IDO1 and cancer: Production of IL-8, which regulates their mobilization and activity, as well as supports the extravasation of cancer cells [85,126]Promotion of malignant angiogenesis and invasion through secretion of proteases involved in ECM remodeling i.e., MMP-9 [127]Expression of PD-L1 and IDO, as well as NOS overexpression, and secretion of the molecules involved in Treg recruitment (i.e., IL-17) [128]