Mechanisms of Gastric Mucosal Transformation in Hip1r-Deficient Mice

描述(申请人提供)：在这个项目中，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的机制。缺乏亨廷顿相互作用蛋白1相关(Hip1r)的小鼠会发生进行性和多方面的胃细胞转化。Hip1r在壁细胞中含量丰富，在与酸分泌相关的囊泡运输中起着重要作用。我们最近发现，Hip1r基因缺陷小鼠表现为腺体肥大，壁细胞和主细胞丢失，异常粘液颈部细胞显著扩张(粘液腺化生)。这些特征在2个月大的小鼠中广泛存在，在年长的小鼠(6-8个月)中出现不典型增生、化生和最终的胃窦肿瘤。壁细胞丢失导致胃酸分泌受损，胃泌素升高是试图使胃酸正常化的一种稳态反应。我们假设胃泌素的增加是胃酸分泌增加的原因。这将在AIM 1中通过将Hip1r缺陷小鼠与胃泌素缺陷小鼠杂交来进行测试，以辨别这种激素在胃粘膜重塑中的作用。我们的初步研究表明，增殖增加和肥大是胃泌素依赖的。Hip1r缺陷胃的另一个关键特征是炎症。初步数据显示，作为反应的组成部分，广泛的免疫细胞渗透和干扰素γ增加。我们最近将干扰素γ受体的表达定位于粘液颈部细胞，从而将细胞因子信号通路与粘液细胞化生中改变的关键靶细胞联系起来。在目标2中，我们将测试干扰素和免疫细胞(B和T细胞)通过将Hip1r缺陷小鼠与免疫耗竭小鼠品系杂交而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部肿瘤的发展。胃肿瘤的进展与人类的转化事件平行，包括形态原Sonic和India Hedgehog的表达和信号增加。目的3将使用hedgehog报告鼠品系来表征Hip1r基因缺陷小鼠发展为异型增生过程中的hedgehog信号，并使用环多巴胺阻断胃中的信号，以测试增加的hedgehog信号是否有助于粘膜转化。此外，刺猬对肿瘤生长的重要性将在环多巴胺的培养中进行测试。总而言之，这些实验将提供对复杂细胞变化的机械性见解，这些变化通常与壁细胞萎缩和胃酸分泌减少有关。 公共卫生相关性：该项目专注于一种新的小鼠品系，该品系表现出典型的细胞变化，类似于在人类胃癌发展过程中观察到的变化。其目标是确定胃细胞转化的基本机制，并测试它们在肿瘤形成中的作用。因此，这些研究可能为人类胃癌的发展过程提供洞察力，胃癌是全球最常见的癌症死亡原因之一。

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.