Tumor-induced upregulation of A2AR on effector CD8 T cells promotes tumor growth in melanoma

Purinergic receptors sense extracellular nucleotide DAMPs such as ATP and adenosine, which are expressed in high concentrations in the tumor microenvironment (TME). A2AR, an adenosine receptor that is expressed on both T cells and tumor cells, promotes immunosuppression. However, the impact of the TME on changes in purinergic receptor expression on CD8 T cells, as well as the overall dynamic between A2AR expression and tumor control, have not been clearly elucidated. Using in vitro co-culture experiments and in vivo murine tumor models, we found that A2AR is significantly upregulated on effector, tumor-infiltrating CD8 T cells. This upregulation was independent of the hypoxia, which we identified via inhibition of HIF1A. We found that this upregulation was partially dependent on CD8 T cell-tumor contact, but independent of cognate antigen recognition, by using transwell co-cultures, as well as combinations of different transgenic lines of CD8 T cells and tumor cells. We confirmed this observation in vivo using transfer of activated OTI cells into B16.OVA-bearing mice. Ultimately, we observed that the upregulation depended on inhibitory receptors such as Tim3 via the antibody blockade of Tim3. Using CRISPR/Cas9-mediated knockout of A2AR on activated CD8 T cells, we found that tumor-bearing mice receiving A2AR knockout CD8 T cells had increased tumor control. Taken together, these results suggest that inhibitory receptor-dependent, TCR-independent signals in the TME promotes upregulation of A2AR on CD8 T cells, leading to impairment of CD8 T cell-mediated tumor control.