APT1 and APT2 control CD95-mediated apoptosis. PB treatment significantly enhanced apoptosis mediated through anti-CD95 (CH11) in CLL cells after 24 hours (n = 14). Apoptosis of CLL cells was determined by Annexin V/7-AAD staining and subsequent flow cytometry. Apoptosis was also significantly increased after treatment of HeLa cells with PB and CD95 after 24 hours (n = 3). Survival of HeLa cells was determined by XTT assays (A). Specific siRNA knockdown of APT1 (n = 3) or APT2 (n = 5) for 48 hours was able to mimic the PB effect in CLL cells (B) and in HeLa cells (n = 3) (C). Knockdown efficiency was determined by western blotting (B-C). In addition, overexpression of miRNAs regulating APT1 and APT2 for 48 hours also led to increased apoptosis in HeLa cells (n = 4) (D). Means are given with their SEM. The statistical significance was determined using the Student t test. *P < .05, **P < .01, or ***P < .001 were considered significant.