title: Targeted inhibition of FLT3 overcomes the block to myeloid differentiation in 32Dcl3 cells caused by expression of FLT3/ITD mutations.
abstract: Internal tandem duplication (ITD) mutations of the juxtamembrane domain-coding sequence of the FLT3 gene are found in up to 34% of patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. FLT3/ITDs result in constitutive activation of the tyrosine kinase domain and transform growth factor-dependent cell lines. FLT3 activation leads to antiapoptotic and proliferative signals, but little is known about the impact of FLT3/ITDs on differentiation. This study was designed to investigate the effect of FLT3/ITD expression on the differentiation of the 32Dcl3 (32D) myeloblastic cell line to neutrophils in response to granulocyte colony-stimulating factor (G-CSF). Expression of FLT3/ITD completely blocked morphologic differentiation and induction of myeloperoxidase (MPO), lysozyme, and CCAAT/enhancer-binding protein epsilon (C/EBPepsilon) in response to G-CSF. Wild-type FLT3 and vector-transfected 32D cells were able to differentiate, although the maturation of FLT3-transfected cells was delayed by FLT3 ligand (FL) stimulation. CEP-701, a potent FLT3 tyrosine kinase inhibitor, overcame the morphologic block in differentiation caused by FLT3/ITD expression and allowed G-CSF induction of myeloid maturation markers. These findings suggest that blocking differentiation may be one of the mechanisms by which FLT3/ITDs contribute to leukemogenesis. CEP-701 and other FLT3 inhibitors may be useful for overcoming the block to differentiation (as well as the block to apoptosis) in the leukemic cells of patients with AML.
authors.affiliation: Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Rui
authors.initials: R
authors.lastname: Zheng
authors.forename: Alan D
authors.initials: AD
authors.lastname: Friedman
authors.forename: Donald
authors.initials: D
authors.lastname: Small
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002227:Carbazoles / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D005663:Furans; D006801:Humans; D007211:Indoles; D007951:Leukemia, Myeloid / Q000235:genetics* / Q000473:pathology; D051379:Mice; D009154:Mutation; D022423:Myeloid Cells / Q000166:cytology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D020080:Tandem Repeat Sequences; D014162:Transfection; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D002227:Carbazoles; D005663:Furans; D007211:Indoles; D011518:Proto-Oncogene Proteins; C119379:lestaurtinib; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3