title: FLT3-ITD-TKD dual mutants associated with AML confer resistance to FLT3 PTK inhibitors and cytotoxic agents by overexpression of Bcl-x(L).
abstract: FLT3 (fms-like tyrosine kinase 3) is constitutively activated in about 30% of patients with acute myeloid leukemia (AML) and represents a disease-specific molecular marker. Although FLT3-LM (length mutation) and TKD (tyrosine kinase domain) mutations have been considered to be mutually exclusive, 1% to 2% of patients carry both mutations. However, the functional and clinical significance of this observation is unclear. We demonstrate that FLT3-ITD-TKD dual mutants induce drug resistance toward PTK inhibitors and cytotoxic agents in in vitro model systems. As molecular mechanisms of resistance, we found that FLT3-ITD-TKD mutants cause hyperactivation of STAT5 (signal transducer and activator of transcription-5), leading to upregulation of Bcl-x(L) and RAD51 and arrest in the G(2)M phase of the cell cycle. Overexpression of Bcl-x(L) was identified as the critical mediator of drug resistance and recapitulates the PTK inhibitor and daunorubicin-resistant phenotype in FLT3-ITD cells. The combination of rapamycin, a selective mTOR inhibitor, and FLT3 PTK inhibitors restored the drug sensitivity in FLT3 dual mutant-expressing cells. Our data provide the molecular basis for understanding clinical FLT3 PTK inhibitor resistance and point to therapeutical strategies to overcome drug resistance in patients with AML.
authors.affiliation: Department of Medicine III, University Hospital Grosshadern, CCG "Leukemia," GSF-National Research Center for Environment and Health, Marchioninistr 25, 81377 Munich, Germany.
authors.forename: Ksenia
authors.initials: K
authors.lastname: Bagrintseva
authors.forename: Stefanie
authors.initials: S
authors.lastname: Geisenhof
authors.forename: Ruth
authors.initials: R
authors.lastname: Kern
authors.forename: Sabine
authors.initials: S
authors.lastname: Eichenlaub
authors.forename: Carola
authors.initials: C
authors.lastname: Reindl
authors.forename: Joachim W
authors.initials: JW
authors.lastname: Ellwart
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hiddemann
authors.forename: Karsten
authors.initials: K
authors.lastname: Spiekermann
mesh_terms: D000208:Acute Disease; D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007951:Leukemia, Myeloid / Q000188:drug therapy*; D051379:Mice; D008894:Milk Proteins / Q000187:drug effects; D017354:Point Mutation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D051135:Rad51 Recombinase; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000494:pharmacology*; D050799:STAT5 Transcription Factor; D020080:Tandem Repeat Sequences; D015534:Trans-Activators / Q000187:drug effects; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects; D051020:bcl-X Protein; D051941:fms-Like Tyrosine Kinase 3
chemical_list: C494811:BCL2L1 protein, human; C494812:Bcl2l1 protein, mouse; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D051020:bcl-X Protein; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse