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Analysis of inactivation mechanism for mismatch repair system in gastric carcinomas with micro satellite instability

微卫星不稳定性胃癌错配修复系统失活机制分析

基本信息

批准号：
12670163
负责人：
YOKOZAKI Hiroshi
金额：
$ 2.18万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12670163/
关键词：
gastric cancer microsatellite instability mismatch repair gene mutation DNA methylation

项目摘要

The aim of the research project is to clarify the clinicopathological characteristics of human gastric carcinomas with microsatellite instability as well as to analyze the molecular inactivation mechanisms for mismatch repair system within these cancers.The investigator established a routine microsatellite analysis system using conventional histopathological specimens. Extracted gastric cancers with microsatellite instability were subjected for the mutation of mismatch repair system genes (hMLH1, hMSH2) by PCR-SSCP and direct sequencing. Expression of mismatch repair immunohistochmistry using specific monoclonal antibodies. Methylation of promoter CpG sequences in these repair genes were analyzed by methylation specific PCR method which was established and optimized for the DNA extracted from hitopathological paraffin sections.From the routine microsatellite analysis over 1000 gastric cancer biopsies, the investigator clarified the clinicopathological characteristics of the gastric carcinomas with micorosatellite instability as following, (1) they share about 6% of overall gastric carcinomas, (2) most of the tumors are protruding type well-differentiated adenocarcinomas, (3) patients with gastric tumors with microsatellite instability prone to have multiple tumors within the same stomach or other gastrointestinal tracts. Although mutation analysis of mismatch repair genes within these tumors failed to demonstrate 2-hit genetic inactivation of the genes, most of the tumors demonstrated loss of expression of hMLH1 along with the hypermethylation of its promoter CpG sequences.These results suggest that epigenetic inactivation of one of the mismatch repair system gene, hMLH1, may have the crucial role in the carcinogenesis of gastric carcinomas with microsatellite instability.

本研究的目的是阐明具有微卫星不稳定性的胃癌的临床病理学特征，并分析这些癌症中错配修复系统的分子失活机制。研究者使用常规组织病理学标本建立了常规微卫星分析系统。采用PCR-SSCP和直接测序法检测错配修复系统基因（hMLH 1、hMSH 2）的突变情况。使用特异性单克隆抗体的错配修复表达。采用甲基化特异性PCR方法对1000例胃癌组织标本进行微卫星分析，明确了微卫星不稳定性胃癌的临床病理特征，（1）它们约占全部胃癌的6%，（2）大多数肿瘤是突出型高分化腺癌，（3）具有微卫星不稳定性的胃肿瘤患者易于在同一胃或其他胃肠道内发生多个肿瘤。尽管这些肿瘤中错配修复基因的突变分析未能证明该基因的2次击中遗传失活，但大多数肿瘤显示hMLH 1沿着其启动子CpG序列的高甲基化而表达缺失。可能在微卫星不稳定性胃癌的发生发展中起重要作用。