IDO1 and cancer: This review examines the prognostic value and association of expression with cancer clinical characteristics, as well as the response to the inhibition of a number of ICs expressed in solid tumor: B7-H1 (PD-L1, CD274), B7-H3 (CD276), B7-H4 (VTCN1), Galectin-3, Galectin-9, IDO1, CEACAM1 (CD66a), CD155 (PVR), Siglec-15 and cell surface protease ADAM17 (CD156b, TACE), which, although not an IC, is important in modulating the immune response and progression of tumors.