title: Efficacy of PD-1 Blockade Is Potentiated by Metformin-Induced Reduction of Tumor Hypoxia.
abstract: Blockade of the coinhibitory checkpoint molecule PD-1 has emerged as an effective treatment for many cancers, resulting in remarkable responses. However, despite successes in the clinic, most patients do not respond to PD-1 blockade. Metabolic dysregulation is a common phenotype in cancer, but both patients and tumors are metabolically heterogeneous. We hypothesized that the deregulated oxidative energetics of tumor cells present a metabolic barrier to antitumor immunity through the generation of a hypoxic microenvironment and that normalization of tumor hypoxia might improve response to immunotherapy. We show that the murine tumor lines B16 and MC38 differed in their ability to consume oxygen and produce hypoxic environments, which correlated with their sensitivity to checkpoint blockade. Metformin, a broadly prescribed type II diabetes treatment, inhibited oxygen consumption in tumor cells in vitro and in vivo, resulting in reduced intratumoral hypoxia. Although metformin monotherapy had little therapeutic benefit in highly aggressive tumors, combination of metformin with PD-1 blockade resulted in improved intratumoral T-cell function and tumor clearance. Our data suggest tumor hypoxia acts as a barrier to immunotherapy and that remodeling the hypoxic tumor microenvironment has potential to convert patients resistant to immunotherapy into those that receive clinical benefit. Cancer Immunol Res; 5(1); 9-16. ©2016 AACR.
authors.affiliation: Tumor Microenvironment Center, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania.|Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors.forename: Nicole E
authors.initials: NE
authors.lastname: Scharping
authors.affiliation: Tumor Microenvironment Center, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania.
authors.forename: Ashley V
authors.initials: AV
authors.lastname: Menk
authors.affiliation: Tumor Microenvironment Center, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania.|Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Whetstone
authors.affiliation: Tumor Microenvironment Center, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania.
authors.forename: Xue
authors.initials: X
authors.lastname: Zeng
authors.affiliation: Tumor Microenvironment Center, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania. delgoffeg@upmc.edu.|Department of Immunology, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors.forename: Greg M
authors.initials: GM
authors.lastname: Delgoffe
mesh_terms: D000818:Animals; D000074322:Antineoplastic Agents, Immunological / Q000494:pharmacology*; D016207:Cytokines / Q000378:metabolism; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D004357:Drug Synergism; D004734:Energy Metabolism / Q000235:genetics; D016246:Lymphocytes, Tumor-Infiltrating / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008546:Melanoma, Experimental; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D010101:Oxygen Consumption / Q000187:drug effects; D061026:Programmed Cell Death 1 Receptor / Q000037:antagonists & inhibitors*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D000072258:Tumor Hypoxia / Q000187:drug effects* / Q000276:immunology*; D059016:Tumor Microenvironment / Q000276:immunology
chemical_list: D000074322:Antineoplastic Agents, Immunological; D016207:Cytokines; D061026:Programmed Cell Death 1 Receptor; D008687:Metformin