幽门螺杆菌对胃癌细胞中钙调蛋白基因启动子区去甲基化的诱导作用

Helicobacter pylori induces demethylation of the Calmodulin gene promoter in gastric cancer cells

目的:探讨钙调蛋白(CaM)基因在胃癌组织中的表达及其启动子区甲基化水平与幽门螺杆菌(Helicobacterpylori,H.pylori)感染的关系.方法:用实时荧光定量PCR法分别检测30例胃癌组织、癌周组织及转移淋巴结组织中CaM基因的表达量,并分析其表达量与H.pylori感染的关系.体外建立H.pylori感染胃癌细胞的实验模型和H.pylori细胞毒素相关蛋白A(cagA)基因稳定转染胃癌细胞的实验模型,以未处理的胃癌细胞为对照,用亚硫酸氢盐修饰后测序法检测实验模型细胞中CaM基因启动子区甲基化水平.结果:胃癌组织中CaM基因的表达量是癌周组织的2.08倍(P<0.05);H.pylori感染组中CaM基因的表达量是无H.pylori感染组的6.11倍(P<0.01),H.pylori及其毒素蛋白CagA可引起CaM基因启动子区-276位点发生去甲基化修饰.结论:H.pylori感染通过所分泌的毒力因子CagA诱导胃癌细胞中CaM基因启动子区去甲基化修饰,从而上调胃癌组织中CaM基因的表达.

Abstract AIM： To explore the expression of Calmodulin （CAM） gene in gastric cancer tissue and the re- lationship between the methylation level of the CaM gene promoter and Helicobacter pylori （H. pylori） infection. METHODS： The expression of the CaM gene in 30 cases of gastric cancer and matched tumor- adjacent gastric tissue and metastatic lymph nodes was assessed by real-time fluorescence quantitative PCR. The relationship between CaM gene expression and H. pylori infection was ana-lyzed. Methylation of CpG islands in the CaM gene promoter was measured by bisulfite modi- fied sequencing method in gastric cancer cells infected with H. pylori and stably transfected with the H. pylori cytotoxin-associated protein A （cagA） gene. RESULTS： The relative expression level of the CaM gene in cancer tissue was 2.08 times high- er than that in tumor-adjacent gastric tissue （P 〈 0.05）, The relative expression level of the CaM gene in H. pylori-positive gastric cancer was 6.11 times higher than that in the H. pylori-negative group （P 〈 0.05）. The demethylation at -276 bp in the CaM gene promoter was detected in H. pylori-infected and cagA-overexpressed gastric cancer cells. CONCLUSION： H. pylori, though secreting the virulence factor CagA, up-regulates the expres- sion of the CaM gene in gastric cancer possibly by inducing the demethylation of the CaM promoter.