胃癌治疗新靶点CXCL1/CXCR2信号通路的研究

Gastric cancer (GC) is the second leading cause of cancer-related death in China. Targeted therapy has potential to improve patient survival. CXCL1/CXCR2 pathway regulates tumor-stromal interactions and targeted inhibitor of this pathway increases survival in animal model of PDAC. In GC, protein expressions of CXCL1 & CXCR2 are higher in advanced stage tumors and significantly corelate with poor prognosis. Previous studies in our lab have found that CXCL1/CXCR2 axis enhances migration and tube formation of lymphatic endothelial cells in GC and promotes tumor growth and dissemination. Therefore, we hypothesize that GC cells secrete CXCL1 which induces chemotaxis and modulates phenotype and function of CXCR2 expressed stromal cells, and CXCL1/CXCR2 axis choreographs cell behavior to shape the tumor microenvironment and promote tumor growth and dissemination. In present grant proposal, we will use clinical GC tissues to investigate infiltration of stromal cells and macrophages, expression of CXCR2/CXCL1 proteins, and relationships between these protein expressions and patient survival. We will use IHC, qPCR, ELISA to characterize the connection between CXCL1 expression and phenotype and function of fibroblast cells/macrophages/endothelial cells in vitro. Then, we evaluate the effect of stromal cells with or without CXCR2 expression on tumor formation and tumor features in vivo. Additionally, we will investigate the efficacy of CXCR2 inhibitor alone and in combination with cytotoxic agents on GC xenograft models. We aim to delineate the mechanism of action of CXCL1/CXCR2 pathway in GC, and explore new target of therapeutic intervention, and improve survival for GC patients.

胃癌是我国第二位肿瘤杀手，联合靶向药物个体化治疗是改善预后的希望。研究发现CXCL1/CXCR2通路介导肿瘤间质微环境，在胰腺癌模型中阻断该通路可以延长生存期；在胃癌中该通路与肿瘤转移、分期和预后密切相关，调控淋巴管内皮细胞增生和功能。我们推测胃癌细胞通过CXCL1/CXCR2通路招募和改造间质细胞，促进自身生长和播散。本课题将利用临床标本预筛CXCL1/CXCR2通路调控的间质细胞；应用IHC、qPCR和ELISA体外研究CXCL1表达对细胞表型和功能的作用，并研究作用机制；通过皮下移植瘤模型研究间质细胞CXCR2表达对胃癌细胞成瘤性和瘤特征的影响；揭示胃癌细胞分泌CXCL1,依赖与间质细胞表面CXCR2结合来调控间质细胞表型和功能，促进胃癌增生和转移；最后，利用胃癌移植瘤模型，研究该通路阻断剂联合细胞毒药物抑制胃癌增生和转移的效果。本研究旨在开辟胃癌治疗新靶点，改善胃癌患者预后。

胃癌是我国肿瘤第二位杀手，靶向治疗有望改善其预后。本项目探讨CXCL1/CXCR2作为胃癌治疗新靶点的价值，明确胃癌是否通过CXCL1/CXCR2调控肿瘤间质微环境促进生长和转移。我们通过共培养和体内外实验证实胃癌细胞分泌TNFa促进肿瘤相关巨噬细胞（TAM）分泌CXCL1和CXCL5诱导胃癌细胞发生EMT，从而促进胃癌转移；CXCL1结合胃癌细胞表面CXCR2活化STAT3信号通路，从而上调VEGF表达，促进肿瘤血管新生，从而促进胃癌生长和转移。而且，我们通过构建高转移潜能胃癌细胞株筛选转移相关的趋化因子受体，发现与胃癌转移最相关的趋化因子受体是CXCR2和CXCR4，进一步研究发现CXCR2与CXCR4存在正反馈通路协同促进胃癌转移：CXCL1/CXCR2可以上调P65，P65与CXCR4启动子结合，促进CXCR4表达；CXCL12/CXCR4上调STAT3，STAT3与CXCR2启动子结合，促进CXCR2表达。我们通过体外实验和裸鼠淋巴结转移瘤模型证实同时阻断CXCR2与CXCR4通路抑制胃癌转移效果最好。最后，我们利用临床标本发现TAM、CXCL1、CXCL5、CXCR2和CXCR4表达均与胃癌患者预后相关，同时表达CXCR2和CXCR4的患者预后最差。因此，本研究阐明了胃癌细胞通过趋化因子和其受体调控微环境促进增生和转移，趋化因子受体之间有协同作用，同时阻断CXCR2与CXCR4才能更好地抑制胃癌转移。研究结果为开发趋化因子和其受体作为胃癌治疗新靶点提供理论依据，为胃癌的治疗提供新的思路。