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. 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.