Escherichia coli and Colorectal Carcinogenesis

描述（由申请人提供）：在美国，大肠癌导致的死亡人数比除肺以外的任何其他器官的死亡人数都多。尽管取得了巨大的进展，但启动和促进结肠肿瘤进展的因素尚未完全了解。我们的初步数据表明，大肠杆菌，特别是E。大肠杆菌菌株，具有E.大肠杆菌附着和消失（EAE）基因与人类结肠癌相关。此外，我们还发现，附加和删除E。大肠杆菌（AEEC）菌株特异性下调错配修复（MMR）蛋白MLH1和MSH2的表达。这些蛋白质在DNA复制过程中防止突变，某些遗传性和散发性结直肠癌患者在这些基因中存在突变。我们的初步微阵列数据还表明，AEEC下调DKK 1，Wnt通路的抑制剂，在细胞增殖中起重要作用，在另一种遗传形式的结直肠癌中被不适当地激活。AEEC还下调先天免疫反应的几个关键组分。总之，这些数据提供了诱人的证据，提出了以下新的假设：AEEC通过T3SS依赖性抑制宿主细胞过程，抵御微生物定植，DNA损伤和不受调控的细胞生长，在结肠癌发生中发挥作用。这项提案的目的是收集更多的数据，以确定这一假设是否成立。我们计划确定是否需要特定的AEEC蛋白来下调MMR蛋白的表达，以及我们是否可以检测到感染的人结肠癌细胞系中MMR活性的降低和感染的人肿瘤组织中基因组不稳定性增加的证据。我们计划确定我们是否可以验证有关在mRNA和蛋白质水平上抑制DKK 1和先天免疫应答激活剂的微阵列数据。我们还计划收集正常和肿瘤的人类结肠组织，我们可以尝试验证和进一步表征AEEC和结肠肿瘤之间的关联。这些研究的结果将表明进一步的研究是否是合理的，以确定AEEC在结直肠癌发生中的作用。最终，这项工作可能对癌症死亡率的主要原因之一的诊断，预防和治疗产生深远的影响。公共卫生相关性：大肠癌导致的美国人死亡人数超过除肺以外的任何其他器官。尽管在破译导致这些癌症的基因变化方面取得了巨大进展，但关于这个过程是如何开始的，还有很多东西需要了解。我们已经发现，某些类型的E。大肠杆菌被发现附着在大肠癌上，这些细菌可以干扰肠细胞修复DNA错误的能力。这些错误在癌症的发展中也很重要。我们希望进一步探索这些细菌干扰这种和其他预防癌症的途径的能力，以确定某些细菌菌株是否可能在癌症发展中发挥作用。

DESCRIPTION (provided by applicant): Cancers of the large intestine cause more deaths in the United States than those arising in any other organ but the lung. Despite tremendous progress, the factors that initiate and promote the progression of neoplasia in the colon are incompletely understood. Our preliminary data suggest that Escherichia coli and in particular E. coli strains that have the E. coli attaching and effacing (eae) gene are associated with colon carcinoma in humans. Furthermore, we have found that attaching and effacing E. coli (AEEC) strains specifically down-regulate expression of mismatch repair (MMR) proteins MLH1 and MSH2. These proteins protect against mutations during DNA replication and patients with certain inherited and some with sporadic colorectal cancer have mutations in these genes. Our preliminary microarray data also indicate that AEEC down-regulate DKK1, an inhibitor of the Wnt pathway, which plays an important role in cell proliferation and is inappropriately activated in another inherited form of colorectal cancer. AEEC also down-regulate several critical components of the innate immune response. Together, these data provide tantalizing evidence to suggest the following novel hypothesis: AEEC play a role in colonic carcinogenesis through T3SS-dependent inhibition of host cell processes that defend against microbial colonization, DNA damage and unregulated cell growth. The goal of this proposal is to gather additional data to determine whether this hypothesis is tenable. We plan to determine whether specific AEEC proteins are required to down-regulate MMR protein expression and whether we can detect decreased MMR activity in infected human colon carcinoma cell lines and evidence of increased genomic instability in infected human neoplastic tissue. We plan to determine whether we can verify the microarray data regarding inhibition of DKK1 and activators of the innate immune response at the mRNA and protein level. We also plan to accrue a collection of normal and neoplastic human colonic tissue with which we can attempt to verify and further characterize the association between AEEC and colonic neoplasia. The results of these studies will indicate whether further research is justified to determine the role of AEEC in colorectal carcinogenesis. Ultimately this work could have profound implications for the diagnosis, prevention and treatment of a one of the leading causes of cancer mortality. PUBLIC HEALTH RELEVANCE: Cancers arising in the large intestine kill more Americans than those from any other organ but the lung. Despite tremendous progress in deciphering the genetic changes that lead to these cancers, there is much to learn about how the process begins. We have found that certain types of E. coli bacteria are found attached to cancers of the large intestine and that these same bacteria can interfere with the ability of intestinal cells to repair mistakes in DNA. These same mistakes are important in the development of cancer. We wish to explore further the ability of these bacteria to interfere with this and other pathways that protect against cancer to determine whether certain strains of bacteria may play a role in cancer development.