IDO1 and neoplasm: We examined the expression of four HDAC genes in addition to ARG1 (encodes arginase 1 enzyme, which synthesizes nitric oxide), ITGAL (CD11a, which could be an important mediator for PMN-MDSCs migration into tumor tissue), and IDO (encodes indoleamine 2,3-dioxygenase enzyme, which possess an immunosuppressive function).