*State Key Laboratory of Oncology in South China, Department of Medical Oncology, Sun Yat-Sen University Cancer Center, Guangzhou, China; †Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, Guangdong, China; ‡Department of Medical Oncology, and §Department of Pathology, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, Guangdong, China.
J Thorac Oncol. 2015 Jun;10(6):910-23. doi: 10.1097/JTO.0000000000000500.
Epidermal growth factor receptor (EGFR) mutation status was reported to be associated with programmed death-ligand 1 (PD-L1) expression. However, the molecular mechanism of PD-L1 regulation by EGFR activation and the potential clinical significance of blocking PD-1/PD-L1 in EGFR-mutant non-small-cell lung cancer (NSCLC) treated with EGFR tyrosine kinase inhibitors (TKIs) were largely unknown.
Western blot, real-time polymerase chain reaction, immunofluorescence, and flow cytometry were employed to explore the association between PD-L1 and EGFR activation. Then, we used EGFR-TKIs and downstream pathways inhibitors to clarify the detailed signaling pathway involved in PD-L1 regulation. Cell apoptosis, viability, and enzyme-linked immunosorbent assay test were used to study the immune suppression by EGFR activation and immune reactivation by EGFR-TKIs and/or PD-1 blocking in tumor cells and human peripheral blood mononuclear cells coculture system.
We found that EGFR activation by EGF stimulation, exon-19 deletions, and L858R mutation could induce PD-L1 expression. EGFR activation upregulated PD-L1 through p-ERK1/2/p-c-Jun but not through p-AKT/p-S6 pathway. PD-L1 mediated by EGFR activation could induce the apoptosis of T cells through PD-L1/PD-1 axis in tumor cells and peripheral blood mononuclear cells coculture system. Inhibiting EGFR by EGFR-TKIs could free the inhibition of T cells and enhance the production of interferon-γ. Synergistic tumor cell killing effects were not observed with EGFR-TKIs and anti-PD-1 antibody combination treatment in coculture system.
Our results imply that EGFR-TKIs could not only directly inhibit tumor cell viability but also indirectly enhance antitumor immunity through the downregulation of PD-L1. Anti-PD-1/PD-L1 antibodies could be an optional therapy for EGFR-TKI sensitive patients, especially for EGFR-TKIs resistant NSCLC patients with EGFR mutation. Combination of EGFR-TKIs and anti-PD-1/PD-L1 antibodies treatment in NSCLC is not supported by the current study but warrant more studies to move into clinical practice.
表皮生长因子受体（EGFR）突变状态与程序性死亡配体 1（PD-L1）表达有关。然而，EGFR 激活调控 PD-L1 的分子机制，以及在接受 EGFR 酪氨酸激酶抑制剂（TKI）治疗的 EGFR 突变型非小细胞肺癌（NSCLC）中阻断 PD-1/PD-L1 的潜在临床意义，在很大程度上仍不清楚。
采用 Western blot、实时聚合酶链反应、免疫荧光和流式细胞术探讨 PD-L1 与 EGFR 激活的关系。然后，我们使用 EGFR-TKIs 和下游通路抑制剂来阐明参与 PD-L1 调控的详细信号通路。细胞凋亡、活力和酶联免疫吸附试验用于研究 EGFR 激活引起的免疫抑制以及 EGFR-TKIs 和/或 PD-1 阻断在肿瘤细胞和人外周血单个核细胞共培养系统中引起的免疫再激活。
我们发现，EGF 刺激、外显子 19 缺失和 L858R 突变导致的 EGFR 激活可诱导 PD-L1 表达。EGFR 激活通过 p-ERK1/2/p-c-Jun 而上调 PD-L1，但不是通过 p-AKT/p-S6 通路。在肿瘤细胞和外周血单个核细胞共培养系统中，由 EGFR 激活介导的 PD-L1 通过 PD-L1/PD-1 轴诱导 T 细胞凋亡。通过 EGFR-TKIs 抑制 EGFR 可释放 T 细胞的抑制作用，并增强干扰素-γ的产生。在共培养系统中，EGFR-TKIs 与抗 PD-1 抗体联合治疗并未观察到协同的肿瘤细胞杀伤作用。
我们的结果表明，EGFR-TKIs 不仅可以直接抑制肿瘤细胞活力，还可以通过下调 PD-L1 间接增强抗肿瘤免疫。抗 PD-1/PD-L1 抗体可能是 EGFR-TKI 敏感患者的一种可选治疗方法，尤其是对于 EGFR-TKI 耐药且存在 EGFR 突变的 NSCLC 患者。目前的研究不支持 NSCLC 中 EGFR-TKIs 与抗 PD-1/PD-L1 抗体联合治疗，但需要更多的研究来推进临床实践。
