ARID1A and neoplasm: We found that in response to cisplatin, a platinum salt drug that causes replication forkstress43, HCT116 ARID1A−/− and tumour cell lines with endogenous ARID1A mutations exhibited similar protein expression of ATR to ARID1A wild-type cells and clear ATR p.T1989 autophosphorylation (Supplementary Fig. 1A,B).