ADORA2A and neoplasm: Notably, in the tumor microenvironment, excess ATP can be degraded by CD39 to cAMP, which is subsequently converted to adenosine by CD73 expressed on the surface of regulatory T cells (Tregs), which binds to the A2A adenosine receptor (A2AR) on NK cells, thereby negatively regulating the maturation and anti-tumor response of NK cells.