Abstract
Internal tandem duplication (ITD) mutations in the FLT3 tyrosine kinase have been detected in approximately 20% of acute myeloid leukemia (AML) patients. Patients harboring FLT3/ITD mutations have a relatively poor prognosis. FLT3/ITD results in constitutive autophosphorylation of the receptor and factor-independent survival. Previous studies have shown that FLT3/ITD activates the signal transducers and activators of transcription 5 (STAT5), p42/p44 mitogen-activated protein kinase [MAPK; extracellular signal-regulated kinase (ERK) 1/2], and phosphatidylinositol 3-kinase/Akt pathways. We herein provide biochemical and biological evidence that ribosomal S6 kinase 1 (RSK1) and protein kinase A (PKA) are the two principal kinases that mediate the antiapoptotic function of FLT3/ITD via phosphorylation of BAD at Ser112. Inhibiting both MAPK kinase (MEK)/ERK and PKA pathways by a combination of U0126 (10 micromol/L) and H-89 (5 micromol/L) reduced most of BAD phosphorylation at Ser112 and induced apoptosis to a level comparable with that induced by FLT3 inhibitor AG1296 (5 micromol/L) in BaF3/FLT3/ITD cells. RNA interference of RSK1 or PKA catalytic subunit reduced BAD phosphorylation and induced apoptosis. The MEK inhibitor U0126 and/or the PKA inhibitor H-89 greatly enhanced the efficacy of the FLT3 inhibitor AG1296, suggesting that combining FLT3/ITD downstream pathway inhibition with FLT3 inhibitors may be a viable therapeutic strategy for AML caused by a FLT3/ITD mutation.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Apoptosis / drug effects
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Apoptosis / genetics
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Butadienes / pharmacology
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Carrier Proteins / metabolism*
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Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
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Cyclic AMP-Dependent Protein Kinases / metabolism*
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Drug Synergism
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Enzyme Activation
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Hematopoietic Stem Cells / cytology
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Hematopoietic Stem Cells / drug effects
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Hematopoietic Stem Cells / enzymology
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Interleukin-3 / deficiency*
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Interleukin-3 / metabolism
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Isoquinolines / pharmacology
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MAP Kinase Signaling System / drug effects
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Mice
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Molecular Sequence Data
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Mutation*
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Nitriles / pharmacology
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Phosphorylation
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Protein Kinase Inhibitors / pharmacology
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Proto-Oncogene Proteins / antagonists & inhibitors
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Proto-Oncogene Proteins / genetics*
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2 / biosynthesis
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RNA Interference
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Receptor Protein-Tyrosine Kinases / antagonists & inhibitors
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Receptor Protein-Tyrosine Kinases / genetics*
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Receptor Protein-Tyrosine Kinases / metabolism
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Ribosomal Protein S6 Kinases, 90-kDa / antagonists & inhibitors
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Ribosomal Protein S6 Kinases, 90-kDa / genetics
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Ribosomal Protein S6 Kinases, 90-kDa / metabolism*
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Serine / metabolism
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Sulfonamides / pharmacology
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Tandem Repeat Sequences / genetics
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Tyrphostins / pharmacology
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bcl-Associated Death Protein
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bcl-X Protein
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fms-Like Tyrosine Kinase 3
Substances
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Bad protein, mouse
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Bcl2l1 protein, mouse
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Butadienes
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Carrier Proteins
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Interleukin-3
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Isoquinolines
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Nitriles
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Protein Kinase Inhibitors
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Sulfonamides
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Tyrphostins
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U 0126
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bcl-Associated Death Protein
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bcl-X Protein
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6,7-dimethoxy-3-phenylquinoxaline
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Serine
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Flt3 protein, mouse
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Receptor Protein-Tyrosine Kinases
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fms-Like Tyrosine Kinase 3
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Ribosomal Protein S6 Kinases, 90-kDa
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Rps6ka1 protein, mouse
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Cyclic AMP-Dependent Protein Kinases
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N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide