Role of TLR4 and the microbiome in colitis associated neoplasia

摘要 我们试图了解炎症性肠病患者从炎症到肿瘤的发展过程。 疾病(IBD)。通常情况下，患者被诊断为发育不良，并接受结肠切除术，尽管他们会 永远不要患上癌症。我们研究的重点是肠道细菌和先天疾病之间的联系 免疫信号导致结肠炎相关肿瘤。Toll样受体4识别内毒素等 内源性配体存在于发炎的结肠中。我们的研究小组发现，TLR4在 溃疡性结肠炎(UC)患者的炎症和发育不良组织。使用转基因和基因敲除小鼠，我们 已经表明，肠道上皮细胞表达TLR4会产生一个产肠微生物群，能够 传播炎症。在上皮细胞中具有固有活性的TLR4的小鼠表现出显著的增加 上皮细胞增殖和结肠肿瘤增多(AOM-DSS)。我们的初步数据表明，癌症 与WT小鼠的肿瘤相比，来自这些肿瘤的干细胞具有非常不同的转录特征。我们 也显示TLR4驱动的肿瘤增强了肿瘤支持髓系来源的募集 抑制细胞(MDSCs)。TLR4驱动的肿瘤显著上调NADPH氧化酶并增强 产生过氧化氢。过氧化氢和其他活性氧物种有几种生物功能，包括控制 细胞增殖和微生物种群。在目前的提案中，我们假设监管失调 TLR4诱导氧化还原信号，促进干细胞激活并导致肿瘤诱因的选择 微生物组。我们进一步假设，非生物微生物群激活MDSCs促进CAC。这是 具体目标如下：1)分析TLR4介导的氧化还原信号在癌症中的作用 干细胞在CAC中的激活。我们将使用我们的不同动物模型来研究TLR4和NADPH双重氧化酶2 (DUOX2)定义氧化还原信号如何参与TLR4过程中肿瘤干细胞的激活和存活- 推动了肿瘤的发生。2)探讨TLR4介导的氧化还原信号在粘膜上的相互关系 生物失调及其在肿瘤发生中的后果。我们将使用我们的动物模型和 元基因组测序研究氧化还原信号通过DUOX2如何参与TLR4介导 并将使用粘膜相关微生物移植来测试这一致癌作用 无菌小鼠的微生物区系。3)剖析TLR4在塑造MDSCs对 肿瘤发生过程中的驻留微生物群。我们将使用细菌和宿主RNA的双重RNA测序 从肿瘤相关MDSCs和UC患者的MDSCs中确定居民之间的相互作用 微生物区系与肿瘤促进基因在MDSCs中的表达我们还将从功能上描述PRO- 骨髓间充质干细胞对TLR4刺激的致瘤反应包括细胞因子、趋化因子和过氧化氢的产生。 本文提出的工作将为后续的人类研究提供机制上的合理性 TLR4或下游信号分子作为阻止UC/炎症进展到异型增生的手段 和异型增生转化为癌症。

ABSTRACT We seek to understand the progression from inflammation to neoplasia in patients with inflammatory bowel disease (IBD). Often patients are diagnosed with dysplasia and undergo colectomies even though they will never develop cancer. The focus of our studies has been the link between intestinal bacteria and innate immune signaling leading to colitis-associated neoplasia. Toll-like receptor 4 (TLR4) recognizes LPS and other endogenous ligands present in the inflamed colon. Our group has shown that TLR4 is overexpressed in inflamed and dysplastic tissues of ulcerative colitis (UC) patients. Using transgenic and knock-out mice, we have shown that intestinal epithelial expression of TLR4 engenders a colitogenic microbiome capable of transmitting inflammation. Mice with constitutively active TLR4 in epithelial cells show dramatically increased epithelial proliferation and increased colonic tumors (AOM-DSS). Our preliminary data demonstrate that cancer stem cells from these tumors have a very distinct transcriptional profile compared to tumors in WT mice. We also show that TLR4-driven tumors have enhanced recruitment of tumor supporting myeloid-derived suppressor cells (MDSCs). TLR4-driven tumors have dramatic upregulation of NADPH oxidases and enhanced production of H2O2. H2O2 and other reactive oxygen species have several biological functions, including control of cell proliferation and microbial populations. In the current proposal, we hypothesize that dysregulation of TLR4 induces redox signaling, promoting stem cell activation and leading to selection of a tumorigenic microbiome. We further hypothesize that the dysbiotic microbiome activates MDSCs to promote CAC. This is pursued in the following specific aims: 1) Analyze the role of TLR4-mediated redox signaling on cancer stem cell activation in CAC. We will use our diverse animal models for TLR4 and the NADPH dual oxidase 2 (Duox2) to define how redox signaling participates in activation and survival of cancer stem cells during TLR4- driven tumorigenesis. 2) Interrogate the inter-relationship of TLR4-mediated redox signaling on mucosal dysbiosis and the consequences of dysbiosis in tumorigenesis. We will use our animal models and metagenomic sequencing to investigate how redox signaling through Duox2 participates in TLR4-mediated dysbiosis, and will use mucosa-associated microbial transplants to test the tumorigenic effects of this microbiota in germ-free mice. 3) Dissect the role of TLR4 in shaping the response of MDSCs to the resident microbiome during tumorigenesis. We will use dual RNA sequencing of bacterial and host RNA from tumor-associated MDSCs and MDSCs from UC patients to determine the interplay between the resident microbiota and tumor-promoting gene expression in MDSCs. We will also functionally characterize the pro- tumorigenic responses of MDSCs upon TLR4 stimulation including cytokine, chemokine, and H2O2 production. The work proposed herein will provide the mechanistic justification for subsequent human studies to target TLR4 or downstream signaling molecules as a means to halt progression from UC/inflammation to dysplasia and dysplasia to cancer.