Identifying and characterizing a novel activating mutation of the FLT3 tyrosine kinase in AML

Blood. 2004 Sep 15;104(6):1855-8. doi: 10.1182/blood-2004-02-0712. Epub 2004 Jun 3.


The FLT3 receptor is activated by juxtamembrane insertion mutations and by activation loop point mutations in patients with acute myeloid leukemia (AML). In a systematic tyrosine kinase gene exon resequencing study, 21 of 24 FLT3 exons were sequenced in samples from 53 patients with AML, 9 patients with acute lymphoblastic leukemia (ALL), and 3 patients with myelodysplasia samples. Three patients had novel point mutations at residue N841 that resulted in a change to isoleucine in 2 samples and to tyrosine in 1 sample. Introduction of FLT3-N841I cDNA into Ba/F3 cells led to interleukin-3 (IL-3)-independent proliferation, receptor phosphorylation, and constitutive activation of signal transducer and activator of transcription 5 (STAT5) and extracellular regulatory kinase (ERK), suggesting that the N841I mutation confers constitutive activity to the receptor. An FLT3 inhibitor (PKC412) inhibited the growth of Ba/F3-FLT3N841I cells (IC(50) 10 nM), but not of wild-type Ba/F3 cells cultured with IL-3. PKC412 also reduced tyrosine phosphorylation of the mutant receptor and inhibited STAT5 phosphorylation. Examination of the FLT3 autoinhibited structure showed that N841 is the key residue in a hydrogen-bonding network that likely stabilizes the activation loop. These results suggest that mutations at N841 represent a significant new activating mutation in patients with AML and that patients with such mutations may respond to small-molecule FLT3 inhibitors such as PKC412.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Cell Division / drug effects
  • Enzyme Activation
  • Female
  • Humans
  • Hydrogen Bonding
  • Interleukin-3 / pharmacology
  • Leukemia, Myeloid, Acute / enzymology*
  • Leukemia, Myeloid, Acute / genetics*
  • Leukemia, Myeloid, Acute / metabolism
  • Leukemia, Myeloid, Acute / pathology
  • Male
  • Middle Aged
  • Models, Molecular
  • Mutation / genetics*
  • Phosphorylation
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins / chemistry
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism*
  • Receptor Protein-Tyrosine Kinases / chemistry
  • Receptor Protein-Tyrosine Kinases / genetics*
  • Receptor Protein-Tyrosine Kinases / metabolism*
  • Signal Transduction
  • Staurosporine / analogs & derivatives*
  • Staurosporine / pharmacology
  • fms-Like Tyrosine Kinase 3


  • Interleukin-3
  • Proto-Oncogene Proteins
  • FLT3 protein, human
  • Receptor Protein-Tyrosine Kinases
  • fms-Like Tyrosine Kinase 3
  • Staurosporine
  • midostaurin