Role of TLR4 in Colitis Associated Neoplasia

描述（由申请人提供）：拟议的项目旨在了解炎症相关瘤形成的分子基础。IBD患者继续需要结肠切除术治疗异型增生，主要是因为我们无法阻止IBD进展为癌症。我们以前的工作已经证明，先天性免疫信号的toll样受体4（TLR 4）的重要贡献结肠炎相关癌症（CAC）的发展。我们确定TLR 4为促进结肠恶性肿瘤的癌基因。我们已经表明，TLR 4在UC相关的异型增生和几乎所有的CAC中过表达。我们发现，TLR 4缺陷的动物（TLR 4-/-小鼠）受到保护，免受结肠炎相关的肿瘤，并产生了绒毛蛋白启动子驱动转基因肠道TLR 4过表达（V-TLR 4）的小鼠。这些小鼠非常容易出现结肠炎相关的肿瘤。从机制上讲，我们已经表明TLR 4通过PI 3激酶激活结肠上皮细胞中的β-连环蛋白信号传导促进肿瘤形成。我们目前的初步数据表明，TLR 4驱动Lgr 5+干细胞在肠肿瘤和正常粘膜中的扩增，表明TLR 4信号传导在体内驱动该模型中的干细胞自我更新。我们还表明，UC粘膜和TLR 4介导的炎性肿瘤在小鼠模型中的特征在于S100 A8/A9表达骨髓源性抑制细胞（MDSC）的浸润。在当前的提议中，我们将检验以下假设：TLR 4信号传导在恶性上皮转化中起自分泌作用，并且通过MDSC的活化起旁分泌作用以刺激β-连环蛋白活化、上皮细胞增殖和癌症干细胞扩增。这是追求以下具体目标：1）确定TLR 4信号传导在炎性瘤形成中肠干细胞活化中的作用。使用我们与干细胞报告基因Lgr 5-EGFP小鼠杂交的各种表达TLR 4的动物模型，我们将研究在体内炎症和肿瘤转化期间，是否需要TLR 4来扩增谱系定型祖细胞和结肠癌干细胞。2)确定TLR 4信号在促进结肠上皮细胞干细胞中的作用。我们将使用原代结肠样培养物来测试TLR 4信号传导是否改变培养物中原代结肠干细胞的表型（生长、出芽）。我们将使用结肠癌细胞系来测试TLR 4信号传导是否在体外促进癌症干细胞表型并使用异种移植物在体内增加致瘤性。3)确定S100 A8/9+ MDSC是否驱动TLR 4依赖性β-连环蛋白活化、干细胞活化和肿瘤发生。我们将确定S100 A8/9 MDSC是否是肠干细胞扩增和CAC所必需的。我们将测试S100 A8或9是否以TLR 4依赖性方式激活结肠上皮中的β-连环蛋白。将分离人UC相关MDSC并研究其在体外刺激结肠上皮中β-连环蛋白信号传导的能力。本文提出的工作旨在为后续人类研究提供机制依据，以靶向先天免疫信号传导作为阻止UC/炎症进展为发育异常的手段。

DESCRIPTION (provided by applicant): The proposed project aims to understand the molecular underpinnings of inflammation-associated neoplasia. Patients with IBD continue to need colectomies for dysplasia largely because of our inability to halt IBD progression to cancer. Our previous work has demonstrated that innate immune signaling by toll-like receptor 4 (TLR4) contributes importantly to the development of colitis-associated cancer (CAC). We identified TLR4 as an oncogene which promotes colonic malignancy. We have shown that TLR4 is over-expressed in UC- associated dysplasia and in almost all CACs. We showed that animals deficient in TLR4 (TLR4-/- mice) are protected from colitis-associated neoplasia and have generated a mouse in which the villin promoter drives transgenic intestinal TLR4 overexpression (V-TLR4). These mice are highly prone to colitis-associated neoplasia. Mechanistically, we have shown that TLR4 promotes neoplasia by activating ß-catenin signaling through PI3 kinase in colonic epithelial cells. We present preliminary data that show that TLR4 drives expansion of Lgr5+ stem cells in both intestinal neoplasia and in normal mucosa suggesting that TLR4 signaling is driving stem cell self-renewal in this model in vivo. We also show that UC mucosa and TLR4- mediated inflammatory neoplasia in mouse models are characterized by an infiltrate of S100A8/A9 expressing myeloid-derived suppressor cells (MDSCs). In the current proposal we will test the hypothesis that TLR4 signaling plays both an autocrine role in malignant epithelial transformation and a paracrine role through activation of MDSCs to stimulate ß-catenin activation, epithelial cell proliferation and cancer stem cell expansion. This is pursued i the following specific aims: 1) Determine the role of TLR4 signaling in activation of intestinal stem cells in inflammatory neoplasia. Using our various TLR4 expressing animal models crossed to stem cell reporter Lgr5-EGFP mice we will investigate if TLR4 is required for expansion of lineage committed progenitors and of colon cancer stem cells during inflammation and neoplastic transformation in vivo. 2) Determine the role of TLR4 signaling in promoting stemness of colonic epithelial cells. We will use primary colonoid cultures to test if TLR4 signaling alters the phenotype (growth, budding) of primary colon stem cells in culture. We will use colon cancer cell lines to test whether TLR4 signaling promotes a cancer stem cell phenotype in vitro and increases tumorgenicity in vivo using xenografts. 3) Determine if S100A8/9+ MDSCs drive TLR4-dependent ß-catenin activation, stem cell activation, and tumorigenesis. We will determine whether S100A8/9 MDSCs are required for intestinal stem cell expansion and CAC. We will test if S100A8 or 9 activate ß-catenin in colonic epithelia in a TLR4-dependent manner. Human UC-associated MDSCs will be isolated and studied for their ability to stimulate ß-catenin signaling in colonic epithelia in vitro. The work proposed herein aims to provide the mechanistic justification for subsequent human studies to target innate immune signaling as a means to halt progression UC/inflammation to dysplasia.