Systematic immune reprogramming via PD-1 inhibition enhances early-stage lung cancer survival.

Success of immune checkpoint inhibitors in advanced non-small cell lung cancer (NSCLC) has invigorated their use in neo-adjuvant setting for early-stage disease. However, the cellular and molecular mechanisms of the early immune responses to therapy remain poorly understood. Through an integrated analysis of early-stage NSCLC patients and a Kras-mutant mouse model, we show a prevalent programmed cell death 1/ programmed cell death 1 ligand 1 (PD-1/PD-L1) axis exemplified by increased intratumoral PD-1+ T cells and PD-L1 expression. Notably, tumor progression was associated with spatiotemporal modulation of the immune microenvironment. Importantly, PD-1 inhibition controlled tumor growth, improved overall survival, and reprogrammed tumor-associated lymphoid and myeloid cells. Depletion of T lymphocyte subsets demonstrated synergistic effects of those populations on PD-1 inhibition of tumor growth. Transcriptome analyses revealed T cell subset-specific alterations corresponding to degree of response to the treatment. These results provide insights into temporal evolution of the phenotypic effects of PD-1/PD-L1 activation and inhibition, and motivate targeting this axis early in lung cancer progression. Overall design: CD4 and CD8 lung tumor infiltrating lymphocytes were sorted into RLT lysis buffer from IgG antibody or anti-PD1 antibody treated C57Bl/6 mice at day 14, 17 or 24 for mRNA-Sequencing.