Death receptor 4 (DR4) is a cell surface protein that is generally thought to mediate apoptosis upon binding to its ligand named TRAIL. However, its contribution to apoptosis resistance has also been reported. MET (or c-MET) gene amplification represents an important mechanism for acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs) against EGFR mutant non-small cell lung cancer (NSCLC). This study focuses on demonstrating the impact of MET inhibition on DR4 modulation in MET-amplified EGFR mutant NSCLC cell lines and the underlying mechanisms. Several MET inhibitors decreased DR4 levels in MET-amplified HCC827 cell lines resistant to EGFR-TKIs with no or limited effects on modulating DR5 levels, while increasing DR4 levels in HCC827 parental cells and other NSCLC cell lines. MET inhibitors did not affect DR4 stability, but decreased DR4 mRNA levels with suppression of AP-1-dependent DR4 promoter transactivation. Moreover, these inhibitors suppressed ERK and c-Jun phosphorylation accompanied with decreasing c-Jun levels. Hence, it is likely that MET inhibition downregulates DR4 expression in MET-amplified EGFR mutant NSCLC cells through suppressing AP-1-mediated DR4 transcription. Osimertinib combined with MET inhibition synergistically induces apoptosis in the MET-amplified EGFR mutant NSCLC cells accompanied with augmented DR4 reduction both in vitro and in vivo. Furthermore, MET inhibition combined with TRAIL enhanced killing of MET-amplified EGFR mutant HCC827/AR cells, but not HCC827 parental cells. These data collectively suggest that DR4 may possess an unrecognized anti-apoptotic function, contributing to apoptosis resistance under given conditions.

死亡受体 4 (DR4) 是一种细胞表面蛋白，通常被认为在与其名为 TRAIL 的配体结合后介导细胞凋亡。然而，它对细胞凋亡抗性的贡献也有报道。MET（或c-MET）基因扩增代表了针对 EGFR 突变非小细胞肺癌（NSCLC）对 EGFR 酪氨酸激酶抑制剂（EGFR-TKI）的获得性耐药的重要机制。本研究的重点是证明 MET 抑制对MET扩增的 EGFR 突变 NSCLC 细胞系中 DR4 调节的影响及其潜在机制。几种 MET 抑制剂降低了MET中的 DR4 水平-扩增的 HCC827 细胞系对 EGFR-TKI 具有抗性，对调节 DR5 水平没有影响或影响有限，同时增加 HCC827 亲代细胞和其他 NSCLC 细胞系中的 DR4 水平。MET 抑制剂不影响 DR4 稳定性，但通过抑制 AP-1 依赖性 DR4 启动子反式激活降低了 DR4 mRNA 水平。此外，这些抑制剂抑制 ERK 和 c-Jun 磷酸化，同时降低 c-Jun 水平。因此，MET 抑制可能通过抑制 AP-1 介导的 DR4 转录来下调MET扩增的 EGFR 突变 NSCLC 细胞中的 DR4 表达。奥希替尼联合 MET 抑制在体外协同诱导MET扩增的EGFR 突变 NSCLC 细胞凋亡，同时增加 DR4 减少和体内。此外，MET 抑制与 TRAIL 结合增强了对MET扩增的EGFR 突变 HCC827/AR 细胞的杀伤，但对 HCC827 亲本细胞没有作用。这些数据共同表明 DR4 可能具有未被识别的抗细胞凋亡功能，在给定条件下有助于细胞凋亡抗性。