Single cell expression profiling of whole B16F10 melanoma tumors, treated with PBS or DCP-IL-12/FLT3L.

Dendritic cells (DCs) are specialized myeloid cells with the ability to uptake, process, and present antigens to T lymphocytes. They also generate cytokine and chemokine gradients that regulate immune cell trafficking, activation, and function. Monocyte-derived DCs (moDCs) pulsed with tumor antigens have been used as a platform for therapeutic vaccination in cancer. However, in spite of significant development and testing, antigen-loaded moDCs have delivered mixed clinical results. Here we present a DC therapy that uses a population of mouse or human DC progenitors (DCPs) engineered to produce two immunostimulatory cytokines, IL-12 and FLT3L. In the absence of antigen loading, cytokine-armored DCPs efficiently differentiated into conventional type I DCs (cDC1) and inhibited tumor growth in melanoma and autochthonous liver cancer models. Tumor response to DCP therapy involved synergy between IL-12 and FLT3L and was associated with early NK cell activation and massive effector T cell infiltration, robust M1-like macrophage programming, and ischemic tumor necrosis. Mechanistically, anti-tumor immunity was dependent on endogenous cDC1 expansion and interferon-γ (IFNγ) production and signaling, but did not require CD8+ T cell cytotoxicity. In one application, cytokine-armored DCPs synergized with antigen-specific CAR-T cells to eradicate intracranial gliomas in mice. Single cell expression profiling of whole B16F10 melanoma tumors, treated with PBS or DCP-IL-12/FLT3L, in triplicates.