高浓度维生素C对PD-L1的表达调控及其联合免疫检查点抑制剂治疗肝癌的作用研究

Although high concentration of vitamin C has killing effect on a wide variety of tumors including liver cancer, its role in tumor immunity, especially the immune checkpoint PD-L1, is unclear. Immune checkpoint blocker therapy can bring some tumor patients long-term survival benefit, but the low efficacy of single drug is a highlighted issue that should be imminently solved. As PD-L1 expression level is one of the important indicators for the sensitivity of immune checkpoint blocker therapy, our preliminary experiment found that high concentration of vitamin C could induce PD-L1 expression in liver cancer cells. Therefore, this study will employ the subcutaneous xenograft tumor model, orthotopic liver cancer model, chemically induced liver cancer model in mice, transgenic mouse model of liver cancer, human and mouse liver cancer cell lines, human primary liver cancer cells to evaluate the regulation role of high concentration of vitamin C on in the expression of PD-L1 in liver cancer, and further test the effect of high concentration of vitamin C combined with immune checkpoint blockers (PD-1/PD-L1 antibody) on the treatment of liver cancer in vitro and in vivo. It provides a potential novel combination therapy for improving the efficacy of tumor immunotherapy.

高浓度维生素C虽然对多种肿瘤包括肝癌，均具有杀伤作用，但是其对肿瘤免疫，尤其是免疫检查点PD-L1的调控尚不明确。免疫检查点抑制剂疗法虽然能给部分肿瘤患者带来长期生存获益，但其单药有效率低是目前亟待解决的突出问题。我们的预实验发现高浓度维生素C可诱导肝癌细胞PD-L1表达升高，PD-L1的表达水平是免疫检查点疗法敏感性的重要指标。因此，本研究将结合免疫健全小鼠的皮下异种移植瘤模型、原位肝癌模型、化学诱导小鼠肝癌模型、肝癌转基因小鼠模型以及体外人/小鼠肝癌细胞系和人原代肝癌细胞，先明确高浓度维生素C对肝癌PD-L1表达的调控作用，并阐明相关分子机制；进一步从体内和体外两个层次探究高浓度维生素C联合免疫检查点抑制剂(PD-1/PD-L1抗体)治疗肝癌的作用，为提高肿瘤免疫治疗疗效提供潜在的联合治疗新方案。

免疫检查点抑制剂疗法仅对部分肿瘤患者有效，其单药有效率低及治疗后的耐药是目前亟待解决的关键问题。高浓度维生素C具有抗肿瘤作用，但其对肿瘤免疫和免疫治疗疗效的影响仍不清楚。本项目通过与肝癌经典靶向药索拉非尼相比，明确了高浓度维生素C促进体内肿瘤血管正常化，显著增强抗PD-L1抗体治疗肝癌的疗效；阐明了高浓度维生素C激活肝癌细胞的cGAS，从而促进其产物cGAMP的分泌，激活血管内皮细胞的STING通路，进而导致血管正常化的分子机制；重要的是，STING抑制剂可以逆转高浓度维生素C对抗PD-L1抗体疗效的增强作用。最后，在完成本项目研究内容的基础上，进一步探索发现NAD+代谢调控肝癌细胞PD-L1表达，从而促进肿瘤免疫逃逸；补充NAD+前体物质NMN显著增强抗PD-L1抗体疗效，并逆转肿瘤免疫治疗耐药。总之，本项目拓展了高浓度维生素C和NAD+代谢对肿瘤免疫调控的分子机制，明确了高浓度维生素C和NAD+前体物质NMN对免疫检查点抑制剂的增强作用，为临床改善免疫治疗疗效提供了新的联合治疗策略。项目研究期间，发表标注本基金号的第一作者SCI论文1篇，影响因子31.373分；申报国家发明专利2项；项目申请人于2021年晋升助理研究员；2022年获国家自然科学基金面上项目；2022年获评海军军医大学深蓝工程“启航”人才；培养硕士研究生1名。