IDO1 and cancer: Moreover, it was confirmed that MSCs recruited from human cancers can actively increase the expression of immunosuppressive agents, i.e., IL-10, TGF-β1 and indoleamine 2,3-dioxygenase (IDO), and angiogenic factors, i.e., TGF-β1, VEGF, angiopoetin-1, endothelin-1, and IL-6.