A_2AR eGFP reporter mouse enables elucidation of A_2AR 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 A_2AR receptor. Understanding of the mechanism by which A_2AR is regulated has been hindered by difficulty in identifying the cell types that express A_2AR due to a lack of robust antibodies for these receptors. To overcome this limitation, here an A_2AR eGFP reporter mouse is developed, enabling the expression of A_2AR during ongoing anti-tumor immune responses to be assessed. This reveals that A_2AR 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 MHCII^hiCD86^hi subset of type 2 conventional dendritic cells. In response to PD-L1 blockade, the emergence of PD-1⁺A_2AR^- cells correlates with successful therapeutic responses, whilst IL-18 is identified as a cytokine that potently upregulates A_2AR and synergizes with A_2AR deficiency to improve anti-tumor immunity. These studies provide insight into the biology of A_2AR in the context of anti-tumor immunity and reveals potential combination immunotherapy approaches.