The effects of microRNA-7 on proliferation and invasion of hepatocellular carcinoma HepG2 cells

Abstract

Objective: To investigate the effects of overexpression of microRNA-7 (miR-7) on the proliferation and invasion of HepG2 cells and the underlying mechanism in vitro. Methods: The relative expression levels of miR-7 and Raf1 in hepatocellular carcinoma (HCC) tissues and adjacent normal tissues (ANT) were detected by quantitative real time-PCR (qRT-PCR). The relationship between the expression of miR-7 and the characteristics of HCC patients was analyzed. Cells were divided into blank control group, negative control (NC) group and miR-7 mimics transfected group, miR-7 mimics and NC were transfected into HepG2 cells by Lipofectamine™2000. The relative expression of miR-7 was detected by qRT-PCR. The proliferation ability of HepG2 cells was detected by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay. The invasion of HepG2 cells was detected by Transwell assay. The target genes of miR-7 were predicted by TargetScan and the binding effect of miR-7 on the 3'UTR of Raf1 was verified by dual luciferase reporter assay.The expressions of Raf1 protein in hepatocellular carcinoma tissues, normal tissues and miR-7 mimics transfected HepG2 cells was detected by Western blot. The correlation of the levels of miR-7 and Raf1 mRNA was determined by Pearson correlation analysis. Results: The relative expression level of miR-7 in HCC was 0.49±0.02, significantly lower than in ANT (1.21±0.05, P<0.01). The level of miR-7 was significantly correlated the tumor volume, metastasis and prognosis of HCC patients (P<0.05). The relative expression level of miR-7 in miR-7 mimics transfected HepG2 group was 12.67±0.40, significantly higher than that in blank group (P<0.01). Compared with the blank group, the A value and invasion ability of miR-7 mimics transfected group were significantly down-regulated at 48 hours and 72 hours after transfection (P<0.01). Compared with miR-7 NC group, the luciferase activity of wild-type Raf1 reporter gene in miR-7 mimics transfected group was significantly reduced (P<0.01). The relative expression of Raf1 protein in HCC was 3.15±0.10, significant higher than in ANT (0.53±0.03, P<0.01). The relative expression of Raf1 protein in miR-7 mimics transfected group was 0.24±0.01, significantly lower than in miR-7 NC group (0.98±0.02, P<0.01). Furthermore, an negative correlation was observed between the levels of miR-7 and Raf1 in HCC tissues (P<0.05). Conclusions: The expression of miR-7 in HCC is significantly decreased and inversely correlated with poor survival of HCC patients. Overexpression of miR-7 can inhibit the proliferation and invasion ability of hepatocellular carcinoma cells HepG2 by downregulating Raf1 in vitro.