Cotreatment with Smac-4 peptide enhanced Epo B– or Apo-2L/TRAIL–induced processing and activity of caspase-3 and down-regulation of the levels of XIAP, cIAP, and survivin.

Jurkat cells were treated with either 10 μM of control or Smac-4 peptide for 3 hours, followed by treatment with 10 nM Epo B or 2.5 ng/mL Apo-2L/TRAIL and/or the control or Smac-4 peptide for 24 hours. Following these treatments, Jurkat cells were treated with either a control peptide or 4–amino acid Smac peptide (10 μM for 3 hours), followed by treatment with Epo B (10 nM) (A) or Apo-2L/TRAIL (2.5 ng/mL) (B) for 24 hours. Following this, cell lysates were obtained from treated and untreated cells and immunoblot analysis of PARP, caspase-3, XIAP, or cIAP1 was performed; β-actin was used as a loading control.