IFN-γ and TLR9 signaling reprogram tumor-associated macrophages to promote antitumor immunity in melanoma

Tumor-associated macrophages (TAMs) often adopt immunosuppressive phenotypes that promote tumor progression and limit the efficacy of immunotherapy. Although Toll-like receptor 9 (TLR9) agonists and interferon-γ (IFN-γ) possess immunostimulatory properties, their antitumor efficacy as monotherapy remains limited, particularly in poorly immunogenic tumors. Here, we investigated whether coordinated activation of innate immune pathways could reprogram macrophages and enhance antitumor immunity in melanoma. Using cap analysis of gene expression (CAGE), we found that combined CpG DNA and IFN-γ stimulation induced extensive transcriptional reprogramming in macrophages, characterized by activation of M1-associated genes, enhancer remodeling, alternative transcription start site usage, and induction of transcription factors associated with inflammatory and cytotoxic responses. Functionally, this combination also markedly enhanced macrophage-mediated phagocytosis of live tumor cells.