不同分子分型胃癌中PD-1，PD-L1基因多态性及蛋白表达与预后的关系及机制研究

The binding of programmed cell death 1 (PD-1) and its ligands (PD-L1) plays a major role in the process of tumor immune escape, though transmits an inhibitory signal to reduce T cell activity. The expression of PD-1, PD-L1 may have associations with the clinical effect of monoclonal antibody drugs and the prognosis of cancer, the inhibitors of PD-1，PD-L1 have became one of the most promising tumor immunotherapy. The patients with advanced or metastatic gastric cancers often have poor prognosis, and for different molecular types of gastric cancer, responses to the immunotherapy are different. Therefore, it’s important to identify the new biomarker for assessing the prognosis and immunotherapy effects in patients of gastric cancer. We use the epidemiology methods and a gastric cancer cohort to clarify the differences of PD-1, PD-L1 expression between different molecular types of gastric cancer, and examine the relationships between PD-1, PD-L1 expression and prognosis of gastric cancer. We also use the genotyping technique to explore the association between PD-1, PD-L1 gene polymorphism and its protein expression. Meanwhile, we use the biostatistics methods and laboratory studies to examine the regulatory mechanism of PD-L1 expression in gastric cancer by JAK-STAT pathway downstream of IFN-γ, Thus, our study will provide insight on successful estimate the prognosis of gastric cancer by PD-1 and PD-L1 molecular, identification the beneficiaries of monoclonal antibody drugs, and promote the precision medicine in gastric cancer.

程序性死亡分子1（PD-1）与其配体(PD-L1)结合，可以通过抑制淋巴细胞活性，介导肿瘤免疫逃逸。PD-1，PD-L1的表达可能与单克隆抗体药物的疗效及肿瘤预后相关，其阻断剂已成为最具希望的肿瘤免疫疗法之一。胃癌，特别是晚期及转移性胃癌患者预后不佳，且不同分子分型胃癌对免疫疗法的反应可能不同，因此发现与胃癌免疫疗效及长期预后相关的分子标志物尤为重要。本研究拟通过流行病学方法，利用胃癌生存队列，分析 PD-1，PD-L1蛋白在不同分子分型胃癌中的表达差异及其表达与胃癌预后的关系；采用基因分型技术，探讨PD-1，PD-L1基因多态性与其蛋白表达的关系及对胃癌预后的影响；同时采用生物统计学方法和实验室研究，探索和验证IFN-γ介导的JAK-STAT信号通路对胃癌中PD-L1表达的调控机制，为综合评估PD-1，PD-L1分子对胃癌预后的预测作用，筛选靶向药物的受益患者，实现胃癌的精准治疗提供依据

本研究系统探讨了程序性死亡分子1（PD-1）及其配体（PD-L1）基因多态及蛋白表达对胃癌长期预后的预测价值。结合胃癌分子分型及病原学分型，对EBV感染型、Hp感染型胃癌患者PD-1，PD-L1，蛋白表达水平的差异进行研究。采用生物信息技术，通过公共数据库数据进行基因功能和相关通路富集，寻找胃癌中与PD-L1表达相关的信号通路，提出JAK-STAT信号通路可能调控胃癌中PD-L1的表达，并进行了初步验证。对胃癌的精准治疗和预后预测提供了依据。. 研究结果发现PD-L1rs822336位点CC基因型是胃癌患者良好预后的独立影响因素（HR=0.504, 95%CI=0.283-0.897）；亚组分析结果显示，PD-L1rs822336位点CC基因型 rs2297136位点AA+AG基因型与未进行术后化疗的胃癌患者的良好预后相关（HR=0.385, 95%CI=0.189–0.786 & HR=0.348, 95%CI=0.125-0.968）。免疫组织化学染色结果提示：EBV感染型胃癌患者中胃癌细胞及肿瘤浸润淋巴细胞均呈现PD-L1蛋白的高表达。未发现PD-1,PD-L1蛋白表达与幽门螺旋杆菌感染相关。肿瘤浸润免疫细胞中PD-L1的阳性表达，是胃癌患者良好预后的预测因素，PD-1蛋白和PD-L1蛋白的共表达与胃癌患者的良好预后相关，并且随着阳性标志物数量的增多，胃癌患者的死亡风险降低，呈现显著剂量效应关系（P-value for trend=0.005）。PD-1，PD-L1基因多态性与蛋白表达之间的关联分析发现，携带rs2297136位点AA+AG基因型的患者，较携带该位点GG基因型的患者，PD-L1蛋白表达的阳性率更高（P=0.014）。通过调用The Cancer Genome Atlas (TCGA)数据库中380个胃癌样本的RNAseq数据，计算了16924个基因mRNA表达水平与PD-L1 mRNA表达水平的相关性。将与PD-L1表达相关性最高的25个基因进行通路富集分析发现，其中7个基因与JAK-STAT通路相关，其调控机制，将是我们未来研究的方向之一。