FLT3 and acute myeloid leukemia: GAS6 has also been shown to be aberrantly expressed in AML cell lines and studies have found that high expression was correlated with worse prognosis.160 Both GAS6 and AXL have been associated with the development of resistance in AML cells in response to TK (FLT3) inhibitors and represent an important consideration for therapy development.144,161 To this effect, AML patients with FLT3-ITD mutations can initially have a good response to FLT3 inhibition but frequently develop resistance.43 This has led to the development and success of dual MERTK and FLT3 inhibitors in AML.