干预肿瘤免疫检查点蛋白PD-L1的药物再发现研究

以靶向PD-1/PD-L1为代表的肿瘤免疫治疗近年来取得了重大进展，但该类抗体药物仍存在有效率低、严重不良反应发生率高等问题，因此，有望克服这些缺点的小分子抑制剂研究已成为该领域的热点。我们前期发现了若干可显著抑制PD-L1的药物，通过药物作用前后基因表达谱、亚克隆细胞差异蛋白等实验研究，发现他汀类、列净类和芳基丙酸类药物分别在基因转录、蛋白降解和内膜系统穿梭等三个不同环节对PD-L1进行调控。本课题将进一步研究上述药物对转录因子KLF12转录激活PD-L1的调控方式，去泛素化酶USP32介导PD-L1泛素化降解，以及影响PD-L1蛋白在细胞内膜系统间穿梭的分子机制，并基于新靶点筛选模型开展化合物结构优化研究。本项目不仅将发现这三类药物的新作用机制，为这些“老药”应用于肿瘤免疫治疗提供实验依据，还有望从中发现调控PD-L1的新靶点，为基于免疫检查点的抗肿瘤小分子药物研发提供思路。

Tumor immunotherapy, especially the therapy targeting PD-1/PD-L1 immune checkpoint proteins, has been made great progress in recent years. However, the problems such as low efficiency and high incidence of severe adverse reactions are commonly observed in using these antibody drugs in clinic. Thus, the development of small molecule inhibitors that are expected to overcome these shortcomings has aroused general interest in this field. In our pilot study, we have identified some drugs that significantly inhibit cell membrane expression of PD-L1 by using a cell-based screening assay. By utilizing the gene expression profiles, proteomics techniques and related cellular experiments, we interestingly found that Statins, Gliflozins and Aryl propanoic acid analogs were respectively involved in disturbing the transcription, protein stability and membrane translocation of PD-L1. This study will mainly focus on the regulation of transcriptional activation of PD-L1 by Statins on KLF12, a novel transcription factor, regulating PD-L1; the ubiquitination-based degradation of PD-L1 mediated by deubiquitinase USP32 that affected by Gliflozins; the molecular mechanisms of membrane translocation of PD-L1, which inhibited by Aryl propanoic acid analogs. Moreover, the compound structure optimization study will be carried out based on the newly identified target found among the researches mentioned above. The novelty and significance of this study lies on several aspects: this study will illustrate the new mechanism of these drugs regulating on PD-L1, providing experimental evidence for the application of these "older drugs" for tumor immunotherapy. The current study might have the chance to identify the new target regulating PD-L1, which will be benefit for developing the potential small molecule inhibitors for immunotherapy.