XIAP inhibitors trigger apoptosis in acute leukemia cells. (A) Protein expression of XIAP, cIAP1, cIAP2, survivin, livin, Smac, Omi, and β-actin was assessed in acute leukemia cell lines by Western blotting. EHEB CLL cells were used as positive control for cIAP2 expression. (B) Acute leukemia cell lines were left untreated (□) or were treated for 48 hours with indicated concentrations of XIAP inhibitors, control compound, or DMSO. Apoptosis was determined by forwardside scatter analysis and flow cytometry. Mean and SD of 3 experiments each performed in triplicate are shown. For statistical analysis, t test was performed comparing XIAP inhibitors to control compound. #P < .05; *P < .01.