Figure 4 : Down-regulation of X-linked inhibitor of apoptosis protein (XIAP) contributes to sensitization effect of luteolin on FasL-induced apoptosis. (A) HepG2 cells were pretreated with 30μM luteolin for 2h, followed by treatment with FasL (60ng/ml) for 3, 6, 12, 24 h. Cells lysates were detected by immunoblot analysis using indicated antibodies. (B) HepG2 cells were pretreated with 10μM, 20μM, 30μM luteolin for 2h, then treated with 60ng/ml FasL for another 24 h. Cells lysates were detected by immunoblot analysis using indicated antibodies. (C) HepG2 cells were pretreated with Wortmannin (20μM) for 30 minutes, followed by treatment with the combination of luteolin (30μM × 24 h) and FasL (60ng/ml × 22 h). Cells lysates were collected for detection of XIAP, p-Akt308 and total Akt by Western blot. (D) HepG2 cells were transiently transfected with wt-Akt, after 24 hours, the cells were treated with luteolin (30μM × 24h) followed by FasL (60ng/ml × 22h). The cells were collected for analysis by western blot using Akt, p-Akt, XIAP antibody. The content of β-actin was used as a loading control.