Abstract 4025: Impact of Kras mutant subtypes on PD-L1 expression in lung adenocarcinoma

Clinical responses to immune checkpoint blockade by anti-PD-1/PD-L1 monoclonal antibodies in non-small-cell lung cancer (NSCLC) may be associated with PD-L1 expression. This study was undertaken to determine the expression profile of PD-L1 in patients with Kras-mutant lung adenocarcinoma (LUAD) and to investigate the activation of Kras codon subtypes as a mechanism of PD-L1 regulation. Immunohistochemistry analysis of PD-L1 expression (SP142 clone) on 117 LUAD (KrasWT, n = 51; KrasG12D, n = 25; KrasG12V, n = 14; KrasG12C, n = 27), showed significantly greater expression of PD-L1 in both tumor and immune cells compartments in Kras mutant LUAD compared with KrasWT wild-type tumors (37% vs. 18%; P = 0.005). PD-L1+ tumors had greater CD66b+ neutrophil infiltrate and lower CD8+ T-cell infiltrate than PD-L1− tumors, notably in KrasG12D tumors. To determine the effect of Kras codon subtypes on PD-L1 expression, stable cell lines were generated by transfection of KrasG12D, KrasG12V, KrasG12C and KrasWT plasmids into Beas2B bronchial cells. At basal level, mutant Kras led to significantly higher cell-surface PD-L1 expression and PD-L1 transcripts, notably in KrasG12C and KrasG12V cells, suggesting transcriptional regulation. Moreover, there was differential activation of NF-kB, ERK and Pi3k/Akt pathways between Kras mutant subtypes. In addition, PD-L1 was upregulated 3-fold by stimulation with IFNγ, independently of the Kras codon subtypes. Instead, hypoxia significantly increased PD-L1 expression in KrasG12C and KrasG12D cells. Co-culture experiments with human PBMCs from healthy patients were performed to determine the functional effect of altered PD-L1 expression. Increased PD-L1 expression by tumor cells induced by Kras mutations led to decreased PBMCs proliferation and increased apoptosis. PD-L1 is expressed in 37% of Kras mutant LUAD, suggesting PD-L1 as a therapeutic target in this subset. According to the Kras mutation subtype, potential drugs targeting the NF-kB, ERK or Pi3k/Akt pathways may increase the antitumor adaptive immune responses. Citation Format: Marius Ilie, Laetitia Fazzalari, Nicolas Guibert, Nathalie Yazbeck, Laurie Signetti, Véronique Hofman, Elodie Long, Katia Zahaf, Julien Fayada, Virginie Lespinet, Olivier Bordone, Virginie Tanga, Kevin Washetine, Nicolas Vénissac, Jérôme Mouroux, Charles Hugo Marquette, Patrick Brest, Paul Hofman. Impact of Kras mutant subtypes on PD-L1 expression in lung adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4025.