NT5E and neoplasm: The means by which Treg cells suppress tumor-specific T cells includes 1) secretion of suppressor cytokines IL-10 and TGF-β [11]; 2) suppression of the function of APC through CTLA4 pathway [12]; 3) hydrolysis of extracellular ATP to inhibitory adenosine by CD39 and CD73 [13]; and 4) transferring inhibitory cAMP from Treg cells to effector T cells through gap junction [14].