MiR-135a functions as a tumor suppressor in epithelial ovarian cancer and regulates HOXA10 expression

The activation of homeobox A10 (HOXA10) has been proved to be an important event in epithelial ovarian carcinogenesis, yet its regulation in epithelial ovarian cancer (EOC) is still not fully understood. Here, we aimed to reveal the mechanism that a predicted target miRNA regulates HOXA10 expression and the association of its expression with progression of EOC. Here, by using computer-assisted algorithms from PicTar, TargetScan, and miRBase, we identified that the predicted target miRNA of HOXA10 was miR-135a. MiR-135a expression in EOC tissues and controls was measured with quantitative RT-PCR. The role of miR-135a and HOXA10 in the growth and survival of several EOC cell lines was determined with several in vitro approaches. We found that miR-135a expression was downregulated in an EOC patient cohort. Also, patients with low miR-135a expression had shorter overall survival and progression-free survival durations than those with high expression. Functional analysis of three EOC-derived cell lines (SKOV-3, HEY, and OVCAR-3) demonstrated that miR-135a directly regulated HOXA10 expression by targeting its 3'-UTR. Inhibition of HOXA10 expression with miR-135a mimics and HOXA10 siRNA consistently resulted in cell apoptosis with concomitant enhancement of caspase-3, increase of p53 expression and reduction of Bcl-2 expression, and also suppressed cell growth and adhesion. These findings suggest that ubiquitous loss of miR-135a expression is a critical mechanism for the overexpression of HOXA10 in EOC cells, which is implicated in epithelial ovarian carcinogenesis. Furthermore, miR-135a may be predictive of EOC prognosis.