Targeted inhibition of FLT3 overcomes the block to myeloid differentiation in 32Dcl3 cells caused by expression of FLT3/ITD mutations.
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.
Zheng
Rui
R
Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Friedman
Alan D
AD
Small
Donald
D
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
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