Human Ovarian Surface Epithelial Cells Research Articles

Abstract B19: Functional genomics approach links anchorage-independence with tumor dormancy in ovarian cancer

Abstract Although a number of genes are aberrantly regulated in ovarian cancer, little is known about which genes are functionally important. The aim of this study was to identify new genes relevant to anchorage-independent growth of ovarian cancer cells through a genome-wide functional screening approach. We performed lentiviral transduction of a library of 81,000 shRNAs (Cellecta, Inc.) targeting 15,000 genes into an immortalized human ovarian surface epithelium cell line and 7 ovarian cancer cell lines (OVCA420, OVCA433, OVCA429, CAOV3, SKOV8, Tyk-nu and DOV13) which do not generate anchorage-independent colonies in soft agar. Among these, only OVCA420 generated colonies larger than 100 micrometers after shRNA library transduction. We extracted DNA from these colonies, amplified the shRNA constructs with PCR, and inserted the amplicons back into the original lentiviral vector, thus generating a secondary library of 68 shRNAs. Subsequent analysis, performed to examine the reproducible formation of anchorage-independent colonies using the secondary library, identified 5 shRNAs targeting ABHD2, CYB5R3, MR1, ELAC2 and CCL22. Interestingly, population doubling time was increased following transduction of these shRNAs (44.8, 50.1, 43.9, 28.0 and 33.2 hours, respectively) compared to the original or control shRNA-transducted OVCA420 cells (22.4 and 23.7 hours, respectively). Furthermore, side populations detected by efflux of Hoechst 33342 dye were drastically increased (50.5, 46.6, 55.5, 76.5 and 41.1%, respectively) compared to the original or control shRNA-transducted OVCA420 cells (7.3 and 10.4%, respectively). Although these data are not conclusive, they support that a phenotypic change occurs as ovarian cancer cells leave the primary tumor and are suspended in ascites. We found that repression of any one of these particular genes was sufficient to avoid anoikis. This change was accompanied by suppression of cell proliferation and increased efflux of Hoechst 33342 dye, which indicates activation of pumping function, suggesting a change to chemoresistant dormant cells. In summary, our functional genomics approach suggests a molecular mechanism underlying the process of anchorage independence, tumor dormancy and chemoresistance in ovarian cancer. Citation Format: Noriomi Matsumura, Koji Yamanoi, Yasuaki Amano, Junzo Hamanishi, Tsukasa Baba, Susan K. Murphy, Ikuo Konishi. Functional genomics approach links anchorage-independence with tumor dormancy in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr B19.

Protein-tyrosine Phosphatase 1B Antagonized Signaling by Insulin-like Growth Factor-1 Receptor and Kinase BRK/PTK6 in Ovarian Cancer Cells*♦

Ovarian cancer, which is the leading cause of death from gynecological malignancies, is a heterogeneous disease known to be associated with disruption of multiple signaling pathways. Nevertheless, little is known regarding the role of protein phosphatases in the signaling events that underlie the disease; such knowledge will be essential to gain a complete understanding of the etiology of the disease and how to treat it. We have demonstrated that protein-tyrosine phosphatase 1B (PTP1B) was underexpressed in a panel of ovarian carcinoma-derived cell lines, compared with immortalized human ovarian surface epithelial cell lines. Stable restoration of PTP1B in those cancer cell lines substantially decreased cell migration and invasion, as well as proliferation and anchorage-independent survival. Mechanistically, the pro-survival IGF-1R signaling pathway was attenuated upon ectopic expression of PTP1B. This was due to dephosphorylation by PTP1B of IGF-1R β-subunit and BRK/PTK6, an SRC-like protein-tyrosine kinase that physically and functionally interacts with the IGF-1R β-subunit. Restoration of PTP1B expression led to enhanced activation of BAD, one of the major pro-death members of the BCL-2 family, which triggered cell death through apoptosis. Conversely, inhibition of PTP1B with a small molecular inhibitor, MSI-1436, increased proliferation and migration of immortalized HOSE cell lines. These data reveal an important role for PTP1B as a negative regulator of BRK and IGF-1Rβ signaling in ovarian cancer cells.

VAV1 represses E-cadherin expression through the transactivation of Snail and Slug: a potential mechanism for aberrant epithelial to mesenchymal transition in human epithelial ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy in the western world. Although patients with early-stage ovarian cancer generally have a good prognosis, approximately 20%-30% of patients will die of the disease, and 5-year recurrence rates are 25%-45%, highlighting the need for improved detection and treatment. We investigated the role of VAV1, a protein with guanine nucleotide exchange factor activity, which is associated with survival in patients with early-stage ovarian cancer (International of Obstetrics and Gynecology [FIGO] stages I and II). We analyzed 88 samples from patients with primary epithelial ovarian cancer, which were divided into FIGO stages I and II (n = 46), and III and IV (n = 42). Prognostic analysis revealed that upregulated VAV1 expression correlated significantly with poor prognosis in patients with early-stage epithelial ovarian cancer (P ≤ 0.05), but not with other clinicopathologic features. Stable overexpression of VAV1 in human high-grade serous ovarian cancer SKOV3 cells induced morphologic changes indicative of loss of intercellular adhesions and organized actin stress fibers. Western blotting and real-time reverse transcriptase-polymerase chain reaction demonstrated that these cells had downregulated E-cadherin protein and messenger RNA levels, respectively. This downregulation is associated with epithelial-mesenchymal transition (EMT) and invasive cancer. Furthermore, VAV1 overexpression in both SKOV3 and human ovarian surface epithelial cells demonstrated that its upregulation of an E-cadherin transcriptional repressor, Snail and Slug, was not confined to ovarian cancer cells. Conversely, knockdown of VAV1 by RNA interference reduced Snail and Slug. Our findings suggest that VAV1 may play a role in the EMT of ovarian cancer, and may serve as a potential therapeutic target.

Mammaglobin B (SCGB2A1) is a novel tumour antigen highly differentially expressed in all major histological types of ovarian cancer: implications for ovarian cancer immunotherapy

Background:We studied the genetic fingerprints of ovarian cancer and validated the potential of Mammaglobin b (SCGB2A1), one of the top differentially expressed genes found in our analysis, as a novel ovarian tumour rejection antigen.Methods:We profiled 70 ovarian carcinomas including 24 serous (OSPC), 15 clear-cell (CC), 24 endometrioid (EAC) and 7 poorly differentiated tumours, and 14 normal human ovarian surface epithelial (HOSE) control cell lines using the Human HG-U133 Plus 2.0 chip (Affymetrix). Quantitative real-time PCR and immunohistochemistry staining techniques were used to validate microarray data at RNA and protein levels for SCGB2A1. Full-length human-recombinant SCGB2A1 was used to pulse monocyte-derived dendritic cells (DCs) to stimulate autologous SCGB2A1-specific cytotoxic T-lymphocyte (CTL) responses against chemo-naive and chemo-resistant autologous ovarian tumours.Results:Gene expression profiling identified SCGB2A1 as a top differentially expressed gene in all histological ovarian cancer types tested. The CD8+ CTL populations generated against SCGB2A1 were able to consistently induce lysis of autologous primary (chemo-naive) and metastatic/recurrent (chemo-resistant) target tumour cells expressing SCGB2A1, whereas autologous HLA-identical noncancerous cells were not lysed. Cytotoxicity against autologous tumour cells was significantly inhibited by anti-HLA-class I (W6/32) monoclonal antibody. Intracellular cytokine expression measured by flow cytometry showed a striking type 1 cytokine profile (i.e., high IFN-γ secretion) in SCGB2A1-specific CTLs.Conclusion:SCGB2A1 is a top differentially expressed gene in all major histological types of ovarian cancers and may represent a novel and attractive target for the immunotherapy of patients harbouring recurrent disease resistant to chemotherapy.

Valeriana jatamansi Constituent IVHD-valtrate As a Novel Therapeutic Agent to Human Ovarian Cancer: in vitro and in vivo Activities and Mechanisms

Identification of novel chemotherapeutic agents from traditional medicines and elucidation of the molecular basis of their anticancer effects are critical and urgently needed for modern pharmacotherapy. We previously found that analogs of the compounds present in Valeriana jatamansi, a traditional medicine used to treat mental disorders, possess notable antitumor properties; however, the underlying molecular mechanisms have not been fully demonstrated. In this study, we evaluated the anticancer effects of IVHD-valtrate, one of the most active Valeriana jatamansi derivatives, against human ovarian cancer cells in vitro and in vivo. IVHD-valtrate inhibited the growth and proliferation of the A2780 and OVCAR-3 ovarian cancer cell lines in a concentration-dependent manner, while relatively low cytotoxicity to immortalized non-tumorigenic human ovarian surface epithelial cells (IOSE-144) was observed. Treatment with IVHD-valtrate arrested the ovarian cancer cells in the G2/M phase and induced apoptosis, and significantly suppressed the growth of A2780 and OVCAR3 xenograft tumors in a dose-dependent manner. The detailed in vitro and in vivo study on the molecular mechanisms of this compound demonstrated that IVHD-valtrate exposure modulated the expression of numerous molecules involved in cell cycle progression and apoptosis regardless of p53 status, leading to increase the level of p53, Rb, p21, p27 and decrease Mdm2, E2F1, Cyclin B1, Cdc25C and Cdc2. It also down-regulated Bcl-2/Bax and Bcl-2/Bad ratio and enhanced the cleavage of PARP and Caspases. Our preclinical results indicated IVHD-valtrate is a potential therapeutic agent for ovarian cancer, providing a basis for development of the compound as a novel chemotherapeutic agent.

Abstract A06: Integration of synthetic lethality and genomic data to identify significant molecular vulnerabilities in ovarian cancer

Abstract Background: Epithelial ovarian cancer (EOC) is the second leading cause of death from a gynecologic malignancy in the U.S. The overall survival rate has not changed over the last 30 years thereby necessitating new therapeutic approaches. Targeted therapeutics that have come to the forefront of exploration such as anti-VEGF and anti-EGFR, have resulted in only marginal improvements in overall survival. We have used a functional genomics approach followed by analyzing TCGA (The Cancer Genome Atlas) ovarian dataset to help identify significant potential molecular targets that represent key points of therapeutic intervention. Methods: We employed an unbiased high-throughput lethality screen using a 24,088 siRNA library targeting 6,022 “druggable” genes and tested for effects on growth and/or survival of A1847 EOC cells. Candidate hits from the primary screen were rescreened in a secondary screen across six additional EOC cell lines (OVCAR5, SKOV3, A2780, C30, CP70 and UPN275), and three non-tumorigenic, immortalized human ovarian surface epithelial (HOSE) cell lines (HIO-80, HIO-117, HIO-120). We further validated and eliminated the leading hits which may be due to potential off-target effects by rescreening individual siRNAs from the initial siRNAs pools and by performing quantitative RT-PCR and western blotting. Mechanistic exploration with each of the lead candidates was performed in A2780 cells using Guava cell cycle and Nexin assays. Clinical datasets for lead candidate genes were obtained from https://tcga-data.nci.nih.gov/tcga/ (n=494) and analyzed for gene expression, DNA methylation, copy number variation (CNV) and survival (Kaplan-Meier analysis). Results: Building on the concept of “oncogenic addiction” we performed a primary lethality screen using A1847 cells and identified 300 genes that were considered essential for tumor cell growth and/or survival. These hits were defined as a gene that reduced cell viability by >15% with a false discovery rate of ≤5%. In the secondary screen, each of the ten cell lines exhibited a unique number of hits ranging from 27-94% of the total siRNAs screened. Fifty-three gene candidates were found to exhibit effects in all seven tumorigenic cell lines. Extensive validation of these hits refined the list to four top priority candidates (HSPA5, NDC80, NUF2 and PTN) that reduced the viability of all the EOC cell lines with minimal effects on the non-tumorigenic HOSE lines. In A2780 cells, HSPA5, NDC80, NUF2 and PTN siRNA treatment led to an average 2.5-fold (n=3, p<0.05) increase in apoptotic cells as compared to control siRNA. Analysis of TCGA ovarian dataset showed NDC80, NUF2 and PTN to be over-expressed (>1.5-fold increase compared with normal tissues) in 99.8%, 99.8% and 40% of patients, respectively. CNV analysis for these three genes showed that the samples with copy number gain exhibited an average 1.6-fold increase (p-value <0.0001, <0.0001 and <0.05 for NDC80, NUF2 and PTN, respectively) in gene expression as compared to samples with no copy number gain. HSPA5 was not found to be significantly over-expressed in ovarian tumors as evaluated by TCGA. DNA methylation analysis showed promoter regions of NDC80, NUF2 and PTN to be hypomethylated (beta values <0.25) in 94% of the tumor samples. KM-survival analysis showed that higher expression of NUF2 mRNA was related to poor prognosis in ovarian cancer patients. Conclusion: Our functional studies integrated with genomics data provide an important, unbiased avenue towards addressing an urgent and unmet clinical need for identification of prospective therapeutic targets for drug discovery and treatment of ovarian cancer. Citation Format: Geetika Sethi, Harsh Pathak, Hong Zhang, Yan Zhou, Margaret B. Einarson, Vinod Vathipadiekal, Sumedha Gunewardena, Michael J. Birrer, Andrew K. Godwin. Integration of synthetic lethality and genomic data to identify significant molecular vulnerabilities in ovarian cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Synthetic Lethal Approaches to Cancer Vulnerabilities; May 17-20, 2013; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(5 Suppl):Abstract nr A06.

NF-YA Underlies EZH2 Upregulation and Is Essential for Proliferation of Human Epithelial Ovarian Cancer Cells

Epithelial ovarian cancer (EOC) accounts for the most gynecologic malignancy-associated deaths in the United States. Enhancer of zeste homolog 2 (EZH2), which silences gene expression through generating trimethylation on lysine 27 residue of histone H3 (H3K27Me3), is often overexpressed in EOCs and has been suggested as a therapeutic target. However, the mechanism underlying EZH2 overexpression in EOCs is unknown. Here, we show that EZH2 is upregulated at the transcription level, and two CCAAT boxes in the proximal regions of the human EZH2 gene promoter are critical for its transcription in EOC cells. Indeed, NF-YA, the regulatory subunit of the CCAAT-binding transcription factor NF-Y, is expressed at higher levels in human EOCs than in primary human ovarian surface epithelial (HOSE) cells. In addition, there is a positive correlation between expression of NF-YA and EZH2 in EOCs. Notably, high NF-YA expression predicts shorter overall survival in patients with EOCs. The association of NF-YA with the promoter of the human EZH2 gene is enhanced in human EOC cells compared with primary HOSE cells. Significantly, knockdown of NF-YA downregulates EZH2, decreases H3K27Me3 levels, and suppresses the growth of human EOC cells both in vitro and in a xenograft mouse model. Notably, NF-YA knockdown induces apoptosis of EOC cells and ectopic EZH2 expression partially rescues apoptosis induced by NF-YA knockdown. Together, these data reveal that NF-Y is a key regulator of EZH2 expression and is required for EOC cell proliferation, thus representing a novel target for developing EOC therapeutics.

Abstract 1039: HO-3867, is selectively cytotoxic to ovarian cancer cells through a dual mechanism of action involving the STAT3 and AKT pathways .

Abstract Objective: The development of anticancer drugs that selectively kills cancer cells while sparing the surrounding healthy tissues is of paramount importance for safe and effective anti-cancer therapy. We have developed a novel class of compounds that are fluoro-substituted analogs of curcumin, called diarylidenylpiperiden-4-ones (DAPs). We hypothesize that the structural backbone of DAP compounds would have cytotoxic activity, and the -NOH moiety would function as a tissue-specific modulator of this cytotoxicity via its anti-oxidant properties. The goal of this study was to analyze the differential cytotoxic effects of one of these compounds, HO-3867, on both ovarian cancer and normal cells. Methods: Protein expression in pro-apoptotic and survival signaling pathways were analyzed via western blotting, and immunofluorescence assays using human ovarian cancer (SKOV-3) and normal ovarian surface epithelial (hOSE) cell lines treated with 10 μM HO-3867. Flow cytometry was used to quantify apoptosis and immunohistochemistry was performed to analyze cellular localization of proteins. The selective cytotoxic effect of HO-3867 was verified using STAT3 cDNA and Akt siRNA transfection. In vivo analysis was performed on mice administered oral HO-3867 using histopathological analysis and TUNEL assays. Efficacy of HO-3867 proved in STAT3 knockdown SKOV3 ovarian cancer cell line. Results: HO-3867 did not affect the proliferation rate of hOSE cells while showing potent cytotoxic activity against SKOV-3 cells. In vivo histopathological evaluation of internal organs collected from treated adult mice revealed no evidence of toxicity. TUNEL staining of collected tissues suggested that selective apoptotic induction was limited to neoplastic cells in tumor xenografts. HO-3867 protected the normal cells by up-regulating the pro-survival protein pAkt. Tumor cells were targeted through downregulation of pAkt, pStat3, pErk1/2 and Bcl2 and upregulation of p21 and p53. Furthermore, HO-3867 was selectively regulates kinase activity in ovarian cancer cells and compared with hOSE cells. In addition, HO-3867 treated into STAT3 knockdown SKOV3 cells, resulted in the decreased apoptosis. These data indicated that HO-3867 induced apoptosis through the targeting STAT3. Conclusion: Our results showed that HO-3867 protects normal cells while retaining antiproliferative activity against ovarian cancer cells. Increased levels of pAkt and the free radical-scavenging effects of the pro-nitroxide N-hydroxypyrroline group mediate this selective protection. The results suggest that the antioxidant-conjugated DAPs may be useful as safe and effective anticancer agents for treatment of ovarian cancer Citation Format: Georgia A. McCann, Kellie S. Rath, Shan Naidu, Pushpa Lata, Bid Hemant, Meryl Sudhakar, Kálmán Hideg, Peter Houghton, Periannan Kuppusamy, David E. Cohn, Karuppaiyah Selvendiran. HO-3867, is selectively cytotoxic to ovarian cancer cells through a dual mechanism of action involving the STAT3 and AKT pathways . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1039. doi:10.1158/1538-7445.AM2013-1039

Abstract 561: Loss of lamin A/C and p53 in mouse embroyic fibroblasts affect the cell cycle and chromosomal stability .

Abstract Ovarian cancer is the most lethal of gynecological cancers being the fifth leading cause of cancer-associated deaths. Reduced expression or loss of lamin A/C has been demonstrated in 47% of ovarian cancers, as well. Lamins A and C are intermediate filament proteins and are major components of the nuclear lamina that provide structure to the nucleus. Mutations in lamins A/ C are the source of several nuclear envelope diseases, namely laminopathies, such as muscular dystrophy. Interestingly, data acquired from research on laminopathy patient samples, as well as from in vitro, and in vivo murine models have revealed that tissue affected by lamin A/C mutations display characteristics similar to neoplastic or malignant cells, such as defective nuclear architecture and changes in ploidy. Further, reduced expression or loss of lamin A/C has been demonstrated in ovarian, breast, and small-cell lung cancers, and has been associated with poor outcome in gastric carcinomas and hematologic malignancies. We previously found that siRNA suppression of lamin A/C in human ovarian surface epithelial cells results in deformed nuclear morphology, p21 induction, decreased mitosis, delayed cell growth, and aneuploidy. Accordingly, we currently investigated how concomitant loss of lamin A/C and p53 (LAC/p53 KO) affect the cell cycle and chromosome content in germ line LAC/p53 knockout mouse embryonic fibroblasts (MEFs) through western blotting and flow cytometry. We found that that in nonsynchronized early and late passage LAC/p53 KO MEFs cell cycle inhibitors p16 and p19, as well as pRB, cyclin D1, and PCNA expression is upregulated compared to the lamin A/C knockout and wild type controls. Surprisingly, this expression pattern is also observed under serum-starved conditions. Cyclin D1, PCNA, and pRB expression is also substantially upregulated in late passage MEFs. Further, early and late passage LAC/p53 KO MEFs possess a considerably larger mitotic and aneuploid cell population than the controls. As lamin A/C is a fundamental structural nuclear protein, it is hypothesized that lamin A/C knockout MEFs display reduced mitosis and hindered cell growth to prevent malignancy. Additional loss of a functional cell cycle, and checkpoint protein like p53, may reverse the initial phenotype to promote tumorigenesis, particularly if chromosomal instability is already established. Our experimental results support the ideas that loss of lamin A/C protein is synergistic with p53 inactivation in promoting cell cycle progression and chromosomal instability to potentially induce tumorigenesis. The mechanism of the aforementioned findings and the potential to induce ovarian tumorigenesis are under further investigation in vivo. Citation Format: Santas Rosario, Deylosse C. Capo-Chichi, Robert Moore, Xiang-xi M. Xu. Loss of lamin A/C and p53 in mouse embroyic fibroblasts affect the cell cycle and chromosomal stability . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 561. doi:10.1158/1538-7445.AM2013-561

Abstract 3201: PTBP1 stability is increased in ovarian and breast cancer cell lines compared to matched controls.

Abstract PTBP1 (polypyrimidine tract-binding) protein is a splicing factor that is frequently upregulated in ovarian and breast tumors. Knockdown (KD) of PTBP1 expression by shRNA impairs ovarian tumor cell growth in vivo and in vitro, as well as colony formation and invasiveness in vitro (He et al, Oncogene 26:4961-8, 2007). We have also found that PTBP1 is progressively upregulated in immortalized human mammary epithelial cells (HMECs) and human ovarian surface epithelial (HOSE) cells, correlating with their transformation state. These results prompted us to determine the factors that play a role in the upregulation of PTBP1 protein expression. We first asked whether the increased PTBP1 protein in human ovarian and breast cell lines is accompanied by proportional increases of PTBP1 mRNA. We found that there was a discordance between PTBP1 mRNA and protein levels, as measured by RT-PCR and western blot, in these cancer cell lines in relation to the control cells (finite lifespan HMEC or HOSE, respectively). Accordingly, we attempted to understand the basis for this discrepancy, and measured PTBP1 protein half-life. We treated A2780 (ovarian cancer), MCF7 (breast cancer) cells, and “finite lifespan” HMEC (184A1) with cycloheximide to terminate protein synthesis and followed the fate of PTBP1 protein over time by western blot. We found that the half-life of PTBP1 protein is ∼3-5 h in the HMECs with finite lifespan, whereas it ranges from ∼9-12h in human epithelial ovarian and breast cancer cells. These results demonstrate that PTBP1 expression is regulated in part by events that control the stability of the protein and suggest that the normal regulation of PTBP1 protein turnover is altered in cancer cell lines. Bioinformatics analysis identified one possible SUMO-binding motif site within the PTBP1 protein (SUMOsp 2.0 - SUMOylation Site Prediction, http://sumosp.biocuckoo.org/), suggesting that SUMOylation may play a role in PTBP1 stability; we are currently examining this possibility. Findings presented herein will enhance our understanding of the regulation of PTBP1 expression and the mechanisms underlying its variation in protein and mRNA levels in ovarian and breast tumors. (Support in part by NCI grants R01 CA40570 and R01 CA138762 [to WTB], by OCRF [to XH], and by UIC.) Citation Format: Ahmet Dirim Arslan, Szilard Asztalos, Martha Stampfer, Debra Tonetti, Xiaolong He, William T. Beck. PTBP1 stability is increased in ovarian and breast cancer cell lines compared to matched controls. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3201. doi:10.1158/1538-7445.AM2013-3201

Microenvironmental Regulation of BRCA1 Gene Expression by c-Jun and Fra2 in Premalignant Human Ovarian Surface Epithelial Cells

Reduced BRCA1 gene expression is common in the sporadic form of ovarian carcinoma. The spread of this highly lethal cancer often begins when tumor cell clusters are shed into the fluid of the abdominopelvic cavity such that they can float freely before seeding distant sites on the peritoneal walls and organs. Thus, the microenvironment that tumor cells find themselves in changes dramatically during these early shedding and floating stages of transperitoneal metastasis. To mimic this microenvironmental change in vitro, we released premalignant human ovarian surface epithelial cells from the substratum and forced them to cluster in suspension. Under these conditions, steady state levels of BRCA1 mRNA and protein fell significantly and the transcriptional activation state of the BRCA1 promoter was suppressed. Analysis of the promoter indicated that the previously identified "CRE" element located within the "positive regulatory region" (PRR) contributed to this suppression. More specifically, we show that the suppression was mediated, at least in part, by a suspension culture-driven decrease in the levels of two members of the AP1 transcription factor complex, c-Jun and Fra2, that bind to the CRE element. Therefore, a microenvironmental change that is manifested during the initial stages of ovarian carcinoma dissemination may, potentially, help suppress BRCA1 expression in sporadic tumors and thus promote their progression.

PTEN loss and HOXA10 expression are associated with ovarian endometrioid adenocarcinoma differentiation and progression

Epithelial ovarian cancer is a heterogeneous disease that is subdivided into five major histotypes but the mechanisms driving their differentiation are not clear. Mutations in adenomatous polyposis coli (APC) and β-catenin are commonly observed in the human ovarian endometrioid adenocarcinoma (OEA) patients. However, the mechanisms subsequent to APC deletion in ovarian tumorigenesis have not been well characterized. We have conditionally deleted APC in the murine ovarian surface epithelium (OSE) and showed that its loss leads to development of epithelial inclusion cysts. High-grade OEAs with tightly packed villoglandular histology were observed in older APC-deleted mice. Phosphatase and tensin homolog (PTEN) expression was elevated in the early lesions but lost after progression to the more advanced tumors. Knockdown of APC or expression of a gain-of-function β-catenin similarly induced human OSE cells to develop tumors with endometrioid histology in xenografts. Expression of HOXA10 was induced in both the advanced APC-deleted murine tumors and in the tumor xenografts of human OSE cells with knocked-down APC. These results show that reduced APC activity is sufficient to induce formation of epithelial inclusion cysts and support OEA development and suggest that induced HOXA10 expression and loss of PTEN are key mechanisms driving endometrioid histotype differentiation and progression.

Transformation of human ovarian surface epithelial cells by Krüppel-like factor 8

Previously we demonstrated that Krüppel-like factor 8 (KLF8) participates in oncogenic transformation of mouse fibroblasts and is highly overexpressed in human ovarian cancer. In this work, we first correlated KLF8 overexpression with the aggressiveness of ovarian patient tumors and then tested if KLF8 could transform human ovarian epithelial cells. Using the immortalized non-tumorigenic human ovarian surface epithelial cell line T80 and retroviral infection, we generated cell lines that constitutively overexpress KLF8 alone or its combination with the known ovarian oncogenes c-Myc, Stat3c and/or Akt and examined the cell lines for anchorage-independent growth and tumorigenesis. The soft agar clonogenic assay showed that T80/KLF8 cells formed significantly more colonies than the mock cells. Interestingly, the cells expressing both KLF8 and c-Myc formed the largest amounts of colonies greater than the sum of colonies formed by the cells expressing KLF8 and c-Myc alone. These results suggested that KLF8 might be a weak oncogene that works cooperatively with c-Myc to transform ovarian cells. Surprisingly, overexpression of KLF8 alone was sufficient to induce tumorigenesis in nude mice resulting in short life span whether the T80/KLF8 cells were injected subcutaneously, intraperitoneally or orthotopically into the ovarian bursa. Histopathological studies confirmed that the T80/KLF8 tumors were characteristic of human serous ovarian carcinomas. Comparative expression profiling and functional studies identified the cell cycle regulators cyclin D1 and USP44 as primary KLF8 targets and effectors for the T80 transformation. Overall, we identified KLF8 overexpression as an important factor in human ovarian carcinoma pathogenesis.

Elevated levels of circulating microRNA-200 family members correlate with serous epithelial ovarian cancer

BackgroundThere is a critical need for improved diagnostic markers for high grade serous epithelial ovarian cancer (SEOC). MicroRNAs are stable in the circulation and may have utility as biomarkers of malignancy. We investigated whether levels of serum microRNA could discriminate women with high-grade SEOC from age matched healthy volunteers.MethodsTo identify microRNA of interest, microRNA expression profiling was performed on 4 SEOC cell lines and normal human ovarian surface epithelial cells. Total RNA was extracted from 500 μL aliquots of serum collected from patients with SEOC (n = 28) and age-matched healthy donors (n = 28). Serum microRNA levels were assessed by quantitative RT-PCR following preamplification.ResultsmicroRNA (miR)-182, miR-200a, miR-200b and miR-200c were highly overexpressed in the SEOC cell lines relative to normal human ovarian surface epithelial cells and were assessed in RNA extracted from serum as candidate biomarkers. miR-103, miR-92a and miR -638 had relatively invariant expression across all ovarian cell lines, and with small-nucleolar C/D box 48 (RNU48) were assessed in RNA extracted from serum as candidate endogenous normalizers. No correlation between serum levels and age were observed (age range 30-79 years) for any of these microRNA or RNU48. Individually, miR-200a, miR-200b and miR-200c normalized to serum volume and miR-103 were significantly higher in serum of the SEOC cohort (P < 0.05; 0.05; 0.0005 respectively) and in combination, miR-200b + miR-200c normalized to serum volume and miR-103 was the best predictive classifier of SEOC (ROC-AUC = 0.784). This predictive model (miR-200b + miR-200c) was further confirmed by leave one out cross validation (AUC = 0.784).ConclusionsWe identified serum microRNAs able to discriminate patients with high grade SEOC from age-matched healthy controls. The addition of these microRNAs to current testing regimes may improve diagnosis for women with SEOC.

The Lymphotactin Receptor Is Expressed in Epithelial Ovarian Carcinoma and Contributes to Cell Migration and Proliferation

Chemokine receptor-ligand interactions are important to support functioning of both normal and pathologic cells. The expression and function of chemokine receptors in epithelial ovarian carcinoma (EOC) is largely unknown. Here, we report that the lymphotactin receptor (XCR1) was expressed in primary and metastatic human epithelial ovarian carcinoma (EOC) specimens and cell lines. In contrast, expression of XCR1 was not detected in the normal ovary or in human normal ovarian surface epithelial cells. Our data indicate that XCL1 and XCL2 are either present in the malignant ascites or expressed by the ovarian carcinoma cells. The addition of lymphotactin (XCL1 and XCL2) stimulated migration and proliferation of XCR1-positive cells. Reduction of XCR1 expression in ovarian carcinoma cell line SKOV-3 resulted in abrogated diaphragm and peritoneal wall tumor formation and in reduced frequency of colonic, splenetic, and liver nodules in an in vivo xenograft mouse model. Taken together, our data suggest that XCR1 is expressed early during the course of tumorigenic transformation and contributes towards increased cell migration and proliferation, which can facilitate the prometastatic behavior of EOC cells.

The Polyoma Virus Large T Binding Protein p150 Is a Transcriptional Repressor of c-MYC

p150, product of the SALL2 gene, is a binding partner of the polyoma virus large T antigen and a putative tumor suppressor. p150 binds to the nuclease hypersensitive element of the c-MYC promoter and represses c-MYC transcription. Overexpression of p150 in human ovarian surface epithelial cells leads to decreased expression, and downregulation to increased expression, of c-MYC. c-MYC is repressed upon restoration of p150 to ovarian carcinoma cells. Induction of apoptosis by etoposide results in recruitment of p150 to the c-MYC promoter and to repression of c-MYC. Analysis of data in The Cancer Genome Atlas shows negative correlations between SALL2 and c-MYC expression in four common solid tumor types.

MicroRNA expression in ovarian carcinoma and its correlation with clinicopathological features

BackgroundMicroRNA (miRNA) expression is known to be deregulated in ovarian carcinomas. However, limited data is available about the miRNA expression pattern for the benign or borderline ovarian tumors as well as differential miRNA expression pattern associated with histological types, grades or clinical stages in ovarian carcinomas. We defined patterns of microRNA expression in tissues from normal, benign, borderline, and malignant ovarian tumors and explored the relationship between frequently deregulated miRNAs and clinicopathologic findings, response to therapy, survival, and association with Her-2/neu status in ovarian carcinomas.MethodsWe measured the expression of nine miRNAs (miR-181d, miR-30a-3p, miR-30c, miR-30d, miR-30e-3p, miR-368, miR-370, miR-493-5p, miR-532-5p) in 171 formalin-fixed, paraffin-embedded ovarian tissue blocks as well as six normal human ovarian surface epithelial (HOSE) cell lines using Taqman-based real-time PCR assays. Her-2/neu overexpression was assessed in ovarian carcinomas (n = 109 cases) by immunohistochemistry analysis.ResultsExpression of four miRNAs (miR-30c, miR-30d, miR-30e-3p, miR-370) was significantly different between carcinomas and benign ovarian tissues as well as between carcinoma and borderline tissues. An additional three miRNAs (miR-181d, miR-30a-3p, miR-532-5p) were significantly different between borderline and carcinoma tissues. Expression of miR-532-5p was significantly lower in borderline than in benign tissues. Among ovarian carcinomas, expression of four miRNAs (miR-30a-3p, miR-30c, miR-30d, miR-30e-3p) was lowest in mucinous and highest in clear cell samples. Expression of miR-30a-3p was higher in well-differentiated compared to poorly differentiated tumors (P = 0.02), and expression of miR-370 was higher in stage I/II compared to stage III/IV samples (P = 0.03). In multivariate analyses, higher expression of miR-181d, miR-30c, miR-30d, and miR-30e-3p was associated with significantly better disease-free or overall survival. Finally, lower expression of miR-30c, miR-30d, miR-30e-3p and miR-532-5p was significantly associated with overexpression of Her-2/neu.ConclusionsAberrant expression of miRNAs is common in ovarian tumor suggesting involvement of miRNA in ovarian tumorigenesis. They are associated with histology, clinical stage, survival and oncogene expression in ovarian carcinoma.

Ezrin Overexpression by Transformed Human Ovarian Surface Epithelial Cells, Ovarian Cleft Cells, and Serous Ovarian Adenocarcinoma Cells

We have shown that ezrin expression correlates with ovarian epithelial cancer (OVCA) cell proliferation and metastatic behavior. In this study, we evaluated ezrin expression in transformed ovarian superficial epithelial cells (OSE) in ovarian clefts and in culture. Immunohistochemistry and Western blotting for immunoreactive ezrin (ir-ezrin) in normal ovarian tissue, cultured OSE, and ovarian epithelial cancer cells. While ir-ezrin was not demonstrable in normal cuboidal surface cells or interior ovarian organelles, cells lining the ovarian clefts strongly expressed ir-ezrin. Long-term culture of OSE increased ezrin expression and cytological abnormalities. Administration of estradiol and insulin at levels reported in inclusions dramatically induced OSE ir-ezrin expression to OVCA levels and membrane specializations; ruffling, pseudopodia and filopodia. Moreover epidermal growth factor (EGF) drastically increased ezrin translocation in OSE cells in a time-dependent manner. Ezrin expression by OSE increases during transformation. Ezrin expression is responsive to estradiol and growth factors previously shown to be present in ovarian inclusions. These findings suggest that the microenvironment in ovarian inclusions and clefts contributes to the development of OVCA. Our findings elaborate on the mechanism of the ovarian origin of OVCA.

Casein kinase I epsilon interacts with mitochondrial proteins for the growth and survival of human ovarian cancer cells

Epithelial ovarian cancer is the leading cause of death among gynaecologic cancers in Western countries. Our studies have shown that casein kinase I-epsilon (CKIε), a Wnt pathway protein, is significantly overexpressed in ovarian cancer tissues and is associated with poor survival. Ectopic expression of CKIε in normal human ovarian surface epithelial cells and inhibition of CKIε in ovarian cancer cells and in xenografts demonstrated the importance of CKIε in regulating cell proliferation and migration. Interestingly, CKIε function did not seem to involve β-catenin activity. Instead, CKIε was found to interact with several mitochondrial proteins including adenine nucleotide translocase 2 (ANT2). Inhibition of CKIε in ovarian cancer cells resulted in suppression of ANT2, downregulation of cellular ATP and the resulting cancer cells were more susceptible to chemotherapy. Our studies indicate that, in the context of ovarian cancer, the interaction between CKIε and ANT2 mediates pathogenic signalling that is distinct from the canonical Wnt/β-catenin pathway and is essential for cell proliferation and is clinically associated with poor survival.

BRCA1 Regulates Follistatin Function in Ovarian Cancer and Human Ovarian Surface Epithelial Cells

Follistatin (FST), a folliculogenesis regulating protein, is found in relatively high concentrations in female ovarian tissues. FST acts as an antagonist to Activin, which is often elevated in human ovarian carcinoma, and thus may serve as a potential target for therapeutic intervention against ovarian cancer. The breast cancer susceptibility gene 1 (BRCA1) is a known tumor suppressor gene in human breast cancer; however its role in ovarian cancer is not well understood. We performed microarray analysis on human ovarian carcinoma cell line SKOV3 that stably overexpress wild-type BRCA1 and compared with the corresponding empty vector-transfected clones. We found that stable expression of BRCA1 not only stimulates FST secretion but also simultaneously inhibits Activin expression. To determine the physiological importance of this phenomenon, we further investigated the effect of cellular BRCA1 on the FST secretion in immortalized ovarian surface epithelial (IOSE) cells derived from either normal human ovaries or ovaries of an ovarian cancer patient carrying a mutation in BRCA1 gene. Knock-down of BRCA1 in normal IOSE cells demonstrates down-regulation of FST secretion along with the simultaneous up-regulation of Activin expression. Furthermore, knock-down of FST in IOSE cell lines as well as SKOV3 cell line showed significantly reduced cell proliferation and decreased cell migration when compared with the respective controls. Thus, these findings suggest a novel function for BRCA1 as a regulator of FST expression and function in human ovarian cells.