MicroRNAs (miRNAs) are emerging as a class of small regulatory RNAs whose alterations are implicated in the initiation and progression of human cancers. Our study showed that miR-25 was highly expressed both in clinical ovarian cancer samples and cell lines. Down-regulation of miR-25 in ovarian cancer cells induced apoptosis whereas overexpression of miR-25 enhanced cell proliferation. The effects of miR-25 abrogation were partly mediated by the intrinsic apoptosis pathway. Many pro-apoptotic proteins such as Bim, Bax and caspase-3 were up-regulated after transfection. Furthermore, luciferase assays demonstrated that Bim was the direct target of miR-25. Introducing Bim cDNA without 3'UTR abrogated miR-25-induced cell survival. Finally, there was an inverse relationship between Bim and miR-25 expression in ovarian cancer tissues. Taken together, these data indicate that miR-25 directly regulates apoptosis by targeting Bim in ovarian cancer and that miR-25 could be a potential therapeutic target for ovarian cancer intervention.

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