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 Reprints, Permissions and Rights Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Risbridger, G. P. Articles by Robertson, D. M. Search for Related Content PubMed PubMed Citation Articles by Risbridger, G. P. Articles by Robertson, D. M.

Activins and Inhibins in Endocrine and Other Tumors

Centre for Urological Research, Institute of Reproduction and Development, Monash University (G.P.R., J.F.S.), Melbourne, Prince Henry’s Institute of Medical Research (D.M.R.), Clayton, Victoria 3168, Australia

Correspondence: Address all correspondence and requests for reprints to: Dr. Gail P. Risbridger, Associate Professor, Director, Center for Urological Research, Monash Institute of Reproduction and Development, Monash Medical Center, 246 Clayton Road, Clayton, Victoria 3168, Australia. E-mail: gail.risbridger{at}med.monash.edu.au

	Abstract

Top Abstract I. Introduction II. Activin and Inhibin:... III. Activin and Inhibin... IV. Endocrine and Other... V. Summary References

 
Inhibin and activin are members of the TGFß superfamily of growth and differentiation factors. They were first identified as gonadal-derived regulators of pituitary FSH and were subsequently assigned multiple actions in a wide range of tissues. More recently, the inhibin subunit was considered as a tumor suppressor based on functional studies employing transgenic mouse models. This review evaluates the functional and molecular evidence that the inhibin subunit is a tumor suppressor in endocrine cancers. The evaluation highlights the discrepant results from the human and mouse studies, as well as the differences between endocrine tumor types. In addition, we examine the evidence that the activin-signaling pathway is tumor suppressive and identify organ-specific differences in the actions and putative roles of this pathway in endocrine tumors. In summary, there is a considerable body of evidence to support the role of inhibins and activins in endocrine-related tumors. Future studies will define the mechanisms by which inhibins and activins contribute to the process of initiation, promotion, or progression of endocrine-related cancers.

I. Introduction

II. Activin and Inhibin: Members of the TGFß Superfamily

A. Activin receptors and signaling

B. Inhibin receptors and signaling

C. Binding proteins

D. Functional activities of inhibin and activin

III. Activin and Inhibin in Tumors

A. Functional evidence for a role of activin and inhibin in tumors

B. Molecular genetics of activin and inhibin gene loci

IV. Endocrine and Other Tumors

A. Ovarian tumors

B. Prostate tumors

C. Testicular tumors

D. Breast tumors

E. Adrenal tumors

F. Pituitary tumors

G. Pancreatic tumors

H. Placental tumors

I. Endometrial tumors

J. Kidney tumors

K. Liver tumors

V. Summary

A. The process of tumorigenesis

B. Role of inhibin in tumorigenesis

C. Role of activin in tumorigenesis

D. Future directions

	I. Introduction

Top Abstract I. Introduction II. Activin and Inhibin:... III. Activin and Inhibin... IV. Endocrine and Other... V. Summary References

 
INHIBIN AND ACTIVIN subunits are present in numerous human tissues of both endocrine and nonendocrine organs. The dimeric proteins formed from the subunits are members of the TGFß superfamily of growth and differentiation factors and were isolated and characterized as gonadal-derived regulators of FSH synthesis and secretion. Inhibins are dimers of an subunit and either a ß_A or ß_B subunit, whereas activins are homo- or heterodimers of the ß_A or ß_B subunits. To add to the complexity of this subgroup, three additional activin ß subunit proteins were described, and there is a growing family of activin and inhibin binding proteins, receptors, and signaling molecules.

Since the first description of these proteins as regulators of FSH, multiple actions were assigned to them in a variety of tissues. In addition, the role of the inhibin subunit gene as a tumor suppressor was investigated in mouse models. Measurement of inhibin is used clinically to detect and monitor human ovarian tumors. The aim of this review is to evaluate the evidence suggesting that the inhibin subunit gene is tumor suppressive. The contribution of activin and its signaling pathway to malignant progression is also evaluated. Evidence from transgenic mouse models is presented, together with a summary of the genetic mutations in human cancers that involve the chromosomes on which the activin and inhibin subunit genes reside. The literature reporting the detection, action, and role of activin and inhibin in endocrine tumorigenesis, including the prostate and gonads, is reported. The conclusion from this review is that there is a substantial body of evidence to support the hypothesis that both inhibin and activin contribute to tumorigenesis.

	II. Activin and Inhibin: Members of the TGFß Superfamily

Top Abstract I. Introduction II. Activin and Inhibin:... III. Activin and Inhibin... IV. Endocrine and Other... V. Summary References

 
Inhibin and activin are members of the TGFß superfamily of growth factors, which includes bone morphogenetic proteins (BMPs) and Müllerian inhibitory substance. Currently, over 45 members of this family have been identified (1, 2). Structural similarities between inhibin, activin, and other members of the TGFß superfamily are based on the conservation of the cysteine spacing within each subunit and the disulphide linkages between two subunits that form the characteristic cysteine knots. Other similarities relate to dimer formation, the location of the bioactive peptide in the carboxyl-terminal region of the precursor molecule, and the similarities in their intracellular signaling mechanisms (3, 4).

Inhibin consists of two partially homologous disulfide-linked subunits ( and ß_A or ß_B, thus inhibin A and B), whereas activin is a dimer of disulfide-linked ß subunits (activin A, B, AB). Another subset of activin ß subunits (ß_C, ß_D, and ß_E subunits) were identified, based on their homology to the ß_A and ß_B subunits (5, 6, 7, 8, 9). The ß_C subunit dimerizes with itself and the ß_A and ß_B subunits in vitro to form activin C, AC, and AB (10). The formation of inhibin C (ß_C dimers) requires both cellular colocalization and dimerization of and ß_C subunits, but in vitro studies have shown that the ß_C subunit does not dimerize with the subunit (10). Activin ß_D (6) and ß_E (9) subunits were isolated from Xenopus and mouse cDNA libraries, respectively. The activin ß_E subunit shows close similarity to the activin ß_C subunit in terms of genomic organization and chromosomal localization, amino acid sequence identity, and tissue expression patterns (8, 9). In addition to the structural similarities, a common in vitro bioactivity, namely mesoderm induction, was identified (6), although mice bearing functional deletion of the activin ß_C and/or ß_E subunit genes did not show developmental defects and were phenotypically normal (11).

Inhibin and activin were originally isolated from follicular fluid as a range of molecular weight forms, consisting of variously processed precursor forms (12). The and ß inhibin and activin subunits are synthesized as full-length precursor proteins. The inhibin subunit precursor protein consists of three regions, Pro, _N, and _C, whereas the activin ß subunit precursors consist of two regions, Proß and ß. Proteolytic cleavage at dibasic or polybasic proteolytic cleavage sites occurs intracellularly as well as in serum (13, 14).

Studies in which the proteolytic cleavage sites in both and ß_A subunits were modified by site-directed mutagenesis showed that the full-length inhibin or activin dimers were inactive in a pituitary cell bioassay, whereas the truncated dimers were bioactive (15). Intermediate processed forms of the precursor or ß_A subunits showed some activity. In vitro studies demonstrated that high molecular weight forms of inhibin present in serum were processed to 30-kDa inhibin (14). Activin A was present in serum as the mature 25-kDa dimeric form (16).

Sensitive immunoassays are now available for detecting all subunit-containing forms of inhibin, including Pro-C, as well as dimeric inhibin A, inhibin B, and activin A, in serum (17, 18, 19, 20). These assays have been used to explore the role of inhibin and activin in normal physiological processes and in endocrine diseases (see Section IV). Immunoassays for examining activins B–E in serum or tissue are not currently available.

A. Activin receptors and signaling
At the cell surface, activin ligands interact with a dual receptor system involving a family of transmembrane serine/threonine kinase receptors classed as type I or type II receptors (Fig. 1 and Ref. 21). Activin binding to the type II receptor (ActRII) leads to the recruitment of the type I receptor (ActRI) and the formation of a heteromeric complex. Formation of this complex induces phosphorylation of the ActRI, which leads to activation of the receptor-regulated Smad [R-Smad (22, 23, 24, 25)]. R-Smads are ligand specific, with Smad2 and Smad3 mediating activin and TGFß signaling, and Smad1, -5, and -8 mediating BMP signaling (22). The interaction between the R-Smads and the receptor complex involves a membrane-bound protein named Smad anchor for receptor activation [SARA (26)]. After phosphorylation, the R-Smads are released and form heteromeric complexes with the Co-Smad, Smad4. The R-Smad and Co-Smad complex then translocates to the nucleus to regulate gene expression. A third class of Smads, the inhibitory Smads (Smad6 and Smad7), can antagonize the signaling events described above and can prevent access and phosphorylation of the R-Smads or interfere with the formation of the R-Smad/Smad4 complexes (2, 27, 28).

View larger version (43K): [in this window] [in a new window]   Figure 1. Activin and inhibin signaling pathways. The binding of activin ligand (ßß) to the type II receptor (II) initiates the activin signaling pathway and leads to recruitment of the type I receptor (I). SARA brings Smad2 into position, and phosphorylation of Smad2 by the activin/receptor complex liberates it from SARA. Smad2 recruits Smad4 and the complex locates to the nucleus, where it binds FAST/FoxH and other transcription factors to regulate the transcription of activin responsive genes. Inhibin potentially interferes with activin signaling by forming complexes with the activin receptors; the low affinity of inhibin for ActRII is enhanced by binding to betaglycan (BG). This complex does not activate a known signal cascade. It was suggested that binding of inhibin to the inhibin receptor (InhBP) leads to recruitment of the activin type I receptor. This complex may be responsible for initiation of a unique inhibin response.

B. Inhibin receptors and signaling
The mechanism of inhibin action is still controversial, and the downstream signaling proteins in the inhibin signal transduction cascade are not as well characterized as those for activin. Although it was suggested that inhibin signals through its own receptor (33, 34), the identity of specific cell surface receptors for inhibin has been difficult to demonstrate. It was proposed that inhibin antagonized the action of activin through a dominant-negative mechanism involving the binding of inhibin to the activin receptor (35, 36). Betaglycan, a type III receptor for TGF-ß, binds inhibin with high affinity and specificity, and together with ActRIIA can enhance the cell-membrane binding of inhibin (37). Theoretically, the binding of inhibin and betaglycan can block the effects of activin via its receptor (Fig. 1). More recently, Chong et al. (38) isolated another inhibin binding protein (InhBP or p120), which is expressed in the pituitary and testis. A key question to resolve from all these studies is whether or not betaglycan, InhBP, and ActRIIs are physiological receptors for inhibin. If this is the case, and if a cell expresses all of these proteins, there are three predictable outcomes or responses. First, activin binding to its receptor initiates activin signaling events leading to a biological response specific for activins. Secondly, inhibin binds to either the activin receptor or to betaglycan and blocks the activin response by generating a nonfunctional receptor complex. Thirdly, inhibin binds to InhBP and activates an inhibin transduction pathway, which elicits a response specific for inhibin ligands (39, 40). However, the evidence to support these predictions remains to be determined.

C. Binding proteins
The activin binding protein, follistatin, is a key inhibitor of activin action and is the subject of previous reviews (4, 41, 42). Essentially, follistatin was isolated on the basis of its inhibin-like ability to suppress FSH activity in vitro. This inhibitory activity was subsequently shown to be due to its ability to bind and neutralize activin with high affinity. Follistatin is structurally dissimilar to members of the TGFß family. It is a product of a single gene forming a series of molecular weight forms by alternate splicing of the mRNA. The 288-amino acid and 315-amino acid forms of follistatin are the most common. Follistatin has structural homology with epidermal growth factor and a group of enzyme inhibitors of the Kazal family, which include secreted protein, acidic and rich in cysteine (SPARC), SC1/hevin, QR1, agrin, testican, and tsc36/FRP. These proteins contain a distinctive, follistatin-like, 10-Cys-containing module followed by an extracellular calcium binding domain. Follistatin prevented the mesoderm-inducing activity of activin in Xenopus, and by blocking activin signaling via activin receptors, follistatin induced neural differentiation (43). Follistatin also neutralized the mesoderm-regulating activities of other cytokines of the TGFß superfamily (BMP-2, BMP-4, and BMP-7) that bind follistatin (43).

More recently, a novel follistatin-like protein (FSLP) with two, rather than three, follistatin domains was identified in the mouse (44). Follistatin-like protein binds activin and BMPs with high affinity and is expressed in a similar range of tissues, including liver and testis, to follistatin. Its biological role has not yet been determined.

Several other binding proteins were identified that may also influence inhibin and activin action. In addition to betaglycan and InhBP (discussed above), which bind inhibin with high affinity but not activin, ₂ macroglobulin forms high molecular weight complexes with inhibin and activin (45). However, no influence on the in vitro activities of either inhibin or activin was reported, and its potential role in vivo is not established.

D. Functional activities of inhibin and activin
Inhibin was originally isolated based on its ability to suppress FSH production and secretion by rat pituitary cells in vitro. FSH regulation appeared to be major biological role for inhibin, although at high concentrations, inhibin antagonized the actions of activin. Activin, in contrast, has a range of activities and is involved in bone growth, mesoderm induction in Xenopus laevis embryos, reproduction through the regulation of pituitary FSH production, nerve cell survival, wound healing, and tissue differentiation in pancreas, kidney, and heart. In some instances, activin action opposes that of inhibin; for example, activin is a potent stimulator of FSH release, suggesting that inhibin may be an antagonist of activin. Within the ovary, FSH in combination with activin caused a dose-related increase in DNA synthesis, suggesting that FSH in the presence of activin is mitogenic (46, 47).

It is generally considered that inhibin is an endocrine factor with a primary function of regulating FSH. Conversely, activin is believed to have local effects as a paracrine and/or autocrine factor (48). For further details on actions of inhibin and activin, the reader is referred to various reviews (3, 4).

	III. Activin and Inhibin in Tumors

Top Abstract I. Introduction II. Activin and Inhibin:... III. Activin and Inhibin... IV. Endocrine and Other... V. Summary References

 
A. Functional evidence for a role of activin and inhibin in tumors
Matzuk et al. (49) made a significant contribution to our understanding of the role of activin and inhibin in cancer by reporting that the inhibin subunit is a tumor suppressor gene with gonadal and adrenal specificity. Given the similarities in the TGFß and activin transduction pathways and the recognized role of the TGFß pathway in tumor suppression (50), it is reasonable to consider that the activin receptors and downstream signaling proteins are tumor suppressors. In the following sections, the evidence suggesting that both the inhibin subunit gene and the activin signaling pathway are tumor suppressive will be reviewed.

1. Inhibin subunit as a tumor suppressor. Both sexes of inhibin-deficient mutant mice generated by targeted deletion of the inhibin subunit gene developed gonadal sex-cord stromal tumors with very high penetrance (49). The development of gonadal tumors was rapidly followed by a cancer cachexia-like wasting syndrome, which was associated with severe weight loss and pathology of the stomach and liver (51). After gonadectomy of these mice, tumors of the adrenal gland occurred (51). Both FSH and activin A levels were significantly increased in the serum.

In the absence of inhibin subunit expression, the role of activin in tumor initiation and/or the onset of cachexia required consideration. The symptoms associated with cachexia were attributed to activin, mediated by the ActRIIA receptor signaling pathway (51, 52). Mutant mice deficient in both the inhibin subunit and the ActRIIA genes developed tumors but did not suffer from an unusual weight loss and the stomachs and livers were histologically normal (52). This finding was consistent with the previous observation that systemic administration of activin A promoted similar cancer cachexia-like wasting symptoms (53). Furthermore, Cipriano et al. (54) showed that inhibin subunit-deficient mice that also overexpressed follistatin continued to develop tumors, but the cachexia-like symptoms were reduced. Thus, the weight of evidence suggests that activins play a significant role in the onset of cachexia in inhibin-deficient mice.

The role of activin in tumor development is unclear. In the ovary, it was suggested that a combination of elevated gonadotropins and activins promoted tumor formation. Gonadotropins stimulate activin production by human (46) and rat (47) granulosa cells in vitro, and activin is mitogenic in sex cord-stromal tumor cell cultures from inhibin subunit- and p53-deficient mice (55). However, the experimental evidence supporting a role for activin in tumor formation is unconvincing. First, mice deficient for both FSH and inhibin developed ovarian tumors, despite severely reduced serum activin levels (56). Second, overexpression of activin ß subunits alone in male mice did not result in testicular tumors (57). Third, ovarian tumor formation was evident in inhibin subunit and ActRIIA double mutant mice (52).

Ovarian transplant experiments provide additional evidence that activin is not essential for the initiation of gonadal tumors. The experiment described by Matzuk et al. (58) was designed to determine whether tumor initiation required an increased production of activin or the absence of inhibin in the circulation. Ovaries from 3-wk-old inhibin-deficient female mice were transplanted into the bursa of 3- to 4-wk-old wild-type immunocompatible female recipients. Either one or both of the ovaries from the recipients were removed from the bursa in which the inhibin-deficient ovaries were transplanted. If both normal ovaries were removed so that circulating levels of inhibin fell, the transplanted inhibin-deficient ovaries developed tumors and the mice became cachexic. If an inhibin-deficient ovary was transplanted into a mouse bearing a contralateral ovary so that circulating inhibin levels were maintained, no tumors developed. These results showed that the local production of activin within the transplanted inhibin-deficient ovaries was not sufficient for tumor development. Inhibin is an endocrine hormone that regulates gonadotropins; FSH levels were elevated in inhibin-deficient mice, and therefore, the role of gonadotropins requires consideration. Gonadotropins were essential for tumor formation, as mutant mice that lack both inhibin and GnRH did not develop gonadal tumors (56, 59), and roles for both FSH and LH were considered.

Although inhibin subunit mutant mice have elevated FSH levels, mice deficient in both inhibin subunit and FSH showed evidence of ovarian tumor formation, albeit at a reduced level compared with -deficient mutant mice (56). In addition, overexpression of FSH did not result in ovarian tumor formation (56). Alternatively, LH might be important in tumorigenesis because overexpression of LH in vivo was shown to cause ovarian granulosa and thecal tumors (60).

Huhtaniemi and colleagues (61) examined the role of gonadotropins in an alternate transgenic mouse model system that incorporated the simian virus 40 (SV40) T-antigen under the regulation of the inhibin subunit gene promoter. The inhibin subunit promoter targeted expression of the T- antigen to the gonads, and gonadal tumors arose. Removal of the gonads resulted in the formation of adrenal tumors. Huhtaniemi and colleagues (62, 63, 64) showed a role for gonadotropins in the development and growth of the T-antigen-induced tumors. Tumors did not develop after the withdrawal of gonadotropins using GnRH antagonists, by crossbreeding with gonadotropin-deficient hpg mice, or by long-term treatment with T. Further studies specifically implicated LH in adrenal tumorigenesis in this mouse model. After gonadectomy, tumors arose in the LH sensitive X zone of the adrenal gland, where inhibin subunit is normally expressed (62, 63, 64, 65).

Although the Matzuk and Huhtaniemi transgenic mouse models both illustrate that gonadotropins modify the role of inhibin in tumor formation, it is difficult to make direct comparisons between the two models. In one instance, loss of inhibin subunit expression caused tumor formation in inhibin-deficient mice and was associated with elevated levels of activin and FSH in serum. On the other hand, tumor formation in the Hutaniemi model was driven by expression of the SV40 T antigen, under the regulation of the inhibin subunit promoter. Therefore, the latter is not a model of inhibin deficiency (serum inhibin levels were elevated and FSH levels reduced); rather, it is a model in which the regulation of the inhibin subunit promoter was studied. Likewise, it does not contradict the hypothesis that inhibin is a tumor suppressor because tumorigenesis was driven by the SV40 T antigen.

Other factors were considered as modifiers of the role of inhibin in tumorigenesis. In male mice, the influence of androgens on tumor development was examined in transgenic mice that were inhibin deficient and carried the testicular feminization mutation, i.e., an inactivating mutation of the androgen receptor (66). Although testicular tumors continued to develop, multifocal lesions were observed at an earlier age and were less hemorrhagic at later stages. In contrast to the modifiers described above, Müllerian inhibitory substance synergized with the effects of inhibin subunit loss to influence and promote a more rapid development of testicular tumors (67). Similarly, enhanced gonadal tumorigenicity occurred in double mutant mice lacking both the inhibin subunit gene and the p27^Kip1 tumor suppressor gene. These mice developed ovarian and testicular tumors and died earlier than those mice lacking inhibin alone (68).

Thus, the mouse models support the hypothesis that the inhibin subunit is tumor suppressive. In addition, these studies reveal a complex network of interactions involving inhibin, activin, and other modifiers in the development and progression of gonadal and adrenal tumors.

2. Activin receptors and signaling proteins as tumor suppressors. The previous section examined the role of activin ligands in inhibin-deficient mice and identified an essential contribution of activins to the onset of cachexia rather than to the initiation of tumor formation. In this section, we consider the hypothesis that the activin signaling pathway is tumor suppressive and contributes to malignant progression. Activins share many common elements with the TGFß signaling cascade, members of which are considered tumor suppressors, e.g., Smad4/DPC4 (69). Several studies showed that the development of resistance to TGFß by tumor cells represents a key event in the progression to malignancy, and in colon cancers, resistance to TGFß was acquired through mutational inactivation of the TGFß type II receptor (70).

However, little is known about alterations in activin signaling events during the development and progression of endocrine-related cancers. Overexpression of the activin ß_A subunit was recorded in inhibin-deficient mice (71), but in normal mice, overexpression of this subunit alone did not lead to tumor formation (57). Up-regulation of TGFß ligand expression occurred in colon tumors, but up-regulation of ligand expression, per se, was not considered to be a key event in malignant progression. Instead, malignancy was associated with the presence of inactivating mutations of the receptors, so that the tumor cells were insensitive to the growth-inhibitory actions of TGFß. van Schaik et al. (72) investigated the levels of activin receptor expression in prostate carcinoma and showed that expression levels were reduced in malignant progression, but they did not determine whether inactivating mutations that might render the cells resistant to activin ligands were present. Although mutations of ActRIB were recently described in pancreatic cancers, it is not known whether these confer resistance to activin (73). It may prove insightful to compare changes to the activin signaling pathway with those of the TGFß signaling pathway. Many studies on activins focused on the changes to ligand expression. For example, down-regulation of activin subunit production by N-myc was reported recently in neuroblastoma cell lines (74), and the authors concluded that this would deprive the cells of a signal from this growth-inhibitory factor. Whether there is up- or down-regulation of activin ß subunit expression and therefore activin ligand levels, as described above, it is unlikely that ovarian tumor formation is primarily due to elevated levels of activin A or B in the inhibin-deficient mouse model.

The role of the other subset of activin ß subunits, ß_C, ß_D and ß_E, in tumorigenesis remains unknown. Although it was demonstrated that the activin ß_C subunit dimerized with the activin ß_A and ß_B subunits (75), a functional role for these heterodimers has yet to be established. Mice with null mutations in either the individual activin ß_C or ß_E subunit genes or both genes develop normally and have no obvious abnormalities in liver or reproductive function (11). The resultant effects of overexpressing these subunits are not known.

B. Molecular genetics of activin and inhibin gene loci
Malignant transformation and progression involves a complex series of genetic alterations that change the gene expression profile of the cells and promote tumor survival. Chromosomal regions harboring tumor suppressor genes are often deleted or down-regulated in cancer, whereas oncogenes and genes that promote cell survival are often localized to chromosomal regions over-represented in human cancers.

In the previous section, we reviewed the evidence suggesting that the inhibin subunit gene and/or the activin signaling pathway are tumor suppressive. To support this hypothesis, it would be predicted that genetic alterations to the chromosomal regions housing these genes would occur in malignancy. The chromosomal localization of the human inhibin- and activin-related genes was determined over the last decade. This section of the review provides a synopsis of the chromosomal localization of the inhibin and activin subunit genes and the genes that encode follistatin and members of the activin signaling cascade (Table 1). The recent literature is reviewed to determine whether mutations were commonly observed for these chromosomal regions in endocrine cancers and cancers of the liver and kidney (those discussed in Section IV).

Table 2 shows that both chromosomal loss and over-representation were observed in endocrine tumors for the chromosomal regions 5q, which harbors the follistatin gene [5q11.2 (85)]; 7p, which harbors the activin ß_B subunit gene [7p15–14 (76)]; 12q, which harbors the activin ß_C [12q13.1 (7)]; ActRIB [12q13 (77)] and possibly the activin ß_E genes [12q13.1 (9)]; and 15q, which harbors the Smad3 and Smad6 genes [15q21-q22 (113)]. In ovarian adenomas, LOH at 5q21–22 occurred in 30% of invasive carcinomas, whereas LOH at a nearby region, 5q32, was seen in only 7.7% of invasive carcinomas (78). Over-representation of chromosome 5q occurred in adrenocortical tumors (114), breast cancer (91, 115, 116), and prostate cancer (117).

Deletions at chromosome 12q occurred in prostate (80) and breast carcinomas (118). In prostate carcinomas, the levels of expression of ActRIB mRNA was reduced with relation to nonmalignant prostate tissues (72), and in pancreatic carcinomas, mutations of ActRIB were described (73). Breast carcinoma and adrenocortical cancers demonstrated gain of chromosome 12q (92, 105, 114, 119).

The 15q chromosomal region was deleted in pancreatic cancer (120) and over-represented in breast cancer (91, 92, 105). In prostate cancer, both loss and gain of this region was reported (121).

The 7p locus was over-represented in tumors of the breast (122) and prostate (80, 123). In prostate cancer, Alers et al. (80, 124, 125) reported that increased chromosome copy number for chromosome 7 was associated with recurrent and metastatic prostate carcinoma. Losses or deletions involving 7p only occurred in breast cancer (122, 126).

The above summary details the chromosomal localization of the inhibin and activin subunit genes, the follistatin gene, and the genes that encode members of the activin signaling pathway. Many of these chromosomal regions are altered in endocrine tumors; losses on chromosomes 2q, 3p, and 18q are more common than gains of these chromosomal regions. Both loss and over-representation of chromosomal regions 5q, 7p, 15q, and 12q occur in endocrine tumors. Although these observations do not specifically implicate the inhibin and activin genes, they do provide impetus for further studies to identify genetic alterations in tumorigenesis of the inhibin/activin subunit genes and the genes encoding the downstream signaling effectors of activins.

	IV. Endocrine and Other Tumors

Top Abstract I. Introduction II. Activin and Inhibin:... III. Activin and Inhibin... IV. Endocrine and Other... V. Summary References

 
A. Ovarian tumors
The mature ovary consists of two main regions, the outer cortex, containing the germinal epithelium and follicles, and the medulla, consisting of stroma. During the menstrual cycle, primordial follicles are recruited and either develop in the follicular phase to mature follicles destined to ovulate, or degenerate as a result of atresia. After ovulation, when the ovum is released, the remaining cells of the granulosa and theca interna undergo luteinization. The corpus luteum persists through the luteal phase, but in the absence of pregnancy, it undergoes degeneration and the cyclicity continues.

As the primordial follicle enters folliculogenesis to form preantral and then antral follicles, the follicles become sensitive to gonadotropins and synthesize inhibin , ß_A, and predominantly ß_B subunit proteins in the granulosa cell layers surrounding the oocyte (150, 151, 152). In the late luteal and early follicular phases of the menstrual cycle, FSH levels increase. Under FSH stimulation, serum inhibin B is preferentially increased until negative feedback occurs, and FSH levels fall before ovulation. The dominant follicle, which is now responsive to LH, produces more inhibin A than B. After the LH surge, the corpus luteum produces inhibin and ß_A subunits, as reflected in elevated serum inhibin A in the luteal phase of the cycle. Thus, there is differential expression of the inhibins during the menstrual cycle.

The ovary has a finite number of follicles that can lead to ovulation, and the follicles are essentially depleted during the fourth decade of life. With the decline in developing follicles, serum inhibin B levels fall. This is followed by a decline in the levels of inhibin A and E2 in the serum. There is a corresponding increase in FSH and LH that can be elevated up to 100 times the levels found before menopause. After menopause, serum levels of inhibin A, B, and subunit are very low or undetectable (4, 42, 153, 154, 155).

Tumors of the ovary arise from surface epithelium, germ cells, and sex-cord stroma. Malignant surface epithelial tumors of the ovary are the most common and include serous, endometrioid, mucinous, and clear-cell carcinomas, which represent 40, 20, 10, and 6% of ovarian cancers, respectively. Sex-cord stromal tumors, including GCTs, represent approximately 5% of ovarian cancers, and malignant germ cell tumors, including teratomas, represent approximately 1% of ovarian cancers.

1. Sex-cord stromal tumors. Inhibin was developed and successfully used as a serum and immunohistochemical marker of GCTs and for the early detection and monitoring of recurrence of GCTs (20, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167). The presence of inhibin , ß_A, and ß_B subunit mRNA (168, 169) and protein by immunohistochemistry (168, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182) in GCT tissues was widely reported (Tables 3 , 4 , and 5). Other sex-cord tumors, including Sertoli cell and mixed Sertoli cell/Leydig cell tumors, were also positive for inhibin and ß_A subunit proteins (Ref. 176 and Table 3). Fibroma and thecoma (thecal cell tumors) were immunopositive for the subunit but not for the ß_A subunit. Immunohistochemical identification of inhibin has been clinically used to differentiate sex-cord stromal tumors and other tumors such as endometrioid carcinomas (176, 183).

View this table: [in this window] [in a new window]   Table 3. Detection of inhibin and ß subunit mRNA in ovarian tumors1

2. Surface epithelial cell tumors. Epithelial cell carcinomas represent 90% of all ovarian tumors. These include serous, mucinous, and endometrioid tumors and are each subclassified as benign, borderline, or malignant. The origins of these tumors are unclear but are thought to involve invagination of the germinal or surface epithelium of the ovary with the formation of inclusion cysts as a consequence of the repeated trauma induced by the ovulation process. The progression of these tumors is believed to proceed either directly, or via a benign and borderline intermediate stage, to malignancy (184, 185, 186, 187). The relative importance of the two pathways is still unclear (186). In the case of mucinous tumors, the close physical proximity of benign epithelium with an apparent intermediate transition stage suggested that this cancer originated from pre-existing mucinous adenomas. The much lower association of benign serous adenomas with serous carcinomas suggests that de novo formation may be the major cause (185). The role of activin and inhibin in the progression to malignancy is poorly understood because most of the studies to date center on defining the utility of inhibin in the diagnosis of ovarian tumors.

Mucinous carcinomas represent 15% of all malignant ovarian tumors and histologically resemble endocervical or enteric epithelium. Expression of the inhibin and activin , ß_A, and ß_B subunits was demonstrated in benign, borderline, and malignant mucinous tumor tissues by RT-PCR (Table 3 and Refs. 168 and 169). Numerous immunohistochemical studies examined the activin ß_A and ß_B subunits in mucinous ovarian cancers and detected these proteins in more than 90% of the tissues (Table 4 and Refs. 170, 171, 174, 188 and 189). The specific localization of the inhibin subunit to the malignant epithelium is controversial and variable and appears to be related to differences in antisera/fixation methods used by the various groups. Table 4 summarizes the data reporting differences in the detection of inhibin subunit immunoreactivity in mucinous tumors using different antisera. Serum inhibin subunit levels were consistently elevated in up to 90% of postmenopausal women with mucinous cancers, and this observation was of diagnostic value (20, 166, 167). Dimeric inhibin and activin serum levels were also increased (167, 190, 191, 192).

View this table: [in this window] [in a new window]   Table 4. Detection of inhibin and ß subunits by immunohistochemistry in ovarian tumors1

In endometrioid carcinomas, inhibin and activin ß_A subunit mRNAs were detected by RT-PCR, and activin ß_A protein was detected by immunohistochemistry (Tables 1–3 and Refs. 168, 170, 171, 172, 175, 176, 180, 182, 183 and 193). The inhibin subunit was not readily immunodetectable in serum or tissues of patients with endometrioid carcinomas.

3. Germ cell tumors. Germ cell tumors, which make up the third major ovarian carcinoma grouping, were negative for inhibin and activin as assessed by immunohistochemistry (Table 4 and Ref. 176).

4. Association of inhibin with luteinized stromal tissue of the ovary. A number of immunohistochemistry studies (see Table 4) using the inhibin subunit antibodies (in particular R1) noted that there was considerable immunoreactivity in the stromal area surrounding the ovarian tumor, even if the tumor itself was not apparently inhibin subunit immunoreactive. These inhibin-positive cells resemble the theca-like cells around normal follicles (172, 173). Immunoreactivity was observed with all ovarian carcinomas including those metastasizing from other tissues to the ovary (168), for example, in Kruckenberg tumors that are colon carcinoma metastases to the ovary (172, 173). It is not clear whether these cells express the activin ß_A subunit (168, 171). The corresponding localization of the inhibin and activin ß_A subunits in luteinized stromal cells in normal postmenopausal ovaries was limited (168) or not evident (172, 173). These observations suggest the expression of inhibin by the surrounding stromal tissue was an ovarian reaction to the presence of a tumor. Kommoss et al. (176) postulated that "neoplastic ovarian epithelium and germ cells stimulated stromal cells to differentiate into spindle-shaped or fully luteinized steroidogenic cells." In a study of tissue from ovaries that were removed because of a high risk of ovarian cancer, a preneoplastic phenotype was observed. Specifically, the presence of hyperactive stroma was noted in 15 of 20 ovaries from the high-risk group compared with 2 of 20 from a separate group of control ovaries (194). The authors queried whether it was the stroma in ovarian tumors that provided the abnormal growth stimulus to the epithelium.

5. Clinical application of inhibin assays to sex-cord stromal and epithelial tumors. Serum inhibin assays, particularly those that detect all inhibin forms, are clinically useful in the early detection of granulosa cell and mucinous tumors (20, 158, 160, 161, 163, 164, 165, 166, 167, 195). The assays detected benign, borderline, and malignant forms, and there was no differentiation between the various stages of disease, although the number of clinical cases observed in the earlier stages of the disease was limited. These assays appeared to fulfill a useful function for detecting mucinous carcinomas and were more effective at detecting this type of tumor than other cancer markers, including CA125 (20). Few studies examined serum activin A as a marker of ovarian cancers (192, 195). The role of activin B in ovarian carcinogenesis requires the development of a suitable human activin B assay.

The observation that CA125 was a marker for a range of epithelial carcinomas and inhibin was a marker for sex-cord stromal tumors and mucinous carcinomas suggested that a combination of the CA125 and inhibin subunit assays would detect the majority of ovarian cancers. In fact, studies showed that the combined assays detected 90% of all ovarian cancers (20). However, the utility of the inhibin assays was compromised in some circumstances. In postmenopausal women, the assays were most appropriate for early detection and monitoring of recurrent cancer, as the serum inhibin levels were very low or nondetectable. In women of reproductive age, the inhibin assays were less useful because inhibin levels were elevated and fluctuated. In women with GCTs, serum levels of inhibin were high and readily measured and monitored; those with mucinous cancers had much lower levels of inhibin, requiring a low, stable background for reliable detection. In women of reproductive age, the use of inhibin to monitor the recurrence of disease after surgery to remove one ovary may be compromised because of the presence of the contralateral ovary.

Progress in understanding the role of activin and inhibin in ovarian cancer is hampered by the difficulties of culturing ovarian cell lines from normal and malignant tissue. In particular, ovarian cells proliferated poorly in culture and lost their ability to respond to gonadotropins. Studies with both primary ovarian cell cultures (196) and established cell lines (197) showed a loss of responsiveness to gonadotropins and a rapid decline in synthesis of the inhibin subunit, although activin ß_A subunit and activin A production was retained. A number of studies were undertaken to develop immortalized cell lines responsive to gonadotropins with some success (166, 198, 199, 200, 201, 202). Interestingly, a recent study reported that activin A inhibited growth and induced apoptosis in early neoplastic and tumorigenic ovarian surface epithelial cells (203). This is one of the few reports of a growth-inhibitory action of activin A on ovarian cells and contrasts with the mitogenic actions of activin in the normal ovary. Additional work is required to determine whether activin A has growth-inhibitory as well as stimulatory effects on ovarian tumor cells.

B. Prostate tumors
In the literature, the name "inhibin" was used to describe two unrelated proteins. Prostatic inhibin, isolated initially from seminal plasma, has numerous names including ß-inhibin, prostatic inhibin peptide (204), ß-microseminoprotein (205), Ig binding factor (206), and prostatic secretory protein of 94 amino acids (207). Prostatic inhibin is a 94-amino acid cysteine-rich, nonglycosylated protein of 10.7 kDa. Prostatic inhibin is not the same as dimeric inhibin and is not discussed further in this review.

Initial studies to determine expression and localization of inhibin and activin in normal prostate were performed using the rat prostate (208, 209). Normal rat prostate tissues expressed the inhibin and activin , ß_A, and ß_B subunits, and immunoreactive activin and inhibin were detected and measured. Studies with human prostate biopsy tissue from men with benign prostatic hyperplasia demonstrated that the nonmalignant prostate had the capacity to make both inhibin and activin (210). The basal and secretory epithelial cells showed inhibin subunit immunoreactivity as well as activin ß_A subunit immunoreactivity. Expression of the activin ß_B subunit differed from that of inhibin and activins and ß_A, as ß_B expression localized predominantly to the basal epithelial cells with minimal expression observed in the secretory cells. In the stroma, smooth muscle cells were positive for the activin ß_B subunit. The colocalization of inhibin and activin ß subunits to the nonmalignant prostate suggested that this tissue produced two forms of inhibin (inhibins A and B) and three forms of activin (activins A, B, and AB).

Prostate cancers are commonly adenocarcinomas (95%); neuroendocrine tumors are rarely detected. All studies that examined inhibin and activin expression in prostate cancer used adenocarcinomas or cancer cell lines such as LNCaP, DU145, and PC3. Inhibin and activin were implicated in prostate carcinogenesis after the observation that the pattern of expression of the subunits differed in malignant tissues relative to nonmalignant prostate epithelium. In high-grade prostate cancer biopsy tissues, the activin ß_A and activin ß_B subunits were expressed in both regions of nonmalignant epithelium and regions of carcinoma (211). In contrast, selective down-regulation of inhibin subunit expression occurs in high-grade prostate cancer cells, whereas adjacent areas of nonmalignant epithelium retained inhibin subunit expression (75). Similarly, the prostate cancer cell lines, LNCaP, DU145, and PC3, did not express the inhibin subunit but expressed the activin ß_A and ß_B subunits (212, 213). Loss of inhibin subunit in high-grade prostate cancer and the cancer cell lines is consistent with its role as a tumor suppressor. The mechanisms responsible for down-regulation of the inhibin subunit gene may include gene deletion (LOH) at the 2q33–36 chromosomal regions, where the inhibin subunit gene is found, and hypermethylation of the promoter of the inhibin subunit gene (J. F. Schmitt and G. P. Risbridger, unpublished observations).

Despite frequent loss of inhibin subunit expression in prostate cancer, the inhibin subunit-null mice did not develop prostate cancer. There may be several reasons for this. Other than man, the dog is the only animal known to spontaneously develop prostate cancer, and carcinoma of the prostate has a long period of latency. The inhibin-deficient mice developed gonadal and adrenal tumors, and in the males, the tumors were lethal by 12 wk (49). This was probably insufficient time to make conclusions about the development of prostate tumors. A period of 10–20 wk was required for the development of prostate tumors in the TRAMP (transgenic adenocarcinoma of the mouse prostate) mouse, in which a region of the probasin promoter was fused to SV40 T-antigen; this is considered to be an aggressive model of prostate cancer (214). Furthermore, the inhibin-deficient mice initially developed testicular tumors, and adrenal tumors only emerged after castration. Because prostate carcinogenesis is androgen dependent, it is not possible to assess the development of androgen-regulated prostate cancer in this setting.

In prostate cancer, the loss of the inhibin subunit expression, but not of the activin ß subunit expression, implied that the synthesis and actions of activin were unopposed by inhibin. Hence, it is important to determine how activin contributes to the tumorigenic process. Studies with the LNCaP cell line demonstrated that activin A inhibited the proliferation of LNCaP cells, altered cell morphology, and induced apoptosis (212, 213, 215, 216). Primary human prostate epithelial cells were also growth inhibited by activin A (217). The specificity of the effects of activin on LNCaP cells, as well as on the primary prostate epithelial cells, was supported by the ability of follistatin to block these effects (213, 215).

The growth inhibitory effects of activin described in these studies were inconsistent with the rapid growth characteristics of tumor cells in malignancy. It was postulated that, like TGFß, the tumor cells acquired resistance to activins (218). This could occur through mutation of the activin receptors or signaling molecules; whether such mutations occur in prostate cancer remains to be determined. A recent study, however, showed reduced expression levels of one of the activin receptors, ActRIB, in prostate cancer relative to nonmalignant prostate tissues (72).

The expression of follistatin provides another means by which prostate cancer cells could be protected from growth-inhibitory effects of activin. The effects of follistatin on prostate cancer cell sensitivity to activin were examined by comparing the LNCaP cell line, which was growth inhibited by activin, with the PC3 cell line, which was resistant to the antiproliferative and apoptotic effects of activin (212, 213). These cell lines showed differential expression of the follistatin isoforms (219); both cell lines expressed the secreted form of follistatin, FS315, but only the PC3 cell line expressed the membrane bound follistatin, FS288. Hence, the different sensitivities of the cell lines to the effects of exogenous activin may be related to the expression of FS288. Further support for this idea was gained from the studies by McPherson et al. (219), which showed that neutralization of FS288 protein in PC3 cells rendered them sensitive to exogenous activin A.

Using a specific antibody, the activin ß_C subunit was detected in basal epithelial cells in nonmalignant prostate tissue and in the cancer cells and cell lines, as well as in liver (10). Because the activin ß_C subunit forms heterodimers with the other activin ß subunits (ß_Cß_A, ß_Cß_B), but not with the inhibin subunit (10), a range of new activins, but not inhibins, may be present in these tissues. A change in the relative levels of the activin ß subunits expressed during cancer progression could effect the proportion of homodimers and heterodimers produced in the cells and could result in a significant regulation of the levels of bioactive activin A. New, specific assays are required to measure and identify novel activins in prostate.

C. Testicular tumors
A wide range of histological types of testicular tumors are recognized and can be divided into two major groups: germ cell tumors, which account for 95% of cases, and nongerminal, stromal, or sex-cord tumors. Malignant transformation of germ cell tumors includes embryonal carcinomas, choriocarcinomas, teratomas in the form of squamous cell carcinomas, or adenocarcinomas and teratocarcinomas that contain both teratoma and embryonal carcinoma.

The testis is the primary site of inhibin production in the male (220), and the role of inhibin and activin in male reproductive processes was extensively studied (for reviews see (221, 222, 223). Inhibin B is the main form of inhibin found in the male circulation and seminal plasma (224, 225), and the and ß_ß inhibin and activin subunits are expressed predominantly by Sertoli cells within the testis and also by Leydig cells (226, 227, 228). Activin A immunoreactivity was detected in seminal plasma, and expression of the activin ß_A subunit was localized to the Sertoli and Leydig cells (228).

Although the testis is a major source of inhibin, few studies examined the inhibin and activin subunits in human testicular cancer. In the testis, inhibin appeared to be a marker of Sertoli cell tumors, and an elevation in the serum inhibin levels occurred in both humans and dogs with Sertoli cell tumors (229, 230) and in dogs with Leydig cell tumors (231, 232). Elevated serum inhibin levels in dogs with sex-cord testicular tumors were associated with increased mRNA levels for the inhibin and activin ß_B subunits within the testes (231). In a case study of a 12-yr-old boy with Sertoli cell tumors, elevated serum inhibin levels were associated with increased levels of mRNA for the inhibin and activin , ß_A, and ß_ß subunits within the diseased testes, as determined by Northern analysis (230). Removal of the testes resulted in a drop in serum inhibin levels. Similarly, a reduction in serum inhibin B to nondetectable levels was associated with eradication of testicular carcinoma in situ by radiotherapy (233).

Immunohistochemistry studies localized inhibin subunit immunoreactivity to both malignant and nonmalignant Sertoli cells in sex-cord tumors (229) and to granulosa cells in a granulosa cell tumor of the testis (234). In a study of patients with unclassified sex-cord stromal tumors with incorporated germ cells, inhibin was present in the Sertoli cell tumors but not in the neoplastic germ cells within the tumors. However, in one sample, inhibin immunoreactivity was detected in germ cells with the morphological appearance of seminoma cells (235). Similar to the ovary, inhibin expression and secretion may provide a marker for determining the presence of Sertoli cell tumors of the testes.

D. Breast tumors
The early reports of changes to inhibin levels in breast cancer were related to the expression of the peptide hormone described by Sheth and colleagues (236). This protein is not the same protein as the inhibin discussed in this review (see Section IV.B). The , ß_A and ß_B inhibin and activin subunits were immunolocalized to the epithelial cells of normal breast tissue (237). In this study, expression of all subunits was reduced in benign breast neoplasms, and inhibin subunit expression was further reduced in breast carcinoma. Expression of the activin ß_A and ß_ß subunits was not detected in breast carcinomas.

A limited study on MCF-7 cells showed that, as well as expressing the activin receptors, these cells produced the inhibin and activin subunit proteins (238). Indeed, activin A was found to be a potent inhibitor of MCF-7 cell growth (239), causing cell cycle arrest in G₁. Activin A also inhibited tubule formation by human mammary organoids in vitro, suggesting a role for activin A in regulating mammary cell growth and morphogenesis (239). The effect of inhibin in these systems was not determined, and it remains unknown as to whether inhibin can oppose the action of activin A.

Kalkhoven and colleagues (240) evaluated the effects of activin on a panel of breast cancer cell lines that were ER positive or negative. The ER-positive cell lines in the study were inhibited by activin A, whereas the ER-negative cell lines were not. In two of the ER-negative cell lines, resistance to the growth-inhibitory effects of activin A were explained by down-regulation of the activin receptors. In two other ER-negative cell lines, MDA-MB231 and MDA-MB468, activin insensitivity was not due to reduced activin receptor levels. Instead, the failure of the MDA-MB468 cell line to respond to activin was explained by loss of Smad4 expression in these cells. Transfection of Smad4 into these cells rendered them sensitive to inhibition by activin. The other activin resistance/ER-negative cell line, MDA-MB231, expressed both Smad4 and Smad2. In this case, additional studies revealed that these cells lacked a functional ActRI (240).

The limited data from the studies mentioned in the previous paragraph described the localization of activin and its effects in breast cancer cells and suggested that resistance to the growth-inhibitory effects of activin might involve changes to the activin signaling pathway. Additional studies are required to define the contribution of inhibin, activin, and the activin signaling pathway to tumorigenesis.

E. Adrenal tumors
The adrenal cortex is structurally and functionally distinct from the medulla and is a site of synthesis of glucocorticoids, mineralocorticoids, and sex steroids. Excessive production of glucocorticoids (Cushing’s syndrome), aldosterone (Lonn’s syndrome), or sex steroids may be due to primary adrenal neoplasms. Primary adrenal neoplasms, including adrenal cortical carcinomas, account for up to 25% of cases of endogenous Cushing’s syndrome. Aldosterone-producing adenomas can lead to primary hyperaldosteronism and hypertension. Androgen secretion by cortical neoplasms may result in virilization in the female and precocious puberty in the male. Feminizing adrenal tumors associated with estrogen synthesis can also occur. The most significant adrenal medullary neoplasm is pheochromocytoma.

All zones of the human adult adrenal gland expressed both the activin ß_A and ß_B subunits, suggesting that activins were synthesized in this organ (241). Expression of the inhibin subunit was investigated more widely because the earlier data from animal models suggested that it was an adrenal tumor suppressor (49, 51, 62). An early study detected inhibin subunit immunoreactivity in hyperplastic tissues and adrenocortical carcinoma (159). This observation was supported by data from larger, subsequent studies of tissues from patients with adrenal cortical neoplasia (178, 241, 242, 243, 244). In general, inhibin subunit immunoreactivity was detected in adrenal cortical adenomas and carcinomas. Inhibin subunit immunoreactivity provides a diagnostic marker that can be used to differentiate adrenal cortical tumors from histologically similar tumors, including phechromocytomas, hepatocellular, and renal cell carcinomas. The morphological distinction of adrenal cell carcinoma and renal cell carcinoma is not always feasible on the basis of cytology when fine-needle aspiration material is obtained from renal, adrenal, or metastatic tumors. In this context, positive staining with antibodies to the inhibin subunit can be used by the cytopathologist to discriminate between adrenal and renal cell carcinomas.

As described in the previous paragraph, there is an apparent inconsistency between these observations in adrenal tumor tissues and the role of the inhibin subunit gene as an adrenal tumor suppressor in the inhibin-null mice. However, a recent study (241) identified a subgroup of adrenal cortical carcinomas in which there was loss of inhibin subunit immunoreactivity, and the authors suggested that this might indicate a role in tumor progression. It will be interesting to determine whether malignant progression correlates with loss of inhibin immunoreactivity in the adrenal gland.

F. Pituitary tumors
In the normal pituitary, the secretion of FSH and the stability of FSHß subunit mRNA was reduced by inhibin. In contrast, activin increased FSHß subunit expression and was a potent differentiation factor in the pituitary (245, 246, 247). Inhibin and activin and ß_A subunit immunoreactivities were localized within FSH- and LH-secreting gonadotropes, whereas immunoreactivities of the activin ß_A subunit and the activin receptors (ActRIB and ActRII) were present throughout the anterior pituitary (248).

Pituitary carcinomas are rare and often originate in the adenohypophyseal cells, whereas adenomas are common and are present in up to 20% of normal pituitaries (249). Most of the studies on inhibin and activin expression and action in neoplastic pituitary examined tissue or cells from adenomas. In a range of pituitary adenomas, mRNAs for the inhibin and activin ß_B subunits (but not ß_A subunit) and the activin receptors (ActRIA, ActRIIB, and splice variants of ActRIB) were detected (250). Follistatin expression was reduced in the gonadotrope adenomas compared with the normal pituitary (251).

Activin had an antiproliferative effect on cells cultured from a subset of pituitary adenomas, although cells cultured from other pituitary tumors were unresponsive to activin (252). The cells from tumors that were growth inhibited by activin expressed little or no follistatin, which implied that differential expression of follistatin affected activin-induced growth arrest (252). Interestingly, the human pituitary cell line hPit-1 expressed uniformly high levels of follistatin mRNA, and the cells were moderately tumorigenic in immune-deficient mice (253). To investigate the hypothesis that activin receptors acted as tumor suppressors in pituitary tumors, D’Abronzo et al. (254) performed mutational analysis of the intracellular kinase domains of the ActRI and ActRII genes and found that somatic mutations were rare. The effectors of downstream signaling events (e.g., Smads) and their role in pituitary tumors remains to be studied.

G. Pancreatic tumors
There is evidence that the activin signaling pathway is tumor suppressive in pancreatic tumors. In pancreatic cancers, deletions were observed in ActRIB, as were mutations of the Smad4 gene (69, 73). The tumor-suppressive function of the TGFß pathway in pancreatic cancers was confirmed by findings that 82% of pancreatic cancers had genetic inactivations of ALK-5 (TGFßRI), Smad4, or TGFßRII (255). The evidence to implicate specific activin ligands in pancreatic cancers was less obvious.

Expression of the inhibin subunit was not detected in pancreatic carcinomas, whereas activin ß_A subunit expression was detected (256). The effects of activin, like TGFß, were growth inhibitory. Mice bearing a dominant-negative mutation of TGFßRII showed increased proliferation of pancreatic acinar cells and severely perturbed acinar differentiation (257) but remained responsive to activin A. These results suggested that either the inhibitory effects of activin and TGFß are independent of one another, or the signaling pathways converge after receptor activation.

Carcinomas of the exocrine pancreas that arise from ductal epithelial cells are the most common type of pancreatic neoplasm. Cystic tumors are less common and represent about 5% of tumors. This group of cancers was reported to express ovarian-like stroma. Positive staining for the inhibin subunit was one of the markers used to identify this type of stroma (258). In a study of 56 patients with mucinous cystic tumors of the pancreas, 66% had inhibin subunit-positive stroma (259), and based on the similarities between pancreatic and ovarian mucinous cystic tumors, the authors suggested a common pathway of tumor development. As discussed in Section IV.A, the inhibin subunit was used as a sensitive marker of primary and recurrent granulosa cell tumors of the ovary; it is not known whether inhibin subunit can be used to detect/monitor cystic neoplasms of the pancreas.

H. Placental tumors
During pregnancy, serum inhibin A levels are higher than in the normal menstrual cycle, and the placenta is a source of inhibin. The cellular localization of inhibin in the placenta is controversial, and both the cytotrophoblasts and syncytiotrophoblasts were reported as positive for inhibin subunit immunoreactivity (260, 261, 262, 263, 264). The conflicting results of such studies may be due to the use of different antibodies to the subunit protein, together with varying methods of detection including antigen retrieval or signal amplification.

Proliferation of trophoblastic tissue results in a range of tumors and tumor-like conditions that include hydatidiform mole, invasive mole, choriocarcinoma, and placental-site trophoblastic tumor. Several studies reported that immunohistochemical localization of the inhibin subunit was useful in the differential diagnosis of gestational trophoblastic vs. nontrophoblastic lesions. At times, such distinctions can be difficult if an analysis is solely based on morphology.

Hydatidiform moles are characterized by cystic swellings of the chorionic villi accompanied by trophoblastic proliferation and are usually diagnosed by ultrasound examination and an elevation in serum levels of human (h)CG. In 10% of patients, invasive moles develop, and in 2.5% of patients, choriocarcinoma will occur. Serum inhibin may be a useful adjunct to hCG and human placental lactogen levels, which are widely used as markers for this condition (265).

Choriocarcinomas consist of abnormal proliferation of both cytotrophoblasts and syncytiotrophoblasts, and expression of the inhibin subunit was observed in two patients examined (260). The authors concluded that, because choriocarcinoma within the uterus or in extrauterine sites can be confused with other malignant neoplasms, inhibin may be a useful histochemical marker for diagnosis of the former lesion.

Placental-site trophoblastic tumors are rare tumors composed of proliferating intermediate trophoblasts, and levels of hCG are usually low in these tumors. Placental site nodules are described as being composed of intermediate trophoblasts and are usually benign lesions. In conjunction with cytokeratin 18, inhibin subunit immunoreactivity was a useful marker to identify placental-site nodules and to distinguish them from squamous cell carcinoma of the cervix. In a study of 42 patients, all placental site nodules expressed the inhibin subunit and cytokeratin 18, whereas there was no positive staining in squamous cell carcinoma of the cervix (266). Thus, the differential and correct diagnosis of these lesions may be improved with immunostaining for the inhibin subunit.

Overall, the utility of immunohistochemical staining for the inhibin subunit was based on the consistent expression of the protein in nearly all gestational trophoblastic lesions, whereas it was not expressed in other tissues that might be confused with gestational trophoblastic lesions (264). In contrast, there appeared to be no value in the measurement of activin A levels in serum from women with placental tumors (267), and the detection of activin in trophoblastic lesions has received little attention.

I. Endometrial tumors
The , ß_A, and ß_B inhibin and activin subunits were detected in normal endometrium by immunohistochemistry and in situ hybridization (268). Inhibin A, inhibin B, and activin A production was detected in endometrial epithelial and stromal cells in vitro and in uterine flushings (195). Uterine fluid and serum from women with endometrial adenocarcinoma showed significantly elevated activin levels that were reduced after surgery (195).

J. Kidney tumors
Early studies by Shiozaki et al. (269) suggested that the relative levels of activin A and follistatin were important markers of chronic renal failure, and Sakamoto et al. (270) described the elevation of free follistatin levels in patients with chronic renal failure. There are no data to describe the changes to serum follistatin or activin in patients with renal cell carcinomas.

In contrast, the utility of inhibin subunit staining for the diagnosis of renal cell carcinoma was examined. Adenocarcinomas of the kidney expressed the inhibin subunit, whereas renal cell carcinomas were negative for the inhibin subunit, facilitating the diagnosis by immunohistochemistry (159, 242, 244).

K. Liver tumors
Several studies showed that the inhibin subunit can be used for immunohistochemical diagnosis of adrenal cortical neoplasms because these are inhibin subunit positive, whereas renal cell carcinomas or hepatocellular carcinomas are mainly negative (242, 244, 271). Although one report suggested that hepatocellular carcinomas were positive for the inhibin subunit (272), it was considered that this was a false positive result caused by the presence of endogenous biotin. In adult GCTs of the ovary, foci of hepatic cells were identified because they did not express the inhibin subunit (273, 274). Therefore, inhibin immunostaining has diagnostic utility because hepatic carcinoma did not show inhibin immunoreactivity.

Changes in the expression of activin A in the liver received little attention. Activin A inhibited the proliferation of the liver cell lines HepG2 and HLF (35, 275, 276). Inhibin had no activity of its own on HepG2 cells but antagonized the inhibition of liver cell growth by activin A (35). In vivo, the development of gonadal tumors in inhibin-deficient mice was rapidly followed by a cancer cachexia-like wasting syndrome (51). This syndrome was associated with hepatocellular necrosis around the central vein, consistent with previously reported effects of elevated activin A on rat hepatocytes (277). Subsequent studies supported the concept that the cancer cachexia-like symptoms were induced by elevated activin A levels (52).

	V. Summary

Top Abstract I. Introduction II. Activin and Inhibin:... III. Activin and Inhibin... IV. Endocrine and Other... V. Summary References

 
A. The process of tumorigenesis
Tumorigenesis is a multistep process involving initiation, promotion, invasion, and metastasis. A carcinogen induces general or specific changes to DNA, but genomic damage alone seldom leads to tumor formation. In normal circumstances, the primary lesions are transient and are eliminated by the activation of cell death or DNA repair mechanisms. If these lesions are not repaired, they become mutations in the target cell population as it proliferates. Proliferation of cells containing this damage may often confer selected growth advantages and mark the promotion of tumorigenesis. The duration of tumor growth varies considerably, but at any stage progression can be accelerated by general or specific endogenous or exogenous factors. When this occurs, several sequential and parallel events are evident in the neoplasm; these may include acquisition of physiological properties that enhance invasiveness and cell motility, escape from immune surveillance, and the emergence of new growth-regulatory mechanisms in distant metastatic sites.

Tumors, including those of the breast and prostate, can be induced by the inappropriate expression or action of mitogenic or antiproliferative factors. Hormones and growth factors can exert proliferative and antiproliferative effects on a target cell directly or indirectly through activation of paracrine and autocrine regulatory loops. Inhibin and activin are growth factors that exert their effects via complex receptor-mediated signaling pathways. The data presented in this review support the hypothesis that the inappropriate activation or deactivation of these pathways could contribute to the tumorigenic process.

B. Role of inhibin in tumorigenesis
In this review, we considered the case that the inhibin subunit is a tumor suppressor based on the results from transgenic mouse models in which deficiency of the inhibin subunit gene was associated with tumorigenesis (49, 278). In contrast, the clinical data from women reported up-regulation of the inhibin subunit and its use as a marker to detect and monitor the recurrence of some types of ovarian carcinomas, e.g., GCTs. Other types of ovarian tumors, particularly serous carcinomas, demonstrate loss of inhibin subunit immunoreactivity. These observations raise the following two issues: Does the inhibin subunit have a different role in mice and women, and does the up-regulation or down-regulation of the inhibin subunit contribute to tumorigenesis? It is difficult to reconcile the differences in the data from mice and humans with ovarian carcinomas. In other types of endocrine cancers, the inhibin expression is also diverse. Inhibin is elevated in testicular Sertoli and Leydig cell tumors, in adrenocortical adenocarcinomas, and in placental tumors. In contrast, negative staining for inhibin was reported in renal cell, hepatocellular, pancreatic, and prostate carcinomas.

In general, the current body of evidence suggests that the different patterns of inhibin subunit expression are specific to the organ in which the tumor arises (Table 6A). One explanation may lie in the influence of gonadotropins on the different tissues. The gonads, adrenal, and placenta are gonadotropin responsive, and the data from the mouse models demonstrated that gonadotropins were modulators of inhibin subunit gene activity. The prostate, breast, kidney, liver, and pancreas are not regarded as organs primarily regulated by gonadotropins, and therefore, the effects of inhibin may be different and modulated by other factors.

This review highlighted the potential role of the inhibin subunit gene in tumorigenesis of endocrine organs, in which altered expression may be of diagnostic or prognostic significance. However, the current data are limited. Many of the studies only examined a small number of tumors; e.g., in the study of inhibin in choriocarcinoma, only two patient tissues were examined (260). In many of these studies, human control tissue was difficult to obtain, yet adequate analysis of appropriate control tissue is essential for comparison to malignant tissues. Furthermore, the range of different assay methods to detect inhibin subunit gene expression contributed to variable results and affected the utility or application of serum inhibin peptide measurements for the detection and monitoring of endocrine cancers. For example, in the ovary, GCTs produced both monomeric inhibin subunit and dimeric inhibin forms detected by most types of inhibin assays, whereas mucinous tumors predominantly produced free inhibin subunit. Thus, assay methods that detect both free inhibin subunit and dimeric forms of inhibin appear to be more useful and specific in monitoring a range of ovarian cancers.

C. Role of activin in tumorigenesis
Activin, like TGFß, can inhibit or stimulate cell growth. Accordingly, in tumors in which activin is growth inhibitory, the tumor cells must acquire resistance to activin to allow malignant progression. In tumors in which activin is growth stimulatory, sustained activin signaling would promote tumorigenesis (Table 6B).

Activins have growth-inhibitory effects on breast, liver, and prostate cancer cells, as well as on pituitary adenomas (see Section IV), yet there are limited data to show that the acquisition of resistance to activin is associated with tumor progression. In the prostate, the androgen-responsive LNCaP cells were growth inhibited by activin A. The PC3 tumor cells were androgen independent and resistant to the effects of activin A. In vivo, a switch from androgen-dependent to -independent tumor growth occurred in the progression of prostate cancer. In breast cancer cell lines, resistance to the growth-inhibitory effects of activin A was associated with the ER status. ER-positive cells lines were responsive to activin A, whereas receptor-negative cell lines were resistant to activin A.

Resistance to activin effect could be acquired through several mechanisms. Mutations of signaling molecules of the activin cascade would lead to activin resistance and were identified in pancreatic carcinomas in which ActRIB and Smad4 were mutated (69, 73). In breast and prostate cancer cell lines and tissues, resistance to activin was associated with low levels of activin receptor expression (72, 240), but inactivating mutations were not investigated.

In tumor tissues that are growth inhibited by activins, it is relevant to ask why the tumor cells should retain the capacity to synthesize these ligands. The answer may lie in the recognition that activins are found in numerous cells and tissues and have multiple actions such as suppression of the immune response, wound healing, tissue repair, and angiogenesis. Many of these features of the activin ligands would promote tumor progression.

In tissues in which activin has a proliferative effect, one would expect to observe changes consistent with sustained, or even enhanced, signaling of these ligands (Table 6B). Tissues that are growth promoted by activin include the testis and ovary. In the normal ovary, activin is mitogenic in combination with FSH (46, 47), and inhibin subunit-null mice have elevated activin and FSH levels. A role for activin in promoting cachexia was suggested after the generation of mutant mice with loss of both the inhibin subunit and the ActRII receptor. In these mice, cachexia was reduced, but tumors formed.

Thus, activin is growth stimulatory or inhibitory, and these actions may differ between organs or tissues or even in the same tissue type. For example, a recent study reported that ovarian surface epithelial cells were growth inhibited by activin A (203), which is in contrast to the effects of activin A in the normal ovary. Regardless of whether activin is proliferative or antiproliferative, the question arises as to the effect of activin in the absence and presence of the inhibin subunit. Is the action of activin in tumorigenesis influenced by inhibin subunit expression, and if so, how? Evaluation of this possibility requires investigation of the relative levels of expression of the subunits and their interaction; this needs to be considered at multiple stages of malignant progression.

D. Future directions
This review has identified a considerable body of evidence to support the role of inhibins and activins in endocrine-related cancers. However, additional work is required to define the exact mechanisms by which inhibins and activins contribute to the process of neoplastic transformation during the stages of initiation, promotion, or progression of endocrine-related cancers.

The current review emphasizes that future studies need to address a number of issues in determining the role and diagnostic/prognostic significance of these ligands in tumorigenesis. The expression and cellular localization of inhibin and activin subunits in normal tissues requires documentation. Changes to activin and inhibin subunit expression and localization that occur during malignant progression require characterization using a large number of patient tissues where the tumor pathology and disease outcome are clearly defined. To assess the contribution of activin and inhibin to tumorigenesis, the relative levels of these ligands needs to be determined. This will require specific assays to measure activin and inhibin, in bound and free forms, and to understand how subunit expression is regulated and directs production of the different dimeric proteins. In addition, the contribution of binding proteins and signaling molecules to the tumorigenic process requires evaluation and could provide targets for the development of novel therapeutics.

	Acknowledgments

 
The authors thank Prof. P. Fuller for helpful discussions and S. Godden for assistance in the preparation of this manuscript.

This work was supported by Program Grants 97/3218 (to G.P.R. and J.F.S.) and 98/3218 (to D.M.R.) from the National Health and Medical Research Council of Australia.

	Footnotes

 
Abbreviations: ActRI, Type I activin receptor; ActRII, type II activin receptor; BMP, bone morphogenetic protein; FAST, forkhead activin signal transducer; h, human; GCT, granulosa cell tumor; InhBP, inhibin binding protein; LOH, loss of heterozygosity; R-smad, receptor-regulated Smad; SARA, Smad anchor for receptor activation; SV40, simian virus 40.

	References

Top Abstract I. Introduction II. Activin and Inhibin:... III. Activin and Inhibin... IV. Endocrine and Other... V. Summary References

 

1. Massague J 1998 TGF-ß signal transduction. Annu Rev Biochem 67:753–791[CrossRef][Medline]
2. Piek E, Heldin CH, Ten Dijke P 1999 Specificity, diversity, and regulation in TGF-ß superfamily signaling. FASEB J 13:2105–2124[Abstract/Free Full Text]
3. Vale W, Hseuh A, Rivier C, Yu J 1990 The inhibin/activin family of hormones and growth factors. In: Sporn M, Roberts A, eds. Peptide growth factors and their receptors: handbook of experimental physiology. Berlin: Springer-Verlag; vol 95:211–248
4. Mather JP, Moore A, Li RH 1997 Activins, inhibins, and follistatins: further thoughts on a growing family of regulators. Proc Soc Exp Biol Med 215:209–222[CrossRef][Medline]
5. Hotten G, Niedhardt H, Schneider C, Pohl J 1995 Cloning of a new member of the TGF-ß superfamily: a putative new activin ßC chain. Biochem Biophys Res Commun 206:608–613[CrossRef][Medline]
6. Oda S, Nishimatsu S, Murakami K, Ueno N 1995 Molecular cloning and functional analysis of a new activin ß subunit: a dorsal mesoderm-inducing activity in Xenopus. Biochem Biophys Res Commun 210:581–588[CrossRef][Medline]
7. Schmitt J, Hotten G, Jenkins NA, Gilbert DJ, Copeland NG, Pohl J, Schrewe H 1996 Structure, chromosomal localization, and expression analysis of the mouse inhibin/activin ßC (Inhbc) gene. Genomics 32:358–366[CrossRef][Medline]
8. Fang J, Yin W, Smiley E, Wang SQ, Bonadio J 1996 Molecular cloning of the mouse activin ßE subunit gene. Biochem Biophys Res Commun 228:669–674[CrossRef][Medline]
9. Fang J, Wang SQ, Smiley E, Bonadio J 1997 Genes coding for mouse activin ßC and ßE are closely linked and exhibit a liver-specific expression pattern in adult tissues. Biochem Biophys Res Commun 231:655–661[CrossRef][Medline]
10. Mellor SL, Cranfield M, Ries R, Pedersen J, Cancilla B, de Kretser DM, Groome N, Mason AJ, Risbridger GP 2000 Localization of activin ßA, ßA and ßC subunits in human prostate and evidence for formation of new activin heterodimers of ßC subunit. J Clin Endocrinol Metab 85:4851–4858[Abstract/Free Full Text]
11. Lau AL, Kumar TR, Nishimori K, Bonadio J, Matzuk MM 2000 Activin ßC and ßE genes are not essential for mouse liver growth, differentiation, and regeneration. Mol Cell Biol 20:6127–6137[Abstract/Free Full Text]
12. Sugino K, Nakamura T, Takio K, Miyamoto K, Hasegawa Y, Igarashi M, Titani K, Sugino H 1992 Purification and characterization of high molecular weight forms of inhibin from bovine follicular fluid. Endocrinology 130:789–796[Abstract/Free Full Text]
13. Robertson DM, Giacometti M, Foulds LM, Lahnstein J, Goss NH, Hearn MT, de Kretser DM 1989 Isolation of inhibin subunit precursor proteins from bovine follicular fluid. Endocrinology 125:2141–2149[Abstract/Free Full Text]
14. McLachlan RI, Robertson DM, Burger HG, de Kretser DM 1986 The radioimmunoassay of bovine and human follicular fluid and serum inhibin. Mol Cell Endocrinol 46:175–185[CrossRef][Medline]
15. Mason AJ, Farnworth PG, Sullivan J 1996 Characterization and determination of the biological activities of noncleavable high molecular weight forms of inhibin A and activin A. Mol Endocrinol 10:1055–1065[Abstract/Free Full Text]
16. Muttukrishna S, Child TJ, Groome NP, Ledger WL 1997 Source of circulating levels of inhibin A, pro C-containing inhibins and activin A in early pregnancy. Hum Reprod 12:1089–1093
17. Groome NP, Illingworth PJ, O’Brien M, Pai R, Rodger FE, Mather JP, McNeilly AS 1996 Measurement of dimeric inhibin B throughout the human menstrual cycle. J Clin Endocrinol Metab 81:1401–1405[Abstract]
18. Groome NP, Illingworth PJ, O’Brien M, Priddle J, Weaver K, McNeilly AS 1995 Quantification of inhibin pro-C-containing forms in human serum by a new ultrasensitive two-site enzyme-linked immunosorbent assay. J Clin Endocrinol Metab 80:2926–2932[Abstract/Free Full Text]
19. Muttukrishna S, Fowler PA, George L, Groome NP, Knight PG 1996 Changes in peripheral serum levels of total activin A during the human menstrual cycle and pregnancy. J Clin Endocrinol Metab 81:3328–3334[Abstract]
20. Robertson DM, Cahir N, Burger HG, Mamers P, McCloud PI, Pettersson K, McGuckin M 1999 Combined inhibin and CA125 assays in the detection of ovarian cancer. Clin Chem 45:651–658[Abstract/Free Full Text]
21. Gaddy-Kurten D, Tsuchida K, Vale W 1995 Activins and the receptor serine kinase superfamily. Recent Prog Horm Res 50:109–129
22. Heldin CH, Miyazono K, ten Dijke P 1997 TGF-ß signaling from cell membrane to nucleus through SMAD proteins. Nature 390:465–471[CrossRef][Medline]
23. Itoh S, Itoh F, Goumans MJ, Ten Dijke P 2000 Signaling of transforming growth factor-ß family members through Smad proteins. Eur J Biochem 267:6954–6967[Medline]
24. Lebrun JJ, Takabe K, Chen Y, Vale W 1999 Roles of pathway-specific and inhibitory Smads in activin receptor signaling. Mol Endocrinol 13:15–23[Abstract/Free Full Text]
25. Derynck R, Zhang Y, Feng XH 1998 Smads: transcriptional activators of TGF-ß responses. Cell 95:737–740[CrossRef][Medline]
26. Tsukazaki T, Chiang TA, Davison AF, Attisano L, Wrana JL 1998 SARA, a FYVE domain protein that recruits Smad2 to the TGFß receptor. Cell 95:779–791[CrossRef][Medline]
27. Wrana JL, Attisano L 2000 The Smad pathway. Cytokine Growth Factor Rev 11:5–13[CrossRef][Medline]
28. Attisano L, Wrana JL 2000 Smads as transcriptional co-modulators. Curr Opin Cell Biol 12:235–243[CrossRef][Medline]
29. Chen X, Weisberg E, Fridmacher V, Watanabe M, Naco G, Whitman M 1997 Smad4 and FAST-1 in the assembly of activin-responsive factor. Nature 389:85–89[CrossRef][Medline]
30. Chen X, Rubock MJ, Whitman M 1996 A transcriptional partner for MAD proteins in TGF-ß signalling. Nature 383:691–696[CrossRef][Medline]
31. Labbe E, Silvestri C, Hoodless PA, Wrana JL, Attisano L 1998 Smad2 and Smad3 positively and negatively regulate TGF ß-dependent transcription through the forkhead DNA-binding protein FAST2. Mol Cell 2:109–120[CrossRef][Medline]
32. ten Dijke P, Miyazono K, Heldin CH 2000 Signaling inputs converge on nuclear effectors in TGF-ß signaling. Trends Biochem Sci 25:64–70[CrossRef][Medline]
33. Hertan R, Farnworth PG, Fitzsimmons KL, Robertson DM 1999 Identification of high affinity binding sites for inhibin on ovine pituitary cells in culture. Endocrinology 140:6–12[Abstract/Free Full Text]
34. Robertson DM, Hertan R, Farnworth PG 2000 Is the action of inhibin mediated via a unique receptor? Rev Reprod 5:131–135[Abstract]
35. Xu J, McKeehan K, Matsuzaki K, McKeehan WL 1995 Inhibin antagonizes inhibition of liver cell growth by activin by a dominant-negative mechanism. J Biol Chem 270:6308–6313[Abstract/Free Full Text]
36. Martens JW, de Winter JP, Timmerman MA, McLuskey A, van Schaik RH, Themmen AP, de Jong FH 1997 Inhibin interferes with activin signaling at the level of the activin receptor complex in Chinese hamster ovary cells. Endocrinology 138:2928–2936[Abstract/Free Full Text]
37. Lewis KA, Gray PC, Blount AL, MacConell LA, Wiater E, Bilezikjian LM, Vale W 2000 Betaglycan binds inhibin and can mediate functional antagonism of activin signalling. Nature 404:411–414[CrossRef][Medline]
38. Chong H, Pangas SA, Bernard DJ, Wang E, Gitch J, Chen W, Draper LB, Cox ET, Woodruff TK 2000 Structure and expression of a membrane component of the inhibin receptor system. Endocrinology 141:2600–2607[Abstract/Free Full Text]
39. Matzuk MM 2000 In search of binding–identification of inhibin receptors. Endocrinology 141:2281–2284[Free Full Text]
40. Pangas SA, Woodruff TK 2000 Activin signal transduction pathways. Trends Endocrinol Metab 11:309–314[CrossRef][Medline]
41. Phillips DJ, de Kretser DM 1998 Follistatin: a multifunctional regulatory protein. Front Neuroendocrinol 19:287–322[CrossRef][Medline]
42. Knight PG 1996 Roles of inhibins, activins, and follistatin in the female reproductive system. Front Neuroendocrinol 17:476–509[CrossRef][Medline]
43. Iemura S, Yamamoto TS, Takagi C, Uchiyama H, Natsume T, Shimasaki S, Sugino H, Ueno N 1998 Direct binding of follistatin to a complex of bone-morphogenetic protein and its receptor inhibits ventral and epidermal cell fates in early Xenopus embryo. Proc Natl Acad Sci USA 95:9337–9342[Abstract/Free Full Text]
44. Tsuchida K, Arai KY, Kuramoto Y, Yamakawa N, Hasegawa Y, Sugino H 2000 Identification and characterization of a novel follistatin-like protein (FSLP) as a binding protein for the TGF-ß family. J Biol Chem 275:40788–40796[Abstract/Free Full Text]
45. Krummen LA, Woodruff TK, DeGuzman G, Cox ET, Baly DL, Mann E, Garg S, Wong WL, Cossum P, Mather JP 1993 Identification and characterization of binding proteins for inhibin and activin in human serum and follicular fluids. Endocrinology 132:431–443[Abstract/Free Full Text]
46. Rabinovici J, Spencer SJ, Jaffe RB 1990 Recombinant human activin-A promotes proliferation of human luteinized preovulatory granulosa cells in vitro. J Clin Endocrinol Metab 71:1396–1398[Abstract/Free Full Text]
47. Miro F, Hillier SG 1996 Modulation of granulosa cell deoxyribonucleic acid synthesis and differentiation by activin. Endocrinology 137:464–468[Abstract]
48. Welt CK, Crowley WF 1998 Activin: an endocrine or paracrine agent? Eur J Endocrinol 139:469–471[CrossRef][Medline]
49. Matzuk MM, Finegold MJ, Su JG, Hsueh AJ, Bradley A 1992 -Inhibin is a tumour-suppressor gene with gonadal specificity in mice. Nature 360:313–319[CrossRef][Medline]
50. Kim SJ, Im YH, Markowitz SD, Bang YJ 2000 Molecular mechanisms of inactivation of TGF-ß receptors during carcinogenesis. Cytokine Growth Factor Rev 11:159–168[CrossRef][Medline]
51. Matzuk MM, Finegold MJ, Mather JP, Krummen L, Lu H, Bradley A 1994 Development of cancer cachexia-like syndrome and adrenal tumors in inhibin-deficient mice. Proc Natl Acad Sci USA 91:8817–8821[Abstract/Free Full Text]
52. Coerver KA, Woodruff TK, Finegold MJ, Mather J, Bradley A, Matzuk MM 1996 Activin signaling through activin receptor type II causes the cachexia-like symptoms in inhibin-deficient mice. Mol Endocrinol 10:534–543[Abstract/Free Full Text]
53. Schwall R, Schmelzer CH, Matsuyama E, Mason AJ 1989 Multiple actions of recombinant activin-A in vivo. Endocrinology 125:1420–1423[Abstract/Free Full Text]
54. Cipriano SC, Chen L, Kumar TR, Matzuk MM 2000 Follistatin is a modulator of gonadal tumor progression and the activin-induced wasting syndrome in inhibin-deficient mice. Endocrinology 141:2319–2327[Abstract/Free Full Text]
55. Shikone T, Matzuk MM, Perlas E, Finegold MJ, Lewis KA, Vale W, Bradley A, Hsueh AJ 1994 Characterization of gonadal sex cord-stromal tumor cell lines from inhibin- and p53-deficient mice: the role of activin as an autocrine growth factor. Mol Endocrinol 8:983–995[Abstract/Free Full Text]
56. Kumar TR, Palapattu G, Wang P, Woodruff TK, Boime I, Byrne MC, Matzuk MM 1999 Transgenic models to study gonadotropin function: the role of follicle-stimulating hormone in gonadal growth and tumorigenesis. Mol Endocrinol 13:851–865[Abstract/Free Full Text]
57. Tanimoto Y, Tanimoto K, Sugiyama F, Horiguchi H, Murakami K, Yagami K, Fukamizu A 1999 Male sterility in transgenic mice expressing activin ßA subunit gene in testis. Biochem Biophys Res Commun 259:699–705[CrossRef][Medline]
58. Matzuk MM, Kumar TR, Shou W, Coerver KA, Lau AL, Behringer RR, Finegold MJ 1996 Transgenic models to study the roles of inhibins and activins in reproduction, oncogenesis, and development. Recent Prog Horm Res 51:123–154
59. Kumar TR, Wang Y, Matzuk MM 1996 Gonadotropins are essential modifier factors for gonadal tumor development in inhibin-deficient mice. Endocrinology 137:4210–4216[Abstract]
60. Risma KA, Clay CM, Nett TM, Wagner T, Yun J, Nilson JH 1995 Targeted overexpression of luteinizing hormone in transgenic mice leads to infertility, polycystic ovaries, and ovarian tumors. Proc Natl Acad Sci USA 92:1322–1326[Abstract/Free Full Text]
61. Kananen K, Markkula M, Rainio E, Su JG, Hsueh AJ, Huhtaniemi IT 1995 Gonadal tumorigenesis in transgenic mice bearing the mouse inhibin -subunit promoter/simian virus T-antigen fusion gene: characterization of ovarian tumors and establishment of gonadotropin-responsive granulosa cell lines. Mol Endocrinol 9:616–627[Abstract/Free Full Text]
62. Kananen K, Markkula M, Mikola M, Rainio EM, McNeilly A, Huhtaniemi I 1996 Gonadectomy permits adrenocortical tumorigenesis in mice transgenic for the mouse inhibin -subunit promoter/simian virus 40 T-antigen fusion gene: evidence for negative autoregulation of the inhibin -subunit gene. Mol Endocrinol 10:1667–1677[Abstract/Free Full Text]
63. Kananen K, Rilianawati, Paukku T, Markkula M, Rainio EM, Huhtanemi I 1997 Suppression of gonadotropins inhibits gonadal tumorigenesis in mice transgenic for the mouse inhibin -subunit promoter/simian virus 40 T-antigen fusion gene. Endocrinology 138:3521–3531[Abstract/Free Full Text]
64. Rilianawati, Kero J, Paukku T, Huhtaniemi I 2000 Long-term testosterone treatment prevents gonadal and adrenal tumorigenesis of mice transgenic for the mouse inhibin- subunit promoter/simian virus 40 T-antigen fusion gene. J Endocrinol 166:77–85[Abstract]
65. Kananen K, Markkula M, el-Hefnawy T, Zhang FP, Paukku T, Su JG, Hsueh AJ, Huhtaniemi I 1996 The mouse inhibin -subunit promoter directs SV40 T-antigen to Leydig cells in transgenic mice. Mol Cell Endocrinol 119:135–146[CrossRef][Medline]
66. Shou W, Woodruff TK, Matzuk MM 1997 Role of androgens in testicular tumor development in inhibin-deficient mice. Endocrinology 138:5000–5005[Abstract/Free Full Text]
67. Matzuk MM, Finegold MJ, Mishina Y, Bradley A, Behringer RR 1995 Synergistic effects of inhibins and Mullerian-inhibiting substance on testicular tumorigenesis. Mol Endocrinol 9:1337–1345[Abstract/Free Full Text]
68. Cipriano SC, Chen L, Burns KH, Koff A, Matzuk MM 2001 Inhibin and p27 interact to regulate gonadal tumorigenesis. Mol Endocrinol 15:985–996[Abstract/Free Full Text]
69. Hahn SA, Schutte M, Hoque AT, Moskaluk CA, da Costa LT, Rozenblum E, Weinstein CL, Fischer A, Yeo CJ, Hruban RH, Kern SE 1996 DPC4, a candidate tumor suppressor gene at human chromosome 18q21.1. Science 271:350–353[Abstract]
70. Markowitz SD, Roberts AB 1996 Tumor suppressor activity of the TGF-ß pathway in human cancers. Cytokine Growth Factor Rev 7:93–102[CrossRef][Medline]
71. Trudeau VL, Matzuk MM, Hache RJ, Renaud LP 1994 Overexpression of activin-ßA subunit mRNA is associated with decreased activin type II receptor mRNA levels in the testes of -inhibin deficient mice. Biochem Biophys Res Commun 203:105–112[CrossRef][Medline]
72. van Schaik RH, Wierikx CD, Timmerman MA, Oomen MH, van Weerden WM, van der Kwast TH, van Steenbrugge GJ, de Jong FH 2000 Variations in activin receptor, inhibin/activin subunit and follistatin mRNAs in human prostate tumour tissues. Br J Cancer 82:112–117[CrossRef][Medline]
73. Su GH, Bansal R, Murphy KM, Montgomery E, Yeo CJ, Hruban RH, Kern SE 2001 ACVR1B (ALK4, activin receptor type 1B) gene mutations in pancreatic carcinoma. Proc Natl Acad Sci USA 98:3254–3257[Abstract/Free Full Text]
74. Breit S, Rossler J, Fotsis T, Schweigerer L 2000 N-myc down-regulates activin A. Biochem Biophys Res Commun 274:405–409[CrossRef][Medline]
75. Mellor SL, Richards MG, Pedersen JS, Robertson DM, Risbridger GP 1998 Loss of the expression and localization of inhibin -subunit in high grade prostate cancer. J Clin Endocrinol Metab 83:969–975[Abstract/Free Full Text]
76. Barton DE, Yang-Feng TL, Mason AJ, Seeburg PH, Francke U 1989 Mapping of genes for inhibin subunits , ßA, and ßB on human and mouse chromosomes and studies of jsd mice. Genomics 5:91–99[CrossRef][Medline]
77. Roijer E, Miyazono K, Astrom AK, Geurts van Kessel A, ten Dijke P, Stenman G 1998 Chromosomal localization of three human genes encoding members of the TGF-ß superfamily of type I serine/threonine kinase receptors. Mamm Genome 9:266–268[CrossRef][Medline]
78. Saretzki G, Hoffmann U, Rohlke P, Psille R, Gaigal T, Keller G, Hofler H, Loning T, Petersen I, Dietel M 1997 Identification of allelic losses in benign, borderline, and invasive epithelial ovarian tumors and correlation with clinical outcome. Cancer 80:1241–1249[CrossRef][Medline]
79. Watson RH, Roy Jr WJ, Davis M, Hitchcock A, Campbell IG 1997 Loss of heterozygosity at the -inhibin locus on chromosome 2q is not a feature of human granulosa cell tumors. Gynecol Oncol 65:387–390[CrossRef][Medline]
80. Alers JC, Rochat J, Krijtenburg PJ, Hop WC, Kranse R, Rosenberg C, Tanke HJ, Schroder FH, van Dekken H 2000 Identification of genetic markers for prostatic cancer progression. Lab Invest 80:931–942[Medline]
81. Suarez BK, Lin J, Burmester JK, Broman KW, Weber JL, Banerjee TK, Goddard KA, Witte JS, Elston RC, Catalona WJ 2000 A genome screen of multiplex sibships with prostate cancer. Am J Hum Genet 66:933–944[CrossRef][Medline]
82. Ala-Fossi SL, Aine R, Punnonen R, Maenpaa J 2000 Is potential to produce inhibins related to prognosis in ovarian granulosa cell tumors? Eur J Gynaecol Oncol 21:187–189[Medline]
83. Gebhart JB, Roche PC, Keeney GL, Lesnick TG, Podratz KC 2000 Assessment of inhibin and p53 in granulosa cell tumors of the ovary. Gynecol Oncol 77:232–236[CrossRef][Medline]
84. Arnold N, Hagele L, Walz L, Schempp W, Pfisterer J, Bauknecht T, Kiechle M 1996 Overrepresentation of 3q and 8q material and loss of 18q material are recurrent findings in advanced human ovarian cancer. Genes Chromosomes Cancer 16:46–54[CrossRef][Medline]
85. Bondestam J, Horelli-Kuitunen N, Hilden K, Ritvos O, Aaltonen J 1999 Assignment of ACVR2 and ACVR2B the human activin receptor type II and IIB genes to chromosome bands 2q22.2q23.3 and 3p22 and the human follistatin gene (FST) to chromosome 5q11.2 by FISH. Cytogenet Cell Genet 87:219–220[CrossRef][Medline]
86. Ishikawa S, Kai M, Murata Y, Tamari M, Daigo Y, Murano T, Ogawa M, Nakamura Y 1998 Genomic organization and mapping of the human activin receptor type IIB (hActR-IIB) gene. J Hum Genet 43:132–134[CrossRef][Medline]
87. Hahn SA, Hoque AT, Moskaluk CA, da Costa LT, Schutte M, Rozenblum E, Seymour AB, Weinstein CL, Yeo CJ, Hruban RH, Kern SE 1996 Homozygous deletion map at 18q21.1 in pancreatic cancer. Cancer Res 56:490–494[Abstract/Free Full Text]
88. Nakao A, Roijer E, Imamura T, Souchelnytskyi S, Stenman G, Heldin CH, ten Dijke P 1997 Identification of Smad2, a human Mad-related protein in the transforming growth factor ß signaling pathway. J Biol Chem 272:2896–900[Abstract/Free Full Text]
89. Roijer E, Moren A, ten Dijke P, Stenman G 1998 Assignment1 of the Smad7 gene (MADH7) to human chromosome 18q21.1 by fluorescence in situ hybridization. Cytogenet Cell Genet 81:189–190[CrossRef][Medline]
90. Tanner MM, Karhu RA, Nupponen NN, Borg A, Baldetorp B, Pejovic T, Ferno M, Killander D, Isola JJ 1998 Genetic aberrations in hypodiploid breast cancer: frequent loss of chromosome 4 and amplification of cyclin D1 oncogene. Am J Pathol 153:191–199[Abstract/Free Full Text]
91. Richard F, Pacyna-Gengelbach M, Schluns K, Fleige B, Winzer KJ, Szymas J, Dietel M, Petersen I, Schwendel A 2000 Patterns of chromosomal imbalances in invasive breast cancer. Int J Cancer 89:305–310[CrossRef][Medline]
92. Aubele M, Mattis A, Zitzelsberger H, Walch A, Kremer M, Welzl G, Hofler H, Werner M 2000 Extensive ductal carcinoma in situ with small foci of invasive ductal carcinoma: evidence of genetic resemblance by CGH. Int J Cancer 85:82–86[CrossRef][Medline]
93. Braga E, Pugacheva E, Bazov I, Ermilova V, Kazubskaya T, Mazurenko N, Kisseljov F, Liu J, Garkavtseva R, Zabarovsky E, Kisselev L 1999 Comparative allelotyping of the short arm of human chromosome 3 in epithelial tumors of four different types. FEBS Lett 454:215–219[CrossRef][Medline]
94. Euhus DM, Maitra A, Wistuba, II, Alberts A, Albores-Saavedra J, Gazdar AF 1999 Loss of heterozygosity at 3p in benign lesions preceding invasive breast cancer. J Surg Res 83:13–18[CrossRef][Medline]
95. Fullwood P, Marchini S, Rader JS, Martinez A, Macartney D, Broggini M, Morelli C, Barbanti-Brodano G, Maher ER, Latif F 1999 Detailed genetic and physical mapping of tumor suppressor loci on chromosome 3p in ovarian cancer. Cancer Res 59:4662–4667[Abstract/Free Full Text]
96. Huiping C, Sigurgeirsdottir JR, Jonasson JG, Eiriksdottir G, Johannsdottir JT, Egilsson V, Ingvarsson S 1999 Chromosome alterations and E-cadherin gene mutations in human lobular breast cancer. Br J Cancer 81:1103–1110[CrossRef][Medline]
97. Isola J, Chu L, DeVries S, Matsumura K, Chew K, Ljung BM, Waldman FM 1999 Genetic alterations in ERBB2-amplified breast carcinomas. Clin Cancer Res 5:4140–4145[Abstract/Free Full Text]
98. Lu YJ, Birdsall S, Osin P, Gusterson B, Shipley J 1997 Phyllodes tumors of the breast analyzed by comparative genomic hybridization and association of increased 1q copy number with stromal overgrowth and recurrence. Genes Chromosomes Cancer 20:275–281[CrossRef][Medline]
99. Malamou-Mitsi VD, Syrrou M, Georgiou I, Pagoulatos G, Agnantis NJ 1999 Analysis of chromosomal aberrations in breast cancer by comparative genomic hybridization (CGH): correlation with histoprognostic variables and c-erbB-2 immunoexpression. J Exp Clin Cancer Res 18:357–361[Medline]
100. Matsumoto S, Minobe K, Utada Y, Furukawa K, Onda M, Sakamoto G, Kasumi F, Nakamura Y, Emi M 2000 Loss of heterozygosity at 3p24–p25 as a prognostic factor in breast cancer. Cancer Lett 152:63–69[CrossRef][Medline]
101. Moinfar F, Man YG, Bratthauer GL, Ratschek M, Tavassoli FA 2000 Genetic abnormalities in mammary ductal intraepithelial neoplasia-flat type ("clinging ductal carcinoma in situ"): a simulator of normal mammary epithelium. Cancer 88:2072–2081[CrossRef][Medline]
102. Moinfar F, Man YG, Arnould L, Bratthauer GL, Ratschek M, Tavassoli FA 2000 Concurrent and independent genetic alterations in the stromal and epithelial cells of mammary carcinoma: implications for tumorigenesis. Cancer Res 60:2562–2566[Abstract/Free Full Text]
103. Sekido Y, Ahmadian M, Wistuba, II, Latif F, Bader S, Wei MH, Duh FM, Gazdar AF, Lerman MI, Minna JD 1998 Cloning of a breast cancer homozygous deletion junction narrows the region of search for a 3p21.3 tumor suppressor gene. Oncogene 16:3151–3157[CrossRef][Medline]
104. Matsumoto S, Kasumi F, Sakamoto G, Onda M, Nakamura Y, Emi M 1997 Detailed deletion mapping of chromosome arm 3p in breast cancers: a 2-cM region on 3p14.3–21.1 and a 5-cM region on 3p24.3–25.1 commonly deleted in tumors. Genes Chromosomes Cancer 20:268–274[CrossRef][Medline]
105. Aubele MM, Cummings MC, Mattis AE, Zitzelsberger HF, Walch AK, Kremer M, Hofler H, Werner M 2000 Accumulation of chromosomal imbalances from intraductal proliferative lesions to adjacent in situ and invasive ductal breast cancer. Diagn Mol Pathol 9:14–19[CrossRef][Medline]
106. Hahn SA, Seymour AB, Hoque AT, Schutte M, da Costa LT, Redston MS, Caldas C, Weinstein CL, Fischer A, Yeo CJ, Hruban RH, Kern SE 1995 Allelotype of pancreatic adenocarcinoma using xenograft enrichment. Cancer Res 55:4670–4675[Abstract/Free Full Text]
107. Hessman O, Lindberg D, Einarsson A, Lillhager P, Carling T, Grimelius L, Eriksson B, Akerstrom G, Westin G, Skogseid B 1999 Genetic alterations on 3p, 11q13, and 18q in nonfamilial and MEN 1-associated pancreatic endocrine tumors. Genes Chromosomes Cancer 26:258–264[CrossRef][Medline]
108. Fujii H, Inagaki M, Kasai S, Miyokawa N, Tokusashi Y, Gabrielson E, Hruban RH 1997 Genetic progression and heterogeneity in intraductal papillary-mucinous neoplasms of the pancreas. Am J Pathol 151:1447–1454[Abstract]
109. Bartsch D, Hahn SA, Danichevski KD, Ramaswamy A, Bastian D, Galehdari H, Barth P, Schmiegel W, Simon B, Rothmund M 1999 Mutations of the DPC4/Smad4 gene in neuroendocrine pancreatic tumors. Oncogene 18:2367–2371[CrossRef][Medline]
110. Yamano M, Fujii H, Takagaki T, Kadowaki N, Watanabe H, Shirai T 2000 Genetic progression and divergence in pancreatic carcinoma. Am J Pathol 156:2123–2133[Abstract/Free Full Text]
111. Schleger C, Arens N, Zentgraf H, Bleyl U, Verbeke C 191 2000 Identification of frequent chromosomal aberrations in ductal adenocarcinoma of the pancreas by comparative genomic hybridization (CGH). J Pathol 27–32
112. Fukushige S, Furukawa T, Satoh K, Sunamura M, Kobari M, Koizumi M, Horii A 1998 Loss of chromosome 18q is an early event in pancreatic ductal tumorigenesis. Cancer Res 58:4222–4226[Abstract/Free Full Text]
113. Riggins GJ, Thiagalingam S, Rozenblum E, Weinstein CL, Kern SE, Hamilton SR, Willson JK, Markowitz SD, Kinzler KW, Vogelstein B 1996 Mad-related genes in the human. Nat Genet 13:347–349[CrossRef][Medline]
114. Zhao J, Speel EJ, Muletta-Feurer S, Rutimann K, Saremaslani P, Roth J, Heitz PU, Komminoth P 1999 Analysis of genomic alterations in sporadic adrenocortical lesions: gain of chromosome 17 is an early event in adrenocortical tumorigenesis. Am J Pathol 155:1039–1045[Abstract/Free Full Text]
115. Hermsen MA, Baak JP, Meijer GA, Weiss JM, Walboomers JW, Snijders PJ, van Diest PJ 1998 Genetic analysis of 53 lymph node-negative breast carcinomas by CGH and relation to clinical, pathological, morphometric, and DNA cytometric prognostic factors. J Pathol 186:356–362[CrossRef][Medline]
116. Loveday RL, Greenman J, Simcox DL, Speirs V, Drew PJ, Monson JR, Kerin MJ 2000 Genetic changes in breast cancer detected by comparative genomic hybridisation. Int J Cancer 86:494–500[CrossRef][Medline]
117. Latil A, Fournier G, Cussenot O, Lidereau R 1996 Differential chromosome allelic imbalance in the progression of human prostate cancer. J Urol 156:2079–2083[CrossRef][Medline]
118. Tirkkonen M, Johannsson O, Agnarsson BA, Olsson H, Ingvarsson S, Karhu R, Tanner M, Isola J, Barkardottir RB, Borg A, Kallioniemi OP 1997 Distinct somatic genetic changes associated with tumor progression in carriers of BRCA1 and BRCA2 germ-line mutations. Cancer Res 57:1222–1227[Abstract/Free Full Text]
119. Moore E, Magee H, Coyne J, Gorey T, Dervan PA 1999 Widespread chromosomal abnormalities in high-grade ductal carcinoma in situ of the breast: comparative genomic hybridization study of pure high-grade DCIS. J Pathol 187:403–409[CrossRef][Medline]
120. Rigaud G, Moore PS, Zamboni G, Orlandini S, Taruscio D, Paradisi S, Lemoine NR, Kloppel G, Scarpa A 2000 Allelotype of pancreatic acinar cell carcinoma. Int J Cancer 88:772–777[CrossRef][Medline]
121. Cher ML, Bova GS, Moore DH, Small EJ, Carroll PR, Pin SS, Epstein JI, Isaacs WB, Jensen RH 1996 Genetic alterations in untreated metastases and androgen-independent prostate cancer detected by comparative genomic hybridization and allelotyping. Cancer Res 56:3091–102[Abstract/Free Full Text]
122. Bieche I, Khodja A, Driouch K, Lidereau R 1997 Genetic alteration mapping on chromosome 7 in primary breast cancer. Clin Cancer Res 3:1009–1016[Abstract]
123. Qian J, Jenkins RB, Bostwick DG 1999 Genetic and chromosomal alterations in prostatic intraepithelial neoplasia and carcinoma detected by fluorescence in situ hybridization. Eur Urol 35:479–483[CrossRef][Medline]
124. Alers JC, Krijtenburg PJ, Hop WC, Bolle WA, Schroder FH, van der Kwast TH, Bosman FT, van Dekken H 1998 Longitudinal evaluation of cytogenetic aberrations in prostatic cancer: tumors that recur in time display an intermediate genetic status between non-persistent and metastatic tumors. J Pathol 185:273–283[CrossRef][Medline]
125. Alers JC, Krijtenburg PJ, Rosenberg C, Hop WC, Verkerk AM, Schroder FH, van der Kwast TH, Bosman FT, van Dekken H 1997 Interphase cytogenetics of prostatic tumor progression: specific chromosomal abnormalities are involved in metastasis to the bone. Lab Invest 77:437–448[Medline]
126. Kurose K, Iida A, Araki T, Sakamoto G, Kasumi F, Nakamura Y, Emi M 1998 Frequent allelic loss at 7p14–15 associated with aggressive histologic types of breast cancer. Jpn J Cancer Res 89:533–538[Medline]
127. Nagai H, Pineau P, Tiollais P, Buendia MA, Dejean A 1997 Comprehensive allelotyping of human hepatocellular carcinoma. Oncogene 14:2927–2933[CrossRef][Medline]
128. Ge K, Minhas F, Duhadaway J, Mao NC, Wilson D, Buccafusca R, Sakamuro D, Nelson P, Malkowicz SB, Tomaszewski J, Prendergast GC 2000 Loss of heterozygosity and tumor suppressor activity of Bin1 in prostate carcinoma. Int J Cancer 86:155–161[CrossRef][Medline]
129. Lothe RA, Peltomaki P, Tommerup N, Fossa SD, Stenwig AE, Borresen AL, Nesland JM 1995 Molecular genetic changes in human male germ cell tumors. Lab Invest 73:606–614[Medline]
130. Pere H, Tapper J, Wahlstrom T, Knuutila S, Butzow R 1998 Distinct chromosomal imbalances in uterine serous and endometrioid carcinomas. Cancer Res 58:892–895[Abstract/Free Full Text]
131. Maitra A, Tavassoli FA, Albores-Saavedra J, Behrens C, Wistuba, II, Bryant D, Weinberg AG, Rogers BB, Saboorian MH, Gazdar AF 1999 Molecular abnormalities associated with secretory carcinomas of the breast. Hum Pathol 30:1435–1440[CrossRef][Medline]
132. Chung DC, Smith AP, Louis DN, Graeme-Cook F, Warshaw AL, Arnold A 1997 A novel pancreatic endocrine tumor suppressor gene locus on chromosome 3p with clinical prognostic implications. J Clin Invest 100:404–410[Medline]
133. Dahiya R, McCarville J, Hu W, Lee C, Chui RM, Kaur G, Deng G 1997 Chromosome 3p24–26 and 3p22–12 loss in human prostatic adenocarcinoma. Int J Cancer 71:20–25[CrossRef][Medline]
134. Schwendel A, Richard F, Langreck H, Kaufmann O, Lage H, Winzer KJ, Petersen I, Dietel M 1998 Chromosome alterations in breast carcinomas: frequent involvement of DNA losses including chromosomes 4q and 21q. Br J Cancer 78:806–811[Medline]
135. Imyanitov EN, Togo AV, Suspitsin EN, Grigoriev MY, Pozharisski KM, Turkevich EA, Hanson KP, Hayward NK, Chenevix-Trench G, Theillet C, Lavin MF 2000 Evidence for microsatellite instability in bilateral breast carcinomas. Cancer Lett 154:9–17[CrossRef][Medline]
136. Saric T, Brkanac Z, Troyer DA, Padalecki SS, Sarosdy M, Williams K, Abadesco L, Leach RJ, O’Connell P 1999 Genetic pattern of prostate cancer progression. Int J Cancer 81:219–224[CrossRef][Medline]
137. Sattler HP, Rohde V, Bonkhoff H, Zwergel T, Wullich B 1999 Comparative genomic hybridization reveals DNA copy number gains to frequently occur in human prostate cancer. Prostate 39:79–86[CrossRef][Medline]
138. Zitzelsberger H, Engert D, Walch A, Kulka U, Aubele M, Hofler H, Bauchinger M, Werner M 2001 Chromosomal changes during development and progression of prostate adenocarcinomas. Br J Cancer 84:202–208[CrossRef][Medline]
139. Schutte M, Hruban RH, Hedrick L, Cho KR, Nadasdy GM, Weinstein CL, Bova GS, Isaacs WB, Cairns P, Nawroz H, Sidransky D, Casero Jr RA, Meltzer PS, Hahn SA, Kern SE 1996 DPC4 gene in various tumor types. Cancer Res 56:2527–2530[Abstract/Free Full Text]
140. Huiping C, Eiriksdottir G, Sigurdsson A, Sigurgeirsdottir JR, Barkardottir RB, Egilsson V, Ingvarsson S 1998 High frequency of LOH at chromosome 18q in human breast cancer: association with high S-phase fraction and low progesterone receptor content. Anticancer Res 18:1031–1036[Medline]
141. Radford DM, Fair KL, Phillips NJ, Ritter JH, Steinbrueck T, Holt MS, Donis-Keller H 1995 Allelotyping of ductal carcinoma in situ of the breast: deletion of loci on 8p, 13q, 16q, 17p and 17q. Cancer Res 55:3399–405[Abstract/Free Full Text]
142. Tirkkonen M, Tanner M, Karhu R, Kallioniemi A, Isola J, Kallioniemi OP 1998 Molecular cytogenetics of primary breast cancer by CGH. Genes Chromosomes Cancer 21:177–184[CrossRef][Medline]
143. Tsuda H, Fukutomi T, Hirohashi S 1995 Pattern of gene alterations in intraductal breast neoplasms associated with histological type and grade. Clin Cancer Res 1:261–267[Abstract]
144. Yokota T, Matsumoto S, Yoshimoto M, Kasumi F, Akiyama F, Sakamoto G, Nakamura Y, Emi M 1997 Mapping of a breast cancer tumor suppressor gene locus to a 4-cM interval on chromosome 18q21. Jpn J Cancer Res 88:959–964[CrossRef][Medline]
145. Tsuda H, Sakamaki C, Tsugane S, Fukutomi T, Hirohashi S 1998 Prognostic significance of accumulation of gene and chromosome alterations and histological grade in node-negative breast carcinoma. Jpn J Clin Oncol 28:5–11[Abstract/Free Full Text]
146. Jenkins R, Takahashi S, DeLacey K, Bergstralh E, Lieber M 1998 Prognostic significance of allelic imbalance of chromosome arms 7q, 8p, 16q, and 18q in stage T3N0 M0 prostate cancer. Genes Chromosomes Cancer 21:131–143[CrossRef][Medline]
147. Ueda T, Komiya A, Emi M, Suzuki H, Shiraishi T, Yatani R, Masai M, Yasuda K, Ito H 1997 Allelic losses on 18q21 are associated with progression and metastasis in human prostate cancer. Genes Chromosomes Cancer 20:140–147[CrossRef][Medline]
148. Crundwell MC, Chughtai S, Knowles M, Takle L, Luscombe M, Neoptolemos JP, Morton DG, Phillips SM 1996 Allelic loss on chromosomes 8p, 22q and 18q (DCC) in human prostate cancer. Int J Cancer 69:295–300[CrossRef][Medline]
149. Visakorpi T, Kallioniemi AH, Syvanen AC, Hyytinen ER, Karhu R, Tammela T, Isola JJ, Kallioniemi OP 1995 Genetic changes in primary and recurrent prostate cancer by comparative genomic hybridization. Cancer Res 55:342–347[Abstract/Free Full Text]
150. Jaatinen TA, Penttila TL, Kaipia A, Ekfors T, Parvinen M, Toppari J 1994 Expression of inhibin , ßA and ßB messenger ribonucleic acids in the normal human ovary and in polycystic ovarian syndrome. J Endocrinol 143:127–137[Abstract/Free Full Text]
151. Roberts VJ, Barth S, el-Roeiy A, Yen SS 1993 Expression of inhibin/activin subunits and follistatin messenger ribonucleic acids and proteins in ovarian follicles and the corpus luteum during the human menstrual cycle. J Clin Endocrinol Metab 77:1402–1410[Abstract]
152. Yamoto M, Minami S, Nakano R, Kobayashi M 1992 Immunohistochemical localization of inhibin/activin subunits in human ovarian follicles during the menstrual cycle. J Clin Endocrinol Metab 74:989–993[Abstract]
153. Burger HG, Cahir N, Robertson DM, Groome NP, Dudley E, Green A, Dennerstein L 1998 Serum inhibins A and B fall differentially as FSH rises in perimenopausal women. Clin Endocrinol (Oxf) 48:809–813[CrossRef][Medline]
154. Baird DT, Smith KB 1993 Inhibin and related peptides in the regulation of reproduction. Oxf Rev Reprod Biol 15:191–232[Medline]
155. Burger HGI, 1–20 1992 Inhibin. Reprod Med Rev 1:1–20
156. Blaakaer J, Bennett P, Micic S, Toftager-Larsen K, Hording U, Bock JE, Lebech PE 1993 The post-operative gonadotropin level in post-menopausal women with epithelial ovarian cancer. Eur J Obstet Gynecol Reprod Biol 52:111–116[CrossRef][Medline]
157. Burger HG, Robertson DM, Cahir N, Mamers P, Healy DL, Jobling T, Groome N 1996 Characterization of inhibin immunoreactivity in post-menopausal women with ovarian tumours. Clin Endocrinol (Oxf) 44:413–418[CrossRef][Medline]
158. Cooke I, O’Brien M, Charnock FM, Groome N, Ganesan TS 1995 Inhibin as a marker for ovarian cancer. Br J Cancer 71:1046–1050[Medline]
159. De Jong FH, Grootenhuis AJ, Steenbergen J, van Sluijs FJ, Foekens JA, ten Kate FJ, Oosterhuis JW, Lamberts SW, Klijn JG 1990 Inhibin immunoreactivity in gonadal and non-gonadal tumors. J Steroid Biochem Mol Biol 37:863–866[CrossRef][Medline]
160. Healy DL, Mamers P, Bangah M, Burger HG 1993 Clinical and pathophysiological aspects of inhibin. Hum Reprod 8(Suppl 2):138–140
161. Jobling T, Mamers P, Healy DL, MacLachlan V, Burger HG, Quinn M, Rome R, Day AJ 1994 A prospective study of inhibin in granulosa cell tumors of the ovary. Gynecol Oncol 55:285–289[CrossRef][Medline]
162. Petraglia F, Florio P, Luisi S, Gallo R, Gadducci A, Vigano P, Di Blasio AM, Genazzani AR, Vale W 1998 Expression and secretion of inhibin and activin in normal and neoplastic uterine tissues: high levels of serum activin A in women with endometrial and cervical carcinoma. J Clin Endocrinol Metab 83:1194–200[Abstract/Free Full Text]
163. Silverman LA, Gitelman SE 1996 Immunoreactive inhibin, Mullerian inhibitory substance, and activin as biochemical markers for juvenile granulosa cell tumors. J Pediatr 129:918–921[CrossRef][Medline]
164. Sluijmer AV, Heineman MJ, Evers JL, de Jong FH 1993 Peripheral vein, ovarian vein and ovarian tissue levels of inhibin in a postmenopausal patient with a granulosa cell tumour. Acta Endocrinol (Copenh) 129:311–314[Abstract/Free Full Text]
165. Yamashita K, Yamoto M, Shikone T, Minami S, Imai M, Nishimori K, Nakano R 1997 Production of inhibin A and inhibin B in human ovarian sex cord stromal tumors. Am J Obstet Gynecol 177:1450–1457[CrossRef][Medline]
166. Zhang H, Vollmer M, De Geyter M, Litzistorf Y, Ladewig A, Durrenberger M, Guggenheim R, Miny P, Holzgreve W, De Geyter C 2000 Characterization of an immortalized human granulosa cell line (COV434). Mol Hum Reprod 6:146–153[Abstract/Free Full Text]
167. Robertson DM, Cahir N, Burger HG, Mamers P, Groome N 1999 Inhibin forms in serum from postmenopausal women with ovarian cancers. Clin Endocrinol (Oxf) 50:381–386[CrossRef][Medline]
168. Zheng W, Sung CJ, Hanna I, DePetris G, Lambert-Messerlian G, Steinhoff M, Lauchlan SC 1997 And ß subunits of inhibin/activin as sex cord-stromal differentiation markers. Int J Gynecol Pathol 16:263–271[Medline]
169. Fuller PJ, Chu S, Jobling T, Mamers P, Healy DL, Burger HG 1999 Inhibin subunit gene expression in ovarian cancer. Gynecol Oncol 73:273–279[CrossRef][Medline]
170. Arora DS, Cooke IE, Ganesan TS, Ramsdale J, Manek S, Charnock FM, Groome NP, Wells M 1997 Immunohistochemical expression of inhibin/activin subunits in epithelial and granulosa cell tumors of the ovary. J Pathol 181:413–418[CrossRef][Medline]
171. Choi YL, Kim HS, Ahn G 2000 Immunoexpression of inhibin subunit, inhibin/activin ßA subunit and CD99 in ovarian tumors. Arch Pathol Lab Med 124:563–569[Medline]
172. Flemming P, Wellmann A, Maschek H, Lang H, Georgii A 1995 Monoclonal antibodies against inhibin represent key markers of adult granulosa cell tumors of the ovary even in their metastases: a report of three cases with late metastasis, being previously misinterpreted as hemangiopericytoma. Am J Surg Pathol 19:927–933[Medline]
173. Flemming P, Grothe W, Maschek H, Petry KU, Wellmann A, Georgii A 1996 The site of inhibin production in ovarian neoplasms. Histopathology 29:465–468[CrossRef][Medline]
174. Gurusinghe CJ, Healy DL, Jobling T, Mamers P, Burger HG 1995 Inhibin and activin are demonstrable by immunohistochemistry in ovarian tumor tissue. Gynecol Oncol 57:27–32[CrossRef][Medline]
175. Hildebrandt RH, Rouse RV, Longacre TA 1997 Value of inhibin in the identification of granulosa cell tumors of the ovary. Hum Pathol 28:1387–1395[CrossRef][Medline]
176. Kommoss F, Oliva E, Bhan AK, Young RH, Scully RE 1998 Inhibin expression in ovarian tumors and tumor-like lesions: an immunohistochemical study. Mod Pathol 11:656–664[Medline]
177. Matias-Guiu X, Prat J 1998 -Inhibin immunostaining in diagnostic pathology. Adv Anat Pathol 5:263–267[CrossRef][Medline]
178. McCluggage WG, Burton J, Maxwell P, Sloan JM 1998 Immunohistochemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against inhibin. J Clin Pathol 51:114–116[Abstract]
179. Pelkey TJ, Frierson Jr HF, Mills SE, Stoler MH 1998 The diagnostic utility of inhibin staining in ovarian neoplasms. Int J Gynecol Pathol 17:97–105[Medline]
180. Riopel MA, Perlman EJ, Seidman JD, Kurman RJ, Sherman ME 1998 Inhibin and epithelial membrane antigen immunohistochemistry assist in the diagnosis of sex cord-stromal tumors and provide clues to the histogenesis of hypercalcemic small cell carcinomas. Int J Gynecol Pathol 17:46–53[Medline]
181. Rishi M, Howard LN, Bratthauer GL, Tavassoli FA 1997 Use of monoclonal antibody against human inhibin as a marker for sex cord-stromal tumors of the ovary. Am J Surg Pathol 21:583–589[CrossRef][Medline]
182. Stewart CJ, Jeffers MD, Kennedy A 1997 Diagnostic value of inhibin immunoreactivity in ovarian gonadal stromal tumors and their histological mimics. Histopathology 31:67–74[CrossRef][Medline]
183. Matias-Guiu X, Pons C, Prat J 1998 Mullerian inhibiting substance, -inhibin, and CD99 expression in sex cord-stromal tumors and endometrioid ovarian carcinomas resembling sex cord-stromal tumors. Hum Pathol 29:840–845[CrossRef][Medline]
184. Puls LE, Powell DE, DePriest PD, Gallion HH, Hunter JE, Kryscio RJ, van Nagell Jr JR 1992 Transition from benign to malignant epithelium in mucinous and serous ovarian cystadenocarcinoma. Gynecol Oncol 47:53–57[CrossRef][Medline]
185. Scully RE 1995 Early de novo ovarian cancer and cancer developing in benign ovarian lesions. Int J Gynaecol Obstet 49 Suppl:S9–15
186. Crayford TJ, Campbell S, Bourne TH, Rawson HJ, Collins WP 2000 Benign ovarian cysts and ovarian cancer: a cohort study with implications for screening. Lancet 355:1060–1063[CrossRef][Medline]
187. Zheng J, Wan M, Zweizig S, Velicescu M, Yu MC, Dubeau L 1993 Histologically benign or low-grade malignant tumors adjacent to high-grade ovarian carcinomas contain molecular characteristics of high-grade carcinomas. Cancer Res 53:4138–4142[Abstract/Free Full Text]
188. Yamashita K, Yamoto M, Shikone T, Minami S, Nakano R 1999 Immunohistochemical localization of inhibin and activin subunits in human epithelial ovarian tumors. Am J Obstet Gynecol 180:316–322[CrossRef][Medline]
189. Zheng W, Luo MP, Welt C, Lambert-Messerlian G, Sung CJ, Zhang Z, Ying SY, Schneyer AL, Lauchlan SC, Felix JC 1998 Imbalanced expression of inhibin and activin subunits in primary epithelial ovarian cancer. Gynecol Oncol 69:23–31[CrossRef][Medline]
190. Phocas I, Sarandakou A, Sikiotis K, Rizos D, Kalambokis D, Zourlas PA 1996 A comparative study of serum -ßA immunoreactive inhibin and tumor-associated antigens CA125 and CEA in ovarian cancer. Anticancer Res 16:3827–3831[Medline]
191. Lambert-Messerlian GM, DePasquale SE, Maybruck WM, Steinhoff MM, Gajewski WH 1999 Secretion of activin A in recurrent epithelial ovarian carcinoma. Gynecol Oncol 74:93–97[CrossRef][Medline]
192. Lambert-Messerlian GM, Steinhoff M, Zheng W, Canick JA, Gajewski WH, Seifer DB, Schneyer AL 1997 Multiple immunoreactive inhibin proteins in serum from postmenopausal women with epithelial ovarian cancer. Gynecol Oncol 65:512–516[CrossRef][Medline]
193. Guerrieri C, Franlund B, Malmstrom H, Boeryd B 1998 Ovarian endometrioid carcinomas simulating sex cord-stromal tumors: a study using inhibin and cytokeratin 7. Int J Gynecol Pathol 17:266–271[Medline]
194. Salazar H, Godwin AK, Daly MB, Laub PB, Hogan WM, Rosenblum N, Boente MP, Lynch HT, Hamilton TC 1996 Microscopic benign and invasive malignant neoplasms and a cancer-prone phenotype in prophylactic oophorectomies. J Natl Cancer Inst 88:1810–1820[Abstract/Free Full Text]
195. Petraglia F, Luisi S, Pautier P, Sabourin JC, Rey R, Lhomme C, Bidart JM 1998 Inhibin B is the major form of inhibin/activin family secreted by granulosa cell tumors. J Clin Endocrinol Metab 83:1029–1032[Abstract/Free Full Text]
196. Welt CK, Lambert-Messerlian G, Zheng W, Crowley Jr WF, Schneyer AL 1997 Presence of activin, inhibin, and follistatin in epithelial ovarian carcinoma. J Clin Endocrinol Metab 82:3720–3727[Abstract/Free Full Text]
197. Di Simone N, Crowley Jr WF, Wang QF, Sluss PM, Schneyer AL 1996 Characterization of inhibin/activin subunit, follistatin, and activin type II receptors in human ovarian cancer cell lines: a potential role in autocrine growth regulation. Endocrinology 137:486–494[Abstract]
198. Rainey WH, Sawetawan C, Shay JW, Michael MD, Mathis JM, Kutteh W, Byrd W, Carr BR 1994 Transformation of human granulosa cells with the E6 and E7 regions of human papillomavirus. J Clin Endocrinol Metab 78:705–710[Abstract]
199. Lie BL, Leung E, Leung PC, Auersperg N 1996 Long-term growth and steroidogenic potential of human granulosa-lutein cells immortalized with SV40 large T antigen. Mol Cell Endocrinol 120:169–176[CrossRef][Medline]
200. Hosokawa K, Dantes A, Schere-Levy C, Barash A, Yoshida Y, Kotsuji F, Vlodavsky I, Amsterdam A 1998 Induction of Ad4BP/SF-1, steroidogenic acute regulatory protein, and cytochrome P450 scc enzyme system expression in newly established human granulosa cell lines. Endocrinology 139:4679–4687[Abstract/Free Full Text]
201. Keren-Tal I, Dantes A, Sprengel R, Amsterdam A 1993 Establishment of steroidogenic granulosa cell lines expressing follicle stimulating hormone receptors. Mol Cell Endocrinol 95:R1–R10
202. Nishi Y, Yanase T, Mu Y, Oba K, Ichino I, Saito M, Nomura M, Mukasa C, Okabe T, Goto K, Takayanagi R, Kashimura Y, Haji M, Nawata H 2001 Establishment and characterization of a steroidogenic human granulosa-like tumor cell line, KGN, that expresses functional follicle-stimulating hormone receptor. Endocrinology 142:437–445[Abstract/Free Full Text]
203. Choi KC, Kang SK, Tai CJ, Auersperg N, Leung PC 2001 The regulation of apoptosis by activin and transforming growth factor-ß in early neoplastic and tumorigenic ovarian surface epithelium. J Clin Endocrinol Metab 86:2125–2135[Abstract/Free Full Text]
204. Doctor VM, Sheth AR, Simha MM, Arbatti NJ, Aaveri JP, Sheth NA 1986 Studies on immunocytochemical localization of inhibin-like material in human prostatic tissue: comparison of its distribution in normal, benign and malignant prostates. Br J Cancer 53:547–554[Medline]
205. Akiyama K, Yoshioka Y, Schmid K, Offner GD, Troxler RF, Tsuda R, Hara M 1985 The amino acid sequence of human ß-microseminoprotein. Biochim Biophys Acta 829:288–294[CrossRef][Medline]
206. Liang ZG, Mitsudo SM, Koide SS 1992 Prostatic specific antigen and immunoglobulin binding factor in human seminal plasma and prostate. Arch Androl 29:225–231[Medline]
207. Dube JY, Frenette G, Paquin R, Chapdelaine P, Tremblay J, Tremblay RR, Lazure C, Seidah N, Chretien M 1987 Isolation from human seminal plasma of an abundant 16-kDa protein originating from the prostate, its identification with a 94-residue peptide originally described as ß-inhibin. J Androl 8:182–189[Abstract/Free Full Text]
208. Risbridger GP, Thomas T, Gurusinghe CJ, McFarlane JR 1996 Inhibin-related proteins in rat prostate. J Endocrinol 149:93–99[Abstract/Free Full Text]
209. Ying SY, Zhang Z, Huang G 1997 Expression and localization of inhibin/activin subunits and activin receptors in the normal rat prostate. Life Sci 60:397–401[CrossRef][Medline]
210. Thomas TZ, Chapman SM, Hong W, Gurusingfhe C, Mellor SL, Fletcher R, Pedersen J, Risbridger GP 1998 Inhibins, activins, and follistatins: expression of mRNAs and cellular localization in tissues from men with benign prostatic hyperplasia. Prostate 34:34–43[CrossRef][Medline]
211. Thomas TZ, Wang H, Niclasen P, O’Bryan MK, Evans LW, Groome NP, Pedersen J, Risbridger GP 1997 Expression and localization of activin subunits and follistatins in tissues from men with high grade prostate cancer. J Clin Endocrinol Metab 82:3851–3858[Abstract/Free Full Text]
212. Dalkin AC, Gilrain JT, Bradshaw D, Myers CE 1996 Activin inhibition of prostate cancer cell growth: selective actions on androgen-responsive LNCaP cells. Endocrinology 137:5230–5235[Abstract]
213. McPherson SJ, Thomas TZ, Wang H, Gurusinghe CJ, Risbridger GP 1997 Growth inhibitory response to activin A and B by human prostate tumor cell lines, LNCaP and DU145. J Endocrinol 154:535–545[Abstract/Free Full Text]
214. Greenberg NM, DeMayo F, Finegold MJ, Medina D, Tilley WD, Aspinall JO, Cunha GR, Donjacour AA, Matusik RJ, Rosen JM 1995 Prostate cancer in a transgenic mouse. Proc Natl Acad Sci USA 92:3439–3443[Abstract/Free Full Text]
215. Wang QF, Tilly KI, Tilly JL, Preffer F, Schneyer AL, Crowley Jr WF, Sluss PM 1996 Activin inhibits basal and androgen-stimulated proliferation and induces apoptosis in the human prostatic cancer cell line, LNCaP. Endocrinology 137:5476–5483[Abstract]
216. Zhang Z, Zhao Y, Batres Y, Lin MF, Ying SY 1997 Regulation of growth and prostatic marker expression by activin A in an androgen-sensitive prostate cancer cell line LNCAP. Biochem Biophys Res Commun 234:362–365[CrossRef][Medline]
217. Wang Q, Tabatabaei S, Planz B, Lin CW, Sluss PM 1999 Identification of an activin-follistatin growth modulatory system in the human prostate: secretion and biological activity in primary cultures of prostatic epithelial cells. J Urol 161:1378–1384[CrossRef][Medline]
218. Risbridger GP, Mellor SL, McPherson SJ, Schmitt JF 2001 The contribution of inhibins and activins to malignant prostate disease. Mol Cell Endocrinol 180:149–153[CrossRef][Medline]
219. McPherson SJ, Mellor SL, Wang H, Evans LW, Groome NP, Risbridger GP 1999 Expression of activin A and follistatin core proteins by human prostate tumor cell lines. Endocrinology 140:5303–5309[Abstract/Free Full Text]
220. Ishida H, Tashiro H, Watanabe M, Fujii N, Yoshida H, Imamura K, Minowada S, Shinohara M, Fukutani K, Aso Y, de Kretser DM 1990 Measurement of inhibin concentrations in men: study of changes after castration and comparison with androgen levels in testicular tissue, spermatic venous blood, and peripheral venous blood. J Clin Endocrinol Metab 70:1019–1022[Abstract/Free Full Text]
221. Anderson RA, Sharpe RM 2000 Regulation of inhibin production in the human male and its clinical applications. Int J Androl 23:136–144[CrossRef][Medline]
222. de Kretser DM, Meinhardt A, Meehan T, Phillips DJ, O’Bryan MK, Loveland KA 2000 The roles of inhibin and related peptides in gonadal function. Mol Cell Endocrinol 161:43–46[CrossRef][Medline]
223. de Jong F 1997 Testicular activin – too hot to handle? Eur J Endocrinol 137:448–449[CrossRef][Medline]
224. Anawalt BD, Bebb RA, Matsumoto AM, Groome NP, Illingworth PJ, McNeilly AS, Bremner WJ 1996 Serum inhibin B levels reflect Sertoli cell function in normal men and men with testicular dysfunction. J Clin Endocrinol Metab 81:3341–3345[Abstract]
225. de Kretser DM, McLachlan RI, Robertson DM, Burger HG 1989 Serum inhibin levels in normal men and men with testicular disorders. J Endocrinol 120:517–523[Abstract/Free Full Text]
226. Bergh A, Cajander S 1990 Immunohistochemical localization of inhibin- in the testes of normal men and in men with testicular disorders. Int J Androl 13:463–469[Medline]
227. Majdic G, McNeilly AS, Sharpe RM, Evans LR, Groome NP, Saunders PT 1997 Testicular expression of inhibin and activin subunits and follistatin in the rat and human fetus and neonate and during postnatal development in the rat. Endocrinology 138:2136–2147[Abstract/Free Full Text]
228. Anderson RA, Irvine DS, Balfour C, Groome NP, Riley SC 1998 Inhibin B in seminal plasma: testicular origin and relationship to spermatogenesis. Hum Reprod 13:920–926[Abstract/Free Full Text]
229. Gilcrease MZ, Delgado R, Albores-Saavedra J 1998 Testicular Sertoli cell tumor with a heterologous sarcomatous component: immunohistochemical assessment of Sertoli cell differentiation. Arch Pathol Lab Med 122:907–911[Medline]
230. Toppari J, Kaipia A, Kaleva M, Laato M, de Kretser DM, Krummen LA, Mather JP, Salmi TT 1998 Inhibin gene expression in a large cell calcifying Sertoli cell tumour and serum inhibin and activin levels. APMIS 106:101–112; discussion 112–3[Medline]
231. Grootenhuis AJ, van Sluijs FJ, Klaij IA, Steenbergen J, Timmerman MA, Bevers MM, Dieleman SJ, de Jong FH 1990 Inhibin, gonadotrophins and sex steroids in dogs with Sertoli cell tumors. J Endocrinol 127:235–242[Abstract/Free Full Text]
232. Peters MA, de Jong FH, Teerds KJ, de Rooij DG, Dieleman SJ, van Sluijs FJ 2000 Ageing, testicular tumors and the pituitary-testis axis in dogs. J Endocrinol 166:153–161[Abstract]
233. Petersen PM, Andersson AM, Rorth M, Daugaard G, Skakkebaek NE 1999 Undetectable inhibin B serum levels in men after testicular irradiation. J Clin Endocrinol Metab 84:213–215[Abstract/Free Full Text]
234. Morgan DR, Brame KG 1999 Granulosa cell tumour of the testis displaying immunoreactivity for inhibin. BJU Int 83:731–732[CrossRef][Medline]
235. Ulbright TM, Srigley JR, Reuter VE, Wojno K, Roth LM, Young RH 2000 Sex cord-stromal tumors of the testis with entrapped germ cells: a lesion mimicking unclassified mixed germ cell sex cord-stromal tumors. Am J Surg Pathol 24:535–542[CrossRef][Medline]
236. Sheth NA, Hurkadli KS, Sathe VS, Sheth AR 1984 Circulating levels of inhibin in cancer. Neoplasma 31:315–321[Medline]
237. Di Loreto C, Reis FM, Cataldi P, Zuiani C, Luisi S, Beltrami CA, Petraglia F 1999 Human mammary gland and breast carcinoma contain immunoreactive inhibin/activin subunits: evidence for a secretion into cystic fluid. Eur J Endocrinol 141:190–194[Abstract]
238. Ying SY, Zhang Z 1996 Expression and localization of inhibin/activin subunits and activin receptors in MCF-7 cells, a human breast cancer cell line. Breast Cancer Res Treat 37:151–160[CrossRef][Medline]
239. Liu QY, Niranjan B, Gomes P, Gomm JJ, Davies D, Coombes RC, Buluwela L 1996 Inhibitory effects of activin on the growth and morpholgenesis of primary and transformed mammary epithelial cells. Cancer Res 56:1155–1163[Abstract/Free Full Text]
240. Kalkhoven E, Roelen BA, de Winter JP, Mummery CL, van den Eijnden-van Raaij AJ, van der Saag PT, van der Burg B 1995 Resistance to transforming growth factor ß and activin due to reduced receptor expression in human breast tumor cell lines. Cell Growth Differ 6:1151–1161[Abstract]
241. Munro LM, Kennedy A, McNicol AM 1999 The expression of inhibin/activin subunits in the human adrenal cortex and its tumours. J Endocrinol 161:341–347[Abstract]
242. Renshaw AA, Granter SR 1998 A comparison of A103 and inhibin reactivity in adrenal cortical tumors: distinction from hepatocellular carcinoma and renal tumors. Mod Pathol 11:1160–1164[Medline]
243. Pelkey TJ, Frierson Jr HF, Mills SE, Stoler MH 1998 The subunit of inhibin in adrenal cortical neoplasia. Mod Pathol 11:516–524[Medline]
244. Fetsch PA, Powers CN, Zakowski MF, Abati A 1999 Anti--inhibin: marker of choice for the consistent distinction between adrenocortical carcinoma and renal cell carcinoma in fine-needle aspiration. Cancer 87:168–172[CrossRef][Medline]
245. Carroll RS, Corrigan AZ, Gharib SD, Vale W, Chin WW 1989 Inhibin, activin, and follistatin: regulation of follicle-stimulating hormone messenger ribonucleic acid levels. Mol Endocrinol 3:1969–1976[Abstract/Free Full Text]
246. Carroll RS, Corrigan AZ, Vale W, Chin WW 1991 Activin stabilizes follicle-stimulating hormone-ß messenger ribonucleic acid levels. Endocrinology 129:1721–1726[Abstract/Free Full Text]
247. Marshall J, Dalkin A, Haisenleder D, Kirk S 1996 Inhibins, activins, follistatin, and GnRH: regulators of gonadotropin subunit gene expression. In: Aono T, Sugino H, Vale WW, eds. Inhibin, activin and follistatin: regulatory functions in system and cell biology. Serono Symposia. New York: Springer; 39–50
248. Roberts V, Meunier H, Vaughan J, Rivier J, Rivier C, Vale W, Sawchenko P 1989 Production and regulation of inhibin subunits in pituitary gonadotropes. Endocrinology 124:552–554[Abstract/Free Full Text]
249. Asa SL, Ezzat S 1998 The cytogenesis and pathogenesis of pituitary adenomas. Endocr Rev 19:798–827[Abstract/Free Full Text]
250. Alexander JM, Bikkal HA, Zervas NT, Laws Jr ER, Klibanski A 1996 Tumor-specific expression and alternate splicing of messenger ribonucleic acid encoding activin/transforming growth factor-ß receptors in human pituitary adenomas. J Clin Endocrinol Metab 81:783–790[Abstract]
251. Penabad JL, Bashey HM, Asa SL, Haddad G, Davis KD, Herbst AB, Gennarelli TA, Kaiser UB, Chin WW, Snyder PJ 1996 Decreased follistatin gene expression in gonadotroph adenomas. J Clin Endocrinol Metab 81:3397–403[Abstract]
252. Danila DC, Inder WJ, Zhang X, Alexander JM, Swearingen B, Hedley-Whyte ET, Klibanski A 2000 Activin effects on neoplastic proliferation of human pituitary tumors. J Clin Endocrinol Metab 85:1009–1015[Abstract/Free Full Text]
253. Pardo FS, Leon S, Carroll R, Black P, Atkins L 2001 Pituitary tumorigenesis and hPit-1 cells. Cancer Genet Cytogenet 128:148–153[CrossRef][Medline]
254. D’Abronzo FH, Swearingen B, Klibanski A, Alexander JM 1999 Mutational analysis of activin/transforming growth factor-ß type I and type II receptor kinases in human pituitary tumors. J Clin Endocrinol Metab 84:1716–1721[Abstract/Free Full Text]
255. Goggins M, Shekher M, Turnacioglu K, Yeo CJ, Hruban RH, Kern SE 1998 Genetic alterations of the transforming growth factor ß receptor genes in pancreatic and biliary adenocarcinomas. Cancer Res 58:5329–5332[Abstract/Free Full Text]
256. La Rosa S, Uccella S, Billo P, Facco C, Sessa F, Capella C 1999 Immunohistochemical localization of - and ßA-subunits of inhibin/activin in human normal endocrine cells and related tumors of the digestive system. Virchows Arch 434:29–36[CrossRef][Medline]
257. Bottinger EP, Jakubczak JL, Roberts IS, Mumy M, Hemmati P, Bagnall K, Merlino G, Wakefield LM 1997 Expression of a dominant-negative mutant TGF-ß type II receptor in transgenic mice reveals essential roles for TGF-ß in regulation of growth and differentiation in the exocrine pancreas. EMBO J 16:2621–2633[CrossRef][Medline]
258. Ridder GJ, Maschek H, Flemming P, Nashan B, Klempnauer J 1998 Ovarian-like stroma in an invasive mucinous cystadenocarcinoma of the pancreas positive for inhibin: a hint concerning its possible histogenesis. Virchows Arch 432:451–454[CrossRef][Medline]
259. Zamboni G, Scarpa A, Bogina G, Iacono C, Bassi C, Talamini G, Sessa F, Capella C, Solcia E, Rickaert F, Mariuzzi GM, Kloppel G 1999 Mucinous cystic tumors of the pancreas: clinicopathological features, prognosis, and relationship to other mucinous cystic tumors. Am J Surg Pathol 23:410–422[CrossRef][Medline]
260. McCluggage WG, Ashe P, McBride H, Maxwell P, Sloan JM 1998 Localization of the cellular expression of inhibin in trophoblastic tissue. Histopathology 32:252–256[CrossRef][Medline]
261. Minami S, Yamoto M, Nakano R 1993 Immunohistochemical localization of inhibin-activin subunits in hydatidiform mole and invasive mole. Obstet Gynecol 82:414–418[Medline]
262. Petraglia F, Sawchenko P, Lim AT, Rivier J, Vale W 1987 Localization, secretion, and action of inhibin in human placenta. Science 237:187–189[Abstract/Free Full Text]
263. Petraglia F, Garuti GC, Calza L, Roberts V, Giardino L, Genazzani AR, Vale W, Meunier H 1991 Inhibin subunits in human placenta: localization and messenger ribonucleic acid levels during pregnancy. Am J Obstet Gynecol 165:750–758[Medline]
264. Shih IM, Kurman RJ 1999 Immunohistochemical localization of inhibin- in the placenta and gestational trophoblastic lesions. Int J Gynecol Pathol 18:144–150[Medline]
265. Pelkey TJ, Frierson Jr HF, Mills SE, Stoler MH 1999 Detection of the -subunit of inhibin in trophoblastic neoplasia. Hum Pathol 30:26–31[CrossRef][Medline]
266. Shih IM, Seidman JD, Kurman RJ 1999 Placental site nodule and characterization of distinctive types of intermediate trophoblast. Hum Pathol 30:687–694[CrossRef][Medline]
267. Florio P, Luisi S, Casarosa E, Genazzani AR, Pautier P, Lhomme C, Bidart JM, Driul PG, Petraglia F 1998 Serum levels of dimeric activin A are not a marker of placental tumors in the course of chemotherapy. J Endocrinol Invest 21:166–169[Medline]
268. Jones RL, Salamonsen LA, Critchley HOD, Rogers PAW, Affandi B, Findlay JK 2000 Inhibin and activin subunits are differentially expressed in endometrial cells and leukocytes during the menstrual cycle, in early pregnancy and in women using progestin-only contraception. Mol Hum Reprod 6:1107–1117[Abstract/Free Full Text]
269. Shiozaki M, Sakai R, Tabuchi M, Shinohara M, Kosaka M, Saito S, Eto Y 1992 The existence of activin A/erythroid differentiation factor and its inhibitor in human serum: comparison of normal and chronic renal failure sera. Biochem Biophys Res Commun 183:273–279[CrossRef][Medline]
270. Sakamoto Y, Shintani Y, Harada K, Abe M, Shitsukawa K, Saito S 1996 Determination of free follistatin levels in sera of normal subjects and patients with various diseases. Eur J Endocrinol 135:345–351[Abstract/Free Full Text]
271. Iezzoni JC, Mills SE, Pelkey TJ, Stoler MH 1999 Inhibin is not an immunohistochemical marker for hepatocellular carcinoma. An example of the potential pitfall in diagnostic immunohistochemistry caused by endogenous biotin. Am J Clin Pathol 111:229–234[Medline]
272. McCluggage WG, Maxwell P, Patterson A, Sloan JM 1997 Immunohistochemical staining of hepatocellular carcinoma with monoclonal antibody against inhibin. Histopathology 30:518–522[CrossRef][Medline]
273. Ahmed E, Young RH, Scully RE 1999 Adult granulosa cell tumor of the ovary with foci of hepatic cell differentiation: a report of four cases and comparison with two cases of granulosa cell tumor with Leydig cells. Am J Surg Pathol 23:1089–1093[CrossRef][Medline]
274. Mooney EE, Nogales FF, Tavassoli FA 1999 Hepatocytic differentiation in retiform Sertoli-Leydig cell tumors: distinguishing a heterologous element from Leydig cells. Hum Pathol 30:611–617[CrossRef][Medline]
275. Takabe K, Lebrun JJ, Nagashima Y, Ichikawa Y, Mitsuhashi M, Momiyama N, Ishikawa T, Shimada H, Vale WW 1999 Interruption of activin A autocrine regulation by antisense oligodeoxynucleotides accelerates liver tumor cell proliferation. Endocrinology 140:3125–3132[Abstract/Free Full Text]
276. Russell CE, Hedger MP, Brauman JN, de Kretser DM, Phillips DJ 1999 Activin A regulates growth and acute phase proteins in the human liver cell line, HepG2. Mol Cell Endocrinol 148:129–136[CrossRef][Medline]
277. Schwall RH, Robbins K, Jardieu P, Chang L, Lai C, Terrell TG 1993 Activin induces cell death in hepatocytes in vivo and in vitro. Hepatology 18:347–356[CrossRef][Medline]
278. Matzuk MM, Bradley A 1994 Identification and analysis of tumor suppressor genes using transgenic mouse models. Semin Cancer Biol 5:37–45[Medline]
279. Delbaere A, Sidis Y, Schneyer AL 1999 Differential response to exogenous and endogenous activin in a human ovarian teratocarcinoma-derived cell line (PA-1): regulation by cell surface follistatin. Endocrinology 140:2463–2470[Abstract/Free Full Text]

This article has been cited by other articles:

				B. M. Necela, W. Su, and E. A. Thompson Peroxisome Proliferator-activated Receptor {gamma} Down-regulates Follistatin in Intestinal Epithelial Cells through SP1 J. Biol. Chem., October 31, 2008; 283(44): 29784 - 29794. [Abstract] [Full Text] [PDF]

				R. V. Korupolu, U. Muenster, J. D. Read, W. Vale, and W. H. Fischer Activin A/Bone Morphogenetic Protein (BMP) Chimeras Exhibit BMP-like Activity and Antagonize Activin and Myostatin J. Biol. Chem., February 15, 2008; 283(7): 3782 - 3790. [Abstract] [Full Text] [PDF]

				J. L. Kipp, S. M. Kilen, T. K. Woodruff, and K. E. Mayo Activin Regulates Estrogen Receptor Gene Expression in the Mouse Ovary J. Biol. Chem., December 14, 2007; 282(50): 36755 - 36765. [Abstract] [Full Text] [PDF]

				Q. Li, J. M. Graff, A. E. O'Connor, K. L. Loveland, and M. M. Matzuk SMAD3 Regulates Gonadal Tumorigenesis Mol. Endocrinol., October 1, 2007; 21(10): 2472 - 2486. [Abstract] [Full Text] [PDF]

				Q. Li, R. Kumar, K. Underwood, A. E. O'Connor, K. L. Loveland, J. S. Seehra, and M. M. Matzuk Prevention of cachexia-like syndrome development and reduction of tumor progression in inhibin-deficient mice following administration of a chimeric activin receptor type II-murine Fc protein Mol. Hum. Reprod., September 1, 2007; 13(9): 675 - 683. [Abstract] [Full Text] [PDF]

				L. M Bilezikjian, A. L Blount, C. J Donaldson, and W. W Vale Pituitary actions of ligands of the TGF-{beta} family: activins and inhibins. Reproduction, August 1, 2006; 132(2): 207 - 215. [Abstract] [Full Text] [PDF]

				S. E. Matsuo, S. G. Leoni, A. Colquhoun, and E. T. Kimura Transforming growth factor-{beta}1 and activin A generate antiproliferative signaling in thyroid cancer cells. J. Endocrinol., July 1, 2006; 190(1): 141 - 150. [Abstract] [Full Text] [PDF]

				Y.-G. Chen, Q. Wang, S.-L. Lin, C. D. Chang, J. Chung, and S.-Y. Ying Activin Signaling and Its Role in Regulation of Cell Proliferation, Apoptosis, and Carcinogenesis Exp Biol Med, May 1, 2006; 231(5): 534 - 544. [Abstract] [Full Text] [PDF]

				M. Bielinska, S. Kiiveri, H. Parviainen, S. Mannisto, M. Heikinheimo, and D. B. Wilson Gonadectomy-induced Adrenocortical Neoplasia in the Domestic Ferret (Mustela putorius furo) and Laboratory Mouse Veterinary Pathology, March 1, 2006; 43(2): 97 - 117. [Abstract] [Full Text] [PDF]

				H. Lefevre, C. Bouvattier, N. Lahlou, C. Adamsbaum, P. Bougneres, and J.-C. Carel Prepubertal gynecomastia in Peutz-Jeghers syndrome: incomplete penetrance in a familial case and management with an aromatase inhibitor Eur. J. Endocrinol., February 1, 2006; 154(2): 221 - 227. [Abstract] [Full Text] [PDF]

				U. Muenster, C. A. Harrison, C. Donaldson, W. Vale, and W. H. Fischer An Activin-A/C Chimera Exhibits Activin and Myostatin Antagonistic Properties J. Biol. Chem., November 4, 2005; 280(44): 36626 - 36632. [Abstract] [Full Text] [PDF]

				L. Cobellis, F. M. Reis, S. Luisi, S. Danero, L. Pirtoli, G. Scambia, and F. Petraglia High Concentrations of Activin A in the Peritoneal Fluid of Women With Epithelial Ovarian Cancer Reproductive Sciences, May 1, 2004; 11(4): 203 - 206. [Abstract] [PDF]

				C A Longui, S H V Lemos-Marini, B Figueiredo, B B Mendonca, M Castro, R Liberatore Jr, C Watanabe, C L P Lancellotti, M N Rocha, M B Melo, et al. Inhibin {alpha}-subunit (INHA) gene and locus changes in paediatric adrenocortical tumours from TP53 R337H mutation heterozygote carriers J. Med. Genet., May 1, 2004; 41(5): 354 - 359. [Abstract] [Full Text] [PDF]

				S. La Rosa, S. Uccella, S. Marchet, C. Capella, and R. V. Lloyd Localization of Inhibins and Activins in Normal Endocrine Cells and Endocrine Tumors of the Gut and Pancreas: an Immunohistochemical and In Situ Hybridization Study J. Histochem. Cytochem., February 1, 2004; 52(2): 217 - 225. [Abstract] [Full Text] [PDF]

				K. H. Burns, J. E. Agno, L. Chen, B. Haupt, S. C. Ogbonna, K. S. Korach, and M. M. Matzuk Sexually Dimorphic Roles of Steroid Hormone Receptor Signaling in Gonadal Tumorigenesis Mol. Endocrinol., October 1, 2003; 17(10): 2039 - 2052. [Abstract] [Full Text] [PDF]

				J. S. Jeruss, C. D. Sturgis, A. W. Rademaker, and T. K. Woodruff Down-Regulation of Activin, Activin Receptors, and Smads in High-Grade Breast Cancer Cancer Res., July 1, 2003; 63(13): 3783 - 3790. [Abstract] [Full Text] [PDF]

				A. Krishnan, C. Murdock, J. Allard, M. Cisar, E. Reid, L. Nieman, and J. Segars Pseudo-isolated FSH deficiency caused by an inhibin B-secreting granulosa cell tumour: Case report Hum. Reprod., March 1, 2003; 18(3): 502 - 505. [Abstract] [Full Text] [PDF]

				D. C. Danila, X. Zhang, Y. Zhou, J. N. S. Haidar, and A. Klibanski Overexpression of Wild-Type Activin Receptor Alk4-1 Restores Activin Antiproliferative Effects in Human Pituitary Tumor Cells J. Clin. Endocrinol. Metab., October 1, 2002; 87(10): 4741 - 4746. [Abstract] [Full Text] [PDF]

				J. F. Schmitt, D. S. Millar, J. S. Pedersen, S. L. Clark, D. J. Venter, M. Frydenberg, P. L. Molloy, and G. P. Risbridger Hypermethylation of the Inhibin {alpha}-Subunit Gene in Prostate Carcinoma Mol. Endocrinol., February 1, 2002; 16(2): 213 - 220. [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 Reprints, Permissions and Rights Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Risbridger, G. P. Articles by Robertson, D. M. Search for Related Content PubMed PubMed Citation Articles by Risbridger, G. P. Articles by Robertson, D. M.