中文摘要：

目的探讨5,10-亚甲基四氢叶酸还原酶（MTHFR）基因多态性与结直肠癌易感性的关系，方法以结直肠癌组和健康对照组基因型分布的OR值为效应指标,全面检索相关文献,纳入符合入选标准的文献,应用REVMAN4，2软件对各研究结果进行异质性检验和效应值合并,并进行发表偏倚评估和敏感性分析，结果纳入677位点相关文献18篇,1 298位点9篇,两位点的各研究结果均无统计学意义,677位点TT/（CT＋CC）合并OR值为0，80（95%CI 0，74～0，87）,1 298位点CC/（AC＋AA）合并OR值为0，84（95% CI 0，72～0，97）,两位点均不存在显著发表偏倚,敏感性分析提示,677位点结果较稳定,1298位点结果不稳定，结论MTHFR基因多态性的677 TF为结直肠癌的保护因素,1298 CC亦可能与结直肠癌危险性降低有关联。

英文摘要：

Objective To evaluate the relationship between 5,10-Methylenetetrahydrofolate reductase （MTHFK） gene polymorphiams and colorectal cancer （CRC）. Methods Studies were selected based on the criteria for inclusion. The Meta-analysis software, REVMAN 4.2, was applied for checking the heterogeneity across the studies and calculating the pooled OR. The results were evaluated by the analyses of publication bias and sensitivity. Results A total of 9 787 cases and 12 986 controls from 18 studies for C677T and a total of 4 422 cases and 5 819 controls from 9 studies for A1 298C were included. No heterogeneity among the studies was found. For codon 677, the frequencies of CC, CT and TT genotypes were 46.48%, 43.81% and 9.71% in cases, and 45.03%, 43.08% and 11.89% in controls, respectively. The pooled OR of TF vs. CT＋CC was 0.80 （95%C1 0.74-0.87）. For codon 1 298, the frequencies of AA, AC and CC genotypes were 53.60%, 39.39% and 7.01% in cases, and 53.31%, 38.67% and 8.03% in controls, respectively. The pooled OR of CC vs. AC＋AA was 0.84 （95%CI 0.72-0.97）. Condusions MTHFR 677TF is at lower risk of developing CRC and 1298CC genotypes might be associated with the decreased risk of developing CRC.