Resistance to cell death and evasion of immunosurveillance are major causes of cancer persistence and progression. Tumor cell-intrinsic activation of the RNA receptor retinoic acid-inducible gene-I (RIG-I) can trigger an immunogenic form of programmed tumor cell death, but its impact on antitumor responses remains largely unexplored. We show that activation of intrinsic RIG-I signaling induces melanoma cell death that enforces cross-presentation of tumor-associated antigens by bystander dendritic cells. This results in systemic expansion and activation of tumor-antigen specific T cells in vivo with subsequent regression of pre-established melanoma. These processes were dependent on the signaling hub MAVS and type I interferon (IFN-I) signaling in the host cell. Using melanoma cells deficient for the transcription factors IRF3 and IRF7, we demonstrate that RIG-I-activated tumor cells used as a vaccine are a relevant source of IFN-I during T cell cross-priming in vivo. Thus, our findings may facilitate translational development of personalized anticancer vaccines.
Keywords: Immunogenic cell death; RIG-I; anticancer vaccine; dendritic cells; nucleic acid receptors; pattern recognition receptors; personalized medicine; tumor immunotherapy.