BIRC2 and neuroblastoma: In contrast to neuroblastoma cells, normal tissue-derived HS5 cells treated with A4 or B3 showed minimal change in XIAP expression with c-IAP1 remaining intact (Fig. 2B) and minimal apoptosis observed (Fig. 2B), possibly due to lower expression and lesser dependency on endogenous XIAP, and thus, higher tolerability toward A4 and B3.