Contrary to classical and intermediate monocytes which represent proinflammatory patterns, non-classical monocytes show increased expression of molecules such as PD-L1 (programmed cell death 1 ligand), PD-L2, Arginase1, IDO (Indoleamine-pyrrole 2,3-dioxygenase), and CD163; this suggests their immunosuppressive potential in the course of malignant neoplasms [16,17]. This evidence concerns the gene IDO1 and cancer.