Figure 7.

(A) XIAP expression was assessed by Western blotting of untransfected IMR-90 fibroblasts and IMR-90 fibroblasts transfected for 24 hours with 10 nM of a nontargeting (control) siRNA or a siRNA-targeting XIAP. The representative blot was stripped and probed for GAPDH. (B) Untransfected IMR-90 fibroblasts and IMR-90 fibroblasts transfected with the control or with XIAP siRNA were treated with or without Fas-Ab (250 ng/ml) with or without the Smac/Diablo mimetics SM164 (100 nM) or AT406 (1.0 μM) for 16 hours, and apoptosis was assessed using ELISA for detection of histone-associated DNA fragments. Data are indexed to the average of the untransfected Fas-Ab–treated cells to allow relative comparisons. Data shown are from five independent experiments with each condition measured in triplicate. *P < 0.01 compared with untransfected cells without treatment. ^#P < 0.01 compared with untransfected cells treated with Fas-Ab. Additional control conditions (Fas-Ab with cycloheximide, cycloheximide alone, SM164 alone, and AT406 alone) are shown in Figure E3. NS, not significantly different from untreated cells.