The inhibitory factors of solid tumors are known to be composed by a complex composition of immunosuppressive molecules, such as TGF-β, IL-10, IDO, PGE2, VEGF, iNOS, and ROS, produced by regulatory immune cells, such as Treg cells, MDSCs, and M2-TAMs, as well as by tumor cells themselves.730 These factors generate a chronic inflammatory and immunosuppressive TME, accelerating tumor progression. The gene discussed is IDO1; the disease is neoplasm.