Control of Epithelial Proliferation by the Microbiota

描述（由申请人提供）：在胃肠道癌症的发生和发展过程中，肠道微生物群影响上皮细胞周期调节和干细胞动力学的分子机制，在我们的知识中存在一个关键的空白。这一差距代表了科学进步的障碍，因为在解决这一问题之前，对肠道微生物群与宿主之间生态失调所导致的疾病的解释将继续超出我们的理解范围。我们的长期目标是确定细胞信号通路，细菌群落结构，以及介导微生物群对人类健康影响的微生物产物。本提案的目的是确定微生物群的扰动如何影响肠干细胞（ISC）的更新，并通过扩展肿瘤的发生或进展-最终，如何故意操纵微生物群可能提供治疗策略。根据我们的初步数据，我们的中心假设是高度适应宿主的微生物群的特定成员（特别是乳酸菌）共同进化，通过诱导ROS的产生来促进肠道细胞增殖，然后调节细胞

DESCRIPTION (provided by applicant): There is a critical gap in our knowledge regarding the molecular mechanisms by which the intestinal microbiota influence epithelial cell cycle regulation and stem cell dynamics during the initiation and progression of GI cancers. This gap represents a barrier to scientific progress because, until it is addressed, an explanation for conditions resulting from dysbiosis between the gut microbiota and the host will continue to be beyond our understanding. Our long-term goal is to identify the cellular signaling pathways, the bacterial community structure, and the microbial products that mediate the influences of the microbiota on human health. The objective of this proposal is to identify how perturbations to the microbiota influence intestinal stem cell (ISC) turnover, and by extension tumor initiation or progression -and ultimately, how deliberate manipulation of the microbiota may offer a therapeutic strategy. Based on our preliminary data, our central hypothesis is that specific members of the highly host adapted microbiota (particularly lactobacilli) have co-evolved to facilitate intestinal cell proliferation by inducing the generation of ROS which then regulate cell signaling in the gut epithelium. Given that a subset of the microbiota possess potent pro-proliferative potential, we further hypothesize that altered, absolute or relative numbers of the microbes will have consequent effects on epithelia growth dynamics, and particularly in cases of intestinal injury, may play a role in intestinal tumor initiation and progression. The rationale fo this hypothesis is the well-established notion that physiological generation of low levels of ROS by the action of host NADPH oxidases in distinct subcellular domains act as critical second messengers in multiple signaling networks. In addition, our published and preliminary data identify well- characterized oncogenic cell signaling pathways that are modulated by bacterial-induced ROS generation. Furthermore, it is well-established that physiological generation of low levels of ROS in distinct subcellular domains act as critical second messengers in multiple signaling networks due to their ability to reversibly oxidize low pKa cysteines ("sulfur switches") of specific sensor target proteins. Based on these compelling preliminary data generated by our research group, the central hypothesis will be tested in three specific aims; 1) Characterize the signaling pathways that mediate microbiota-induced stem cell proliferation, 2) Identify the influence of manipulated microbiota in model epithelial early neoplasia, and 3) Identify symbiotic bacteria and bacterial communities that induce redox dependent cell signaling. Our approach will employ, ex-vivo enteroid model, knockout mice, a novel redox I-CAT proteomic technique, and a highly innovative genetically tractable Drosophila model whose biology can be manipulated to a far greater extent than mammalian models. The outcomes of these investigations will have an important positive impact on public health because of direct implications to idiopathic intestinal cancers. The investigation is also relevant to the mission of NIDDK/NIH by addressing preventative interventions for these conditions.