胃癌组织中p16基因甲基化分析

The methylation of p16 gene in gastric cancer tissues

目的 :探讨抑癌基因p16在胃癌组织中是否存在甲基化异常及其与胃癌发生发展的关系。方法 :对 2 0例胃癌组织及相应正常胃粘膜组织应用甲基敏感酶 (HpaII)和甲基非敏感酶 (MspI)酶切 ,结合PCR扩增技术 ,对p16基因外显子 1、外显子 2的二核苷酸胞嘧啶特定序列 5’ CCGG 3’位点甲基化进行检测。结果 :2 0例胃癌组织中 ,p16基因外显子 1、2异常甲基化分别为 5例 (2 5 % )和 9例 (45 % ) ,正常组织未发现甲基化异常 ;14例高甲基化标本中 ,中分化胃癌 4例 ,低分化 7例 ,高分化 1例 ;有 2例存在外显子 1、2同时甲基化异常 ,二者均为低分化胃癌 ,进展期胃癌 (Ⅲa、Ⅳ期各 1例 )中 1例呈现泳动易位 ;外显子 2甲基化异常多发生于晚期肿瘤患者 (P <0 .0 5 )。结论 :p16基因甲基化异常可能会造成基因功能丧失 ,从而失去对细胞增殖的负性调控作用 ,导致胃癌发生与进展 ;外显子 2高甲基化与临床进展有关 。

Aim:To study if abnormal methylation of p16 gene occur and its relationship with the progression of gastric cancer.Methods:The methylation pattern of 5mC at 5' CCGG 3' site in exon 1 and exon 2 of p16 gene was studied with PCR, using methylation sensitive restriction endonuclease HpaII and methylation insensitive restriction endonuclease MspI in 20 gastric cancer tissues and adjacent normal tissues.Results:The hypermethylation changes in exon 1 and exon 2 of p16 gene were 25%(5/20) and 45%(9/20) , respectively, while no methylation abnormality was found in adjacent normal tissues. Among 14 out of 20 cases of hypermethylation,4 and 7 cases were moderate and poorly differentiated cancer tissues, respectively, and 1 case was well differentiated cancer. Besides, 2 cases had methylation abnormalities in both exon 1 and 2 simultaneously, which were poorly differentiated and advanced gastric cancers (Ⅲa and Ⅳ stage), and mobility shift was detected in 1 of the 2 cases. Moreover, abnormal methylation of exon 2 was found to be associated with tumors at late stage ( P <0.05).Conclusion: The results suggest that the hypermethylation of p16 gene may play a role in the loss function of the gene, and may lead to loss of the negative regulation of cellular proliferation and contribute to the development of gastric cancer. The hypermethylation of exon 2 of p16 gene may have effects on the carcinogenesis of gastric mucosa and may be a later event.