Oxidized Melanoma Antigens Promote Activation and Proliferation of Cytotoxic T-Cell Subpopulations

Increasing evidence suggests the role of reactive oxygen and nitrogen species (RONS) in regulating antitumor immune effects and immunosuppression. RONS modify biomolecules and induce oxidative post-translational modifications (oxPTM) on proteins that can alarm phagocytes. However, it is unclear if and how protein oxidation by technical means could be a strategy to foster antitumor immunity and therapy. To this end, cold gas plasma technology producing various RONS simultaneously to oxidize the two melanoma-associated antigens MART and PMEL is utilized. Cold plasma-oxidized MART (oxMART) and PMEL (oxPMEL) are heavily decorated with oxPTMs as determined by mass spectrometry. Immunization with oxidized MART or PMEL vaccines prior to challenge with viable melanoma cells correlated with significant changes in cytokine secretion and altered T-cell differentiation of tumor-infiltrated leukocytes (TILs). oxMART promoted the activity of cytotoxic central memory T-cells, while oxPMEL led to increased proliferation of cytotoxic effector T-cells. Similar T-cell results are observed after incubating splenocytes of tumor-bearing mice with B16F10 melanoma cells. This study, for the first time, provides evidence of the importance of oxidative modifications of two melanoma-associated antigens in eliciting anticancer immunity.