ADORA2A and neoplasm: eAdo can inhibit the activation of dendritic cells, the production of Th1/Th2 cytokines, the infiltration of cytotoxic T lymphocytes (CTLs), the activation, maturation, and cytotoxicity of natural killer (NK) cells, and enhance the pro-tumor effects of regulatory T (Treg) cells, TR1 cells and tumor-associated macrophage (TAM) by binding to A2aR expressed on immune cells (Figure 1) (10).