Toll- Like Receptor-Complex in Intestinal Epithelial Cells

项目负责人/主要研究者（最后一名、第一名、中间名）： 阿伯Maria T. 3 R56 AI052266-07S1 摘要在上一个项目期间，人们对Toll样受体（TLR）信号通路有了大量的了解。我们在本项目中所做的题为“肠上皮细胞中的Toll样受体复合物”的工作有助于确定TLR信号传导在肠上皮中的作用。基于我们自己的研究和其他人最近的工作，我们希望测试TLR 4将先天免疫信号与APC依赖性散发性结肠癌联系起来的假设。具体来说，我们计划专注于结肠上皮细胞和肠道巨噬细胞中的这一新途径，因为这两种重要细胞类型之间存在密切的相互作用。所提出的工作是我们在前一时期工作的直接延伸，该工作涉及肠道先天免疫系统，但现在将这些途径连接起来以了解结直肠肿瘤的机制。大量的研究已经阐明了导致结肠癌的分子途径。在85%的散发性结肠癌中发现了腺瘤性结肠息肉病（APC）基因和/或Wnt信号通路的突变。APC突变导致结肠癌的部分机制是通过诱导考克斯-2和激活表皮生长因子受体（EGFR）信号传导。我们已经表明，这两种途径都被肠上皮细胞（IEC）中的TLR 4激活。APC途径与癌症似乎在结肠中特别相关，与其他上皮细胞不同，但APC突变不成比例地在结肠癌中达到顶峰的原因尚不清楚。细菌和TLR信号转导与结直肠癌的发展有关。在初步数据中，我们发现TLR 4在大多数散发性结肠癌中过表达。这些令人信服的发现迫使我们了解TLR 4如何参与散发性结肠癌的发展。基于我们的初步数据，我们假设TLR 4信号通过几种不同的机制支持APC依赖性结直肠癌的发展。首先，TLR 4可以与APC相互作用以激活靶基因如考克斯-2。其次，TLR 4既是EGFR信号传导的靶标，也能够激活EGFR，导致增殖失调。最后，上皮细胞的TLR 4表达导致肿瘤相关巨噬细胞的募集，这是促进肿瘤生长所必需的。研究TLR 4提供了一个框架，以了解肠道中的先天免疫系统如何无意中促进癌症的发展，作为其正常修复作用的延伸。这些研究提供了一个额外的途径，通过它来预防易感宿主的结肠癌和治疗结肠癌患者。这项提案是我们赠款四年半期间所做工作的自然延伸。

Program Director/Principal Investigator (Last, First, Middle): Abreu. Maria T. 3 R56 AI052266-07S1 ABSTRACT During the last project period, a great deal has been learned about toll-like receptor (TLR) signaling. The work we have performed on the present project entitled "Toll-like receptor complex in intestinal epithelial cells" has helped to define the role of TLR signaling in the intestinal epithelium. Based on our own research and recent work by others, we wish to test the hypothesis that TLR4 links innate immune signaling to APCdependent sporadic colon cancer. Specifically, we plan to focus on this rather new pathway in the colonic epithelial cell and the intestinal macrophage because of the close interaction between these two important cell types. The work proposed is a direct extension of our work in the previous period which dealt with the gut innate immune system, but which now connects these pathways to understand mechanisms of colorectal neoplasia. A great deal of research has elucidated the molecular pathways that result in colon cancer. Mutations in the adenomatous polyposis coli (APC) gene andlor the Wnt signaling pathway are found in 85% of sporadic colon cancers. Part of the mechanism by which APC mutations result in colon cancer is through induction of COX-2 and activation of epidermal growth factor receptor (EGFR) signaling. We have shown that both of these pathways are activated by TLR4 in intestinal epithelial cells (lEC) 2. The APC pathway to cancer seems to be particularly relevant in the colon, as distinct from other epithelia, but the reason why APC mutations disproportionately culminate in colon cancer are unknown. Bacteria and TLR signaling have been implicated in the development of colorectal cancer. In preliminary data, we show that TLR4 is over-expressed in most sporadic colon cancers. These compelling findings force us to understand how TLR4 participates in the development of sporadic colon cancer. Based on our preliminary data, we hypothesize that TLR4 signaling supports the development of APC-dependent colorectal cancers through several distinct mechanisms. First, TLR4 may interact with APC to activate target genes such as COX-2. Second, TLR4 is both a target of EGFR signaling as well as capable of activating EGFR resulting in dysregulated proliferation. Finally, TLR4 expression by the epithelium leads to the recruitment of tumor-associated macrophages, which are required to promote tumor growth. Studying TLR4 provides a framework to understand how the innate immune system in the gut may inadvertently promote the development of cancer as an extension of its normal role in repair. These studies offer an additional avenue by which to prevent colon cancer in susceptible hosts and treat patients with colon cancer. This proposal is a natural extension of the work performed during the four and a half years of our grant.