Role of Bacteria in Colitis-Associated Colon Cancer

描述（由申请人提供）：结直肠癌（CRC）是美国男性和女性中第三常见的癌症，也是癌症相关死亡的第二大原因。慢性肠道炎症已被确定为结直肠癌发展的重要风险因素，因此患有炎症性肠病（IBD）的个体处于高风险中。微生物群在CRC发展中的作用尚未明确定义。迄今为止，研究主要集中在先天传感器和相关宿主反应在结直肠癌发展中的作用。虽然研究宿主中的先天传感器是信息丰富的，但确定微生物组在CRC发展中的作用将需要一种更直接的方法，这种方法可以干扰微生物群落并测量微生物和宿主的后果。本申请的目的是确定肠道细菌的选择性组如何促进IllO-/-小鼠中CRC的发展。我们假设特定的细菌实体通过表达微生物遗传毒性产物促进CRC的发展，导致宿主基因组不稳定性增强和肿瘤性病变的形成。我们已经制定了这一假设的基础上，我们的初步研究结果表明，特定的细菌类群扩大在荷瘤小鼠，而这些没有检测到在无肿瘤小鼠。此外，虽然大肠杆菌NC 101（E. coli）和粪肠球菌（Enterococcus faecalis，E. faecalis）单相关的IL 10-/-小鼠中，肿瘤数量在E. coliNC 101组与E.粪便最后，我们确定了大肠杆菌NC-101中的pks基因组岛，该基因组岛编码一组聚酮合成酶基因，这些基因已被证明可产生遗传毒性产物大肠杆菌素。该基因组岛诱导细胞周期阻滞和组蛋白2AX丝氨酸139磷酸化（？H2AX）。我们计划测试我们的中心假设，并实现本申请的总体目标，具体目标如下。1)确定炎症对微生物群落结构和功能的影响; 2）确定大肠杆菌NC 101介导的结直肠癌发展的机制。 在这些研究完成后，我们希望已经确定了与CRC发展相关的微生物群落，并确定了增强对这种病理易感性的微生物基因产物。由于CRC是美国癌症死亡的第二大原因，并且是长期溃疡性结肠炎和克罗恩氏结肠炎的主要并发症，因此我们的研究结果将非常重要，因为它们将确定可以靶向预防/治疗炎症诱导的CRC的新途径。此外，从宏基因组研究中获得的基础知识有望推动CRC研究的总体领域向前发展。

DESCRIPTION (provided by applicant): Colorectal cancer (CRC) is the third most common form of cancer in men and women in the United States and the second leading cause of cancer-related death. Chronic intestinal inflammation has been identified as an important risk factor for the development of colorectal cancer and consequently individuals suffering from inflammatory bowel diseases (IBD) are at high risk. The role of the microbiota in the development of CRC has not been clearly defined. To date, research has largely focused on the role of innate sensors and associated host responses in the development of colorectal cancer. While studying innate sensors in the host is informative, establishing the role of the microbiome in the development of CRC will require a more direct approach that perturbs the microbial community and measures the consequences for both microbes and host. The objective of the present application is to determine how selective group of commensal bacteria promote development of CRC in Il10-/- mice. We hypothesize that specific bacterial entities promote the development of CRC through expression of microbial genotoxic products, resulting in enhanced host genomic instability and formation of neoplastic lesions. We have formulated this hypothesis based on our preliminary findings showing that specific bacterial taxa expand in tumor-bearing mice, whereas these were not detected in tumor-free mice. Furthermore, although colitis severity at the histological and molecular level is similar between Escherichia coli NC101 (E. coli) and Enterococcus faecalis (E. faecalis) monoassociated Il10-/- mice, tumor numbers were strongly enhanced in the E. coli NC101 group compared to E. faecalis. Finally, we identified the pks genomic island in E.coli NC-101, which encodes a set of polyketide-synthetase genes that have been shown to produce a genotoxic product, colibactin. This genomic island induces cell cycle arrest and histone2AX serine 139 phosphorylation (?H2AX). We plan to test our central hypothesis and fulfill the overall objective of this application with the following specific aims. 1) Identify the impact of inflammation on microbial community structure and function and 2) Determine the mechanisms of E.coli NC101- mediated development of colorectal cancer. At the completion of these studies, we expect to have identified the microbial communities associated with the development of CRC and determined microbial gene products that enhanced susceptibility to this pathology. Since CRC is the second leading cause of cancer death in the U.S. and is a major complication of long standing ulcerative colitis and Crohn's colitis, our findings will be important because they will identify novel pathways that can be targeted to prevent/treat inflammation-induced CRC. In addition, the basic knowledge gained from metagenomic studies is expected to move the general field of CRC research forward.