p53介导PD-L1调控在肺癌EGFR-TKI耐药及免疫逃逸中的作用和机制研究

Our previous study found that EGFR mutation could up-regulate the expression of programmed cell death ligand 1 (PD-L1) and mediate immune evasion of lung cancer; and high expression of PD-L1 may be involved in the drug resistance of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), the detailed mechanisms of which remain unknown. Our preliminary experiments found that PD-L1 expression was remarkably over-expressed in the circumstance of p53 and EGFR co-alterations which also was associated with primary and secondary EGFR-TKIs resistance. We hypothesize that p53 loss and/or mutation amplifies the EGFR mutation-mediated PD-L1 up-regulation and leads to immune evasion and EGFR-TKIs resistance in lung cancer. In the project, we utilize lung cancer cell lines with different p53 gene status to investigate the impact of three status of p53 gene (wildtype, loss and mutation) on the EGFR-mediated PD-L1 expression and unveil its molecular mechanisms. We also try to reveal the influence of p53 and EGFR genes on immune microenvironment and viability of lung cancer cells with tumor cell and T cell co-culture system and EGFR-mutant/p53-loss transgenic mouse models. The project will for the first time investigate the regulation of PD-L1 by oncogene and tumor suppressor gene collectively and provide theoretical basis and experimental rationale for precisely determining the patients that might benefit from anti-PD-1/PD-L1 antibodies and overcoming EGFR-TKIs resistance.

我们前期研究发现EGFR突变可上调PD-L1表达，介导肺癌的免疫逃逸；PD-L1高表达可能参与了EGFR-TKIs耐药，但其具体机制未明。我们预实验发现p53基因变异合并EGFR突变后，PD-L1表达显著升高，并与EGFR-TKI原发和继发耐药相关。我们假设p53缺失和/或突变强化了EGFR突变介导的PD-L1上调，导致肺癌的免疫逃逸和EGFR-TKI耐药。本项目将在不同p53基因背景的肺癌细胞系中，研究p53（野生、缺失、突变）三种状态对EGFR基因介导的PD-L1调节的影响，阐明其分子机制，并通过肿瘤细胞与T细胞共培养体系及EGFR突变/p53缺失转基因小鼠模型，揭示p53和EGFR基因对免疫微环境及肺癌细胞活性的影响。本项目将首次研究癌基因和抑癌基因共同调节PD-L1的机制，为精准定位抗PD-1/PD-L1免疫治疗的获益人群和克服EGFR-TKIs耐药提供理论基础和实验依据。

常见EGFR突变的非小细胞肺癌有一半以上的突变概率对EGFR-TKI敏感。而TP53突变是EGFR伴随最高频突变。这种共突变缩短非小细胞肺癌患者的无进展生存时间以及总生存时间，因而导致不良的预后。我们前期研究发现EGFR突变可上调PD-L1表达，介导肺癌的免疫逃逸；PD-L1高表达可能参与了EGFR-TKIs耐药，我们发现p53基因变异合并EGFR突变后，PD-L 1表达显著升高，并与EGFR-TKI原发和继发耐药相关。本课题针对EGFR-TKIs的耐药机制，免疫微环境等各个方面进行了非常全面、系统的研究。我们研究发现了EGFR L858R突变合并TP53突变，PD-L1阳性率显著高于L858R突变/TP53野生型。另外，我们完成中国非小细胞肺癌人群PD-1/PD-L1免疫治疗疗效与基因组学特征的关系。临床上，我们发现对于单独使用吉非替尼治疗的这组患者，基线同时存在TP53突变的EGFR突变型NSCLC患者，其中位无进展时间(PFS)较没有合并TP53突变的EGFR突变型NSCLC患者明显缩短。与此同时，我们发现PD-L1表达水平并非最佳疗效预测的生物标志物。并且，肿瘤内异质性（ITH）可作为肺癌接受抗PD-1/PD-L1单抗治疗的预测生物标志物。综上所述，本研究探索影响EGFR-TKIs疗效的各种因素，为P53合并EGFR突变病人对EGFR-KTI耐药探索新的治疗手段。