Tumor cells can suppress the secretion of IL-6 in dendritic cells by the overexpression of indoleamine 2,3-dioxygenase (IDO), inhibit the reprogramming of Treg cells to Th17 cells, and further enhance the stability of Treg cells in the tumor microenvironment by silencing the expression of the Akt/mTOR pathway (35). Here, IDO2 is linked to neoplasm.