CCR2 mediated inflammation and gut microbiota in promoting intestinal cancer

 描述（由申请人提供）：结直肠癌（CRC）与伴有白细胞浸润增加的炎症密切相关。CCR 2是一种七跨膜G蛋白偶联趋化因子受体，介导多种生物学功能，包括与其配体CCL 2（MCP 1）结合后的白细胞趋化性。CCR 2在外周血单核细胞/巨噬细胞以及活化的T细胞、B细胞、未成熟树突细胞和肥大细胞上表达。肿瘤细胞中CCL 2的高表达与几种类型的人类癌症的转移增加和预后不良非常相关。近年来，动物模型研究表明，CCL 2-CCR 2轴在结肠肿瘤的发生发展中起重要作用。我们的初步数据显示，与ApcMin/+小鼠相比，ApcMin/+（一种自发性肠癌小鼠模型）背景下的CCR 2-/-小鼠发生的小肠和结肠肿瘤显著更少且更小，并显示出显著的生存优势。此外，CCR 2-/-ApcMin/+中的息肉显示出减少的肿瘤浸润F4/80+细胞，减少的炎性分子（例如，IL-1β，SOCS 1），与ApcMin/+小鼠相比，细胞凋亡和CD 8水平增加。有趣的是，炎性细胞因子IL-23和IL-17在CCR 2-/-ApcMin/+中显著降低。我们的肠道微生物群分析显示，与ApcMin/+小鼠相比，CCR 2-/-ApcMin/+小鼠中促进肿瘤的拟杆菌属显着减少。 基于这些初步数据，我们假设CCR 2/CCL 2介导的肿瘤相关巨噬细胞（TAM）和Th 17细胞的募集调节肿瘤微环境中的炎症和微生物群以促进肠道肿瘤，并且阻断CCR 2-CCL 2轴将降低肿瘤负荷。为了验证这一假设，我们提出了两个具体目标。在AIM 1中，我们将确定在肠肿瘤发生过程中CCR 2对IL-23（TAM，DC）和IL-17（Th 17，Th 17 δ T细胞）产生细胞的募集和活化的需求。在AIM 2中，我们将确定肠道微生物区系对CCR 2依赖性IL-23和IL-17产生的影响，以促进肠道肿瘤发生。目前的提案还将检查现有CCR 2抑制剂在结肠癌进展中的疗效，以将我们的基本观察转化为临床前模型。确定癌症背景下免疫系统-微生物群之间的分子，细胞机制和复杂的相互关系将对我们对肠道致癌作用的基本理解以及开发新的治疗策略的潜力产生强烈影响。

 DESCRIPTION (provided by applicant): Colorectal cancer (CRC) is strongly associated with inflammation accompanied by increased infiltration of leukocytes. CCR2, a seven transmembrane G-protein coupled chemokine receptor, mediates several biological functions including chemotaxis of leukocytes upon binding to its ligand, CCL2 (MCP1). CCR2 is expressed on peripheral blood monocytes/macrophages as well as on activated T-cells, B-cells, immature dendritic cells and mast cells. Elevated expression of CCL2 in tumor cells is very well correlated with increased metastasis and poor prognosis in several types of human cancers. Recently, it was shown in animal models that CCL2-CCR2 axis play an important role in promotion of colon tumorigenesis. Our preliminary data showed that CCR2-/- mice in the ApcMin/+ (a spontaneous intestinal cancer mouse model) background developed significantly fewer and smaller size small intestinal and colon tumors and showed substantial survival advantage compared to ApcMin/+ mice. Further, polyps in CCR2-/-ApcMin/+ displayed decreased tumor infiltrating F4/80+ cells, decreased inflammatory molecules (e.g., IL-1β, SOCS1), increased apoptosis and CD8 levels compared to ApcMin/+ mice. Interestingly, inflammatory cytokines IL-23 and IL-17 were significantly reduced in CCR2-/-ApcMin/+. Our gut microbiota analysis revealed that tumor promoting Bacteroides genus are significantly reduced in CCR2-/-ApcMin/+ mice compared to ApcMin/+ mice. Based on these preliminary data we hypothesize that CCR2/CCL2 mediated recruitment of tumor associated macrophages (TAMs) and Th17 cells modulate inflammation and microbiota in the tumor microenvironment to promote intestinal tumors and blocking CCR2-CCL2 axis would reduce the tumor burden. To test this hypothesis we propose two specific aims. In AIM 1 we will determine the requirement of CCR2 for recruitment and activation of IL-23 (TAMs, DCs) and IL-17 (Th17, ɣδ T-cells) producing cells during intestinal tumorigenesis. In AIM 2, we will determine the influence of gut microflora on CCR2 dependent production of IL-23 and IL-17 to promote intestinal tumorigenesis. The current proposal will also examine the efficacy of existing CCR2 inhibitors in colon cancer progression to translate our basic observation in pre-clinical models. Determining the molecular, cellular mechanisms and complex inter-relationship between immune system-microbiota in the context of cancer will have a strong impact on our basic understanding of intestinal carcinogenesis as well as potential for developing novel therapeutic strategies.