Role of Iron and B-Catenin Activation in Gastric Carcinogenesis

幽门螺杆菌是已知的胃腺癌的最强危险因素，而胃腺癌是全球癌症相关死亡的第二大原因，但只有一小部分感染者会发展成这种恶性肿瘤。一个增加癌症风险的幽门螺杆菌决定因素是cag IV型分泌系统（T4SS），它将微生物癌蛋白GagA转运到上皮细胞中。我们在项目2中获得的初步数据表明，在细胞内传递GagA激活了b -连环蛋白，并且在幽门螺杆菌感染的上皮细胞中激活β -连环蛋白的结果是过度增殖。我们的研究还表明，缺铁增强了幽门螺杆菌激活β -连环蛋白的能力。我们现在用胃组织病理学核心A表明，铁的消耗以caga依赖的方式加速了沙鼠幽门螺杆菌诱导的癌症的发展。蛋白质组学Core B的二维（20）DIGE/质谱分析鉴定了从缺铁沙鼠和缺铁沙鼠中分离的幽门螺杆菌菌株中33种差异丰富的蛋白质，其中一些蛋白质介导微生物粘附和cag T4SS的功能。这些结果直接为项目3中具有挑战性的新研究提供了依据，这些研究表明，从缺铁沙鼠身上获得的幽门螺杆菌菌株或在体外缺铁条件下生长的幽门螺杆菌菌株表现出更强的组装cag T4SS、转运GagA和诱导促炎细胞因子表达的能力。我们还开发了新的幽门螺杆菌感染模型，更密切地概括发生在胃生态位内的事件。胃类器官是三维的，单层上皮器官样结构，为研究宿主幽门螺杆菌在临床前模型中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、鉴定并感染了幽门螺旋杆菌的胃类器官。我们的假设是缺铁增加了幽门螺杆菌依赖性肿瘤的发生。我们将通过以下目标进行测试：

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.