MRC1 and colorectal carcinoma: We also studied the effect of MSH3 knockdown in an MMR-deficient background by using the SW48 CRC cell line that is deficient in MLH1. In SW48 cells, the enhanced cytotoxic effects of SN-38 and oxaliplatin were maintained after MSH3 knockdown whereas no difference was seen for 5-FU compared to results in HCT116+3+5 cells with MLH1 knockdown (Fig. 6D–F).