Several mechanisms have been reported by which VEGFA suppresses tumor immune responses, including promoting M2 polarization of macrophages and thereby causing them to secrete antiinflammatory cytokines, such as IL-10 and TGF-β (41); inhibiting dendritic cell maturation (42); upregulating immune checkpoint regulators, such as indoleamine 2,3-dioxygenase (42) and PD-L1/2 in myeloid cells (42, 43); and recruiting myeloid-derived suppressor cells and regulatory T cells into tumors (44, 45). Here, IDO2 is linked to neoplasm.