Integrative MHC-I peptidome quantitation with isobaric tagging mass spectrometry

Despite the appreciation of CD8+ T cell anti-tumor immune responses towards improvement patient outcomes, the MHC-I peptides that facilitate the response are poorly described. Alternatively, whether cancer therapies alter the MHC-I peptide repertoire has not been fully assessed due to the lack of quantitative strategies. In this regard, anthracyclines and ionizing radiation both increase the infiltration of CD8+ T cells into tumors but whether they do so by altering the MHC-I peptidome repertoire is not known. To investigate this, we developed a platform for screening therapy-induced MHC-I peptides by quantitative, multiplexed measurement of MHC-I peptides with tandem mass tags (TMT). We show that both ionizing radiation and the anthracycline doxorubicin induce MHC-I peptides that are largely derived from mitotic progression and cell cycle proteins. Our approach enables further strategies to understand how small molecules and other therapies alter MHC-I peptide presentation that may be harnessed for CD8+ T cell-based immunotherapies.