MiR-182 overexpression in tumourigenesis of high-grade serous ovarian carcinoma

Molecular pathogenesis of high‐grade serous ovarian carcinoma (HG‐SOC) is poorly understood. Recent recognition of HG‐SOC precursor lesions, defined as serous tubal intraepithelial carcinoma (STIC) in fimbria, provides a new venue for the study of early genetic changes in HG‐SOC. Using microRNA profiling analysis, we found that miR‐182 expression was significantly higher in STIC than in matched normal Fallopian tube. Further study revealed that miR‐182 was significantly overexpressed in most HG‐SOC cases. To test whether miR‐182 plays a major role in early tumourigenesis of HG‐SOC, we overexpressed miR‐182 in immortalized ovarian surface, Fallopian tube secretory cells and malignant ovarian cell lines, and found that miR‐182 overexpression resulted in increased tumour transformation in vitro, and enhanced tumour invasiveness in vitro and metastasis in vivo. Mechanistically, we demonstrated that the oncogenic properties of miR‐182 in ovarian cancer were mediated in part by its impaired repair of DNA double‐strand breaks and negative regulation of breast cancer 1 (BRCA1) and metastasis suppressor 1 (MTSS1) expression as well as its positive regulation of the oncogene high‐mobility group AT‐hook 2 (HMGA2). Our findings suggest that miR‐182 dysregulation confers powerful oncogenic potential in the tumourigenesis of HG‐SOC. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.