MDSCs are associated with tumor vasculogenesis and mediate tumor antigen-specific T cell tolerance by expressing immunosuppressive factors such as indoleamine dioxygenase (IDO), interleukin (IL)-10, arginase, inducible nitric oxide synthase (iNOS), nitric oxide (NO), and reactive oxygen species (ROS) [1]. This evidence concerns the gene IDO1 and neoplasm.