Department of Internal Medicine, Uijongbu St. Mary's Hospital, The Catholic University of Korea, Uijongbu 480-717, South Korea.
Cancer Lett. 2012 Dec 29;326(1):96-104. doi: 10.1016/j.canlet.2012.07.032. Epub 2012 Aug 4.
Chronic Helicobacter pylori infection is associated with the decreased expression of the gastric tumour suppressor protein p27. Because transcription of the gene p27 may be regulated epigenetically through histone acetylation, which is mediated by G-protein coupled delta opioid receptor (DOR) stimulation, we examined whether H. pylori regulates the DOR/histone acetylation/p27 promoter pathway. The levels of acetylated histone and p300, a gene-specific histone acetyltransferase within the p27 promoter, were measured using ChIP assays. The expression of phospho-DOR was evaluated by Western blot and immunohistochemical analyses. Growth curves were constructed, and cell proliferation was assessed after BrdU incorporation. Low p27 expression in acutely H. pylori-infected AGS gastric epithelial cells and in chronically H. pylori-infected AGS-derived HS3C cells was associated with approximate 20% and 40% decreases in p27 mRNA expression, respectively, when compared to p27 mRNA levels in uninfected AGS parental cells. The low p27 mRNA levels following H. pylori infection were associated with a 15-60% reduction in p27 promoter histone H4 acetylation. The recruitment of p300 to the p27 promoter was also markedly decreased by H. pylori infection. The expression of phospho-DOR was decreased by H. pylori infection in cell lines in vitro and in H. pylori-infected human gastric mucosa in vivo. The level of cellular p27 inversely correlated with cell proliferation in HS3C cells. These results demonstrate that H. pylori decreases p27 expression by modulating the DOR and thereby inhibiting histone acetylation of the p27 promoter. These findings link low gastric p27 expression levels with increased instances of gastric carcinogenesis associated with H. pylori infection.
慢性幽门螺杆菌感染与胃肿瘤抑制蛋白 p27 的表达减少有关。由于基因 p27 的转录可能通过组蛋白乙酰化来进行表观遗传调控，而组蛋白乙酰化是由 G 蛋白偶联的德尔塔阿片受体（DOR）刺激介导的，因此我们研究了幽门螺杆菌是否调节 DOR/组蛋白乙酰化/p27 启动子途径。使用 ChIP 检测测定乙酰化组蛋白和 p300（p27 启动子内的基因特异性组蛋白乙酰转移酶）的水平。通过 Western blot 和免疫组织化学分析评估磷酸化 DOR 的表达。构建生长曲线，并在 BrdU 掺入后评估细胞增殖。与未感染 AGS 亲本细胞相比，急性 H. pylori 感染的 AGS 胃上皮细胞和慢性 H. pylori 感染的 AGS 衍生的 HS3C 细胞中的低 p27 表达分别与 p27 mRNA 表达降低约 20%和 40%相关。感染 H. pylori 后，p27 mRNA 水平降低与 p27 启动子组蛋白 H4 乙酰化降低 15-60%相关。幽门螺杆菌感染也明显减少了 p27 启动子 p300 的募集。体外细胞系和体内 H. pylori 感染的人胃黏膜中，DOR 的表达被 H. pylori 感染下调。细胞 p27 的水平与 HS3C 细胞中的细胞增殖呈负相关。这些结果表明，幽门螺杆菌通过调节 DOR 降低 p27 的表达，从而抑制 p27 启动子的组蛋白乙酰化。这些发现将胃内 p27 表达水平降低与与 H. pylori 感染相关的胃癌发生几率增加联系起来。
