M1 polarization enhances the antitumor activity of chimeric antigen receptor macrophages in solid tumors

Background: Chimeric antigen receptor macrophage (CAR-M) therapy integrates CAR structure with macrophage function and shows promise for solid tumors. Because macrophage polarization affects antitumor activity, the authors hypothesized that inducing M1-type polarization would enhance CAR-M efficacy. Methods: A novel HER2-targeting CAR-M was generated using a humanized anti-HER2 scFv, a CD28 hinge, and the FcγRI transmembrane and intracellular domains. Phagocytosis, tumor-killing, and cytokine release were measured with or without M1-polarization (LPS + IFN-γ) pretreatment. Multiple syngeneic tumor models evaluated in vivo antitumor activity of M1-polarized CAR-Ms. Results: M1 polarization significantly enhanced CAR-M phagocytosis and cytotoxicity against target cells and increased costimulatory molecules and proinflammatory cytokines. In vivo, M1-polarized CAR-Ms suppressed tumor progression and prolonged survival in multiple murine models with enhanced cytotoxicity. Conclusions: The novel HER2-targeting CAR-M effectively eliminated HER2-positive tumor cells in vitro and in vivo; M1 polarization significantly improved antitumor activity, yielding stronger therapeutic effects in solid tumor immunotherapy.