ERCC2 and xeroderma pigmentosum: Polymorphisms of several key NER genes have previously been reported to alter the GC risk, including xeroderma pigmentosum, complementation group A (XPA) and xeroderma pigmentosum, complementation group C (XPC) in the damage recognition step, excision repair cross-complementation group 2 (ERCC2) in the damage unwinding step, and ERCC1, ERCC4, and ERCC5 in the damage incision step [13].