Dendritic cells (DCs) play a key role in the orchestration of antitumor immune responses. The cDC1 subset was demonstrated as essential for tumor control and response to immunotherapies in mice, but its precise role in human is largely unexplored. In our study, we combined the analysis of large cohorts of fresh breast and ovarian primary tumors and of public transcriptomic data sets to elucidate human cDC1 functions and clinical impact compared with other DC subsets. We identified a key role for intratumoral cDC1 in producing selectively type III interferon (IFN-III), strongly associated with cytokines and chemokines promoting cytotoxic immune cell recruitment and activation. Of utmost importance, we also revealed a positive impact of IFN-III and cDC1 on patient outcome in many human cancers and identified TLR3-triggering as a therapeutic strategy to trigger IFN-III production by tumor-associated cDC1. These data may pave the way for new IFN or cDC1-targeting antitumor therapies.

Citation Format: Margaux Hubert, Coline Couillault, Thien Phong Vu Manh, Vincent Ollion, Helene Lopez-Mestre, Nabil Rahmouni, Janice KIielbassa, Celine Rodriguez, Christophe Sajous, Benoit Dumont, Anne-Claire Doffin, Isabelle Treilleux, Olivier Tredan, Marc Dalod, Nathalie BendrissS-Vermare, Christophe Caux, Jenny Valladeau-Guilemomd. IFN-III is selectively produced by cDC1 and predicts good clinical outcome in human breast cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A70.