MLH1 and colorectal cancer: In a 1998 study looking at aspirin and hereditary nonpolyposis, it was shown that microsatellite instability in colorectal cancer cells in HNPCC (specifically looking at cells deficient for a subset of the human mismatch repair-MMR genes of hMLH1, hMSH2, and hMSH6) was thought to be markedly reduced during exposure to aspirin (Rüschoff et al., 1998).