Detection of mRNA expression of gonadotropin-releasing hormone and its receptor in normal and neoplastic rat prostates

Hypothalamic gonadotropin-releasing hormone (GnRH) plays a central role in the regulation of the mammalian reproductive systems as a releasing hormone of pituitary gonadotropins. However, a number of studies have shown that GnRH or its receptor are also expressed in some reproductive organs including prostate gland, mammary gland, ovary and placenta, tumors and tumor cell lines derived from these organs, suggesting that this peptide hormone may have other extrapituitary functions in addition to its role as a gonadotropin-releasing hormone. Moreover, it has been demonstrated that GnRH analogs exert some direct inhibitory effects on the proliferation of human and rat prostate cancer cells, probably mediated by its own specific receptors expressed in these tumor cells. In the present study, we investigated the mRNA expression of GnRH and its receptor in normal Noble rat prostate gland, and in three rat models of prostate cancer including the sex hormone-induced Noble rat model, an androgen-independent Noble rat prostatic tumor (AIT) and Dunning rat prostatic adenocarcinomas by RT-PCR and Southern blot analyses. The results showed that GnRH mRNA was expressed in the normal, hormone-treated and neoplastic rat prostates, in addition to its positive control expression in the hypothalamus, whereas its receptor was only detected in the androgen-dependent Dunning R3327H tumor. The detection of both GnRH and its receptor in the androgen-dependent Dunning R3327H tumor tissue suggests that this peptide hormone may have some autocrine and paracrine regulatory functions in this tumor. However, the gene expression of GnRH receptor was not detected in two androgen-independent Dunning tumor sublines and the Noble rat prostatic tumor, AIT, suggesting that the expression of GnRH receptor is lost or down-regulated in the prostatic tumors during the progression to a hormone-independent phenotype.

Kaposiform hemangioendothelioma: five patients with cutaneous lesion and long follow-up

Kaposiform hemangioendothelioma is a rare locally aggressive vascular tumor of the skin, deep soft tissue, and bone in children, characterized by infiltrating nodules and sheets of spindle cells, and unmistakable resemblance to Kaposi's sarcoma. More than 60 patients with such tumor have been reported so far, and while many have died as a result of extensive disease and severe coagulopathy, the long-term biologic behavior of this tumor remains undetermined. We describe five patients with kaposiform hemangioendothelioma and a mean follow-up of 19 years, ranging from 8 to 35 years. This report emphasizes on the importance of cutaneous lesions being the most commonly affected site, but also for its clinical diversity. Early diagnosis is possible even for a small skin lesion, which may be critical for the treatment of a potentially fatal deep-seated extensive tumor. All five patients are well, and three of them with persistent vascular tumor, which has carried two patients from childhood to adult. Although the behavior of this tumor might have been modified by radiation or interferon in three patients, this series indicates that kaposiform hemangioendothelioma is incapable of metastasis, despite a protracted course of many decades with no tendency for spontaneous regression.

Interaction of prostaglandin F(2alpha) and prostaglandin E(2) on progesterone production in human granulosa-luteal cells

This study examined the effects of prostaglandin-F(2alpha) (PGF(2alpha)), prostaglandin-E(2) (PGE(2)) and their interactions on progesterone production in human granulosa-luteal cells (GLCs). Human GLCs collected from in vitro fertilization patients were cultured for 1 (D(1)) or 8 days (D(8)), followed by a 24-hour treatment period, after which media were collected and radioimmunoassayed for progesterone. Seven-point PGF(2alpha) and PGE(2) concentration-response curves were crossed into a matrix of 49 separate treatments. Responses were plotted in three dimensions and as two-dimensional "slices". In D(1) cultured human GLCs neither PGF(2alpha) nor PGE(2) alone had any effect on progesterone production, however two different combinations of these hormones led to at least a 3-fold increase in progesterone production. This stimulation was seen when cells were treated with 10(-6) M PGF(2alpha) plus 10(-9) M PGE(2), and when they were treated with 10(-10) M PGF(2alpha) plus 10(-9) M PGE(2). In D(8) GLCs, PGF(2alpha) stimulated progesterone production maximally at 10(-9) M, while the lowest (10(-11) M) and highest concentrations (10(-6) M) tested were ineffectual. On the contrary, in the presence of high concentrations of PGE(2) (10(-6) to 10(-7) M), PGF(2alpha)-mediated stimulation of progesterone production was attenuated. In a similar fashion to PGF(2alpha), PGE(2) also acted in a luteotrophic manner, although the maximal stimulation of progesterone production was seen at a higher concentration (10(-8) to 10(-7) M). Likewise, PGE(2)-mediated progesterone production was attenuated by the presence of high concentrations of PGF(2alpha) (10(-6) to 10(-7) M). In conclusion, in D(1) human GLCs neither PGF(2alpha) nor PGE(2) alone were luteotrophic, although specific combinations of these hormones were. Conversely, in D(8) GLCs both PGF(2alpha) and PGE(2) stimulated progesterone production in a biphasic manner, while the presence of a high concentration of either of these prostaglandins attenuated the luteotrophic effects of the other. Therefore, PGF(2alpha) and PGE(2) interacted in a concentration-dependent manner, resulting in a multimodal progesterone response, which was easily visualized using three-dimensional plots.

Clinical significance of P-glycoprotein immunohistochemistry and doxorubicin binding assay in patients with osteosarcoma

In 45 osteosarcoma patients, mean age 18 (4-61) years and followed for 14 (5-48) months, we studied the sensitivity to doxorubicin as well as P-glycoprotein expression, and compared these with the extent of tumour necrosis following chemotherapy. Doxorubicin assay was positive in 37 patients in whom necrosis induced by chemotherapy was good in 20 and poor in 17. Metastases developed in nine patients. In eight patients in whom doxorubicin assay indicated tumour resistance, chemonecrosis was poor and all developed pulmonary metastases. P-glycoprotein was studied in pre-treatment biopsies and post-treatment resection specimens. Its expression was positive in 16 patients in whom the necrosis induced by chemotherapy was good in four and poor in 12. In 29 patients with negative P-glycoprotein expression, necrosis was good in 16 and poor in 13. The doxorubicin sensitivity had a high correlation with chemonecrosis (P=0.006) and the incidence of metastases (P<0.001). However, P-glycoprotein expression at the time of diagnosis did not correlate statistically with chemonecrosis (P=0.066). Doxorubicin sensitivity prior to treatment is a better determinant of the response to chemotherapy and clinical outcome than is the P-glycoprotein expression.

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.

Direct action of melatonin in human granulosa-luteal cells

The direct involvement of melatonin in modulation of ovarian steroidogenesis, the high levels of melatonin found in human follicular fluid, and the presence of melatonin binding sites in the ovary led us to hypothesize that melatonin acts as a modulator of ovarian function. In contrast to the hypothalamus and pituitary, the mechanism of melatonin action at the level of the ovary is still poorly understood. In the present study, we investigated the gene expression of the two different forms of melatonin receptors in human granulosa-luteal cells, using RT-PCR. PCR products corresponding to the expected sizes of the melatonin receptor subtypes, mt(1)-R and MT(2)-R, were obtained from granulosa-luteal cells, and the authenticity of the PCR products was confirmed by Southern blot hybridization with cDNA probes. Subsequent cloning and sequence analysis revealed that the ovarian mt(1)-R and MT(2)-R cDNAs are identical to their brain counterparts. Because gonadotropins and GnRH acting through specific receptors in the human ovary regulate cellular functions, we investigated the role of melatonin in the regulation of FSH receptor, LH receptor, GnRH, and GnRH receptor levels. Treatment with melatonin (10 pM-100 nM) significantly increased LH receptor mRNA levels without altering the expression of the FSH receptor gene. Both GnRH and GnRH receptor mRNA levels were significantly decreased, to 61% and 45% of control levels, respectively, after melatonin treatment. Melatonin treatment alone had no effect on basal progesterone production but enhanced the effects of human CG-stimulated progesterone production. Because MAPKs are activated in response to a diverse array of extracellular stimuli leading to the regulation of cell growth, division, and differentiation, and because melatonin has been shown to modulate cellular proliferation and differentiation, in this study, we demonstrated that melatonin activated MAPK in a dose- and time-dependent manner. In summary, our studies demonstrate, for the first time, that melatonin can regulate progesterone production, LH receptor, GnRH, and GnRH receptor gene expression through melatonin receptors in human granulosa-luteal cells, which may be mediated via the MAPK pathway and activation of Elk-1. Our results support the notion that melatonin plays a direct role in regulating ovarian function.

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.

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.

Human gonadotropin-releasing hormone receptor gene transcription: up-regulation by 3',5'-cyclic adenosine monophosphate/protein kinase A pathway

Transient transfection of mouse gonadotrope-derived (alphaT3-1) cells with a 2297 bp human GnRHR promoter-luciferase construct (p2300-LucF) showed a dose- and time-dependent increase in the human gonodotropin-releasing hormone receptor (GnRHR) promoter activity after forskolin treatment. An average of 4.8-fold increase in promoter activity was observed after 12 h of 10 microM forskolin treatment. This effect was mimicked by administration of cholera toxin, cAMP analog or pituitary adenylate cyclase activating polypeptide 38 (PACAP). A specific adenylate cyclase (AC) inhibitor (ACI) or protein kinase A (PKA) inhibitor (PKAI) pretreatment reversed the forskolin- and PACAP-induced increase in the human GnRHR promoter activity. These results not only confirm the stimulatory effect of Cyclic adenosine monophosphate (cAMP) in human GnRHR promoter activation, but also suggest that hormones or neurotransmitters that activate adenylate cyclase in pituitary gonadotropes may increase the expression of human GnRHR gene in transcriptional level. Progressive 5' deletion assays identified a 412 bp fragment (-577 to 167) in the human GnRHR 5'-flanking region that is essential in maintaining the basal responsiveness to cAMP. Mutagenesis coupled with functional studies have identified two putative AP-1/CREB binding sites, namely hGR-AP/CRE-1 and hGR-AP/CRE-2 that participated in mediating the cAMP-stimulatory effect. Mutation of the putative hGR-AP/CRE-1 and hGR-CRE-2 resulted in a 38 and 32% decrease in the forskolin-induced stimulation. However, mutation of both binding sites did not completely abolish the cAMP-stimulatory effect, suggesting that multiple transcription factor binding sites were involved in full response in cAMP stimulation. The binding of CREB to these motifs was confirmed by gel mobility shift assay and antibody supershift assay.

Soy intake and the maintenance of peak bone mass in Hong Kong Chinese women

Our previous study on bone health among premenopausal women showed that bone mass consolidation is attained by the early 30s, and small loss of spinal bone mineral density (SBMD) occurs soon after peak bone mass attainment. Recent interest has been shown in the potential beneficial effects of phytoestrogens on bone health. However, data are lacking, particularly in Asian women. This study aims to investigate the effect of soy isoflavones intake on the maintenance of peak bone mass in a cohort of 132 women aged 30-40 years who were followed up for 3 years. Baseline measurements of SBMD (L2-L4) were obtained using dual-energy X-ray densitometry, and dietary intake of soy foods and other key nutrients, including dietary calcium, were obtained through a quantitative food frequency method. Information on body measurements; physical activity (PA), weight-bearing activity in particular; age of menarche; and number of pregnancies were obtained at baseline. Repeated measurements of SBMD were obtained yearly for a further 3 years with an average follow-up time of 38 months. Analyses were performed on 116 subjects with at least three SBMD measurements (at baseline, 3-year follow-up, and at least one measurement during follow-up). The individual SBMD regression slope was computed for each of the subjects. Soy isoflavones consumption was categorized as quartiles of intake. We observed a significant difference in the SBMD individual regression slopes between women belonging to the fourth and first soy isoflavones intake quartiles. The positive effect of soy isoflavones on SBMD remained after adjusting for age and body size (height, weight, and bone area). Multiple linear regression analysis including the other known covariates (lean body mass, PA, energy adjusted calcium, and follow-up time) showed that soy isoflavones, together with these variables, accounted for 24% of the variances of the SBMD individual regression slope. This longitudinal study shows that soy intake had a significant effect on the maintenance of SBMD in women aged 30-40 years. The effects of phytoestrogens on bone health should be explored further in a population with habitual dietary soy but low calcium intake.

Antigonadotropic action of adenosine triphosphate in human granulosa-luteal cells: involvement of protein kinase Calpha

The presence of P2U purinoceptor in human granulosa-luteal cells (hGLCs) indicates a potential role of ATP in regulating ovarian function. In this study an inhibitory effect of ATP on hCG-induced cAMP production was observed. Extracellular ATP has been shown to activate protein kinase C (PKC) after binding to a purinoceptor. To understand the role of PKC in mediating ATP action, hCG-stimulated cAMP level was examined in the presence of the PKC activator, 1 micromol/L phorbol 12-myristate 13-acetate (PMA), or the PKC inhibitor, 1 micromol/L staurosporin or 1 micromol/L bisindolylmaleimide I. PMA, like 10 micromol/L ATP, significantly reduced hCG-evoked cAMP production. In addition, the inhibitory effect of ATP was reversed by staurosporin and bisindolylmaleimide I. To further investigate the involvement of PKC isoforms in mediating the inhibitory effect of ATP, the presence of PKC isoforms in cultured hGLCs was examined by Western blot using monoclonal antibodies against specific isoforms. Translocation of PKC isoforms from cytosolic fraction to membrane fraction was studied to identify the active PKC isozymes subsequent to ATP treatment. The change in PKC isoform in PKC-depleted cells (achieved by exposure to PMA for 18 h) was also examined. Our results demonstrated the presence of PKCalpha, -delta, -iota, and -lambda isoforms in hGLCs and the translocation of PKCalpha subsequent to ATP treatment. In PKC-depleted cells the PKCalpha level was reduced, and no significant effect of ATP on hCG-stimulated cAMP production was observed. To our knowledge, this is the first demonstration of PKC isoforms in hGLCs and the involvement of activated PKC in mediating the antigonadotropic effect of extracellular ATP. Taken together, these results further support a role of this neurotransmitter in regulating human ovarian function.

In situ model for studying potassium currents in various growth plate chondrocyte subpopulations

A new in situ model of partially digested growth plate cartilage suitable for patch clamp study of membrane currents of chondrocytes from various differentiation stages was developed. Thin sections of growth plate were enzyme digested to expose intact membranes of chondrocytes previously covered by extracellular matrix. This treatment dramatically increased the success rate of tight-seal formation from virtually 0% up to 40%. Whole-cell patch clamp recording revealed a delayed outward rectifying current as the major macroscopic current in chondrocytes of all differentiation stages. This current was sensitive to tetraethylammonium chloride and reversed polarity at a membrane potential close to the equilibrium potential of K+. Chondrocytes at resting stage expressed a much smaller K+ current than the proliferative and hypertrophic chondrocytes. When the current amplitudes were normalized for the cell membrane area, proliferative cells expressed a significantly higher outward current density.

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.

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.

Interplay of pituitary adenylate cyclase-activating polypeptide with a silencer element to regulate the upstream promoter of the human gonadotropin-releasing hormone receptor gene

Multiple transcription start sites were identified in the human gonadotropin releasing hormone receptor (hGnRHR) gene. Recently, an upstream promoter residing at -1727/-1674, in vicinity of a CAP site at -1673, was characterized. In this report, we elucidated the underlying mechanisms for the regulation of this promoter. Functionally, this promoter was constitutively suppressed by a silencer element (-1673/-1351) situated immediately downstream to it. On the other hand, pituitary adenylate cyclase-activating polypeptide (PACAP), via the cAMP pathway, was found to be the extracellular cue to control the upstream promoter. Following PACAP-27, PACAP-38 (30 nM) and forskolin (25 microM) treatment, there were significant increases in the reporter gene activities. By deletion analysis, the region residing at -1727 to -1577, containing the distal promoter and 97 bp of the silencer was subsequently found to be responsible for PACAP/cAMP induction. To localize the PACAP-dependent cis-acting element(s) within the silencer, block replacement scanning mutation was performed and a hGnRHR gene PACAP-responsive element (GPRE) was identified at -1676/-1648. The actions of PACAPs and forskolin on the GPRE were further evidenced by gel mobility shift assays. There was an increase in protein binding onto this element only after peptide treatment. As GnRH receptor number on gonadotrope cell surface is a key factor in regulating gonadotropin release, the present study provides an insight into the interplay between PACAP and GnRH receptors on pituitary gonadotropes to control human reproductive functions.

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.

Adenosine triphosphate activates mitogen-activated protein kinase in human granulosa-luteal cells

ATP has been shown to activate the phospholipase C/diacylglycerol/protein kinase C (PKC) pathway. However, little is known about the downstream signaling events. The present study was designed to examine the effect of ATP on activation of the mitogen-activated protein kinase (MAPK) signaling pathway and its physiological role in human granulosa-luteal cells. Western blot analysis, using a monoclonal antibody that detected the phosphorylated forms of extracellular signal-regulated kinase-1 and -2 (p42(mapk) and p44 (mapk), respectively), demonstrated that ATP activated MAPK in a dose- and time-dependent manner. Treatment of the cells with suramin (a P2 purinoceptor antagonist), neomycin (a phospholipase C inhibitor), staurosporin (a PKC inhibitor), or PD98059 (an MAPK/ERK kinase inhibitor) significantly attenuated the ATP-induced activation of MAPK. In contrast, ATP-induced MAPK activation was not significantly affected by pertussis toxin (a G(i) inhibitor). To examine the role of G(s) protein, the intracellular cAMP level was determined after treatment with ATP or hCG. No significant elevation of intracellular cAMP was noted after ATP treatment. To determine the role of MAPK in steroidogenesis, human granulosa-luteal cells were treated with ATP, hCG, or ATP plus hCG in the presence or absence of PD98059. RIA revealed that ATP alone did not significantly affect the basal progesterone concentration. However, hCG-induced progesterone production was reduced by ATP treatment. PD98059 reversed the inhibitory effect of ATP on hCG-induced progesterone production. To our knowledge, this is the first demonstration of ATP-induced activation of the MAPK signaling pathway in the human ovary. These results support the idea that the MAPK signaling pathway is involved in mediating ATP actions in the human ovary.

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.

Functional mapping of a placenta-specific upstream promoter for human gonadotropin-releasing hormone receptor gene

GnRH has been showed to regulate hCG expression and secretion from the placenta through a GnRH receptor (GnRHR)-mediated process. Recently, we have reported the isolation of human GnRHR full-length complementary DNA from the human placental cells including choriocarcinoma JEG-3 cells, immortalized extravillous trophoblasts, and primary cultures of trophoblasts. Despite these observations, the molecular mechanism that controls the transcription regulation of the GnRHR gene expression in the placenta remains unknown. Here we described the identification of an upstream placenta-specific promoter located between nucleotide (nt) -1737 and -1346 (relative to the translation start site) for the human GnRHR gene. Using transient transfection studies, this upstream promoter has been shown to determine the placental cell-specific expression of this gene. Primer extension studies further confirmed the utilization of this promoter in JEG-3 cells in vivo. By mutagenesis coupled to functional studies, we have identified four putative transcription factor-binding sites, namely human glucocorticoid receptor (hGR)-Oct-1 (nt -1718 to -1710), hGR-cAMP response element (CRE; nt -1649 to -1641), hGR-GATA (nt -1602 to -1597), and hGR-activating protein-1 (nt -1518 to -1511), that are essential to the expression of this gene. Mutations of these cis-acting motifs reduced the promoter activity. The CRE and GATA motifs were subsequently shown to be placenta specific, as mutations of these motifs caused a dramatic loss in promoter activities in the placental JEG-3 cells, but not in the ovarian carcinoma OVCAR-3, monkey kidney COS-1, and human embryonic kidney 293 cells. Gel mobility assays confirmed the binding of nuclear proteins Oct-1, CRE-binding protein, GATA-2, GATA-3, c-Fos, and c-Jun from JEG-3 cells to these four elements.

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.

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.

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.

Stimulation of mitogen-activated protein kinase by gonadotropin-releasing hormone in human granulosa-luteal cells

The present study investigated the activation of mitogen-activated protein kinases (MAPKs) by a GnRH agonist (GnRHa) in human granulosa-luteal cells (hGLCs). The phosphorylation state of p44 and p42 MAPK was examined using antibodies that distinguish phospho-p44/42 MAPK (Thr(202)/Tyr(204)) from total p44/42 MAPK (activated plus inactivated). Activation of MAPK by GnRHa was observed within 5 min and was sustained for 60 min after treatment. GnRHa stimulated MAPK activation in a dose-dependent manner, with maximum stimulation (6.7-fold over basal levels) at 10(-7) M. Pretreatment with a protein kinase C (PKC) inhibitor, GF109203X, completely blocked GnRHa-induced MAPK activation. In addition, pretreatment with a PKC activator, phorbol-12-myristate 13-acetate, potentiated GnRH-induced MAPK activation. These results indicate that GnRHa stimulates MAPK activation through a PKC-dependent pathway in hGLCs, possibly coupled to G(q)alpha protein. MAPK activation was also observed in response to 8-bromo-cAMP or cholera toxin, but not pertussis toxin. Forskolin (50 microM) substantially stimulated a rapid cAMP accumulation, whereas GnRHa (10(-7) M) or pertussis toxin (100 mg/ml) did not affect basal intracellular cAMP levels. Cotreatment of GnRHa (10(-7) M) did not attenuate forskolin- or hCG-stimulated cAMP accumulation. These results suggest that the GnRH receptor is probably not coupled to G(s)alpha or G(i)alpha in hGLCs. Finally, GnRHa (10(-7) M) stimulated a significant increase in Elk-1 phosphorylation and c-fos messenger RNA expression, as revealed by an in vitro kinase assay and Northern blot analysis, respectively. These results clearly demonstrate that GnRH activates the MAPK cascade through a PKC-dependent pathway in the human ovary.

Adenosine triphosphate-evoked cytosolic calcium oscillations in human granulosa-luteal cells: role of protein kinase C

ATP has been shown to modulate progesterone production in human granulosa-luteal cells (hGLCs) in vitro. After binding to a G protein-coupled P2 purinergic receptor, ATP stimulates phospholipase C. The resultant production of diacylglycerol and inositol triphosphate activates protein kinase C (PKC) and intracellular calcium [Ca(2+)](i) mobilization, respectively. In the present study, we examined the potential cross-talk between the PKC and Ca(2+) pathway in ATP signal transduction. Specifically, the effect of PKC on regulating ATP-evoked [Ca(2+)](i) oscillations were examined in hGLCs. Using microspectrofluorimetry, [Ca(2+)](i) oscillations were detected in Fura-2 loaded hGLCs in primary culture. The amplitudes of the ATP-triggered [Ca(2+)](i) oscillations were reduced in a dose-dependent manner by pretreating the cells with various concentrations (1 nM to 10 microM) of the PKC activator, phorbol-12-myristate-13-acetate (PMA). A 10 microM concentration of PMA completely suppressed 10 microM ATP-induced oscillations. The inhibitory effect occurred even when PMA was given during the plateau phase of ATP evoked [Ca(2+)](i) oscillations, suggesting that extracellular calcium influx was inhibited. The role of PKC was further substantiated by the observation that, in the presence of a PKC inhibitor, bisindolylmaleimide I, ATP-induced [Ca(2+)](i) oscillations were not completely suppressed by PMA. Furthermore, homologous desensitization of ATP-induced calcium oscillations was partially reversed by bisindolylmaleimide I, suggesting that activated PKC may be involved in the mechanism of desensitization. These results demonstrate that PKC negatively regulates the ATP-evoked [Ca(2+)](i) mobilization from both intracellular stores and extracellular influx in hGLCs and further support a modulatory role of ATP and P2 purinoceptor in ovarian steroidogenesis.