Molecular Understanding and Targeting of Determinant Factors in Gastric Tumorigenesis

摘要胃癌是世界第五大常见恶性肿瘤和第三大致死性癌症。 在世界范围内，晚期患者的5年存活率为5-10%。我们研究的长期目标是 基于关键基因分子靶向开发预防和治疗胃癌的新干预措施 胃癌发生中的事件。这一应用是基于一项令人兴奋的发现，即带有绒毛蛋白启动子的小鼠- 被驱动的PPAR-d过表达(Villin-PPAR-d小鼠)自发形成大的侵袭性GC。我们的 已发表的数据显示，PPAR-d在人胃癌组织中上调，这种上调是 与患者预后不良有关。绒毛蛋白启动子在一小部分胃上皮细胞中的活性 被认为是绒毛蛋白阳性的胃祖细胞(V-GPC)。癌症干细胞(CSCs)被认为 通过转化正常的干细胞/祖细胞来驱动肿瘤的形成。我们发现PPAR-d 增强V-GPC的干性，并通过激活PPAR-d-干扰素使V-GPC形成肿瘤- 伽马(IFNG)信令环路。此外，我们还发现1)CCL20的表达上调最明显 2)CCR6+CD45+细胞(CCR6是趋化因子的唯一受体)。 CCL20)较CCR6-CD45+细胞有更高的IFNG mRNA表达。幽门螺杆菌(H. 幽门螺杆菌)是一种人类胃癌的I类致癌物。慢性幽门螺杆菌感染，目前影响近一半的 世界人口，是已知的人类GC的强烈危险因素。幽门螺杆菌感染增加PPAR-d、CCL20和 IFNG反过来促进幽门螺杆菌引起的胃炎症，增强GPC的干性并促进 小鼠和人的胃上皮细胞增殖。幽门螺杆菌是否需要这种PPAR-d过度激活- 诱导的GC在很大程度上是未知的。解决这一知识差距对公众很重要，特别是对 患有慢性幽门螺杆菌感染的人，因为PPAR-d是一种可药物蛋白，对于 激动剂和拮抗剂已经开发出来，PPAR-d激动剂正用于非癌症 适应症(例如，增强肌肉耐力)。因此，我们假设在GPC中PPAR-d过度激活 通过上调PPAR-d-CCL20/CCR6-IFNG信号通路及其分子靶向来推动GC 通路可能成为GC的一种新的干预方式。目标1将确定PPAR-d上调在 成人期V-GPC和LGR5阳性GPC(L-GPC)在胃癌发生中的作用目标2将决定效果 V-GPC和L-GPC中PPAR-d基因缺失/功能丧失在费氏嗜血杆菌诱导的胃癌发生中的作用H. Felis是幽门螺杆菌的近亲，在小鼠身上的作用类似于幽门螺杆菌在人类身上的作用。目标3将 确定PPAR-d-IFNG信号失控的分子机制，并评估 该通路的分子靶向在胃癌发生中的作用。我们期望这项提议能够完成 这不仅为探讨胃癌的分子发病机制提供了新的思路，而且促进了胃癌的发展。 基于机制的GC预防和治疗新方法。

ABSTRACT Gastric cancer (GC) is the fifth most common malignancy and the third most lethal cancer worldwide, with a 5-year survival rate of 5-10% in advanced stages. The long-term goal of our research is to develop novel interventions to prevent and treat gastric cancer (GC) based on molecular targeting of crucial events in GC carcinogenesis. This application is based on an exciting finding that mice with villin-promoter– driven PPAR-d overexpression (villin-PPAR-d mice) spontaneously developed large and invasive GCs. Our published data showed that PPAR-d was upregulated in human GC tissues and this upregulation was associated with poor prognosis of patients. Villin promoter is active in a small subpopulation of gastric epithelial cells that are considered villin-positive gastric progenitor cells (V-GPCs). Cancer stem cells (CSCs) are thought to arise from transformation of normal stem/progenitor cells to drive tumor formation. We found that PPAR-d enhanced the stemness of V-GPCs and enabled V-GPCs to form tumors via activating the PPAR-d–interferon- gamma (IFNG) signaling loop. Furthermore, we also found 1) CCL20 is the most markedly upregulated chemokine by PPAR-d overexpression in V-GPCs, and 2) CCR6+CD45+ cells (CCR6 is the sole receptor of CCL20) have significantly higher IFNG mRNA expression than CCR6-CD45+ cells do. Helicobacter pylori (H. pylori) is a class I carcinogen for human GC. Chronic H. pylori infection, currently affecting nearly half of the world population, is a known strong risk factor for human GC. H. pylori infection increases PPAR-d, CCL20, and IFNG, which in turn promotes H. pylori–induced gastric inflammation, enhances GPCs’ stemness and promotes gastric epithelial proliferation in mice and humans. Whether this PPAR-d overactivation is required for H. pylori– induced GC is largely unknown. Addressing this knowledge gap is important to the public, especially for individuals who suffer from chronic H. pylori infection, because PPAR-d is a druggable protein for which both agonists and antagonists have been developed, and PPAR-d agonists are being used for noncancerous indications (e.g. enhancing muscle endurance). Thus, we hypothesize that PPAR-d overactivation in GPCs drives GC via upregulating the PPAR-d–CCL20/CCR6–IFNG signaling pathway and molecular targeting of this pathway could be a novel intervention modality for GC. Aim 1 will determine the role of PPAR-d upregulation in V-GPCs and Lgr5-positive GPCs (L-GPCs) at adult onset on GC carcinogenesis. Aim 2 will determine the effect of PPAR-d genetic deletion/loss of function in V-GPCs or L-GPCs on H. felis-induced GC tumorigenesis. H. felis is a close relative of H. pylori that has analogous effects in mice to those of H. pylori in humans. Aim 3 will determine the molecular mechanisms underlying dysregulated PPAR-d–IFNG signaling and evaluate the effects of molecular targeting of this pathway on GC carcinogenesis. We expect that completion of this proposal will not only provide new insights into the molecular pathogenesis of GC, but also advance the development of novel mechanism-based approaches for GC prevention and therapy.