糖代谢重编程调控PD-L1/PD-1表达对肿瘤微环境效应T细胞活性的影响及机制

At present, the therapeutic effect of PD-L1/PD-1 monoclonal antibody is not satisfying, but the cause of treatment failure is not clear. In our previous studies, we found that the level of glycolysis was closely related to the activity of PD-L1/PD-1 pathway in bladder cancer cells, and the expression of lactate transporter 4 (MCT4) was high in bladder cancer cells, and T cells were highly expressed MCT1. Is there any correlation between glycolysis and T cell activity and immune escape in bladder cancer cells? We put forward the hypothesis “glucose metabolic reprogramming in tumor cells and their microenvironment can increase the activity of PD-L1/PD-1 pathway. The possible mechanism is the epigenetic regulation of PD-L1/PD-1 pathway molecules can be regulated by lactic acid, which can inhibit the activity of T cells. This may be one of the important factors in the treatment failure of PD-L1/PD-1 monoclonal antibody. The targeted therapy should be enhanced if above mentioned process can be reversed. To test this hypothesis, we first detect the abnormal expression of PD-L1/PD-1 pathway and glucose metabolism related molecules in the clinical samples. Secondly constructing microfluidic chip and discussing the mechanism of glucose metabolism and reprogramming on PD-L1/PD-1 pathway in cancer cells and effector T cell under a co-culture environment. At last, combined targeted small interfering RNA technique was performed to block PD-L1/PD-1 pathway and lactic acid transporter and to investigate its in vivo antitumor effect. Above all things, present research will help to explain the mechanism of bladder cancer and lay the foundation for the novel targeted antitumor therapy.

PD-L1/PD-1单抗治疗效果不理想，原因尚未明确。前期研究发现糖酵解与PD-L1/PD-1通路活性密切相关；且膀胱癌细胞、T细胞分别高表达乳酸转运体4（MCT4）、MCT1。膀胱癌细胞的糖酵解与效应T细胞的活性及肿瘤免疫逃逸之间是否存在关联？我们提出假说“肿瘤细胞及其微环境的糖代谢重编程能够上调PD-L1/PD-1通路的活性从而抑制T细胞免疫活性，其机制是通过乳酸对PD-L1/PD-1通路分子的表观遗传调控；这可能是PD-L1/PD-1单抗治疗不反应的重要因素之一，如能逆转该过程，可增强靶向治疗的疗效”。拟在临床标本中检测PD-L1/PD-1通路分子与糖代谢相关分子的异常表达；构建三维微流控培养体系，探讨膀胱癌细胞与效应T细胞共生环境下，糖代谢竞争和重编程对PD-L1/PD-1通路的影响及其调控机制；利用联合靶向性siRNA技术阻断PD-L1/PD-1通路及MCT4，探讨联合抗瘤效果。

肿瘤微环境糖代谢重编程在肿瘤发生发展中具有重要的作用，前期研究发现糖酵解与PD-L1/PD-1介导的免疫逃逸作用密切相关，但具体调节机制尚未明确。本课题通过构建膀胱肿瘤细胞和CD8+T细胞的共培养体系来模拟肿瘤免疫微环境，同时联合小鼠原位肿瘤模型，探讨糖代谢重编程对PD-L1/PD-1介导的免疫逃逸机制的调节作用，并进一步探究其具体分子机制。结果发现：在肿瘤高效糖酵解导致的低糖微环境下，糖代谢重编程能够通过EGFR/ERK/c-Jun信号通路促进肿瘤细胞PD-L1的高表达，并对CD8+T细胞表现出较强的免疫抑制作用，从而调节肿瘤的免疫逃逸；联合多种通路激活剂及抑制剂进一步确定了该结论的可靠性。通过本课题的实施，确定了肿瘤糖代谢重编程在肿瘤免疫逃逸中的重要作用及具体机制，进一步为膀胱癌的免疫治疗提供了必要的理论依据及临床协同治疗靶点。