{
  "abstract": "Background Metabolic competition and nutrient restriction in the tumor microenvironment (TME) shape the immune infiltrate in tumors and subsequently tumor immunity. In this study we used the transgenic melanoma mouse model tg(Grm1)EPv, which spontaneously develops melanoma due to the ectopic expression of the metabotropic glutamate receptor 1 ( Grm1) in melanocytes to investigate if aberrant glutamate metabolism drives tumor formation and affects immune cell function.Methods We performed liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based metabolomic analyses and RNA sequencing on tumor-free and tumor-bearing tg(Grm1)EPv tissues to characterize metabolic alterations associated with tumor progression. Flow cytometry was used to examine changes in immune cell subsets within the TME. To assess the functional relevance of glutamate metabolism, we inhibited glutathione metabolism using L-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutamate-cysteine ligase that depletes cellular glutathione levels.Results LC-MS/MS-based metabolomic analyses and RNA sequencing revealed changes in glutamate and glutamine metabolism, a glycolytic shift (Warburg effect), and reduced ATP levels in advanced tumors compared with tumor-free tissue, suggesting respiratory chain dysfunction. These metabolic changes in the TME are advantageous for the tumor cells and unfavorable for immune cells, such as dendritic cells (DC). Indeed, flow cytometry analysis of myeloid subsets during tumor progression showed a decline in tumor-infiltrating conventional type 2 DC and macrophages, alongside an increase in neutrophil and monocyte populations in advanced lesions. Interference with glutamate metabolism using BSO induced immunogenic cell death, namely ferroptosis, in an tg(Grm1)EPv-derived cell line in vitro. Therefore, we evaluated the combination of this inhibitor with immunotherapy as a promising new approach for the treatment of tumors in the tg(Grm1)EPv mouse model. We observed that tumor growth could be delayed in vivo when BSO was combined with a therapy regimen boosting DC numbers and activation. This inhibition of tumor growth was supported by the infiltration of activated T cells.Conclusion Overall, our findings provide novel insights into the importance of combining metabolic intervention with immunotherapy for the treatment of patients with melanoma, particularly those bearing glutamate pathway-active or immunologically cold tumors. This knowledge can drive the design of novel therapeutic strategies for patients with cancer.",
  "authors": [
    {
      "affiliations": [
        "Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Sophie Marie Dieckmann"
    },
    {
      "affiliations": [
        "Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Christoph H Tripp"
    },
    {
      "affiliations": [
        "Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Helen Strandt"
    },
    {
      "affiliations": [
        "Department of Internal Medicine V, Medical University of Innsbruck, Innsbruck, Austria",
        "Tyrolean Cancer Research Institute, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Florian Hornsteiner"
    },
    {
      "affiliations": [
        "Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Annelie Kerstin Schäfer"
    },
    {
      "affiliations": [
        "Centre for Immunobiology and Infection, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK"
      ],
      "name": "Anastasia Prokopi"
    },
    {
      "affiliations": [
        "Department of Dermatology, Venerelogoy and Allergology, Medical University of Innsbruck University Hospital for Dermatology and Venereology, Innsbruck, Austria"
      ],
      "name": "Janine Vierthaler"
    },
    {
      "affiliations": [
        "Institute of Immunology, Dresden University of Technology, Dresden, Germany"
      ],
      "name": "Antonia Resag"
    },
    {
      "affiliations": [
        "Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Daniela Ortner-Tobider"
    },
    {
      "affiliations": [
        "Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Vera Reinstadler"
    },
    {
      "affiliations": [
        "Department of Molecular Biology, Digital Science Center (DiSC), University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Irene Rigato"
    },
    {
      "affiliations": [
        "Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Berit Junger"
    },
    {
      "affiliations": [
        "Department of Pediatrics I, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Alexeja Kleiter"
    },
    {
      "affiliations": [
        "Institute of Bioinformatics, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Georgios Fotakis"
    },
    {
      "affiliations": [
        "Barts Cancer Institute, Queen Mary University of London, London, UK"
      ],
      "name": "Mirjana Efremova"
    },
    {
      "affiliations": [
        "Biocenter, Institute of Bioinformatics, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Zlatko Trajanoski"
    },
    {
      "affiliations": [
        "JJP Biologics, Warsaw, Poland"
      ],
      "name": "Louis Boon"
    },
    {
      "affiliations": [
        "Department of Chemical Biology, Rutgers The State University of New Jersey, New Brunswick, New Jersey, USA"
      ],
      "name": "Suzie Chen"
    },
    {
      "affiliations": [
        "Institute of Biochemistry, FAU, Erlangen, Germany"
      ],
      "name": "Anja Katrin Bosserhoff"
    },
    {
      "affiliations": [
        "Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Herbert Oberacher"
    },
    {
      "affiliations": [
        "Department of Molecular Biology, Digital Science Center (DiSC), University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Francesca Finotello"
    },
    {
      "affiliations": [
        "Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria"
      ],
      "name": "Patrizia Stoitzner"
    }
  ],
  "title": "Metabolic inhibition of glutamate-cysteine ligase increases dendritic cell-mediated antitumor immunity in melanoma",
  "uid": "32f01eb4-79bd-5da9-93ef-db55d93b18a8"
}