Abstract 3875: NUAK2, a gene with a putative driver mutation in ovarian cancer, is regulated through the murine estrus cycle and loss is associated with worse outcome in ovarian cancer

Molecular events leading to ovarian cancer are poorly understood but ovulatory hormones and a high number of lifetime ovulations increase risk. The most common histotype, serous ovarian cancer, is thought to arise from ovarian surface epithelium or inclusion cysts although recent evidence has implicated fallopian tube epithelium and other Müllerian tissues as potential sites of origin. The aim of this study was to identify genes that may play a critical role in the pathogenesis of ovarian cancer from candidates that we have previously identified as regulated during the murine estrus cycle in microdissected ovarian surface epithelium and matched oviduct.

We examined estrus regulated gene profiles in normal mouse ovarian and oviduct epithelium for genes (i) differentially expressed in ovarian cancer compared to normal controls; (ii) with copy number aberration in ovarian cancer; and (iii) with reported mutation in solid tumors. We identified over 350 genes that are regulated in the normal mouse ovarian epithelium during the estrus cycle and dysregulated in cancer including four genes found to be mutated in various tumour types (Catalogue Of Somatic Mutations In Cancer) and around 50 genes that have copy number aberration in ovarian cancer (The Cancer Genome Atlas). A similar number of genes were regulated in the normal mouse oviduct epithelium during the estrus cycle and dysregulated in ovarian cancer including six that are mutated in various tumor types and around 35 with copy number aberration in ovarian cancer. Interestingly, there was very little similarity between the ovarian and oviduct epithelium gene lists with only 19 genes in common, however, pathway analysis revealed over-representation of genes involved in cell cycle, particularly the spindle assembly checkpoint, and extracellular matrix/cell adhesion in both lists.

We identified NUAK family, SNF1-like kinase, 2 (NUAK2) as upregulated in ovarian epithelium during the proestrus phase of the murine estrus cycle, upregulated in ovarian cancer and with a candidate driver mutation for breast and ovarian cancer. Expression of NUAK2 was examined by immunohistochemistry in human ovary (n=10), fallopian tube (n=9), and ovarian cancer (n=119). This showed that NUAK2 expression was highest in fallopian tube, intermediate in OSE and lost in ∼20% of ovarian cancer cases. Kaplan-Meier curves with log-rank test revealed reduced expression of NUAK2 was significantly associated with reduced overall survival in ovarian cancer (p<0.04).

Future work involves functional analysis of key genes, including NUAK2, in human cell lines. Defining genes that are activated in normal ovarian and oviduct epithelial cells in the course of ovulation that are also dysregulated in cancer has identified a number of molecular pathways and novel candidate genes that may contribute to the development of ovarian cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3875. doi:10.1158/1538-7445.AM2011-3875

Comparison of expression profiles in ovarian epithelium in vivo and ovarian cancer identifies novel candidate genes involved in disease pathogenesis

Molecular events leading to epithelial ovarian cancer are poorly understood but ovulatory hormones and a high number of life-time ovulations with concomitant proliferation, apoptosis, and inflammation, increases risk. We identified genes that are regulated during the estrous cycle in murine ovarian surface epithelium and analysed these profiles to identify genes dysregulated in human ovarian cancer, using publically available datasets. We identified 338 genes that are regulated in murine ovarian surface epithelium during the estrous cycle and dysregulated in ovarian cancer. Six of seven candidates selected for immunohistochemical validation were expressed in serous ovarian cancer, inclusion cysts, ovarian surface epithelium and in fallopian tube epithelium. Most were overexpressed in ovarian cancer compared with ovarian surface epithelium and/or inclusion cysts (EpCAM, EZH2, BIRC5) although BIRC5 and EZH2 were expressed as highly in fallopian tube epithelium as in ovarian cancer. We prioritised the 338 genes for those likely to be important for ovarian cancer development by in silico analyses of copy number aberration and mutation using publically available datasets and identified genes with established roles in ovarian cancer as well as novel genes for which we have evidence for involvement in ovarian cancer. Chromosome segregation emerged as an important process in which genes from our list of 338 were over-represented including two (BUB1, NCAPD2) for which there is evidence of amplification and mutation. NUAK2, upregulated in ovarian surface epithelium in proestrus and predicted to have a driver mutation in ovarian cancer, was examined in a larger cohort of serous ovarian cancer where patients with lower NUAK2 expression had shorter overall survival. In conclusion, defining genes that are activated in normal epithelium in the course of ovulation that are also dysregulated in cancer has identified a number of pathways and novel candidate genes that may contribute to the development of ovarian cancer.

Evaluation of candidate stromal epithelial cross-talk genes identifies association between risk of serous ovarian cancer and TERT, a cancer susceptibility "hot-spot"

We hypothesized that variants in genes expressed as a consequence of interactions between ovarian cancer cells and the host micro-environment could contribute to cancer susceptibility. We therefore used a two-stage approach to evaluate common single nucleotide polymorphisms (SNPs) in 173 genes involved in stromal epithelial interactions in the Ovarian Cancer Association Consortium (OCAC). In the discovery stage, cases with epithelial ovarian cancer (n=675) and controls (n=1,162) were genotyped at 1,536 SNPs using an Illumina GoldenGate assay. Based on Positive Predictive Value estimates, three SNPs-PODXL rs1013368, ITGA6 rs13027811, and MMP3 rs522616-were selected for replication using TaqMan genotyping in up to 3,059 serous invasive cases and 8,905 controls from 16 OCAC case-control studies. An additional 18 SNPs with Pper-allele<0.05 in the discovery stage were selected for replication in a subset of five OCAC studies (n=1,233 serous invasive cases; n=3,364 controls). The discovery stage associations in PODXL, ITGA6, and MMP3 were attenuated in the larger replication set (adj. Pper-allele>or=0.5). However genotypes at TERT rs7726159 were associated with ovarian cancer risk in the smaller, five-study replication study (Pper-allele=0.03). Combined analysis of the discovery and replication sets for this TERT SNP showed an increased risk of serous ovarian cancer among non-Hispanic whites [adj. ORper-allele 1.14 (1.04-1.24) p=0.003]. Our study adds to the growing evidence that, like the 8q24 locus, the telomerase reverse transcriptase locus at 5p15.33, is a general cancer susceptibility locus.

Abstract 4727: TERT SNPs and ovarian cancer risk

There is increasing evidence that neighboring stromal cells are not uninvolved bystanders in the pathway to cancer. We hypothesized that SNPs in genes expressed as a consequence of interactions between ovarian cancer cells and the host micro-environment could contribute to ovarian cancer susceptibility. We therefore used a two-stage approach to comprehensively evaluate common single nucleotide polymorphisms (SNPs) in the Ovarian Cancer Association Consortium (OCAC) for 173 genes involved in stromal-epithelial interactions. Cases with epithelial ovarian cancer (n=675) and controls (n=1,162) were genotyped at 1536 SNPs using an Illumina GoldenGate™ BeadArray array. Logistic regression was used to estimate odds ratios (ORs) and adjust for potential confounders. Based on Positive Predictive Value estimates, three SNPs - PODXL rs1013368, ITGA6 rs13027811 and MMP3 rs522616 - were selected for replication using TaqMan genotyping in 3,734 serous invasive cases and 10,067 controls from 16 OCAC case-control studies. An additional 18 SNPs with Pper-allele &lt;0.05 in the test set, and which fitted into an iPLEX design, were selected for replication by a subset of five OCAC studies (n=1771 serous invasive cases; n=4022 controls). The associations observed in the test set for the PODXL, ITGA6 and MMP3 SNPs were completely attenuated in the replication set (adj. Pper-allele ≥0.5). However, TERT rs7726159 showed evidence of a log additive association with ovarian cancer risk in the replication study (Pper-allele =0.03). Combined analysis of the test and replication sets for this SNP showed a significant association with risk of serous ovarian cancer among non-Hispanic whites [adj. ORper-allele 1.14 (1.04 - 1.24) p = 0.003]. A stronger association was observed for serous invasive cases when data for all ethnicities were included [adj. ORper-allele 1.18 (1.09 - 1.28) p = 2.46 × 10−5]. Stratification by histological subtype and malignant potential showed that TERT rs7726159 was also associated with risk of serous borderline tumors, but not with any other subtypes. Although TERT variants have not been previously reported to be associated with ovarian cancer, multiple genome-wide association studies have reported associations with this locus and risk of glioma, basal cell carcinoma, and several cancer types that are known to originate in the epithelium, including lung, bladder, prostate and cervical cancer. Further analysis of this locus is necessary to definitively identify the causal SNP(s). Our study adds to the growing evidence that, as well as 8q24, the TERT locus at 5p15.33, is a general cancer susceptibility locus.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4727.

Global gene expression profiles of ovarian surface epithelial cells in vivo

Epithelial ovarian cancer, the leading cause of death from gynecological malignancy in Western countries, is thought to arise from the ovarian surface epithelium (OSE). It has been postulated that the constant rounds of proliferation and repair following ovulation contributes to neoplastic transformation. However, there is little information on the genes and pathways which are involved in the normal functions of the ovarian epithelium, in particular genes that are hormone responsive and those central to functions such as proliferation and apoptosis during ovulation. We used laser microdissection and cDNA microarrays to profile gene expression specifically in mouse ovarian epithelial cells, first compared with other ovarian cells, and secondly between ovarian epithelium collected at different physiological stages. We identified over 1000 transcripts that were consistently more highly expressed in the ovarian epithelium compared with remaining ovarian cell types, including genes involved in cell growth, transcription, and cell adhesion. At the various physiological stages examined, the highest number of regulated genes was found during the estrous cycle, specifically on the evening of proestrus, coincident with the ovulatory surge of hormones and just prior to ovulation. The expression of several selected genes, identified by the microarray analysis, including Villin 2, Keratin 8, Arginine-rich mutated in epithelial tumors, and Tumor-associated calcium signal transducer 1, was validated by independent methods. The identification of genes expressed and regulated in the OSE, and characterization of the pathways involved, will contribute to a more detailed understanding of the ovarian epithelium transcriptome and ultimately lead to a better understanding of the aberrations leading to malignant transformation in the ovarian epithelium.

Overlapping and distinct expression of progesterone receptors A and B in mouse uterus and mammary gland during the estrous cycle

In rodents, progesterone receptors (PRs) A and B have different and often nonoverlapping roles, and this study asked whether different activities of the PR proteins in mouse are related to differences in their expression in reproductive tissues. The individual expression of PRA and PRB was determined immunohistochemically in mammary gland and uterus during the estrous cycle or in response to endocrine manipulation. In the mammary gland, PRA and PRB were colocated in PR+ epithelial cells, with little change during the estrous cycle. In the uterus, PRA was not detected in luminal epithelium at any stage of the cycle, and PR+ luminal cells expressed only PRB. In the stroma and myometrium, PRA and PRB levels fluctuated with cyclical systemic hormone exposure. Observation of functional end points suggested that augmented stromal and/or myometrial PRA in proestrus inhibited estrogen receptor expression and epithelial proliferation. Colocation of PRA and PRB was hormonally regulated, and ovariectomy did not reproduce the expression of PRA and PRB in the uterus during the estrous cycle. Whereas PRB was the only PR in the luminal epithelium in cycling mice, ovariectomy restored PRA expression, resulting in PRA-PRB colocation. In stroma and myometrium, PRA and PRB colocated in PR+ cells, but ovariectomy reduced PRA levels more than PRB, resulting in PRB-only-expressing cells. This study has shown that nonoverlapping PRA and PRB expression in the uterus, in particular the lack of PRA, and expression of PRB only in the luminal epithelium throughout the estrous cycle, is likely to contribute to the distinct roles of PRA and PRB in the adult mouse.

Focal subnuclear distribution of progesterone receptor is ligand dependent and associated with transcriptional activity

The progesterone receptor (PR) is a critical mediator of progesterone action in the female reproductive system. Expressed in the human as two proteins, PRA and PRB, the receptor is a ligand-activated nuclear transcription factor that regulates transcription by interaction with protein cofactors and binding to specific response elements in target genes. We previously reported that PR was located in discrete subnuclear foci in human endometrium. In this study, we investigated the role of ligand in the formation of PR foci and their association with transcriptional activity. PR foci were detected in mouse uterus and normal human breast tissues and were more abundant when circulating progesterone was high. In human malignant tissues, PR foci were aberrant: foci were larger in endometrial cancers than in normal endometrium, and in breast cancers hormone-dependence was decreased. Chromatin disruption also increased foci size and decreased ligand dependence, suggesting that altered nuclear architecture may contribute to the aberrant PR foci observed in endometrial and breast cancers. In breast cancer cells, movement of PR into foci required exposure to ligand and was blocked by transcriptional inhibitors and by prolonged inhibition of proteasomal degradation. Foci contained PR dimers, and fluorescence resonance energy transfer demonstrated that PR foci contained the highest concentration of receptor dimers in the nucleus. PR in foci colocalized with transcription factors and nascent RNA transcripts only in the presence of ligand, and inhibition of coactivator recruitment inhibited PR foci formation. The demonstration that focal distribution of PR within the nucleus is associated with transcription suggests a link between the subnuclear distribution of PR and its transcriptional activity that is likely to be important for normal cellular function of PR.

Expression of progesterone receptors A and B in the mouse ovary during the estrous cycle

Progesterone plays a central role in the regulation of ovarian function. The progesterone receptor (PR) has been shown to be essential for ovulation because mice lacking PR fail to ovulate and are infertile. PR is expressed as two isoforms, PRA and PRB, which have been shown to have different functional activities. In this study, we investigated the cellular distribution of PRA and PRB in the ovaries and oviducts of cycling mice using immunohistochemistry with isoform-specific monoclonal antibodies. In the ovary, on the evening of proestrus before ovulation, both the granulosa and theca cells of the preovulatory follicles expressed both PR isoforms. PRA and PRB staining was also observed in the theca cells of preantral and antral follicles, whereas only PRB was observed in the granulosa cells of primary, preantral, and antral follicles and in the corpus luteum. In the oviduct, PRA was the predominant isoform observed, expressed in both the epithelial and stromal cells, whereas PRB was only detected in the epithelial cells. The differences in PRA and PRB localization in the ovary and oviduct may reflect diverse functions for PRA and PRB in reproductive tissues and may have important implications in understanding the mechanisms of progesterone action.