IDO2 and neoplasm: These procancer modifications include the expression of antiapoptotic molecules which prevent tumor cell death [46]; growth factors which encourage tumor outgrowth [47], and immunosuppressive mediators such as VEGF, transforming growth factor-β (TGF-β), interleukin (IL)-10, indoleamine 2,3-dioxygenase (IDO), and programmed cell death-ligand 1 (PD-L1) which suppress antitumor immunity [48, 49].