ATM and cancer: Using CRISPR-based cell-growth competition assays (44,53), we provisionally validated both genes alongside various other resistance-gene hits from the Atm WT screens that commonly acquire missense mutations and/or reduced expression in cancer (Prkar1a (54–56), Flcn (57,58), E2f8, Ccnc (59) and Cdk8 (60)) (Figure 2A).