FLT3 and acute myeloid leukemia: In AML patients containing the internal tandem duplication (ITD) in the Fms-like tyrosine kinase (FLT3) gene, lack of elimination of LSCs due to their strong drug resistance is presumably responsible for failed treatment with the small molecules of FLT3 tyrosine kinase inhibitors (TKIs) (Levis, 2011; Horton and Huntly, 2012; Smith et al., 2012).