Activating a collaborative innate-adaptive immune response to control metastasis

Tumor-associated macrophages (TAMs) promote metastasis and inhibit T cells, but macrophages can be polarized to kill Cancer cells. Macrophage polarization could thus be a strategy for controlling Cancer. We show that macrophages from metastatic pleural effusions of breast Cancer patients can be polarized to kill Cancer cells with monophosphoryl lipid A (MPLA) and interferon (IFN) γ. MPLA + IFNγ injected intratumorally or intraperitoneally reduces primary tumor growth and metastasis in breast Cancer mouse models, suppresses metastasis, and enhances chemotherapy response in an ovarian Cancer model. Both macrophages and T cells are critical for the treatment's anti-metastatic effects. MPLA + IFNγ stimulates type I IFN signaling, reprograms CD206⁺ TAMs to inducible NO Synthase (iNOS)⁺ macrophages, and activates cytotoxic T cells through macrophage-secreted interleukin-12 (IL-12) and tumor necrosis factor alpha (TNFα). MPLA and IFNγ are used individually in clinical practice and together represent a previously unexplored approach for engaging a systemic anti-tumor immune response.