hMLH1基因启动子区甲基化在胃癌阶段性发生发展中的作用

Effect of methylation of hMLH1 gene promotor on stage tumorigenesis and progression of human gastric cancer

目的：通过检测胃癌原发灶及距离原发灶不同距离组织hMLH1基因启动子区甲基化状态，探讨hMLH1基因启动子区甲基化在胃癌阶段性发生发展中的作用。方法选取2006年1月至2006年8月在中国医科大学肿瘤研究所保存的行胃癌根治术治疗的40例胃癌患者的组织标本，分别在标本距胃癌原发灶边缘5 cm、3 cm、1 cm及胃癌原发灶各取材2份，1份用于组织病理学检查，另1份采用甲基化特异性PCR法检测hMLH1基因启动子区甲基化。结果 hMLH1基因启动子区甲基化阳性率在距胃癌原发灶边缘1 cm、3 cm和5 cm组织中分别为10％（4／40）、12．5％（5／40）及2．5％（1／40），均明显低于胃癌组织原发灶的32．5％（13／40），差异有统计学意义（P＜0．05）。病理检查示，癌旁1 cm和3 cm组织中检出23例癌前病变，癌旁5 cm组织中24例为正常胃组织者。hMLH1甲基化阳性率在正常胃组织、癌前病变组织及胃癌原发灶中分别为0（0／24）、8．7％（2／23）和32．5％（13／40），差异具有统计学意义（P＜0．01）。 hMLH1基因甲基化阳性率在肿瘤穿透浆膜的胃癌组织中为57．1％（8／14），明显高于未透浆膜组织的19．2％（5／26）；在转移淋巴结大于或等于7枚的胃癌组织中其阳性率为61.5%（8／13），明显高于转移淋巴结少于7枚组织的18.5%（5／27）；差异均有统计学意义（均P＜0．05）；而不同年龄、性别、组织学分化程度、大体类型、生长方式及TNM分期的胃癌原发灶hMLH1基因甲基化阳性率间差异无统计学意义（P＞0．05）。结论 hMLH1基因启动子区异常甲基化可能促进胃癌的发生及发展。

Objective To illustrate the role of methylation level of hMLH1 gene promoter in different stages of gastric carcinogenesis by methylation-specific PCR （MSP） detection of samples from paracancerous tissue and gastric cancer tissue. Methods Methylation status of hMLH1 gene promoter of 40 patients undergoing radical stomach cancer operation in the Tumor Research Institute of China Medical University between January 2006 and August 2006 was detected by MSP. For each patient , 2 samples were chosen from the cancer site, paracancerous tissues of 1 cm, 3 cm, 5 cm away from the cancer site, separately. One sample was used in pathology examination, and the other in methylation detection. Results Positive rates of hMLH1 gene promoter methylation in the paracancerous tissues of 1 cm, 3 cm, 5 cm away from the cancer site were 10%（4/40）, 12.5%（5/40） and 2.5%（1/40） respectively, which were significantly lower than 32.5% （13/40） in cancer site （all P 〈0.05）. Pathological examination showed precancerous lesions in 23 samples of paracancerous 1 cm and 3 cm＆amp;nbsp;tissues and normal tissues in 24 samples of paracancerous 5 cm tissues. Positive rates of hMLH1 gene promoter methylation in the cancer site , paracancerous tissue and normal gastric tissue were 32.5%（13/40）, 8.7%（2/23） and 0（0/24） （P〈0.01）. For cancer tissue penetrated the gastric serosa, 8 out of 14 tissue samples were positive methylation （57.1%）, which was significantly higher compared with 5 out of 26 tissue samples without penetration of gastric serosa （19.2%）. Positive rate of hMLH1 gene promoter methylation in tissue samples with 7 or more of metastatic lymphatic node number was 61.5%（8/13）,which was higher compared to that with less than 7 （5/27, 18.5%） （P〈0.05）. No significant differences of positive rate of hMLH1 gene promoter methylation were found between different tumor gross types, tumor grow pattern, tumor differentiation degree, patient age and sex （all P〉0.05）. Conclusion Hypermethylation of hMLH1 gene promoter may be associated with the carcinogenesis stages and progression of human gastric cancer.