Exome sequencing of KP and KPM lung tumors.

Immune checkpoint blockade (ICB) with PD1 or PDL1 antibodies has been approved for the treatment of non-small cell lung cancer (NSCLC). However, only a minority of the patients respond and sustained remissions are rare. Both chemotherapy and anti-angiogenic drugs may improve tumor response to ICB in mouse models and patients with cancer. Here, we used genetically engineered mouse models of KrasG12D/p53null NSCLC, including a mismatch repair-deficient variant (KrasG12D/p53null/Msh2null) with higher mutational burden, and longitudinal imaging to study tumor response and resistance to combinations of ICB, anti-angiogenic therapy, and chemotherapy. Anti-angiogenic blockade of VEGFA and angiopoietin-2 markedly slowed progression of established tumors but, contrary to findings in other mouse cancer models, addition of a PD1 or PDL1 antibody was not beneficial and even accelerated progression of some of the tumors. We found that anti-angiogenic treatment facilitated tumor infiltration by PD1+ regulatory T cells (T-regs), which were more efficiently targeted by the PD1 antibody than CD8+ T cells. Both tumor-associated macrophages (TAMs) of bone-marrow origin, which are CSF1R-dependent, and TAMs of alveolar origin, which are sensitive to cisplatin, contributed to establishing a TGFB-rich tumor microenvironment that supported PD1+ T-regs. Dual TAM targeting with a combination of cisplatin and a CSF1R inhibitor fully abated T-regs, redirected the PD1 antibody to CD8+ T cells, and improved the efficacy of anti-angiogenic immunotherapy, achieving regression of the majority of the tumors. Overall design: Exome sequencing of KP (KrasLSL-G12D/+; p53fl/fl) and KPM (KrasLSL-G12D/+; p53fl/fl;Msh2–/–) lung tumors.