ATM and B-cell chronic lymphocytic leukemia: The RT-MLPA assay was performed on all (n=30) samples from the training cohort and showed upregulation of cluster I genes following ionizing irradiation (IR) in WT samples and impaired upregulation in TP53/ATM-defective CLL samples following IR, confirming earlier results from Stankovic et al.9 Additionally, most cluster II-IV genes discriminated between TP53- and ATM-defective CLL samples in their regulation following IR.