TP53 and colorectal carcinoma: To compare the impact of APC with that of p53 expression, since p53 is also mutated in several of the CRC lines analyzed, we knocked down wild type APC by siRNA in HCT116 cell lines wild-type or null for p53 and observed that APC depletion reversed the 5-FU-dependent induction of PARP cleavage in parental HCT116 cells similar to that observed in p53 null cells (Supplementary Fig. S2A).