癌旁肠道粘膜中巨噬细胞促进结直肠癌进展的机制研究

Mucosal immunity plays a key role in the progression of intestinal tumor. Local invasion of colorectal cancer is highly associated with the immunosuppressive microenvironment in peritumoral intestinal mucosa. Our previous results showed higher accumulation of macrophages secreting IL-10 and functionally tending to be M2 macrophages in peritumoral intestinal mucosa. Higher expression of CXCL12, upregulated by IL-6 and exosomes derived from tumor, in peritumoral intestinal mucosa is correlated with markers of M2 macrophages and would polarize macrophages into M2 macrophages in peritumoral intestinal mucosa. Therefore, we hypothesize that tumor would active CXCL12-CXCR4 signaling pathway to accumulate M2 macrophages and further build immunosuppressive microenvironment in peritumoral intestinal mucosa and promote local invasion of CRC. However, the mechanism of this process is still unclear. This project explores the accumulation, function and mechanism of M2 macrophages in peritumoral microenvironment through analyzing samples from colorectal cancer patients, mouse orthotopic model of colorectal cancer and CD11b-Cre/CXCR4fl/fl mouse model by using RNA-sequencing, atomic force microscope and drug-packaging microparticles and at the same time illuminates relationship of intestinal tract and tumor progression. New therapies targeting macrophages in peritumoral intestinal mucosa and rebuilding peritumoral immune microenvironment will be raised to treat colorectal cancer patients clinically.

肠道粘膜免疫在肿瘤进展中发挥重要作用，结直肠癌局部侵袭与癌旁粘膜免疫抑制微环境密切相关。我们前期研究发现，高分泌IL-10的巨噬细胞在结直肠癌旁粘膜中浸润较多，功能表现为M2型巨噬细胞；CXCL12在癌旁组织中高表达，与M2型巨噬细胞标志物相关；肿瘤来源的IL-6和外泌体促进CXCL12上调。因此，推测肿瘤激活CXCL12/CXCR4通路，促进癌旁粘膜M2型巨噬细胞聚集，进而塑造癌旁免疫抑制微环境，促进结直肠癌局部侵袭，目前具体机制尚未清楚。本研究利用组学、可视化、囊泡递送药物等技术，通过结直肠癌患者标本、原位成瘤小鼠模型和CD11b-Cre/CXCR4fl/fl小鼠模型等，体内外研究M2型巨噬细胞在癌旁粘膜中累积、功能及机制，揭示肠道这一特殊免疫器官与肿瘤进展的关系，探索靶向M2型巨噬细胞控制结直肠癌局部侵袭的新策略，为临床治疗结直肠癌提供新方案。

肠道粘膜免疫在肿瘤进展中发挥重要作用，结直肠癌发生发展与粘膜免疫抑制微环境密切相关。在本项目的资助下，我们从“空间特征”角度发现了：M2型巨噬细胞在癌旁组织中高表达且预示不良预后；结直肠肿瘤通过外泌体携带EPAS1激活CXCL12/CXCR4通路，招募M2型巨噬细胞至癌旁,促进肿瘤侵袭。靶向CXCR4阻止M2型巨噬细胞聚集，抑制结直肠癌局部侵袭。同时，我们从“时间特征”角度发现了：晚期结直肠癌患者PD-1+CD8+T细胞表达水平较早期患者低，是由于晚期患者巨噬细胞通过IL-6联合IL-8抑制T细胞PD-1表达。在此基础上，我们还进行了与肿瘤微环境及肿瘤治疗相关工作，结果发现：MDSC上GPR84表达促进其抑制功能，靶向GPR84可有效促进PD-1单抗敏感性；纳米负载的吲哚胺2,3-双加氧酶1抑制剂可增强CAR-T细胞功能；化疗通过HMGB1促进PD-1膜蛋白内化抑制PD-1表达；长链非编码RNA lncNDEPD1通过miR-3619-5p调控CD8+T细胞中PD-1的表达；TRAIL通过诱导PD-L1的表达促进上皮间质化的转变；调节性T细胞通过TGF-b/NF-kB/IL6/STAT3信号通路促进胶质瘤细胞干性；cxcl9修饰的CAR-T细胞增强免疫细胞浸润和抗肿瘤疗效；牛磺酸通过增强CD8+T细胞功能来增强PD-1单抗的抗肿瘤功效；肿瘤相关成纤维细胞通过IL-6/外泌体mir-21激活的STAT3信号诱导单核细胞骨髓来源的抑制细胞生成，促进顺铂耐药；萝卜硫素通过调节PD-1/PD-L1通路增强嵌合抗原受体T细胞的抗肿瘤反应；GasderminE介导的CAR-T细胞焦亡引发细胞因子释放综合征。我们还对目前肿瘤微环境中脂质代谢、瘤内菌群及肿瘤免疫关键分子如IFN-γ、IL-33/ST2等进行了综述相关探讨，并分析了结直肠癌免疫治疗耐药的机制。以上相关研究工作为全面解析肿瘤免疫微环境，寻找肿瘤治疗相关靶点，提高肿瘤患者免疫治疗现状提供依据。