Publication
Acidosis-mediated increase in IFN-γ-induced PD-L1 expression on cancer cells as an immune escape mechanism in solid tumors.
Journal Paper/Review - Dec 15, 2023
Knopf Philipp, Stowbur Dimitri, Hoffmann Sabrina Hl, Hermann Natalie, Maurer Andreas, Bucher Valentina, Poxleitner Marilena, Tako Bredi, Sonanini Dominik, Krishnamachary Balaji, Sinharay Sanhita, Fehrenbacher Birgit, Gonzalez-Menendez Irene, Reckmann Felix, Bomze David, Flatz Lukas, Kramer Daniela, Schaller Martin, Forchhammer Stephan, Bhujwalla Zaver M, Quintanilla-Martinez Leticia, Schulze-Osthoff Klaus, Pagel Mark D, Fransen Marieke F, Röcken Martin, Martins André F, Pichler Bernd, Ghoreschi Kamran, Kneilling Manfred
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PubMed
Doi
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Journal
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Issn Electronic
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Brief description/objective
Immune checkpoint inhibitors have revolutionized cancer therapy, yet the efficacy of these treatments is often limited by the heterogeneous and hypoxic tumor microenvironment (TME) of solid tumors. In the TME, programmed death-ligand 1 (PD-L1) expression on cancer cells is mainly regulated by Interferon-gamma (IFN-γ), which induces T cell exhaustion and enables tumor immune evasion. In this study, we demonstrate that acidosis, a common characteristic of solid tumors, significantly increases IFN-γ-induced PD-L1 expression on aggressive cancer cells, thus promoting immune escape. Using preclinical models, we found that acidosis enhances the genomic expression and phosphorylation of signal transducer and activator of transcription 1 (STAT1), and the translation of STAT1 mRNA by eukaryotic initiation factor 4F (elF4F), resulting in an increased PD-L1 expression. We observed this effect in murine and human anti-PD-L1-responsive tumor cell lines, but not in anti-PD-L1-nonresponsive tumor cell lines. In vivo studies fully validated our in vitro findings and revealed that neutralizing the acidic extracellular tumor pH by sodium bicarbonate treatment suppresses IFN-γ-induced PD-L1 expression and promotes immune cell infiltration in responsive tumors and thus reduces tumor growth. However, this effect was not observed in anti-PD-L1-nonresponsive tumors. In vivo experiments in tumor-bearing IFN-γ mice validated the dependency on immune cell-derived IFN-γ for acidosis-mediated cancer cell PD-L1 induction and tumor immune escape. Thus, acidosis and IFN-γ-induced elevation of PD-L1 expression on cancer cells represent a previously unknown immune escape mechanism that may serve as a novel biomarker for anti-PD-L1/PD-1 treatment response. These findings have important implications for the development of new strategies to enhance the efficacy of immunotherapy in cancer patients.