基于MITF途径双重下调免疫检查点FGL1和PD-L1的土贝母苷甲类新化合物TBM-19抗肿瘤免疫作用及机制研究

免疫检查点阻断疗法是目前肿瘤免疫治疗领域的热点，FGL1/LAG-3和PD-L1/PD-1已成为肿瘤免疫治疗的有效靶点，研发能双重阻断这两对免疫检查点的小分子药物是下一代肿瘤免疫疗法的新方向。前期研究发现，土贝母苷甲类新化合物TBM-19能通过转录途径同时下调肿瘤细胞中FGL1和PD-L1的表达，在荷瘤小鼠中也显示出较好的抗肿瘤活性。本项目拟在此原创性工作基础上，以MITF参与TBM-19降解FGL1和PD-L1的新发现为依据，深入研究：（1）TBM-19下调FGL1和PD-L1的表达及增强T/NK细胞的杀伤活性；（2）TBM-19调控MITF转录活性及相关的信号转导机制；（3）鉴定TBM-19的直接靶蛋白；（4）多种移植瘤小鼠模型评价TBM-19的抗肿瘤效果及对肿瘤浸润性免疫细胞的激活作用，为将TBM-19研发成双重下调FGL1和PD-L1的新型小分子肿瘤免疫治疗药物奠定坚实的基础。

Immune checkpoint blockage therapy has become a current topic and the most promising approache in the field of cancer immunotherapy. Fibrinogen-like protein 1(FGL1)/lymphocyte-activation gene 3 (LAG-3) and programmed cell death protein-1 (PD-1) /programmed cell death ligand-1 (PD-L1) are key targets in cancer immune therapy, but current antibody-based drugs against these pathways have inherent drawbacks that may limit their effectiveness. Therefore, small molecules inhibitors that disrupt FGL1/LAG-3 and PD-1/PD-L1-mediated tumor tolerance are highly desirable..During the screening program for natural small molecules immune checkpoint inhibitors, we identifided Tubeimoside derivative TBM-19 as a new regulator of FGL1and PD-L1 expression in cancer cells. Our primary results demonstrated that TBM-19 has potent anti-tumor activity by degradation of FGL1 and PD-L1 expressed on the tumor cells. Meanwhile, we also found that TBM-19 down-regulated FGL1 and PD-L1 by inhibition of the transcription activity of MITF. However, how TBM-19 regulates FGL1 and PD-L1expression through MITF-dependent pathway remains unknow. In this study, we will demonstrate the effect of TBM-19-induced FGL1and PD-L1 degradation and the cytotoxity of co-cultured T /NK cells, delineate the molecular mechanism by which TBM-19 regulates MITF activity through AMPK-mTOR, PKC-GSK-3β and TPL2-ERK signaling pathways, investigate the target protein of TBM-19, evaluate the antitumor effect of TBM-19 in vivo with the use of multiple cellular, molecular biotechnologies and animal models..This study will clarify a new role of TBM-19 in cancer immunotherapies via dual inhibition of FGL1/LAG-3 and PD-1/PD-L1 pathways, and provide a theoretical basis of TBM-19 for the treatment of advanced malignancies.