FIGURE 4.

cIAP1, cIAP2, and XIAP cooperatively protect against IL-1β-induced cancer cell death. SF295 (A), SNB75 (B), and U2OS (C), cells were transfected with siRNA targeting cIAP1, cIAP2, XIAP, or nontargeting siRNA as a control. 48 h after siRNA-mediated silencing, cells were treated with vehicle (black bars) or with 1 ng/ml IL-1β (white bars) for an additional 48 h. Cell viability was determined by Alamar Blue. The percentage viability relative to nontargeting siRNA and vehicle ± S.D. (n = 4) was plotted. D, cells were transfected with siRNA as in A–C for 48 h and harvested, and protein expression levels of cIAP1, cIAP2, and XIAP were analyzed by Western immunoblotting. β-Actin was used as a loading control. The combined silencing of cIAP1, cIAP2, and XIAP by siRNA results in the highest sensitization to IL-1β-mediated cancer cell death.