A2AR eGFP reporter mouse enables elucidation of A2AR expression dynamics during anti-tumor immune responses

There is significant clinical interest in targeting adenosine-mediated immunosuppression, with several small molecule inhibitors having been developed for targeting the A2AR receptor. Understanding of the mechanism by which A2AR is regulated has been hindered by difficulty in identifying the cell types that express A2AR due to a lack of robust antibodies for these receptors. To overcome this limitation, here an A2AR eGFP reporter mouse is developed, enabling the expression of A2AR during ongoing anti-tumor immune responses to be assessed. This reveals that A2AR is highly expressed on all tumor-infiltrating lymphocyte subsets including Natural Killer (NK) cells, NKT cells, γδ T cells, conventional CD4+ and CD8+ T lymphocytes and on a MHCIIhiCD86hi subset of type 2 conventional dendritic cells. In response to PD-L1 blockade, the emergence of PD-1+A2AR- cells correlates with successful therapeutic responses, whilst IL-18 is identified as a cytokine that potently upregulates A2AR and synergizes with A2AR deficiency to improve anti-tumor immunity. These studies provide insight into the biology of A2AR in the context of anti-tumor immunity and reveals potential combination immunotherapy approaches.