Interestingly, we observed that for expression of a different hotspot tumor-associated p53 mutant R175H in HCT116 p53−/− cells (Supplementary Figure 6A) the ATR inhibition had a modest effect in increasing the etoposide sensitivity, possibly indicating a p53 mutation-specific effect (compare HCT p53R273H in Figure 4C with HCT116 p53R175H in Supplementary Figure 6B). Here, TP53 is linked to neoplasm.