Targeting the exosomal CaMK2A-ZDHHC3-GPX4 pathway reprograms tumor-associated macrophages and enhances anti-PD-1/PD-L1 immunotherapy in gastric cancer.

Gastric cancer (GC) remains a major global health challenge, characterized by poor outcomes driven by an immunosuppressive tumor microenvironment (TME). Tumor-associated macrophages (TAMs), particularly the M2 subtype, are central mediators of immune evasion and therapeutic resistance. While tumor-derived exosomes are key regulators of intercellular communication, the mechanisms by which they modulate TAM fate remain unclear. Proteomic profiling, molecular assays, and in vivo models were used to identify GC-derived exosomal cargos regulating macrophage polarization. The CaMK2A-ZDHHC3-GPX4 axis was dissected using phosphorylation, palmitoylation, and genetic perturbation analyses. The therapeutic implications were evaluated through macrophage-specific GPX4 ablation and anti-PD-1/PD-L1 blockade in murine GC models. We identified exosomal CaMK2A as a critical determinant of TAM polarization. Internalized CaMK2A phosphorylates ZDHHC3 at Thr176, enhancing GPX4 S-palmitoylation at Cys10, preventing its lysosomal degradation, and stabilizing GPX4 protein. This cascade suppresses macrophage ferroptosis and promotes M2 polarization, fostering tumor proliferation and metastasis. Conversely, GPX4 deletion in macrophages restrains tumor growth and synergizes with PD-1/PD-L1 blockade to enhance antitumor immunity. Clinically, GPX4 is upregulated in GC, enriched in TAMs, and predicts poor prognosis. Our study reveals a previously unrecognized CaMK2A-ZDHHC3-GPX4 signaling axis that couples ferroptosis resistance to immunosuppressive TAM polarization. Targeting GPX4 or disrupting exosomal CaMK2A signaling may reprogram the TME and potentiate immune checkpoint therapy in GC.