Palmitoylation-mediated alterations in FLT3-ITD localization and signaling. FLT3-ITD localization to the endoplasmic reticulum is enhanced by ZDHHC6-mediated S-palmitoylation. ER-localized FLT3-ITD aberrantly activates cytoplasmic STAT5 that promotes leukemia progression. Inhibition of palmitoylation by mutating the palmitoylated cysteine residue or targeting ZDHHC6 releases FLT3-ITD from the ER to the plasma membrane, where it activates the PI3K/AKT and RAS/MAPK pathways. Combined activation of STAT5, RAS/MAPK, and PI3K/AKT increases AML cell growth. In contrast, treatment with a depalmitoylation inhibitor decreased the cell-surface levels of FLT3-ITD and reduced PI3K/AKT and RAS/MAPK activation and led to enhanced inhibition of AML cell growth in combination with FLT3 TKI treatment.