Over-expression of miR-155 in human hepatoma cells. (A) qRT-PCR analysis of miR-155 levels in miR-155 gene-modified HepG2 (HepG2-miR155) cells and parental HepG2 cells. (B) 50 nM miR-155 mimics or control RNA (cnt RNA) were transfected into HepG2 cells. qRT-PCR analysis was performed 48 h after transfection. Data shown are means ± SD from at least three separate experiments. (*P < 0.05, **P < 0.01 by comparison with control cells).