In particular, CD39 and/or CD73 (over)expression has been detected on the surface of tumor cells (39, 44–51), cancer-associated fibroblasts (CAFs) (52–54), mesenchymal stem cells and stromal cells (55–57), endothelial cells (ECs) (45, 46, 51), myeloid derived suppressor cells (MDSCs) (58–60), tumor associated macrophages (TAMs) (53, 61), Tregs (46, 62–64), Th17 cells (65) and of antigen experienced/exhausted conventional CD4+ and CD8+ T cells (64, 66–68). The gene discussed is ENTPD1; the disease is cancer.