蛋白激酶D1调控免疫检查点分子PD-L1促进口腔鳞癌免疫逃逸的临床潜力研究

Cancer cells exploit the expression of the programmed death-1 (PD-1) ligand 1 (PD-L1) which results in the destruction of T-cell-mediated immunosurveillance. Thus, it is crucial to elucidate mechanisms of PD-L1 expression to predict the efficacy of cancer immunotherapy on cancer cells. Protein kinase D1, is a type of kinase that can catalyze the phosphorylation or serine of threonine residues on various protein substrates, as a regulator of the PD-L1 protein. The applicant confirmed that PKD1 regulates hypoxic metabolism through hypoxia-inducible factor 1(HIF-α) and glycolytic enzymes in oral cancer cells, and studies have confirmed that HIF-α upregulate PD-L1 under hypoxia condition. However, it is still lack of direct evidence that to determine whether PKD1 interacts with PD-L1 in oral cancer cells, and it is of great significance to understand the regulation mechanism and further research need to be performed. In this proposal, we intent to use oral squamous cell carcinoma, a high incidence of disease in China as the model to study the following: to establish specific expression of PKD1, studying on the role of PKD1 in regulating PD-L1 function; to find out the effect and mechanism of PKD1 ehhances the ability of tumour-specific T cell activity in oral squamous cell carcinoma; to find out the possibility of using PKD1 as a target, the prognostic value of the immune checkpoint inhibitors and the development of immune biomarkers for the prediction of efficacy. The results will reveal the molecular mechanism of PKD1 promotes immune evasion in cancer through PD-L1, and guide the clinical strategy in the treatment of oral squamous cell carcinoma.

癌细胞利用程序性死亡配体-1（PD-L1）破坏T细胞介导的免疫监视，阐明癌细胞中PD-L1表达机制对预测肿瘤免疫疗效至关重要。蛋白激酶D1(PKD1) 是一类能催化多种底物蛋白质上丝氨酸/苏氨酸蛋白残基磷酸化的酶，是PD-L1的关键调节因子。申请人前期研究发表论文提示PKD1调控缺氧诱导因子HIF-1α表达，HIF-1α上调缺氧条件下PD-L1表达已有研究证实，而PKD1在口腔鳞癌中是否与PD-L1直接作用缺鲜有研究，其具体调控机制和意义仍有待诠释。本课题拟以我国高发的口腔鳞癌为模型，建立特异性表达PKD1的细胞系，分析其对PD-L1蛋白的调控作用；解析PKD1在口腔鳞癌诱导肿瘤特异性T细胞耗竭中的效应和机制；探索以PKD1为靶标，抗PD-1/PD-L1免疫疗效预测及预后评价生物标志物的开发。结果将揭示PKD1调控PD-L1促进恶性肿瘤免疫逃逸的精细机制，对口腔鳞癌的临床防治具有指导意义。

蛋白激酶D1(PKD1) 是一类能催化多种底物蛋白质上丝氨酸/苏氨酸蛋白残基磷酸化的酶，是程序性死亡配体-1（PD-L1）的关键调节因子。申请人前期研究发表论文提示PKD1调控缺氧诱导因子HIF-1α表达，HIF-1α上调缺氧条件PD-L1表达已有研究证实，而PKD1在口腔鳞癌中是否与PD-L1直接作用缺鲜有研究，其具体调控机制和意义仍有待诠释。本研究详尽阐述了PKD1调控PD-L1促进口腔鳞癌免疫逃逸的作用及机制。本研究利用免疫组织化学法和Western blot检测PKD1和PD-L1在OSCC细胞和组织与正常细胞和癌旁良性组织中的表达，阐明了PKD1和PD-L1在OSCC组织中表达明显高于癌旁良性组织，PKD1与OSCC肿瘤分期具有相关性。其次，本研究探索了PKD1对PD-L1蛋白的调控作用，研究发现PKD1参与了PD-L1表达的调控，可通过降低PKD1表达，减少PD-L1，显著降低体内外对肿瘤特异性T细胞活性的抑制。接着，该课题研究了PKD1调控OSCC细胞中PD-L1表达可能的调节机制，发现PKD1是AKT信号通路调节PD-L1表达的关键激酶，PKD1上游信号通路对OSCC细胞PD-L1分子表达具有调节作用。最后，本项目研究了PKD1沉默对OSCC增殖的影响，通过构建动物模型，发现PKD1小分子抑制剂CRT0066101对C3H小鼠肿瘤的生长有一定的抑制作用。综上所述，本研究结果详细诠释了PKD1是维持PD-L1表达所必需的，解析了PKD1增强了表达PD-L1的OSCC细胞抑制T细胞活化的能力；阻断PKD1表达(基因水平和小分子抑制剂)能够重新激活免疫细胞抗癌作用，能有效提高机体对抗OSCC的能力。探索以PKD1为OSCC免疫治疗中的一个分子靶标，帮助临床医生预测是否患者能够获益于检查点抑制剂这类免疫疗法，建立OSCC防治的新策略。