Role of Iron and B-Catenin Activation in Gastric Carcinogenesis

幽门螺杆菌是已知的胃腺癌的最大危险因素，而胃腺癌是全球与癌症相关的死亡的第二大原因，但只有一小部分感染者患上了这种恶性肿瘤。幽门螺杆菌增加癌症风险的一个决定因素是CAG IV型分泌系统(T4SS)，它将微生物癌蛋白GagA转移到上皮细胞中。我们与项目2产生的初步数据表明，GAGA的细胞内递送激活了B-连环蛋白，并且在幽门螺杆菌感染的上皮细胞中，β连环蛋白激活的结果是过度增殖。我们的研究还表明，铁的耗竭增强了幽门螺杆菌激活β-连环蛋白的能力。我们现在已经用胃组织病理学核心A表明，铁的耗竭以cagA依赖的方式加速了幽门螺杆菌诱导的沙土鼠癌症的发展。蛋白质组学核心B进行的二维(20)DGE/MS鉴定了从缺铁和富铁沙土鼠分离的幽门螺杆菌菌株中存在33种差异丰富的蛋白质，其中几种参与了微生物黏附和CAG T4SS的功能。这些结果直接为项目3进行的具有挑衅性的新研究提供了信息，该研究表明，从缺铁沙土鼠中获得的或在体外缺铁条件下生长的H.Pylori菌株具有更强的组装CAG T4SS、转位GagA和诱导促炎细胞因子表达的能力。我们还开发了幽门螺杆菌感染的新模型，更接近地概括了发生在胃壁龛内的事件。胃类器官是一种三维的单层上皮器官样结构，为在临床前模型中研究宿主幽门螺杆菌的相互作用提供了独特的机会。我们现在已经成功地培养、维持、表征和感染了幽门螺杆菌感染的胃类器官。我们的假设是，铁缺乏增加了幽门螺杆菌CAg�依赖的肿瘤发生。我们将通过以下目标来测试这一点： 1.确定铁缺乏和幽门螺杆菌对肿瘤发生的调控机制。 2.利用一种新的体外有机系统确定幽门螺杆菌诱导的致癌反应。 3.使用铁缺乏背景下的胃癌沙鼠模型，确定上皮细胞对致癌幽门螺杆菌和cagA突变株的分子反应的差异。

H. pylori is the strongest known risk factor for gastric adenocarcinoma, the second leading cause of cancer-related death worldwide, yet only a fraction of infected persons ever develop this malignancy. One H. pylori determinant that augments cancer risk is the cag type IV secretion system (T4SS), which translocates the microbial oncoprotein GagA into epithelial cells. Our preliminary data generated with Project 2 demonstrate that intracellular delivery of GagA activates B-catenin and that a consequence of Beta catenin activation within H. pylori-infected epithelial cells is hyperproliferation. Our studies have also demonstrated that iron depletion augments the ability of H. pylori to activate Beta-catenin. We have now shown with Gastric Histopathology Core A that iron depletion accelerates the development of H. pylori induced cancer in gerbils in a cagA-dependent manner. Two-dimensional (20) DIGE/mass spectrometry performed by Proteomics Core B identified 33 differentially abundant proteins among H. pylori strains isolated from iron-depleted versus iron-replete gerbils, several of which mediate microbial adherence and function of the cag T4SS. These results directly informed provocative new studies performed with Project 3 demonstrating that H. pylori strains harvested from iron-depleted gerbils or grown under iron-depleted conditions in vitro exhibit an enhanced capacity to assemble the cag T4SS, translocate GagA, and induce expression of proinflammatory cytokines. We have also developed new models of H. pylori infection that more closely recapitulate events occurring within the gastric niche. Gastric organoids are three dimensional, single-layered epithelial organ-like structures, and provide a unique opportunity to study host H. pylori interactions in a pre-clinical model. We have now successfully grown, maintained, characterized, and infected gastric organoids with H. pylori. Our hypothesis is that iron depletion augments H. pylori cag� dependent oncogenesis. We will test this via the following Aims: 1. Define mechanisms that regulate oncogenesis in response to iron deprivation and H. pylori. 2. Define H. pylori-induced carcinogenic responses using a novel ex vivo organoid system. 3. Define differences in epithelial molecular responses to carcinogenic H. pylori versus a cagA- mutant strain using a gerbil model of gastric cancer within the context of iron depletion.