MicroRNA-25 Exerts an Oncogenic Function by Regulating the Ubiquitin Ligase Fbxw7 in Hepatocellular Carcinoma

Background: MicroRNA (miRNA) expression abnormalities are implicated in tumor progression. Previous reports have indicated that microRNA-25 (miR-25) acts as a tumor suppressor or oncogene in diverse cancers. However, its molecular mechanisms in hepatocellular carcinoma (HCC) are still unclear. F-box and WD repeat domain 7 (Fbxw7) is a critical tumor suppressor and is one of the most important deregulated proteins of the ubiquitin–proteasome system in cancer. Our objective was to elucidate the role of miR-25 and Fbxw7 in HCC and to clarify the mechanism by which Fbxw7 is regulated. Methods: Fbxw7 expression was estimated in 210 fixed paraffin-embedded HCC samples by immunohistochemistry, and miR-25 expression was evaluated in 142 frozen HCC tissue samples by quantitative real-time PCR. Oncogenic functions of miR-25 and its role in the regulation of Fbxw7 expression were assayed in vitro. Results: miR-25 was overexpressed in HCC tissue compared with adjacent normal tissue and significantly correlated with a poorer prognosis. Moreover, it was inversely correlated with Fbxw7 expression in HCC tissues. Furthermore, miR-25 inhibition significantly reduced the proliferation, migration, and invasion of HCC cells in vitro. Conclusion: miR-25 may promote tumor progression in HCC patients by repression of Fbxw7 and could serve as a promising molecular target for HCC treatment.