Hypoxia induces a state of immunogenic dormancy in non-small cell lung cancer by blocking protein translation of the MHC class I pathway associated with m5C hypermethylation of mRNA 3663

Description Deficiencies in the MHC class I presentation pathway (C1PP) drive immune evasion and resistance to immunotherapies in cancers, including non-small cell lung cancer (NSCLC). Understanding how the C1PP is disrupted is likely to uncover strategies to enhance tumor immunogenicity. Here, we show that hypoxia (low O2 in solid tumors) suppresses the protein translation (but not mRNA expression) of key IFN-γ-induced C1PP components in A549 NSCLC cells in a HIF-1α/2α independent manner. These components include the proteolytic subunits of the immunoproteasome, ER transporters, chaperones, and peptide-loading complexes. Immunopeptidomics revealed a significant reduction in the diversity and abundance of MHC class I-presented antigens under hypoxia, including dozens of neoantigens and tumor-associated antigens. Mechanistically, we identified hyper-m5C methylation in hypoxic mRNA as a likely driver of C1PP selective translational suppression using immunoblotting, ELISA, and direct m5C RNA mapping. Reversing this methylation with 5-azacitidine restored hypoxic C1PP protein translation. In vivo, hyperbaric oxygen therapy (HBOT) raised tumor O2, reduced tumor growth, enhanced T-cell effector function, and prolonged survival in s.c. murine NSCLC. This is the first evidence linking epitranscriptomic m5C modifications to C1PP regulation, and highlights HBOT as a promising strategy to restore tumor immunogenicity and improve therapeutic outcomes. Funding Sources Supported by: NIH-NCI CA214285-01A1; ACS-IRG – 18-164-43; ACS CAT-24-1414241-01-CAT Topic Categories Antigen and Dendritic Cell Processing, Presentation, and Biology (AGDC)