IDO1 and neoplasm: The function of DCs can be potentially influenced by the cytokines in the TME through (1) impaired migratory capacity as well as decreased synthesis of costimulatory components (CD86/80) by TGF-β (147, 148); (2) prevented DCs maturation by IL-6-gp130-STAT3 axis; and (3) inhibited activity by Indoleamine 2,3-dioxygenase 1 (IDO, will be discussed in Section “Suppressive tumor microenvironment”).