Interleukin-17A Promotes Lung Tumor Progression through Neutrophil Attraction to Tumor Sites and Mediating Resistance to PD-1 Blockade

Introduction: Proinflammatory cytokine interleukin-17A (IL-17A) is overexpressed in a subset of patients with lung cancer. We hypothesized that IL-17A promotes a pro-tumorigenic inflammatory phenotype and inhibits antitumor immune responses. Methods: We generated bitransgenic mice expressing a conditional IL-17A allele along with conditional Kras(G12D) and performed immune phenotyping of mouse lungs, a survival analysis, and treatment studies with antibodies either blocking programmed cell death 1 (PD-1) or IL-6 or depleting neutrophils. To support the preclinical findings, we analyzed human gene expression data sets and immune profiled patient lung tumors. Results: Tumors in IL-17:Kras(G12D) mice grew more rapidly, resulting in a significantly shorter survival as compared with that of KrasG12D mice. IL-6, granulocyte colony stimulating factor (G-CSF), milk fat globule-EGF factor 8 protein, and C-X-C motif chemokine ligand 1 were increased in the lungs of IL17:Kras mice. Time course analysis revealed that levels of tumor-associated neutrophils were significantly increased, and lymphocyte recruitment was significantly reduced in IL17:KrasG12D mice as compared with in Kras(Gl2D) mice. In therapeutic studies PD-1 blockade was not effective in treating IL-17:Kras(G12D) tumors. In contrast, blocking IL-6 or depleting neutrophils with an anti-Ly-6G antibody in the IL17:Kras(G12D) tumors resulted in a clinical response associated with T-cell activation. In tumors from patients with lung cancer with KRAS mutation we found a correlation between higher levels of IL-17A and colony- stimulating factor 3 and a significant correlation among high neutrophil and lower T-cell numbers. Conclusions: Here we have shown that an increase in a single cytokine, IL-17A, without additional mutations can promote lung cancer growth by promoting inflammation, which contributes to resistance to PD-1 blockade and sensitizes tumors to cytokine and neutrophil depletion. (C) 2017 International Association for the Study of Lung Cancer. Published by Elsevier Inc.