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N Auersperg

Publications and source records attributed to N Auersperg.

At least 19 recordsLinked to original sources

The ovarian surface epithelium: simple source of a complex disease.

The ovarian surface epithelium (OSE) is thought to be the origin of most ovarian cancers in humans. OSE is a single cell layer of squamous or cuboidal cells on the surface of ovaries. In contrast to its relatively simple structure, it gives rise to a highly complex group of neoplasms, the epithelial ovarian carcinomas. Thus, in this review, we summarize the development and the main characteristics of normal adult OSE with emphasis on those properties that might contribute to its propensity to undergo neoplastic progression. Secondly, a brief comparison of the biology and endocrinology of normal and neoplastic OSE is being described to understand the mechanisms in the transformation of normal OSE to its neoplastic counterparts. Lastly, recent advances in experimental approaches including in vitro and in vivo models that have contributed to our understanding of the nature of epithelial ovarian cancers are being briefly explored.

Animals↗

Lysophosphatidic acid induction of vascular endothelial growth factor expression in human ovarian cancer cells.

BACKGROUND: Lysophosphatidic acid (LPA) stimulates ovarian tumor growth at concentrations present in ascitic fluid. Vascular endothelial growth factor (VEGF) stimulates angiogenesis and plays a pivotal role in the formation of ovarian cancer-associated ascites. We examined whether LPA promotes ovarian tumor growth by increasing angiogenesis via VEGF. METHODS: VEGF expression was examined in a simian virus 40 T-antigen-immortalized ovarian surface epithelial cell line (IOSE-29) and in ovarian cancer cell lines (OVCAR-3, SKOV-3, and CAOV-3) treated with LPA. VEGF promoter activity was measured in OVCAR-3 cells after transfection or cotransfection with c-Fos and c-Jun, components of AP1 transcription factor, potential binding sites for which are present in the VEGF promoter. The expression of the LPA receptors Edg2 and Edg4 was also assessed. All statistical tests were two-sided. RESULTS: LPA treatment increased steady-state VEGF messenger RNA (mRNA) levels in OVCAR-3 cells in a time- and dose-dependent fashion and stimulated VEGF promoter activity without prolonging mRNA half-life in these cells, but LPA had little effect on IOSE-29 cells. Forced overexpression of c-Jun and c-Fos in OVCAR-3 cells stimulated VEGF promoter activity fourfold. LPA also elevated VEGF protein levels by 1.5-fold in SKOV-3 cells (P =.0148), 1.9-fold in CAOV-3 cells (P<.001), and threefold in OVCAR-3 cells (P<.0001). Both Edg2 and Edg4 were detected in ovarian cancer cells; however, only Edg2 was present in normal ovarian surface epithelial cells and IOSE-29 cells. CONCLUSIONS: LPA stimulates ovarian tumor growth, at least in part, via induction of VEGF expression through transcriptional activation. However, this LPA response is not evident in normal ovarian surface epithelial cells. Our data suggest that Edg4, but not Edg2, plays a role in LPA stimulation of ovarian tumor growth.

Antibiotics, Antineoplastic↗

Differential expression of activin/inhibin subunit and activin receptor mRNAs in normal and neoplastic ovarian surface epithelium (OSE).

Ovarian surface epithelium (OSE) is the tissue of origin for the majority of ovarian cancers. The mechanism underlying the neoplastic transformation of OSE to ovarian cancer is poorly understood. Activin, a member of the transforming growth factor-beta superfamily, has been shown to increase cell proliferation in ovarian cancer cells. The present study was carried out to investigate the expression and regulation of activin/inhibin subunits and activin receptors in normal and neoplastic OSE. Using reverse transcriptase-polymerase chain reaction and Southern blot analysis, the mRNA levels of alpha, betaA and betaB subunits and activin receptor type IIA and IIB were analyzed in normal OSE and the ovarian cancer cell line, OVCAR-3 cells. The alpha and betaA subunits were highly expressed in normal OSE when compared to OVCAR-3 cells. By contrast, betaB subunit was highly expressed in OVCAR-3 cells, when compared to normal OSE cells. Interestingly, activin receptor IIB mRNA levels were significantly higher in OVCAR-3 when compared to normal OSE cells, whereas activin receptor IIA mRNA levels were the same in both cell types. To characterize the growth modulatory role of activin during neoplastic progression, normal OSE and OVCAR-3 cells were treated with recombinant human activin A (rh-activin A). At concentrations of 1,10 and 100 ng/ml, rh-activin A stimulated the growth of OVCAR-3 cells, but not of normal OSE. Treatment with follistatin, binding protein of activin, attenuates the stimulatory effect of activin. To determine whether the growth stimulatory action of activin in the neoplastic OSE is mediated via an autocrine regulatory mechanism, OVCAR-3 cells were treated with rh-activin A in a dose- and time-dependent manner and the expression levels of activin/inhibin subunits and activin receptors were investigated. Treatments with activin increased the alpha and betaA subunit mRNA levels in a dose- and time-dependent manner. However, no difference was observed in levels of betaB subunit, or in activin receptor type IIA and IIB mRNAs following activin treatments in OVCAR-3 cells. Taken together, these results suggest that different levels of activin/inhibin and activin receptor isoforms are expressed in normal and neoplastic OSE cells. In addition, the altered expression of the activin/inhibin subunits, as well as the cell proliferative effect of activin observed in OVCAR-3 but not in normal OSE cells, indicate that activin may act as an autocrine regulator of neoplastic OSE progression.

Activin Receptors↗

Coexpression of hepatocyte growth factor-Met: an early step in ovarian carcinogenesis?

Since autocrine regulation of HGF-Met is implicated in many forms of human cancer, we investigated whether the predisposition to develop ovarian cancer in women with hereditary ovarian cancer syndromes involves changes in the expression of HGF-Met by the tissue of origin of epithelial ovarian cancers, the ovarian surface epithelium (OSE). We compared cultures of normal OSE from women with (FH-OSE) (n=20) and with no (NFH-OSE) (n=48) family histories of ovarian cancer, SV40 Tag immortalized OSE lines (IOSE, n=5) and ovarian cancer cell lines (n=3). Cultures derived from 21/22 women with NFH-OSE and 13/13 women with FH-OSE expressed Met mRNA initially. After two to three passages, Met was downregulated in 37% of NFH-OSE cultures but persisted in 100% of FH-OSE cultures and ovarian cancer lines, like other epithelial differentiation markers that are stabilized in FH-OSE and neoplasia. HGF and Met mRNA were concomitantly expressed by NFH-OSE from only three of 32 women but in FH-OSE from eight of 13 women, and also in five of five IOSE and two of three ovarian cancer lines. Conditioned media from FH-OSE, but not NFH-OSE, contained immunoreactive HGF and induced cohort migration which was inhibited by neutralizing HGF antibody. Several signaling molecules of the PI3K pathway, including Akt2 and p70 S6K, were constitutively activated in FH-OSE from six of six women but in NFH-OSE from only four of eight women. Exogenous HGF was mitogenic in OSE, and that effect was regulated through the MAP kinase (ERK1/ERK2) and FRAP/p70 S6K pathways. The proliferative response to HGF was greater in NFH-OSE than in FH-OSE cultures. The results show that FH-OSE cultures differ from NFH-OSE by increased stability of Met expression and by HGF secretion. Constitutive phosphorylation of kinases and a diminished growth response to HGF suggest the presence of autocrine regulation in FH-OSE. In analogy with other cell types where an autocrine HGF-Met loop has been implicated in tumorigenic transformation, this change in FH-OSE may play a role in the enhanced susceptibility to ovarian carcinogenesis in women with hereditary ovarian cancer syndromes.

Autocrine Communication↗

Profiling of protein kinases in the neoplastic transformation of human ovarian surface epithelium.

OBJECTIVE: The aim of this study was to study the pattern of protein kinase expression in a culture model of epithelial ovarian carcinogenesis. METHODS: Cultures of normal human ovarian surface epithelium (OSE), OSE from women with BRCA1 mutations, a cell culture model of preneoplastic (SV40 T-antigen-immortalized, nontumorigenic) and neoplastic (SV40-E-cadherin transfected, tumorigenic) OSE, and three ovarian cancer cell lines were used to represent OSE phenotypes of different genetic backgrounds and at different, progressive stages of neoplastic transformation. The protein kinase network signaling was studied by Western blotting, simultaneously using multiple antibodies for specific protein kinases. RESULTS: High levels of cGMP-dependent protein kinase were found in normal and preneoplastic OSE, but were absent in neoplastic OSE. In contrast, expression of MEK6 was detected exclusively in neoplastic OSE. The expressions of casein kinase II (CK2), p38 mitogen-activated protein kinase (MAPK), cyclin-dependent kinase, and the phosphatidylinositol 3-kinase (PI3K) effectors Akt2 and p70 S6 kinase (S6K) were several-fold higher in neoplastic OSE than in normal OSE, whereas the expressions of the MAPKs extracellular signal-regulated kinases ERK1 and -2 were unchanged. Importantly, constitutive phosphorylation of Akt2 and p70 S6K, as found in neoplastic OSE, was also observed in overtly normal OSE from women with predisposing BRCA1 gene mutations. CONCLUSIONS: These data demonstrate that different repertoires of downstream signaling proteins, particularly those of the MEK6-p38 MAPK-CK2 pathway and the PI3K pathway, are correlated with phenotypic manifestations of a cell culture model of OSE at progressive stages in the development of ovarian cancer. Changes in PI3K effectors are already found in overtly normal OSE from women with BRCA1 mutations.

Animals↗

Ovarian surface epithelium: biology, endocrinology, and pathology.

The epithelial ovarian carcinomas, which make up more than 85% of human ovarian cancer, arise in the ovarian surface epithelium (OSE). The etiology and early events in the progression of these carcinomas are among the least understood of all major human malignancies because there are no appropriate animal models, and because methods to culture OSE have become available only recently. The objective of this article is to review the cellular and molecular mechanisms that underlie the control of normal and neoplastic OSE cell growth, differentiation, and expression of indicators of neoplastic progression. We begin with a brief discussion of the development of OSE, from embryonic to the adult. The pathological and genetic changes of OSE during neoplastic progression are next summarized. The histological characteristics of OSE cells in culture are also described. Finally, the potential involvement of hormones, growth factors, and cytokines is discussed in terms of their contribution to our understanding of the physiology of normal OSE and ovarian cancer development.

Adult↗

Estradiol regulates gonadotropin-releasing hormone (GnRH) and its receptor gene expression and antagonizes the growth inhibitory effects of GnRH in human ovarian surface epithelial and ovarian cancer cells.

In the present study, we investigated the expression of estrogen receptors (ERalpha and ERbeta) in human ovarian surface epithelial (hOSE) cells and the ovarian cancer cell line, OVCAR-3, and provided novel evidence that estrogen may have a growth regulatory effect in these cells. Expression levels of ERalpha messenger RNA (mRNA) were 1.5-fold higher in OVCAR-3 cells than in hOSE cells, as revealed by semiquantitative RT-PCR and Southern blot analysis. A significant increase (3.3-fold) in ERss mRNA levels was observed in OVCAR-3 cells compared with hOSE cells. In parallel with mRNA levels, expression levels of ERalpha and ERbeta proteins were also higher in OVCAR-3 cells compared with hOSE cells. We recently proposed that GnRH and its receptor may have an autocrine role in hOSE and ovarian cancer cells. To determine whether estrogen regulates GnRH and GnRH receptor (GnRHR), hOSE and OVCAR-3 cells were treated with various concentrations of 17beta-estradiol for 24 h. Expression levels of GnRH and GnRHR mRNA were examined using quantitative and competitive RT-PCR, respectively. Treatment with 17beta-estradiol induced a significant down-regulation of GnRH mRNA in OVCAR-3 cells, but not in hOSE cells and of GnRHR mRNA in both hOSE and OVCAR-3 cells. Tamoxifen, an estrogen antagonist, prevented the effects of 17ssestradiol, suggesting that estradiol action is mediated via the ER. Finally, the effect of estrogen on the growth of hOSE and OVCAR-3 cells was investigated. The cells were treated with various concentrations of 17ss-estradiol, and the proliferative index of cells was measured using [(3)H]thymidine incorporation and DNA fluorometric assays. 17beta-Estradiol stimulated the growth of OVCAR-3 cells in a dose- and time-dependent manner. In contrast, 17beta-estradiol failed to stimulate the growth of hOSE cells. As estrogen down-regulated GnRH and GnRHR mRNA, we investigated whether estrogen treatment blocks the growth inhibitory effect of a GnRH agonist in OVCAR-3 and hOSE cells. Cells were treated with 17beta-estradiol (10(-7) M) together with (D-Ala(6))-GnRH (10(-7) M), and the proliferative index of cells was measured. Pre- or cotreatment of cells with 17beta-estradiol significantly attenuated the growth inhibitory effect of the GnRH agonist in OVCAR-3 cells, whereas no effect of 17ss-estradiol treatment was observed in hOSE cells. To our knowledge, these results provide the first demonstration of a potential interaction between the estradiol/ER and GnRH/GnRHR systems, which may be important in the growth regulation of normal and neoplastic hOSE cells.

Cell Division↗

Estradiol up-regulates antiapoptotic Bcl-2 messenger ribonucleic acid and protein in tumorigenic ovarian surface epithelium cells.

Most epithelial ovarian tumors appear to arise from the ovarian surface epithelium (OSE). Even though it has been suggested that estrogen may be associated with ovarian tumorigenesis, the exact role of estrogen in the regulation of apoptosis in neoplastic OSE cells remains uncertain. Immortalized OSE (IOSE) cell lines were generated from human normal OSE. These cell lines represent early neoplastic (IOSE-29), tumorigenic (IOSE-29EC), and late neoplastic (IOSE-29EC/T4 and IOSE-29EC/T5) transformation stages from human normal OSE. The present studies demonstrated that both mRNAs and proteins of estrogen receptor (ER) alpha and beta were expressed in IOSE cell lines. No difference was observed in normal OSE and IOSE-29 cells, whereas treatment with 17beta-estradiol (E(2); 10(-8)-10(-6) M) resulted in an increased thymidine incorporation and DNA content per culture in IOSE-29EC cells. This effect of E(2) was attenuated with tamoxifen treatment (10(-6) M), the estrogen antagonist, suggesting that the effect of E(2) is mediated through specific ERs. There was no stimulatory effect on thymidine incorporation before day 6, but after 6 days of E(2) treatment, thymidine incorporation was significantly increased. Because the ratio of thymidine incorporation to DNA content per culture did not change, this E(2) effect does not appear to indicate stimulation of proliferation but, rather, inhibition of apoptosis. In addition, treatment with tamoxifen (10(-6) M) induced apoptosis up to 3-fold in IOSE-29EC cells, whereas cotreatment with E(2) (10(-8)-10(-6) M) plus tamoxifen attenuated tamoxifen-induced apoptosis in a dose-dependent manner. Both proapoptotic bax and antiapoptotic bcl-2 at messenger RNA (mRNA) and protein levels were expressed in IOSE cell lines. Interestingly, treatments with E(2) resulted in a significant increase of bcl-2 mRNA and protein levels (2- and 1.7-fold, respectively), whereas no difference was observed in bax mRNA level. Thus, E(2) may enhance survival of IOSE-29EC by up-regulating bcl-2, and antiapoptotic bcl-2 may be a dominant regulator of apoptotic pathway in these cells. In conclusion, the present study indicates that early neoplastic (IOSE-29), tumorigenic (IOSE-29EC), and late neoplastic (IOSE-29EC/T4 and T5) OSE cells expressed both ERalpha and ERbeta at the mRNA and protein levels. In addition, E(2) prevented tamoxifen induced-apoptosis through ERs. The mechanism of E(2) action may be associated with up-regulation of bcl-2 gene at mRNA and protein levels. These results suggest that estrogen may play a role in ovarian tumorigenesis by preventing apoptosis in tumorigenic OSE cells.

Apoptosis↗

Expression and antiproliferative effect of a second form of gonadotropin-releasing hormone in normal and neoplastic ovarian surface epithelial cells.

Epithelial ovarian carcinomas are the most common cause of death from gynecological malignancies and appear to arise from ovarian surface epithelium (OSE), but the exact mechanism of ovarian tumorigenesis has not been elucidated. Recent cloning of a second form of gonadotropin-releasing hormone (GnRH-II) has been reported in various human tissues including the ovary. However, the expression and role of GnRH-II in human OSE and ovarian carcinomas is not known. In the present study, we demonstrated that in addition to the GnRH receptor (GnRH-R), GnRH-II mRNA is expressed in normal OSE, immortalized OSE (IOSE) cells, primary cultures of ovarian tumors and ovarian cancer cell lines. Treatments with increasing doses (10(-9)-10(-7) M) of GnRH-I and -II resulted in a growth-inhibition in both non-tumorigenic IOSE-29 and tumorigenic IOSE-29EC cells. These results indicate for the first time the expression and potential anti-proliferative effect of GnRH-II, suggesting that GnRH-II, similar to GnRH-I, may have a growth-regulatory effect in normal and neoplastic OSE cells.

Cell Division↗

The regulation of apoptosis by activin and transforming growth factor-beta in early neoplastic and tumorigenic ovarian surface epithelium.

Most ovarian neoplasms arise from the ovarian surface epithelium (OSE), and multiple growth factors have been implicated to influence the transformation from OSE. The present study was performed to investigate the role of activin and transforming growth factor-beta (TGFbeta) in normal and neoplastic OSE cells. An immortalized OSE cell line (IOSE-29) was generated from normal OSE by transfecting simian virus 40 large T antigen and was rendered tumorigenic after subsequent transfection with the E-cadherin gene (IOSE-29EC). The activin/inhibin subunits and activin receptors were expressed at both messenger ribonucleic acids and protein levels in these cells, suggesting that activin may have an autocrine role in neoplastic OSE cells. Treatments with activin (1-100 ng/mL) resulted in a significant decrease in cell proliferation in both IOSE-29 and IOSE-29EC cells, although we have shown that it stimulated the growth of ovarian cancer cells and had no effect on normal OSE. This inhibitory effect was attenuated with cotreatment with follistatin. Treatment with TGFbeta (0.1-10 ng/mL) also significantly decreased the proliferation of normal, IOSE-29, and IOSE-29EC cells in a dose-dependent manner. In addition, treatments with both activin and TGFbeta resulted in an increase in DNA fragmentation in IOSE-29EC cells in a dose-dependent manner. This apoptotic effect of activin was attenuated by cotreatment with follistatin. Treatment with TGFbeta (1 and 10 ng/mL) resulted in a significant decrease in Bcl-2 protein (up to 50%) in IOSE-29EC, whereas no difference was observed in Bax protein levels. Therefore, down-regulated Bcl-2 by TGFbeta may eventually induce apoptosis in IOSE-29EC cells. In contrast, no difference was observed in Bax and Bcl-2 protein expression after treatment with activin. In conclusion, the present study indicates that activin and TGFbeta inhibited growth and induced apoptosis in early neoplastic (IOSE-29) and tumorigenic OSE (IOSE-29EC) cells. Furthermore, antiapoptotic Bcl-2 protein was down-regulated by TGFbeta, whereas no difference was produced in Bax protein by activin or TGFbeta treatment or in Bcl-2 protein by activin. These results suggest that activin and TGFbeta may play a role in growth inhibition and induction of apoptosis in early neoplastic and tumorigenic stage of ovarian cancer.

Activin Receptors↗

Differentiation and growth potential of human ovarian surface epithelial cells expressing temperature-sensitive SV40 T antigen.

The epithelial ovarian carcinomas arise in the ovarian surface epithelium (OSE) which is the mesothelial covering of the ovary. Studies of human USE have been hampered by the small amounts and limited lifespan of this epithelium in culture. OSE cells expressing SV40 large T antigen (Tag) or the HPV genes E6 and E7 have increased growth potentials but lack some of the normal characteristics of OSE. In this study, we used conditional SV40 Tag expression to produce OSE cells with increased proliferative potentials but relatively normal phenotypes. Primary OSE cultures from three women, one of whom had a BRCA1 mutation, were infected with a temperature-sensitive Tag construct (tsTag), and from these, 28 monoclonal and four polyclonal lines were isolated. The effects of temperature changes were examined in two monoclonal and two polyclonal lines. At the permissive temperature (34 degrees C), these cell lines underwent 52-71 population doublings (PD) compared to 15-20 PD for normal OSE. Nuclear SV40-Tag and p53 expression, demonstrated by immunofluorescence, showed that tsTag was uniformly present and biologically active in all lines. At 34 degrees C, culture morphologies ranged from epithelial to mesenchymal. The mean percentage of cells expressing the epithelial differentiation marker, keratin. varied between lines from 20 to 97%. Collagen type III, a mesenchymal marker expressed by OSE in response to explantation into culture, was present in 24-43% of cells. At 39 degrees C, tsTag was inactivated by 2 d while nuclear p53 staining diminished to control levels over 2 wk. Over 3 d. the cells assumed more epithelial morphologies, keratin expression reached 85-100% in all lines and collagen expression increased significantly in two lines. The cultures with the BRCA1 mutation expressed the most keratin and the least collage n III at both temperatures. As indicated by beta-galactosidase staining at pH 6.0, changes leading to senescence were initiated at 39 degrees C by 6 h and were present in all cells after 24 h. However, the cells underwent 1-3 population doublings over up to 1 wk before growth arrest and widespread cell death, thus providing an experimental system where large numbers of OSE cells with different genetic backgrounds and growth potentials can be studied without the concurrent influence of Tag.

Antigens, Polyomavirus Transforming↗

An ovarian adenocarcinoma line derived from SV40/E-cadherin-transfected normal human ovarian surface epithelium.

Epithelial ovarian carcinomas are thought to originate in the ovarian surface epithelium (OSE), i.e., the mesothelium covering the ovary, but experimental evidence for this origin has been lacking. Contrary to most epithelia, where neoplastic progression is associated with a reduction of E-cadherin, this cell-cell adhesion molecule is sparse in normal human OSE but its expression increases with the development of ovarian epithelial metaplasia and neoplasia. Concurrently, the tumors tend to acquire characteristics of the complex epithelia of the oviduct and uterus. The high proportion of ovarian cancers where such aberrant Mullerian differentiation occurs suggests that this change may confer a selective advantage on the transforming cells. We previously demonstrated that increased E-cadherin expression may be a cause, rather than a consequence, of such Mullerian differentiation. E-cadherin was transfected into SV40 large T antigen-immortalized, E-cadherin-negative cells derived from normal OSE. Constitutive expression of E-cadherin re-established normal epithelial markers that had been lost in culture, such as keratin, and induced markers of metaplasia and neoplasia, such as CA125. In the present study, SV40-immortalized, E-cadherin-transfected cells, but not the E-cadherin-negative controls, were found to be anchorage-independent and to form transplantable, invasive s.c. and i.p. adenocarcinomas in 100% of injected SCID mice. Tumor cells injected i.p. seeded the mesenteries and omentum, invaded the liver and thigh musculature and produced ascites. The presence of SV40 large T antigen in the tumor cell nuclei confirmed their origin as transfected OSE cells. Our results demonstrate that ovarian adenocarcinomas can be derived by genetic manipulation of normal human OSE.

Adenocarcinoma↗

Hepatocyte growth factor promotes in vitro scattering and morphogenesis of human cervical carcinoma cells.

OBJECTIVE: Hepatocyte growth factor (HGF) enhances cell dissociation and morphogenesis in many forms of carcinomas including some, but not all, cervical carcinomas. In this study, we examined the effects of HGF on two cervical cancer cell lines, derived from the same tumor, with different growth patterns in vivo and in vitro. METHODS: Two cell lines, derived from the same cervical carcinoma, express spinous (C-4I) and basal (C4-II) squamous cell differentiation, respectively. A cell scattering assay was used to determine whether HGF would stimulate cell dissociation and motility. The morphogenetic capacity of HGF was assessed in collagen gel cultures, expression of the HGF receptor c-Met by Western blot analysis, and cadherin expression by immunofluorescence microscopy. RESULTS: HGF-induced cell scattering was intense in C-4II, but limited in C-4I cultures. In collagen gels, C-4I cells formed large, spherical compact colonies with necrotic centers while C-4II cells formed small, irregular colonies with no necrosis. HGF induced proliferation and branching morphogenesis in both lines, but more prominently in C-4II cultures. There was no difference in c-Met or E- and P-cadherin expression between C-4I and C-4II cultures, but the lines differed in their signal transduction responses to HGF. The scatter response was mediated primarily by phosphatidylinositol 3-kinase in line C-4I, but by mitogen-activated protein kinase in line C-4II. HGF induced collagen gel contraction by C-4 cells, demonstrating for the first time that HGF has the capacity to induce this function. CONCLUSIONS: The HGF-induced cell dispersion, morphogenesis, and collagen gel contraction in two cervical carcinoma cell lines were greatly influenced by differences between the lines in differentiation-associated properties. These properties, which include variations in extracellular matrix, junctional proteins, and signal transduction, may also modulate HGF action in vivo and thus determine patterns of invasiveness and growth of cervical carcinomas.

Animals↗

Presence of activin signal transduction in normal ovarian cells and epithelial ovarian carcinoma.

In this study, we have investigated the expression of inhibin subunits and activin receptors (ActRs) in normal and malignant ovarian cells. Each product of the inhibin subunits (alpha, betaa, betab) and activin receptors (ActRs) amplified by reverse transcription polymerase chain reaction were detected as a single band in human granulosa cells, surface epithelial cells (OSE), and the ovarian cancer cell lines OVCAR 3 and SKOV 3. Western blot analysis was performed using polyclonal antibodies against ActR IIa or IIb peptides based on 13 COOH-terminal amino acids; cultured human granulosa cells were used as a positive control. Using ActR IIa antibody, one major band corresponding to approximately 80 kDa and one minor band corresponding to 105 kDa were observed in the samples. One single band at approximately 60 kDa was detected in OVCAR 3 and a 50 kDa band was detected with ActR IIb antibody in cultured granulosa cell, OSE and SKOV 3. Although no detectable change was induced in Smad 4 mRNA in OVCAR 3, Smad 2 mRNA levels were increased during 48 h treatment with activin A (50 ng ml(-1)). These data provide a better understanding as the first step in the mechanism of action of the activin in the epithelial ovarian carcinoma.

Activin Receptors↗

Role of gonadotropin-releasing hormone as an autocrine growth factor in human ovarian surface epithelium.

Epithelial ovarian cancer, which accounts for 80-90% of all ovarian cancers, is the most common cause of death from gynecological malignancies and is believed to originate from the ovarian surface epithelium. In the present study we investigated the expression of GnRH and its receptor in human ovarian surface epithelial (hOSE) cells and provided novel evidence that GnRH may have antiproliferative effects in this tissue. Using RT-PCR and Southern blot analysis, we cloned the GnRH and GnRH receptor (GnRHR) in hOSE cells. Sequence analysis revealed that GnRH and its receptor have sequences identical to those found in the hypothalamus and pituitary, respectively. To address whether GnRH regulates its own and receptor messenger RNA (mRNA), the cells were treated with different concentrations of the GnRH agonist (D-Ala6)-GnRH. Expression levels of GnRH and its receptor were investigated using quantitative and competitive RT-PCR, respectively. Interestingly, a biphasic effect was observed for the GnRH and GnRHR mRNA levels. High concentrations of the GnRH agonist (10(-7) and 10(-9) M) decreased GnRH and GnRHR mRNA levels, whereas a low concentration (10(-11) M) resulted in up-regulation of GnRH and receptor mRNA levels. Treatment with the GnRH antagonist, antide, prevented the biphasic effects of the GnRH agonist in hOSE cells, confirming the specificity of the response. Furthermore, to investigate the physiological significance, we studied receptor-mediated growth regulatory effects of GnRH in human ovarian surface epithelial cells. The cells were treated with GnRH analogs, and the proliferative index of cells was measured using a [3H]thymidine incorporation assay. (D-Ala6)-GnRH had a direct inhibitory effect on the growth of hOSE cells in a time- and dose-dependent manner. This antiproliferative effect of the GnRH agonist was receptor mediated, as cotreatment of hOSE cells with antide abolished the growth inhibitory effects of the GnRH agonist. The results strongly suggest that GnRH can act as an autocrine/paracrine regulator in hOSE cells.

Autocrine Communication↗

E-cadherin induces mesenchymal-to-epithelial transition in human ovarian surface epithelium.

Ovarian carcinomas are thought to arise in the ovarian surface epithelium (OSE). Although this tissue forms a simple epithelial covering on the ovarian surface, OSE cells exhibit some mesenchymal characteristics and contain little or no E-cadherin. However, E-cadherin is present in metaplastic OSE cells that resemble the more complex epithelia of the oviduct, endometrium and endocervix, and in primary epithelial ovarian carcinomas. To determine whether E-cadherin was a cause or consequence of OSE metaplasia, we expressed this cell-adhesion molecule in simian virus 40-immortalized OSE cells. In these cells the exogenous E-cadherin, all three catenins, and F-actin localized at sites of cell-cell contact, indicating the formation of functional adherens junctions. Unlike the parent OSE cell line, which had undergone a typical mesenchymal transformation in culture, E-cadherin-expressing cells contained cytokeratins and the tight-junction protein occludin. They also formed cobblestone monolayers in two-dimensional culture and simple epithelia in three-dimensional culture that produced CA125 and shed it into the culture medium. CA125 is a normal epithelial-differentiation product of the oviduct, endometrium, and endocervix, but not of normal OSE. It is also a tumor antigen that is produced by ovarian neoplasms and by metaplastic OSE. Thus, E-cadherin restored some normal characteristics of OSE, such as keratin, and it also induced epithelial-differentiation markers associated with weakly preneoplastic, metaplastic OSE and OSE-derived primary carcinomas. The results suggest an unexpected role for E-cadherin in ovarian neoplastic progression.

Actins↗

Constitutive and conditional cadherin expression in cultured human ovarian surface epithelium: influence of family history of ovarian cancer.

Epithelial ovarian carcinomas arise in a simple mesothelium (ovarian surface epithelium, OSE) but exhibit properties of oviductal and endometrial epithelia. Thus, during malignant progression, their differentiation proceeds from simple to complex, in contrast to carcinomas in other tissues. Related changes in OSE of women with a history of familial ovarian cancer indicate that this aberrant differentiation is initiated very early in neoplastic progression. The mechanisms underlying this process are not understood. Because cadherins are known regulators of differentiation, we investigated the relationship of the cadherins E, N and P to OSE morphology, growth patterns and differentiation in cultures of normal and metaplastic OSE from women with (FH-OSE) and without (NFH-OSE) a family history of ovarian cancer and in the ovarian carcinoma lines OVCAR-3 and CaOV3. We used immunofluorescence, RT-PCR, in situ hybridization and Western blotting. Our results define N-cadherin as the constitutively expressed cadherin of normal and metaplastic OSE and indicate that P-cadherin is undetectable while E-cadherin expression is conditional and related to genotype, stage of neoplastic progression and growth pattern. The altered expression of E-cadherin in apparently normal OSE of women with hereditary ovarian cancer syndromes in conjunction with the known capacity of E-cadherin to induce epithelial characteristics implicates this adhesion molecule as a possible inducer of the aberrant Mullerian differentiation which characterizes epithelial ovarian carcinomas. Abnormal differentiation in such (pre)-neoplastic tissues may represent an early, irreversible, non-mutational step in ovarian epithelial neoplastic progression.

Adult↗

Regulation of proliferation and apoptosis by epidermal growth factor and protein kinase C in human ovarian surface epithelial cells.

Epidermal growth factor (EGF) is produced in the ovary and influences proliferation of the malignant ovarian surface epithelium (OSE); yet its role in malignancy or in regulating the normal surface epithelium is unclear. In human OSE cells derived from primary cultures of normal tissue transfected with SV40 large T antigen (IOSE cells), EGF promoted survival but not proliferation. This survival effect was reversed by acute treatment with the phorbol ester, 12-0-tetradecanoyl-13-phorbol acetate (TPA) which alone markedly inhibited IOSE proliferation. We tested whether the activities of the mitogen-activated protein kinases (ERK1/2 and JNK1) varied in response to EGF, TPA, or combinations of these agonists and if the same treatments altered patterns of immediate early gene expression. Alone, EGF activated ERK1/2, increased and sustained levels of c-jun mRNA, but had almost no effect on JNK1 activation. Conversely, PKC activation resulted in a rapid, but transient induction of c-fos RNA and of both kinases, JNK1 and ERK2. When combined, EGF and TPA further enhanced the phosphorylation of both enzymes despite inhibiting survival. Though JNKs and ERKs are thought to transduce opposing cellular responses, in IOSE cells, robust costimulation of the JNK and ERK pathways may redirect the survival message.

Apoptosis↗