The synergy of nutlin-3a and 1396-11 on apoptosis is mediated via p53 activation and XIAP inhibition. (A) Knockdown of p53 by shRNA blunts the synergy of nutlin-3a and 1396-11. OCI-AML3vec and OCI-AML3p53shRNA cells were treated with nutlin-3a, 1396-11, or both for 48 hours. p53 levels were determined at 24 hours by Western blot. N3a indicates nutlin-3a; Vec, OCI-AML3vec cells (solid lines); and p53KD, OCI-AML3p53shRNA cells (dashed lines). (B) Inhibition of XIAP by ASO sensitizes OCI-AML3 cells to nutlin-3a. OCI-AML3 cells were treated with XIAP ASO and control oligonucleotide (NSO; both 6 μg) by electroporation for 24 hours and then treated with nutlin-3a for an additional 24 hours. Inhibition of XIAP was confirmed by Western blot at 24 hours. (C) Inhibition of XIAP and MDM2 by their respective ASOs enhances apoptosis induction. OCI-AML3 cells were transfected with XIAP ASO (9 μg), MDM2 ASO (8 μg), or both, for 48 hours by electroporation. Apoptosis was assessed by annexin V (Ann V) staining in the presence of a vital dye.