Figure 3: RNA interference and plasmid-mediated overexpression of ABCG2 in SMMC-7721 cells. (a) RT-PCR analysis of ABCG2 mRNA in SMCC-7721 cells after transfection with siRNA or plasmid for 48 h. Normal SMMC-7721 cells were used as blank control. Scrambled siRNA was set as negative control. For overexpression, empty plasmid was transfected as negative control. (b), (c) Western blot analysis confirmed the efficiency of downregulation of ABCG2 by siRNA and upregulation by overexpression, respectively. β-Actin served as loading control. The optical density was quantified and normalized to β-Actin. ** , *** .