TP53 and neuroblastoma: An important difference between UKF-NB-3rVCR10 and the other investigated neuroblastoma cell lines is that UKF-NB-3rVCR10 cells harbor a C135F p53 mutation.16, 17, 18 Indeed, YM155 induced a p53 response in UKF-NB-3 and UKF-NB-6 cells as indicated by increased cellular levels of p53 and p21, and apoptosis as indicated by poly(ADP-ribose) polymerase (PARP) cleavage (Figure 2a).