Polymorphisms in the XPC gene affect urinary bladder cancer risk: a case-control study, meta-analyses and trial sequential analyses.

Compromised activity of the DNA repair enzymes may raise the risk of a number of cancers. We analyzed polymorphisms in the Xeroderma Pigmentosum, Complementation Group C (XPC) gene for their correlation with urinary bladder cancer. Ala499Val and Lys939Gln polymorphisms were genotyped in 234 urinary bladder cancer cases and 258 control samples. A significant association between Ala499Val polymorphism and bladder cancer was observed (OR = 1.78, CI = 1.19-2.66, p = 0.005); however, Lys939Gln was unrelated (OR = 0.97, CI = 0.65-1.45, P = 0.89). Further analysis revealed that Ala499Val was a significant risk factor only in the presence of smoking (OR = 2.23, CI = 1.28-3.87, p < 0.004) or tobacco chewing (OR = 2.40, CI = 1.43-4.04, p = 0.0008). To further appraise the association, we undertook meta-analyses on seven studies (2893 cases and 3056 controls) on Ala499Val polymorphism and eleven studies (5064 cases and 5208 controls) on Lys939Gln polymorphism. Meta-analyses corroborated the above results, showing strong association of Ala499Val (OR = 1.54, CI = 1.21-1.97, p = 0.001) but not that of Lys939Gln (OR = 1.13, CI = 0.95-1.34, p = 0.171) with urinary bladder cancer risk. In conclusion, XPC Ala499Val substitution increases urinary bladder cancer risk, but Lys939Gln appears to be neutral.