PD-1 and CTLA-4 combination blockade expands infiltrating T cells and reduces regulatory T and myeloid cells within B16 melanoma tumors.
Vaccination with irradiated B16 melanoma cells expressing either GM-CSF (Gvax) or Flt3-ligand (Fvax) combined with antibody blockade of the negative T-cell costimulatory receptor cytotoxic T-lymphocyte antigen-4 (CTLA-4) promotes rejection of preimplanted tumors. Despite CTLA-4 blockade, T-cell proliferation and cytokine production can be inhibited by the interaction of programmed death-1 (PD-1) with its ligands PD-L1 and PD-L2 or by the interaction of PD-L1 with B7-1. Here, we show that the combination of CTLA-4 and PD-1 blockade is more than twice as effective as either alone in promoting the rejection of B16 melanomas in conjunction with Fvax. Adding alphaPD-L1 to this regimen results in rejection of 65% of preimplanted tumors vs. 10% with CTLA-4 blockade alone. Combination PD-1 and CTLA-4 blockade increases effector T-cell (Teff) infiltration, resulting in highly advantageous Teff-to-regulatory T-cell ratios with the tumor. The fraction of tumor-infiltrating Teffs expressing CTLA-4 and PD-1 increases, reflecting the proliferation and accumulation of cells that would otherwise be anergized. Combination blockade also synergistically increases Teff-to-myeloid-derived suppressor cell ratios within B16 melanomas. IFN-gamma production increases in both the tumor and vaccine draining lymph nodes, as does the frequency of IFN-gamma/TNF-alpha double-producing CD8(+) T cells within the tumor. These results suggest that combination blockade of the PD-1/PD-L1- and CTLA-4-negative costimulatory pathways allows tumor-specific T cells that would otherwise be inactivated to continue to expand and carry out effector functions, thereby shifting the tumor microenvironment from suppressive to inflammatory.
Curran
Michael A
MA
Department of Immunology, Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
Montalvo
Welby
W
Yagita
Hideo
H
Allison
James P
JP
D000818:Animals; D000943:Antigens, Differentiation / Q000276:immunology*; D001854:Bone Marrow Cells / Q000276:immunology*; D019496:Cancer Vaccines / Q000276:immunology; D053804:Granzymes / Q000276:immunology*; D007371:Interferon-gamma / Q000096:biosynthesis; D008546:Melanoma, Experimental / Q000276:immunology*; D061026:Programmed Cell Death 1 Receptor; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
D000943:Antigens, Differentiation; D019496:Cancer Vaccines; C491383:Pdcd1 protein, mouse; D061026:Programmed Cell Death 1 Receptor; D007371:Interferon-gamma; D053804:Granzymes; C509214:Gzmb protein, mouse