甲基转移酶基因甲基化在结直肠肿瘤中作用的实验性研究  

The experimental research of the function of Methyl transferase gene methylafion in colorectal tumor

作　　者：高月秋[1] 任磊[1] 曲波[2] 刘波[3] 

机构地区：[1]哈尔滨医科大学第五临床医学院消化内科,大庆163311 [2]哈尔滨医科大学附属第二医院消化内科,150081 [3]大庆油田总医院神经外科,163311

出　　处：《国际免疫学杂志》2013年第2期162-166,共5页International Journal of Immunology

摘　　要：目的验证6-氧-甲基鸟嘌呤-DNA甲基转移酶（MGMT）基因启动子CpG岛高甲基化在结直肠癌发生、发展中的作用，并探讨联合检测基因甲基化发现早期结直肠肿瘤的可能性。方法用甲基特异性PCR（MSP）检测20例正常大肠粘膜、32例散发性结直肠腺瘤和34例散发性结直肠腺癌组织DNA中MGMT基因启动子的甲基化状况。同时用免疫组化方法检测MGMT蛋白的表达情况。结果正常大肠粘膜组织均不存在甲基化，40．6％（13／32）的腺瘤组织和44．1％（15／34）的腺癌组织存在MGMT基因启动子CpG岛高甲基化。正常大肠黏膜胞核和胞浆表达MGMT蛋白，21．9％（7／32）的腺瘤和50．0％（17／34）的腺癌MGMT蛋白表达缺失，其差异有统计学意义（P=0．018）。7例MGMT表达缺失的腺瘤中6例存在甲基化（P=0．027），17例表达缺失的腺癌中14例存在甲基化（X^2=17，P〈0．001）。结论结直肠肿瘤中存在高频率MGMT基因启动子CpG岛高甲基化和MGMT蛋白表达缺失。腺癌中蛋白表达缺失比腺瘤中更常见。MGMT基因表型遗传性失活可能在结直肠肿瘤发生过程中起重要作用，且联合检测异常甲基化基因可能为结直肠肿瘤的早期发现提供帮助。Objective To verify the effect of promoter hypermethylation of O^6-methylguanine-DNA methyhransferase（MGMT） gene on colorectal tumorigenesis and progression, and to explore the possibility of find the early eolorectal cancer by joint detection of gene methylation. Methods The promoter hypermethylation status of O^6-methylguanine-DNA methyhransferase gene was assayed in 32 sporadic colorectal adenomas, 34 sporadic colorectal carcinomas and 20 normal colorectal mucosa tissues by methylation-specific PCR. , The expression of MGMT protein in the same batch of samples was detected with immunohistochemistry as well. Results No CpG land hypermethylation was found in the normal colorectal mucosa tissues , but in 40.6% （ 13/ 32） of adenomas and 44.1% （15/34） of carcinomas, it was confirmed. Compared with the MGMT proteins expression in nucleus and cytoplasm of normal colorectal mucosa tissues, the loss of MGMT expression was veri- fied in 21.9% （7/32） of adenomas and 50.0% （17/34） of carcinomas, respectively. There were significant difference among them（P =0.018）. On the other hand, because of the salient overlapping phenomenon, i.e. methylation in6 of the 7 adenomas （P =0.027） and 14 of the 17carcinomas （X^2 = 17 ,P 〈 0. 001）with MGMT expression losing was discovered, the high relationship between the CpG island methylation and MGMT protein losing was proofed. Conclusions Promoter hypermethylation and loss of expression of MGMT gene was common events in colorectal tumorigenesis, and loss of expression of MGMT occurs more frequently in carcinoma than in adenoma in sporadic patients. It suggests that epigenetic inactivation of MGMT plays an important role in colorectal tumorigenesis, and it may be can provide a help for find the early colorectal cancer by joint detection of gene methylation.

关 键 词：6-氧-甲基鸟嘌呤-DNA甲基转移酶 CPG岛 DNA甲基化 表型遗传改变 

分 类 号：R735[医药卫生—肿瘤]