中文摘要：

目的：探讨代谢叶酸的亚甲基四氢叶酸还原酶（MTHFR）基因单核苷酸多态与胃癌风险的关系。方法：以聚合酶链反应和限制性片段长度多态方法分析170例胃癌病人和性别、年龄配对的140例正常对照者的MTHFR基因C677T和A1298C基因型及其与胃癌风险的相关性。结果：在正常对照中，MTHFR基因677CC、CT、TT基因型频率分别为47．9％、40％和12．1％，而在胃癌病人中分别为35．9％、45．9％和18．2％。在病例组中677（CT＋TT）变异型基因者占64．1％，显著高于对照组中的52．1％，差异具有显著意义（X^2=4．54，P〈0．05）。与677CC基因型者相比，变异型基因者和下r型基因者发生胃癌的危险性分别高1，67倍（OR为1．67，95％CI为1．06—2．64）和2．67倍（OR为2．67，95％CI为1．382—5．341）。A1298C基因型在病例和对照中的分布差异无显著性意义。但进一步分析发现，1298变异基因型与677变异基因型之间有协同作用。携带MTHFR677TT/1298AC基因型个体发生胃癌的风险是携带MTHFR677CC／1298AA基因型个体的3．684倍（95％CI为0．829～25．776）。结论：MTHFR单核苷酸多态是胃癌的遗传易感性因素。

英文摘要：

Objective To explore the relationship between methylenetetrahydrofolate reductase （MTHFR） gene polymorphisms （C677T and A1298C） and risk of gastric carcinoma. Methods Genomic DNA was isolated from the 170 patients with gastric carcinoma and 140 age- and sex- matched control subjects. Polymerase chain reaction and restriction fragment length polymorphism were used to examine the polymorphisms of MTHFR genes C677T and A1298C, and the relation between the genotypes and risk of gastric carcinoma was analyzed. Results The frequencies of C677T genotype were： CC（47.9% ）, CT（40% ）, CT（ 12.1% ） in control group and CC（35.9% ）, CT（45.9% ）, TT（ 18.2% ） in gastric carcinoma group, respectively. The genotype frequency of 677CT and 677TT was 64.1% among gastric carcinoma cases, and the genotype frequency of 677CT and 677TT was 52.1% （X2 =4.54 ,P 〈0.05） among controls. The individuals with 677 （CT ＋ TT） genotype group or 677TT had a 1.67-fold （95% CI：1. 06-2.64 ） or 2.67-fold （95% CI： 1. 382-5. 341 ） increased risk of developing gastric carcinoma compared with those had 677CC genotype. The genotype of MTHFR gene A1298C, allele was not significantly different between the two groups. We found that a joint effect exits between the MTHFR C677T and A1298C polymorphism on the risk of gastric carcinoma. Compared with the individuals with 677CC/1298AA genotype, the individuals with 677TT/1298AC genotype had a 3. 684 - fold （95% CI： 0. 829 - 25. 776） risk of developing gastric carcinoma. Conclusion The single nucleotide polymorphisms in the MTHFR gene are associated the risk of gastric carcinoma in the Chinese population.