Abstract 3278: EOS100850 potently restores adenosine A2Areceptor-dependent suppression of T cell function in the adenosine rich tumor microenvironment
Authors: Houthuys Erica , Basilico Paola , Bodo Veronique , Brouwer Margreet , Detheux Michel , Driessens Gregory , Gomes Bruno , Hermant Annelise , Hoofd Catherine , Lambolez Florence , Leroy Xavier , Marillier Reece , Martinoli Chiara , Mercier Marjorie , Nyawouame Florence , Prasad Shruthi , Scoumanne Ariane , Crosignani Stefano 
Published: August 2019

Abstract
Adenosine is a potent immunosuppressive metabolite that is often found elevated in the extracellular tumor microenvironment (TME). We determined concentrations of extracellular adenosine in different patient-derived xenografts (PDX) from 7 different histological types, in which extracellular median adenosine concentrations were shown to range from 0.5 to 45 µM, with the overall median adenosine concentration being about 4.5 µM. Adenosine concentration in the non-tumorous subcutaneous space in mice was measured at about 0.5 µM. Adenosine in the TME is generated mainly by the concerted action of the ectonucleotidases CD39 and CD73. The expression of these enzymes across various cancer types was evaluated by flow cytometry in dissociated human tumor biopsies. CD73 and CD39 were strongly expressed by multiple tumor-infiltrating T cell types. Tumor-associated myeloid cells mostly expressed CD39 and high frequencies of EpCAM+ tumor cells strongly expressed CD73. These data strongly suggest that adenosine levels could be further increased compared to non-immune-infiltrated PDX.Adenosine activates 4 G protein-coupled receptor subtypes, of which the adenosine A2A receptor in particular suppresses innate and adaptive immune cell responses leading to suppression of anti-tumor immunity. Among the 4 adenosine receptors, we confirmed the A2A receptor as the main adenosine receptor expressed in CD4+ and CD8+ T cells, natural killer cells, monocytes, and dendritic cells. Stimulation of these immune cell subsets further increased A2A receptor expression. A2B receptor was expressed at very low levels in stimulated CD4+ and CD8+ T cells and in monocytes and immature DCs. A1 and A3 receptors were hardly detected in these subsets of immune cells. EOS100850, a highly potent and selective A2A receptor antagonist, was characterized in various in vitro functional assays. A2A receptor activation by a selective agonist suppressed priming of mouse OVA-specific OT1 T cells and subsequent antigen-specific CD8+ T cell cytotoxicity in a co-culture assay of effector CD8+ T cells and target cancer cells. This A2A receptor-mediated immune suppression was potently and dose-dependently reversed by EOS100850. In a mixed lymphocyte reaction between human dendritic cells and T cells, EOS100850 blocked the adenosine-dependent inhibition of T cell proliferation and secretion of IFNg, TNFa and IL-2 in a dose-dependent manner. In conclusion, extracellular adenosine as well as adenosine pathway components were strongly present across multiple tumor types, and across multiple tumor-associated cell types. In addition, EOS100850, a highly potent A2A receptor antagonist, reversed A2A receptor-mediated suppression of T cell priming, cytotoxicity, cytokine production and proliferation.
Citation Format: Erica Houthuys, Paola Basilico, Veronique Bodo, Margreet Brouwer, Michel Detheux, Gregory Driessens, Bruno Gomes, Annelise Hermant, Catherine Hoofd, Florence Lambolez, Xavier Leroy, Reece Marillier, Chiara Martinoli, Marjorie Mercier, Florence Nyawouame, Shruthi Prasad, Ariane Scoumanne, Stefano Crosignani. EOS100850 potently restores adenosine A2Areceptor-dependent suppression of T cell function in the adenosine rich tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3278.