Association of A66G polymorphism with cancer susceptibility: Evidence from 85 studies.

Methionine synthase reductase (MTRR) is a key regulatory enzyme involved in the folate metabolic pathway. Previous studies investigating the association of A66G polymorphism with cancer susceptibility reported inconclusive results. We performed the current meta-analysis to obtain a more precise estimation of the possible association. Published literatures were identified from PubMed, Embase and CBM databases up to October 2016. The strength of the association between the A66G polymorphism and cancer susceptibility was assessed using odds ratios (ORs) and the corresponding 95% confidence intervals (CIs). Eighty five published studies with 32,272 cases and 37,427 controls were included in this meta-analysis. Pooled results indicated that the A66G polymorphism was associated with an increased overall cancer risk (homozygous model: OR = 1.08, 95% CI = 1.02-1.15, = 0.009; recessive model: OR = 1.06, 95% CI = 1.00-1.12, < 0.001 and allele comparison: OR = 1.03, 95% CI = 1.00-1.06, < 0.001). Stratification analysis further indicated significant associations in head and neck cancer, Caucasians, Africans, and high quality studies. However, to avoid the "false-positive report", the significant findings were assessed by the false-positive report probability (FPRP) test. Interestingly, the results of FPRP test revealed that the increased risk for A66G polymorphism among Africans need further validation due to the high probabilities of false-positive results. This meta-analysis suggests that the A66G polymorphism is associated with significantly increased cancer risk, a finding that needs to be confirmed in single large studies.