MTHFR Gene Polymorphisms and Bladder Cancer Susceptibility: a Meta-Analysis Including Race, Smoking Status and Tumour Stage

Epidemiological studies have investigated that functional polymorphisms in the methylene-tetrahydrofolate reductase (MTHFR) gene may play an essential role in bladder carcinogenesis, but the numerous published studies have reported inconclusive results. The objective of the current study was to conduct an updated analysis in order to investigate the association between polymorphisms in the MTHFR gene and risk of bladder cancer. We searched the Pubmed database for all articles published up to March 31, 2011 that addressed bladder cancer and polymorphisms and variants or mutations of MTHFR for analysis using statistical software. Results for two polymorphisms (C677T and A1298C) in 27 case-control were studies from 15 articles indicated individuals carrying the 677T allele (TC or TT+TC) to have a reduction to a 29% or 21% compared to the wild genotype (CC) in mixed populations (OR: 0.71, 95% CI: 0.55-0.93 or OR: 0.79, 95% CI: 0.64-0.97, respectively) and it is shown that there is significant positive associations between A1298C polymorphism and bladder cancer in Africans (OR: 1.24, 95% CI: 1.02-1.52 for C vs. A; OR: 1.35, 95% CI: 1.10-1.66 for CA vs. AA; OR: 1.29, 95% CI: 1.08-1.55 for CC+CA vs. AA). However, no significant relationship was found in two polymorphisms in the stratified analysis by smoking status. Interestingly, individuals carrying the 677T allele (TT+TC) demonstrated a higher percentage of invasive than superficial cases (OR: 1.38, 95% CI: 1.13-1.69). The results from the current update analysis suggest that C677T and A1298C polymorphisms in the MTHFR gene are associated with bladder cancer risk and prognosis. Further evaluation based on more studies with larger groups of patients are now required.