CXCL1募集髓源性抑制细胞重塑微环境促进胃癌进展的机制研究

Related research about interaction of tumor with the microenvironment is expected to provide a new approach to tumor therapy. Non-resolving inflammation is an important characteristic of tumor microenvironment. Our previous research found that CXCL1 was upregulated in gastric cancer cells when stimulated by inflammation. We further systemically studied the role of CXCL1/CXCR2 in lymphatic metastasis of gastric cancer from the perspective of tumor microenvironment. It was reported that CXCL1 can recruit MDSC to promote tumor progression. Pre-experimental results has confirmed that CXCR2 is expressed in MDSC, and CXCL1 play an important role in the recruitment of MDSC via CXCR2 in gastric cancer microenvironment. But the mechanism and significance remain to be fully elucidated. Therefore, we propose that CXCL1 released by tumor cells recruits MDSC which leads to the remodeling of tumor microenvironment and thus promote the progression of gastric cancer. This project will firstly obtain further evidence that MDSC can be recruited by CXCL1 derived from gastric cancer. Furthermore, we plan to elucidate the mechanism of remodeling microenvironment by recruited MDSC. On the one hand, we study the positive feedback effect of MDSC recruited by microenvironment on gastric cancer cells. On the other hand, we explore the molecular mechanism how CXCL1/CXCR2 pathway exerts immunosuppressive function on macrophages and T cells in the microenvironment mediated by promoting the activation of MDSC. This project is expected to provide a theoretical basis for developing a new therapy for gastric cancer that using CXCR2 antagonists or neutralizing antibodies to destroy tumor-induced immunosuppression.

肿瘤与微环境相互作用的研究，有望为肿瘤治疗提供新的途径。非可控性炎症是肿瘤微环境的重要特征，前期发现胃癌细胞在炎症刺激下产生CXCL1，我们进一步从微环境角度系统研究了CXCL1/CXCR2在胃癌淋巴转移中的作用。文献报道CXCL1能够趋化髓源性抑制细胞（MDSC）促进肿瘤进展。预实验证实MDSC表达CXCR2，CXCL1是胃癌微环境募集MDSC的重要因素，但作用机制和意义未明。由此，我们提出：肿瘤细胞表达CXCL1募集MDSC，重塑肿瘤微环境，促进胃癌进展。本项目拟进一步获得胃癌表达CXCL1募集MDSC的证据；然后阐明募集的MDSC重塑肿瘤微环境的机制，一方面研究微环境募集的MDSC对胃癌细胞的正反馈作用；另一方面探讨CXCL1/CXCR2信号促进MDSC活化对微环境巨噬细胞和T细胞发挥免疫抑制功能的分子机制。这有望为胃癌开发出新的疗法提供理论基础，为胃癌微环境的靶向治疗提供新的策略。

背景：PD-1/PD-L1获批用于晚期胃癌 (gastric cancer,GC)的三线治疗。尽管针对PD-1/PD-L1的免疫疗法在肿瘤方面取得了临床进展，但仍有相当一部分胃癌患者对治疗无反应。有证据表明，骨髓来源的抑制细胞（myeloid-derived suppressor cells，MDSCs）在肿瘤组织中的聚集与PD-1耐药性有关。本研究旨在分析MDSCs在胃癌组织聚集以及导致PD-1耐药的分子机制。.主要研究内容：采用流式分析外周血MDSCs比例。免疫组化分析胃癌组织CXCL1表达和MDSCs（CD11b）的表达。Transwell 实验评估CXCL1对PMN-MDSCs迁移的影响。Western-Blotting研究了S100A8/A9对胃癌细胞CXCL1表达的影响。通过流式评估CD8+T细胞在MDSCs共培养或者S100A8/A9刺激后代谢特征。构建小鼠皮下肿瘤模型，流式分析MDSCs在皮下瘤、脾脏、外周血的改变。.结果：胃癌患者外周血总MDSCs及PMN-MDSCs的比例显著高于健康者外周血。在患者的外周血和肿瘤组织中，CXCL1的表达与MDSCs（CD11b）的表达呈正相关。在体外来自胃癌细胞的CXCL1可以促进PMN-MDSCs迁移。而PMN-MDSCs分泌的S100A8/A9可以通过TLR4/p38 MAPK/NF-κB 通路刺激胃癌细胞CXCL1表达。而且，S100A8/A9经过TLR4/AKT/mTOR通路导致CD8+T细胞耗竭。在小鼠模型中，CXCR2拮抗剂SB225002抑制了皮下瘤的生长，降低了在皮下瘤、脾脏、外周血PMN-MDSCs的比例。最后，SB225002和抗PD-1联合治疗进一步抑制了肿瘤生长及降低了皮下瘤PMN-MDSCs的浸润，增强了CD8+T细胞浸润及其功能。.科学意义：CXCL1诱导PMN-MDSCs在胃癌组织聚集。PMN-MDSCs通过S100A8/A9反馈促进胃癌细胞CXCL1表达，同时通过S100A8/A9导致CD8+T细胞耗竭，从而促进胃癌进展。