A 2A R eGFP reporter mouse enables elucidation of A 2A R 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 2A R receptor. Understanding of the mechanism by which A 2A R is regulated has been hindered by difficulty in identifying the cell types that express A 2A R due to a lack of robust antibodies for these receptors. To overcome this limitation, here an A 2A R eGFP reporter mouse is developed, enabling the expression of A 2A R during ongoing anti-tumor immune responses to be assessed. This reveals that A 2A R 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 hi CD86 hi subset of type 2 conventional dendritic cells. In response to PD-L1 blockade, the emergence of PD-1 + A 2A R - cells correlates with successful therapeutic responses, whilst IL-18 is identified as a cytokine that potently upregulates A 2A R and synergizes with A 2A R deficiency to improve anti-tumor immunity. These studies provide insight into the biology of A 2A R in the context of anti-tumor immunity and reveals potential combination immunotherapy approaches.