GPR35: Role in Colonic Inflammation and Oncogenesis

描述(由申请人提供)：对微生物区系的炎症反应被认为是人类结直肠癌(CRC)的起始和/或进展的因素。然而，微生物区系成员和结肠癌发生之间的分子联系还没有明确的定义。人类结肠厌氧细菌，产肠毒素脆弱类杆菌(ETBF)，是脆弱芽孢杆菌的一个分子亚型，能产生一种有效的金属蛋白酶毒素，称为脆弱芽孢杆菌毒素(BFT)。ETBF是一种通过诱导选择性致癌的Th17免疫反应而在小鼠模型中形成结肠癌的有效诱导剂。ETBF结肠癌的发生需要BFT的表达。BFT通过结合定位于结肠上皮细胞(CEC)的特定受体来激活CEC中的几个癌前信号通路。然而，BFT CEC受体及其与BFT诱导的致癌信号、结肠炎和结肠肿瘤发生的关系仍有待阐明。通过消减阵列和shRNA策略，G蛋白偶联受体GPR35被确定为BFT受体。这一提议将检验一种假设，即GPR35是被BFT劫持的CEC受体，是结肠癌发生的关键因素。GPR35已知在结肠高表达，先前与胃癌诱导有关，从而在常见微生物区系成员与结直肠癌发病机制之间提供了直接的分子联系。我们将验证这一假设，并进一步定义GPR35如何在BFT诱导的CEC癌信号转导中发挥作用，使用敲除和敲入CEC策略加上GPR35和ç-arrestin KO小鼠模型。GPRCs是人类基因组中最大的细胞表面受体家族，也是新药发现的强大靶点。因此，确定GPR35或其异构体在结肠癌发生中的作用可能会促进人类结直肠癌的预防和/或治疗。

DESCRIPTION (provided by applicant): Inflammatory responses to the microbiota are proposed as contributory to the initiation and/or progression of human colorectal cancer (CRC). However, molecular links between members of the microbiota and colon carcinogenesis are poorly defined. The human colon anaerobic bacterium, enterotoxigenic Bacteroides fragilis (ETBF), is a molecular subtype of B. fragilis that produces a potent metalloprotease toxin called the B. fragilis toxin (BFT). ETBF is a potent inducer of colon tumorigenesis in a murine model through induction of a selective procarcinogenic intracolonic Th17 immune response. ETBF colon tumorigenesis requires BFT expression. BFT activates several procarcinogenic signaling pathways in colonic epithelial cells (CEC) by binding to a specific receptor localized to CECs. However, the BFT CEC receptor and its relationship to BFT-induced oncogenic signaling, colitis and colon tumorigenesis remain to be elucidated. Through subtraction array and shRNA strategies, GPR35, a G protein-coupled receptor (GPCR), is now identified as the putative BFT receptor. This proposal will test the hypothesis that GPR35, known to be highly expressed in the colon and previously linked to gastric cancer induction, is the CEC receptor hijacked by BFT and a critical contributor to colon carcinogenesis, thereby, providing a direct molecular link between a common microbiota member and CRC pathogenesis. We will test this hypothesis and further define how GPR35 contributes to BFT-induced CEC oncogenic signaling using knockout and knock-in CEC strategies plus GPR35 and ß-arrestin KO murine models. GPRCs represent the largest family of cell surface receptors within the human genome and powerful targets for new drug discovery. Thus, establishing a role for GPR35 or its isoforms in colon carcinogenesis may advance the prevention and/or therapy of human CRC.