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Abstract A100: Crosstalk between regulatory T cells and tumor-associated dendritic cells controls antitumor immunity in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is marked by an abundant fibroinflammatory microenvironment. Regulatory T (Treg) cell infiltration constitutes a prominent feature of PDA. However, the immunomodulatory function of Treg cells in PDA remains poorly understood. Using orthotopic and autochthonous mouse models of PDA we have found that Treg cell ablation is sufficient to evoke effective anti-tumor immune response in early and advanced pancreatic neoplasia. This response is dependent on IFN-γ producing cytotoxic CD8+ T cells. We show that Treg cells engage in extended interactions with tumor-associated CD11c+ dendritic cells (DCs) and restrain their immunogenic function by suppressing the expression of costimulatory ligands necessary for CD8+ T cell activation. Consequently, tumor-associated CD8+ T cells fail to display effector activities when Treg cell ablation is combined with DC depletion. We propose that tumor-infiltrating Treg cells promote immune-tolerance by suppressing DC immunogenicity. Therapeutic manipulation this axis might provide an effective approach for the targeting of PDA. Citation Format: Jung-Eun Jang, Cristina H. Hajdu, George Miller, Michael L. Dustin, Dafna Bar-Sagi. Crosstalk between regulatory T cells and tumor-associated dendritic cells controls antitumor immunity in pancreatic cancer [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A100.