Effect of PUMA-specific siRNA on the protein expression levels of Bax and Bcl-2 in HepG2 cells. (A) Representative western blot showing the protein expression of PUMA, Bax and Bcl-2. (B) Relative protein expression levels of PUMA, Bax and Bcl-2, as assessed by the gray values. The PUMA antibody also cross-reacted with an 18 kDa band of unknown origin. Expression levels were normalized against the value obtained for β-actin protein expression. Data are expressed as the mean ± standard deviation (n=3). *P<0.05, vs. control group; #P<0.05, vs. si-PUMA group. PUMA, p53 upregulated modulator of apoptosis; Bcl-2, B-cell lymphoma 2; Bax, Bcl-2-associated X protein; Tau, taurine; IOD, integrated optical density; NC, negative control; si, small interfering.