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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bone morphogenetic proteins (BMPs), members of the transforming growth factor beta superfamily, were recently shown to be expressed and to regulate steroidogenesis in rat ovarian tissue. The purpose of this study was to investigate the effect of BMP-4 on androgen production in a human ovarian theca-like tumor (HOTT) cell culture model. We have previously demonstrated the usefulness of these cells as a model for human thecal cells. HOTT cells respond to protein kinase A agonists by increased production of androstenedione and with an induction of steroid-metabolizing enzymes. In this investigation, HOTT cells were treated with forskolin or dibutyryl cyclic AMP (dbcAMP) in the presence or absence of various concentrations of BMP-4. The accumulation of androstenedione, progesterone, and 17alpha-hydroxyprogesterone (17OHP) in the incubation medium was measured by RIA. The expression of 17alpha-hydroxylase (CYP17), 3beta-hydroxysteroid dehydrogenase (3betaHSD), cholesterol side-chain cleavage (CYP11A1), and steroidogenic acute regulatory (StAR) protein was determined by protein immunoblotting analysis using specific rabbit polyclonal antibodies. We also examined the expression of BMP receptor subtypes in our HOTT cells using RT-PCR. In cells treated with medium alone, steroid accumulation and steroid enzyme expression was unchanged. In cells treated with BMP alone there was a modest decrease in androstenedione secretion. In the presence of forskolin, HOTT cell production of androstenedione, 17OHP, and progesterone increased by approximately 4.5-, 35-, and 3-fold, respectively. In contrast, BMP-4 decreased forskolin-stimulated HOTT cell secretion of androstenedione and 17OHP by 50% but increased progesterone production 3-fold above forskolin treatment alone. Forskolin treatment led to an increase in CYP17, CYP11A1, 3betaHSD, and StAR protein expression. BMP-4 markedly inhibited forskolin stimulation of CYP17 expression but had little effect on 3betaHSD, CYP11A1, or StAR protein levels. Similar results were observed with the cAMP analog dbcAMP. In addition, BMP-4 inhibited basal and forskolin stimulation of CYP17 messenger RNA expression as determined by RNase protection assay. Other members of the transforming growth factor beta superfamily, including activin and inhibin, had minimal effect on androstenedione production in the absence of forskolin. In the presence of forskolin, activin inhibited androstenedione production by 80%. Activin also inhibited forskolin induction of CYP17 protein expression as determined by Western analysis. We identified the presence of messenger RNA for three BMP receptors (BMP-IA, BMP-IB, and BMP-II) in the HOTT cells model. In conclusion, BMP-4 inhibits HOTT cell expression of CYP17, leading to an alteration of steroidogenic pathway resulting in reduced androstenedione accumulation and increased progesterone production. These effects of BMP-4 seem similar to those caused by activin, another member of the transforming growth factor-beta superfamily of proteins.
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PMID:Bone morphogenetic protein inhibits ovarian androgen production. 1099 29

Activin ligands are formed by dimerization of activin ss(A)- and/or ss(B)-subunits to produce activins A, AB, or B. These ligands are members of the transforming growth factor-ss superfamily and act as growth and differentiation factors in many cells and tissues. New additions to this family include activin ss(C)-, ss(D)-, and ss(E)-subunits. The aim of this investigation was to examine the localization of and dimerization among activin subunits; the results demonstrate that activin ss(C) can form dimers with activin ss(A) and ss(B) in vitro, but not with the inhibin alpha-subunit. Using a specific antibody, activin ss(C) protein was localized to human liver and prostate and colocalized with ss(A)- and ss(B)-subunits to specific cell types in benign and malignant prostate tissues. Activin C did not alter DNA synthesis of the prostate tumor cell line, LNCaP, or the liver tumor cell line, HepG2, in vitro when added alone or with activin A. Therefore, the capacity to form novel activin heterodimers (but not inhibin C) resides in the human liver and prostate. Activin A, AB, and B have diverse actions in many tissues, including liver and prostate, but there is no known biological activity for activin C. Thus, the evidence of formation of activin AC or BC heterodimers may have significant implications in the regulation of levels and/or biological activity of other activins in these tissues.
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PMID:Localization of activin beta(A)-, beta(B)-, and beta(C)-subunits in humanprostate and evidence for formation of new activin heterodimers of beta(C)-subunit. 1113 53

Activin A, a member of the transforming growth factor beta superfamily, has a wide spread expression pattern and pleiotropic functions. In this overview we summarize data that points to a role of activin A in negative regulation of B lineage lymphocytes. Experiments performed by us and by other groups revealed the capacity of activin A to cause apoptotic death of tumor myeloma cells, through mechanisms of cell cycle inhibition and antagonism with the survival signal of interleukin-6. In vitro studies on B lymphocyte generation from bone marrow stem cells and use of human nasal polyps as a model of inflamed tissue further demonstrate an inhibitory role of activin A in B cell spread and accumulation. These data are analyzed with respect to our model of tissue organization that we term the "restrictin model of cell growth regulation." This model assumes a morphogen-like role of activin A in the hematopoietic system. Thus, the relative concentration of biologically functional activin A, in different parts of the tissue, may determine the local B cell content and functional state of these cells within a specific microenvironment.
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PMID:Role of activin A in negative regulation of normal and tumor B lymphocytes. 1140 69

The transmembrane receptor Patched regulates several developmental processes in both invertebrates and vertebrates. In vertebrates, Patched also acts as a tumor suppressor. The Patched pathway normally operates by negatively regulating Smoothened, a G-protein-coupled receptor; binding of Hedgehog ligand to Patched relieves this negative interaction and allows signaling by Smoothened. We show that Ptc regulates Drosophila head development by promoting cell proliferation in the eye-antennal disc. During head morphogenesis, Patched positively interacts with Smoothened, which leads to the activation of Activin type I receptor Baboon and stimulation of cell proliferation in the eye-antennal disc. Thus, loss of Ptc or Smoothened activity affects cell proliferation in the eye-antennal disc and results in adult head capsule defects. Similarly, reducing the dose of smoothened in a patched background enhances the head defects. Consistent with these results, gain-of-function Hedgehog interferes with the activation of Baboon by Patched and Smoothened, leading to a similar head capsule defect. Expression of an activated form of Baboon in the patched domain in a patched mutant background completely rescues the head defects. These results provide insight into head morphogenesis, a process we know very little about, and reveal an unexpected non-canonical positive signaling pathway in which Patched and Smoothened function to promote cell proliferation as opposed to repressing it.
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PMID:A positive role for patched-smoothened signaling in promoting cell proliferation during normal head development in Drosophila. 1193 50

The activin-follistatin system is a potent growth regulatory system of liver tissue homeostasis. Activin A inhibits hepatocellular DNA synthesis and induces cell death. Follistatin binds activin and sequesters it from the signaling pathway. Consistently, follistatin has been reported to act as an inducer of DNA synthesis in the liver. Using RNase protection analysis, we studied the expression of follistatin in rat and mouse liver tumors as a possible mechanism to overcome activin growth control. Approximately 40% of the tumors (nine of 24 each), most of them hepatocellular carcinomas, displayed increased levels of follistatin mRNA when compared to tumor-surrounding liver tissue. The degree of overexpression was highly variable but independent of the carcinogen treatment that animals had received. It was also independent from the histological stage of malignancy and further found in rat liver adenomas. Follistatin expression was also observed in cell lines derived from human hepatocellular carcinomas. Overexpression of follistatin may represent a unique strategy of hepatic tumors to overcome the inhibitory action of a growth factor, activin, by decreasing its local bioavailability.
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PMID:Follistatin overexpression in rodent liver tumors: a possible mechanism to overcome activin growth control. 1220 61

Activin A is a member of the transforming growth factor beta (TGF-beta) superfamily and is a strong differentiation factor of embryonic stem (ES) cells. It is unknown whether activin A has any correlation with carcinoma cell differentiation. We investigated the expression of activin-betaA (Act-betaA) which is a subunit of activin A, its receptor type I and IIb (ActRI, ActRIIb) and its inhibitor, inhibin-alpha (Inh-alpha), which is a subunit of inhibin A in esophageal carcinoma by reverse transcription polymerase chain reaction (RT-PCR) method. Act-betaA was overexpressed in carcinoma tissues significantly (p=0.030). On the other hand, Inh-alpha, ActRI and ActRIIb were neither overexpressed, nor suppressed. In immunohistochemistry and in situ hybridization analysis, Act-betaA expression was mainly derived from carcinoma cells. The mRNA expression of Act-betaA was not associated with carcinoma cell differentiation but lymph node metastasis (n0, 1, 2 vs. n3, 4; p=0.013) and clinical stage (I, II, III vs. IV; p=0.026). Moreover, patients with high mRNA expression of Act-betaA had a tendency to show poor prognosis compared to those with low mRNA expression (p=0.064). The finding indicated that activin A expression might not be associated with carcinoma cell differentiation but tumor aggressiveness such as lymph node metastasis in esophageal carcinoma.
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PMID:Clinical significance of the expression of activin A in esophageal carcinoma. 1246 87

Activin A has been reported to play a role in the progression of colorectal cancer. Because dietary fiber protects against colorectal cancer, we hypothesized that butyrate, a fermentation product of dietary fiber, may affect the expression of activin A in colon cancer cells. Semiquantitative RT-PCR demonstrated that the activin A gene was upregulated by sodium butyrate in the human colon cancer cell lines HT-29 and Caco-2 in a concentration- and time-dependent manner. However, the activin A gene did not respond to sodium butyrate in the human normal colonic cell line FHC, rat normal intestinal epithelial cell (IEC) line IEC-6, and the explant of rat colon. Flow cytometry and agarose gel electrophoresis of genomic DNA revealed that cell cycle arrest and apoptosis were induced by sodium butyrate but not exogenous activin A in HT-29 cells, indicating that activin A could not act as an autocrine factor in colon cancer cells. By assuming that activin A promotes colorectal cancer spread as a paracrine factor, our findings suggest that butyrate could act as a tumor promoter in some circumstances.
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PMID:Upregulation of activin A gene by butyrate in human colon cancer cell lines. 1254 Mar 70

In addition to a stimulatory effect on FSH production by the pituitary gland, activin is thought to have a paracrine or autocrine role in follicular development in the ovary, where it is produced. Recently, we established a human ovarian granulosa tumor cell line, KGN, which possesses in vivo characteristics of granulosa cells, namely the expression of functional FSH receptors and cytochrome P-450 aromatase. Here, we have demonstrated the activin signaling pathway and its role in KGN cells. A series of transient transfection experiments revealed that activin type IB receptor (ActRIB) is an essential component of the activin signaling pathway in KGN cells. Smad2 was found to act downstream of ActRIB as an intracellular signal transmitter. Smad7, but not Smad6, was an inhibitory Smad in the pathway. Finally, we show that FSH receptor expression and cytochrome P-450 (P-450) aromatase activity was up-regulated by activin stimulation through ActRIB in KGN cells. These results show that we have clarified the signaling mechanisms and the roles of activin in the human granulosa cell line, KGN. Activin signaling mediated by ActRIB-Smad2 system in the ovary may thus be essential for the regulation of follicular differentiation.
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PMID:Activin signaling through type IB activin receptor stimulates aromatase activity in the ovarian granulosa cell-like human granulosa (KGN) cells. 1263 45

In humans, Sertoli cell tumors account for approximately 4% of all testicular tumors, and 20% of these are malignant. The mechanisms underlying Sertoli cell tumorigenesis remain largely unknown. Using gene knockout technology, we previously generated mutant mice lacking the alpha subunit of inhibin dimers. The inhibin alpha-null male mice develop testicular Sertoli cell tumors with 100% penetrance. These tumors develop as early as 4 weeks of age and cause a cachexia-like wasting syndrome. Castrated inhibin alpha knockout mice develop sex steroidogenic adrenal cortical tumors. These studies have identified inhibins as secreted tumor suppressors with specificity for the gonads and adrenal glands. It had been suggested that endocrine factors play roles in Sertoli cell tumorigenesis by altering cell cycle machinery of the Sertoli cells. To test the potential of these factors to function as modifiers of Sertoli cell tumorigenesis, we have employed a genetic intercross strategy, breeding inhibin a mutant mice with mutant mice deficient in endocrine signaling factors including gonadotropin releasing hormone (hypogonadal, hpg mice), follicle stimulating hormone, anti-Miillerian hormone (AMH), activin receptor type II, or androgen receptor (testicular feminization, tfm mice), or mice overexpressing follistatin. We are also investigating the effects of loss of critical cell cycle regulators, such as cyclin dependent kinase inhibitor p27, on Sertoli cell tumorigenesis in inhibin alpha knockout males. These studies clearly demonstrate the roles of these factors as modifiers of the Sertoli cell tumorigenesis. Activin signaling through activin receptor type II is responsible for the cachexia-like syndrome observed in the inhibin a knockout mice with tumors. The gonadotropin hormones are essential for testicular tumor development, but elevated FSH levels are not sufficient to cause Sertoli cell tumors. Absence of FSH, lack of androgen receptor, or overexpression of follistatin slows the tumor growth and minimizes the cachexia symptoms, thus prolonging the life span of these double mutant mice. In contrast, absence of AMH or p27 causes earlier onset and more aggressive development of testicular tumor, with an earlier death of double mutant mice. We are currently investigating roles of estrogen signaling pathways, and other cell cycle regulators, in tumor development in the inhibin alpha knockout mice by generating mice with double or triple mutations. Genetic engineering in mouse models provides a powerful tool to study the mechanisms of testicular tumorigenesis and define the important genetic modifiers in vivo.
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PMID:Genetic engineering to study testicular tumorigenesis. 1276 Mar 77

Activin and inhibin, two closely related protein hormones, are members of the transforming growth factor beta (TGF beta) superfamily of growth factors. Activin and TGF beta have been associated with mouse mammary gland development and human breast carcinogenesis. TGF beta expression in the mammary gland has been previously described, and was found to be expressed in nonparous tissue and during pregnancy, down-regulated during lactation, and then up-regulated during involution. The expression pattern of activin subunits, receptors and cytoplasmic signaling molecules has not been thoroughly described in post-natal mammary gland development. We hypothesize that activin signaling components are dynamically regulated during mammary gland development, thereby permitting activin to have distinct temporal growth regulatory actions on this tissue. To examine the activin signal transduction system in the mammary gland, tissue from CD1 female mice was dissected from nonparous, lactating day 1, 10, and 20 and post-weaning day 4 animals. The expression of the activin receptors (ActRIIA, ActRIIB and ActRIB), the inhibin co-receptor (betaglycan), and ligand subunit (alpha, beta A and beta B), mRNA was measured by semi-quantitative RT-PCR in these tissues. In addition, the cellular compartmentalization of the activin signaling proteins, including the cytoplasmic signaling co-activators, Smads 2, 3 and 4, were examined by immunohistochemistry. Generally, mRNA abundance of activin signaling components was greatest in the nonparous tissue, and then decreased, whereas protein immunoreactivity for activin signaling components increased during lactation and decreased during involution. The alpha-subunit protein was detected in nonparous and lactating day 1 tissue only. Importantly, Smad 3, but not Smad 2, was detected in epithelial cell nuclei during all time points examined, indicating that activin signaling is mediated by Smad 3 at these times. These findings suggest that activin's growth regulatory role during lactation may be distinguished from that of TGF beta during post-natal mammary development. Future studies will focus on determining the exact role this ligand plays in mammary tissue differentiation and neoplasia.
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PMID:Localization of activin and inhibin subunits, receptors and SMADs in the mouse mammary gland. 1278 14


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