Tim-1在CD8+T细胞介导肠癌肿瘤免疫应答中的作用研究

Tim-1 is an important co-stimulatory molecule which contributes to T cell activation, and is mainly expressed on CD4+ T cells. However, our recent data indicated that Tim-1 could also be expressed on tumor infiltrating CD8+ T cells after tumor vaccination. The CD8+ T cell is the major subset of effector cells involved anti-tumor immune response, thus it's important for us to study the contribution and the mechanism of Tim-1 in the enhancement of CD8+ T cell mediated anti-tumor response, which will help improving adoptive T cell therapy of human cancers. Based on our previous data, in this proposal, we aim to further investigate the distribution, the clinical significance and the effector function of Tim-1+CD8+ T cells infiltrating human colorectal cancer tissues. And to study the contribution and the mechanism of Tim-1 in CD8+ T cell-mediated anti-tumor immune response in vitro using various anti-Tim-1 antibodies. We will also study the transcription factors that regulate Tim-1 expression using chromatin immunoprecipitation assay. In addition, the Tim-1 knockout mice and OVA/OT-I model system will be used to determine the contribution of Tim-1 in adoptive cell therapy against colorectal cancer in vivo. Our study will establish the role of Tim-1 in enhancing the effector function of tumor infiltrating CD8+T cell, elucidate the mechanism by which Tim-1 regulates CD8+T cell-mediated anti-tumor immune responses, and provide theoretical and experimental basis for targeting TIM-1 for promoting immunotherapy of cancer.

Tim-1是主要表达在CD4+T细胞并参与T细胞活化的重要协同刺激分子，我们最新的研究表明，在接种肿瘤疫苗的小鼠中Tim-1表达于肿瘤浸润CD8+T细胞。由于CD8+T细胞是杀伤肿瘤的主要效应细胞，研究Tim-1促进CD8+T细胞抗肿瘤效应的作用机制，对提高肿瘤过继细胞治疗的疗效具有重要意义。 本项目拟在前期工作基础上，结合临床样本深入分析Tim-1+CD8+T细胞在肠癌组织中的分布特征、临床意义及效应功能；体外实验采用抗体干预及染色质免疫共沉淀技术，探讨Tim-1在肠癌浸润CD8+T细胞抗肿瘤效应中的作用及调控机制；体内实验应用Tim-1 基因敲除小鼠及OVA/OT-I模型，验证Tim-1介导CD8+T细胞抗肿瘤免疫应答在肠癌过继细胞治疗中的作用。本研究将进一步阐述Tim-1在CD8+T细胞抗肿瘤免疫应答中的作用机制，为Tim-1作为肠癌过继细胞治疗的靶点提供理论依据与实验基础。

TIM-1(T cell immunoglobulin mucin-1，TIM-1)是T细胞免疫球蛋白黏蛋白结构域相关分子家族(TIM)的重要成员，在T细胞活化中起重要作用。我们研究发现在结直肠癌浸润CD8+T细胞中，TIM-1表达水平较癌旁组织显著升高；在RFA肿瘤治疗模型中我们也发现，肿瘤浸润CD8+T细胞中TIM-1表达水平显著上调。同时我们构建TIM-1-CAR-T细胞，结果表明，TIM-1信号可以显著增强CAR-T细胞IL2分泌。本课题组还进一步围绕肿瘤免疫治疗开展了系列研究，具体体现在： (1)、TIM-1信号在CD8+T细胞中的表达可以在肿瘤微环境中有效抗原刺激的情况下被上调，而TIM-1信号可有效增强效应T细胞的功能；(2)、基于PD-1/PD-L1、B7-H3、B7-H4等免疫卡控点的检测及靶向干预，可有效提高特异性肿瘤杀伤细胞的效应功能，通过肿瘤特异抗原筛查及监测确定肿瘤免疫治疗优势人群并建立疗效评估体系，具有重要的临床应用价值；(3)、本研究通过回顾性病例分析及小鼠移植瘤模型的实验研究，证实RFA后期可出现肿瘤浸润T细胞活化后失能、肿瘤微环境中Treg与MDSCs扩增、Th1/Th2应答转化及PD-1/PD-L1表达上调，通过RFA联合PD-1单抗阻断能显著增强肿瘤浸润T细胞的抗肿瘤免疫应答水平，阻止RFA治疗后效应T细胞向调节性T细胞的转化，抑制肿瘤内MDSCs扩增。该项目研究证实PD-L1检测对于筛选结直肠肝转移患者中适宜RFA联合PD-1阻断治疗的优势人群具有重要意义。该项目研究为基于免疫卡控点靶向干预的肿瘤免疫治疗新策略提供了新思路，具有重要临床应用价值。