XIAP and neuroblastoma: Tumors harvested from neuroblastoma PDXs after exposure to 10 mg/kg A4 at serial timepoints over 48 hours showed an eventual reduction of XIAP tissue expression and increased apoptosis indicated by PARP and caspase-3 cleavage, consistent with in vitro findings (Fig. 4A; Supplementary Fig. S6A and S6B).