Chimeric Antigen Receptor-Macrophage Extracellular Vesicles Reprogram Immune Microenvironment for Cancer Therapy

Immunotherapy has become a new milestone in cancer treatment, with chimeric antigen receptor (CAR)-T cell therapy proven to be an effective method for treating hematologic malignancies. However, its efficacy in solid tumors remains limited. Macrophages, the most infiltrative innate immune cells in the tumor microenvironment, are being genetically engineered to express CARs, rapidly emerging as a promising new therapy for non-hematologic malignancies. Yet, CAR- Macrophages therapy is associated with unique acute toxicities and is susceptible to immunosuppressive mechanisms. Here, we propose using CAR macrophages-derived extracellular vesicles (CAR-MEVs) as an optimization of CAR-Ms therapy. Compared to CAR-Ms cells, CAR-MEVs exhibit lower toxicity and enhanced drug delivery capabilities. In an in vivo liver cancer model, CAR-MEVs administration proved safer than CAR-Ms therapy, reducing tumor burden and prolonging overall survival. In a humanized mouse model, CAR-MEVs further demonstrated the ability to induce a pro-inflammatory tumor microenvironment and enhance anti-tumor T cell activity. Mechanistically, CAR-MEVs target tumor cells, inducing immunogenic cell death (ICD) and subsequently leading to neutrophil infiltration in tumor tissues. We demonstrated that the anti-tumor effects of CAR-MEVs depend on neutrophils and are partially reliant on inducible nitric oxide synthase (iNOS). This study supports the potential of macrophage extracellular vesicles as a novel therapeutic approach for solid tumors.