CCR2 mediated inflammation and gut microbiota in promoting intestinal cancer

 描述(申请人提供)：结直肠癌(CRC)与炎症密切相关，并伴有白细胞的增加。CCR2是一种七跨膜G蛋白偶联趋化因子受体，通过与其配体CCL2(MCP1)结合，介导多种生物学功能，包括白细胞的趋化作用。CCR2表达于外周血单核/巨噬细胞以及活化的T细胞、B细胞、未成熟树突状细胞和肥大细胞。在几种类型的人类癌症中，肿瘤细胞中CCL2的高表达与转移增加和预后不良密切相关。近年来，动物模型研究表明CCL2-CCR2轴在促进结肠肿瘤发生中起重要作用。我们的初步数据显示，与ApcMin/+小鼠相比，在ApcMin/+(一种自发性肠癌小鼠模型)背景下的CCR2-/-小鼠发生的小肠和结肠肿瘤明显更少和更小，并显示出显著的生存优势。此外，与ApcMin/+小鼠相比，CCR2-/-ApcMin/+小鼠的息肉表现出肿瘤浸润性F4/80+细胞减少，炎性分子(如IL-1β，SOCS1)减少，细胞凋亡和CD8水平增加。有趣的是，炎症细胞因子IL-23和IL-17在CCR2-/-ApcMin/+组显著降低。我们的肠道微生物区系分析显示，与ApcMin/+小鼠相比，CCR2-/-ApcMin/+小鼠的促肿瘤类杆菌属显著减少。基于这些初步数据，我们假设CCR2/CCL2介导的肿瘤相关巨噬细胞(TAMs)和Th17细胞的募集调节了肿瘤微环境中的炎症和微生物区系，从而促进了肠道肿瘤的发生，阻断CCR2-CCL2轴将减轻肿瘤负担。为了检验这一假设，我们提出了两个具体目标。在目标1中，我们将确定在肠道肿瘤发生过程中，CCR2对IL-23(TAMS，DC)和IL-17(Th17，ɣδT细胞)产生细胞的募集和激活的需求。在AIM 2中，我们将确定肠道微生物区系对CCR2依赖的IL-23和IL-17产生的影响，以促进肠道肿瘤的发生。目前的提案还将检查现有CCR2抑制剂在结肠癌进展中的有效性，以转化我们在临床前模型中的基本观察。在癌症的背景下，确定免疫系统-微生物区系之间的分子、细胞机制和复杂的相互关系将对我们对肠癌发生的基本理解以及开发新的治疗策略的潜力产生强烈的影响。

 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.