Estrogen regulated microRNAs in mouse ovarian cancer cells.

In a mouse model of ovarian cancer, we have established that prolonged exposure to 17β-estradiol (E2) accelerates tumour onset and increases the incidence of morphologically dysplastic ovarian surface epithelium (OSE). OSE cell proliferation and morphology are tightly regulated by the asymmetrical distribution of polarity proteins that provide positional cues for surface localization and growth inhibition. We hypothesized that E2 causes OSE dysplasia by inhibiting a tumour suppressor gene called Disabled-2 (Dab2). Dab2 is critical in mediating the polarized distribution of cell surface proteins and is highly expressed in normal OSE, but is absent in the majority of ovarian cancers. In this study, Dab2 is shown to be suppressed by E2 and we investigated the possibility that this occurs through E2 up-regulation of microRNAs. microRNA microarray analysis comparing control vs. E2 treated mouse ovarian cancer cells (MASE) was used to identify candidate miRNAs that have a seeding sequence capable of targeting the 3-prime untranslated region (3’UTR) of both human and mouse Dab2 transcript. MASE ovarian cancer cells were isolated from ascites fluid of estrogen treated tgCAG-TAg mice. Once cells were established in culture, they were treated with 100nM E2 for 24H. An equivalent volume of 100% EtOH (vehicle) was added to control plates for a final concentration of 0.0002% EtOH.