IL-33/ST2途径介导肿瘤浸润T淋巴细胞的聚集、代谢和功能的机制研究

Introducing the right inflammation to the tumor microenvironment by expressing appropriate cytokines should help further improvement of the aggregation, activation, metabolism and function of tumor infiltrating T lymphocytes and it might be an effective strategy for tumor immunotherapy. In the previous study, we had found that the expression of IL-33 and ST2 mRNA in cancer tissues was significantly lower than that in adjacent normal tissues, the expression of IL-33 mRNA was significantly associated with overall survival of patients suffering from NSCLC. The expression of IL-33 in cancer cells potently inhibited tumor growth and metastasis, and IL-33 significantly up-regulated the CCL20 expression of activating CD8+ T cells in vitro. Based on these findings, by using clinical, in vitro and in vivo animal experiments, first of all, we will further determine whether IL-33/ST2 signal can recruit circulating DC and enhance the recruitment and activation of tumor antigen specific CD8+ T cell to the tumor microenvironment by CCL20/CCR6 pathway, then the role of IL-33/ST2 signal in promoting CD8+T cell metabolism by stimulating mTOR dependent on CCL20 and subsequently inhibit tumor progression will be studied. In addition, the expression, function and significance of CD4+ST2+Foxp3+Treg in the antitumor immunity mediated by IL-33 will be analyzed. However, such studies will provide insights of potential applications in tumor immunotherapy, that is cytokine-mediated immune therapy of cancer should provide new opportunities for enhancing the immune “checkpoint”-based approach.

一些细胞因子通过适度激发肿瘤微环境的炎症反应，促进肿瘤浸润T淋巴细胞的聚集活化、代谢改善与效应发挥，是肿瘤免疫治疗的有效策略。申请者前期发现IL-33/ST2在人非小细胞肺癌肿瘤组织下调表达且其表达与患者生存期相关，肿瘤局部引入的IL-33显著抑制肿瘤的生长转移，IL-33体外激发明显上调CD8+T细胞CCL20的表达。本项目以此为切入点，以非小细胞肺癌为研究对象，结合临床、体外和动物实验，首先探讨IL-33是否通过CCL20/CCR6途径招募体内循环DC并激发肿瘤抗原特异性CD8+T细胞在肿瘤微环境的募集活化，激活mTOR信号调整T细胞的代谢而介导抗肿瘤效应；继而深入探讨CD4+ST2+Foxp3+Treg这群新的调节性T细胞在IL-33介导的抗肿瘤免疫应答中的表达、作用及意义，为以IL-33联合免疫卡控点分子抗体阻断的肿瘤免疫治疗策略提供新的理论基础。

适度激发肿瘤微环境的炎症反应，提高肿瘤的免疫原性，有助于增强肿瘤免疫应答。一些炎性细胞因子，如IL-1家族成员IL-33可以改变肿瘤微环境，有望加强以免疫卡控点分子为靶点的肿瘤免疫治疗的疗效，深入理解和认识IL-33在T细胞介导的抗肿瘤免疫应答中的作用机制有利于其在肿瘤免疫治疗中的转化应用，具有临床转化应用的实际价值。鉴此，本研究首先在抗原特异性的CD4+Th9细胞在过继性细胞免疫治疗中通过CCL20/CCR6信号通路发挥更有效的抗肿瘤效应的基础上，探讨在Th9极化培养条件下，IL-33对人外周血单个核细胞(PBMCs)和小鼠脾脏细胞中纯化的CD4+T细胞活化、分化和效应的影响。结果表明，IL-33显著上调人CD4+Th9细胞IL-9、IFN-γ、Granzyme A、IL-17A以及转录因子PU.1，IRF4和趋化因子CCL20及趋化因子受体CCR6的表达；同时IL-33显著上调小鼠CD4+Th9细胞IL-9、IFN-γ和Granzyme A的表达，所获结果为将IL-33作为CD4+Th9细胞抗肿瘤免疫应答的调节因子运用于过继性细胞免疫治疗提供了理论依据和新策略。进而探讨了细胞因子IL-33联合免疫卡控点分子PD-1单克隆抗体阻断介导肿瘤微环境中抗肿瘤免疫应答的效应机制。结果表明，细胞因子IL-33联合PD-1免疫卡控点阻断能够增强肿瘤微环境中CD4+T淋巴细胞和CD8+T淋巴细胞的增殖，促进CD4+T淋巴细胞、CD8+T淋巴细胞在肿瘤组织的浸润，分泌表达IFN-γ、GZ-B、perforin等效应分子杀伤肿瘤细胞，增强机体抗肿瘤免疫应答；同时，该联合疗法能够通过抑制体内髓系来源抑制细胞（MDSC）重新刺激活化T淋巴细胞，使其恢复机体效应功能，从而显著抑制荷瘤小鼠肿瘤的生长，并且延长其生存期，所获结果为以细胞因子IL-33 为物质基础的肿瘤联合免疫治疗提供了新的思路和理论依据。