Ovarian surface epithelium: biology, endocrinology, and pathology

Cyclic changes of the ovarian surface epithelium in the rat

The ovarian surface epithelium (OSE) plays pivotal roles during ovulation and postovulatory wound repair. In this paper we describe the proliferative activity of the OSE through the estrous cycle in adult cycling rats, by immunohistochemical detection of DNA-incorporated bromodeoxyuridine (BrdU). Immunohistochemical detection of estrogen receptor α (ERα) and progesterone receptor was also performed. The cycle of the OSE consists of a proliferative phase (that lasts for two consecutive estrous cycles) and a quiescent phase of variable duration. Cyclic changes in the OSE were related to the underlying ovarian structure. OSE areas covering growing follicles entered into the proliferative phase during the transition from proestrus to estrus, with the appearance of fast-growing class 1 follicles, destined to ovulate at the end of the current estrous cycle. A labeling index (after pulse-labeling BrdU treatment) of about 7% was maintained throughout the estrous cycle in parallel to follicle growth. Cumulative BrdU-labeling (after daily BrdU treatment) indicated that about 1/3 of the total OSE cell proliferation was related to follicle growth. Following ovulation, OSE cells covering newly-formed corpora lutea showed a labeling index of about 50% that decreased through metestrus and diestrus (about 13% and 3%, respectively), returning to basal levels by proestrus. Cumulative BrdU-labeling indicated that about 2/3 of the total proliferative activity was related to ovulation repair/luteinization. The remaining OSE covering ovarian stroma or structurally regressing corpora lutea of previous cycles showed negligible BrdU labeling. The equivalent proliferative activity found in the OSE covering newly-formed corpora lutea in indomethacin-treated rats lacking rupture of the OSE at the apex, demonstrated that ovulation-triggered proliferation was not dependent on the loss of integrity of the OSE at the ovulation site. OSE cells expressed ERα throughout the cycle, but no differential expression was found between proliferating and quiescent OSE areas. On the contrary, OSE cells did not express PR at any time of the cycle. These data indicate the existence of a cycle of the OSE, related to the cyclic changes in the underlying ovarian structure and strongly suggest that the proliferative activity of the OSE is regulated by local microenvironmental rather than by systemic factors.

Ovarian tumor expression of an oviductal protein in the hen: a model for human serous ovarian adenocarcinoma

OBJECTIVE

We hypothesized that ovarian tumors without oviductal involvement would not express the oviductal protein ovalbumin, the major protein found in the magnum of the hen's oviduct.

METHODS

On the basis of gross visual examination, tissues samples were removed from hens determined to have ovarian tumors and were processed, embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin. Ovarian tumors and other peritoneal lesions were evaluated histologically. Paraffin sections of ovarian and oviductal tissue were deparaffinized and evaluated for the protein expression of ovalbumin, proliferating cell nuclear antigen (PCNA), and progesterone receptor (PR).

RESULTS

Hens with ovarian adenocarcinoma without (n = 10) or with (n = 6) oviductal involvement were positive for ovalbumin in the ovary. Ovary sections from normal hens (n = 9) were negative, and oviductal sections from normal hens (n = 3) were positive for ovalbumin. Expression of PCNA protein was abundant in all ovarian tumors (16 of 16). Oviductal epithelial cells strongly expressed PCNA protein. Expression of PR was observed in 9 of 14 ovarian tumors.

CONCLUSION

The presence of ovalbumin in ovarian tumors in the absence of any oviductal involvement suggests that ovarian tumors dedifferentiate during the disease process and thereby resemble serous-type ovarian tumors in women.

Aromatase expression in ovarian epithelial cancers

Our study focused on aromatase cytochrome P450 (CYP19) expression in ovarian epithelial normal and cancer cells and tissues. Aromatase mRNA expression was analyzed by real-time PCR in ovarian epithelial cancer cell lines, in human ovarian surface epithelial (HOSE) cell primary cultures, and in ovarian tissue specimens (n=94), including normal ovaries, ovarian cysts and cancers. Aromatase mRNA was found to be expressed in HOSE cells, in BG1, PEO4 and PEO14, but not in SKOV3 and NIH:OVCAR-3 ovarian cancer cell lines. Correlation analysis of aromatase expression was performed according to clinical, histological and biological parameters. Aromatase expression in ovarian tissue specimens was higher in normal ovaries and cysts than in cancers (P<0.0001). Using laser capture microdissection in normal postmenopausal ovaries, aromatase was found to be predominantly expressed in epithelial cells as compared to stromal component. Using immunohistochemistry (IHC), aromatase was also detected in the epithelium component. There was an inverse correlation between aromatase and ERalpha expression in ovarian tissues (P<0.001, r=-0.34). In the cancer group, no significant differences in aromatase expression were observed according to tumor histotype, grade, stage and survival. Aromatase activity was evaluated in ovarian epithelial cancer (OEC) cell lines by the tritiated water assay and the effects of third-generation aromatase inhibitors (AIs) on aromatase activity and growth were studied. Letrozole and exemestane were able to completely inhibit aromatase activity in BG1 and PEO14 cell lines. Interestingly, both AI showed an antiproliferative effect on the estrogen responsive BG1 cell line co-expressing aromatase and ERalpha. Aromatase expression was found in ovarian epithelial normal tissues and in some ovarian epithelial cancer cells and tissues. This finding raises the possibility that some tumors may respond to estrogen and provides a basis for ascertaining an antimitogenic effect of AI in a subgroup of ovarian epithelial cancers.

Characterization of a Carcinogenesis Rat Model of Ovarian Preneoplasia and Neoplasia

Animal models of ovarian cancer are crucial for understanding the pathogenesis of the disease and for testing new treatment strategies. A model of ovarian carcinogenesis in the rat was modified and improved to yield ovarian preneoplastic and neoplastic lesions that pathogenetically resemble human ovarian cancer. A significantly lower dose (2 to 5 mug per ovary) of 7,12-dimethylbenz(a)anthracene (DMBA) was applied to the one ovary to maximally preserve its structural integrity. DMBA-induced mutagenesis was additionally combined with repetitive gonadotropin hormone stimulation to induce multiple cycles of active proliferation of the ovarian surface epithelium. Animals were treated in three arms of different doses of DMBA alone or followed by hormone administration. Comparison of the DMBA-treated ovaries with the contralateral control organs revealed the presence of epithelial cell origin lesions at morphologically distinct stages of preneoplasia and neoplasia. Their histopathology and path of dissemination to other organs are very similar to human ovarian cancer. Hormone cotreatment led to an increased lesion severity, indicating that gonadotropins may promote ovarian cancer progression. Point mutations in the Tp53 and Ki-Ras genes were detected that are also characteristic of human ovarian carcinomas. Additionally, an overexpression of estrogen and progesterone receptors was observed in preneoplastic and early neoplastic lesions, suggesting a role of these receptors in ovarian cancer development. These data indicate that this DMBA animal model gives rise to ovarian lesions that closely resemble human ovarian cancer and it is adequate for additional studies on the mechanisms of the disease and its clinical management.

Anti-inflammatory and proliferative responses in human and ovine ovarian surface epithelial cells

The majority of ovarian cancers (>90%) are believed to derive from the ovarian surface epithelium (OSE); a single layer covering the entire surface of the ovary. At ovulation, the OSE cell layer undergoes an inflammatory response, involving cell death and growth, in order to overcome ovarian surface rupture. Abnormalities during these processes are believed to contribute to the development of tumours. Using primary cultures of OSE cells, we have compared anti-inflammatory and proliferative responses directly between human and ovine OSE cells to further establish the use of ovine OSE cells as a suitable model system for the study of human OSE cells. In order to compare effects of inflammatory stimulation, expression and activity of 11βhydroxysteroid dehydrogenase (11βHSD) type 1 was measured in OSE cells in response to interleukin (IL)-1α. As previously identified in human OSE cells, treatment of ovine OSE cells with IL-1α stimulated a concomitant increase of 11βHSD type 1 mRNA (31-fold;P< 0.05) and oxoreductase activity, indicating an increased production of anti-inflammatory cortisol. To compare the growth of human and ovine OSE cells, OSE cell number was measured in response to treatment with gonadotropins or growth factors. In the presence of FSH, LH or human chorionic gonadotropin (hCG), ovine and human OSE cell growth was similarly stimulated >1.2-fold (P< 0.05). In the presence of connective tissue growth factor (CTGF) and more significantly insulin growth factor I (IGF-I), human and ovine OSE cell growth was also similarly stimulated >1.2-fold (P< 0.05) and >1.5-fold (P< 0.01), respectively. The induction of both human and ovine OSE cell growth by IGF-I or hCG was further shown to be dependent on activation of the MAP kinase/extracellular-signal-regulated kinase (ERK) pathway. Stimulation of ovine OSE cell growth by hepatocyte growth factor (HGF) was similarly shown to be ERK-dependent; however, for human OSE cells, HGF only mildly stimulated ERK phosphorylation and failed to stimulate OSE cell growth. The demonstration that human and ovine OSE cells share similarities at the level of cell signalling, gene expression and cellular growth supports the use of ovine OSE cells as a suitable model for the study of human OSE cells.

Expression of candidate tumor markers in ovarian carcinoma and benign ovary: evidence for a link between epithelial phenotype and neoplasia

EpCAM, epithelial membrane antigen (EMA)-mucin 1 (MUC1), mesothelin, and CD9 have been reported to be overexpressed at the RNA level in ovarian carcinomas. By using immunohistochemistry, we profiled the protein expression of these gene products in ovarian carcinoma tissues and compared them with benign ovarian surface epithelium (OSE) and cortical inclusion cysts (CICs). Immunoreactivity for EMA and calretinin were used to define epithelial and mesothelial differentiation in nontumor tissues, respectively. Papillary serous (n = 16) and endometrioid (n = 10) tumors were immunopositive for EMA/MUC1 (100%), mesothelin (75% and 30%, respectively), CD9 (88% and 90%, respectively), and EpCAM (100%). All ovarian carcinomas and carcinoma cell lines tested were negative for calretinin. In nonneoplastic ovary, both OSE and CICs ranged from flat-to-cuboidal to stratified and ciliated in appearance. OSE with a cuboidal morphology had a similar immunoreactivity as omental peritoneum, expressing calretinin, mesothelin, and CD9. In contrast, CICs with stratified and ciliated epithelium show expression patterns similar to those in fallopian tubes. They frequently expressed EMA, EpCAM, mesothelin, and CD9. This immunophenotype is preserved in ovarian carcinomas, suggesting that Müllerian metaplasia signals the acquisition of these markers and that their expression is maintained in ovarian carcinomas that originate from this epithelium.

Estrogens and epithelial ovarian cancer

OBJECTIVE

Molecular mechanisms involved in ovarian carcinogenesis are still unclear, but there is growing evidence that estrogens promote tumor progression in an epithelial ovarian cancer (EOC) subgroup.

METHODS

We reviewed current knowledge on the effects of estrogens in ovarian carcinogenesis and new potential research focuses concerning hormonal therapy of EOC.

RESULTS

Experimentally, estrogen stimulates the growth of ovarian tumor cell lines expressing estrogen receptors (ER). We and other authors have demonstrated differential expression of ERalpha or beta during ovarian carcinogenesis, with overexpression of ERalpha as compared to ERbeta in cancer. This differential expression in ER suggests that estrogen-induced proteins may act as ovarian tumor-promoting agents. Among these proteins, c-myc, fibulin-1, cathepsin-D, or several kallikreins may play a role, since high expression levels have been found in EOC. Consistently, recent prospective epidemiological studies have indicated that estrogen replacement therapy in postmenopausal women may increase ovarian cancer incidence and mortality.

CONCLUSION

Questions on the estrogen-sensitivity and potential benefits of new hormone therapies in an EOC subgroup should be readdressed in the light of recent experimental and clinical data.

Cultures of ovarian surface epithelium from women with and without a hereditary predisposition to develop female adnexal carcinoma

AIM

Conflicting evidence exists on whether in vivo morphological characteristics can distinguish Ovarian Surface Epithelium (OSE) of ovaries obtained from women with and without a predisposition to develop female adnexal (ovarian and fallopian tube) carcinoma. This study aims to detect differences in growth potential and morphology that are maintained or specifically expressed in vitro.

STUDY DESIGN

Ovarian surfaces were scraped to retrieve OSE cells from 56 women at hereditary high risk for female adnexal carcinoma, of whom 33 are BRCA1 and four are BRCA2 mutation carriers (Predisposed OSE, POSE) and from 26 women without such risk (Non Predisposed OSE, NPOSE). Number of passages and total cell yield until last passage, as well as morphology was compared between both groups. To confirm morphology, the expression of epithelial, mesothelial, and fibroblast markers was assessed.

RESULTS

Both POSE and NPOSE cultures displayed similar growth potential and morphology. The expression of epithelial markers cyto-keratins 7 and 8 was similar between both groups. Only in cultures in which cells did not uniformly exhibit these markers, the percentage of cells expressing these markers was significantly lower at last passage when compared to the initial culture. In these latter cultures, cells that were morphologically indistinguishable from fibroblasts were observed. Mesothelial marker calretinin was expressed in 75% of cells of both POSE and NPOSE cultures and correlates with cyto-keratins 7 and 8 expression. CA 125 expression was equally low in POSE and NPOSE cultures (4.3%). Fibroblast markers FSM and vimentin were expressed in 100% and collagen IV was expressed in 16% of cells in all cultures.

CONCLUSION

OSE cells derived from women with a hereditary predisposition to develop female adnexal cancer possess similar in vitro characteristics as OSE from women without this predisposition. On basis of our results, it seems advisable to study only 100% cyto-keratins 7 and 8 positive OSE cultures, since contamination of fibroblasts in some primary OSE cultures cannot be ruled out.

Differential expression of interleukins IL-13 and IL-15 in normal ovarian tissue and ovarian carcinomas

OBJECTIVE

To determine the temporal and spatial expression of interleukins (IL)-13 and IL-15 in ovarian carcinoma compared to normal ovarian tissue.

METHODS

Quantitative RT-PCR, ELISA and immunohistochemistry.

RESULTS

Q-RT-PCR, ELISA and immunohistochemical analysis indicates that IL-13 and IL-15 mRNA and protein are expressed in normal ovary at various phases of the menstrual cycle with immunoreactive proteins detected in granulosa/theca and luteal cells and to a lesser extent in stromal cells and surface epithelial cells. Compared to normal ovary, ovarian carcinoma expresses elevated levels of IL-13 and IL-15 mRNA, with higher IL-13 expression in primary vs. metastatic tumors. IL-13 and IL-15 protein expression was also higher in the tumor tissues compared to ascites. In normal ovary, ovarian tumors and ascites, the ratio of IL-13/IL-15 favored IL-13. Immunoreactive IL-13 and IL-15 proteins were localized primarily in the tumor cells and infiltrated inflammatory cells with increased intensity with disease stage.

CONCLUSION

Normal ovary and ovarian tumors express IL-13 and IL-15 and pattern of their expression in carcinomas suggests that these cytokines may function in various ovarian cellular activities including inflammatory/immune responses that are integrated cellular events taking place in normal ovary and ovarian tumors.

Tumor necrosis factor-alpha-induced matrix proteolytic enzyme production and basement membrane remodeling by human ovarian surface epithelial cells: molecular basis linking ovulation and cancer risk

The majority of cancer is of surface/cyst epithelial origin. The ovarian surface epithelial cells are organized by a sheet of basement membrane composed mainly of collagen IV and laminin, and it is believed that the basement membrane greatly influences the physiological properties of ovarian surface epithelial cells. Previous studies in our laboratories indicated that loss of the basement membrane, an obligated step in ovulation, is also a critical step during the morphological transformation and tumor initiation of the ovarian surface epithelium. It is speculated that the loss of basement membrane in ovarian surface epithelial transformation may have similar biological mechanism to the loss of surface epithelial basement membrane in ovulation. However, the mechanisms involved in the ovarian surface epithelial basement membrane removal during ovulation are still not completely understood. In the current study, cultured human ovarian surface epithelial (HOSE) cells were examined for their abilities to produce matrix hydrolyzing enzymes and degrade basement membrane in response to a number of potential local mediators in ovulation. Among the candidate-stimulating factors tested, tumor necrosis factor (TNF)-alpha and IL-1beta (to a lesser extent) were found to drastically increase urokinase type plasminogen activator (uPA) and matrix metalloproteinase (MMP)-9 activities secreted from HOSE cells. MMP-2, the other major HOSE cell-secreted gelatinase, is constitutively produced but not regulated. As demonstrated by immunofluorescence staining and Western blot analysis, TNF-alpha treatment caused the degradation and structural reorganization of collagen IV and laminin secreted and deposited by HOSE cells in culture. Amiloride, an uPA inhibitor, not only inhibited the activity of uPA but was also able to suppress TNF-alpha-stimulated MMP-9 activity and prevented the TNF-alpha-stimulated remodeling of the basement membrane extracellular matrix, suggesting the contribution of uPA-mediated proteolytic cascade in this process. This study implicates the potential roles of TNF-alpha, uPA, and MMP-9 in ovarian surface epithelial basement membrane degradation and remodeling, which are processes during ovulation and may contribute to epithelial transformation. The findings may underscore the importance of TNF-alpha, uPA, and MMP-9 in ovarian surface epithelial basement membrane remodeling and may provide a molecular mechanism linking ovulation and ovarian cancer risk.

Pathophysiological Dynamics of Human Ovarian Surface Epithelial Cells in Epithelial Ovarian Carcinogenesis

Epithelial ovarian cancer is responsible for almost half of all the deaths from female genital tract tumors. Major impediments to the clinical treatment of this disease are the relatively asymptomatic progression and a lack of knowledge regarding defined precursor or malignant lesions. Most epithelial ovarian cancers are thought to arise from the transformation of ovarian surface epithelial cells, a single continuous layer of flat-to-cuboidal mesothelial cells surrounding the ovary. To improve our understanding of the pathogenesis of epithelial ovarian cancer, it is necessary to study the biological characteristics of normal ovarian surface epithelial cells. However, this approach has been hampered by the inability to purify and culture such human cells. During the past decade, procedures to isolate and culture human ovarian surface epithelial cells have been developed, and, subsequently, using viral oncogenes, several immortalized cells have been established. This new experimental system is being employed to improve our understanding of the genetic changes leading to the initiation of epithelial ovarian cancer and to identify events in the cancer's development. This review mainly describes the biological dynamics of ovarian surface epithelial cells in the pathogenesis of epithelial ovarian cancer, focusing on humans and excluding small animal models.

Ovarian cancer after in vitro fertilization

There is serious concern about cancer risk in women undergoing ovarian stimulation treatment for infertility and long-term safety of these procedures. Association between fertility drugs and ovarian cancer is still controversial. A 30-year-old woman was referred to our institution with the initial diagnosis of an adnexal tumor after in vitro fertilization. Her history revealed adnexectomy for mucinous cystadenofibroma of the left ovary eight years ago, and cystectomy due to cystadenoma of the right ovary three years ago. At admission, the most remarkable findings were high temperature and elevated white blood cell count and erythrocyte sedimentation rate. Broad spectrum antibiotic treatment was initiated. Six days after admission, the patient was feverish, with temperature up to 38?C, and evident signs of the acute abdomen. Immediate laparotomy was performed and multilocular right adnexal tumor 150x130x100 millimeters in size was identified. The right salpingo-oophorectomy was carried out. Pathological diagnosis was mucinous ovarian adenocarcinoma. Eighteen days later, radical surgery was performed. After the surgery, chemotherapy was applied. There is an urgent need for clear interpretation of the association between fertility drugs and subsequent higher ovarian cancer risk. Lacking conclusive evidence, an increased risk of ovarian cancer has been reported and more recently disputed. Higher ovarian cancer risk may be serious and even life-threatening complication for women undergoing ovarian stimulation.

Roles of luteinizing hormone/chorionic gonadotropin receptor in anchorage-dependent and -independent growth in human ovarian surface epithelial cell lines

Epithelial ovarian carcinomas are thought to arise from cells of ovarian surface epithelium (OSE) covering the free surface of the human ovary. Two immortalized human cell lines, OSE2a (non-tumorigenic) and OSE2b-2 (tumorigenic), were previously established from normal OSE cells of a reproductive-age patient. In the present study, we found that expression of luteinizing hormone (LH)/chorionic gonadotropin (CG) receptor (LH/CGR) is present in OSE2a cells and absent in OSE2b-2 cells. In OSE2a cells, a low concentration (10(3) mIU/ml) of CG enhanced anchorage-dependent growth via up-regulation of insulin-like growth factor-1 (IGF1), whereas a high concentration (10(5) mIU/ml) of CG induced anchorage-independent growth and down-regulation of IGF1 expression. To investigate involvement of other genes in LH/CGR-related tumorigenicity, we compared cDNA expression arrays of OSE2a and OSE2b-2 cells, and found that the following genes had lower expression in OSE2b-2 than in OSE2a: integrin beta 1, intercellular adhesion molecule-1 (ICAM1), and Waf1/Cip1. Subsequent semiquantitative reverse transcription polymerase chain reaction using OSE2a cells showed that expression of integrin beta 1 was down-regulated by a high concentration (10(5) mIU/ml) of CG. These results suggest that LH/CGR affects anchorage-dependent and -independent growth by mediating up- and down-regulation of IGF1 and integrin beta 1. Repetitive and excessive activation of LH/CGR may cause genetic alteration of its signal transduction pathway, resulting in stimulation of growth of OSE cells, initiation of ovarian carcinogenesis, and cancer progression.

Ovarian cancer and high-risk women—implications for prevention, screening, and early detection

OBJECTIVE

The aim of this study was to understand the strengths and limitations of current prevention, detection, and screening methods for ovarian cancer and to identify research areas to improve prevention, screening, and detection of the disease for all women as well as for women carrying a mutation in the BRCA1/2 genes.

METHODS

We convened an ovarian cancer symposium at the University of Pittsburgh in May 2002. Nineteen leading scientists representing disciplines such as epidemiology, molecular biology, pathology, genetics, bioinformatics, and psychology presented the latest data on ovarian cancer prevention, screening, and early detection.

RESULTS

Ovarian cancer is the most common cause of death from a gynecologic malignancy in the United States. Because survival depends on stage of diagnosis, early detection is critical in improving clinical outcome. However, existing screening techniques (CA125, transvaginal ultrasound) have not been shown to reduce morbidity or mortality. Moreover, with the exception of oral contraceptives, there are no available chemopreventive agents. Bilateral salpingo-oophorectomy also has been shown to reduce incidence, but this procedure has several drawbacks in terms of a woman's reproductive, cardiovascular, skeletal, and mental health.

CONCLUSIONS

Better methods to prevent, detect, and screen for ovarian cancer in all women, but particularly in high-risk women carrying mutations in BRCA1/2, are urgently needed. This article reviews the current state of knowledge in the etiology, prevention, and early detection of ovarian cancer and suggests several areas for future clinical, epidemiologic, and laboratory-based research.

Ovarian cancer cell proliferation and motility is induced by engagement of integrin alpha(v)beta3/Vitronectin interaction

During tumor metastasis, a fine-tuned balance between the formation and loosening of adhesive cell contacts has to occur, a process based on the regulated expression of integrins. Human ovarian OV-MZ-6 cancer cells express the integrin alpha(v)beta3, which associates with vitronectin (VN) and correlates with ovarian cancer progression. Adhesion and spreading of OV-MZ-6 cells on VN was accompanied by the formation of focal adhesion contacts and the recruitment of activated tyrosine-phosphorylated focal adhesion kinase. Cultivation of OV-MZ-6 cells on VN resulted in a significantly induced cell proliferation. This VN effect could be mimicked by cultivating cells on the immobilized alpha(v)beta3 directed peptide cyclo-Arg-Gly-Asp-D-Phe-Val (cRGDfV). VN-dependent OV-MZ-6 cell adhesion and proliferation was significantly enhanced by overexpression of alpha(v)beta3 and was accompanied by rapid and transient tyrosine-phosphorylation of p44(erk-1)/p42(erk-2) mitogen-activated protein kinase. Moreover, overexpression of alpha(v)beta3 and OV-MZ-6 cell attachment to VN increased cell motility up to 5-fold accompanied by prominent changes in cytoskeletal organization and cell morphology. Upon alpha(v)beta3/VN interaction, by cDNA expression microarray analysis we identified altered mRNA levels of c-myc, epidermal growth factor receptor (EGF-R), transcription factor Fra-1, prothymosin-alpha (PTMA), integrin-linked kinase (ILK), and the cell adhesion molecule SQM-1, candidates which are possibly involved in changes of the adhesive, migratory, and proliferative phenotype of human ovarian cancer cells.

Overexpression of kallikrein 10 in epithelial ovarian carcinomas

OBJECTIVE

We wanted to identify genes up-regulated in ovarian tumors that might serve as early markers for ovarian cancer. One promising focus is the family of genes that encode secreted proteases, which play essential roles in tumor invasion and metastasis. Kallikrein 10 (KLK10) is a member of the kallikrein family of serine proteases which include 15 proteins, including the prostate-specific antigen (PSA), also known as hK3. We investigated whether KLK10 and its related protein, hK10, might serve as equally accurate markers for ovarian carcinoma.

METHODS

Transcriptional profiling was performed using RNA isolated from normal ovarian epithelium, ovarian cancer cell lines, and primary ovarian tumors. Microarray data were confirmed by Northern blot analysis of 66 ovarian tumor samples and 6 ovarian cancer cell lines. In situ hybridization and Western blot analysis confirmed the Northern blot findings.

RESULTS

KLK10 was more highly expressed by primary ovarian tumors than by NOE. Thirty-two of 35 primary serous ovarian carcinoma samples (91.4%) expressed higher levels of KLK10 than NOE did. Eleven of 15 nonserous epithelial ovarian carcinoma samples (73.3%) and 8 of 11 primary peritoneal carcinoma samples (72.7%) also expressed KLK10. Overall, 84.8% of all epithelial ovarian and peritoneal carcinoma tumor samples showed elevated expression of KLK10. Similarly, Western blot analysis demonstrated that levels of the KLK10-related protein, designated hK10, are elevated in primary ovarian tissue lysates, but the protein is undetectable in immortalized ovarian epithelium. Finally, in situ hybridization established that KLK10 mRNA is much more highly expressed by tumor tissue than by normal epithelium and stromal tissues.

CONCLUSIONS

Our data support recent immunoassay findings of elevated levels of hK10 in the tumor tissue and serum of ovarian cancer patients. Thus, it is likely that KLK10 and other kallikreins will serve as useful diagnostic and prognostic markers in patients with ovarian carcinoma.

Lack of proliferative activity of surface epithelial inclusion cysts of the ovary

Surface epithelial inclusion cysts (SEICs) of the ovary are epithelial inclusions in the ovarian cortex believed to form from invagination of the surface epithelium at the time of ovulation. It has long been theorized that SEICs are related to the development of epithelial ovarian cancer. Ki-67 antigen is a marker of cell proliferation and has been shown to be prognostic in epithelial ovarian cancer. The purpose of this study was to evaluate Ki-67 activity in SEICs to evaluate their possible connection to ovarian neoplastic proliferation. A retrospective review of benign ovaries removed at the time of pelvic surgery was performed. Slides were immunostained with Ki-67. Proliferation index, expressed as the percent of cells staining in SEICs, was calculated. Proliferative activity was scored as negligible, low, moderate, or high, at <5%, 5-10%, 11-40%, and >40%, respectively. Eighteen ovaries from 18 women were evaluated. The percentage of Ki-67 positive cells ranged from 0% to 7%. Ki-67 activity in SEICs of the ovary is negligible to low. Proliferative activity as assessed by Ki-67 staining does not explain any possible relationship of SEICs to epithelial ovarian cancer.

What we have learned from isolated cells from human ovary?

In the ovary, morphodynamics of follicles with cyclic maturation, ovulation and repair occur under the control of various tropic factors. The ovarian functions have been mostly studied by using subhuman primates and non-primate animals because of the limited availability of closely staged human specimens. We have recently established the in vitro culture systems of ovarian surface epithelium (OSE) and granulosa cells of humans, and subsequently developed the immortalization of each cell. The immortalized cell lines may supply us advanced studies on ovarian disorders as well as its physiological functions. On the embryologically putative müllerian potential of coelomic epithelium, endometriosis can be explained by coelomic metaplasia from the peritoneal mesothelium, including OSE. We can microscopically observe a continuity from flat epithelial cells on the ovarian surface or within the cortical inclusion cysts to endometriotic gland cells. The primary human OSE cells exhibited a glandular-stromal structure similar to endometriosis when they were co-cultured with endometrial stromal cells in an estrogen-rich environment. Primary and immortalized OSE cells converted the estrone to estradiol, and expressed the genes for steroidogenic factor-1 (SF-1), p450arom and 17beta-HSDs. This character of OSE was, in part, similar to the granulosa cells. One of the immortalized OSE clone produces disseminated tumors mimicking undifferentiated carcinomas in nude mice. Ovarian granulosa cells play a key role in the functional maturation of the entire follicle. The molecular pathways in granulosa cells responsible for the growth, differentiation, and nursing the oocyte are still largely unknown. Our immortalized human granulosa cell line, GC1a, obtained from developing follicles, showed no steroid hormone biosynthesis, and no detectable expression of the genes for StAR or cytochrome p450 enzymes due to the lack of SF-1. Transfected SF-1 elicited estradiol secretion in GC1a cells with concomitant expression of the genes encoding the proteins for gonadal steroidogenesis. The enzymatic activity of 17beta-HSD was also achieved by SF-1 transgene. These results indicate that SF-1 controls the gene expression required for steroidogenesis in the human developing follicle. Clinically, immortalized GC1a cells from human origin, with steroidogenic capacity, may serve as a feeder layer for in vitro oocyte maturation. Further investigations of our immortalized OSE and granulosa cells of humans will allow us to clarify whether they have a single progenitor cell.

Primary culture and mRNA analysis of human ovarian cells

Established cell lines are invaluable for studying cell and molecular biological questions. A variety of human ovarian cancer (OC) cell lines exist, however, most have acquired significant genetic alterations from their cells of origin, including deletion of important cell cycle regulatory genes. In order to analyze signaling events related to cell cycle control in human OC, we have modified existing protocols for isolating and culturing OC cells from patient ascites fluid and normal ovarian surface epithelial (OSE) cells from benign ovarian tissue sections. These cells maintain an epithelial phenotype and can be manipulated experimentally for several passages before cellular senescence. An example using TGFb1 treatment of OC cells to examine signaling and target gene activation is presented.

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.

Role of X-linked inhibitor of apoptosis protein in chemoresistance in ovarian cancer: possible involvement of the phosphoinositide-3 kinase/Akt pathway

Although cisplatin derivatives are first-line chemotherapeutic agents for the treatment of epithelial ovarian cancer, chemoresistance remains a major hurdle to successful therapy and the molecular mechanisms involved are poorly understood. Apoptosis is the cellular underpinning of cisplatin-induced cell death, which is associated with expression of specific "death" genes and down-regulation of "survival" counterparts. The X-linked inhibitor of apoptosis proteins (Xiap), an intracellular anti-apoptotic protein, plays a key role in cell survival by modulating death signaling pathways and is a determinant of cisplatin resistance in ovarian cancer cells in vitro. This review focuses on the role of Xiap and its interactions with the phosphoinositide-3 kinase (PI3K)/Akt cell survival pathway in conferring resistance of ovarian cancer cells to chemotherapeutic agents and discusses potential therapeutic strategies in overcoming chemoresistant ovarian cancer.

Molecular pathogenesis of granulosa cell tumours

Granulosa cell tumours (GCT) of the ovary arise from granulosa cells of the ovary on morphological, biochemical and molecular criteria. In order to understand the molecular pathogenesis of these tumours better we have sought to define their molecular phenotype, to identify activating mutations of the FSH-signalling pathway, to characterise their estrogen receptor expression and to explore the hypothesis that GCT may be resistant to inhibin. The pattern of gene expression observed in GCT suggests a phenotype which is similar to that of late preovulatory granulosa cells which would be consistent with activation of the FSH receptor signalling pathway, however, there is no evidence for activating mutations of either the FSH receptor or the associated trimeric G-proteins. Estrogen receptor beta is abundantly expressed in GCT. The various subunits and isoforms of the activin-inhibin receptor are expressed in GCT. These observations provide a basis for future studies of GCT, including further characterisation of signalling pathways known to be important in the regulation of granulosa cell growth and differentiation.

Microarray analysis of gene expression mirrors the biology of an ovarian cancer model

We have previously described an ovarian cancer model based on four independent spontaneously immortalized epithelial ovarian cancer cell lines (TOV-21G, TOV-81D, TOV-112D and OV-90) from patients who were never exposed to chemotherapy or radiation therapy. These cell lines are particularly interesting since they retain characteristics of the original epithelial ovarian cancers (EOC) from which they were derived. Here we report the characterization of this model system using high-density DNA microarrays in order to assess gene expression. Expression profiles were generated from total RNAs extracted from the four EOC cell lines. For comparison, expression profiling is also provided for a primary culture of normal ovarian surface epithelium (NOV-31) and a fresh EOC sample (TOV-578G). Comparison of expression profiles revealed patterns of expression that distinguish NOV-31 from that of all tumor derived samples. The expression pattern of TOV-81D, an EOC cell line that was derived from a patient with indolent disease, most closely resembles NOV-31 while profiles of samples derived from patients with more aggressive disease (TOV-21G, OV-90, TOV-112D and TOV-578G) showed more divergent patterns of expression. The microarray analysis (http://genome.mcgill.ca) results confirm the usefulness of an ovarian cancer model based on the characterization of these EOC cell lines.