Atmospheric pressure plasma-activated medium activates macrophages toward an antitumor M1 phenotype by modulating the SIRPα phagocytic checkpoint.

Macrophage-mediated tumor clearance is frequently restricted by the immunosuppressive tumor microenvironment. This study investigates the immunomodulatory effects of plasma-activated medium (PAM) on macrophage pro-inflammatory activation and antitumor function. Murine RAW264.7 and primary bone marrow-derived macrophages were treated with PAM generated by a helium atmospheric pressure plasma jet. Phenotypic changes and underlying signaling mechanisms were assessed. Functional enhancements in macrophage recruitment and tumor engulfment were quantified using chemotaxis and 3D confocal co-culture assays with Panc02 pancreatic cancer cells. Results show that PAM promotes macrophage activation by increasing spatial recruitment via pro-inflammatory chemokine secretion and enhancing tumor cell engulfment. Mechanistically, PAM drives this functional shift through hierarchical activation of the TLR4/NF-κB and PI3K/AKT signaling cascades. Furthermore, while hydrogen peroxide alone triggers a compensatory upregulation of the inhibitory SIRPα receptor, the reactive oxygen and nitrogen species (RONS) in PAM bypass this negative feedback to directly downregulate SIRPα. These findings demonstrate that PAM-mediated oxidative modulation effectively suppresses the "don't-eat-me" signal and enhances innate antitumor immunity, providing a potential strategy for cancer immunotherapy.