While AML blasts can prompt the secretion of stimulatory cytokines such as tumor necrosis factor (TNF)-α, IL-1β, and IL-6 by monocytes, upregulation of inducible T cell costimulator ligand (ICOSLG) on AML blasts can provide co-stimulation through ICOS for the conversion and expansion of Tregs sustaining high Foxp3 and CD25 expression and a suppressive cell function with secretion of inhibitory cytokines, including transforming growth factor (TGF)-β and IL-10 [153]. The gene discussed is ICOSLG; the disease is acute myeloid leukemia.