APEX1 and colorectal cancer: Therefore, the abnormal expression of APE1 gene may lead to the repair of defects in these lesions and give individuals the susceptibility to cancer.[33–38] Epidemiological studies have found that APE1 gene polymorphism is related to the risk of lung cancer, breast cancer, colorectal cancer and bladder cancer.[35,36] 18 SNPs were identified in APE1, including two functional SNPs rs1760944 in the promoter region and rs1130409 in the fifth exon.