Apoptosis-sensitive and apoptosis-resistant ALL tumors exhibit comparable p53-dependent transcriptional responses to IR. Microarray analysis reveals comparable up-regulation IR of a set of p53-dependent genes (PCNA, IFFBP4, DDB2, BCL2, GADD45A, FAS MDM2, FDXR, BAX, TNFRSF10B, and BBC3) 8 hours following 5 Gy IR in 11 representative apoptosis-sensitive and 11 apoptosis-resistant ALLs. The error bars represent two times the standard deviation of the values.