ATR and leukemia: In vitro sensitivity does not correlate with leukemia cell type (B-ALL vs T-ALL), TP53 mutation status (BV-173, SUPB-15, NALM-6, and NALM-19 cells were p53 wild-type, whereas REH, MOLT-4, RPMI-8402, and CEM cells were p53 mutated) (Fig. 2a), and with baseline levels of Chk1/2 and ATR/ATM phosphorylation, indicative of intrinsic genetic stress (Fig. 2b).