胃癌的微卫星不稳定性与hMLH1基因启动子甲基化的关系  

Methylation of hMLH1 Gene Promoter in Gastric Carcinoma with Microsatellite Instability

作　　者：李建华[1] 石先哲[2] 刘敏[1] 王彦[1] 于志红[1] 许国旺[2] 吕申[1] 

机构地区：[1]大连医科大学附属第二医院实验中心分子生物学实验室,辽宁大连116027 [2]中国科学院大连化学物理研究所,国家色谱研究分析中心,辽宁大连116011

出　　处：《癌症》2005年第3期273-277,共5页Chinese Journal of Cancer

基　　金：中国科学院知识创新工程领域前沿项目(No.K2001A4)~~

摘　　要：背景与目的:由于细胞错配修复功能缺陷而导致基因组微卫星序列高度不稳定是遗传性非息肉性大肠癌发生的主要原因。以往的研究表明胃癌组织也有错配修复蛋白表达的缺失,但错配修复基因突变频率却很低;而启动子的甲基化是肿瘤抑癌基因失活的主要途径,也可能是错配修复基因功能丧失的主要原因。本研究拟通过对胃癌组织的微卫星不稳定性的分析及对hMLH1基因启动子甲基化和蛋白表达的检测,对胃癌发病的分子机制进行探讨。方法:从52例胃癌患者的癌组织及其周围组织提取DNA,PCR扩增基因组的5个微卫星位点BAT-26、D17S261、D3S1283、D2S123和D3S1611,毛细管电泳后,判定胃癌组织的微卫星不稳定性;免疫组织化学方法检测hMLH1蛋白的表达;酶切法检测hMLH1基因启动子甲基化。结果:52例胃癌标本中微卫星高度不稳定13例,低度不稳定2例,稳定37例。微卫星高度不稳定的13例胃癌组织中,均检测到hMLH1基因启动子甲基化(100.0%);微卫星低度不稳定和微卫星稳定的39例胃癌组织中,hMLH1基因启动子甲基化仅1例(2.6%),前者发生率高于后者,两者之间有显著性差异(P<0.01)。微卫星高度不稳定的13例胃癌的癌旁组织中,hMLH1基因启动子甲基化6例(46.2%),而微卫星低度不稳定和微卫星稳定39例胃癌的癌旁肿瘤组织标本中。BACKGROUND & OBJECTIVE: Mismatch repair (MMR) deficiency, characterized by microsatellite instability (MSI), is a major cause of hereditary nonpolyposis colorectal carcinoma (HNPCC). Our previous study showed that loss of MMR protein expression can also be seen in gastric carcinoma, but MMR gene mutation seldom occur. Promoter methylation, a main cause of suppressor gene inactivation, might also lead to defect of MMR gene function. This study was designed to investigate the relationship of hMLH1 gene promoter methylation status to MSI in gastric carcinoma, and analyze its action as a risk factor of carcinogenesis. METHODS: DNA was extracted from 52 samples of gastric carcinoma and their adjacent non-cancerous gastric mucosa. Polymerase chain reaction (PCR) was used to amplify microsatellite loci BAT-26, D17S261, D3S1283, D2S123, and D3S1611. MSI was studied by capillary electrophoresis. Methylation of hMLH1 gene promoter was detected by restrictive endonuclease digestion, expression of hMLH1 protein was detected by immunohistochemistry. RESULTS: Of the 52 specimens of gastric carcinoma, 13 with high MSI (MSI-H), 2 with low MSI (MSI-l), and 37 with microsatellite stability (MSS). Frequency of hMLH1 promoter methylation was significantly higher in the 13 specimens of gastric carcinoma with MSI-H than in the 39 specimens of gastric carcinoma with MSI-L or MSS (100% vs. 2.6%, P<0.01). Furthermore, frequency of hMLH1 promoter methylation was significantly higher in the 13 specimens of adjacent non-cancerous gastric mucosa of gastric carcinoma with MSI-H than in the 39 specimens of adjacent non-cancerous gastric mucosa of gastric carcinoma with MSI-L or MSS (46.2% vs. 2.6%, P<0.01). The methylation status was accordant with loss of hMLH1 protein expression. Methylation of hMLH1 gene promoter had no relation with differentiation and clinical stage of gastric carcinoma. CONCLUSION: Methylation of hMLH1 gene promoter exists in gastric carcinoma tissues with MSI-H, and their adjacent non-cancerous gastric mucosa, it may be

关 键 词：胃肿瘤 HMLH1基因 甲基化 微卫星 

分 类 号：R735.2[医药卫生—肿瘤]