结直肠癌肠道免疫微环境对抗肿瘤T细胞PD-1和Tim-3信号通路的调控作用及其机制

A lot of studies showed that tumor-infirltrating lymphocytes in patients with colorectl cancers (CRC) represents a strong independent predictor of relapse and overall survival of , which suggest that anti-tumor immune play a important role in development and progress of CRC. However, the patients with microsatellite stable CRC did not benefit from the administration of PD-1 targeting antibody, which showed impressive results in a number of cancers. Our previous studies found the regulatory roles of Treg of draining lymph nodes and PD-1 signaling pathway in CD8+ T cell respones in CRC. Our recent results suggest that Tim-3 may be a more important inhibitor for CD8+T cells than PD-1. But, all these studies could not explain why anti-PD-1 antibody therapy is ineffective for CRC. Due to its special functions, intestine has a rich lymphoild tissuce and immune cells, as well as a robust immune homeostasis mechanism. We hypothesize that the intestinal immune microenvironment may influence the anti-tumor T cell response by regulating the tumor immune microenvironment. This project will carry on a comprehensive and systematic analysis the expresison and location of PD-1, Tim-3 and their ligands in intestines, tumors and draining lymph nodes. In animal studies, we will study the regulatory roles of the microenvironment of intestines and tumors in PD-1 and Tim-3 signaling pathways of CD8+ T cells ae well as their effects on anti-tumor CD8+ T cell responses. The final goal is to develop the effective immunotherapies for CRC.

大量研究显示肿瘤浸润淋巴细胞是结直肠癌（CRC）复发和患者生存的独立预测指标，说明肿瘤免疫对CRC的发展转归具有重要作用。然后，对多种常见恶性肿瘤具有良好疗效的PD-1抗体免疫治疗，对微卫星稳定型CRC无临床疗效。我们前期研究发现了淋巴结Treg和PD-1信号通路对CRC中CD8+T细胞的调控作用，而且发现Tim-3可能是比PD-1更重要的免疫抑制分子，但这些不足以说明CRC的免疫治疗无效。由于肠道功能独特，具有丰富的免疫系统和强大的免疫稳态机制，我们提出：肠组织免疫微环境会调控CRC组织免疫微环境，影响肿瘤免疫治疗。因此，本项目将系统全面分析人结直肠组织、CRC组织和引流淋巴结中PD-1和Tim-3、及其配体的表达和分布，结合动物实验分析研究肠道和癌组织免疫微环境对CD8＋T细胞PD-1和Tim-3信号通路的调控作用，及其调节抗肿瘤CD8＋T细胞反应的作用及机制，建立有效免疫治疗策略。

结直肠癌是第一个被证明存在免疫监视的人恶性肿瘤，大量研究显示肿瘤浸润淋巴细胞是结直肠癌（CRC）复发和患者生存的独立预测指标。然后，对多种常见恶性肿瘤具有良好疗效的PD-1抗体免疫治疗，对微卫星稳定型CRC无临床疗效。我们系统全面分析了人80多例CRC组织、引流淋巴结和患者外周血中T细胞上免疫检查点受体PD-1、Tim-3、LAG-3、CTLA-4、CD38和CDHLA-DR等的表达，发现Tim-3在CD8+ TIL上几乎全部与PD-1分子共表达，而引流淋巴结和外周血中Tim-3与PD-1分别表达在不同CD8+ T细胞上。PD-1单阳性的CD8+ T细胞细胞因子产生没有显著下降，而Tim-3无论与PD-1共表达还是单独表达，Tim-3+细胞分泌细胞因子的功能均显著下降。这些结果说明结直肠癌肿瘤微环境中CD8+ T细胞功能反应，主要受到Tim-3免疫抑制信号的调控。我们通过杂交瘤技术获得了抗人Tim-3的抗体，但抗小鼠抗体还在制备中。下一步计划研究Tim-3阻断型抗体对结直肠癌的治疗作用。.对PD-1抑制剂治疗反应和不反应的患者进行分析，大量研究结果显示：肿瘤浸润T细胞的数量和分化状态与治疗反应密切相关。为了增强PD-1抑制剂的治疗疗效，我们研发了抗PD-1抗体与IL-21融合蛋白，体外及小鼠体内试验证实，该融合蛋白在发挥PD-1信号阻断作用同时，可以靶向肿瘤特异性T细胞，显著促进抗肿瘤记忆性T细胞反应，极大提高PD-1抗体的肿瘤治疗效果。也制备了人源化PD-抗体与IL-21融合蛋白，目前在转化中。该成果申请了中国及国际专利，文章投稿Nature Communications,在修回中。