MicroRNA383-PD-L1/PD-1通路参与肝癌微环境T细胞耗竭和肿瘤细胞免疫逃逸的机制研究

T cell exhaustion could cause the dysfunction of T cell immune surveillance and immune protection, finally resulting in immune escape of liver cancer cells. Our preliminary study showed that miR-22 could directly negatively regulate Gal-9 expression and the Gal-9/miR-22 axis could influence lymphocytes apoptosis and tumor cells proliferation. In tumor microenvironment, PD-1 and Tim3 could co-express on exhausted T cells. PD-1/PD-L1 is a couple of negative immune costimulate molecule. In tumor microenvironment, PD-L1 expressed on tumor cells binds to PD-1 on tumor infiltrate lymphocytes (TILs). The interaction between PD-1 and PD-L1 causes an inhibitory signal that results in reduction of cytokine secretion and apoptosis of effector cells, negatively regulates Th1-type immunity, and induces tumor immune tolerance and immune evasion. Our preliminary study showed that miR-383 was downregulated in liver cancer cell lines and PD-L1 expression would be negatively regulated by miR-383 at the posttranscriptional level. In this project, we intend to study the expression level and clinical significance of microRNA-383 in liver cancer, validate its target regulation to PD-L1, and then investigate the mechanism of the microRNA383-PD-L1/PD-1 axis in inducing CD8+T cell exhaustion and mediating immune evasion. This study would provide a novel target for liver cancer immunotherapy.

T细胞耗竭可引起T细胞免疫保护与免疫监视功能障碍，最终导致肝癌细胞免疫逃逸。前期实验证实miR-22靶向负调控Gal-9表达，引起共培养的肝癌细胞和T细胞的增殖和凋亡。在肿瘤微环境中，T细胞可同时高表达PD-1和Tim3。程序性死亡分子1及其配体（PD-1/PD-L1）是一对负性共刺激分子，在肿瘤微环境中，肿瘤细胞表面PD-L1与T细胞表面PD-1结合，发挥免疫负调控作用，导致T细胞耗竭，引起肿瘤细胞免疫逃逸。前期实验显示miR-383在肝癌细胞中显著低表达，PD-L1蛋白水平表达可能在转录后水平受到miR-383的负性调控。本课题拟从microRNA角度出发，研究miRNA-383在肝癌中的表达和临床意义，验证其与PD-L1的靶向调控关系，并进一步探讨miRNA383-PD-L1/PD-1信号通路引起肝癌微环境中T细胞耗竭，介导免疫逃逸的作用机制，为肝癌免疫治疗提供新的方向。

T细胞耗竭可引起T细胞免疫保护与免疫监视功能障碍，最终导致肝癌细胞免疫逃逸。本项目从microRNA角度出发，研究miRNA-383在肝癌中的表达和临床意义，验证其与PD-L1的靶向调控关系，并进一步探讨miRNA383-PD-L1/PD-1信号通路引起肝癌微环境中T细胞耗竭，介导免疫逃逸的作用机制，发现（1）肝癌中PD-L1表达升高，miR-383 表达降低；（2）miR-383与PD-L1存在靶向调控关系，miR-383通过直接与PD-L1 3’UTR结合，在转录后水平下调PD-L1的表达；（3）miR-383-PD-L1途径影响共培养体系中CD8+ T淋巴细胞的凋亡与活性，以及肿瘤细胞的凋亡与迁移，可能参与肿瘤细胞逃逸。本项目的研究结果为肝癌个体化治疗与免疫治疗，改善肝癌患者预后提供理论依据。