APEX1 and colorectal cancer: The joint effect of tobacco exposure and the MUTYH Gln324His showed a significant association with colorectal cancer risk in non-smokers (adjusted OR 4.08, 95%CI 1.22–13.58, p = 0.022) and the APEX1 Asp148Glu was significantly increased in smokers (adjusted OR 5.02, 95%CI 1.80–13.99, p = 0.002).