Background: Epithelial ovarian cancer is the 5th leading cause of cancer death in women. Our objective was to identify key genetic events important for the pathogenesis of this lethal disease. Methods: Levels of microRNA (miRNA) expression were examined in specimens of primary papillary serous carcinomas, normal ovary and distal fallopian tube using Next Generation Sequencing and a custom expression array. Chromosomal gains and losses were also examined by CGH. SYBR Green reagents were used to measure relative expression of target gene expression by quantitative real-time PCR. Functional impact of altered miRNA expression was tested using standard MTT and Caspase 3/7 assays to measure proliferation and apoptosis (Promega). Key outcome demographics were coded and correlated with miRNA and gene expression by Kaplan-Meier analysis. Results: A total of 140 miRNAs were differentially expressed when papillary serous ovarian cancers were compared to either fimbrae of normal fallopian or normal ovary. Of these, 36 miRNAs were found to correlate with either overall survival, disease free interval (DFI) or platinum sensitivity. Nineteen (19) of these clinically significant miRNAs mapped to single primate-specific genomic locus located at 19q13.41. This locus spanned 125 Kb of non-coding DNA and encoded a total of 44 miRNAs, most all of which showed significant copy number variation in papillary serous ovarian cancers (n = 178) and showed copy losses in the majority of tumors. Using established algorithms for target prediction, we found that this miRNA cluster collectively targeted more than 2800 distinct genes. Key loci included gene products implicated in the epithelial-to-mesenchymal transition (Snail, Slug) as well as both the G1-S and G2-M cell cycle checkpoints (MYCN and Wee1). Transfection of established ovarian cancer cell lines with individual 19q13.41 miRNAs significantly reduced expression of Snail, Slug, Wee1, resulting in altered proliferation and apoptosis. Conclusions: Altered expression of 19q13.41 cluster miRNAs correlate with significant clinical outcomes for women with papillary serous ovarian cancers. These miRNAs appear to play a key role in regulating the expression of gene products critical for the ongoing proliferation and metastasis of ovarian cancer. Future work will focus on dissecting the role of individual 19q13.41 miRNAs in ovarian and other cancers as well as validating the novel nanoparticle-based strategies we have developed for therapeutic miRNA delivery. Supported by NIH TCGA and the Ovarian Cancer Research Foundation (OCRF)

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 2029.