胃癌中p16^(INK4a)基因启动子高甲基化及其蛋白表达

Correlation of p16^(INK4a) promoter hypermethylation with p16^(INK4a) protein loss in gastric carcinomas

目的探讨胃癌中p16INK4a基因失活的主要分子机制及其与胃癌发生、发展的关系。方法采用甲基化特异性PCR技术检测62例胃癌和癌旁组织及10例慢性胃炎黏膜p16INK4a基因启动子区CpG岛甲基化状态,用免疫组化EnVision两步法检测p16INK4a蛋白的表达。结果62例胃癌和癌旁组织p16INK4a基因启动子高甲基化率分别为51·6%(32/62)和19·4%(12/62),10例正常对照胃黏膜未发现高甲基化,胃癌组织p16INK4a基因启动子高甲基化率高于癌旁组织和正常对照(P<0·05)。58·1%(36/62)的胃癌组织p16INK4a蛋白表达阴性,其中72·2%(26/36)的病例具有p16INK4a基因启动子的高甲基化,p16INK4a基因启动子的高甲基化与其蛋白失表达密切相关(P<0·05)。结论胃癌中p16INK4a基因启动子的高甲基化是p16INK4a基因失活的主要机制,并可能是胃癌发生中的早期分子事件。

Purpose To detect the p16^INK4a gene promoter methylation and its protein expression in human gastric carcinoma,aimed to explore the predominant molecular mechanism of inactivation of the p16^INK4a gene and its relationship with carcinogenesis and progression of gastric carcinoma. Methods A total of 62 gastric carcinoma tissues and their adjacent normal tissues and 10 nontumorous gastric tissues from gastritis patients were study, the methylation status of the 5′CpG island of p16^INK4a gene was evaluated using methylation specific PCR（MSP）. Protein expression of p16^INK4a gene was assessed by immunohistochemical method. Results Hypermethylation of the promoter region of p16^INK4a gene in 62 gastric carcinoma and their tumor-adjacent normal tissues were 51.6% （32/62） and 19.4% （12/62） respectively,while no methylation abnormality was found in nontumorous gastric tissues. Hypermethylation of the promoter region of p16^INK4a gene in gastric carcinoma was significantly higher than that in tumor-adjacent normal tissues and nontumorous gastric tissues（ P 〈 0. 05 ）. 36 cases were negative for p16^INK4a protein,26 of these 36 cases had hypermethylation of the promoter region of the p16^INK4a gene. Hypermethylation of the promoter was strongly associated with loss of p16^INK4a protein by immunohistochemistry（ P 〈0.05）. Conclusions Promoter hypermethylation is the predominant mechanism of inactivation of p16^INK4a gene and which may be an early event in the pathogenesis of gastric carcinoma.