Diverse effects of FSH and LH on proliferation of human ovarian surface epithelial cells

A Comprehensive Molecular and Clinical Analysis of the piRNA Pathway Genes in Ovarian Cancer

Simple Summary

Although ovarian cancer (OC) is one of the most lethal gynecological cancers, its development and progression remain poorly understood. The piRNA pathway is important for transposon defense and genome stability. piRNA maturation and function involve a number of genes known as the piRNA pathway genes. These genes have recently been implicated in cancer development and progression but information about their role in OC is limited. Our work aimed to provide a better understanding of the roles of piRNA pathway genes in OC. Through analyzing changes in the abundance of 10 piRNA pathway genes, we discovered gene expression differences in benign vs. cancer, chemosensitive vs. chemoresistant and post hormone treatment in OC samples and cells. Furthermore, we observed the differential effects of these genes on patient survival and OC cell invasion. Overall, this work supports a role of the piRNA pathway genes in OC progression and encourages further study of their clinical relevance.

Abstract

Ovarian cancer (OC) is one of the most lethal gynecological malignancies, yet molecular mechanisms underlying its origin and progression remain poorly understood. With increasing reports of piRNA pathway deregulation in various cancers, we aimed to better understand its role in OC through a comprehensive analysis of key genes: PIWIL1-4, DDX4, HENMT1, MAEL, PLD6, TDRD1,9 and mutants of PIWIL1 (P1∆17) and PIWIL2 (PL2L60). High-throughput qRT-PCR (n = 45) and CSIOVDB (n = 3431) showed differential gene expression when comparing benign ovarian tumors, low grade OC and high grade serous OC (HGSOC). Significant correlation of disparate piRNA pathway gene expression levels with better progression free, post-progression free and overall survival suggests a complex role of this pathway in OC. We discovered PIWIL3 expression in chemosensitive but not chemoresistant primary HGSOC cells, providing a potential target against chemoresistant disease. As a first, we revealed that follicle stimulating hormone increased PIWIL2 expression in OV-90 cells. PIWIL1, P1∆17, PIWIL2, PL2L60 and MAEL overexpression in vitro and in vivo decreased motility and invasion of OVCAR-3 and OV-90 cells. Interestingly, P1∆17 and PL2L60, induced increased motility and invasion compared to PIWIL1 and PIWIL2. Our results in HGSOC highlight the intricate role piRNA pathway genes play in the development of malignant neoplasms.

Gonadotropins promote human ovarian cancer cell migration and invasion via a cyclooxygenase 2-dependent pathway

It is generally accepted that ovarian cancer is associated with local elevation of gonadotropins (FSH and LH), with repeated ovulation and accompanying expression of inducible cyclooxygenase 2 (COX2). However, the roles of gonadotropins and the concomitant elevation of COX2 in the development of ovarian cancer have not been fully characterized. Herein, we report that excessive FSH/LH exposure did not induce proliferation in ovarian cancer cell lines but significantly promoted cell migration and invasion. Moreover, FSH/LH treatment rapidly upregulated COX2 expression within 24 h, whereas COX1 expression remained unchanged. Further results showed that enhancement of epithelial-mesenchymal transition (EMT) and upregulation of matrix metalloproteinase (MMP)2 and MMP9 contributed to the stimulatory effect of gonadotropins on cell migration and invasion; these effects were sufficiently blocked by a selective COX2 inhibitor. In conclusion, the present study suggests that gonadotropin-induced migration and invasion in ovarian cancer may be caused by EMT and MMP upregulation via a COX2-dependent pathway.

Development of a mouse model of menopausal ovarian cancer

Despite significant understanding of the genetic mutations involved in ovarian epithelial cancer and advances in genomic approaches for expression and mutation profiling of tumor tissues, several key questions in ovarian cancer biology remain enigmatic: the mechanism for the well-established impact of reproductive factors on ovarian cancer risk remains obscure; cell of origin of ovarian cancer continue to be debated; and the precursor lesion, sequence, or events in progression remain to be defined. Suitable mouse models should complement the analysis of human tumor tissues and may provide clues to these questions currently perplexing ovarian cancer biology. A potentially useful model is the germ cell-deficient Wv (white spotting variant) mutant mouse line, which may be used to study the impact of menopausal physiology on the increased risk of ovarian cancer. The Wv mice harbor a point mutation in c-Kit that reduces the receptor tyrosine kinase activity to about 1–5% (it is not a null mutation). Homozygous Wv mutant females have a reduced ovarian germ cell reservoir at birth and the follicles are rapidly depleted upon reaching reproductive maturity, but other biological phenotypes are minimal and the mice have a normal life span. The loss of ovarian function precipitates changes in hormonal and metabolic activity that model features of menopause in humans. As a consequence of follicle depletion, the Wv ovaries develop ovarian tubular adenomas, a benign epithelial tumor corresponding to surface epithelial invaginations and papillomatosis that mark human ovarian aging. Ongoing work will test the possibility of converting the benign epithelial tubular adenomas into neoplastic tumors by addition of an oncogenic mutation, such as of Tp53, to model the genotype and biology of serous ovarian cancer. Model based on the Wv mice may have the potential to gain biological and etiological insights into ovarian cancer development and prevention.

Gonadotropins activate oncogenic pathways to enhance proliferation in normal mouse ovarian surface epithelium

Ovarian cancer is the most lethal gynecological malignancy affecting American women. The gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (LH), have been implicated as growth factors in ovarian cancer. In the present study, pathways activated by FSH and LH in normal ovarian surface epithelium (OSE) grown in their microenvironment were investigated. Gonadotropins increased proliferation in both three-dimensional (3D) ovarian organ culture and in a two-dimensional (2D) normal mouse cell line. A mouse cancer pathway qPCR array using mRNA collected from 3D organ cultures identified Akt as a transcriptionally upregulated target following stimulation with FSH, LH and the combination of FSH and LH. Activation of additional pathways, such as Birc5, Cdk2, Cdk4, and Cdkn2a identified in the 3D organ cultures, were validated by western blot using the 2D cell line. Akt and epidermal growth factor receptor (EGFR) inhibitors blocked gonadotropin-induced cell proliferation in 3D organ and 2D cell culture. OSE isolated from 3D organ cultures stimulated with LH or hydrogen peroxide initiated growth in soft agar. Hydrogen peroxide stimulated colonies were further enhanced when supplemented with FSH. LH colony formation and FSH promotion were blocked by Akt and EGFR inhibitors. These data suggest that the gonadotropins stimulate some of the same proliferative pathways in normal OSE that are activated in ovarian cancers.

Gonadotropin signalling in epithelial ovarian cancer

Ovarian cancer is the most lethal of all gynecologic malignancies, although its aetiology remains poorly understood. A role for the gonadotropins, follicle-stimulating hormone (FSH) and luteinising hormone (LH), has been implicated in a variety of different aspects of ovarian cancer tumorigenesis, including cellular proliferation, migration and invasion. This review focuses on the latest advances in knowledge concerning signalling pathways and functional consequences of gonadotropin action, including changes in protein-, miRNA- and gene expression, in epithelial ovarian cancer cells.

Induction of a menopausal state alters the growth and histology of ovarian tumors in a mouse model of ovarian cancer

OBJECTIVE

Ovarian cancer is often diagnosed in women after menopause when the levels of the serum gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are increased because of the depletion of growing follicles within the ovary. The ability of FSH and LH to modulate the disease has not been well studied owing to a lack of physiologically relevant models of ovarian cancer. In this study, 4-vinylcyclohexene diepoxide (VCD) was used to deplete ovarian follicles and increase the levels of circulating FSH and LH in the tgCAG-LS-TAg mouse model of ovarian cancer.

METHODS

VCD-induced follicle depletion was performed either before or after induction of the oncogene SV40 large and small T-antigens in the ovarian surface epithelial cells of tgCAG-LS-TAg mice, which was mediated by the intrabursal delivery of an adenovirus expressing Cre recombinase (AdCre).

RESULTS

tgCAG-LS-TAg mice injected with AdCre developed undifferentiated ovarian tumors with mixed epithelial and stromal components and some features of sex cord stromal tumors. Treatment with VCD before or after AdCre injection yielded tumors of similar histology, but with the unique appearance of Sertoli cell nests. In mice treated with VCD before the induction of tumorigenesis, the ovarian tumors tended to grow more slowly. The human ovarian cancer cell lines SKOV3 and OVCAR3 responded similarly to increased levels of gonadotropins in a second model of menopause, growing more slowly in ovariectomized mice compared with cycling controls.

CONCLUSIONS

These results suggest that follicle depletion and increased gonadotropin levels can alter the histology and the rate of growth of ovarian tumors.

Dynamics of the primate ovarian surface epithelium during the ovulatory menstrual cycle

BACKGROUND

Epithelial ovarian cancer (EOC) risk correlates strongly with the number of ovulations that a woman experiences. The primary source of EOC in women is the ovarian surface epithelium (OSE). Mechanistic studies on the etiology of OSE transformation to EOC cannot be realistically performed in women. Selecting a suitable animal model to investigate the normal OSE in the context of ovulation should be guided by the model's reproductive similarities to women in natural features that are thought to contribute to EOC risk.

METHODS

We selected the non-human primate, rhesus macaque, as a surrogate to study the normal OSE during the natural menstrual cycle. We investigated OSE morphology and marker expression, plus cell proliferation and death in relation to menstrual cycle stage and ovulation.

RESULTS

OSE cells displayed a morphological range from squamous to columnar. Cycle-independent parameters and cycle-dependent changes were observed for OSE histology, steroid receptor expression, cell death, DNA repair and cell adhesion. Contrary to findings in non-primates, primate OSE cells were not manifestly cleared from the site of ovulation, nor were proliferation rates affected by ovulation or stage of the menstrual cycle. DNA repair proteins were more highly expressed in OSE than in other ovarian cells.

CONCLUSIONS

This study identifies significant differences between primate and non-primate OSE. In contrast to established views, ovulation-induced death and proliferation are not indicated as prominent contributors to EOC risk, but disruption of OSE cadherin-mediated adhesion may be, as could the loss of ovary-mediated chronic suppression of proliferation and elevation of DNA repair potential.

Prediagnostic circulating follicle stimulating hormone concentrations and ovarian cancer risk

Gonadotropins have been indicted in ovarian carcinogenesis but direct evidence has been limited and inconsistent. The aim of this study was to determine the association between prediagnostic levels of follicle stimulating hormone (FSH) and subsequent development of invasive epithelial ovarian cancer. A nested case-control study was conducted using cases and controls drawn from three cohorts: CLUE I and CLUE II of Washington County, MD, and the Island of Guernsey Study, United Kingdom. In total, 67 incident invasive epithelial ovarian cancer cases were each matched to 1 to 2 controls on age, menopausal status, time since last menstrual period, current hormone use and other relevant factors. FSH concentrations were classified into ranked thirds of low, medium or high based on the distribution among controls. Conditional logistic regression was used to estimate the odds ratio (OR) across increasing thirds of FSH concentrations. Results of the analysis showed that ovarian cancer risk decreased with higher FSH concentrations (p-trend = 0.005). Compared with the lowest third of FSH concentrations, the OR among those in the middle and highest thirds were 0.45 [95% Confidence Interval (CI): 0.20-1.00] and 0.26 (95% CI: 0.10-0.70), respectively. Associations persisted after excluding cases diagnosed within 5 years of follow-up. In conclusion, a reduction in subsequent risk of invasive epithelial ovarian cancer was observed among women with higher circulating FSH concentrations. These findings contradict the hypothesized role of FSH as a risk factor in ovarian carcinogenesis.

Gonadotropins and ovarian cancer

Ovarian epithelial cancer (OEC) accounts for 90% of all ovarian cancers and is the leading cause of death from gynecological cancers in North America and Europe. Despite its clinical significance, the factors that regulate the development and progression of ovarian cancer are among the least understood of all major human malignancies. The two gonadotropins, FSH and LH, are key regulators of ovarian cell functions, and the potential role of gonadotropins in the pathogenesis of ovarian cancer is suggested. Ovarian carcinomas have been found to express specific receptors for gonadotropins. The presence of gonadotropins in ovarian tumor fluid suggests the importance of these factors in the transformation and progression of ovarian cancers as well as being prognostic indicators. Functionally, there is evidence showing a direct action of gonadotropins on ovarian tumor cell growth. This review summarizes the key findings and recent advances in our understanding of these peptide hormones in ovarian cancer development and progression and their role in potential future cancer therapy. We will first discuss the supporting evidence and controversies in the "gonadotropin theory" and the use of animal models for exploring the involvement of gonadotropins in the etiology of ovarian cancer. The role of gonadotropins in regulating the proliferation, survival, and metastasis of OEC is next summarized. Relevant data from ovarian surface epithelium, which is widely believed to be the precursor of OEC, are also described. Finally, we will discuss the clinical applications of gonadotropins in ovarian cancer and the recent progress in drug development.

Gonadotropin and its role in the β-catenin/T-cell factor signaling pathway

Gonadotropins, follicle-stimulating hormone and luteinizing hormone are key regulators in ovarian function, acting in an endocrine manner to regulate gametogenesis and steroidogenesis. In addition to normal tissue, gonadotropin receptors have also been demonstrated in ovarian carcinoma cell lines and primary tumors, suggesting that the gonadotropins may play a role in the pathophysiology of ovarian cancer. Thus, understanding mechanisms involved in signaling transduction by the gonadotropin receptors are of considerable interest and potential significance. In the ovary, gonadotropins initiate their cellular responses by binding to their G-protein-coupled receptors and activation of specific downstream intracellular effectors and signal pathways, including those of protein kinases A and C and mitogen-activated protein kinase. Recently, gonadotropins were shown to stimulate nuclear accumulation of β-catenin, which controls lymphoid-enhancing factor/T-cell factor family-sensitive gene expression. β-catenin has a pivotal function in the control of cell fate. The ability of gonadotropins to regulate β-catenin provides a new dimension of knowledge linking pituitary hormones to the β-catenin signaling in normal ovarian physiology and demonstrating how its dysregulation can contribute to the development of ovarian cancer.

E-cadherin expression and bromodeoxyuridine incorporation during development of ovarian inclusion cysts in age-matched breeder and incessantly ovulated CD-1 mice

BACKGROUND

Female CD-1/Swiss Webster mice subjected to incessant ovulation for 8 months and 12-month breeder mice both developed ovarian inclusion cysts similar to serous cystadenomas. The majority of cysts appeared to be dilated rete ovarii tubules, but high ovulation number resulted in more cortical inclusion cysts. We hypothesized that comparison of inclusion cyst pathology in animals of the same age, but with differences in total lifetime ovulation number, might allow us to determine distinguishing characteristics of the two types of cyst.

METHODS

Ovaries from breeder mice (BR) or females subjected to incessant ovulation (IO) were compared at 6-, 9- and 12-months of age. Ovaries were serially sectioned and cysts characterized with regard to location and histology, E-cadherin immunoreactivity and rates of BrdU incorporation.

RESULTS

Inclusion cysts developed with age in BR and IO ovaries. The majority of cysts were connected to the ovarian hilus. Two cortical inclusion cysts were observed in ten IO ovaries and one in ten BR ovaries. Low or no E-cadherin immuno-staining was seen in the OSE of all mice studied. Conversely, strong membrane immuno-staining was observed in rete ovarii epithelial cells. Variable E-cadherin immunoreactivity was seen in cells of hilar inclusion cysts, with strong staining observed in cuboidal ciliated cells and little or no staining in flat epithelial cells. Two of the three cortical cysts contained papillae, which showed E-cadherin immuno-staining at the edge of cells. However hilar and cortical cysts were not distinguishable by morphology, cell type or E-cadherin immunoreactivity. BrdU incorporation in cyst cells (1.4% [95% CI: 1.0 to 2.1]) was greater than in OSE (0.7% [95% CI: 0.4 to 1.2]) and very few BrdU-labeled cells were observed in rete ovarii at any age. Incessant ovulation significantly increased BrdU incorporation in OSE of older animals.

CONCLUSION

These experiments confirm ovarian inclusion cysts develop with age in the CD-1 mouse strain, irrespective of total ovulation burden. We conclude longer periods of incessant ovulation do not lead to significant changes in inclusion cyst formation or steroidogenesis in CD-1 mice and inclusion cyst type can not be distinguished by morphology, cell proliferation rate or E-cadherin immunoreactivity.

Role of endocrine and growth factors on the ovarian surface epithelium

Epithelial ovarian cancer is a highly fatal disease for which prevention strategies have been limited; in part because of our poor understanding of the underlying biology of its precursor, the ovarian surface epithelium (OSE). The OSE is a single layer of flat-to-cuboidal mesothelial cells that covers the surface of the ovary. Despite its inconspicuous appearance in vivo, it is believed that OSE cells actively participate in the cyclical ovulatory rupture and repair process. The continuous rupture of the OSE at ovulation and the subsequent proliferation to repair the wound renders the cells susceptible to genetic damage and malignant transformation. As the ovary is a rich source of multiple hormones, and normal OSE and ovarian carcinomas secrete and have receptors for hormones, growth factors and cytokines, these factors are strong candidates to regulate normal OSE physiology and the transformation and progression of ovarian cancers. In particular, alterations of hormone/growth factor production and receptor expression are common in ovarian tumors. This review summarizes the current knowledge in the field of endocrinology and its relationship to the biology and pathology of the OSE.

Hypercalcemia induced by ovarian clear cell carcinoma producing all transcriptional variants of parathyroid hormone-related peptide gene during pregnancy

BACKGROUND

Parathyroid hormone-related peptide (PTHrP) appears as the major causative agent responsible for the humoral hypercalcemia of malignancy (HHM). However, the use of promoters and splicing patterns of PTHrP gene in HHM have not been reported yet.

CASE

A 35-year-old woman was diagnosed as an ovarian clear cell carcinoma with HHM caused by elevated serum PTHrP after delivery. An immunohistochemical study showed PTHrP expression in the tumor tissue. The Southern blot analysis following RT-PCR confirmed the presence of all types of PTHrP mRNA transcripts produced by a combination of three promoters, one 5' alternative splicing and three alternative 3' splicing events.

CONCLUSION

An ovarian clear cell carcinoma induced PTHrP-related HHM, which resulted from the high expression of all isoforms for PTHrP gene.

Endocrine signaling in ovarian surface epithelium and cancer

Ovarian cancer is the sixth most common cancer and the fifth leading cause of cancer-related death among women in developed countries. Greater than 85% of human ovarian cancer arises within the ovarian surface epithelium (OSE), with the remainder derived from granulosa cells or, rarely, stroma or germ cells. The pathophysiology of ovarian cancer is the least understood among all major human malignancies because of a poor understanding of the aetiological factors and mechanisms of ovarian cancer progression. There is increasing evidence suggesting that several key reproductive hormones, such as GnRH, gonadotrophins and sex steroids, regulate the growth of normal OSE and ovarian cancer cells. The objective of this review was to highlight the effects of these endocrine factors on ovarian cancer cell growth and to summarize the signalling mechanisms involved in normal human OSE and its neoplastic counterparts.

Prostaglandin-endoperoxide synthase (PTGS1 and PTGS2) expression and prostaglandin production by normal monkey ovarian surface epithelium

OBJECTIVE

To determine whether hCG regulates the expression of prostaglandin (PG) synthesis enzymes and the production of PGs by normal monkey ovarian surface epithelium (OSE).

DESIGN

Experimental animal study.

SETTING

Research laboratory.

ANIMAL(S)

Adult cynomolgus macaques.

INTERVENTION(S)

Monkeys received exogenous gonadotropins to stimulate multiple follicular development. Ovarian surface epithelium cells and whole ovaries were obtained before (0 hours) and 36 hours after an ovulatory dose of hCG.

MAIN OUTCOME MEASURE(S)

Ovarian surface epithelium expression of prostaglandin-endoperoxide synthase 1 (PTGS1) and PTGS2 proteins was determined by immunocytochemistry. Prostaglandin synthesis enzyme messenger RNA (mRNA) levels were determined by RT-PCR. Prostaglandin E2 and PGF2alpha production was assessed by enzyme immunoassays.

RESULT(S)

Ovarian surface epithelium maintained in long-term culture expressed mRNA and protein for PTGS1 and PTGS2 (n = 6); inhibition of PTGS1, but not PTGS2, reduced PGE2 synthesis (n = 3). Prostaglandin-endoperoxide synthase 1 was present in OSE of ovarian tissue sections obtained 0 (n = 4) and 36 (n = 3) hours after hCG; PTGS2 was not detected. Ovarian surface epithelium collected 0 (n = 3) and 36 (n = 4) hours after hCG expressed mRNAs for PTGS1, PTGS2, and three PGE synthases; the ratio of PTGS2 to PTGS1 increased in response to hCG exposure.

CONCLUSION(S)

Monkey OSE expresses mRNA for PTGS1, PTGS2, and all PGE synthases and produces PGE2 both before and 36 hours after hCG. Detection of PTGS1, but not PTGS2, protein in OSE in vivo supports the hypothesis that PTGS1 is the enzyme responsible for PGE2 production by primate OSE in vivo.

Gonadotropin-induced apoptosis in human ovarian surface epithelial cells is associated with cyclooxygenase-2 up-regulation via the beta-catenin/T-cell factor signaling pathway

Gonadotropins play a prominent role in ovarian function and pathology. We have shown that treatment with gonadotropins (FSH and LH/human chorionic gonadotropin) reduces the amount of N-cadherin with a concomitant induction of apoptosis in human ovarian surface epithelial (OSE) cells, but precise molecular mechanisms remain to be elucidated. Here, we demonstrated activation of beta-catenin/T-cell factor (TCF) signaling by gonadotropins. We further showed that ectopic expression of N-cadherin was sufficient to recruit beta-catenin to the plasma membrane, thereby blocking beta-catenin/TCF-mediated transactivation in gonadotropin-treated cells. Transfection with beta-catenin small interfering RNA or expression of dominant negative TCF inhibited apoptosis, whereas expression of dominant stable beta-catenin (S37A) caused significant apoptosis, thus supporting a proapoptotic role for beta-catenin/TCF in human OSE. In addition, we showed that gonadotropins enhanced beta-catenin/TCF transcriptional activity through inactivation of glycogen synthase kinase-3beta in a phosphatidylinositol 3-kinase/Akt-dependent manner, indicating cross talk between the phosphatidylinositol 3-kinase/Akt and beta-catenin signaling pathways through glycogen synthase kinase-3beta. Furthermore, gonadotropins increased cyclooxygenase-2 (COX-2) expression via the beta-catenin/TCF pathway. COX-2 also played a role in gonadotropin-induced apoptosis, as treatment with the COX-2-specific inhibitor NS-398 or COX-2 small interfering RNA blocked gonadotropin-dependent apoptotic activity. These findings suggest that the participation of beta-catenin in adhesion and signaling may represent a novel mechanism through which gonadotropins may regulate the cellular fate of human OSE.

Impact of gonadotrophins and steroid hormones on tumour cells derived from borderline ovarian tumours

BACKGROUND

Conservative surgery is currently proposed for young patients with borderline ovarian tumours (BOT). For those experiencing infertility, the question of medically assisted procreation is raised. We have evaluated in vitro the proliferation of cultured BOT cells in response to FSH or estradiol (E(2)).

METHODS

Primary cell cultures were prepared from BOT. The presence of FSH and E(2) receptors was evaluated by immunochemistry. Cultures in vitro were stimulated with FSH (40 and 200 mUI/ml) or E(2) (300 and 2000 pg/ml) for 96 h and proliferation was evaluated with the WST-1 test.

RESULTS

Four primary cultures were obtained that expressed FSH and E(2) receptors to different extents. Growth was generally similar to controls when treated with either FSH or E(2) although 300 pg/ml E(2) caused a significant inhibitory effect on cell proliferation (P = 0.035).

CONCLUSION

No stimulatory effect of FSH or E(2) on cultured BOT cells was found, despite the presence of receptors. Although preliminary, these results suggest that gonadotrophins and E(2) could be used in patients experiencing infertility after conservative surgery.

Gonadotropins activate proteolysis and increase invasion through protein kinase A and phosphatidylinositol 3-kinase pathways in human epithelial ovarian cancer cells

Despite evidence that gonadotropins may facilitate peritoneal metastasis of ovarian cancer by increasing cell adhesion, the action and molecular mechanism of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in ovarian cancer invasion is not well characterized. In the present study, we investigated the effects of FSH and LH on the invasive activity and the expression of metastasis-related proteinases in human epithelial ovarian cancer by Western blot, zymography, reverse transcription-PCR (RT-PCR), ELISA, and Boyden chamber assay. Treatment with FSH or LH (10, 100, or 1,000 ng/mL) significantly increased the invasion of ovarian cancer cell lines, including BG-1, CaOV-3, and SKOV-3 cells but not OVCAR-3 cells. In addition, treatment of SKOV-3 cells with FSH or LH (100 or 1,000 ng/mL) enhanced the expression and activation of matrix metalloproteinases (MMP-2 and MMP-9) as shown by RT-PCR, gelatin zymography, and ELISA. Pretreatment with [(2R)-2-(hydroxamido-carbonylmethyl)-4-methylpentanoyl]-l-tryptophan methylamide (10 micromol/L), a total MMP inhibitor, and 3-(4-phenoxyphenylsulfonyl)-propylthiirane (20 micromol/L), a specific gelatinase inhibitor, neutralized the proinvasive effect of gonadotropins in SKOV-3 cells. In addition, the secretion of tissue inhibitor of metalloproteinases (TIMP-1 and TIMP-2) and plasminogen activator inhibitor-1 was significantly decreased by FSH and LH (100 or 1,000 ng/mL). We further showed that gonadotropins induced an increase in SKOV-3 invasiveness via the activation of protein kinase A (PKA) and phosphatidylinositol 3-kinase (PI3K) signaling pathways. Taken together, these results suggest that gonadotropins may contribute to ovarian cancer metastasis via activation of proteolysis and increase in invasion through the PKA and PI3K pathways.

Gonadotropins and ovarian carcinogenesis: a new era of basic research and its clinical implications

The possible relationship between gonadotropins and ovarian carcinoma development has received much attention, and in recent years, great progress has been made in basic and epidemiologic research about this issue. Gonadotropins sensitivity in the ovarian surface epithelium (OSE) and in a subset of ovarian carcinomas has been established in vivo and in vitro. Gonadotropins have been shown to induce various biologic actions in the OSE and ovarian carcinoma cells, such as changes in cell proliferation, apoptosis, cell adhesion, and chemosensitivity. These basic studies strongly suggest that gonadotropins are involved in the development and progression of ovarian carcinoma. In contrast, although earlier studies showed a significant risk of infertility therapy for ovarian carcinoma development, subsequent studies reported only slightly increased or no significant increased risk of gonadotropin stimulation and/or assisted reproductive technologies for ovarian carcinoma development. Therefore, the association between ovarian stimulation and ovarian carcinoma remains controversial. Nevertheless, since development of ovarian carcinoma in infertile women during infertility treatment is a serious concern for gynecologists, this review also covers important points for clinical practice, especially the issue of early detection of ovarian carcinoma.

Gonadotropin-induced superovulation drives ovarian surface epithelia proliferation in CD1 mice

The ovarian surface epithelium (OSE) is a monolayer of cells that surround the ovary and accommodate repeated tear and repair in response to ovulation. OSE cells are thought to be the progenitors of 90% of ovarian cancers. Currently, the total amount of proliferation of the OSE has not been reported in response to one ovulatory event. In this study, proliferation of the OSE was quantified in response to superovulation induced by ip injection of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) in immature 27-d-old CD1 mice using bromodeoxyuridine (BrdU). BrdU incorporation into the OSE cells was measured from the time of hCG injection for a total cumulative label of 12 h. BrdU incorporation was also measured from the time of PMSG injection for a total label of 60 h to correlate proliferation with specific gonadotropin stimulation. The OSE proliferation was significantly higher in superovulated animals compared with control mice at all time points. Proliferation was also analyzed in discrete anatomical sections and indicated that OSE covering antral follicles and corpora lutea proliferated more rapidly than OSE distal to follicular growth. Finally, apoptosis was assessed in response to ovulation, and virtually no cell death within the OSE was detected. These data demonstrate that the OSE, especially near antral follicles and corpora lutea, proliferates significantly in response to the gonadotropins PMSG and hCG. Therefore, ovarian surface cell division in response to ovulation could contribute to ovarian cancer by proliferation-induced DNA mutations and transformed cell progression.

Gonadotropins regulate N-cadherin-mediated human ovarian surface epithelial cell survival at both post-translational and transcriptional levels through a cyclic AMP/protein kinase A pathway

Gonadotropins are the major regulators of ovarian function and may be involved in the etiology of ovarian cancer. In this study, we report a new mechanism whereby gonadotropins regulate the survival of human ovarian surface epithelium (OSE), the tissue of origin of epithelial ovarian carcinomas. Our results indicate that disruption of N-cadherin-mediated cell-cell adhesion is an important molecular event in the apoptosis of human OSE. Treatment with surge serum concentrations of gonadotropins reduced the amount of N-cadherin with a concomitant induction of apoptosis, and this effect was mediated by a cAMP/protein kinase A pathway but not the ERK1/2 and protein kinase C cascades. We further demonstrated that activation of the gonadotropins/cAMP signaling pathway in human OSE led to a rapid down-regulation of N-cadherin protein level followed by a reduction at the level of N-cadherin mRNA, indicating that expression of N-cadherin was regulated by post-translational and transcriptional mechanisms. The former mechanism was mediated by increased turnover of N-cadherin protein and could be reversed by inhibition of proteasomal or matrix metalloproteinase (MMP-2) activity. On the other hand, at the transcriptional level, the addition of actinomycin D abolished the cAMP-mediated decrease in N-cadherin mRNA but did not change its stability. Inhibition of protein kinase A or expressing a dominant negative mutant of cAMP-response element-binding protein blocked this decrease of N-cadherin mRNA. Together, the combined operation of post-translational and transcriptional mechanisms suggests that regulation of N-cadherin is a crucial event and emphasizes the important role that N-cadherin has in controlling the survival capability of human OSE.

Endogenous Hormones and Ovarian Cancer: Epidemiology and Current Hypotheses

The effect of major epidemiologic risk factors for ovarian cancer has been reviewed in the light of several hormonal hypotheses, including the gonadotropin, androgens, progesterone, estrogens, insulin-like growth factor-I, and insulin hypotheses. The role of inclusion cyst formation and Mullerian epithelium differentiation in the pathology of the disease are also briefly outlined. Although based on limited data, the observed tendency in current evidence suggests possible etiologic roles for elevated androgens and estrogens and decreased progesterone in the pathogenesis of ovarian cancer. A direct effect of gonadotropins cannot be entirely ruled out, but it is plausible that their effect on ovarian cancer risk is mediated by stimulation of ovarian steroidogenesis. Insulin-like growth factor-I also emerges as a hormone that may be directly involved in the pathogenesis of the disease, but thus far only one prospective study has examined this association. Hyperinsulinemia is an unlikely risk factor for ovarian cancer. The observed tendency for an increased risk with androgens from ovarian origin (in premenopausal women), the lack of association with adrenal androgens, and the relatively weak associations observed with obesity, hormonal replacement therapy use, and endogenous hormones after menopause suggest that ovarian synthesis of sex steroids rather than their circulating levels may be etiologically important. More data from prospective studies will be crucial to improve our understanding of the etiologic role of endogenous hormones in the pathogenesis of ovarian cancer. Such data will ultimately provide opportunities for research targeted; at early detection and preventive interventions.

Gonadotropin (LH, FSH) levels in serum and cyst fluid in epithelial tumors of the ovary

OBJECTIVES

The aim of this work was to determine gonadotropin (LH, FSH) levels in serum and cyst fluid in various type of ovarian epithelial neoplasms (benign, borderline, malignant) and to compare them with levels in benign cysts. Additionally we decided to estimate if there were some significant correlations between serum and ovarian cyst fluid in gonadotropin levels in all investigated groups.

MATERIALS AND METHODS

The study group included 74 patients before (n=36) and after (n=38) menopause, divided into four groups depending on the histopathologic diagnosis. Serum and cyst fluid levels of LH and FSH were determined in all patients.

RESULTS

We found statistically significant differences concerning LH and FSH levels in serum and cyst fluid between malignant and borderline tumors, between malignant tumors and benign cystadenomas and between malignant tumors and non-neoplastic cysts. We also found statistically significant correlations between serum and cyst fluid as to FSH and LH levels in patients with borderline tumors. There were no statistically significant correlations between serum and cyst fluid as to FSH and LH levels in patients with malignant epithelial tumors (group 1) and in patients with benign cystadenomas (group 3).

CONCLUSIONS

High FSH and LH levels in cyst fluid of malignant epithelial tumors of the ovary are in line with the gonadotropin theory of tumor growth. Simultaneous determination of various types inhibin levels appears to be an interesting topic for our future research.

Formation and Barrier Function of Tight Junctions in Human Ovarian Surface Epithelium1

The normal ovarian surface epithelium (OSE) is a primitive epithelium made up by a single layer of mesothelial-type epithelial cells. When these cells get trapped in the ovarian stroma, expression of epithelial specific markers, such as E-cadherin, are induced. Most epithelial cells are also characterized by the ability to form tight junctions (TJ). Incomplete TJ have earlier been demonstrated in the OSE by electron microscopy studies. We have investigated expression and localization of the TJ proteins ZO-1, occludin, and claudin-1 in tissue biopsies from normal human ovaries and OSE in culture. The dynamics of TJ formation were studied in human OSE cultured on porous filters in culture inserts by measuring trans epithelial resistance (TER) including Ca(2+) switch experiments. Confluent OSE cells were also analyzed by electron microscopy. The results show that normal human OSE has expression of all three TJ proteins investigated. These proteins, ZO-1, occludin, and claudin-1, were localized to OSE cell borders both in ovarian biopsies and in cultured OSE. There was no difference in this regard between fertile and postmenopausal women. Cells in culture were polarized and presented junctional complexes seen by electron microscopy. In the Ca(2+) switch experiments, removing free Ca(2+) transiently, TER decreased significantly (P < 0.05) in the Ca(2+)-free group compared with nontreated OSE. TER was fully restored after 24 h. N-cadherin but not E-cadherin was expressed in the OSE and localized to the cell borders. We conclude that normal human OSE express and form functional TJ both in vivo and vitro. This report also describes a method to study the influence of ovarian-derived mediators on TJ in cultured OSE.

Cytology of human ovarian surface epithelial brushings

BACKGROUND

The human ovarian surface epithelium (HOSE) is the putative source of ovarian epithelial cancer, the most lethal gynecologic malignancy that affects women in the United States. The current study was designed to provide a database of normal HOSE cell features for diagnostic and research applications.

METHODS

HOSE was harvested from 42 women undergoing laparoscopy or laparotomy for benign gynecologic disorders, infertility problems, or pregnancy. Of the 42 women, 12 were postovulatory and 20 were receiving hormonal regimens. Cells were harvested with a sterile brush inserted through a laparoscopic port or with a sterile cell scraper at laparotomy.

RESULTS

Two HOSE populations were identified, ranging in size from 8 to 10 microm and from 15 to 20 microm, respectively. The cells measuring 15-20 microm exhibited slight anisonucleosis, more prominent nucleoli, fine cytoplasmic metachromasia, and an overall reparative or squamoid morphology. Cells were single or arranged in small clusters, sheets, or papillae. They coexpressed cytokeratin and vimentin but did not overexpress p53. Cellularity and proliferation (up to 3.2% +/- 0.8) were higher and papillae more frequent in postovulatory and cyst-bearing ovaries, including polycystic ovaries, suggesting underlying ovarian or hormonal influences. Representative HOSE brushings yielded a mean of 23,133 cells per patient (range, 4250-64,500 cells), equivalent to an estimated 0.58, 0.46, and 0.14 microg of nuclear protein, cell RNA, and nuclear DNA, respectively. Within 7-10 days of explantation, HOSE cells formed confluent monolayers with immunohistochemical and ultrastructural epithelial features.

CONCLUSIONS

The current study defined baseline features of HOSE cells important to pathologists and clinicians evaluating women at risk for ovarian epithelial cancer and to researchers investigating the pathobiology of this aggressive gynecologic malignancy.

Loss of surface and cyst epithelial basement membranes and preneoplastic morphologic changes in prophylactic oophorectomies

BACKGROUND

The authors suggested that the loss of collagen IV and laminin-containing basement membrane and the loss of Disabled-2 (Dab2) expression were two critical events associated with morphologic dysplastic changes of the ovarian surface epithelium as a step in tumorigenicity. Both the basement membrane and Dab2, a candidate tumor suppressor of ovarian carcinoma, were involved in epithelial cell surface positioning and organization. The authors speculated that the purging of the basement membrane may be similar to the proteolysis during gonadotropin-stimulated ovulation, a cyclooxygenase 2 (Cox-2)-mediated process.

METHODS

Prophylactic oophorectomy is used to prevent breast and ovarian carcinoma in high-risk populations. These ovarian tissue specimens often contain an increased presence of morphologically abnormal lesions that are believed to be preneoplastic. The authors evaluated archived prophylactic oophorectomy specimens to verify whether the loss of Dab2 expression and the removal of the basement membrane that occur at the ovarian surface and inclusion cyst epithelia are molecular markers of preneoplastic lesions. Of the 36 samples containing identifiable ovarian surface epithelial components on slides, immunostaining was employed to evaluate the intactness of the basement membrane (periodic acid-Schiff [PAS], collagen IV, and laminin) and the expression of Dab2 and Cox-2. Expression of Cox-1 and Cox-2 also were evaluated in cultured ovarian surface epithelial cells prepared from ovarian tissue specimens removed from patients who underwent prophylactic surgery.

RESULTS

The morphologically normal ovarian surface epithelium typically contained a collagen IV- and laminin-positive basement membrane, which also was detected by PAS staining. Many morphologically altered areas, such as papillomatosis, invaginations, inclusion cysts, stratification, adenomas, and microscopic adenocarcinomas, were found in these specimens. Both the morphologically altered and adjacent morphologically normal epithelia consistently exhibited loss of basement membrane and/or Dab2 expression and an increase in Cox-2 staining. Frequently, an increase in Cox-2 staining was correlated with the loss of epithelial basement membrane in morphologically normal areas.

CONCLUSIONS

The loss of Dab2 and basement membrane and the overexpression of Cox-2 were observed in presumptive neoplastic precursor areas of oophorectomy specimens obtained from a population at high risk for ovarian carcinoma. Transient loss of collagen IV and laminin in the basement membrane of the preneoplastic epithelium and the loss of Dab2 expression are common early events associated with morphologic alteration and tumorigenicity of the ovarian surface epithelium. The authors concluded that Cox-2 overexpression may play a role in the purging of basement membrane of the ovarian surface epithelium, mimicking the process of ovulation. Further experiments may be able to test the hypothetical model derived from these histologic observations.

Cell-cell adhesion in the normal ovary and ovarian tumors of epithelial origin; an exception to the rule

Cells are held together either by direct cell-cell contact or adhesion to extra-cellular matrix. Cell-cell adhesion in epithelial cell sheets consists of junctions, i.e. tight-, adherens- and gap-junctions. The adherens junctions, which are build up by the cadherin/catenin complex, are the main topic of this review, especially the aspect of its role in ovarian tumor biology. The ovarian surface epithelium is the origin for approximately 90% of the malignant ovarian tumors. The tumors arise from the inclusion cysts, localized in the ovarian stroma and grow solid, cystic or in mixed formations. Intra-abdominal spread of the ovarian cancer is common and this is a process that theoretically could be closely connected with impaired cell-cell adhesion. However, as we stand today, descriptive and functional studies on the cadherin-catenin complex and its cell signaling role in ovarian tumorigenesis reveals data that suggests a conversion of the mesothelial-like cells of the ovarian surface to a more epithelial phenotype with normal cell-cell adhesion prior to tumor differentiation. In later stages, invasive ovarian tumors still strongly express several cadherins, which are contrary to many other tumors, i.e. prostate and thyroid adenocarcinomas.

Three-dimensional microanatomical dynamics of the ovary in postreproductive aged women

OBJECTIVE

To evaluate the microanatomical dynamics of the ovary during postreproductive life.

DESIGN

Retrospective, observational research study.

SETTING

Institutional (university).

PATIENT(S)

Eleven (43- to 72-year-old) women in perimenopause, menopause, or postmenopause.

INTERVENTION(S)

Biopsies of ovaries obtained from patients undergoing gynecologic surgery or diagnostic procedures.

MAIN OUTCOME MEASURE(S)

Analysis of the 3-dimensional microanatomy of the ovary by transmission and high-resolution scanning electron microscopy.

RESULT(S)

The surface epithelium gets gradually flatter and is always present, even in advanced age. The surface appears smoother because of a smaller number of papillae and crypts as well as a decreased number and shortening of microvilli on surface epithelial cells. Signs of atrophy and fibrosis are evident. Primordial follicles are usually absent in postmenopause, whereas corpora atretica, hemorrhagica, and albicantia, scar tissue, and simple follicular cysts are common after menopause. Apoptotic and necrotic cells appear frequently within the surface epithelium. Major common features are a marked reduction in number and caliber of blood vessels with thickening of the vascular walls and changes in endothelial cells.

CONCLUSION(S)

Scanning electron microscopy studies are a useful complement to ordinary gynecologic diagnostic methods. Variations among patients of the same age range or functional status should be considered.

Premature ovarian failure (POF): discordance between somatic and reproductive aging

Premature ovarian failure (POF) is a unique example of isolated organ senescence, with a population prevalence of approximately 1%. Though the phenotypic expression of POF is similar to that of age-appropriate natural menopause, the underlying pathophysiological mechanisms are diverse and not entirely clear. The impact of POF on the patient is profound, with myriad ramifications, ranging from psychological devastation to multi-system implications of estrogen deprivation and its sequelae. The hastening of degenerative changes noted in these patients however, are not entirely ameliorated with estrogen replacement and POF may indeed represent an acceleration of the aging process.

Proliferation of rhesus ovarian surface epithelial cells in culture: lack of mitogenic response to steroid or gonadotropic hormones

Ovarian cancer is the most lethal gynecological cancer, and approximately 90% of ovarian cancers derive from the ovarian surface epithelium (OSE), yet the biology of the OSE is poorly understood. Factors associated with increased risk of non-hereditary ovarian cancer include the formation of inclusion cysts, effects of reproductive hormones and the number of ovulations experienced in a woman's lifetime. Distinguishing between these factors is difficult in vivo, but cultured OSE cells are viable tools for some avenues of research. Here we establish rhesus macaque OSE cultures and demonstrate that these cells express cytokeratin, vimentin, N-cadherin, ER-alpha, and PR but are negative for E-cadherin. We show that these cells activate MAPK and proliferate in response to extracellular calcium, as do human and rat OSE. In contrast, the gonadotropic hormones FSH (4-400 IU/liter), LH (8.5-850 IU/liter), and human CG (10-1000 IU/liter) fail to stimulate proliferation. We find that concentrations of progesterone and estrogen normally present in follicles just before ovulation ( approximately 1000 ng/ml) significantly decrease the number of mitotically active rhesus macaque OSE cells as determined by PCNA labeling, total cell count, and (3)H-thymidine uptake, whereas lower steroid concentrations have no effect.

Production of steroids by human ovarian surface epithelial cells in culture: possible role of progesterone as growth inhibitor

OBJECTIVE

The purpose was to investigate whether normal ovarian surface epithelial cells, harvested from premenopausal and postmenopausal women, are capable of steroid production, and to evaluate effects of estradiol and progesterone on growth regulation of such cells.

METHODS

Ovarian surface epithelial cells were obtained by brushing of the ovarian surface of 9 premenopausal and 10 postmenopausal women undergoing surgery for benign gynecological diseases. The conditioned media after culture, with and without addition of FSH and LH, were analyzed for estradiol and progesterone. The proliferative effects of the steroids were analyzed using two different culture models, nonconfluent cells and confluent cells, and two different detection methods, [(3)H]thymidine incorporation and a colorimetric method assaying cell number.

RESULTS

The normal ovarian surface epithelial cells were found to secrete both estradiol and progesterone, a production that was not regulated by FSH or LH. Addition of steroids to the cultured cells did not induce any overall significant growth effects. However, progesterone significantly inhibited the growth of ovarian surface epithelial cells from three of the patients. Enhanced thymidine incorporation was observed in the presence of the progesterone receptor antagonist Org 31710 in the nonconfluent cultures of cells from postmenopausal women, but no effect of an estrogen receptor antagonist was observed.

CONCLUSIONS

The normal ovarian surface epithelium is capable of steroid production, which is also often observed in tissue from ovarian epithelial tumors. Progesterone appeared to be a negative regulator of ovarian surface epithelial growth, while estradiol had no effect.