Trametinib sensitizes KRAS-mutant lung adenocarcinoma tumors to PD-1/PD-L1 axis blockade via Id1 downregulation

The identification of novel therapeutic strategies to overcome the intrinsic or acquired resistance to trametinib in mutant KRAS lung adenocarcinoma (LUAD) is a major challenge. This study analyzes the effects of trametinib in Id1, a key factor involved in the oncogenic KRAS pathway, and investigates the Id1 role in acquire resistance and synergy with immunotherapy in KRAS-driven LUAD. Restoring the antitumor immune response by blocking programmed-cell death protein 1 (PD-1) and programmed-cell death-ligand 1 (PD-L1) pathway represents a major breakthrough in non-small-cell lung cancer (NSCLC) treatment. Nevertheless, a high proportion of LUAD patients with KRAS alterations remain refractory to this therapy. Material and Methods: To explore whether MEK1/2 inhibition reduces Id1 expression, in vitro and in vivo experiments were conducted in KRAS-mutant NSCLC cells and murine models. RNAseq analysis was performed to elucidate the pathways involved in Id1 inhibition. Apoptosis and PD-L1 expression was measured by flow cytometry. Synergy of trametinib combined with anti-PD1 was investigated in KRAS-mutant LUAD mouse models. Results: Using preclinical syngeneic KRAS-mutant lung cancer mouse models, we demonstrate that trametinib synergizes with PD-1 blockade to reduce lung cancer progression and increase mice overall survival. This antitumor activity was linked to the degradation of Id1 via proteasome, and an enhanced INF-Y-mediated PD-L1 tumor cell expression in KRAS-mutant tumor cells. This effect required CD8+ T cells, boosted the intratumoral CD8+/Treg ratio, reducing the intratumoral Treg/CD4+ ratio. Conclusions: Our data may support the role of Id1 in the trametinib antitumoral effect, sustaining the mitogen-activated protein kinases (MAPK) signaling pathway involved in the trametinib acquired resistance cells and sensitizing KRAS-mutant lung tumors to PD-1 inhibitors, through PD-L1 overexpression. Overall design: In order to investigate the molecular mechanisms involved in the trametinib-mediated Id1 downregulation, a global transcriptomic profiling using RNA sequencing analysis was performed on murine CMT167 and KLA lung cancer cells treated or not with trametinib.