错配修复基因hMLH1和hMSH2甲基化及突变与地方性砷中毒关系

[目的]探讨错配修复基因hMLH1和hMSH2启动子区CpG岛甲基化及第12外显子（exon12）突变与燃煤污染型地方性砷中毒发生发展乃至癌变的关系。[方法]以砷中毒患者110例为病例组,按临床诊断分为轻、中、重度组;按皮肤病理诊断分为非癌变组和癌变组。采用甲基化特异性聚合酶链反应（MSP）法检测其中105例砷中毒患者和82例对照人群外周血中hMLH1和hMSH2基因启动子区的甲基化情况;采用聚合酶链反应-单链构象多态性分析（PCR-SSCP）检测110例砷中毒患者和110例对照人群外周血中hMLH1和hMSH2基因exon12突变情况。[结果]①轻、中、重度组砷中毒患者hMSH2基因甲基化阳性率分别为11.76%、16.28%和32.14%,均明显高于对照组,重度组亦明显高于轻度组（P〈0.05或P〈0.01）;癌变组患者hMLH1和hMSH2基因甲基化阳性率分别为11.11%和27.78%,均明显高于对照组（P〈0.05）;hMLH1和hMSH2基因甲基化阳性率均随临床病情和皮肤病变程度加重而增高（P〈0.05或P〈0.01）。②病例组和对照组均未发现hMLH1和hMSH2基因exon12突变。[结论]错配修复基因hMLH1和hMSH2启动子区甲基化是砷中毒发生发展乃至癌变的早期分子特征,亦可能是导致错配修复功能缺陷的主要方式之一。

A Study on Ralationship of the Methylation and Mutation of Mismatch Repair Gene hMLH1 and hMSH2 in Patients with Endemic Arsenism

[Objective] To explove the relationship of the promoter 5’CpG island methylation of mismatch repair gene hMLH1 and hMSH2 and the mutation of their exon12 with the effect of arsenism development cause by coal-burning,and also the process of canceration.[Methods] A total of 110 cases of arsenism patients were selected as case group,classified as mild, moderate and severe subgroups according to their clinical diagnosis,and also divided into non-cancerous and carcinoma subgroups according to the pathology of their skin lesions.Methylation status of the hMLH1 and hMSH2 promoter region were assayed by methylation-specific polymerase chain reaction（MSP）in peripheral blood of 105 arsenism patients and 82 normal controls.The mutations of hMLH1 and hMSH2 exon12 were analyzed by polymerase chain reaction-single strand conformation polymorphism （PCR-SSCP）in peripheral blood DNA of 110 arsenism patients and 110 normal controls.[Results] ①The positive rates of hMSH2 methylation were 11.76%,16.28%and 32.14%in mild,moderate and severe patients respectively,all significantly higher than those in controls,and the rate in severe patients were significantly higher than that in moderate.The positive rates of hMLH1 and hMSH2 were 11.11%and 27.78%in non-cancerous and carcinoma groups respectively,both significantly higher than that in controls.With the severity of clinical condition and skin lesions the positive rates of hMLH1 and hMSH2 methylation increased. ②There were no mutations of mismatch repair gene hMLH1and hMSH2 exon12 in patients and controls.[Conclusion] The promoter hypermethylation of the mismatch repair gene hMLH1and hMSH2 is an early incident in the development of arsenism and in the process of carcinogenesis,and it may be one of the main reasons leading to its defect or deactivation of gene function.