MLH1 and colorectal cancer: To examine whether the mismatch repair (MMR) status of colorectal cancer cells affects sensitivity to trifluridine/tipiracil, a study used the MMR deficient cell line HCT116, which is defective for the mismatch repair protein MLH1, and a derivative cell line, HCT116 + ch3, with restoration of MLH1 expression [32].