Mechanisms of Gastric Mucosal Transformation in Hip1r-Deficient Mice

描述（由申请人提供）：在本项目中，我们将使用基因工程小鼠模型来探索进展为胃化生和癌症的细胞变化机制。缺乏亨廷顿蛋白相互作用蛋白1相关（Hip1r）的小鼠会发生胃的进行性和多方面的细胞转化。Hip1r在壁细胞中含量丰富，它对与酸分泌相关的囊泡运输很重要。我们最近确定hip1r缺陷小鼠表现出腺体肥大，顶壁细胞和主细胞的缺失，以及异常粘液颈细胞（粘液腺化生）的显著扩张。这些特征在2个月大的小鼠中普遍存在，在6-8个月大的小鼠中出现发育不良、化生和最终的胃窦肿瘤。壁细胞损失导致酸分泌受损，胃泌素增加是一种试图使酸正常化的稳态反应。我们假设胃泌素的增加是分泌酸的胃增殖增加的原因。这将在AIM 1中进行测试，通过将hip1r缺陷小鼠与胃泌素缺陷小鼠杂交，以确定这种激素在胃粘膜重塑中的作用。我们的初步研究表明，增加的增殖和肥厚是胃泌素依赖的。hip1r胃缺乏的另一个关键特征是炎症。初步数据显示广泛的免疫细胞浸润和增加的干扰素γ作为反应的组成部分。我们最近将干扰素γ受体的表达定位于粘膜颈部细胞，从而将细胞因子信号通路与粘膜细胞化生中发生改变的关键靶细胞联系起来。在Aim 2中，我们将通过杂交hip1r缺陷小鼠到免疫缺失小鼠品系来验证干扰素γ和免疫细胞（B细胞和T细胞）诱导细胞转化的假设。与胃酸分泌部分的转化事件相关的是胃窦区肿瘤的发展。胃肿瘤的进展与人类的转化事件相似，包括形态因子sonic和印度刺猬的表达和信号传导增加。Aim 3将使用hedgehog基因报告小鼠品系来表征hip1r缺陷小鼠向发育不良进展过程中的hedgehog基因信号，并通过使用环巴胺阻断胃中的信号传导，测试hedgehog基因信号的增加是否有助于粘膜转化。此外，将在环巴胺培养中测试hedgehog基因对肿瘤生长的重要性。总之，这些实验将提供复杂的细胞变化的机制见解，通常与胃壁细胞萎缩和低酸分泌有关。

DESCRIPTION (provided by applicant): In this project we will use genetically engineered mouse models to probe mechanisms of cellular changes that progress to gastric metaplasia and cancer. Mice deficient in Huntingtin interacting protein 1 related (Hip1r) develop a progressive and multifaceted cellular transformation of the stomach. Hip1r is abundant in parietal cells where it is important for vesicular trafficking associated with acid secretion. We have recently determined that Hip1r-deficient mice exhibit glandular hypertrophy, loss of parietal and chief cells, and marked expansion of abnormal mucous neck cells (mucous gland metaplasia). These features are widespread in mice as young as 2 months of age, with dysplasia, metaplasia and eventual antral tumors emerging in older mice (6-8 months). Parietal cell loss results in impaired acid secretion and increased gastrin occurs as a homeostatic response to attempt to normalize acid. We hypothesize that increased gastrin is responsible for increased proliferation of the acid-secreting stomach. This will be tested in AIM 1 by crossing Hip1r-deficient mice to gastrin-deficient mice, to discern the role of this hormone in the remodeling of the gastric mucosa. Our preliminary studies demonstrate that increased proliferation and hypertrophy are gastrin-dependent. Another key feature of the Hip1r-deficent stomach is inflammation. Preliminary data shows widespread immune cell infiltrates and increased interferon gamma as components of the response. We have recently localized interferon gamma receptor expression to the mucous neck cells, thus linking cytokine signaling pathways to the key target cell altered in mucous cell metaplasia. In Aim 2 we will test the hypothesis that interferon gamma and immune cells (B and T cells) induce the cellular transformation by crossing Hip1r-deficient mice to immune-depleted mouse strains. Associated with the transformation events in the acid secreting portion of the stomach is the development of tumors in the antral region. The progression to gastric tumors parallels transformation events in the human, including increased expression and signaling of the morphogens sonic and Indian hedgehog. Aim 3 will characterize hedgehog signaling in Hip1r-deficient mice during the progression to dysplasia using hedgehog reporter mouse strains, and test whether increased hedgehog signaling is contributing to the mucosal transformation with the use of cyclopamine to block signaling in the stomach. In addition, the importance of hedgehog for tumor growth will be tested in culture with cyclopamine. Together these experiments will provide mechanistic insights into the complex cellular changes commonly associated with parietal cell atrophy and low acid secretion in the stomach. PUBLIC HEALTH RELEVANCE: This project focuses on a new mouse strain that exhibits classic cellular changes similar to those observed in the development of human gastric cancer. The goal is to define basic mechanisms of stomach cell transformation and test their role in tumor formation. Thus these studies may provide insights into the process of stomach cancer development in human, which is one of the most prevalent causes of cancer death worldwide.