结直肠癌环氧化酶-2、错配修复酶-1微卫星不稳定与基因调控的关系

Study the relationship between the gene regulation and microsatellite instability of the cyclooxygenase-2,hMLH1 in colon carcinoma

目的 检测临床手术切除42例结直肠癌及相应正常组织环氧化酶-2（COX-2）、错配修复酶-1（hMLH1）微卫星不稳定状态（MSI）及二种基因启动子甲基化,探讨它们与结直肠癌发生的关系.方法 采用聚合酶链反应（PCR）技术检测5个位点的MSI状态;甲基化特异性PCR（MSP）方法检测结直肠癌及正常组织COX-2、hMLH1二种基因启动子CpG岛甲基化状态.结果 42例结直肠癌中MSI总检出率为42.86%（18/42）,5个位点的MSI检出率差异无统计学意义（P＞0.05）.COX-2和hMLH1基因启动子CpG岛甲基化在42例结直肠癌中分别有13例和15例.MSI-H组中COX-2基因启动子CpG岛甲基化8例,且有6例结直肠癌同时出现hMLH1和COX-2基因启动子CpG岛甲基化.结论 MSI结直肠癌hMLH1基因启动子CpG岛甲基化率高于MSS结直肠癌,hMLH1基因启动子CpG岛甲基化有助于判断肿瘤类型.

Objective To investigate the cyclooxygenase-2 （COX-2）,human mut-lhomologue 1 （hMLH1） of genes promoter methylation and microsatellite instability （MSI） frequency in 42 cases of human colon carcinoma and normal tissues, and to evaluate the relationship between them and occurrence of colon carcinoma. Methods Methylation specific polymerease chain reaction （ MSP） and polymerase chain reaction （PCR） methods were employed in this study in order to investigate the promoter methylation of these genes and 5 loci MSI frequency in human colon carcinoma and normal tissues. Results Of 42 colon carcinoma cases,the total frenquency of MSI was 43.86 % （ 18/42）. The MSI frenquency no significant discrepancy was found among the 5 loci （P 〉 0.05）. The number of MSI, MSS was 18 and 24, respectively. Cases with methylation of COX-2 and hMLH1 gene promoter CpG islands in colon carcinoma were 13 and 15 ,and they were not detected in normal tissues. 8 cases with methylation of COX-2 gene promoter CpG islands only occurred in MSI-H colon carcinoma, and 6 cases both with methylation of COX-2 and hMLH1 gene promoter CpG islands was observed in MSI-H. Conclusion The methylation rate of hMLH1 gene promoter CpG islands in MSI colon carcinoma was higher than that in MSS colon carcinoma. It suggested that detecting the methylation of hMLH1 gene promoter CpG islands might be a useful method for determining the colon carcinoma type.