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.