Abstract 133:MiR-182overexpression and ovarian high grade serous carcinoma

OBJECTIVES: BRCA1/BRCA2 mutations are hallmarks high grade papillary serous carcinoma (H-PSC). This correlation is due to the fact that approximately 40-50% of H-PSC have altered expression of BRCA1/BRCA2 (including germline and somatic mutations and epigenetic modifications). Furthermore, women with germline mutations of BRCA1/2 have a 30%-70% chance of developing H-PSC by the age of 70. If inactivation of BRCA1/2 is critical in the early tumorigenesis of H-PSC, there must be other mechanisms whereby BRCA1/2 is downregulated in the remaining 50% of H-PSC. Recent findings of miR-182-mediated repression of BRCA1 expression and significant overexpression of miR-182 in H-PSC suggest that miR-182 may play an important role in the tumorigenesis of H-PSC through its negative regulation of BRCA1. DESIGNS: To explore the role of miR-182 through the negative regulation of BRCA1 in the early stages of H-PSC tumorigenesis, we conducted in vitro molecular and cellular analyses of miR-182 in human fallopian tube secretory (FTSE) and ovarian surface epithelia (OSE) cell lines. We 1) established stable cell lines with stable miR-182 overexpression; 2) examined the oncogenic properties of miR-182 by anchorage-independent growth, cell proliferation and invasion in vitro; 3) investigated DNA damage response in cells with miR-182 expression after ionizing radiation (IR); 4) examined and characterized several predicted target genes of miR-182, including BRCA1, HMGA2 and MTSS1; 5) studied tumor growth and metastasis in vivo (in nude mice) with and without miR-182 overexpression. RESULTS: 1) Introducing miR-182 overexpression in normal immortalized cell lines (both FTSE and OSE) resulted in tumor transformation and significantly enhanced cell invasion in vitro. 2) FTSE and OSE cell lines with miR-182 overexpression had impaired repair of DNA double-strand breaks when treated with low doses of IR. 3) We further demonstrated that the oncogenic properties of miR-182 in ovarian cancer were mediated by its negative regulation of breast cancer 1 (BRCA1) and metastasis suppressor 1 (MTSS1) expression and its positive regulation of oncogene high-mobility group AT-hook 2 (HMGA2). Knockdown of miR-182 expression in ovarian cancer cell lines (SKOV3, and HEY) could therefore partially restore BRCA1 and MTSS1 expression and reduce aggressive tumor growth in vitro. Ovarian cancer cell line SKOV3 with miR-182 overexpression enhances lung metastasis in vivo. CONCLUSION: MiR-182 confers a powerful oncogenic potential in normal and malignant ovarian/fallopian tube cell lines through its negative regulation of several critical target genes in H-PSC, including BRCA1, MTSS1 and HMGA2. Therefore, MiR-182 likely plays a significant role in the early tumorigenesis of H-PSC. Our findings provide a novel target and a new potential therapeutic modality in treating H-PSC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 133. doi:1538-7445.AM2012-133