That ATR could be involved in p53 induction by fludarabine or cladribine was corroborated by experiments performed in the CLL cell line EHEB, in which depletion of ATR by siRNA paralleled the inhibitory effect of VE-821 on p53 phosphorylation and accumulation (Supplementary Figure 2). The gene discussed is TP53; the disease is B-cell chronic lymphocytic leukemia.