Protein levels of XIAP, survivin and β-actin following treatment with exogenous TGF-β1 or TGF-β1 siRNA in HepG2 cells. (A) Representative protein bands from the western blotting. (B) Protein band quantification. 1, control group; 2, 24 h exogenous TGF-β1 group; 3, 48 h exogenous TGF-β1 group; 4, 72 h exogenous TGF-β1 group; 5, 72 h TGF-β1-knockdown group; 6, 96 h TGF-β1-knockdown group. *P<0.05 vs. the control group. XIAP, X-linked inhibitor of apoptosis protein; TGF-β1, transforming growth factor-β-1; siRNA, small interfering RNA.