Trained immunity-primed DLL3-targeted CAR macrophages for the eradication of small cell lung cancer

Background Small cell lung cancer (SCLC) is highly malignant with limited treatment options. Chimeric antigen receptor macrophages (CAR-Ms) show potential for solid tumor therapy due to their phagocytic activity, tissue penetration, and immunomodulatory functions, but their application in SCLC remains unexplored. Delta-like ligand 3 (DLL3), a SCLC-specific membrane antigen, represents a promising therapeutic target. Here, we developed a DLL3-targeted CAR-M therapy and an enhanced strategy for SCLC immunotherapy. Methods DLL3-specific CAR-Ms were generated by introducing a CAR construct (DLL3-ScFv-CD8-CD3ζ) into murine and human macrophages via lentiviral transduction. A β-glucan (BG)-based training protocol was established to enhance CAR-M functionality. Phagocytic and cytotoxic activities were evaluated by flow cytometry and bioluminescence assays, and in vivo antitumor efficacy was assessed in immunodeficient and immunocompetent mouse models. Results Engineered CAR-Ms exhibited potent phagocytic and cytotoxic activity against DLL3-positive cells and effectively infiltrated and eliminated tumor spheroids in 3D culture systems. Intravenously administered CAR-Ms suppressed DLL3-positive lung cancer growth in both immunodeficient and immunocompetent models without discernible toxicity. Importantly, BG training enhanced CAR-M functionality by conferring sustained anti-tumor immunity, amplifying inflammatory and interferon pathway activation, and remodeling the tumor microenvironment through epigenetic and metabolic reprogramming. These findings establish BG-trained, DLL3-targeting CAR-Ms as a promising therapeutic approach for SCLC. Conclusion Anti-DLL3 CAR-Ms demonstrate significant potential for solid tumor treatment and may offer a viable clinical strategy for SCLC in the future.