错配修复基因启动子甲基化与胰腺癌发生的关系

目的通过对胰腺癌错配修复基因启动子甲基化及蛋白表达的检测与微卫星不稳定性的分析，探讨胰腺癌发病的分子机制。方法从35例胰腺癌病人的正常胰腺组织、癌组织中提取DNA；MSP法检测hMLH1及hMSH2基因启动子甲基化状态；SSCP法检测标本中微卫星不稳定性发生情况；免疫组化法检测错配修复基因hMLH1及hMSH2在胰腺癌中的表达情况。结果35例胰腺癌中hMLH1启动子甲基化发生率为60％（21／35），正常组织中未发现甲基化，两者之间有统计学差异（P〈0.05）；而对于hMSH2仅有1例胰腺癌出现启动子甲基化；35例胰腺癌中微卫星高度不稳定7例，低度不稳定14例，稳定11例，正常组织中没有出现微卫星不稳定，两者之间有统计学差异（P〈0.05）；在微卫星不稳定的21例胰腺癌组织中有19例（90％）出现hMLH1启动子甲基化现象，微卫星稳定的ll例胰腺癌组织中仅有2例（6％）出现hMLH1启动子甲基化。hMLH1启动子甲基化在微卫星不稳定胰腺癌组织中常为缺失表达或低表达，在微卫星稳定胰腺癌组织中呈正常表达。hMSH2无论在MSI-H或MSI-L胰腺癌与正常胰腺组织中均无缺失表达，仅部分低表达。结论胰腺癌组织中错配修复基因的缺陷主要是hMLH1启动子甲基化，与胰腺癌微卫星不稳定性及蛋白表达缺失有关，在胰腺癌发生过程中起重要作用，是胰腺癌发生的重要机制之一。

Relation of mismatch repair gene promoter methylation to pancreatic carcinogenesis

Objective To investigate the relation of mismatch repair gene promoter methylation (MRGPM) to pancreatic carcinogenesis (PC). Methods DNA was extracted from tumor tissue and adjacent normal tissue of 35 cases of pancreatic carcinoma. Methylation of hMLH1 and hMSH2 gene promoter was verified by MSP analysis. SSCP was used to detect MSI.Immunohistochemistry was performed to determine the expression of hMLH1 and hMSH2 protein in pancreatic carcinoma. Results hMLH1 promoter methylation was found in 21 patients (60%) and none of the controls (P<0. 05). hMSH2 promoter methylation was found in 1 patient. Of the 35 patients, 7 had high MSI, 14 low MSI and 11 microsatellite stability. There was marked difference between the experimental group and the control group (P<0. 05). Meanwhile, the frequency of hMLH1 promoter methylation was remarkably higher in 21 patients with MSI than in 11 controls with MSS (P<0. 05). The methylation status of hMLH1 promoter was in accordance with deletion of hMLH1 protein expressioa hMSH2 was lowly expressed in both groups. Conclusions Methylation of hMLH1 gene promoter is the important factor resulting in defection of mismatch repair gene in pancreatic carcinoma and is related to MSI and deletion protein expression. Furthermore, it might be one of the important mechanisms of carcinogenesis in pancreatic carcinoma.