XIAP inhibitor 1396-12 activates effector caspases. XIAP inhibitor 1396-12 activates effector caspases as an early event: Jurkat (A), K562 (B), and primary AML (C) leukemic cells (6 × 105/mL) were treated with the XIAP inhibitor 1396-12 (10 μM) for increasing periods of time. As controls, Jurkat cells were treated with CH-11 anti-Fas antibody (100 ng/mL; D) or staurosporine (STS; E) for increasing periods of time. After treatment, the mean percentage plus or minus SD of cells above control with active caspase 3 (▵), caspase 8 (□), and caspase 9 (⋄) was determined. Inhibition of effector caspases blocks XIAP inhibitor-induced apoptosis: Jurkat (F), K562 (G), and primary AML leukemic cells (H) (6 × 105/mL) were treated with the XIAP inhibitor 1396-12 (10 μM) for 12 hours with or without the pan-caspase inhibitor z-VAD, the preferential effector caspase inhibitor DEVD, the preferential caspase 8 inhibitor IETD, or the preferential caspase 9 inhibitor LEHD. After treatment, apoptosis was measured by annexin V staining. The mean percentage plus or minus SD of apoptotic cells above control is shown.
