膀胱移行细胞癌中DNA错配修复基因hMLH1、hMSH2和hMSH3启动子区甲基化状态研究

CpG island methylation status of hMLH1,hMSH2 and hMSH3 gene and their expressions in bladder transitional cell carcinoma

目的探讨DNA错配修复基因启动子区CpG岛甲基化状态及其在膀胱移行细胞癌(BTCC)中的表达。方法应用MSP技术检测膀BTCC中hMLH1、hMSH2和hMSH3基因启动子区甲基化状态,RT-PCR法检测其mRNA表达水平。结果36例BTCC组织中hMSH1、hMSH2的甲基化阳性率分别为38.9%(14/36)、52.8%(19/36),所有标本中均未发现有hMSH3启动子甲基化。hMLH1、hMSH2、hMSH3 mRNA在BTCC中表达率分别为47.2%(17/36)、38.9%(14/36)、16.7%(6/36),在正常组织中分别为22.2%(8/36)、63.9%(23/36)、0%(0/36),差异均有统计学意义(P<0.01),并且随肿瘤病理分级的增加呈下降趋势(P<0.05),均与临床分期不相关(P>0.05)。结论hMLH1、hMSH2和hMSH3基因启动子异常甲基化可能导致该基因转录表达失活,使其mRNA表达减少甚至缺失,这可能是导致BTCC发生、发展的原因之一。

Objective To detect the hypermethylation status of the 5＇CpG island located in the promoter region of hMLH1, hMSH2 and hMSH3 gene and the expressions of their mRNA in bladder transitional cell carcinoma （BTCC）. Methods MSP technique was adopted to detect methylation status of hMLH1, hMSH2 and hMSH3 gene in BTCC, and RTPCR method was used to detect their mRNA levels. Results The frequency of promoter methylation of hMSH1 and hMSH2 gene in BTCC tissues was 38.9 % （14/36）, 52.8 % （19/36）, respectively, but hMSH3 methylation was not found in all bladder tissues. The expressions of hMLH1, hMSH2 and hMSH3 mRNA in the BTCC tissue were 47.2% （17/36）, 38.9% （14/ 36）, 16.7%（6/36）, respectively （P〈0.05）, and were 22.2% （8/36）, 63.9% （23/36）, 0% （0/36）, respectively in normal tissues. Differences between the two groups were statistically significant （P〈0.01）, and declined with the increasing pathological grades （P〈0.05）, but were no correlated with the clinical stages （P〉0.05）. Conclusion Hypermethylation can inactivate the transcription of hMLH1, hMSH2 and hMSH3 and reduce the protein expression. It may be a considerable mechanism which leads to oncogenesis and metastasis of BTCC.