While apoptotic Treg cells are a major source of ATP in the tumor microenvironment [158], Treg cells also express CD39 and CD73 and thus generate a large amount of adenosine from ATP in the tumor microenvironment, which inhibits the function and proliferation of effector T cells via the adenosine A2A receptor [125]. The gene discussed is ADORA2A; the disease is neoplasm.