This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Herynk, M. H. Articles by Fuqua, S. A. W. Search for Related Content PubMed PubMed Citation Articles by Herynk, M. H. Articles by Fuqua, S. A. W.

Estrogen Receptor Mutations in Human Disease

Breast Center, Baylor College of Medicine, Houston, Texas 77030

Correspondence: Address all correspondence and requests for reprints to: Suzanne A. W. Fuqua, Ph.D., Breast Center, Baylor College of Medicine, One Baylor Plaza, Mailstop 600, Houston, Texas 77030. E-mail: suzannef{at}breastcenter.tmc.edu

	Abstract

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
As early as the 1800s, the actions of estrogen have been implicated in the development and progression of breast cancer. The estrogen receptor (ER) was identified in the late 1950s and purified a few years later. However, it was not until the 1980s that the first ER was molecularly cloned, and in the mid 1990s, a second ER was cloned. These two related receptors are now called ER and ERß, respectively. Since their discovery, much research has focused on identifying alterations within the coding sequence of these receptors in clinical samples. As a result, a large number of naturally occurring splice variants of both ER and ERß have been identified in normal epithelium and diseased or cancerous tissues. In contrast, only a few point mutations have been identified in human patient samples from a variety of disease states, including breast cancer, endometrial cancer, and psychiatric diseases. To elucidate the mechanism of action for these variant isoforms or mutant receptors, experimental mutagenesis has been used to analyze the function of distinct amino acid residues in the ERs. This review will focus on ER and ERß alterations in breast cancer.

I. Introduction

II. ER Structure

III. Roles of ER and ERß

IV. ERs in Human Breast Cancer

V. Splicing and Genetic Alterations of ER

A. Alternative exons in the 5'UTR

B. mRNA splice variants

C. ER experimental splice variants

D. mRNA splice variants summary

E. Natural mutations of ER identified in human tissue samples

F. Natural mutations conclusions

G. Experimental mutations

H. ER experimental mutations summary

VI. Splicing and Genetic Alterations of ERß

A. Alternative exons in the 5'UTR

B. Natural mRNA splice variants

C. mRNA splice variants summary

D. Natural point mutations identified in human tissue samples

E. Experimental point mutations

F. ERß summary

VII. Discussion

	I. Introduction

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
ABERRANT ESTROGENIC SIGNALING has long been associated with human disease such as schizophrenia, Parkinson’s [reviewed by Cyr et al. (1)], osteoporosis [reviewed by Gennari et al. (2) and Grumbach (3)], cancers of the breast [reviewed by Russo and Russo (4)], the colon [reviewed by Di Leo et al. (5)], and ovarian tissues (6). It has long been appreciated that estrogenic signaling plays a critical role in the development of breast cancer (7, 8, 9, 10). As early as the late 1800s, it was recognized that oophorectomy of premenopausal women with metastatic breast cancer caused tumor regression in approximately one third of these patients (9, 10). In the 1950s, Jensen and Jacobson (11, 12) used tritium-labeled, 17ß-estradiol to demonstrate that estradiol was specifically retained by estrogen target tissues. The specific tissue targeting of radiolabeled estradiol led them to hypothesize that a receptor must exist for this molecule. In the next decade, an estrogen receptor (ER) was identified by Toft and Gorski (13) and isolated from several mammalian species, including rat and human (14, 15, 16). However, it was not until the mid 1980s that the first ER, now called ER, was cloned by two groups of investigators (17, 18, 19, 20). In the mid 1990s, a second ER, called ERß, was identified in a library scan of rat (21) and subsequently cloned from several species including the mouse, human, and fish (21, 22, 23). At first, a human ERß with 477 amino acids was reported (23). A few months later, Enmark et al. (24) reported the identification of an ERß mRNA species with a size of 485 amino acids, and it was hypothesized to reflect full-length ERß. The following year, Ogawa et al. (25) reported the cloning of an additional ERß species consisting of 530 amino acids, which is now considered to represent full-length ERß. A few months later, Moore et al. (26) also identified the same 530-amino acid sequence as the full-length ERß, as well as various isoforms. As has been extensively shown for ER, ERß expression has also been associated with cancers of the breast (27, 28, 29, 30), colon (31, 32), and ovarian tissues (6, 33). Additionally, studies with ER and ERß knockout (KO) mice have revealed a role for ER signaling in bone formation, male and female sexual maturation, fertility, cardiovascular and angiogenesis effects, and behavior (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57). These effects of ER and ERß KOs are completely reviewed by Couse and Korach (58) and will not be covered here. Other topics, such as the role of the two ERs in human disease (59, 60, 61), ER structure and function (62), ER interaction with other cellular signaling molecules (63, 64), ER coregulators (62, 65, 66), and the pharmacology of selective estrogen receptor modulators (SERMs) (67, 68), are also extensively reviewed elsewhere, and hence will only be modestly reviewed here for the purpose of background information. This review will instead focus on the genetic alterations that have been identified in the human ERs, including sequence mutations and RNA splice variants.

	II. ER Structure

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
ER and ERß are separate genes, and do not represent splice variants. Accordingly, ER is found on chromosome 6q, whereas ERß is localized to chromosome 14q (24, 69, 70). To fully understand the consequences of specific ER mutations or variants, one must first be familiar with the functional domains of the two ERs. Figure 1 shows the six structural domains (termed domains A–F) of ER (71), and Fig. 2 presents the ERß structural domains as defined by Ogawa et al. (25). There is a predicted 96% homology in the DNA binding domain (C), and a 53% homology between the E/F domains, but the A, B, and hinge (D) domains are not well conserved between ER and ERß as reported by Ogawa et al. (25). In addition to their structural domains, the ERs contain defined functional domains. The transactivation domain termed activation function (AF)-1 is contained within the amino-terminal A and B domains and contains ligand-independent activation function (72, 73, 74, 75). In addition, the A/B region contains a coregulatory domain, which binds various ER coactivators and corepressors that modulate ER-mediated transcriptional activity. The C domain is composed of two zinc finger motifs and encodes the DNA binding domain that is responsible for binding to specific estrogen response elements (EREs) within the promoters of estrogen-responsive genes (72, 76, 77). The ER dimerization domain is discontinuous, is split between the C and E domains, and is required for the ERs to dimerize, allowing binding to the entire ERE site (72). The structural D domain contains the hinge region, part of the ligand-dependent, transactivation domain AF-2a and a portion of the ER nuclear localization signal (78, 79). The carboxy-terminal E and F regions contain the ligand binding domain and the ligand-dependent AF-2 transactivation domain (78). Finally, as previously mentioned, this carboxy-terminal region is also involved in receptor dimerization, the binding of coregulatory proteins, and the binding of chaperone proteins, such as heat shock proteins 70 and 90 (80, 81).

View larger version (15K): [in this window] [in a new window]   FIG. 1. Domains of ER. A, The mRNA sequence of ER. Alternative promoters are shown to the left of +1. The shaded box shows the ER coding region. Exons are numbered in the corresponding blocked region with the nucleotide number above. ATG start codon and the TAG stop codon are shown below. B, The protein domains are labeled A–F, nucleotide numbers corresponding to the start of each domain are above, with amino acid numbers below. Relative positions of some of the known functional domains are represented by solid bars below. BD, Binding domain.

View larger version (12K): [in this window] [in a new window]   FIG. 2. Domains of ERß. A, The mRNA sequence of ERß. Alternative promoters are shown to the left of +1. The shaded box shows the ERß coding region. Exons are numbered in the corresponding blocked region with the nucleotide number above. ATG start codon and the TAG stop codon are shown below. B, The protein domains are labeled A–F, nucleotide numbers corresponding to the start of each domain are above, with amino acid numbers below. Relative positions of some functional domains are represented by solid bars below.

The ligand-independent AF-1 domain can be activated by cAMP, dopamine, vanadate, and growth factors such as epidermal growth factor (EGF) and IGF (77, 101, 102, 103, 104, 105, 106). The AF-1 domain demonstrates ligand-independent activation that is closely related to its phosphorylation status (102, 105, 107). The A/B region also contains a coregulator binding domain, where coactivators such as p68 and steroid receptor coactivator (SRC)-1 and corepressors such as Ssn3 bind and modulate ER-mediated transcriptional activity (108, 109, 110, 111, 112). AF-2 and AF-2a demonstrate ligand-dependent activity (72, 73, 77, 78, 113). AF-2 also contains coregulator binding sites for the coactivators SRC-1, -2, -3 and CREB binding protein (CBP), as well as the corepressors thyroid hormone receptor interacting protein (TRIP1) and repressor of estrogen activity (REA), to name only a few (108, 110, 114, 115, 116, 117, 118, 119, 120). Mutations in these AF-1 and AF-2 functional domains can alter ER signaling by activating or inactivating the protein or by altering the binding of coregulator proteins and, indirectly, modulating ER signaling.

The crystal structure of ER, ERß, and several other nuclear receptors bound to agonists has demonstrated that ligand binding to the carboxy-terminal hydrophobic pocket induces helix 12 to position itself over the pocket (121, 122, 123, 124, 125). This repositioning stabilizes helix 12, allowing it to recruit transcriptional coactivators required for full agonist action (126, 127). When ER is bound to partial agonists or antagonists such as tamoxifen, Faslodex, or raloxifene, the "bulky" side chain of the compound prevents helix 12 from adopting the agonist bound position over the pocket, thus antagonizing coactivator binding to the ERs (124, 128, 129, 130, 131, 132). Compounds without bulky side chains, such as genestein or THC (5,11-cis-diethyl-5,6,11,12-tetrahydrochrysene-2,8-diol) inhibit full ER activation by stabilizing nonproductive conformations of the ligand-binding pocket (128, 129). The mechanism of tamoxifen-mediated repression has been well studied and has demonstrated that tamoxifen-bound ER can recruit corepressors such as nuclear receptor corepressor (NCoR) and silencing mediator of retinoid and thyroid receptor (SMRT) (133, 134, 135, 136, 137, 138). In contrast, ERß has been shown to recruit these corepressors in the presence of agonists, but not antagonists (139). Furthermore, reduced expression of NCoR and SMRT has been correlated with tamoxifen resistance in breast tumors (134, 135, 136, 138, 140), demonstrating the importance of putative helix 12 mutations. This review will focus on ER mutations that lead to alterations within the protein sequence, particularly those that alter AF-1 or AF-2 function. The many ER mRNA splice variants that have been identified, which predict variant forms of the ER proteins, will also be discussed.

	III. Roles of ER and ERß

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
With the relatively recent discovery of ERß, the separate cellular roles for ER and ERß are just now being elucidated. ER and ERß have been demonstrated to form heterodimers, as well as homodimers, further complicating their individual and/or combined function within a cell. Although both receptors bind estrogen with similar affinities, ERß appears to have a stronger affinity for phytoestrogens (141, 142, 143). ERß also exhibits reduced transactivation in most cells when directly compared with ER, and this is likely due to the weaker AF-1 activity of ERß (144, 145, 146). In contrast, AF-2 activity is similar for both ER and ERß, depending on the cell-type (147, 148). These receptors display differential ligand-induced activity; therefore, it is predicted that they could also differentially regulate transactivation of heterologous promoters (149). Paech et al. (149) have shown that estrogens up-regulate ER activating protein (AP)-1 activity, whereas ERß AP-1 activity is reduced. In contrast, the antiestrogens tamoxifen, raloxifene, and ICI 164,384 all increase AP-1 activity of both ER and ERß. Furthermore, serotonin-1A has been shown to be specifically up-regulated through nuclear factor-B (NF-B) induced by ER signaling, but not ERß, demonstrating receptor gene specificity (150). When MDA-MB-231 cells were engineered to overexpress either ER or ERß, both ER and ERß decreased in vitro invasion (151); however, ER-overexpressing cells reduced proliferation in a ligand-dependent manner, whereas ERß was able to repress proliferation in a ligand-independent manner, thus demonstrating divergent roles for these receptors. Although ER and ERß share similar ligand specificities and some signaling actions, they appear to respond to ligands in a receptor-specific manner.

Work with ER KO mice has demonstrated that these receptors are not dependent on or under the control of each other, because mice deficient in one receptor are not lacking in the other (152, 153, 154, 155, 156). Mammary glands of ER KO mice have normal embryonic and fetal development, but these glands never develop beyond the newborn stage (41). In contrast, mammary glands of ERß KO mice develop normally with ductal structures that fill the fatpad but exhibit reduced side branching in nulliparous glands (37, 157), thus demonstrating that ER is the predominant receptor involved in mammary gland development. It should be noted that, in a number of studies, ER KO mice, although lacking the full-length ER, express shorter isoforms of ER mRNA and protein with some residual signaling activity (38, 158, 159). Examination of mammary glands from pregnant and lactating ERß KO mice has revealed that ERß expression is required for normal lobuloalveolar development (157). Additionally, analysis of tight junction proteins, gap junction proteins, smooth muscle actin, and Ki67 expression all suggested that ERß KO mice have less well-differentiated mammary glands compared with wild-type mice (157). Because ER KO mice do not develop normal adult mammary glands, it will be necessary to develop conditional KOs to more adequately model human breast cancer development and progression and to fully delineate hormone action during development.

Because ER KO mice have significantly impaired mammary gland development, it is perhaps not surprising that these mice would be resistant to 7,12-dimethyl benz[a]anthracene (DMBA)-induced mammary tumors (160). Interestingly, when mice lacking ER expression were crossed with transgenic mice overexpressing the mouse mammary tumor virus-Wnt-1 oncogene or the mouse mammary tumor virus-Her2/neu oncogene, mammary tumors did indeed develop (161, 162); however, tumor development was delayed when compared with mice expressing wild-type receptor (161, 162). Collectively, these data demonstrate that although ER can contribute to mammary tumorigenesis, it is not absolutely required.

	IV. ERs in Human Breast Cancer

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
ER signaling is known to be necessary for the proper development and maturation of the mammary gland by stimulating DNA synthesis and promoting bud formation (163, 164, 165, 166). It is estimated that only 7–10% of the epithelial cells in the normal human breast express ER, and it has been shown that this expression fluctuates with the menstrual cycle (167, 168, 169, 170, 171, 172, 173). Although only a small percentage of the cells in the normal breast express ER, these are not the same cells as those that are proliferating (174, 175, 176). In contrast, ERß expression is relatively high in the normal breast, with 80–85% of the cells expressing ERß, which is again inversely correlated with cellular proliferation (59, 177). In contrast, ERß expression does not appear to change during the menstrual cycle (178, 179, 180). Although ER signaling is required for normal mammary gland development, it has been hypothesized that aberrant signaling could lead to abnormal cellular proliferation and survival, potentially participating in the development and progression of breast cancer. Similar to invasive breast cancer, low-grade ductal carcinoma in situ (DCIS) has been demonstrated to have 75% of the cells expressing high levels of ER, but high-grade DCIS has approximately 30% of the cells expressing low levels of ER (181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193). Additionally, it has been shown that DCIS lesions have reduced ERß expression compared with normal epithelium, with high-grade DCIS showing the most significant reduction in ERß levels (177, 178). Although reduced, invasive breast carcinomas show high levels of ER and ERß with approximately two thirds of the tumors staining positive by immunohistochemistry (28, 180, 194, 195, 196). To date, few large studies have been performed analyzing ERß protein expression in normal breast, early lesions, and invasive cancers. Two recent studies, although having varying cutoffs, have demonstrated reduced intralesional ERß expression in DCIS when compared with normal epithelium (197, 198). Additionally, these studies demonstrated a further loss of ERß expression from DCIS to invasive cancer. One study demonstrated a 21% reduction in tumors expressing ERß (194), whereas a second study demonstrated a reduction in intralesional ERß expression and not a reduced number of invasive breast cancers expressing ERß (198). Interestingly, when primary tumors and matched lymph node metastases where compared, there was not a significant reduction in lymph node metastases staining positive for ERß expression (197). Although it has been much hypothesized that ERß has tumor-suppressor-like activity in the breast (199), ERß would have to be unique among tumor suppressors if expressed in over 75% of invasive lesions (178). Undeniably, much more work is required to understand this paradox. Collectively, these data indicate that although ERß levels may vary, ER expression levels rise during tumor progression.

The potential role of ERß in breast cancer progression is highly controversial. Many studies have suggested that ERß expression is a favorable prognostic indicator, whereas additional studies have suggested that ERß expression is associated with known factors of poor clinical outcome. Basically, two types of prognostic studies have been performed to date, those evaluating RNA levels, and those evaluating protein expression. It is interesting to note that many of the studies indicating that ERß is a poor prognostic indicator have evaluated only the RNA levels by quantitative or semiquantitative PCR techniques. Many of these RNA-based studies have correlated ERß expression with markers of a poor prognosis, such as EGF receptor expression and high tumor grade, and an inverse correlation between ERß expression and progesterone receptor (PR) status (28, 30, 200, 201). However, a few studies evaluating RNA have demonstrated that ERß expression is reduced in breast cancer compared with normal epithelium, and that it is inversely correlated with proliferation (evaluated by measuring Ki67 levels) (177, 202), thereby suggesting that ERß expression is a favorable prognostic indicator. However, PCR analysis of RNA levels from tumor samples will also measure ERß mRNA in the "normal" surrounding cells, stroma, and contaminating immune cells present in homogenized tissues. Additionally, many PCR primers may also amplify alternatively spliced RNA variants, thereby increasing the false-positive rate or perhaps skewing results toward higher expression levels. Thus, protein analyses would more precisely measure ERß expression levels in clinical samples.

Studies evaluating ERß protein expression appear to be much less contradictory. Direct protein analyses generally suggest that ERß protein expression is a favorable prognostic indicator, correlating with known biomarkers such as low histological grade, ER and PR expression, longer disease-free survival, and response to tamoxifen (180, 195, 196, 197, 203, 204, 205). Although these studies do not always agree on the specific associations with known prognostic indicators, they do generally agree that similar to ER, ERß expression is a favorable prognostic indicator. A few protein-based studies have suggested that ERß expression is associated with high proliferation (Ki67 expression) and high tumor grade (206, 207). However, these studies have varying cut-off points for being classified as ERß-positive, requiring 20–25% of the cells staining positive for ERß. Furthermore, these later studies examined small tumor subsets. Mann et al. (205), have demonstrated that tumors with as little as 10% of the cells expressing ERß have a more favorable response to tamoxifen, thus suggesting that only 10% positive cells may be a reasonable cut-off point for classification of ERß status in tumors, as has been adopted for ER and tamoxifen responses (208). However, these methods give an estimate of the percentage of positive cells, but they do not account for expression levels in individual cells. The Allred score, used in several studies, measures both the percentage positive and the relative intensity, thus providing a semiquantitative method of ER protein expression (209). It is clear that the role of ERß in breast carcinogenesis has not been fully elucidated; however, direct protein analysis strongly suggests that ERß is an indicator of a more favorable clinical outcome. A uniformly adopted classification of ERß expression will be required to reconcile these issues and may help to clarify the potential role of ERß in breast cancer progression.

It has also been suggested that it is not necessarily the individual level of ER or ERß that is clinically relevant, but the ratio of ER:ERß that may change and impact tumorigenesis. In support of this hypothesis, it has been shown that ER-positive breast cancer has a mean higher ER:ERß ratio when compared with the normal tissue; in contrast, estrogen-independent, ER-negative cancer exhibits a low ER:ERß ratio (201, 210). Further complicating this hypothesis, however, is the existence of ER and ERß splice variants that may contribute to measurements and result in an overestimation of mRNA or protein expression. It is evident that the interplay between ER and ERß could be complicated; data exist that both may have roles within normal breast epithelial cells and that up-regulation or down-regulation of one receptor could potentially upset a physiological balance. Thus, although a definitive role for ERß in breast carcinogenesis has not yet been demonstrated, it can be concluded that ER appears to play the dominant role in the breast.

	V. Splicing and Genetic Alterations of ER

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
A. Alternative exons in the 5'UTR
The majority of efforts to understand ER action have focused on its functional domains and protein-protein interactions. Over the past several years, many investigators have separately identified and named as many as eight upstream untranslated ER exons (69, 211, 212, 213, 214, 215, 216). Because these exons have been identified and differently named, this review will use the nomenclature suggested by Flouriot et al. (216), as modified by Kos et al. (217) and shown in Fig. 1A. ER exon 1, as defined by Green et al. (18), contains an acceptor splice site at +163, permitting the splicing of several different exons encoding various 5' untranslated regions (UTRs). To date, at least seven different promoters have been described, allowing for a relative amount of tissue specificity [for a complete review, see Kos et al. (217)]. The most common promoter found expressed in tissues and cell lines is encoded in exon 1 and is termed promoter A. What is now called promoter C was first described in 1991 (214), and a longer version of promoter C was described a couple of years later (212, 214). In subsequent years, exons A–E were described. These various upstream exons have been shown to affect reporter gene expression levels (218). Numerous AUG start codons are found in these various 5'UTRs and are thought to inhibit the scanning ribosomes from reaching the start codon responsible for full-length ER translation, thus reducing ER protein expression (218). The tissue specificity of these various 5'UTR promoters has been examined (216, 219). It was found that the promoters within 2-kb pairs of the acceptor splice site, namely promoters A, B, and C, are predominately used in cell lines and tissues expressing relatively high levels of ER, whereas the more distal promoters, named E and F, are found in tissues where ER is less abundant, such as the liver and osteoblasts (219). Although these promoters demonstrate some tissue-specific expression, Brand et al. (211) have reported the identification of two new exons, called T1 and T2, that are expressed predominantly in the testis and the epididymis. Because these different promoters can indeed control tissue-specific expression, as well as ER levels, the inappropriate splicing of these promoters may affect the expression and ER signaling activities.

B. mRNA splice variants
ER splice variants have been detected in a number of different normal tissues, including the breast, endometrium, and pituitary tissues, as well as smooth muscle cells and peripheral blood mononuclear cells (220, 221, 222, 223, 224). Additionally, ER mRNA splice variants have been detected in various tumor types including breast cancer, endometrial carcinoma, prolactinoma, systemic lupus erythematosus, and meningiomas, to name a few (see Table 1 and references therein). In the vast majority of cases, wild-type ER is coexpressed along with variant ER mRNAs (225, 226, 227). Although many of these variants have been predominately detected in diseased tissues, a number of studies have been unable to demonstrate differences in the expression levels, or individual patterns of mRNA splice variants when comparing normal controls from unaffected patients to diseased tissues, suggesting that these variants may also play a role in normal physiological processes (220, 221). A large number of splice variants have been reported; therefore, only the most common RNA splice variants will be discussed herein. Unfortunately, the study of predicted proteins of these RNA variants is rare, but we will include a discussion of protein isoforms when appropriate.

View this table: [in this window] [in a new window]   TABLE 1. ER splice variants

1. ER exon 2 deletion (2).

The 2 variant has been detected in a number of tissues. It is interesting to note that in diseases such as breast cancer and systemic lupus erythematosus, where this variant has been identified in both the normal and diseased tissue, no associations were found between relative expression and the particular disease state (221, 231). Additionally, 2 has also been identified in normal endometrium, but not in hyperplastic endometrium or endometrial adenocarcinoma (232, 233). However, this ER variant was not found in the normal pituitary but has been identified in prolactinoma, a tumor arising from the pituitary (222). These data suggest that the exon 2 deleted ER splice variant may be regulated in a tissue-specific manner, but probably does not play a significant role in tumorigenesis.

2. ER exon 3 deletion (3).
The ER 3 splice variant results in an in-frame shift that is missing part of the DNA binding domain. This deletion results in a protein with dominant-negative activity that is able to suppress estrogen-induced transcriptional activity (228, 234). Because this variant is unable to bind DNA, its ability to act as a dominant-negative isoform most likely occurs through dimerization with wild-type ER (228). Stable transfection of ER 3 into the ER-positive MCF-7 breast cancer cell line resulted in an 80% reduction in invasion using a chick embryo chorioallantoic membrane assay (235). Treatment of these 3-expressing cells with estrogen also reduced soft-agar colony-forming ability to below basal levels (235). Because 3 is able to inhibit estrogen-induced transcriptional activity, its expression could potentially affect ER signaling.

The 3 variant has been detected in prolactinoma, endometrial hyperplasia, and breast cancer (222, 225, 233). Comparison of the ER 3:wild-type ER ratios demonstrated that normal breast tissues have a median ratio of 3.4, whereas breast cancers, due to 3 down-regulation, have a median ratio of 0.11 (235). Additionally, 3 has been detected in the majority of ER-positive, PR-negative breast tumors (225), suggesting a role in the discordant receptor phenotype. 3 was not detected in normal pituitary, normal endometrium, or endometrial carcinoma (222, 233). This variant was also found in 19 of 21 endometrial hyperplasias but was not detected in 29 endometrial carcinomas (233). The dominant negative activity of 3 may serve to reduce normal estrogenic signaling, thereby influencing tumor progression and growth. It is interesting to note the tissue-type manner in which this variant has been found. Although prolactinomas and endometrial hyperplasias expressed 3, endometrial carcinomas did not; and furthermore, normal breast tissues have significantly reduced levels, prompting the question does 3 have contrasting roles in alternatively promoting or protecting from tumorigenesis in a tissue-type dependent manner? In addition, ER 3 expression is reduced by over 30-fold in breast cancer when compared with normal breast epithelium; and because ER 3 has dominant negative activity [requiring significantly higher levels of 3 for dominant negative activity (236)], the loss of ER 3 may "relieve" normal physiological repression of ER signaling. To our knowledge, no antibodies specific for 3 exist to test this hypothesis.

3. ER exon 4 deletion (4).
Deletion of ER exon 4 results in an in-frame deletion that encodes a protein lacking a nuclear localization signal, the AF-2a activation domain, and part of the hormone binding domain. The resulting variant isoform is unable to bind hormone or DNA, and therefore has no basal or estrogen-induced transcriptional activity (237). Additionally, this alternately spliced ER isoform does not appear to interfere with wild-type ER activity (237). Although these data suggest that expression of this variant would be of no significant consequence to a cell, its RNA expression has been associated with biomarkers of a more favorable clinical outcome for breast cancer, such as low grade and high PR levels (225, 238). In addition, 4 RNA is more common in PR-positive breast cancer (225, 238). When endometrial hyperplasia and adenocarcinomas were examined for the presence ER 4, it was found in 17 of 21 hyperplasias but was absent in 29 adenocarcinoma samples (233). It is not understood how 4 expression could associate with markers of a more favorable clinical outcome for breast cancer; because it has no appreciable binding or transcriptional activity, larger studies will be required to demonstrate that 4 expression is indeed significantly associated with a more favorable clinical outcome for either breast or endometrial carcinoma?

4. ER exon 5 deletion (5).
We first identified the ER exon 5 deletion isoform that results in the introduction of a stop codon within the ligand binding domain (239). Although the resulting 40-kDa protein lacks most of the ligand binding domain, it retains AF-1 activity and DNA binding ability (239). The 5 retains its ligand-independent transactivation domain AF-1; therefore, it is not surprising that the encoded protein is constitutively active in a yeast transactivation assay or transfected into some breast cancer cell lines (239, 240, 241), although not all cell lines (242). Many studies have attempted to correlate expression of the 5 splice variant with tamoxifen resistance in clinical samples. One study by Madsen et al. (230) found similar levels of 5 mRNA in both tamoxifen-resistant and tamoxifen-sensitive MCF-7 cells. In support of this in vitro result, two separate studies reported by Daffada et al. (243) and Zhang et al. (225) examined 120 and 109 primary breast tumors, respectively, and did not find any correlation between 5 mRNA expression levels and the tamoxifen-resistant phenotype (225, 243). In contrast, several in vitro studies in our laboratory have shown that overexpression of ER 5 in MCF-7 cells confers relative tamoxifen resistance (240, 244). In these studies, we used exogenously expressed 5 in MCF-7 cells, whereas the studies by Madsen et al. looked for levels of this splice variant in acquired tamoxifen-resistant cells. These data suggest that although 5 is able to confer tamoxifen resistance in vitro, it is probably not a major mechanism of de novo or acquired tamoxifen resistance in invasive breast cancer.

ER 5 was first identified in a small number of ER-negative, but PR-positive breast cancers, and these tumors tend to have higher expression levels of 5 (239, 245) relative to wild-type ER. In addition to primary breast cancer, 5 has also been found in normal breast tissue, and is expressed at increased levels in breast cancer metastases (225, 231, 246, 247). Interestingly, this variant has not been found in breast hyperplasias but has been found at reduced levels in normal tissue adjacent to breast cancer (231, 240, 248). Regardless of these correlative findings, 5 levels have not associated with known clinical prognostic indicators such as ER or PR status, tumor size, or S-phase fraction (225). Thus, although expression of ER 5 mRNA is elevated in breast cancers compared with normal tissues, collectively, these data do not support a dominant role for ER 5 in breast tumorigenesis, and convincing evidence for protein expression in patient samples has not been presented.

In addition to breast cancer, other tumor types exhibit expression of 5; pituitary tumors, but not normal pituitary, express 5 (222). In addition, this is the only ER splice variant whose expression has been detected at a significantly increased level in endometrial carcinomas, compared with endometrial hyperplasias (233). Peripheral blood mononuclear cells in patients with systemic lupus erythematosus also express either wild-type ER or the 5 variant, but not both isoforms (249, 250). Thus, at present one can conclude that although 5 does not appear to play a significant role in breast tumorigenesis, there may be an as yet undefined role for 5 in other tumor types.

5. ER exon 6 deletion (6).
There have been few reports of an ER exon 6 deletion variant. Poola and Speirs (251), using RT-PCR assays, first found this variant in one of 35 normal breast samples, but in seven of 38 clinical breast cancer specimens. Using this same technique, 6 has been detected in several ER-positive breast cancer cell lines, including MCF-7 and T47D (252) (see Table 1 for a complete listing). The exon 6 region encodes a portion of the hormone binding and dimerization domains, and it has been demonstrated using experimental mutagenesis (see Table 3) that many important functional amino acids reside within this exon. Although this region is rarely deleted, it is commonly duplicated (Table 1), and three naturally occurring mutations lie within this exon (Table 2). These data are suggestive of an important role for exon 6 in ER signaling, and may help to explain why this particular exon is rarely deleted in vivo.

View this table: [in this window] [in a new window]   TABLE 3. Experimental mutations in ER

View this table: [in this window] [in a new window]   TABLE 2. ER point mutations found in patients

6. ER exon 7 deletion (7).

7. Multiple exon deletions.
In addition to single exon deletions, a number of multiple and partial exon deletions have been found in different normal and neoplastic tissues (Table 1). Although normal breast tissue expresses primarily single exon deletion variants, breast cancer tissues appear to express a number of multiexon splice variants, (251), but their clinical significance remains to be fully discovered. One study by Leygue et al. (238) demonstrated that deletions in exons 2–4 or exons 3–7 are associated with high-grade breast cancers and elevated ER expression. In addition, many of these multiple ER splice variants do not appear to affect the transactivation function of wild-type ER (257). Thus, although a large number of multiple exon splice variants have been identified to date, their role, if any, in breast cancer remains unclear.

8. ER insertion and exon duplications.
In contrast to the lack of single exon 6 deletion variants, a number of the ER variants with multiple exon duplications or multi base-pair insertions involve exon 6; 7.5% of breast cancers examined (n = 212) demonstrate a duplication of exon 6 (226). This duplication results in a truncation immediately after the duplicated exon, leading to a 50-kDa protein that lacks the AF-2 and dimerization domains (226). A duplication of both exons 6 and 7 results in an 80-kDa protein that has lost the ability to bind ligands, such as estrogen or tamoxifen (258, 259, 260, 261). This duplication was originally identified in an estrogen-independent MCF-7 subline and is the result of a genomic rearrangement, rather than alternative RNA splicing (258). A 69-nucleotide insertion between exons 5 and 6 has also been identified in three of 212 breast cancer tumor specimens analyzed (226). This 69-nucleotide insertion results from a point mutation in the intron creating a consensus splice donor site (262). Because a consensus splice acceptor site is located 5' to the 69-nucleotide sequence, this short intron sequence is recognized as an exon (262). Karnik et al. (263) examined tamoxifen-resistant breast cancers for mutations and identified a 42-bp insertion within exon 6. As with the other major ER splice variants, the individual importance of ER exon 6 remains unclear, because it is rarely deleted and is a common site for duplications, suggesting that exon 6 may play an important role in the general function of ER.

C. ER experimental splice variants
The human ER (HE) series of experimental splice variants are widely used both as experimental variants and as backbone plasmids for additional mutational analysis. Originally, 14 deletion and/or truncation mutants were made and called HE1–HE14, and they helped to identify the functional domains of ER (264). In subsequent years, many additional variants with single or multiple deletions and N-terminal and C-terminal truncations have been made; however, these are too numerous to mention, so they will not be discussed here (73, 75, 81, 265). Figure 3 shows the deleted portions of the ER protein in the original HE series mutants (264). HE5–HE9 mutants were unable to bind estradiol, indicating that the hormone binding domain was within amino acids 301–552 (264). Deletions that altered domain C (HE3, HE4, or HE11) or domain D (HE12) reduced nuclear association and ERE binding (81, 264). These original mutants as well as the continued series of deletions and truncations have been valuable tools in mapping the functional domains of ER.

View larger version (22K): [in this window] [in a new window]   FIG. 3. Experimental deletion mutants. The original HE series of experimental deletion mutants as published by Kumar et al. (264 ) is shown. The relative positions of the deleted regions are shown by a break in the horizontal solid black bars. The deleted amino acids are shown in the far right column, with the mutants name in the far left column. The vertical black lines correspond to the A–F domains of ER.

Compared with the number of mRNA splice variants, relatively few variant protein isoforms have been examined, in part, due to the lack of antibodies with the ability to detect specific deleted exons. Although PCR and sequencing can determine the ER exact deletion and/or insertion, antibodies reacting with a different size band only give the relative size and the epitope, but not the isoform identity. A number of groups have compared amino-terminal, carboxy-terminal, and exon-specific antibodies in immunohistochemical studies. These studies have demonstrated that the pattern of immunohistochemical staining is not always identical for antibodies reacting with different epitopes (266, 267). Typically, the amino-terminal signal was found to be stronger than the carboxy-terminal signal, suggesting the presence of truncated variants of ER in clinical samples (266, 268). Western blot analysis of tumor samples has demonstrated a number of different ER isoforms, corresponding to the predicted protein sizes of specific molecular weight forms of mRNA splice variants (245, 246, 269). For instance, Desai et al. (246) developed an ER 5-specific antibody and demonstrated a positive correlation between ER 5 expression and disease-free survival in breast cancer patients. Thus, whereas the number of detected alternatively spliced ER mRNAs is large, the number of variant isoforms that appear to be stably translated in vivo is infrequent.

In vitro analysis of ER variant isoforms has demonstrated a range of activities, including constitutive activation and dominant negative phenotypes. Theoretically, a small amount of a constitutively active isoform could significantly up-regulate total ER activity. In contrast, numerous studies have demonstrated that significantly higher amounts of dominant negative receptor are required to obtain significant inhibition of wild-type ER signaling. For instance, dose-dependent inhibition of ER transactivation has been demonstrated with a number of different dominant negative constructs, including ER 3 and ER 7 as well as ERß 5 (236, 254, 270). Erenburg et al. (235), using transient transfection assays, demonstrated that 10 times more ER 3 is required to obtain an 80% inhibition of estrogen-induced ER transactivation in HeLa cells. MCF-7 cells stably expressing ER 3 at varying levels showed a dose-dependent reduction in pS2 mRNA, with the greatest reduction in cells expressing higher levels of variant than wild-type protein. These in vitro studies support the concept that significantly higher amounts of dominant negative ER, compared with wild-type receptor, are required to inhibit ER function. Because it has been shown that relatively few tumors demonstrate variant expression levels higher than wild-type ER (225), thus is the expression of variant ER isoforms really playing a significant role in this small subset of tumors? Although 10 times more DNA was required to reduce transactivation in transient transfection assays, stable transfection and expression of similar or even slightly less ER 3 did significantly reduce anchorage-dependent growth, soft-agar colony-forming ability, and in vitro invasion of MCF-7 breast cancer cells (235). This later result could suggest that although low level dominant negative inhibition may not dramatically affect transactivation, it may significantly impair the ability of a cell to survive and grow, at least in vitro.

E. Natural mutations of ER identified in human tissue samples
Several groups have reported single mutations within the ER sequence, however many of these are silent mutations or polymorphisms that do not affect the protein sequence. Some of the identified mutations do result in an altered ER protein sequence and have been detected in a variety of tissues and diseases, including breast cancer and its metastases, endometrial cancer, and physiological disorders (Table 2). Only those ER mutations that have been identified in breast cancers will be discussed here.

Although two thirds of all breast cancers express ER, mutations within the ER sequence are relatively rare. One study found that mutations occur in only 1% of primary tumors (271). It has been suggested that the mutation frequency may be higher in metastatic breast tumors, and some of these have been correlated with tamoxifen resistance and estrogen independence (263, 272). For instance, recent studies have demonstrated increased mutation rates in metastatic breast lesions (272). We have identified a somatic mutation at nucleotide 908 of ER in 34% of hyperplastic breast tissues (273). This later study used newer, more sensitive detection techniques, which, due to the heterogeneity of tumors, may be required to accurately detect ER mutations to determine realistic mutation rates. Although the rates of mutations are low in the primary tumor and increased in metastases, many of the single mutations identified to date have been demonstrated to influence breast cancer cell behavior.

1. Mutations that do not affect ER functionality.
Some of the ER point mutations do not demonstrate any observable phenotype different from that of wild-type ER. For instance, ER S47T and K531E mutations identified from metastatic breast cancer specimens were analyzed for their ability to transactivate four different ERE reporter constructs in HeLa and MDA-MB-231 breast cancer cells (272). The transactivation profiles of these two mutants did not differ from the transactivation status of the wild-type ER. Roodi et al. (271) have also identified two single mutations from an individual patient with a breast cancer metastasis. These two mutations, ER N69K in the AF-1 transactivation domain and ER M396V in the ligand binding domain, were identified from a tumor that was clinically ER-negative (271). A missense mutation in the ER D domain was identified as a leucine to proline substitution at amino acid 296 (274). An ER E352V mutation was also identified in a breast cancer patient who responded to adjuvant tamoxifen therapy (263). Although these later mutations do not observably alter ER functionality, many mutations have been identified that do dramatically affect the regulation of wild-type ER and will be discussed next.

2. ER A86V.
One of the first naturally occurring missense mutations identified in breast cancer specimens was ER A86V (275, 276). This mutation was found to be present in a subset of patients originally identified with a silent mutation at nucleotide 261 (275). This combination of a silent mutation and a missense mutation has been found to be associated with several distinct phenotypes. First, women expressing this variant allele are significantly taller (277), and ER-positive breast cancer patients have an elevated risk of spontaneous abortions if this double mutation is present (278). Additionally, ER-positive breast tumors expressing this allele tend to have lower levels of ER protein when compared with tumors expressing wild-type ER (275). These data all demonstrate that a single mutation in ER can have profound biological effects. It will prove useful when these studies are expanded to larger patient populations.

Because ER-positive tumors expressing this variant allele demonstrated reduced ER protein levels, Schmutzler et al. (279) hypothesized that it may be one mechanism leading to ER-negative tumors. To test this hypothesis, they examined genomic DNA, but found an approximately equal distribution of this variant allele (279). In total, of the tissue samples from 483 women that were analyzed, 59 were found to carry this variant allele (279). Additionally, blood samples from healthy women expressed the variant allele 9.5% (279) of the time. Interestingly, all carriers were heterozygous, suggesting that homozygous expression of this variant allele may not be viable. However, through power calculations, these authors determined that at least 960 samples would have to be tested to determine whether indeed the A86V homozygous cell is not viable.

3. ER K303R.
Our group has identified a K303R somatic mutation at the border of the hinge and hormone binding domains of ER in 34% of hyperplastic breast lesions (273). Additionally, we have detected this same mutation in the majority of primary breast cancers (our unpublished results). In contrast to our findings in samples from the United States, Zhang et al. (280) were unable to find this mutation in a cohort of breast cancer samples from Japanese women. The reason for this ethnic difference is currently under investigation. Because this mutation is present only in tumor samples, and not in normal tissues, it may have an important role in tumor progression.

To examine a potential role for this mutation in tumor progression, MCF-7 cells with enforced expression of K303R ER were analyzed. Both the wild-type and the K303R ER mutant receptors have similar binding affinities for estrogen and tamoxifen (273). Although these receptors have similar binding affinities, cells expressing the mutant receptor responded to 10^–12 M estrogen as well as they responded to 10^–9 M estrogen in an in vitro growth assay. MCF-7 cells expressing the wild-type receptor had a doubling time of 2.2 d and 1.3 d when grown in 10^–12 and 10^–9 M estrogen, respectively (273). In contrast, cells expressing the mutant receptor had a doubling time of 1.3 d, regardless of whether the cells were grown in 10^–12 or 10^–9 M estrogen (273). Because the estrogen binding affinities were identical, the binding of the ER coactivator transcriptional intermediary factor 2 (TIF2) was analyzed. In vitro binding experiments revealed increased ER association with transcriptional intermediary factor 2 at low levels of hormone, suggesting one potential mechanism for the observed increased sensitivity to estrogen (273). We hypothesize that the K303R ER mutation reduces the concentration of hormone required for the formation of the coactivator:ER hydrophobic groove binding surface (131, 273). Lysine at amino acid 303 has also been identified as a major acetylation site within ER (281). ER acetylation was shown to modulate the response to ligand and may, in part, be a component of the mechanism leading to the increased estrogen hypersensitivity associated with this mutant receptor (281). These data demonstrate that the K303R ER mutation has acquired the ability to respond to much lower concentrations of estrogen, e.g., a gain of function mutation. Because the hypersensitive mutation has been found in a large percentage of primary tumor samples, we are currently examining its clinical role as a prognostic biomarker.

4. ER 437Stop
The 437Stop mutation results from the deletion of a nucleotide in codon 432 leading to a frameshift and the introduction of a stop codon at residue 437 (263). This mutation was first identified in a patient that had relapsed while on tamoxifen (263). Interestingly, this mutation was found only in the metastatic lesion and not in the primary tumor, suggesting a role in tamoxifen resistance and/or metastatic spread (263). Furthermore, Graham et al. (282) have identified an ER 417Stop mutation in the tamoxifen-resistant T47D_CO cell line. These two mutants suggest that loss of the ligand binding domain could be one mechanism, albeit infrequently, of acquired tamoxifen resistance. However, there have been no reports of these truncated proteins in vivo in tamoxifen-treated patients.

5. ER Y537N/Y537S.
Before identifying Y537 as a site of natural mutation in breast cancer, much work had already been done with mutations at this site, demonstrating that this tyrosine is an important phosphorylation site with potential roles in regulating ligand binding, homodimerization, and transactivation of ER. These experiments, as well as additional Y537 experimental mutations are discussed in Section V.G. dealing with experimental mutations. Because of this earlier work, it was very exciting when Kohler et al. (283) identified a Y537S mutation in endometrial cancer and we found the Y537N mutation in an ER-negative metastatic breast cancer patient (272). Because many publications have analyzed the Y537S mutation in conjunction with other Y537 mutants, the in vitro analysis of the Y537S mutation will be further discussed in Section V.G. dealing with experimental mutations. Transactivation analysis of the Y537N mutation was analyzed in both HeLa and MDA-MB-231 breast cancer cells utilizing four different ER-responsive promoter constructs: vitellogenin, pS2, cathepsin D, and lactoferrin (272). It was demonstrated that, in the absence of estrogen, the Y537N mutant exhibited 5- to 20-fold higher levels of transactivation (vs. wild-type ER). Because this tyrosine residue is an important ER phosphorylation site, a mutation at this site may allow ER to escape phosphorylation-mediated controls (272, 284, 285, 286) and provide a cell with a potential selective tumorigenic advantage. Because only a relatively few metastatic tumors have been examined for mutations at Y537, its frequency may be underappreciated.

6. ER silent mutations.
In addition to the numerous nonsense and missense mutations that have been found in ER, several silent mutations have also been identified. These mutations do not alter the protein sequence, so they would not be predicted to significantly affect ER function. In fact, the majority of polymorphisms identified do not have an observable phenotype associated with them, regardless of the tissue of origin (263, 271, 287). Although the ER codon 10 polymorphism has been found in numerous normal and diseased tissues, it is not commonly associated with the diseased state (221, 283, 288, 289). However, two other silent mutations, one in codon 87 and one in codon 325, have been reported to be associated with distinct phenotypes. The BstU1 restriction fragment length polymorphism (RFLP) is caused by a silent mutation in codon 87 (275). This mutation was subsequently found to be linked with the A86V missense mutation, and it is associated with spontaneous abortions and reduced ER levels in breast cancer patients with ER-positive tumors, as discussed above. Multiple studies have demonstrated a correlation between a silent mutation at codon 325 and breast cancer risk (271, 290, 291). Additionally, this mutation has been associated with low femoral neck bone mineral density (BMD), but not lumbar spine BMD (292). Unfortunately, all of the correlative studies have involved a small number of patients. Although these silent mutations do not directly affect the protein sequence, they may indirectly affect protein function through alterations in RNA turnover rates, such as RNA half-life, and/or protein translation, hence indirectly altering total ER protein levels. Thus, the exact mechanism of how these silent mutations affect ER protein function and their clinical significance remains to be elucidated.

F. Natural mutations conclusions
Mutations within ER have been found in a number of different diseases, and it is interesting to note that many of these mutations were identified in breast cancer patients that were clinically classified as ER-negative. The ligand binding assay is the most common technique for determining tumor ER status and might not be efficient in detecting ERs with an altered ligand binding capacity or reduced protein levels; antibodies used for immunohistochemical studies may also suffer from these same limitations. Additional functional analysis of the mutations identified in patients will help to determine whether they indeed play a role in breast cancer progression and/or resistance to therapeutic treatment, or just represent errors without functional clinical meaning.

G. Experimental mutations
Many laboratories have used experimental mutagenesis techniques to identify the important functional amino acids in ER. Mutations have been introduced into the human ER cDNA, resulting in well over 100 point mutations along the amino acid sequence of human ER (outlined in Table 3). Many of these were made and screened for activating mutations, and thus a large number do not affect the protein function analyzed in the corresponding references. Although many of these mutations are listed as "no change" in function, this is not intended to imply that other, as yet unanalyzed, functions of these mutant ERs will not be altered. Several of these mutations have been extensively studied and reveal important aspects of ER structure-function relationships, and they will be discussed in more detail. In addition to the single point mutations discussed in this paper, a number of proteins containing double and triple point mutations have been made and will be discussed briefly herein. Double and triple mutations within the DNA-binding domain generally demonstrated lost or reduced transactivation induced by estrogen and tamoxifen (293, 294, 295, 296). In contrast, replacing the lysines at amino acids 302 and 303, within the hinge region, with arginine, glutamine, or alanine resulted in increased estrogen-induced transactivation (281). A number of studies have reported double and triple mutations within the ligand-binding domain of ER and generally result in decreased estrogen binding affinity and reduced estrogen induced transactivation (297, 298, 299, 300, 301, 302, 303). Additionally, mutations within the ligand binding domain have also been shown to eliminate or reduce the agonist activity of tamoxifen and raloxifene (77, 124, 294, 304, 305). Although a detailed discussion of ER containing double and triple point mutations would undoubtedly be interesting and informative, it is beyond the scope of this paper.

1. ER serine 118.
Because of the location of serine 118 within the ER ligand-independent transactivation AF-1 domain, many groups have sought to determine the effects of phosphorylation at serine 118 on ER-induced transcriptional activation. S118 is a major ER phosphorylation site that can be induced by estrogens, antiestrogens such as tamoxifen, and growth factors such as the EGF and IGF (105, 106, 306, 307, 308, 309). Experiments using pharmacological inhibitors have demonstrated that phosphorylation of S118 is dependent upon signaling through the Ras-MAPK pathway (105, 106, 306). Furthermore, Chen et al. (309) have demonstrated that the MAPKs ERK1/2 phosphorylate S118 in an estrogen-independent manner. Additionally, cyclin-dependent kinase (CDK)7, but not cyclin A-CDK2, has been shown to phosphorylate S118 in a ligand-dependent manner (309, 310). A number of different growth factors have been demonstrated to induce phosphorylation of S118, and many of these factors are known to be involved in proliferation, cell-cycle regulation, and survival.

Mutational analysis has demonstrated that S118 is required for the complete transcriptional activity of ER (105, 106, 308, 311, 312). Although mutation of serine 118 to alanine resulted in reduced transactivation, no change in estrogen binding affinity or ERE binding affinity was found (312). EGF-induced transactivation of ER is dependent on S118, but phosphorylation of S118 is not sufficient for transactivation (105). Furthermore, Karas et al. (306) examined differences in ER signaling in human saphenous vein smooth muscle cells, pulmonary vein endothelial cells (PVECs) and COS-1 cells, and found that although MAPK-induced phosphorylation of S118 activates ER transcription in nonvascular cells, mutation of S118 did not affect ER transactivation in PVECs. Additionally, S118A altered ER phosphorylation patterns in COS-1 and Sf9 cells but not HeLa cells, indicating some cell-type-specific effects on ER posttranslational phosphorylation (312). Collectively, these data suggest an important role for S118 phosphorylation in ER transactivation; however, ER S118 may also function in a cell-type-specific manner.

The role of S118 in nuclear localization of ER has been examined, and mutations at this site demonstrate this residue to be important for estrogen-independent nuclear localization of ER (313). In contrast, this residue has not been shown to be involved in estrogen-stimulated nuclear localization (313). Additionally, constitutive activation of MAPK signaling results in the nuclear localization of ER, suggesting that phosphorylation of S118 is important for growth factor-mediated nuclear localization of ER (313).

2. ER aspartate 351.
A naturally occurring mutation in the ligand binding domain was discovered in the tamoxifen-resistant MCF7/MT2 xenografted tumor line (314, 315). Of note, the D351Y mutation was the primary form of ER identified in this particular tumor (314, 315). Although this mutation was identified in only one of four tamoxifen-resistant xenografted tumor lines and has yet to be reported in human breast tumors, it has been the subject of much research and has revealed details about ER structure-function relationships. The conversion of aspartate to tyrosine or glutamate results in a receptor that exhibits an estrogenic response to many antiestrogens, including raloxifene, EM652, GW7604, keoxifene, and tamoxifen (305, 316, 317, 318, 319, 320, 321, 322, 323, 324). Interestingly, the effects of the pure antiestrogen Faslodex (ICI 182,780) are unaffected by mutating this site to tyrosine (319, 322, 323). Experimental mutagenesis of D351 to glycine, valine, or phenylalanine does not result in a receptor that responds to antiestrogens in an agonistic manner, demonstrating that only specific mutations result in activity inversion mutants (298, 321, 325). These in vitro studies, combined with x-ray crystallography studies, have shown that D351 is critical for the interaction with the antiestrogenic side chains of SERMs (124, 131, 316, 320). Liu et al. (316) tested whether the SERM side chain neutralizes the negative charge of aspartate, or whether "shielding" the negative charge is the mechanism responsible for the activity inversion mutants. Through the use of various mutants and R1/h (a raloxifene derivative unable to neutralize the negative charge of aspartate), Liu et al. demonstrated that the raloxifene side chain both shields and neutralizes the negative charge at D351 (316). The estrogenic response of the D351Y mutant to antiestrogens requires the AF-1 domain because mutants with a deleted AF-1 domain lose the ability to increase ER transactivation in response to the antiestrogens tamoxifen and raloxifene (305, 326). Although the AF-2 domain is not required, D351Y mutants possessing intact AF-1 and AF-2 domains produce a synergistic estrogenic response to antiestrogens (305, 326). Furthermore, the ER D351Y mutant shows reduced interactions with the corepressors NCoR and SMRT (324). Collectively, these data demonstrate an important role for D351 in the ER response elicited by SERMs.

3. ER glycine 400.
A glycine residue at amino acid 400 also lies within the ligand binding domain of ER. However, in contrast to D351Y, mutation of G400 does not result in a receptor that exhibits an agonistic response to keoxifene (320, 327). However, G400V has been demonstrated to convert tamoxifen from a partial agonist into a full agonist (328). Upon examination of binding affinity, it was found that the G400V mutant has 10- to 100-fold lower affinity for both estrogen and antiestrogens (327, 329). However, estrogen, albeit at higher concentrations, was able to activate both the wild-type and the mutant receptors to similar levels (330). Collectively, these data demonstrate that the G400 mutation alters ligand binding affinity, but not ER-induced transcriptional activity.

Although wild-type ER demonstrates low levels of ERE DNA binding in the absence of estrogen, the G400V mutant is devoid of ERE binding and transactivation in the absence of estrogen (325, 331). Metzger et al. (332) studied the effects of heat on the ability of ER to bind on the ERE. It was found that although heat inactivated binding of both wild-type ER and the G400V mutant ER, the ERE binding capacity of the mutant was reduced more quickly compared with wild-type ER (332). This effect was independent of estrogen, tamoxifen, or ICI 164,384 (332). Analysis of the ability of dopamine to activate ER demonstrated that dopamine induced transcriptional activity only in wild-type ER, and not of the G400 mutated ER. Additionally, dopamine in combination with estrogen induced a synergistic increase in transcriptional activity in the mutated ER, whereas the wild-type ER only demonstrated an additive increase in transcriptional activity (330), thus suggesting a cooperative mechanism of ER activation. These data also demonstrate that mutation of glycine at amino acid 400 within the ligand binding domain results in an ER with a reduced affinity for estrogen leading to reduced ERE binding and transactivation.

4. ER cysteine 530.
Amino acid residues 515–535 have been suggested to play a critical role in ligand binding (333). The cysteine at position 530 has received considerable attention and study. Although C530A has been the most commonly made in vitro mutation, Neff et al. (334) have identified C530P, C530G, and C530W as the most informative mutations at this site. Despite having an unchanged estrogen binding affinity, these mutations were shown to have reduced estrogen-mediated transcription as well as ERE binding activity (334). In contrast, the C530A mutant showed similar estrogen and ERE binding affinities and estrogen-induced transcription (334, 335, 336). Additionally, C530A did not result in differential effects of hexesterol, P1496, or tamoxifen (337). Because estrogen and tamoxifen bind in a noncovalent, reversible manner, the important role of this cysteine is most notably seen when covalently binding ligands are used. C530 has been identified as a covalent attachment site for 17--(haloacetamidoalkyl) estradiols, 11ß-[(aziridinylalkoxy)phenyl]estradiols, kenostrol aziridine, and tamoxifen aziridine (335, 338, 339). Mutation of this cysteine did not alter binding of reversible ligands but showed a 10-fold reduction in kenostrol aziridine and tamoxifen aziridine binding (335). Furthermore, the covalently attaching 11ß-[(aziridinylalkoxy)phenyl]estradiol did not affect the ability of estrogen to bind in the ER containing the C530A mutation (338). These data suggest that C530 is a critical residue for covalently attaching ligands; thus, new antiestrogenic therapeutic strategies targeting this residue may hold future promise for the treatment of breast cancer.

C530 lies outside the nuclear localization signal, and consequently, it would not be expected to impact nuclear localization; however, Neff et al. (334) have also demonstrated that C530 may play a role in nuclear translocation. Two mutants, C530S and C530P, demonstrated high levels of cytoplasmic ER in the absence of estrogen, whereas stimulation with estrogen results in nuclear translocation of these two mutant receptors (337). The wild-type receptor, along with eight other mutants, demonstrated primarily nuclear localization, regardless of the presence or absence of estrogen (337). These data suggest that specific mutations outside the nuclear localization signal can still significantly affect the subcellular localization of the ER.

5. ER tyrosine 537.
Because tyrosine 537 to asparagine was identified as a naturally occurring, constitutively active mutation (272), Y537 has been an informative site for in vitro mutation analysis. In addition to ER Y537N, alanine and serine also result in a constitutively active receptor (115, 325, 340). Estrogen binding affinities were measured for several of the mutants, with phenylalanine and serine demonstrating similar binding affinities as wild-type ER, but a glutamic acid substitution exhibited a 10-fold reduction in estrogen binding affinity (341). Interestingly, all of these mutated receptors retain the ability to respond to antiestrogens by inhibiting both basal and estrogen-induced ER transcriptional activity (115, 342). When the crystal structure was solved, Y537 was found to be the amino-cap residue of helix 12 (343). Helix 12 has been shown to stabilize ligand binding and to be important for creating the agonist bound conformation allowing ER to actively recruit coactivators (124, 125). Y537 and the amino-cap of helix 12 thus play important roles in the activation and regulation of ER signaling.

A number of studies have demonstrated that tyrosine 537, the major tyrosine phosphorylation site in ER (344), also plays a critical role in the dimerization and DNA binding of ER. Treatment of wild-type ER with the tyrosine-specific phosphatase, protein tyrosine phosphatase 1B (PTP1B), significantly reduced the ability of ER to dimerize and bind DNA in a dose-dependent manner (345). This reduced ability of dephosphorylated ER to dimerize and bind DNA could be restored by pretreating ER with the c-Src family kinases pp60c-src or p56lck (286, 345). Additionally, dimerization of wild-type ER can be blocked by the addition of free phosphotyrosine or a phosphotyrosyl peptide, indicating that the dimerization domain of one ER binds to the phosphorylated tyrosine of an adjacent receptor (285). Furthermore, using a bivalent antihuman ER antibody, inactive (e.g., unphosphorylated) ER monomers can be induced to dimerize and bind to DNA (345). These data would suggest that phosphorylation of Y537 is critical to ER activation; however, more recent studies have demonstrated that phosphorylation of Y537 is not required for hormone binding or transactivation (344). Y537 forms a hydrogen bond with N348 upon ligand binding, and this newly formed hydrogen bond stabilizes helix 12 in the "closed" pocket formation (340). Mutation of Y537 to phenylalanine, but not serine or glutamic acid, abolishes this hydrogen bond (124, 131, 341). This "lost" hydrogen bond correlates with monophasic estrogen dissociation kinetics, suggesting an inability of ER to dimerize (341, 346). In contrast, wild-type ER and Y537S or Y537E demonstrate biphasic dissociation kinetics (341). Yudt et al. (346) have suggested that the monophasic dissociation kinetics are due to the lost hydrogen bond allowing an open or loose pocket conformation, regardless of the presence or absence of ligand, rather than an inhibition of ER dimerization. Although Y537 undoubtedly plays a critical role in ER activation, its exact mechanism of action remains unclear.

6. ER leucine 540.
Mutation of leucine to glutamine at amino acid 540 has been generated by chemical mutagenesis (347). This mutation exhibits reduced basal transcriptional activity and has lost the ability to respond to estrogen, although it can bind estrogen with normal affinity (298, 347, 348). Similar to the mutations described at amino acid 351, L540Q has increased transcriptional activity in response to many antiestrogens, including ICI 164,384, RU54876, and tamoxifen (348, 349). More importantly, L540Q can act as a dominant-negative receptor by inhibiting the activity of wild-type receptor by as much as 75% (347). This dominant-negative receptor has been used to reduce established ER-positive T47D xenografted tumors when animals were treated with adenovirus containing the L540Q mutant ER (350). Furthermore, expression of L540Q resulted in increased levels of Bax protein and elevated p38 MAPK phosphorylation leading to cellular apoptosis (350). It has been hypothesized that L540 may play a role in regulating ER ligand recognition or transcriptional activation.

L540Q can inhibit wild-type ER through a dominant-negative manner; thus, multiple groups have sought to determine the exact ER regions important for this dominant-negative effect. Montano et al. (348) have demonstrated that the ER A/B domain is important for the estrogenic response of the L540Q mutant to antiestrogens. Additionally, deleting the A/B domain in the L540Q mutant resulted in a receptor that no longer acts as a dominant-negative; these double mutants still retain the ability to dimerize with wild-type ER but are unable to inhibit its activity (349, 351). The introduction of a dimerization-deficient mutation (L507R) into this dominant-negative receptor abrogates the ability of the L540Q mutation to inhibit wild-type ER (351). These data support the hypothesis that the dominant negative effect of L540Q involves the AF-1 transactivation domain and that dimerization of the mutant to wild-type receptor is critical for this effect.

H. ER experimental mutations summary
The ability to target specific regions of ER by site-directed mutational analysis has allowed researchers to tease apart the various mechanisms of ER action, including ligand interactions, transactivational requirements, and numerous corepressor and coactivator interactions. Future studies such as these will undoubtedly aid in developing ER-specific therapies for the treatment of human breast cancer.

	VI. Splicing and Genetic Alterations of ERß

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
A. Alternative exons in the 5'UTR
Although many alternatively spliced exons have been described in the 5' UTR of ER, only two have been described for ERß. Exons ON and OK have been demonstrated to regulate ERß gene expression (352). Whereas exon ON is found in a wide range of tissues including the spermatozoa, uterine endometrium, uterine myometrium, and peripheral leukocytes, exon OK is predominantly found in spermatozoa (352). It is interesting to note that the sequence of exon OK was found to be identical to the 5' UTR of ERßcx, which can function as a dominant-negative receptor for ER, to be discussed in the next section (352, 353). These data suggest that exon OK may play a role in more than just tissue-specific expression of ERß or may directly affect signaling of both ER and ERß.

B. Natural mRNA splice variants
By far, the vast majority of identified alterations within the ERß sequence are differentially spliced variants (Table 4). As with ER splice variants, ERß splice variants have been found in a number of different normal and diseased tissues. ERß was identified much later than ER, hence much less is known with respect to its splice variants, sequence mutations, and the protein functions of these isoforms. Although significantly fewer ERß splice variants have been identified to date, their number is growing rapidly.

2. ERß exon 2 deletion (2).
Deletion of exon 2 has been found to be the most common ERß splice site, and it is frequently associated with deletion of exons 5 or 6 (358). The loss of exon 2 results in a premature termination codon leading to a predicted carboxy-truncated protein (358). Although this is the most common splice variant, no significant differences in expression between breast cancer or matched normal breast from a distant site have been reported (359). Thus, preliminary data suggest that the exon 2 splice variant may not play a significant role in breast tumorigenesis, which may limit its impact, if any, in breast cancer.

3. ERß exon 3 deletion (3).
The 3 variant, originally identified in normal ovarian tissue, does not result in a disruption of the ERß open reading frame (358). However, exon 3 does encode the second zinc finger in the DNA binding domain (358), and this zinc finger has been demonstrated to be required for ERß cross-talk with Stat5b (360). Although this mutation has not been identified in breast cancer, it may play a role in differential interactions with other transcription factors and is worthy of future study.

4. ERß exon 4 deletion (4).
Similar to 3, loss of only ERß exon 4 does not result in a disruption of the open reading frame (358). However, this splice variant does lack the nuclear localization signal and appears to be localized to the cytoplasmic spaces (358). Although 4 has been identified in breast cancer, no significant differences have been observed between normal breast and breast cancer (359). The role of 4 in breast tumorigenesis is currently unknown.

5. ERß exon 5 deletion (5).
Because much work has been done analyzing the role of the ER 5 isoform, it is not surprising that ERß 5 is one of the most studied ERß splice variants. This variant also lacks part of the hormone binding domain (358, 361). The resulting protein is properly localized to the nucleus, and does not have any differential effects on basal activation of ERß (270). However, 5 acts as a dominant-negative receptor for estrogen-induced transactivation of both ER and ERß in a dose-dependent manner (270, 355). Ten-fold more ERß 5 was required to inhibit 80% of the estrogen-induced activity of ER or ERß (270). It has been suggested that expression of 5 could impair the normal functions of both ERs, potentially contributing to the genesis of estrogen-independent breast cancer.

ERß 5 has been found in a number of different tissues including ovary, uterus, normal breast, and breast cancer (358, 362). One study found 5 in normal breast, but not in breast cancer (358). However, a later study by the same group found elevated levels of the 5 variant to be associated with high tumor grade and postmenopausal status; grade 3 breast cancer expressed higher levels of ERß 5, whereas grade 2 tumors exhibited reduced expression when compared with matched normal breast (359). Interestingly, this variant was also found in the ER-negative breast cancer cell line, MDA-MB-231 (361). ERß 5 has the potential to play a role in breast tumorigenesis, but additional studies with larger numbers of clinical samples examining 5 at the protein level are needed to ascertain a definitive role.

6. ERß exon 6 deletion (6).
In contrast to ER, the ERß exon 6 is commonly deleted and results in a truncated translation product (358). Although this variant was found at slightly lower levels in breast cancer compared with normal breast, the differences were not statistically significant (359). This difference was also not correlated with histological type, grade, ER or PR status, menopause, or nodal status (359). Therefore, although the ERß exon 6 is commonly deleted in the breast, it does not appear to play a significant role in breast tumorigenesis.

7. ERß exon 7 deletion (7).
ER 7 is the most frequently observed variant in human breast cancer; however, deletion of exon 7 is relatively rare in ERß. Two separate studies have failed to detect ERß splice variants containing a deletion of this exon (358, 359). The lack of ERß 7 variant expression is similar to ER 6 expression, suggesting that both exon 6 in ER and exon 7 in ERß may play vital roles in ER function.

C. mRNA splice variants summary
ERß was discovered more than three decades after ER, and therefore much less is known about its functional interactions. The recent identification of multiple ERß splice variants may help to elucidate the role of ERß and its variants in breast cancer. It is interesting to note that 6 is a rare splice variant in ER, whereas ERß 6 is fairly common. Additionally, ER 7 is a fairly common-occurring splice variant, but deletion of exon 7 in ERß is virtually nonexistent. Exons 6 and 7 in both ER and ERß encode portions of the ligand binding domain and the AF-2 transactivation domain. Why exon 6 in ER and exon 7 in ERß are infrequently spliced remains to be elucidated. These two exons may be important for the stabilization of ER mRNAs; their deletion may lead to degradation and may be associated with our inability to find these deletion variants. These data suggest an as yet unknown important role for this region in ER function. Deletion of exon 5 in both ER and ERß has proven to be common and potentially clinically relevant, but in contrasting ways. ER 5 is a constitutively active receptor, whereas ERß 5 can act as a dominant-negative isoform of both ER and ERß. ER expression is a good prognostic indicator for clinical outcome; thus, a naturally occurring dominant-negative ERß could suppress the beneficial effects of ER expression, thereby indirectly contributing to tumor progression. Additionally, alternatively spliced variants have been shown to lead to important effects on ER function, such as differential interactions with transcription factors and altered nuclear localization.

D. Natural point mutations identified in human tissue samples
Although numerous splice variants of ERß have been identified, relatively few point mutations have been reported. A G250S mutation was identified in obese male children, and this same study identified several silent mutations in both underweight and obese children (363). These include the base-pair changes, 1082G to A, 1421G to C, and 1730G to A, but these polymorphisms were not associated with any of the phenotypes analyzed (363). ER has been associated with BMD; thus, there have been searches for ERß mutations also in postmenopausal women with osteoporosis (364). A silent mutation in codon 328G to A was identified and demonstrated to lead to an RsaI RFLP (364). This RFLP was then used to screen a larger cohort of patients to demonstrate that the silent mutation at codon 328 was not significantly associated with BMD (364). In summary, the number of point mutations identified within the ERß sequence is few, and thus, their clinical relevance remains to be discovered.

E. Experimental point mutations
Analysis of ERß function through the use of experimental mutations has been very limited to date. One study by Bjornstrom and Sjoberg (360) made several single and double point mutations in the zinc finger domain of ERß to identify key residues involved in DNA binding and transactivation, and these mutations abrogated ERß-induced reporter activity. These mutations include R207A/K208A, E167A/G168A, C201A/C204A, C149A/C152A, and A187T (360). Interestingly, S200E also abrogated ERß transactivation, but the S200A mutation had no effect on transactivation (360). In addition, L206A, R207A/K208A, Y210A, and P186T mutations exhibited little effect on the activity of ERß (360). Furthermore, analysis of ERß cross-talk with Stat5b or AP-1 indicated that disruption of the second zinc finger domain was important for signaling through Stat5b, but the first zinc finger was found to be irrelevant for Stat5b signaling (360). In contrast, AP-1 signaling required both zinc finger structures for ERß-induced AP-1 signaling (360). Furthermore, the DNA binding ability of ERß was found to be inconsequential for estrogen-induced Stat5b or AP-1 activity (360). In contrast to ER, relatively few point mutations in the ERß protein sequence have been discovered or experimentally constructed; thus, we are just beginning to elucidate potential ERß actions in the breast and to find functions that are distinct from ER.

F. ERß summary
To date, ERß point mutations have not provided much insight into the mechanism of action of ERß, because relatively few naturally occurring point mutations have been identified and in vitro mutagenesis experiments with ERß are few. However, as was done with ER, future mutagenesis work will help to unravel the potential functions of ERß signaling in the normal breast and breast cancer.

	VII. Discussion

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 
Due to the normal function of the ERs in mammary gland development, it is not surprising that ER signaling has been implicated in breast cancer progression and metastasis. Many groups have identified naturally occurring mutations and splice variants with constitutive activity, even in the absence of estrogen. Additionally, a naturally occurring ER mutation (K303R) has been identified which leads to a receptor that is able to induce proliferation in low levels of hormone. These alternate receptor forms could lead to uncontrolled proliferation, potentially providing a cell with a growth advantage. Additional mutants act as dominant-negatives and inhibit ER action. Interestingly, a number of these were identified in tamoxifen-resistant or clinically ER-negative tumors. Taken together, these data support dual roles for ER signaling in breast cancer: 1) uncontrolled ER signaling that can lead to increased cellular proliferation, or 2) ER signaling is required for normal growth controls, where a loss of ER signaling can lead to hormone-independence, clinically ER-negative tumors, or a more aggressive phenotype.

In addition to the many splice variants and mutations reported to be expressed in breast cancer, the story may be even further complicated by direct heterodimerization between ER and ERß. It has been suggested that it is not the individual levels of ER or ERß, but the ratio of ER:ERß that may be most important. How might the ratios of ER:ERß be important? ERß usually exhibits weak ligand-independent transactivation; therefore, an ER/ERß heterodimer should theoretically have less ligand-independent (e.g., cAMP, dopamine, and growth factor-induced) transcriptional activity compared with ER/ER homodimers. However, ERß retains normal ligand-dependent transcriptional activity; therefore, ER/ERß heterodimers could be activated by estrogen-dependent mechanisms to similar levels as ER homodimers. Heterodimerization is a potential mechanism whereby the cell could limit the immediate response to nonestrogenic signals and, hence, restrain growth factor signaling through ER. In addition to the ratio of ER:ERß, it has been suggested that splice variants may serve to regulate the pool of mRNA available to produce full-length protein, thereby controlling ER expression levels in a tissue-specific manner (365). These data would imply that, although they do not regulate one another at the genetic level, they may regulate one another at the epigenetic level.

It is interesting to note that although a large number of splice variants have been reported, only a handful of mutations have been identified or studied from human patient samples. Furthermore, most of these single base-pair mutations have little or no observable effect on function. However, there may be multiple "hot spots" for spontaneous ER mutations. For instance, three separate ER mutations have been found in the relatively short hinge region, and one of these mutations, K303R ER, has been found at a relatively high frequency in primary breast cancers (366). The hormone binding domain comprises a large portion of the ER protein; therefore, it is not surprising that many mutations would be found within this region. However, tyrosine 537 is the only amino acid that has been found mutated to two different amino acids. Because these mutations have been identified in breast cancer patient samples, they are the focus of intense research that has yielded valuable insights into potential mechanisms of hormone-independent signaling.

Experimental mutagenesis studies have also yielded significant insight into hormone action in the breast. These studies have determined critical residues for ligand binding, coregulator proteins, DNA binding, dimerization and activation states. These types of in vitro mutagenesis studies will undoubtedly aid in the development of newer, more effective pure antiestrogens. Additionally, it may be possible to modulate the activities of ER and potentially activate the antitumorigenic properties of ER signaling. Because many clinically ER-negative tumors demonstrate expression of ER splice variants and mutations, development of new strategies to identify and therapeutically target these altered receptors may hold significant potential in the treatment of breast cancer.

	Acknowledgments

M.H.H. is supported by National Institutes of Health (NIH)/National Cancer Institute (NCI) Training Program Grant T32 CA90221, and this work was supported in part by NIH/NCI Grant CA58183 (to S.A.W.F.).

	Footnotes

 
Abbreviations: AF, Activation function; AP, activating protein; BMD, bone mineral density; CDK, cyclin-dependent kinase; DCIS, ductal carcinoma in situ; EGF, epidermal growth factor; ER, estrogen receptor; ERE, estrogen response element; HE, human ER; KO, knockout; NCoR, nuclear receptor corepressor; PR, progesterone receptor; RFLP, restriction fragment length polymorphism; SERM, selective estrogen receptor modulator; SMRT, silencing mediator of retinoid and thyroid receptor; SRC, steroid receptor coactivator; UTR, untranslated region.

	References

Top Abstract I. Introduction II. ER Structure III. Roles of ER{alpha}... IV. ERs in Human... V. Splicing and Genetic... VI. Splicing and Genetic... VII. Discussion References

 

1. Cyr M, Calon F, Morissette M, Di Paolo T 2002 Estrogenic modulation of brain activity: implications for schizophrenia and Parkinson’s disease. J Psychiatry Neurosci 27:12–27[Medline]
2. Gennari L, Becherini L, Falchetti A, Masi L, Massart F, Brandi ML 2002 Genetics of osteoporosis: role of steroid hormone receptor gene polymorphisms. J Steroid Biochem Mol Biol 81:1–24[CrossRef][Medline]
3. Grumbach MM 2000 Estrogen, bone, growth and sex: a sea change in conventional wisdom. J Pediatr Endocrinol Metab 13(Suppl 6):1439–1455
4. Russo IH, Russo J 1998 Role of hormones in mammary cancer initiation and progression. J Mammary Gland Biol Neoplasia 3:49–61[CrossRef][Medline]
5. Di Leo A, Messa C, Cavallini A, Linsalata M 2001 Estrogens and colorectal cancer. Curr Drug Targets Immune Endocr Metabol Disord 1:1–12[Medline]
6. Pujol P, Rey JM, Nirde P, Roger P, Gastaldi M, Laffargue F, Rochefort H, Maudelonde T 1998 Differential expression of estrogen receptor- and -ß messenger RNAs as a potential marker of ovarian carcinogenesis. Cancer Res 58:5367–5373[Abstract/Free Full Text]
7. Feigelson HS, Ross RK, Yu MC, Coetzee GA, Reichardt JK, Henderson BE 1996 Genetic susceptibility to cancer from exogenous and endogenous exposures. J Cell Biochem Suppl 25:15–22[Medline]
8. Colditz GA 1998 Relationship between estrogen levels, use of hormone replacement therapy, and breast cancer. J Natl Cancer Inst 90:814–823[Abstract/Free Full Text]
9. Beatson C 1896 On the treatment of inoperable cases of carcinoma of the mamma: suggestions for a new method of treatment, with illustrative cases. Lancet 2:104–107
10. Boyd S 1900 On oophorectomy in cancer of the breast. Br Med J 2:1161–1167[Free Full Text]
11. Jensen E, Jacobson HI 1960 Fate of steroidal estrogens in target tissues. In: Pincus G, Vollmer EP, eds. Biological activities of steroids in relation to cancer. New York: Academic Press; 161–174
12. Jensen E, Jacobson HI 1962 Basic guides to the mechanism of estrogen action. Recent Prog Horm Res 18:387–414
13. Toft D, Gorski J 1966 A receptor molecule for estrogens: isolation from the rat uterus and preliminary characterization. Proc Natl Acad Sci USA 55:1574–1581[Free Full Text]
14. Toft D, Shyamala G, Gorski J 1967 A receptor molecule for estrogens: studies using a cell-free system. Proc Natl Acad Sci USA 57:1740–1743[Free Full Text]
15. Gorski J, Toft D, Shyamala G, Smith D, Notides A 1968 Hormone receptors: studies on the interaction of estrogen with the uterus. Recent Prog Horm Res 24:45–80[Medline]
16. Jensen EV, Suzuki T, Kawashima T, Stumpf WE, Jungblut PW, DeSombre ER 1968 A two-step mechanism for the interaction of estradiol with rat uterus. Proc Natl Acad Sci USA 59:632–638[Free Full Text]
17. Walter P, Green S, Greene G, Krust A, Bornert JM, Jeltsch JM, Staub A, Jensen E, Scrace G, Waterfield M, Chambon P 1985 Cloning of the human estrogen receptor cDNA. Proc Natl Acad Sci USA 82:7889–7893[Abstract/Free Full Text]
18. Green S, Walter P, Kumar V, Krust A, Bornert JM, Argos P, Chambon P 1986 Human oestrogen receptor cDNA: sequence, expression and homology to v-erb-A. Nature 320:134–139[CrossRef][Medline]
19. Greene GL, Gilna P, Waterfield M, Baker A, Hort Y, Shine J 1986 Sequence and expression of human estrogen receptor complementary DNA. Science 231:1150–1154[Abstract/Free Full Text]
20. Green S, Walter P, Greene G, Krust A, Goffin C, Jensen E, Scrace G, Waterfield M, Chambon P 1986 Cloning of the human oestrogen receptor cDNA. J Steroid Biochem 24:77–83[CrossRef][Medline]
21. Kuiper GG, Enmark E, Pelto-Huikko M, Nilsson S, Gustafsson JA 1996 Cloning of a novel receptor expressed in rat prostate and ovary. Proc Natl Acad Sci USA 93:5925–5930[Abstract/Free Full Text]
22. Tremblay GB, Tremblay A, Copeland NG, Gilbert DJ, Jenkins NA, Labrie F, Giguere V 1997 Cloning, chromosomal localization, and functional analysis of the murine estrogen receptor ß. Mol Endocrinol 11:353–365[Abstract/Free Full Text]
23. Mosselman S, Polman J, Dijkema R 1996 ER ß: identification and characterization of a novel human estrogen receptor. FEBS Lett 392:49–53[CrossRef][Medline]
24. Enmark E, Pelto-Huikko M, Grandien K, Lagercrantz S, Lagercrantz J, Fried G, Nordenskjold M, Gustafsson JA 1997 Human estrogen receptor ß-gene structure, chromosomal localization, and expression pattern. J Clin Endocrinol Metab 82:4258–4265[Abstract/Free Full Text]
25. Ogawa S, Inoue S, Watanabe T, Hiroi H, Orimo A, Hosoi T, Ouchi Y, Muramatsu M 1998 The complete primary structure of human estrogen receptor ß (hER ß) and its heterodimerization with ER in vivo and in vitro. Biochem Biophys Res Commun 243:122–126[CrossRef][Medline]
26. Moore JT, McKee DD, Slentz-Kesler K, Moore LB, Jones SA, Horne EL, Su JL, Kliewer SA, Lehmann JM, Willson TM 1998 Cloning and characterization of human estrogen receptor ß isoforms. Biochem Biophys Res Commun 247:75–78[CrossRef][Medline]
27. Speirs V, Malone C, Walton DS, Kerin MJ, Atkin SL 1999 Increased expression of estrogen receptor ß mRNA in tamoxifen-resistant breast cancer patients. Cancer Res 59:5421–5424[Abstract/Free Full Text]
28. Speirs V, Parkes AT, Kerin MJ, Walton DS, Carleton PJ, Fox JN, Atkin SL 1999 Coexpression of estrogen receptor and ß: poor prognostic factors in human breast cancer? Cancer Res 59:525–528[Abstract/Free Full Text]
29. Dotzlaw H, Leygue E, Watson PH, Murphy LC 1997 Expression of estrogen receptor-ß in human breast tumors. J Clin Endocrinol Metab 82:2371–2374[Abstract/Free Full Text]
30. Dotzlaw H, Leygue E, Watson PH, Murphy LC 1999 Estrogen receptor-ß messenger RNA expression in human breast tumor biopsies: relationship to steroid receptor status and regulation by progestins. Cancer Res 59:529–532[Abstract/Free Full Text]
31. Campbell-Thompson M, Lynch IJ, Bhardwaj B 2001 Expression of estrogen receptor (ER) subtypes and ERß isoforms in colon cancer. Cancer Res 61:632–640[Abstract/Free Full Text]
32. Foley EF, Jazaeri AA, Shupnik MA, Jazaeri O, Rice LW 2000 Selective loss of estrogen receptor ß in malignant human colon. Cancer Res 60:245–248[Abstract/Free Full Text]
33. Rutherford T, Brown WD, Sapi E, Aschkenazi S, Munoz A, Mor G 2000 Absence of estrogen receptor-ß expression in metastatic ovarian cancer. Obstet Gynecol 96:417–421[CrossRef][Medline]
34. Lubahn DB, Moyer JS, Golding TS, Couse JF, Korach KS, Smithies O 1993 Alteration of reproductive function but not prenatal sexual development after insertional disruption of the mouse estrogen receptor gene. Proc Natl Acad Sci USA 90:11162–11166[Abstract/Free Full Text]
35. Korach KS 1994 Insights from the study of animals lacking functional estrogen receptor. Science 266:1524–1527[Abstract/Free Full Text]
36. Haynes MP, Russell KS, Bender JR 2000 Molecular mechanisms of estrogen actions on the vasculature. J Nucl Cardiol 7:500–508[CrossRef][Medline]
37. Krege JH, Hodgin JB, Couse JF, Enmark E, Warner M, Mahler JF, Sar M, Korach KS, Gustafsson JA, Smithies O 1998 Generation and reproductive phenotypes of mice lacking estrogen receptor ß. Proc Natl Acad Sci USA 95:15677–15682[Abstract/Free Full Text]
38. Couse JF, Curtis SW, Washburn TF, Lindzey J, Golding TS, Lubahn DB, Smithies O, Korach KS 1995 Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene. Mol Endocrinol 9:1441–1454[Abstract/Free Full Text]
39. Korach KS, Couse JF, Curtis SW, Washburn TF, Lindzey J, Kimbro KS, Eddy EM, Migliaccio S, Snedeker SM, Lubahn DB, Schomberg DW, Smith EP 1996 Estrogen receptor gene disruption: molecular characterization and experimental and clinical phenotypes. Recent Prog Horm Res 51:159–186; discussion 186–188[Medline]
40. Schomberg DW, Couse JF, Mukherjee A, Lubahn DB, Sar M, Mayo KE, Korach KS 1999 Targeted disruption of the estrogen receptor- gene in female mice: characterization of ovarian responses and phenotype in the adult. Endocrinology 140:2733–2744[Abstract/Free Full Text]
41. Bocchinfuso WP, Korach KS 1997 Mammary gland development and tumorigenesis in estrogen receptor knockout mice. J Mammary Gland Biol Neoplasia 2:323–334[CrossRef][Medline]
42. Eddy EM, Washburn TF, Bunch DO, Goulding EH, Gladen BC, Lubahn DB, Korach KS 1996 Targeted disruption of the estrogen receptor gene in male mice causes alteration of spermatogenesis and infertility. Endocrinology 137:4796–4805[Abstract]
43. Hess RA, Bunick D, Lee KH, Bahr J, Taylor JA, Korach KS, Lubahn DB 1997 A role for oestrogens in the male reproductive system. Nature 390:509–512[CrossRef][Medline]
44. Ogawa S, Lubahn DB, Korach KS, Pfaff DW 1997 Behavioral effects of estrogen receptor gene disruption in male mice. Proc Natl Acad Sci USA 94:1476–1481[Abstract/Free Full Text]
45. Ogawa S, Taylor JA, Lubahn DB, Korach KS, Pfaff DW 1996 Reversal of sex roles in genetic female mice by disruption of estrogen receptor gene. Neuroendocrinology 64:467–470[Medline]
46. Ogawa S, Eng V, Taylor J, Lubahn DB, Korach KS, Pfaff DW 1998 Roles of estrogen receptor- gene expression in reproduction-related behaviors in female mice. Endocrinology 139:5070–5081[Abstract/Free Full Text]
47. Ogawa S, Washburn TF, Taylor J, Lubahn DB, Korach KS, Pfaff DW 1998 Modifications of testosterone-dependent behaviors by estrogen receptor- gene disruption in male mice. Endocrinology 139:5058–5069[Abstract/Free Full Text]
48. Rissman EF, Early AH, Taylor JA, Korach KS, Lubahn DB 1997 Estrogen receptors are essential for female sexual receptivity. Endocrinology 138:507–510[Abstract/Free Full Text]
49. Wersinger SR, Sannen K, Villalba C, Lubahn DB, Rissman EF, De Vries GJ 1997 Masculine sexual behavior is disrupted in male and female mice lacking a functional estrogen receptor gene. Horm Behav 32:176–183[CrossRef][Medline]
50. Rubanyi GM, Freay AD, Kauser K, Sukovich D, Burton G, Lubahn DB, Couse JF, Curtis SW, Korach KS 1997 Vascular estrogen receptors and endothelium-derived nitric oxide production in the mouse aorta. Gender difference and effect of estrogen receptor gene disruption. J Clin Invest 99:2429–2437[Medline]
51. Iafrati MD, Karas RH, Aronovitz M, Kim S, Sullivan Jr TR, Lubahn DB, O’Donnell Jr TF, Korach KS, Mendelsohn ME 1997 Estrogen inhibits the vascular injury response in estrogen receptor -deficient mice. Nat Med 3:545–548[CrossRef][Medline]
52. Karas RH, Hodgin JB, Kwoun M, Krege JH, Aronovitz M, Mackey W, Gustafsson JA, Korach KS, Smithies O, Mendelsohn ME 1999 Estrogen inhibits the vascular injury response in estrogen receptor ß-deficient female mice. Proc Natl Acad Sci USA 96:15133–15136[Abstract/Free Full Text]
53. Windahl SH, Andersson G, Gustafsson JA 2002 Elucidation of estrogen receptor function in bone with the use of mouse models. Trends Endocrinol Metab 13:195–200[CrossRef][Medline]
54. Windahl SH, Hollberg K, Vidal O, Gustafsson JA, Ohlsson C, Andersson G 2001 Female estrogen receptor ß –/– mice are partially protected against age-related trabecular bone loss. J Bone Miner Res 16:1388–1398[CrossRef][Medline]
55. Wang L, Andersson S, Warner M, Gustafsson JA 2003 Estrogen receptor (ER) ß knockout mice reveal a role for ERß in migration of cortical neurons in the developing brain. Proc Natl Acad Sci USA 100:703–708[Abstract/Free Full Text]
56. Lindberg MK, Moverare S, Skrtic S, Gao H, Dahlman-Wright K, Gustafsson JA, Ohlsson C 2003 Estrogen receptor (ER)-ß reduces ER-regulated gene transcription, supporting a "ying yang" relationship between ER and ERß in mice. Mol Endocrinol 17:203–208[Abstract/Free Full Text]
57. McCauley LK, Tozum TF, Kozloff KM, Koh-Paige AJ, Chen C, Demashkieh M, Cronovich H, Richard V, Keller ET, Rosol TJ, Goldstein SA 2003 Transgenic models of metabolic bone disease: impact of estrogen receptor deficiency on skeletal metabolism. Connect Tissue Res 44(Suppl 1):250–263
58. Couse JF, Korach KS 1999 Estrogen receptor null mice: what have we learned and where will they lead us? Endocr Rev 20:358–417[Abstract/Free Full Text]
59. Palmieri C, Cheng GJ, Saji S, Zelada-Hedman M, Warri A, Weihua Z, Van Noorden S, Wahlstrom T, Coombes RC, Warner M, Gustafsson JA 2002 Estrogen receptor ß in breast cancer. Endocr Relat Cancer 9:1–13[Abstract]
60. Fuqua SA 2001 The role of estrogen receptors in breast cancer metastasis. J Mammary Gland Biol Neoplasia 6:407–417[CrossRef][Medline]
61. Ali S, Coombes RC 2000 Estrogen receptor in human breast cancer: occurrence and significance. J Mammary Gland Biol Neoplasia 5:271–281[CrossRef][Medline]
62. Sommer S, Fuqua SA 2001 Estrogen receptor and breast cancer. Semin Cancer Biol 11:339–352[CrossRef][Medline]
63. Ho KJ, Liao JK 2002 Nonnuclear actions of estrogen. Arterioscler Thromb Vasc Biol 22:1952–1961[Abstract/Free Full Text]
64. Lannigan DA 2003 Estrogen receptor phosphorylation. Steroids 68:1–9[CrossRef][Medline]
65. Klinge CM 2000 Estrogen receptor interaction with co-activators and co-repressors. Steroids 65:227–251[CrossRef][Medline]
66. Tremblay GB, Giguere V 2002 Coregulators of estrogen receptor action. Crit Rev Eukaryot Gene Expr 12:1–22[CrossRef][Medline]
67. Jordan VC 2003 Antiestrogens and selective estrogen receptor modulators as multifunctional medicines. 2. Clinical considerations and new agents. J Med Chem 46:1081–1111[CrossRef][Medline]
68. Jordan VC 2003 Antiestrogens and selective estrogen receptor modulators as multifunctional medicines. 1. Receptor interactions. J Med Chem 46:883–908[CrossRef][Medline]
69. Ponglikitmongkol M, Green S, Chambon P 1988 Genomic organization of the human oestrogen receptor gene. EMBO J 7:3385–3388[Medline]
70. Gosden JR, Middleton PG, Rout D 1986 Localization of the human oestrogen receptor gene to chromosome 6q24—-q27 by in situ hybridization. Cytogenet Cell Genet 43:218–220[Medline]
71. Green S, Kumar V, Krust A, Walter P, Chambon P 1986 Structural and functional domains of the estrogen receptor. Cold Spring Harb Symp Quant Biol 51(Pt 2):751–758
72. Ribeiro RC, Kushner PJ, Baxter JD 1995 The nuclear hormone receptor gene superfamily. Annu Rev Med 46:443–453[CrossRef][Medline]
73. Kumar V, Green S, Stack G, Berry M, Jin JR, Chambon P 1987 Functional domains of the human estrogen receptor. Cell 51:941–951[CrossRef][Medline]
74. Berry M, Metzger D, Chambon P 1990 Role of the two activating domains of the oestrogen receptor in the cell-type and promoter-context dependent agonistic activity of the anti-oestrogen 4-hydroxytamoxifen. EMBO J 9:2811–2818[Medline]
75. Metzger D, Ali S, Bornert JM, Chambon P 1995 Characterization of the amino-terminal transcriptional activation function of the human estrogen receptor in animal and yeast cells. J Biol Chem 270:9535–9542[Abstract/Free Full Text]
76. Klein-Hitpass L, Ryffel GU, Heitlinger E, Cato AC 1988 A 13 bp palindrome is a functional estrogen responsive element and interacts specifically with estrogen receptor. Nucleic Acids Res 16:647–663[Abstract/Free Full Text]
77. Tzukerman MT, Esty A, Santiso-Mere D, Danielian P, Parker MG, Stein RB, Pike JW, McDonnell DP 1994 Human estrogen receptor transactivational capacity is determined by both cellular and promoter context and mediated by two functionally distinct intramolecular regions. Mol Endocrinol 8:21–30[Abstract/Free Full Text]
78. Norris JD, Fan D, Kerner SA, McDonnell DP 1997 Identification of a third autonomous activation domain within the human estrogen receptor. Mol Endocrinol 11:747–754[Abstract/Free Full Text]
79. Picard D, Kumar V, Chambon P, Yamamoto KR 1990 Signal transduction by steroid hormones: nuclear localization is differentially regulated in estrogen and glucocorticoid receptors. Cell Regul 1:291–299[Medline]
80. Scherrer LC, Picard D, Massa E, Harmon JM, Simons Jr SS, Yamamoto KR, Pratt WB 1993 Evidence that the hormone binding domain of steroid receptors confers hormonal control on chimeric proteins by determining their hormone-regulated binding to heat-shock protein 90. Biochemistry 32:5381–5386[CrossRef][Medline]
81. Chambraud B, Berry M, Redeuilh G, Chambon P, Baulieu EE 1990 Several regions of human estrogen receptor are involved in the formation of receptor-heat shock protein 90 complexes. J Biol Chem 265:20686–20691[Abstract/Free Full Text]
82. Klock G, Strahle U, Schutz G 1987 Oestrogen and glucocorticoid responsive elements are closely related but distinct. Nature 329:734–736[CrossRef][Medline]
83. Driscoll MD, Sathya G, Muyan M, Klinge CM, Hilf R, Bambara RA 1998 Sequence requirements for estrogen receptor binding to estrogen response elements. J Biol Chem 273:29321–29330[Abstract/Free Full Text]
84. Klinge CM, Peale Jr FV, Hilf R, Bambara RA, Zain S 1992 Cooperative estrogen receptor interaction with consensus or variant estrogen responsive elements in vitro. Cancer Res 52:1073–1081[Abstract/Free Full Text]
85. Klinge CM, Knox DT, Bambara RA, Zain S, Hilf R 1989 Antiestrogen(4-hydroxytamoxifen)-charged estrogen receptor binding to nuclei from normal and neoplastic rat mammary tissues is not affected by host hormonal status. J Steroid Biochem 33:335–340[CrossRef][Medline]
86. Klinge CM, Traish AM, Bambara RA, Hilf R 1996 Dissociation of 4-hydroxytamoxifen, but not estradiol or tamoxifen aziridine, from the estrogen receptor as the receptor binds estrogen response element DNA. J Steroid Biochem Mol Biol 57:51–66[CrossRef][Medline]
87. Klinge CM, Traish AM, Driscoll MD, Hilf R, Bambara RA 1996 Site-directed estrogen receptor antibodies stabilize 4-hydroxytamoxifen ligand, but not estradiol, and indicate ligand-specific differences in the recognition of estrogen response element DNA in vitro. Steroids 61:278–289[CrossRef][Medline]
88. Anolik JH, Klinge CM, Bambara RA, Hilf R 1993 Differential impact of flanking sequences on estradiol- vs 4-hydroxytamoxifen-liganded estrogen receptor binding to estrogen responsive element DNA. J Steroid Biochem Mol Biol 46:713–730[CrossRef][Medline]
89. Anolik JH, Klinge CM, Hilf R, Bambara RA 1995 Cooperative binding of estrogen receptor to DNA depends on spacing of binding sites, flanking sequence, and ligand. Biochemistry 34:2511–2520[CrossRef][Medline]
90. Anolik JH, Klinge CM, Brolly CL, Bambara RA, Hilf R 1996 Stability of the ligand-estrogen receptor interaction depends on estrogen response element flanking sequences and cellular factors. J Steroid Biochem Mol Biol 59:413–429[CrossRef][Medline]
91. Nardulli AM, Greene GL, Shapiro DJ 1993 Human estrogen receptor bound to an estrogen response element bends DNA. Mol Endocrinol 7:331–340[Abstract/Free Full Text]
92. Potthoff SJ, Romine LE, Nardulli AM 1996 Effects of wild type and mutant estrogen receptors on DNA flexibility, DNA bending, and transcription activation. Mol Endocrinol 10:1095–1106[Abstract/Free Full Text]
93. Kim J, de Haan G, Nardulli AM, Shapiro DJ 1997 Prebending the estrogen response element destabilizes binding of the estrogen receptor DNA binding domain. Mol Cell Biol 17:3173–3180[Abstract]
94. Nardulli AM, Grobner C, Cotter D 1995 Estrogen receptor-induced DNA bending: orientation of the bend and replacement of an estrogen response element with an intrinsic DNA bending sequence. Mol Endocrinol 9:1064–1076[Abstract/Free Full Text]
95. Nardulli AM, Shapiro DJ 1992 Binding of the estrogen receptor DNA-binding domain to the estrogen response element induces DNA bending. Mol Cell Biol 12:2037–2042[Abstract/Free Full Text]
96. Sabbah M, Le Ricousse S, Redeuilh G, Baulieu EE 1992 Estrogen receptor-induced bending of the Xenopus vitellogenin A2 gene hormone response element. Biochem Biophys Res Commun 185:944–952[CrossRef][Medline]
97. Sadovsky Y, Webb P, Lopez G, Baxter JD, Fitzpatrick PM, Gizang-Ginsberg E, Cavailles V, Parker MG, Kushner PJ 1995 Transcriptional activators differ in their responses to overexpression of TATA-box-binding protein. Mol Cell Biol 15:1554–1563[Abstract]
98. Jacq X, Brou C, Lutz Y, Davidson I, Chambon P, Tora L 1994 Human TAFII30 is present in a distinct TFIID complex and is required for transcriptional activation by the estrogen receptor. Cell 79:107–117[CrossRef][Medline]
99. Wu SY, Thomas MC, Hou SY, Likhite V, Chiang CM 1999 Isolation of mouse TFIID and functional characterization of TBP and TFIID in mediating estrogen receptor and chromatin transcription. J Biol Chem 274:23480–23490[Abstract/Free Full Text]
100. Klein-Hitpass L, Schwerk C, Kahmann S, Vassen L 1998 Targets of activated steroid hormone receptors: basal transcription factors and receptor interacting proteins. J Mol Med 76:490–496[CrossRef][Medline]
101. Chen D, Pace PE, Coombes RC, Ali S 1999 Phosphorylation of human estrogen receptor by protein kinase A regulates dimerization. Mol Cell Biol 19:1002–1015[Abstract/Free Full Text]
102. Aronica SM, Katzenellenbogen BS 1993 Stimulation of estrogen receptor-mediated transcription and alteration in the phosphorylation state of the rat uterine estrogen receptor by estrogen, cyclic adenosine monophosphate, and insulin-like growth factor-I. Mol Endocrinol 7:743–752[Abstract/Free Full Text]
103. Gangolli EA, Conneely OM, O’Malley BW 1997 Neurotransmitters activate the human estrogen receptor in a neuroblastoma cell line. J Steroid Biochem Mol Biol 61:1–9[CrossRef][Medline]
104. Auricchio F, Di Domenico M, Migliaccio A, Castoria G, Bilancio A 1995 The role of estradiol receptor in the proliferative activity of vanadate on MCF-7 cells. Cell Growth Differ 6:105–113[Abstract]
105. Bunone G, Briand PA, Miksicek RJ, Picard D 1996 Activation of the unliganded estrogen receptor by EGF involves the MAP kinase pathway and direct phosphorylation. EMBO J 15:2174–2183[Medline]
106. Kato S, Endoh H, Masuhiro Y, Kitamoto T, Uchiyama S, Sasaki H, Masushige S, Gotoh Y, Nishida E, Kawashima H, Metzger D, Chambon P 1995 Activation of the estrogen receptor through phosphorylation by mitogen-activated protein kinase. Science 270:1491–1494[Abstract/Free Full Text]
107. Weigel NL, Zhang Y 1998 Ligand-independent activation of steroid hormone receptors. J Mol Med 76:469–479[CrossRef][Medline]
108. McDonnell DP, Vegeto E, O’Malley BW 1992 Identification of a negative regulatory function for steroid receptors. Proc Natl Acad Sci USA 89:10563–10567[Abstract/Free Full Text]
109. Ogryzko VV, Schiltz RL, Russanova V, Howard BH, Nakatani Y 1996 The transcriptional coactivators p300 and CBP are histone acetyltransferases. Cell 87:953–959[CrossRef][Medline]
110. Voegel JJ, Heine MJ, Tini M, Vivat V, Chambon P, Gronemeyer H 1998 The coactivator TIF2 contains three nuclear receptor-binding motifs and mediates transactivation through CBP binding-dependent and -independent pathways. EMBO J 17:507–519[CrossRef][Medline]
111. Endoh H, Maruyama K, Masuhiro Y, Kobayashi Y, Goto M, Tai H, Yanagisawa J, Metzger D, Hashimoto S, Kato S 1999 Purification and identification of p68 RNA helicase acting as a transcriptional coactivator specific for the activation function 1 of human estrogen receptor . Mol Cell Biol 19:5363–5372[Abstract/Free Full Text]
112. Onate SA, Tsai SY, Tsai MJ, O’Malley BW 1995 Sequence and characterization of a coactivator for the steroid hormone receptor superfamily. Science 270:1354–1357[Abstract/Free Full Text]
113. Webb P, Nguyen P, Valentine C, Lopez GN, Kwok GR, McInerney E, Katzenellenbogen BS, Enmark E, Gustafsson JA, Nilsson S, Kushner PJ 1999 The estrogen receptor enhances AP-1 activity by two distinct mechanisms with different requirements for receptor transactivation functions. Mol Endocrinol 13:1672–1685[Abstract/Free Full Text]
114. Onate SA, Boonyaratanakornkit V, Spencer TE, Tsai SY, Tsai MJ, Edwards DP, O’Malley BW 1998 The steroid receptor coactivator-1 contains multiple receptor interacting and activation domains that cooperatively enhance the activation function 1 (AF1) and AF2 domains of steroid receptors. J Biol Chem 273:12101–12108[Abstract/Free Full Text]
115. Weis KE, Ekena K, Thomas JA, Lazennec G, Katzenellenbogen BS 1996 Constitutively active human estrogen receptors containing amino acid substitutions for tyrosine 537 in the receptor protein. Mol Endocrinol 10:1388–1398[Abstract/Free Full Text]
116. Anzick SL, Kononen J, Walker RL, Azorsa DO, Tanner MM, Guan XY, Sauter G, Kallioniemi OP, Trent JM, Meltzer PS 1997 AIB1, a steroid receptor coactivator amplified in breast and ovarian cancer. Science 277:965–968[Abstract/Free Full Text]
117. Montano MM, Ekena K, Delage-Mourroux R, Chang W, Martini P, Katzenellenbogen BS 1999 An estrogen receptor-selective coregulator that potentiates the effectiveness of antiestrogens and represses the activity of estrogens. Proc Natl Acad Sci USA 96:6947–6952[Abstract/Free Full Text]
118. Simon SL, Parkes A, Leygue E, Dotzlaw H, Snell L, Troup S, Adeyinka A, Watson PH, Murphy LC 2000 Expression of a repressor of estrogen receptor activity in human breast tumors: relationship to some known prognostic markers. Cancer Res 60:2796–2799[Abstract/Free Full Text]
119. Spencer TE, Jenster G, Burcin MM, Allis CD, Zhou J, Mizzen CA, McKenna NJ, Onate SA, Tsai SY, Tsai MJ, O’Malley BW 1997 Steroid receptor coactivator-1 is a histone acetyltransferase. Nature 389:194–198[CrossRef][Medline]
120. Henttu PM, Kalkhoven E, Parker MG 1997 AF-2 activity and recruitment of steroid receptor coactivator 1 to the estrogen receptor depend on a lysine residue conserved in nuclear receptors. Mol Cell Biol 17:1832–1839[Abstract]
121. Steinmetz AC, Renaud JP, Moras D 2001 Binding of ligands and activation of transcription by nuclear receptors. Annu Rev Biophys Biomol Struct 30:329–359[CrossRef][Medline]
122. Weatherman RV, Fletterick RJ, Scanlan TS 1999 Nuclear-receptor ligands and ligand-binding domains. Annu Rev Biochem 68:559–581[CrossRef][Medline]
123. Glass CK, Rosenfeld MG 2000 The coregulator exchange in transcriptional functions of nuclear receptors. Genes Dev 14:121–141[Free Full Text]
124. Brzozowski AM, Pike AC, Dauter Z, Hubbard RE, Bonn T, Engstrom O, Ohman L, Greene GL, Gustafsson JA, Carlquist M 1997 Molecular basis of agonism and antagonism in the oestrogen receptor. Nature 389:753–758[CrossRef][Medline]
125. Tanenbaum DM, Wang Y, Williams SP, Sigler PB 1998 Crystallographic comparison of the estrogen and progesterone receptor’s ligand binding domains. Proc Natl Acad Sci USA 95:5998–6003[Abstract/Free Full Text]
126. Feng W, Ribeiro RC, Wagner RL, Nguyen H, Apriletti JW, Fletterick RJ, Baxter JD, Kushner PJ, West BL 1998 Hormone-dependent coactivator binding to a hydrophobic cleft on nuclear receptors. Science 280:1747–1749[Abstract/Free Full Text]
127. Moras D, Gronemeyer H 1998 The nuclear receptor ligand-binding domain: structure and function. Curr Opin Cell Biol 10:384–391[CrossRef][Medline]
128. Pike AC, Brzozowski AM, Hubbard RE, Bonn T, Thorsell AG, Engstrom O, Ljunggren J, Gustafsson JA, Carlquist M 1999 Structure of the ligand-binding domain of oestrogen receptor ß in the presence of a partial agonist and a full antagonist. EMBO J 18:4608–4618[CrossRef][Medline]
129. Pike AC, Brzozowski AM, Walton J, Hubbard RE, Bonn T, Gustafsson JA, Carlquist M 2000 Structural aspects of agonism and antagonism in the oestrogen receptor. Biochem Soc Trans 28:396–400[Medline]
130. Pike AC, Brzozowski AM, Walton J, Hubbard RE, Thorsell AG, Li YL, Gustafsson JA, Carlquist M 2001 Structural insights into the mode of action of a pure antiestrogen. Structure (Camb) 9:145–153
131. Shiau AK, Barstad D, Loria PM, Cheng L, Kushner PJ, Agard DA, Greene GL 1998 The structural basis of estrogen receptor/coactivator recognition and the antagonism of this interaction by tamoxifen. Cell 95:927–937[CrossRef][Medline]
132. Shiau AK, Barstad D, Radek JT, Meyers MJ, Nettles KW, Katzenellenbogen BS, Katzenellenbogen JA, Agard DA, Greene GL 2002 Structural characterization of a subtype-selective ligand reveals a novel mode of estrogen receptor antagonism. Nat Struct Biol 9:359–364[Medline]
133. Smith CL, Nawaz Z, O’Malley BW 1997 Coactivator and corepressor regulation of the agonist/antagonist activity of the mixed antiestrogen, 4-hydroxytamoxifen. Mol Endocrinol 11:657–666[Abstract/Free Full Text]
134. Lavinsky RM, Jepsen K, Heinzel T, Torchia J, Mullen TM, Schiff R, Del-Rio AL, Ricote M, Ngo S, Gemsch J, Hilsenbeck SG, Osborne CK, Glass CK, Rosenfeld MG, Rose DW 1998 Diverse signaling pathways modulate nuclear receptor recruitment of N-CoR and SMRT complexes. Proc Natl Acad Sci USA 95:2920–2925[Abstract/Free Full Text]
135. Jepsen K, Hermanson O, Onami TM, Gleiberman AS, Lunyak V, McEvilly RJ, Kurokawa R, Kumar V, Liu F, Seto E, Hedrick SM, Mandel G, Glass CK, Rose DW, Rosenfeld MG 2000 Combinatorial roles of the nuclear receptor corepressor in transcription and development. Cell 102:753–763[CrossRef][Medline]
136. Shang Y, Hu X, DiRenzo J, Lazar MA, Brown M 2000 Cofactor dynamics and sufficiency in estrogen receptor-regulated transcription. Cell 103:843–852[CrossRef][Medline]
137. Zhang X, Jeyakumar M, Petukhov S, Bagchi MK 1998 A nuclear receptor corepressor modulates transcriptional activity of antagonist-occupied steroid hormone receptor. Mol Endocrinol 12:513–524[Abstract/Free Full Text]
138. Jackson TA, Richer JK, Bain DL, Takimoto GS, Tung L, Horwitz KB 1997 The partial agonist activity of antagonist-occupied steroid receptors is controlled by a novel hinge domain-binding coactivator L7/SPA and the corepressors N-CoR or SMRT. Mol Endocrinol 11:693–705[Abstract/Free Full Text]
139. Webb P, Valentine C, Nguyen P, Price Jr RH, Marimuthu A, West BL, Baxter JD, Kushner PJ 2003 ERß binds N-CoR in the presence of estrogens via an LXXLL-like motif in the N-CoR C-terminus. Nucl Recept 1:4[CrossRef][Medline]
140. Graham JD, Bain DL, Richer JK, Jackson TA, Tung L, Horwitz KB 2000 Thoughts on tamoxifen resistant breast cancer. Are coregulators the answer or just a red herring? J Steroid Biochem Mol Biol 74:255–259[CrossRef][Medline]
141. Kuiper GG, Lemmen JG, Carlsson B, Corton JC, Safe SH, van der Saag PT, van der Burg B, Gustafsson JA 1998 Interaction of estrogenic chemicals and phytoestrogens with estrogen receptor ß. Endocrinology 139:4252–4263[Abstract/Free Full Text]
142. Kuiper GG, Carlsson B, Grandien K, Enmark E, Haggblad J, Nilsson S, Gustafsson JA 1997 Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors and ß. Endocrinology 138:863–870[Abstract/Free Full Text]
143. Perlmann T, Evans RM 1997 Nuclear receptors in Sicily: all in the famiglia. Cell 90:391–397[CrossRef][Medline]
144. McInerney EM, Weis KE, Sun J, Mosselman S, Katzenellenbogen BS 1998 Transcription activation by the human estrogen receptor subtype ß (ER ß) studied with ER ß and ER receptor chimeras. Endocrinology 139:4513–4522[Abstract/Free Full Text]
145. Hall JM, McDonnell DP 1999 The estrogen receptor ß-isoform (ERß) of the human estrogen receptor modulates ER transcriptional activity and is a key regulator of the cellular response to estrogens and antiestrogens. Endocrinology 140:5566–5578[Abstract/Free Full Text]
146. Delaunay F, Pettersson K, Tujague M, Gustafsson JA 2000 Functional differences between the amino-terminal domains of estrogen receptors and ß. Mol Pharmacol 58:584–590[Abstract/Free Full Text]
147. Hyder SM, Chiappetta C, Stancel GM 1999 Interaction of human estrogen receptors and ß with the same naturally occurring estrogen response elements. Biochem Pharmacol 57:597–601[CrossRef][Medline]
148. Cowley SM, Parker MG 1999 A comparison of transcriptional activation by ER and ER ß. J Steroid Biochem Mol Biol 69:165–175[CrossRef][Medline]
149. Paech K, Webb P, Kuiper GG, Nilsson S, Gustafsson J, Kushner PJ, Scanlan TS 1997 Differential ligand activation of estrogen receptors ER and ERß at AP1 sites. Science 277:1508–1510[Abstract/Free Full Text]
150. Wissink S, van der Burg B, Katzenellenbogen BS, van der Saag PT 2001 Synergistic activation of the serotonin-1A receptor by nuclear factor-B and estrogen. Mol Endocrinol 15:543–552[Abstract/Free Full Text]
151. Lazennec G, Bresson D, Lucas A, Chauveau C, Vignon F 2001 ER ß inhibits proliferation and invasion of breast cancer cells. Endocrinology 142:4120–4130[Abstract/Free Full Text]
152. Shughrue P, Scrimo P, Lane M, Askew R, Merchenthaler I 1997 The distribution of estrogen receptor-ß mRNA in forebrain regions of the estrogen receptor- knockout mouse. Endocrinology 138:5649–5652[Abstract/Free Full Text]
153. Rosenfeld CS, Ganjam VK, Taylor JA, Yuan X, Stiehr JR, Hardy MP, Lubahn DB 1998 Transcription and translation of estrogen receptor-ß in the male reproductive tract of estrogen receptor- knock-out and wild-type mice. Endocrinology 139:2982–2987[Abstract/Free Full Text]
154. Couse JF, Lindzey J, Grandien K, Gustafsson JA, Korach KS 1997 Tissue distribution and quantitative analysis of estrogen receptor- (ER) and estrogen receptor-ß (ERß) messenger ribonucleic acid in the wild-type and ER-knockout mouse. Endocrinology 138:4613–4621[Abstract/Free Full Text]
155. Shughrue PJ 1998 Estrogen action in the estrogen receptor -knockout mouse: is this due to ER-ß? Mol Psychiatry 3:299–302[CrossRef][Medline]
156. Shughrue PJ, Lane MV, Merchenthaler I 1999 Biologically active estrogen receptor-ß: evidence from in vivo autoradiographic studies with estrogen receptor -knockout mice. Endocrinology 140:2613–2620[Abstract/Free Full Text]
157. Forster C, Makela S, Warri A, Kietz S, Becker D, Hultenby K, Warner M, Gustafsson JA 2002 Involvement of estrogen receptor ß in terminal differentiation of mammary gland epithelium. Proc Natl Acad Sci USA 99:15578–15583[Abstract/Free Full Text]
158. Russell KS, Haynes MP, Sinha D, Clerisme E, Bender JR 2000 Human vascular endothelial cells contain membrane binding sites for estradiol, which mediate rapid intracellular signaling. Proc Natl Acad Sci USA 97:5930–5935[Abstract/Free Full Text]
159. Pendaries C, Darblade B, Rochaix P, Krust A, Chambon P, Korach KS, Bayard F, Arnal JF 2002 The AF-1 activation-function of ER may be dispensable to mediate the effect of estradiol on endothelial NO production in mice. Proc Natl Acad Sci USA 99:2205–2210[Abstract/Free Full Text]
160. Day JK, Besch-Williford C, McMann TR, Hufford MG, Lubahn DB, MacDonald RS 2001 Dietary genistein increased DMBA-induced mammary adenocarcinoma in wild-type, but not ER KO, mice. Nutr Cancer 39:226–232[CrossRef][Medline]
161. Bocchinfuso WP, Hively WP, Couse JF, Varmus HE, Korach KS 1999 A mouse mammary tumor virus-Wnt-1 transgene induces mammary gland hyperplasia and tumorigenesis in mice lacking estrogen receptor-. Cancer Res 59:1869–1876[Abstract/Free Full Text]
162. Hewitt SC, Bocchinfuso WP, Zhai J, Harrell C, Koonce L, Clark J, Myers P, Korach KS 2002 Lack of ductal development in the absence of functional estrogen receptor delays mammary tumor formation induced by transgenic expression of ErbB2/neu. Cancer Res 62:2798–2805[Abstract/Free Full Text]
163. Anderson TJ, Ferguson DJ, Raab GM 1982 Cell turnover in the "resting" human breast: influence of parity, contraceptive pill, age and laterality. Br J Cancer 46:376–382[Medline]
164. Dickson RB, Huff KK, Spencer EM, Lippman ME 1986 Induction of epidermal growth factor-related polypeptides by 17 ß-estradiol in MCF-7 human breast cancer cells. Endocrinology 118:138–142[Abstract/Free Full Text]
165. Huseby RA, Maloney TM, McGrath CM 1984 Evidence for a direct growth-stimulating effect of estradiol on human MCF-7 cells in vivo. Cancer Res 44:2654–2659[Abstract/Free Full Text]
166. Mueller SO, Clark JA, Myers PH, Korach KS 2002 Mammary gland development in adult mice requires epithelial and stromal estrogen receptor . Endocrinology 143:2357–2365[Abstract/Free Full Text]
167. Allegra JC, Lippman ME, Green L, Barlock A, Simon R, Thompson EB, Huff KK, Griffin W 1979 Estrogen receptor values in patients with benign breast disease. Cancer 44:228–231[CrossRef][Medline]
168. Ricketts D, Turnbull L, Ryall G, Bakhshi R, Rawson NS, Gazet JC, Nolan C, Coombes RC 1991 Estrogen and progesterone receptors in the normal female breast. Cancer Res 51:1817–1822[Abstract/Free Full Text]
169. Petersen OW, Hoyer PE, van Deurs B 1987 Frequency and distribution of estrogen receptor-positive cells in normal, nonlactating human breast tissue. Cancer Res 47:5748–5751[Abstract/Free Full Text]
170. Schmitt FC 1995 Multistep progression from an oestrogen-dependent growth towards an autonomous growth in breast carcinogenesis. Eur J Cancer 31A:2049–2052
171. Markopoulos C, Berger U, Wilson P, Gazet JC, Coombes RC 1988 Oestrogen receptor content of normal breast cells and breast carcinomas throughout the menstrual cycle. Br Med J (Clin Res Ed) 296:1349–1351
172. Williams G, Anderson E, Howell A, Watson R, Coyne J, Roberts SA, Potten CS 1991 Oral contraceptive (OCP) use increases proliferation and decreases oestrogen receptor content of epithelial cells in the normal human breast. Int J Cancer 48:206–210[Medline]
173. Battersby S, Robertson BJ, Anderson TJ, King RJ, McPherson K 1992 Influence of menstrual cycle, parity and oral contraceptive use on steroid hormone receptors in normal breast. Br J Cancer 65:601–607[Medline]
174. Russo J, Ao X, Grill C, Russo IH 1999 Pattern of distribution of cells positive for estrogen receptor and progesterone receptor in relation to proliferating cells in the mammary gland. Breast Cancer Res Treat 53:217–227[CrossRef][Medline]
175. Clarke RB, Howell A, Potten CS, Anderson E 1997 Dissociation between steroid receptor expression and cell proliferation in the human breast. Cancer Res 57:4987–4991[Abstract/Free Full Text]
176. Russo J, Hu YF, Yang X, Russo IH 2000 Developmental, cellular, and molecular basis of human breast cancer. J Natl Cancer Inst Monogr 27:17–37
177. Roger P, Sahla ME, Makela S, Gustafsson JA, Baldet P, Rochefort H 2001 Decreased expression of estrogen receptor ß protein in proliferative preinvasive mammary tumors. Cancer Res 61:2537–2541[Abstract/Free Full Text]
178. Shaw JA, Udokang K, Mosquera JM, Chauhan H, Jones JL, Walker RA 2002 Oestrogen receptors and ß differ in normal human breast and breast carcinomas. J Pathol 198:450–457[CrossRef][Medline]
179. Critchley HO, Henderson TA, Kelly RW, Scobie GS, Evans LR, Groome NP, Saunders PT 2002 Wild-type estrogen receptor (ERß1) and the splice variant (ERßcx/ß2) are both expressed within the human endometrium throughout the normal menstrual cycle. J Clin Endocrinol Metab 87:5265–5273[Abstract/Free Full Text]
180. Jarvinen TA, Pelto-Huikko M, Holli K, Isola J 2000 Estrogen receptor ß is coexpressed with ER and PR and associated with nodal status, grade, and proliferation rate in breast cancer. Am J Pathol 156:29–35[Abstract/Free Full Text]
181. Zafrani B, Leroyer A, Fourquet A, Laurent M, Trophilme D, Validire P, Sastre-Garau X 1994 Mammographically detected ductal in situ carcinoma of the breast analyzed with a new classification. A study of 127 cases: correlation with estrogen and progesterone receptors, p53 and c-erbB-2 proteins, and proliferative activity. Semin Diagn Pathol 11:208–214[Medline]
182. Chauchereau A, Savouret JF, Milgrom E 1992 Control of biosynthesis and post-transcriptional modification of the progesterone receptor. Biol Reprod 46:174–177[Abstract]
183. Pallis L, Wilking N, Cedermark B, Rutqvist LE, Skoog L 1992 Receptors for estrogen and progesterone in breast carcinoma in situ. Anticancer Res 12:2113–2115[Medline]
184. Karayiannakis AJ, Bastounis EA, Chatzigianni EB, Makri GG, Alexiou D, Karamanakos P 1996 Immunohistochemical detection of oestrogen receptors in ductal carcinoma in situ of the breast. Eur J Surg Oncol 22:578–582[CrossRef][Medline]
185. Albonico G, Querzoli P, Ferretti S, Magri E, Nenci I 1996 Biophenotypes of breast carcinoma in situ defined by image analysis of biological parameters. Pathol Res Pract 192:117–123[Medline]
186. Giri DD, Dundas SA, Nottingham JF, Underwood JC 1989 Oestrogen receptors in benign epithelial lesions and intraduct carcinomas of the breast: an immunohistological study. Histopathology 15:575–584[Medline]
187. Barnes R, Masood S 1990 Potential value of hormone receptor assay in carcinoma in situ of breast. Am J Clin Pathol 94:533–537[Medline]
188. Helin HJ, Helle MJ, Kallioniemi OP, Isola JJ 1989 Immunohistochemical determination of estrogen and progesterone receptors in human breast carcinoma. Correlation with histopathology and DNA flow cytometry. Cancer 63:1761–1767[CrossRef][Medline]
189. Poller DN, Snead DR, Roberts EC, Galea M, Bell JA, Gilmour A, Elston CW, Blamey RW, Ellis IO 1993 Oestrogen receptor expression in ductal carcinoma in situ of the breast: relationship to flow cytometric analysis of DNA and expression of the c-erbB-2 oncoprotein. Br J Cancer 68:156–161[Medline]
190. Chaudhuri B, Crist KA, Mucci S, Malafa M, Chaudhuri PK 1993 Distribution of estrogen receptor in ductal carcinoma in situ of the breast. Surgery 113:134–137[Medline]
191. Leal CB, Schmitt FC, Bento MJ, Maia NC, Lopes CS 1995 Ductal carcinoma in situ of the breast. Histologic categorization and its relationship to ploidy and immunohistochemical expression of hormone receptors, p53, and c-erbB-2 protein. Cancer 75:2123–2131[CrossRef][Medline]
192. Bose S, Lesser ML, Norton L, Rosen PP 1996 Immunophenotype of intraductal carcinoma. Arch Pathol Lab Med 120:81–85[Medline]
193. Roger P, Daures JP, Maudelonde T, Pignodel C, Gleizes M, Chapelle J, Marty-Double C, Baldet P, Mares P, Laffargue F, Rochefort H 2000 Dissociated overexpression of cathepsin D and estrogen receptor in preinvasive mammary tumors. Hum Pathol 31:593–600[CrossRef][Medline]
194. Speirs V, Kerin MJ 2000 Prognostic significance of oestrogen receptor ß in breast cancer. Br J Surg 87:405–409[CrossRef][Medline]
195. Fuqua S, Schiff R, Parra I, Moore JT, Mohsin S, Osborne CK, Clark GM, Allred DC 2003 Estrogen receptor ß protein in human breast cancer: correlation with clinical tumor parameters. Cancer Res 63:2434–2439[Abstract/Free Full Text]
196. Skliris GP, Carder PJ, Lansdown MR, Speirs V 2001 Immunohistochemical detection of ERß in breast cancer: towards more detailed receptor profiling? Br J Cancer 84:1095–1098[CrossRef][Medline]
197. Skliris GP, Munot K, Bell SM, Carder PJ, Lane S, Horgan K, Lansdown MR, Parkes AT, Hanby AM, Markham AF, Speirs V 2003 Reduced expression of oestrogen receptor ß in invasive breast cancer and its re-expression using DNA methyl transferase inhibitors in a cell line model. J Pathol 201:213–220[CrossRef][Medline]
198. Shaaban AM, O’Neill PA, Davies MP, Sibson R, West CR, Smith PH, Foster CS 2003 Declining estrogen receptor-ß expression defines malignant progression of human breast neoplasia. Am J Surg Pathol 27:1502–1512[Medline]
199. Speirs V 2002 Oestrogen receptor ß in breast cancer: good, bad or still too early to tell? J Pathol 197:143–147[CrossRef][Medline]
200. Knowlden JM, Gee JM, Robertson JF, Ellis IO, Nicholson RI 2000 A possible divergent role for the oestrogen receptor and ß subtypes in clinical breast cancer. Int J Cancer 89:209–212[CrossRef][Medline]
201. Iwao K, Miyoshi Y, Egawa C, Ikeda N, Tsukamoto F, Noguchi S 2000 Quantitative analysis of estrogen receptor- and -ß messenger RNA expression in breast carcinoma by real-time polymerase chain reaction. Cancer 89:1732–1738[CrossRef][Medline]
202. Iwao K, Miyoshi Y, Egawa C, Ikeda N, Noguchi S 2000 Quantitative analysis of estrogen receptor-ß mRNA and its variants in human breast cancers. Int J Cancer 88:733–736[CrossRef][Medline]
203. Omoto Y, Kobayashi S, Inoue S, Ogawa S, Toyama T, Yamashita H, Muramatsu M, Gustafsson JA, Iwase H 2002 Evaluation of oestrogen receptor ß wild-type and variant protein expression, and relationship with clinicopathological factors in breast cancers. Eur J Cancer 38:380–386[CrossRef][Medline]
204. Omoto Y, Inoue S, Ogawa S, Toyama T, Yamashita H, Muramatsu M, Kobayashi S, Iwase H 2001 Clinical value of the wild-type estrogen receptor ß expression in breast cancer. Cancer Lett 163:207–212[CrossRef][Medline]
205. Mann S, Laucirica R, Carlson N, Younes PS, Ali N, Younes A, Li Y, Younes M 2001 Estrogen receptor ß expression in invasive breast cancer. Hum Pathol 32:113–118[CrossRef][Medline]
206. Miyoshi Y, Taguchi T, Gustafsson JA, Noguchi S 2001 Clinicopathological characteristics of estrogen receptor-ß-positive human breast cancers. Jpn J Cancer Res 92:1057–1061[CrossRef][Medline]
207. Jensen EV, Cheng G, Palmieri C, Saji S, Makela S, Van Noorden S, Wahlstrom T, Warner M, Coombes RC, Gustafsson JA 2001 Estrogen receptors and proliferation markers in primary and recurrent breast cancer. Proc Natl Acad Sci USA 98:15197–15202[Abstract/Free Full Text]
208. Harvey JM, Clark GM, Osborne CK, Allred DC 1999 Estrogen receptor status by immunohistochemistry is superior to the ligand-binding assay for predicting response to adjuvant endocrine therapy in breast cancer. J Clin Oncol 17:1474–1481[Abstract/Free Full Text]
209. Allred DC, Harvey JM, Berardo M, Clark GM 1998 Prognostic and predictive factors in breast cancer by immunohistochemical analysis. Mod Pathol 11:155–168[Medline]
210. Leygue E, Dotzlaw H, Watson PH, Murphy LC 1998 Altered estrogen receptor and ß messenger RNA expression during human breast tumorigenesis. Cancer Res 58:3197–3201[Abstract/Free Full Text]
211. Brand H, Kos M, Denger S, Flouriot G, Gromoll J, Gannon F, Reid G 2002 A novel promoter is involved in the expression of estrogen receptor in human testis and epididymis. Endocrinology 143:3397–3404[Abstract/Free Full Text]
212. Piva R, Bianchi N, Aguiari GL, Gambari R, del Senno L 1993 Sequencing of an RNA transcript of the human estrogen receptor gene: evidence for a new transcriptional event. J Steroid Biochem Mol Biol 46:531–538[CrossRef][Medline]
213. Thompson DA, McPherson LA, Carmeci C, deConinck EC, Weigel RJ 1997 Identification of two estrogen receptor transcripts with novel 5' exons isolated from a MCF7 cDNA library. J Steroid Biochem Mol Biol 62:143–153[CrossRef][Medline]
214. Keaveney M, Klug J, Dawson MT, Nestor PV, Neilan JG, Forde RC, Gannon F 1991 Evidence for a previously unidentified upstream exon in the human oestrogen receptor gene. J Mol Endocrinol 6:111–115[Abstract/Free Full Text]
215. Grandien K 1996 Determination of transcription start sites in the human estrogen receptor gene and identification of a novel, tissue-specific, estrogen receptor-mRNA isoform. Mol Cell Endocrinol 116:207–212[CrossRef][Medline]
216. Flouriot G, Griffin C, Kenealy M, Sonntag-Buck V, Gannon F 1998 Differentially expressed messenger RNA isoforms of the human estrogen receptor- gene are generated by alternative splicing and promoter usage. Mol Endocrinol 12:1939–1954[Abstract/Free Full Text]
217. Kos M, Reid G, Denger S, Gannon F 2001 Minireview: genomic organization of the human ER gene promoter region. Mol Endocrinol 15:2057–2063[Abstract/Free Full Text]
218. Kos M, Denger S, Reid G, Gannon F 2002 Upstream open reading frames regulate the translation of the multiple mRNA variants of the estrogen receptor . J Biol Chem 277:37131–37138[Abstract/Free Full Text]
219. Reid G, Denger S, Kos M, Gannon F 2002 Human estrogen receptor-: regulation by synthesis, modification and degradation. Cell Mol Life Sci 59:821–831[CrossRef][Medline]
220. Petursdottir V, Moslemi AR, Persson M, Nordborg E, Nordborg C 2001 Estrogen receptor in giant cell arteritis: a molecular genetic study. Clin Exp Rheumatol 19:297–302[Medline]
221. Kassi EN, Vlachoyiannopoulos PG, Moutsopoulos HM, Sekeris CE, Moutsatsou P 2001 Molecular analysis of estrogen receptor and ß in lupus patients. Eur J Clin Invest 31:86–93[CrossRef][Medline]
222. Chaidarun SS, Klibanski A, Alexander JM 1997 Tumor-specific expression of alternatively spliced estrogen receptor messenger ribonucleic acid variants in human pituitary adenomas. J Clin Endocrinol Metab 82:1058–1065[Abstract/Free Full Text]
223. Pfeffer U, Fecarotta E, Vidali G 1995 Coexpression of multiple estrogen receptor variant messenger RNAs in normal and neoplastic breast tissues and in MCF-7 cells. Cancer Res 55:2158–2165[Abstract/Free Full Text]
224. Rice LW, Jazaeri AA, Shupnik MA 1997 Estrogen receptor mRNA splice variants in pre- and postmenopausal human endometrium and endometrial carcinoma. Gynecol Oncol 65:149–157[CrossRef][Medline]
225. Zhang QX, Hilsenbeck SG, Fuqua SA, Borg A 1996 Multiple splicing variants of the estrogen receptor are present in individual human breast tumors. J Steroid Biochem Mol Biol 59:251–260[CrossRef][Medline]
226. Murphy LC, Wang M, Coutt A, Dotzlaw H 1996 Novel mutations in the estrogen receptor messenger RNA in human breast cancers. J Clin Endocrinol Metab 81:1420–1427[Abstract]
227. Anandappa SY, Sibson R, Platt-Higgins A, Winstanley JH, Rudland PS, Barraclough R 2000 Variant estrogen receptor mRNAs in human breast cancer specimens. Int J Cancer 88:209–216[CrossRef][Medline]
228. Wang Y, Miksicek RJ 1991 Identification of a dominant negative form of the human estrogen receptor. Mol Endocrinol 5:1707–1715[Abstract/Free Full Text]
229. Ignar-Trowbridge DM, Pimentel M, Parker MG, McLachlan JA, Korach KS 1996 Peptide growth factor cross-talk with the estrogen receptor requires the A/B domain and occurs independently of protein kinase C or estradiol. Endocrinology 137:1735–1744[Abstract]
230. Madsen MW, Reiter BE, Larsen SS, Briand P, Lykkesfeldt AE 1997 Estrogen receptor messenger RNA splice variants are not involved in antiestrogen resistance in sublines of MCF-7 human breast cancer cells. Cancer Res 57:585–589[Abstract/Free Full Text]
231. Leygue ER, Watson PH, Murphy LC 1996 Estrogen receptor variants in normal human mammary tissue. J Natl Cancer Inst 88:284–290[Abstract/Free Full Text]
232. Daffada AA, Dowsett M 1995 Tissue-dependent expression of a novel splice variant of the human oestrogen receptor. J Steroid Biochem Mol Biol 55:413–421[CrossRef][Medline]
233. Horvath G, Leser G, Hahlin M, Henriksson M 2000 Exon deletions and variants of human estrogen receptor mRNA in endometrial hyperplasia and adenocarcinoma. Int J Gynecol Cancer 10:128–136[CrossRef][Medline]
234. Iwase H, Omoto Y, Iwata H, Hara Y, Ando Y, Kobayashi S 1998 Genetic and epigenetic alterations of the estrogen receptor gene and hormone independence in human breast cancer. Oncology 55(Suppl 1):11–16
235. Erenburg I, Schachter B, Mira y Lopez R, Ossowski L 1997 Loss of an estrogen receptor isoform (ER 3) in breast cancer and the consequences of its reexpression: interference with estrogen-stimulated properties of malignant transformation. Mol Endocrinol 11:2004–2015[Abstract/Free Full Text]
236. Miksicek RJ, Lei Y, Wang Y 1993 Exon skipping gives rise to alternatively spliced forms of the estrogen receptor in breast tumor cells. Breast Cancer Res Treat 26:163–174[CrossRef][Medline]
237. Koehorst SG, Cox JJ, Donker GH, Lopes da Silva S, Burbach JP, Thijssen JH, Blankenstein MA 1994 Functional analysis of an alternatively spliced estrogen receptor lacking exon 4 isolated from MCF-7 breast cancer cells and meningioma tissue. Mol Cell Endocrinol 101:237–245[CrossRef][Medline]
238. Leygue E, Huang A, Murphy LC, Watson PH 1996 Prevalence of estrogen receptor variant messenger RNAs in human breast cancer. Cancer Res 56:4324–4327[Abstract/Free Full Text]
239. Fuqua SA, Fitzgerald SD, Chamness GC, Tandon AK, McDonnell DP, Nawaz Z, O’Malley BW, McGuire WL 1991 Variant human breast tumor estrogen receptor with constitutive transcriptional activity. Cancer Res 51:105–109[Abstract/Free Full Text]
240. Fuqua S, Wiltschke C, Castles CG, Wolf DC, Allred DC 1995 A role for estrogen-receptor variants in endocrine resistance. Endocr Rel Cancer 2:19–25[Medline]
241. Lemieux P, Fuqua S 1996 The role of the estrogen receptor in tumor progression. J Steroid Biochem Mol Biol 56:87–91[CrossRef][Medline]
242. Rea D, Parker MG 1996 Effects of an exon 5 variant of the estrogen receptor in MCF-7 breast cancer cells. Cancer Res 56:1556–1563[Abstract/Free Full Text]
243. Daffada AA, Johnston SR, Smith IE, Detre S, King N, Dowsett M 1995 Exon 5 deletion variant estrogen receptor messenger RNA expression in relation to tamoxifen resistance and progesterone receptor/pS2 status in human breast cancer. Cancer Res 55:288–293[Abstract/Free Full Text]
244. Fuqua SA, Allred DC, Auchus RJ 1993 Expression of estrogen receptor variants. J Cell Biochem Suppl 17G:194–197
245. Castles CG, Fuqua SA, Klotz DM, Hill SM 1993 Expression of a constitutively active estrogen receptor variant in the estrogen receptor-negative BT-20 human breast cancer cell line. Cancer Res 53:5934–5939[Abstract/Free Full Text]
246. Desai AJ, Luqmani YA, Walters JE, Coope RC, Dagg B, Gomm JJ, Pace PE, Rees CN, Thirunavukkarasu V, Shousha S, Groome NP, Coombes R, Ali S 1997 Presence of exon 5-deleted oestrogen receptor in human breast cancer: functional analysis and clinical significance. Br J Cancer 75:1173–1184[Medline]
247. Zhang QX, Borg A, Fuqua SA 1993 An exon 5 deletion variant of the estrogen receptor frequently coexpressed with wild-type estrogen receptor in human breast cancer. Cancer Res 53:5882–5884[Abstract/Free Full Text]
248. Pfeffer U, Fecarotta E, Arena G, Forlani A, Vidali G 1996 Alternative splicing of the estrogen receptor primary transcript normally occurs in estrogen receptor positive tissues and cell lines. J Steroid Biochem Mol Biol 56:99–105[CrossRef][Medline]
249. Wilson KB, Evans M, Abdou NI 1996 Presence of a variant form of the estrogen receptor in peripheral blood mononuclear cells from normal individuals and lupus patients. J Reprod Immunol 31:199–208[CrossRef][Medline]
250. Suenaga R, Evans MJ, Mitamura K, Rider V, Abdou NI 1998 Peripheral blood T cells and monocytes and B cell lines derived from patients with lupus express estrogen receptor transcripts similar to those of normal cells. J Rheumatol 25:1305–1312[Medline]
251. Poola I, Speirs V 2001 Expression of alternatively spliced estrogen receptor mRNAs is increased in breast cancer tissues. J Steroid Biochem Mol Biol 78:459–469[CrossRef][Medline]
252. Poola I, Koduri S, Chatra S, Clarke R 2000 Identification of twenty alternatively spliced estrogen receptor mRNAs in breast cancer cell lines and tumors using splice targeted primer approach. J Steroid Biochem Mol Biol 72:249–258[CrossRef][Medline]
253. McGuire WL, Chamness GC, Fuqua SA 1991 Estrogen receptor variants in clinical breast cancer. Mol Endocrinol 5:1571–1577[Abstract/Free Full Text]
254. Fuqua SA, Fitzgerald SD, Allred DC, Elledge RM, Nawaz Z, McDonnell DP, O’Malley BW, Greene GL, McGuire WL 1992 Inhibition of estrogen receptor action by a naturally occurring variant in human breast tumors. Cancer Res 52:483–486[Abstract/Free Full Text]
255. Garcia Pedrero JM, Zuazua P, Martinez-Campa C, Lazo PS, Ramos S 2003 The naturally occurring variant of estrogen receptor (ER) ERE7 suppresses estrogen-dependent transcriptional activation by both wild-type ER and ERß. Endocrinology 144:2967–2976[Abstract/Free Full Text]
256. Koehorst SG, Jacobs HM, Thijssen JH, Blankenstein MA 1993 Wild type and alternatively spliced estrogen receptor messenger RNA in human meningioma tissue and MCF7 breast cancer cells. J Steroid Biochem Mol Biol 45:227–233[CrossRef][Medline]
257. Ye Q, Chung LW, Cinar B, Li S, Zhau HE 2000 Identification and characterization of estrogen receptor variants in prostate cancer cell lines. J Steroid Biochem Mol Biol 75:21–31[CrossRef][Medline]
258. Pink JJ, Wu SQ, Wolf DM, Bilimoria MM, Jordan VC 1996 A novel 80 kDa human estrogen receptor containing a duplication of exons 6 and 7. Nucleic Acids Res 24:962–969[Abstract/Free Full Text]
259. Pink JJ, Jordan VC 1996 Models of estrogen receptor regulation by estrogens and antiestrogens in breast cancer cell lines. Cancer Res 56:2321–2330[Abstract/Free Full Text]
260. Pink JJ, Jiang SY, Fritsch M, Jordan VC 1995 An estrogen-independent MCF-7 breast cancer cell line which contains a novel 80-kilodalton estrogen receptor-related protein. Cancer Res 55:2583–2590[Abstract/Free Full Text]
261. Pink JJ, Fritsch M, Bilimoria MM, Assikis VJ, Jordan VC 1997 Cloning and characterization of a 77-kDa oestrogen receptor isolated from a human breast cancer cell line. Br J Cancer 75:17–27[Medline]
262. Wang M, Dotzlaw H, Fuqua SA, Murphy LC 1997 A point mutation in the human estrogen receptor gene is associated with the expression of an abnormal estrogen receptor mRNA containing a 69 novel nucleotide insertion. Breast Cancer Res Treat 44:145–151[CrossRef][Medline]
263. Karnik PS, Kulkarni S, Liu XP, Budd GT, Bukowski RM 1994 Estrogen receptor mutations in tamoxifen-resistant breast cancer. Cancer Res 54:349–353[Abstract/Free Full Text]
264. Kumar V, Green S, Staub A, Chambon P 1986 Localisation of the oestradiol-binding and putative DNA-binding domains of the human oestrogen receptor. EMBO J 5:2231–2236[Medline]
265. Ali S, Metzger D, Bornert JM, Chambon P 1993 Modulation of transcriptional activation by ligand-dependent phosphorylation of the human oestrogen receptor A/B region. EMBO J 12:1153–1160[Medline]
266. Huang A, Pettigrew NM, Watson PH 1996 Immunohistochemical assay for oestrogen receptors in paraffin wax sections of breast carcinoma using a new monoclonal antibody. J Pathol 180:223–227[CrossRef][Medline]
267. Saccani Jotti G, Johnston SR, Salter J, Detre S, Dowsett M 1994 Comparison of new immunohistochemical assay for oestrogen receptor in paraffin wax embedded breast carcinoma tissue with quantitative enzyme immunoassay. J Clin Pathol 47:900–905[Abstract/Free Full Text]
268. Huang A, Leygue ER, Snell L, Murphy LC, Watson PH 1997 Expression of estrogen receptor variant messenger RNAs and determination of estrogen receptor status in human breast cancer. Am J Pathol 150:1827–1833[Abstract]
269. Park W, Choi JJ, Hwang ES, Lee JH 1996 Identification of a variant estrogen receptor lacking exon 4 and its coexpression with wild-type estrogen receptor in ovarian carcinomas. Clin Cancer Res 2:2029–2035[Abstract]
270. Inoue S, Ogawa S, Horie K, Hoshino S, Goto W, Hosoi T, Tsutsumi O, Muramatsu M, Ouchi Y 2000 An estrogen receptor ß isoform that lacks exon 5 has dominant negative activity on both ER and ERß. Biochem Biophys Res Commun 279:814–819[CrossRef][Medline]
271. Roodi N, Bailey LR, Kao WY, Verrier CS, Yee CJ, Dupont WD, Parl FF 1995 Estrogen receptor gene analysis in estrogen receptor-positive and receptor-negative primary breast cancer. J Natl Cancer Inst 87:446–451[Abstract/Free Full Text]
272. Zhang QX, Borg A, Wolf DM, Oesterreich S, Fuqua SA 1997 An estrogen receptor mutant with strong hormone-independent activity from a metastatic breast cancer. Cancer Res 57:1244–1249[Abstract/Free Full Text]
273. Fuqua SA, Wiltschke C, Zhang QX, Borg A, Castles CG, Friedrichs WE, Hopp T, Hilsenbeck S, Mohsin S, O’Connell P, Allred DC 2000 A hypersensitive estrogen receptor- mutation in premalignant breast lesions. Cancer Res 60:4026–4029[Abstract/Free Full Text]
274. McGuire WL, Chamness GC, Fuqua SA 1992 Abnormal estrogen receptor in clinical breast cancer. J Steroid Biochem Mol Biol 43:243–247[CrossRef][Medline]
275. Garcia T, Lehrer S, Bloomer WD, Schachter B 1988 A variant estrogen receptor messenger ribonucleic acid is associated with reduced levels of estrogen binding in human mammary tumors. Mol Endocrinol 2:785–791[Abstract/Free Full Text]
276. Garcia T, Sanchez M, Cox JL, Shaw PA, Ross JB, Lehrer S, Schachter B 1989 Identification of a variant form of the human estrogen receptor with an amino acid replacement. Nucleic Acids Res 17:8364[Free Full Text]
277. Lehrer S, Rabin J, Stone J, Berkowitz GS 1994 Association of an estrogen receptor variant with increased height in women. Horm Metab Res 26:486–488[Medline]
278. Lehrer S, Sanchez M, Song HK, Dalton J, Levine E, Savoretti P, Thung SN, Schachter B 1990 Oestrogen receptor B-region polymorphism and spontaneous abortion in women with breast cancer. Lancet 335:622–624[CrossRef][Medline]
279. Schmutzler RK, Sanchez M, Lehrer S, Chaparro CA, Phillips C, Rabin J, Schachter B 1991 Incidence of an estrogen receptor polymorphism in breast cancer patients. Breast Cancer Res Treat 19:111–117[CrossRef][Medline]
280. Zhang Z, Yamashita H, Toyama T, Omoto Y, Sugiura H, Hara Y, Haruki N, Kobayashi S, Iwase H 2003 Estrogen receptor mutation (A-to-G transition at nucleotide 908) is not found in different types of breast lesions from Japanese women. Breast Cancer 10:70–73[Medline]
281. Wang C, Fu M, Angeletti RH, Siconolfi-Baez L, Reutens AT, Albanese C, Lisanti MP, Katzenellenbogen BS, Kato S, Hopp T, Fuqua SA, Lopez GN, Kushner PJ, Pestell RG 2001 Direct acetylation of the estrogen receptor hinge region by p300 regulates transactivation and hormone sensitivity. J Biol Chem 276:18375–18383[Abstract/Free Full Text]
282. Graham 2nd ML, Krett NL, Miller LA, Leslie KK, Gordon DF, Wood WM, Wei LL, Horwitz KB 1990 T47DCO cells, genetically unstable and containing estrogen receptor mutations, are a model for the progression of breast cancers to hormone resistance. Cancer Res 50:6208–6217[Abstract/Free Full Text]
283. Kohler MF, Berkholz A, Risinger JI, Elbendary A, Boyd J, Berchuck A 1995 Mutational analysis of the estrogen-receptor gene in endometrial carcinoma. Obstet Gynecol 86:33–37[CrossRef][Medline]
284. Castoria G, Migliaccio A, Green S, Di Domenico M, Chambon P, Auricchio F 1993 Properties of a purified estradiol-dependent calf uterus tyrosine kinase. Biochemistry 32:1740–1750[CrossRef][Medline]
285. Arnold SF, Notides AC 1995 An antiestrogen: a phosphotyrosyl peptide that blocks dimerization of the human estrogen receptor. Proc Natl Acad Sci USA 92:7475–7479[Abstract/Free Full Text]
286. Arnold SF, Obourn JD, Jaffe H, Notides AC 1995 Phosphorylation of the human estrogen receptor on tyrosine 537 in vivo and by src family tyrosine kinases in vitro. Mol Endocrinol 9:24–33[Abstract/Free Full Text]
287. Assikis VJ, Bilimoria MM, Muenzner HD, Lurain JR, Jordan VC 1996 Mutations of the estrogen receptor in endometrial carcinoma: evidence of an association with high tumor grade. Gynecol Oncol 63:192–199[CrossRef][Medline]
288. Malamitsi-Puchner A, Tziotis J, Evangelopoulos D, Fountas L, Vlachos G, Creatsas G, Sekeris CE, Moutsatsou P 2001 Gene analysis of the N-terminal region of the estrogen receptor in preeclampsia. Steroids 66:695–700[CrossRef][Medline]
289. Dotzlaw H, Alkhalaf M, Murphy LC 1992 Characterization of estrogen receptor variant mRNAs from human breast cancers. Mol Endocrinol 6:773–785[Abstract/Free Full Text]
290. Iwase H, Kobayashi S, Iwata H, Yamashita T, Ito K, Toyama T, Hara Y, Greenman J, Mathew CG 1996 [Molecular analysis of the estrogen receptor (ER) gene in association with ER negativity in breast cancer]. Gan To Kagaku Ryoho 23(Suppl 1):61–65
291. Iwase H, Greenman JM, Barnes DM, Hodgson S, Bobrow L, Mathew CG 1996 Sequence variants of the estrogen receptor (ER) gene found in breast cancer patients with ER negative and progesterone receptor positive tumors. Cancer Lett 108:179–184[CrossRef][Medline]
292. Jurada S, Marc J, Prezelj J, Kocijancic A, Komel R 2001 Codon 325 sequence polymorphism of the estrogen receptor gene and bone mineral density in postmenopausal women. J Steroid Biochem Mol Biol 78:15–20[CrossRef][Medline]
293. MacGregor Schafer J, Liu H, Levenson AS, Horiguchi J, Chen Z, Jordan VC 2001 Estrogen receptor mediated induction of the transforming growth factor gene by estradiol and 4-hydroxytamoxifen in MDA-MB-231 breast cancer cells. J Steroid Biochem Mol Biol 78:41–50[CrossRef][Medline]
294. Lonard DM, Nawaz Z, Smith CL, O’Malley BW 2000 The 26S proteasome is required for estrogen receptor- and coactivator turnover and for efficient estrogen receptor- transactivation. Mol Cell 5:939–948[CrossRef][Medline]
295. Lazennec G, Thomas JA, Katzenellenbogen BS 2001 Involvement of cyclic AMP response element binding protein (CREB) and estrogen receptor phosphorylation in the synergistic activation of the estrogen receptor by estradiol and protein kinase activators. J Steroid Biochem Mol Biol 77:193–203[CrossRef][Medline]
296. Zajchowski DA, Webster L, Humm R, White 3rd FA, Simmons SJ, Bartholdi M 1997 Different estrogen receptor structural domains are required for estrogen- and tamoxifen-dependent anti-proliferative activity in human mammary epithelial cells expressing an exogenous estrogen receptor. J Steroid Biochem Mol Biol 62:373–383[CrossRef][Medline]
297. Zhuang Y, Katzenellenbogen BS, Shapiro DJ 1995 Estrogen receptor mutants which do not bind 17 ß-estradiol dimerize and bind to the estrogen response element in vivo. Mol Endocrinol 9:457–466[Abstract/Free Full Text]
298. Wrenn CK, Katzenellenbogen BS 1993 Structure-function analysis of the hormone binding domain of the human estrogen receptor by region-specific mutagenesis and phenotypic screening in yeast. J Biol Chem 268:24089–24098[Abstract/Free Full Text]
299. Kraus WL, Weis KE, Katzenellenbogen BS 1997 Determinants for the repression of estrogen receptor transcriptional activity by ligand-occupied progestin receptors. J Steroid Biochem Mol Biol 63:175–188[CrossRef][Medline]
300. Pakdel F, Reese JC, Katzenellenbogen BS 1993 Identification of charged residues in an N-terminal portion of the hormone-binding domain of the human estrogen receptor important in transcriptional activity of the receptor. Mol Endocrinol 7:1408–1417[Abstract/Free Full Text]
301. Huang HJ, Norris JD, McDonnell DP 2002 Identification of a negative regulatory surface within estrogen receptor provides evidence in support of a role for corepressors in regulating cellular responses to agonists and antagonists. Mol Endocrinol 16:1778–1792[Abstract/Free Full Text]
302. Norris JD, Fan D, Stallcup MR, McDonnell DP 1998 Enhancement of estrogen receptor transcriptional activity by the coactivator GRIP-1 highlights the role of activation function 2 in determining estrogen receptor pharmacology. J Biol Chem 273:6679–6688[Abstract/Free Full Text]
303. Pakdel F, Katzenellenbogen BS 1992 Human estrogen receptor mutants with altered estrogen and antiestrogen ligand discrimination. J Biol Chem 267:3429–3437[Abstract/Free Full Text]
304. Schwartz JA, Zhong L, Deighton-Collins S, Zhao C, Skafar DF 2002 Mutations targeted to a predicted helix in the extreme carboxyl-terminal region of the human estrogen receptor- alter its response to estradiol and 4-hydroxytamoxifen. J Biol Chem 277:13202–13209[Abstract/Free Full Text]
305. Liu H, Lee ES, Deb Los Reyes A, Zapf JW, Jordan VC 2001 Silencing and reactivation of the selective estrogen receptor modulator-estrogen receptor complex. Cancer Res 61:3632–3639[Abstract/Free Full Text]
306. Karas RH, Gauer EA, Bieber HE, Baur WE, Mendelsohn ME 1998 Growth factor activation of the estrogen receptor in vascular cells occurs via a mitogen-activated protein kinase-independent pathway. J Clin Invest 101:2851–2861[Medline]
307. Joel PB, Traish AM, Lannigan DA 1995 Estradiol and phorbol ester cause phosphorylation of serine 118 in the human estrogen receptor. Mol Endocrinol 9:1041–1052[Abstract/Free Full Text]
308. Joel PB, Smith J, Sturgill TW, Fisher TL, Blenis J, Lannigan DA 1998 pp90rsk1 Regulates estrogen receptor-mediated transcription through phosphorylation of Ser-167. Mol Cell Biol 18:1978–1984[Abstract/Free Full Text]
309. Chen D, Washbrook E, Sarwar N, Bates GJ, Pace PE, Thirunuvakkarasu V, Taylor J, Epstein RJ, Fuller-Pace FV, Egly JM, Coombes RC, Ali S 2002 Phosphorylation of human estrogen receptor at serine 118 by two distinct signal transduction pathways revealed by phosphorylation-specific antisera. Oncogene 21:4921–4931[CrossRef][Medline]
310. Rogatsky I, Trowbridge JM, Garabedian MJ 1999 Potentiation of human estrogen receptor transcriptional activation through phosphorylation of serines 104 and 106 by the cyclin A-CDK2 complex. J Biol Chem 274:22296–22302[Abstract/Free Full Text]
311. Le Goff P, Montano MM, Schodin DJ, Katzenellenbogen BS 1994 Phosphorylation of the human estrogen receptor. Identification of hormone-regulated sites and examination of their influence on transcriptional activity. J Biol Chem 269:4458–4466[Abstract/Free Full Text]
312. Castano E, Chen CW, Vorojeikina DP, Notides AC 1998 The role of phosphorylation in human estrogen receptor function. J Steroid Biochem Mol Biol 65:101–110[CrossRef][Medline]
313. Lu Q, Ebling H, Mittler J, Baur WE, Karas RH 2002 MAP kinase mediates growth factor-induced nuclear translocation of estrogen receptor . FEBS Lett 516:1–8[CrossRef][Medline]
314. Wolf DM, Jordan VC 1994 The estrogen receptor from a tamoxifen stimulated MCF-7 tumor variant contains a point mutation in the ligand binding domain. Breast Cancer Res Treat 31:129–138[CrossRef][Medline]
315. Wolf DM, Jordan VC 1994 Characterization of tamoxifen stimulated MCF-7 tumor variants grown in athymic mice. Breast Cancer Res Treat 31:117–127[CrossRef][Medline]
316. Liu H, Park WC, Bentrem DJ, McKian KP, Reyes Ade L, Loweth JA, Schafer JM, Zapf JW, Jordan VC 2002 Structure-function relationships of the raloxifene-estrogen receptor- complex for regulating transforming growth factor- expression in breast cancer cells. J Biol Chem 277:9189–9198[Abstract/Free Full Text]
317. Bentrem D, Dardes R, Liu H, MacGregor-Schafer J, Zapf J, Jordan V 2001 Molecular mechanism of action at estrogen receptor of a new clinically relevant antiestrogen (GW7604) related to tamoxifen. Endocrinology 142:838–846[Abstract/Free Full Text]
318. Catherino WH, Wolf DM, Jordan VC 1995 A naturally occurring estrogen receptor mutation results in increased estrogenicity of a tamoxifen analog. Mol Endocrinol 9:1053–1063[Abstract/Free Full Text]
319. Levenson AS, Catherino WH, Jordan VC 1997 Estrogenic activity is increased for an antiestrogen by a natural mutation of the estrogen receptor. J Steroid Biochem Mol Biol 60:261–268[CrossRef][Medline]
320. Levenson AS, Jordan VC 1998 The key to the antiestrogenic mechanism of raloxifene is amino acid 351 (aspartate) in the estrogen receptor. Cancer Res 58:1872–1875[Abstract/Free Full Text]
321. Levenson AS, MacGregor Schafer JI, Bentrem DJ, Pease KM, Jordan VC 2001 Control of the estrogen-like actions of the tamoxifen-estrogen receptor complex by the surface amino acid at position 351. J Steroid Biochem Mol Biol 76:61–70[CrossRef][Medline]
322. MacGregor Schafer J, Liu H, Bentrem DJ, Zapf JW, Jordan VC 2000 Allosteric silencing of activating function 1 in the 4-hydroxytamoxifen estrogen receptor complex is induced by substituting glycine for aspartate at amino acid 351. Cancer Res 60:5097–5105[Abstract/Free Full Text]
323. Schafer JI, Liu H, Tonetti DA, Jordan VC 1999 The interaction of raloxifene and the active metabolite of the antiestrogen EM-800 (SC 5705) with the human estrogen receptor. Cancer Res 59:4308–4313[Abstract/Free Full Text]
324. Yamamoto Y, Wada O, Suzawa M, Yogiashi Y, Yano T, Kato S, Yanagisawa J 2001 The tamoxifen-responsive estrogen receptor mutant D351Y shows reduced tamoxifen-dependent interaction with corepressor complexes. J Biol Chem 276:42684–42691[Abstract/Free Full Text]
325. Anghel SI, Perly V, Melancon G, Barsalou A, Chagnon S, Rosenauer A, Miller Jr WH, Mader S 2000 Aspartate 351 of estrogen receptor is not crucial for the antagonist activity of antiestrogens. J Biol Chem 275:20867–20872[Abstract/Free Full Text]
326. Webb P, Nguyen P, Valentine C, Weatherman RV, Scanlan TS, Kushner PJ 2000 An antiestrogen-responsive estrogen receptor- mutant (D351Y) shows weak AF-2 activity in the presence of tamoxifen. J Biol Chem 275:37552–37558[Abstract/Free Full Text]
327. Jiang SY, Parker CJ, Jordan VC 1993 A model to describe how a point mutation of the estrogen receptor alters the structure-function relationship of antiestrogens. Breast Cancer Res Treat 26:139–147[CrossRef][Medline]
328. Jiang SY, Langan-Fahey SM, Stella AL, McCague R, Jordan VC 1992 Point mutation of estrogen receptor (ER) in the ligand-binding domain changes the pharmacology of antiestrogens in ER-negative breast cancer cells stably expressing complementary DNAs for ER. Mol Endocrinol 6:2167–2174[Abstract/Free Full Text]
329. Tora L, Mullick A, Metzger D, Ponglikitmongkol M, Park I, Chambon P 1989 The cloned human oestrogen receptor contains a mutation which alters its hormone binding properties. EMBO J 8:1981–1986[Medline]
330. Smith CL, Conneely OM, O’Malley BW 1993 Modulation of the ligand-independent activation of the human estrogen receptor by hormone and antihormone. Proc Natl Acad Sci USA 90:6120–6124[Abstract/Free Full Text]
331. Aumais JP, Lee HS, Lin R, White JH 1997 Selective interaction of hsp90 with an estrogen receptor ligand-binding domain containing a point mutation. J Biol Chem 272:12229–12235[Abstract/Free Full Text]
332. Metzger D, Berry M, Ali S, Chambon P 1995 Effect of antagonists on DNA binding properties of the human estrogen receptor in vitro and in vivo. Mol Endocrinol 9:579–591[Abstract/Free Full Text]
333. Reese JC, Wooge CH, Katzenellenbogen BS 1992 Identification of two cysteines closely positioned in the ligand-binding pocket of the human estrogen receptor: roles in ligand binding and transcriptional activation. Mol Endocrinol 6:2160–2166[Abstract/Free Full Text]
334. Neff S, Sadowski C, Miksicek RJ 1994 Mutational analysis of cysteine residues within the hormone-binding domain of the human estrogen receptor identifies mutants that are defective in both DNA-binding and subcellular distribution. Mol Endocrinol 8:1215–1223[Abstract/Free Full Text]
335. Reese JC, Katzenellenbogen BS 1991 Mutagenesis of cysteines in the hormone binding domain of the human estrogen receptor. Alterations in binding and transcriptional activation by covalently and reversibly attaching ligands. J Biol Chem 266:10880–10887[Abstract/Free Full Text]
336. Ekena K, Weis KE, Katzenellenbogen JA, Katzenellenbogen BS 1996 Identification of amino acids in the hormone binding domain of the human estrogen receptor important in estrogen binding. J Biol Chem 271:20053–20059[Abstract/Free Full Text]
337. Ekena K, Weis KE, Katzenellenbogen JA, Katzenellenbogen BS 1997 Different residues of the human estrogen receptor are involved in the recognition of structurally diverse estrogens and antiestrogens. J Biol Chem 272:5069–5075[Abstract/Free Full Text]
338. Aliau S, Mattras H, Richard E, Borgna JL 1999 Cysteine 530 of the human estrogen receptor is the main covalent attachment site of 11ß-(aziridinylalkoxyphenyl)estradiols. Biochemistry 38:14752–14762[CrossRef][Medline]
339. Aliau S, El Garrouj D, Yasri A, Katzenellenbogen BS, Borgna JL 1997 17 (haloacetamidoalkyl) estradiols alkylate the human estrogen receptor at cysteine residues 417 and 530. Biochemistry 36:5861–5867[CrossRef][Medline]
340. Carlson KE, Choi I, Gee A, Katzenellenbogen BS, Katzenellenbogen JA 1997 Altered ligand binding properties and enhanced stability of a constitutively active estrogen receptor: evidence that an open pocket conformation is required for ligand interaction. Biochemistry 36:14897–14905[CrossRef][Medline]
341. Zhong L, Skafar DF 2002 Mutations of tyrosine 537 in the human estrogen receptor- selectively alter the receptor’s affinity for estradiol and the kinetics of the interaction. Biochemistry 41:4209–4217[CrossRef][Medline]
342. Tremblay GB, Tremblay A, Labrie F, Giguere V 1998 Ligand-independent activation of the estrogen receptors and ß by mutations of a conserved tyrosine can be abolished by antiestrogens. Cancer Res 58:877–881[Abstract/Free Full Text]
343. Skafar DF 2000 Formation of a powerful capping motif corresponding to start of "helix 12" in agonist-bound estrogen receptor- contributes to increased constitutive activity of the protein. Cell Biochem Biophys 33:53–62[CrossRef][Medline]
344. Arnold SF, Melamed M, Vorojeikina DP, Notides AC, Sasson S 1997 Estradiol-binding mechanism and binding capacity of the human estrogen receptor is regulated by tyrosine phosphorylation. Mol Endocrinol 11:48–53[Abstract/Free Full Text]
345. Arnold SF, Vorojeikina DP, Notides AC 1995 Phosphorylation of tyrosine 537 on the human estrogen receptor is required for binding to an estrogen response element. J Biol Chem 270:30205–30212[Abstract/Free Full Text]
346. Yudt MR, Vorojeikina D, Zhong L, Skafar DF, Sasson S, Gasiewicz TA, Notides AC 1999 Function of estrogen receptor tyrosine 537 in hormone binding, DNA binding, and transactivation. Biochemistry 38:14146–14156[CrossRef][Medline]
347. Ince BA, Zhuang Y, Wrenn CK, Shapiro DJ, Katzenellenbogen BS 1993 Powerful dominant negative mutants of the human estrogen receptor. J Biol Chem 268:14026–14032[Abstract/Free Full Text]
348. Montano MM, Ekena K, Krueger KD, Keller AL, Katzenellenbogen BS 1996 Human estrogen receptor ligand activity inversion mutants: receptors that interpret antiestrogens as estrogens and estrogens as antiestrogens and discriminate among different antiestrogens. Mol Endocrinol 10:230–242[Abstract/Free Full Text]
349. Ince BA, Schodin DJ, Shapiro DJ, Katzenellenbogen BS 1995 Repression of endogenous estrogen receptor activity in MCF-7 human breast cancer cells by dominant negative estrogen receptors. Endocrinology 136:3194–3199[Abstract]
350. Lee EJ, Jakacka M, Duan WR, Chien PY, Martinson F, Gehm BD, Jameson JL 2001 Adenovirus-directed expression of dominant negative estrogen receptor induces apoptosis in breast cancer cells and regression of tumors in nude mice. Mol Med 7:773–782[Medline]
351. Schodin DJ, Zhuang Y, Shapiro DJ, Katzenellenbogen BS 1995 Analysis of mechanisms that determine dominant negative estrogen receptor effectiveness. J Biol Chem 270:31163–31171[Abstract/Free Full Text]
352. Hirata S, Shoda T, Kato J, Hoshi K 2001 The multiple untranslated first exons system of the human estrogen receptor ß (ER ß) gene. J Steroid Biochem Mol Biol 78:33–40[CrossRef][Medline]
353. Ogawa S, Inoue S, Watanabe T, Orimo A, Hosoi T, Ouchi Y, Muramatsu M 1998 Molecular cloning and characterization of human estrogen receptor ßcx: a potential inhibitor of estrogen action in human. Nucleic Acids Res 26:3505–3512[Abstract/Free Full Text]
354. Omoto Y, Eguchi H, Yamamoto-Yamaguchi Y, Hayashi S 2003 Estrogen receptor (ER) ß1 and ERßcx/ß2 inhibit ER function differently in breast cancer cell line MCF7. Oncogene 22:5011–5020[CrossRef][Medline]
355. Peng B, Lu B, Leygue E, Murphy LC 2003 Putative functional characteristics of human estrogen receptor-ß isoforms. J Mol Endocrinol 30:13–29[Abstract]
356. Saji S, Omoto Y, Shimizu C, Warner M, Hayashi Y, Horiguchi S, Watanabe T, Hayashi S, Gustafsson JA, Toi M 2002 Expression of estrogen receptor (ER) (ß)cx protein in ER()-positive breast cancer: specific correlation with progesterone receptor. Cancer Res 62:4849–4853[Abstract/Free Full Text]
357. Saji S, Omoto Y, Shimizu C, Horiguchi S, Watanabe T, Funata N, Hayash S, Gustafsson JA, Toi M 2002 Clinical impact of assay of estrogen receptor ß cx in breast cancer. Breast Cancer 9:303–307[Medline]
358. Poola I, Abraham J, Baldwin K 2002 Identification of ten exon deleted ERß mRNAs in human ovary, breast, uterus and bone tissues: alternate splicing pattern of estrogen receptor ß mRNA is distinct from that of estrogen receptor . FEBS Lett 516:133–138[CrossRef][Medline]
359. Poola I, Abraham J, Liu A 2002 Estrogen receptor ß splice variant mRNAs are differentially altered during breast carcinogenesis. J Steroid Biochem Mol Biol 82:169–179[CrossRef][Medline]
360. Bjornstrom L, Sjoberg M 2002 Mutations in the estrogen receptor DNA-binding domain discriminate between the classical mechanism of action and cross-talk with Stat5b and activating protein 1 (AP-1). J Biol Chem 277:48479–48483[Abstract/Free Full Text]
361. Vladusic EA, Hornby AE, Guerra-Vladusic FK, Lupu R 1998 Expression of estrogen receptor ß messenger RNA variant in breast cancer. Cancer Res 58:210–214[Abstract/Free Full Text]
362. Lu B, Leygue E, Dotzlaw H, Murphy LJ, Murphy LC, Watson PH 1998 Estrogen receptor-ß mRNA variants in human and murine tissues. Mol Cell Endocrinol 138:199–203[CrossRef][Medline]
363. Rosenkranz K, Hinney A, Ziegler A, Hermann H, Fichter M, Mayer H, Siegfried W, Young JK, Remschmidt H, Hebebrand J 1998 Systematic mutation screening of the estrogen receptor ß gene in probands of different weight extremes: identification of several genetic variants. J Clin Endocrinol Metab 83:4524–4527[Abstract/Free Full Text]
364. Arko B, Prezelj J, Komel R, Kocijancic A, Marc J 2002 No major effect of estrogen receptor ß gene RsaI polymorphism on bone mineral density and response to alendronate therapy in postmenopausal osteoporosis. J Steroid Biochem Mol Biol 81:147–152[CrossRef][Medline]
365. Murphy LC, Dotzlaw H, Leygue E, Coutts A, Watson P 1998 The pathophysiological role of estrogen receptor variants in human breast cancer. J Steroid Biochem Mol Biol 65:175–180[CrossRef][Medline]
366. Fuqua S, Hopp T, Van M, Osborne CK, O’Connell P, Allred DC, An estrogen receptor a mutation that predicts metastatic breast cancer clinical behavior. 9th SPORE Investigators Workshop, 2001, p 174
367. Poola I, Clarke R, DeWitty R, Leffall LD 2002 Functionally active estrogen receptor isoform profiles in the breast tumors of African American women are different from the profiles in breast tumors of Caucasian women. Cancer 94:615–623[CrossRef][Medline]
368. Jazaeri O, Shupnik MA, Jazaeri AA, Rice LW 1999 Expression of estrogen receptor mRNA and protein variants in human endometrial carcinoma. Gynecol Oncol 74:38–47[CrossRef][Medline]
369. Hu C, Hyder SM, Needleman DS, Baker VV 1996 Expression of estrogen receptor variants in normal and neoplastic human uterus. Mol Cell Endocrinol 118:173–179[CrossRef][Medline]
370. Omoto Y, Iwase H, Iwata H, Hara Y, Toyama T, Ando Y, Kobayashi S 2000 Expression of estrogen receptor exon 5 and 7 deletion variant in human breast cancers. Breast Cancer 7:27–31[Medline]
371. Leslie KK, Tasset DM, Horwitz KB 1992 Functional analysis of a mutant estrogen receptor isolated from T47Dco breast cancer cells. Am J Obstet Gynecol 166:1053–1061[Medline]
372. Lau KM, Mok SC, Ho SM 1999 Expression of human estrogen receptor- and -ß, progesterone receptor, and androgen receptor mRNA in normal and malignant ovarian epithelial cells. Proc Natl Acad Sci USA 96:5722–5727[Abstract/Free Full Text]
373. Feng J, Yan J, Michaud S, Craddock N, Jones IR, Cook Jr EH, Goldman D, Heston LL, Peltonen L, Delisi LE, Sommer SS 2001 Scanning of estrogen receptor (ER) and thyroid hormone receptor (TR) genes in patients with psychiatric diseases: four missense mutations identified in ER gene. Am J Med Genet 105:369–374[CrossRef][Medline]
374. Smith EP, Boyd J, Frank GR, Takahashi H, Cohen RM, Specker B, Williams TC, Lubahn DB, Korach KS 1994 Estrogen resistance caused by a mutation in the estrogen-receptor gene in a man. N Engl J Med 331:1056–1061[Abstract/Free Full Text]
375. Zelada-Hedman M, Borresen-Dale AL, Lindblom A 1997 Screening of 229 family cancer patients for a germline estrogen receptor gene (ESR) base mutation. Hum Mutat 9:289[CrossRef][Medline]
376. England GM, Bilimoria MM, Chen Z, Assikis VJ, Muenzner HD, Jordan VC 1998 Characterization of a point mutation in the hormone binding domain of the estrogen receptor from a breast tumor. Int J Oncol 12:981–986[Medline]
377. Schlegel A, Wang C, Katzenellenbogen BS, Pestell RG, Lisanti MP 1999 Caveolin-1 potentiates estrogen receptor (ER) signaling. Caveolin-1 drives ligand-independent nuclear translocation and activation of ER. J Biol Chem 274:33551–33556[Abstract/Free Full Text]
378. Clark DE, Poteet-Smith CE, Smith JA, Lannigan DA 2001 Rsk2 allosterically activates estrogen receptor by docking to the hormone-binding domain. EMBO J 20:3484–3494[CrossRef][Medline]
379. Sun M, Paciga JE, Feldman RI, Yuan Z, Coppola D, Lu YY, Shelley SA, Nicosia SV, Cheng JQ 2001 Phosphatidylinositol-3-OH kinase (PI3K)/AKT2, activated in breast cancer, regulates and is induced by estrogen receptor (ER) via interaction between ER and PI3K. Cancer Res 61:5985–5991[Abstract/Free Full Text]
380. Mishra SK, Mazumdar A, Vadlamudi RK, Li F, Wang RA, Yu W, Jordan VC, Santen RJ, Kumar R 2003 MICoA, a novel metastasis-associated protein 1 (MTA1) interacting protein coactivator, regulates estrogen receptor- transactivation functions. J Biol Chem 278:19209–19219[Abstract/Free Full Text]
381. Wang RA, Mazumdar A, Vadlamudi RK, Kumar R 2002 P21-activated kinase-1 phosphorylates and transactivates estrogen receptor- and promotes hyperplasia in mammary epithelium. EMBO J 21:5437–5447[CrossRef][Medline]
382. Lee H, Bai W 2002 Regulation of estrogen receptor nuclear export by ligand-induced and p38-mediated receptor phosphorylation. Mol Cell Biol 22:5835–5845[Abstract/Free Full Text]
383. Ekena K, Katzenellenbogen JA, Katzenellenbogen BS 1998 Determinants of ligand specificity of estrogen receptor-: estrogen versus androgen discrimination. J Biol Chem 273:693–699[Abstract/Free Full Text]
384. Chen S, Zhou D, Yang C, Sherman M 2001 Molecular basis for the constitutive activity of estrogen-related receptor -1. J Biol Chem 276:28465–28470[Abstract/Free Full Text]
385. Schreurs RH, Quaedackers ME, Seinen W, van der Burg B 2002 Transcriptional activation of estrogen receptor ER and ERß by polycyclic musks is cell type dependent. Toxicol Appl Pharmacol 183:1–9[CrossRef][Medline]
386. Webb P, Nguyen P, Kushner PJ 2003 Differential SERM effects on corepressor binding dictate ER activity in vivo. J Biol Chem 278:6912–6920[Abstract/Free Full Text]
387. McInerney EM, Ince BA, Shapiro DJ, Katzenellenbogen BS 1996 A transcriptionally active estrogen receptor mutant is a novel type of dominant negative inhibitor of estrogen action. Mol Endocrinol 10:1519–1526[Abstract/Free Full Text]
388. Reese JC, Katzenellenbogen BS 1992 Examination of the DNA-binding ability of estrogen receptor in whole cells: implications for hormone-independent transactivation and the actions of antiestrogens. Mol Cell Biol 12:4531–4538[Abstract/Free Full Text]
389. Stoica A, Katzenellenbogen BS, Martin MB 2000 Activation of estrogen receptor- by the heavy metal cadmium. Mol Endocrinol 14:545–553[Abstract/Free Full Text]
390. Stoica A, Pentecost E, Martin MB 2000 Effects of arsenite on estrogen receptor- expression and activity in MCF-7 breast cancer cells. Endocrinology 141:3595–3602[Abstract/Free Full Text]
391. Stoica A, Pentecost E, Martin MB 2000 Effects of selenite on estrogen receptor- expression and activity in MCF-7 breast cancer cells. J Cell Biochem 79:282–292[CrossRef][Medline]
392. Bush SM, Folta S, Lannigan DA 1996 Use of the yeast one-hybrid system to screen for mutations in the ligand-binding domain of the estrogen receptor. Steroids 61:102–109[CrossRef][Medline]
393. Eng FC, Lee HS, Ferrara J, Willson TM, White JH 1997 Probing the structure and function of the estrogen receptor ligand binding domain by analysis of mutants with altered transactivation characteristics. Mol Cell Biol 17:4644–4653[Abstract]
394. Rosenauer A, Nervi C, Davison K, Lamph WW, Mader S, Miller Jr WH 1998 Estrogen receptor expression activates the transcriptional and growth-inhibitory response to retinoids without enhanced retinoic acid receptor expression. Cancer Res 58:5110–5116[Abstract/Free Full Text]
395. Jiang SY, Jordan VC 1992 Growth regulation of estrogen receptor-negative breast cancer cells transfected with complementary DNAs for estrogen receptor. J Natl Cancer Inst 84:580–591[Abstract/Free Full Text]
396. Aliau S, Mattras H, Richard E, Bonnafous JC, Borgna JL 2002 Differential interactions of estrogens and antiestrogens at the 17 ß-hydroxyl or counterpart hydroxyl with histidine 524 of the human estrogen receptor . Biochemistry 41:7979–7988[CrossRef][Medline]
397. Preisler-Mashek MT, Solodin N, Stark BL, Tyriver MK, Alarid ET 2002 Ligand-specific regulation of proteasome-mediated proteolysis of estrogen receptor-. Am J Physiol Endocrinol Metab 282:E891—E898
398. Whelan J, Miller N 1996 Generation of estrogen receptor mutants with altered ligand specificity for use in establishing a regulatable gene expression system. J Steroid Biochem Mol Biol 58:3–12[CrossRef][Medline]
399. Scarlata S, Miksicek R 1995 Binding properties of coumestrol to expressed human estrogen receptor. Mol Cell Endocrinol 115:65–72[CrossRef][Medline]
400. Zhao C, Koide A, Abrams J, Deighton-Collins S, Martinez A, Schwartz JA, Koide S, Skafar DF 2003 Mutation of Leu-536 in human estrogen receptor- alters the coupling between ligand binding, transcription activation, and receptor conformation. J Biol Chem 278:27278–27286[Abstract/Free Full Text]
401. Eng FC, Barsalou A, Akutsu N, Mercier I, Zechel C, Mader S, White JH 1998 Different classes of coactivators recognize distinct but overlapping binding sites on the estrogen receptor ligand binding domain. J Biol Chem 273:28371–28377[Abstract/Free Full Text]
402. Pearce ST, Liu H, Jordan VC 2003 Modulation of estrogen receptor function and stability by tamoxifen and a critical amino acid (Asp-538) in helix 12. J Biol Chem 278:7630–7638[Abstract/Free Full Text]
403. Saville B, Poukka H, Wormke M, Janne OA, Palvimo JJ, Stoner M, Samudio I, Safe S 2002 Cooperative coactivation of estrogen receptor in ZR-75 human breast cancer cells by SNURF and TATA-binding protein. J Biol Chem 277:2485–2497[Abstract/Free Full Text]
404. Webb P, Nguyen P, Shinsako J, Anderson C, Feng W, Nguyen MP, Chen D, Huang SM, Subramanian S, McKinerney E, Katzenellenbogen BS, Stallcup MR, Kushner PJ 1998 Estrogen receptor activation function 1 works by binding p160 coactivator proteins. Mol Endocrinol 12:1605–1618[Abstract/Free Full Text]
405. Kraus WL, Weis KE, Katzenellenbogen BS 1995 Inhibitory cross-talk between steroid hormone receptors: differential targeting of estrogen receptor in the repression of its transcriptional activity by agonist- and antagonist-occupied progestin receptors. Mol Cell Biol 15:1847–1857[Abstract]
406. Kato K, Horiuchi S, Takahashi A, Ueoka Y, Arima T, Matsuda T, Kato H, Nishida Ji J, Nakabeppu Y, Wake N 2002 Contribution of estrogen receptor to oncogenic K-Ras-mediated NIH3T3 cell transformation and its implication for escape from senescence by modulating the p53 pathway. J Biol Chem 277:11217–11224[Abstract/Free Full Text]
407. Fujimoto J, Sun WS, Misao R, Sakaguchi H, Aoki I, Toyoki H, Tamaya T 2003 Expression of estrogen receptor ß exon-deleted variant mRNAs in ovary and uterine endometrium. J Steroid Biochem Mol Biol 84:133–140[CrossRef][Medline]

This article has been cited by other articles:

				V. Stanisic, A. Malovannaya, J. Qin, D. M. Lonard, and B. W. O'Malley OTU Domain-containing Ubiquitin Aldehyde-binding Protein 1 (OTUB1) Deubiquitinates Estrogen Receptor (ER) {alpha} and Affects ER{alpha} Transcriptional Activity J. Biol. Chem., June 12, 2009; 284(24): 16135 - 16145. [Abstract] [Full Text] [PDF]

				Y. Wang, H. Zong, Y. Chi, Y. Hong, Y. Yang, W. Zou, X. Yun, and J. Gu Repression of Estrogen Receptor alpha by CDK11p58 Through Promoting its Ubiquitin-Proteasome Degradation J. Biochem., March 1, 2009; 145(3): 331 - 343. [Abstract] [Full Text] [PDF]

				O. I. Olopade, T. A. Grushko, R. Nanda, and D. Huo Advances in Breast Cancer: Pathways to Personalized Medicine Clin. Cancer Res., December 15, 2008; 14(24): 7988 - 7999. [Abstract] [Full Text] [PDF]

				S. A. Abdelmagid and C. K. L. Too Prolactin and Estrogen Up-Regulate Carboxypeptidase-D to Promote Nitric Oxide Production and Survival of MCF-7 Breast Cancer Cells Endocrinology, October 1, 2008; 149(10): 4821 - 4828. [Abstract] [Full Text] [PDF]

				E. M. Fox, T. M. Bernaciak, J. Wen, A. M. Weaver, M. A. Shupnik, and C. M. Silva Signal Transducer and Activator of Transcription 5b, c-Src, and Epidermal Growth Factor Receptor Signaling Play Integral Roles in Estrogen-Stimulated Proliferation of Estrogen Receptor-Positive Breast Cancer Cells Mol. Endocrinol., August 1, 2008; 22(8): 1781 - 1796. [Abstract] [Full Text] [PDF]

				N. Kondo, T. Toyama, H. Sugiura, Y. Fujii, and H. Yamashita miR-206 Expression Is Down-regulated in Estrogen Receptor {alpha}-Positive Human Breast Cancer Cancer Res., July 1, 2008; 68(13): 5004 - 5008. [Abstract] [Full Text] [PDF]

				N. B. Berry, M. Fan, and K. P. Nephew Estrogen Receptor-{alpha} Hinge-Region Lysines 302 and 303 Regulate Receptor Degradation by the Proteasome Mol. Endocrinol., July 1, 2008; 22(7): 1535 - 1551. [Abstract] [Full Text] [PDF]

				M. Maynadier, J.-M. Ramirez, A.-M. Cathiard, N. Platet, D. Gras, M. Gleizes, M. S. Sheikh, P. Nirde, and M. Garcia Unliganded estrogen receptor {alpha} inhibits breast cancer cell growth through interaction with a cyclin-dependent kinase inhibitor (p21WAF1) FASEB J, March 1, 2008; 22(3): 671 - 681. [Abstract] [Full Text] [PDF]

				S. Lopez-Tarruella and R. Schiff The Dynamics of Estrogen Receptor Status in Breast Cancer: Re-shaping the Paradigm Clin. Cancer Res., December 1, 2007; 13(23): 6921 - 6925. [Full Text] [PDF]

				C. M. Silva and M. A. Shupnik Integration of Steroid and Growth Factor Pathways in Breast Cancer: Focus on Signal Transducers and Activators of Transcription and Their Potential Role in Resistance Mol. Endocrinol., July 1, 2007; 21(7): 1499 - 1512. [Abstract] [Full Text] [PDF]

				O. Treeck, G. Pfeiler, D. Mitter, C. Lattrich, G. Piendl, and O. Ortmann Estrogen receptor {beta}1 exerts antitumoral effects on SK-OV-3 ovarian cancer cells J. Endocrinol., June 1, 2007; 193(3): 421 - 433. [Abstract] [Full Text] [PDF]

				M. H. Herynk, I. Parra, Y. Cui, A. Beyer, M.-F. Wu, S. G. Hilsenbeck, and S. A.W. Fuqua Association between the Estrogen Receptor {alpha} A908G Mutation and Outcomes in Invasive Breast Cancer Clin. Cancer Res., June 1, 2007; 13(11): 3235 - 3243. [Abstract] [Full Text] [PDF]

				J. S. Ross, W. F. Symmans, L. Pusztai, and G. N. Hortobagyi Standardizing Slide-Based Assays in Breast Cancer: Hormone Receptors, HER2, and Sentinel Lymph Nodes Clin. Cancer Res., May 15, 2007; 13(10): 2831 - 2835. [Abstract] [Full Text] [PDF]

				B. D. Adams, H. Furneaux, and B. A. White The Micro-Ribonucleic Acid (miRNA) miR-206 Targets the Human Estrogen Receptor-{alpha} (ER{alpha}) and Represses ER{alpha} Messenger RNA and Protein Expression in Breast Cancer Cell Lines Mol. Endocrinol., May 1, 2007; 21(5): 1132 - 1147. [Abstract] [Full Text] [PDF]

				P. Galluzzo, F. Caiazza, S. Moreno, and M. Marino Role of ER{beta} palmitoylation in the inhibition of human colon cancer cell proliferation Endocr. Relat. Cancer, March 1, 2007; 14(1): 153 - 167. [Abstract] [Full Text] [PDF]

				Y. Lu, A. Amleh, J. Sun, X. Jin, S. D. McCullough, R. Baer, D. Ren, R. Li, and Y. Hu Ubiquitination and Proteasome-Mediated Degradation of BRCA1 and BARD1 during Steroidogenesis in Human Ovarian Granulosa Cells Mol. Endocrinol., March 1, 2007; 21(3): 651 - 663. [Abstract] [Full Text] [PDF]

				M. H. Herynk, A. R. Beyer, Y. Cui, H. Weiss, E. Anderson, T. P. Green, and S. A.W. Fuqua Cooperative action of tamoxifen and c-Src inhibition in preventing the growth of estrogen receptor-positive human breast cancer cells Mol. Cancer Ther., December 1, 2006; 5(12): 3023 - 3031. [Abstract] [Full Text] [PDF]

				I. Shamovsky and E. Nudler Gene Control by Large Noncoding RNAs Sci. Signal., October 3, 2006; 2006(355): pe40 - pe40. [Abstract] [Full Text] [PDF]

				U. Ohnemus, M. Uenalan, J. Inzunza, J.-A. Gustafsson, and R. Paus The Hair Follicle as an Estrogen Target and Source Endocr. Rev., October 1, 2006; 27(6): 677 - 706. [Abstract] [Full Text] [PDF]

				D. Alvaro, B. Barbaro, A. Franchitto, P. Onori, S. S. Glaser, G. Alpini, H. Francis, L. Marucci, P. Sterpetti, S. Ginanni-Corradini, et al. Estrogens and Insulin-Like Growth Factor 1 Modulate Neoplastic Cell Growth in Human Cholangiocarcinoma Am. J. Pathol., September 1, 2006; 169(3): 877 - 888. [Abstract] [Full Text] [PDF]

				J. M. Garcia-Pedrero, E. Kiskinis, M. G. Parker, and B. Belandia The SWI/SNF Chromatin Remodeling Subunit BAF57 Is a Critical Regulator of Estrogen Receptor Function in Breast Cancer Cells J. Biol. Chem., August 11, 2006; 281(32): 22656 - 22664. [Abstract] [Full Text] [PDF]

				J. A Riancho, M. T Zarrabeitia, C. Valero, C. Sanudo, V. Mijares, and J. Gonzalez-Macias A gene-to-gene interaction between aromatase and estrogen receptors influences bone mineral density. Eur. J. Endocrinol., July 1, 2006; 155(1): 53 - 59. [Abstract] [Full Text] [PDF]

				R. J. Pietras Biologic Basis of Sequential and Combination Therapies for Hormone-Responsive Breast Cancer Oncologist, July 1, 2006; 11(7): 704 - 717. [Abstract] [Full Text] [PDF]

				X. Long and K. P. Nephew Fulvestrant (ICI 182,780)-dependent Interacting Proteins Mediate Immobilization and Degradation of Estrogen Receptor-{alpha} J. Biol. Chem., April 7, 2006; 281(14): 9607 - 9615. [Abstract] [Full Text] [PDF]

				N. Normanno, M. Di Maio, E. De Maio, A. De Luca, A. de Matteis, A. Giordano, F. Perrone, and on behalf of the NCI-Naples Breast Cancer Group Mechanisms of endocrine resistance and novel therapeutic strategies in breast cancer Endocr. Relat. Cancer, December 1, 2005; 12(4): 721 - 747. [Abstract] [Full Text] [PDF]

				J. Huang, X. Li, C. A. Maguire, R. Hilf, R. A. Bambara, and M. Muyan Binding of Estrogen Receptor {beta} to Estrogen Response Element in Situ Is Independent of Estradiol and Impaired by Its Amino Terminus Mol. Endocrinol., November 1, 2005; 19(11): 2696 - 2712. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Herynk, M. H. Articles by Fuqua, S. A. W. Search for Related Content PubMed PubMed Citation Articles by Herynk, M. H. Articles by Fuqua, S. A. W.