CD8A and neoplasm: In inflamed and damaged tissues (i.e., cancers), extracellular adenosine can increase in concentration by up to 100 times and accumulate, inhibiting the effector functions of various immune cell populations—including CD8+ T cells, natural killer (NK) cells, dendritic cells (DC) and macrophages—but also enhance the proliferation and polarization of immunosuppressive cells, thereby promoting the progression of neoplasms [25].