[miR-455 Inhibits HepG2 Cell Proliferation and Promotes Apoptosis by Targeting RhoC]

Hepatocellular carcinoma (HCC) is a common malignancy worldwide with poor prognosis and high mortality. The aberrant expression or alteration of microRNAs (miRNAs) contributes to the development and progression of cancer. Studies have shown that miR-455 plays a regulatory role in the development of HCC. Therefore, in the present study, the role of miR-455 was analyzed in HepG2 cells proliferation and apoptosis using MTT and flow cytometry methods. Binding sites were predicted by bioinformatics and luciferase assay was used to verify the target relationship between miR-455 and RhoC-encoding gene RHOC. After that, the effects of miR-455 on RHOC and its product RhoC, were explored by qPCR and Western blotting. As PTEN is a key tumor suppressor gene in HCC, and Bcl-2 and Caspase 3 are important indication of apoptosis, expression levels of PTEN, Bcl2 and Caspase 3 proteins were determined in cells overexpressing RhoC. We show that miR-455 promotes HepG2 cells apoptosis and inhibits proliferation. Bioinformatics analysis and luciferase assay indicate that specific recognition sites for miR-455 are within the RhoC 3'-UTR. Luciferase activity was significantly lower in the cells co-transfected with miR-455 mimics and RhoC-WT (p < 0.01) as compared to that in control cells, pointing that RHOC gene is, indeed, targeted by miR-455. RHOC mRNA was significantly reduced after miR-455 transfection in HepG2 cells. In addition, we show that RhoC could activate the HCC cells proliferation ability and inhibit apoptosis rate (p < 0.01), and decrease expression of PTEN and Caspase 3 (p < 0.01), while upregulating levels of Bcl2. In conclusion, our study indicates that miR-455 plays a suppressive role in HCC development by targeting RhoC-encoding mRNA.