MET-STAT通路调节脑胶质瘤PD-L1表达及免疫逃逸机制的研究

Gliomas are the most common primary intracranial malignancies in adults. Immunotherapy has gradually emerged as an important means of treating malignant tumors. Previous studies have found that in gliomas, the expression level of PD-L1 increases with the degree of tumor malignancy, which is closely related to the activation of sputum cell function. Further studies found that high activation of MET can significantly up-regulate the expression level of PD-L1, change the immune cell components and immune microenvironment in the tumor, assisting the tumor to escape the cytotoxic killing of immune cells, and inhibiting MET can significantly reduce expression level of PD-L1. At the same time, MET activation in gliomas leads to activation of the downstream STAT pathway. However, whether MET regulates PD-L1 expression levels and immune microenvironment through the STAT pathway, and its mechanism is still unclear. This is of great significance for deciphering the immune escape mechanism of glioma and the application of immunotherapy such as PD-L1 antibody. The aim of this study is to combine the analysis of big data and experiments to elucidate the mechanism of regulation of PD-L1 expression and immune evasion mediated by of MET-STAT pathway in glioma, promoting the combination of immunotherapy and MET-targeted treatments for glioma patients.

脑胶质瘤是最常见的成人原发性颅内恶性肿瘤，免疫治疗逐渐兴起成为治疗恶性肿瘤的重要手段。我们前期研究发现，在脑胶质瘤中PD-L1表达水平与恶性程度密切相关，并参与调节T细胞活化与耗竭。进一步研究发现，MET高激活能够显著上调PD-L1的表达水平，改变肿瘤内免疫细胞成分和免疫微环境，抑制MET可显著降低PD-L1表达水平。同时，在脑胶质瘤中MET激活可导致下游STAT通路激活。由此，我们提出假设：MET可通过激活STAT通路调节PD-L1表达水平及免疫细胞成分等免疫微环境因素，协助肿瘤细胞逃避免疫杀伤。本研究旨在结合前期研究基础，通过整合大数据分析、细胞学、在体动物实验和临床样本验证，联合靶向抑制剂等方法，解析MET-STAT通路调节脑胶质瘤PD-L1表达及免疫逃逸的机制，希望能为开发脑胶质瘤免疫治疗和靶向MET治疗相结合的联合治疗相结合的联合治疗方案奠定理论基础。

脑胶质瘤是最常见的成人原发性颅内恶性肿瘤，免疫治疗逐渐兴起成为治疗恶性肿瘤的重要手段。我们前期研究发现，在脑胶质瘤中PD-L1表达水平与恶性程度密切相关，并参与调节T细胞活化与耗竭。进一步研究发现，MET高激活能够显著上调PD-L1的表达水平，改变肿瘤内免疫细胞成分和免疫微环境，抑制MET可显著降低PD-L1表达水平。同时，在脑胶质瘤中MET激活可导致下游STAT通路激活。通过我们的研究发现，MET被干细胞生长因子激活后，能够进一步激活STAT4通路，通过STAT4在转录层面调节PD-L1表达水平，病情能够富集巨噬细胞等免疫细胞，形成抑制性免疫微环境，协助肿瘤细胞逃避免疫杀伤。..课题组收集了1243例原发胶质瘤样本(WHO2-4级)的RNA表达数据，包括癌症基因组图谱、中国胶质瘤基因组图谱和GSE16011数据集。对多组学数据研究，我们发现了MET表达与胶质瘤微环境之间的关系。三个数据集的Pearson相关检验显示，MET与PD-L1和STAT通路具有很强的相关性。Western blot分析显示，在GBM细胞系(N33和LN229)中，肝细胞生长因子激活MET后，PD-L1和磷酸化的STAT4上调，而PLB-1001抑制MET后下调。肿瘤组织芯片分析显示MET与PD-L1及巨噬细胞相关标志物呈正相关。染色质免疫沉淀-PCR检测显示，PD-L1 DNA中STAT4蛋白高度富集，这表便STAT4作为转录因子，激活后，能够显著促进PD-L1的表达。后续Transwell共培养和趋化实验表明，在GBM细胞中敲除MET表达，能够显著抑制巨噬细胞的趋化，这说明MET的高表达与脑胶质瘤中巨噬细胞的趋化富集具有确切的因果关系。此外，我们进行了CIBERSORTx和单细胞RNA测序数据分析，结果显示MET过表达的胶质瘤样本中巨噬细胞数量增加。Kaplan-Meier生存分析显示MET/STAT4/PD-L1通路的激活和巨噬细胞的富集与原发性GBM患者较短的生存时间相关。.综上，本研究解析了MET-STAT通路调节脑胶质瘤PD-L1表达及巨噬细胞富集导致的免疫逃逸的机制，提示我们在后续的临床治疗研究中，尤其针对MET高表达的脑胶质瘤患者，联合应用MET和免疫抑制剂可能会给患者带来更多的生存收益，为推动脑胶质瘤免疫治疗和MET靶向药物的联合治疗奠定了理论和临床前实验基础。