title: SRC is a signaling mediator in FLT3-ITD- but not in FLT3-TKD-positive AML.
abstract: Mutations of Fms-like tyrosine kinase 3 (FLT3) are among the most frequently detected molecular abnormalities in AML patients. Internal tandem duplications (ITDs) are found in approximately 25% and point mutations within the second tyrosine kinase domain (TKD) in approximately 7% of AML patients. Patients carrying the FLT3-ITD but not the FLT3-TKD mutation have a significantly worse prognosis. Therefore, both FLT3 mutations seem to exert different biologic functions. FLT3-ITD but not FLT3-TKD has been shown to induce robust activation of the STAT5 signaling pathway. In the present study, we investigated the mechanisms leading to differential STAT5 activation and show that FLT3-ITD but not FLT3-TKD uses SRC to activate STAT5. Coimmunoprecipitation and pull-down experiments revealed an exclusive interaction between SRC but not other Src family kinases and FLT3-ITD, which is mediated by the SRC SH2 domain. We identified tyrosines 589 and 591 of FLT3-ITD to be essential for SRC binding and subsequent STAT5 activation. Using site-specific Abs, we found that both residues were significantly more strongly phosphorylated in FLT3-ITD compared with FLT3-TKD. SRC inhibition and knock-down blocked STAT5 activation and proliferation induced by FLT3-ITD but not by FLT3-TKD. We conclude that SRC might be a therapeutic target in FLT3-ITD(+) AML.
authors.affiliation: Department of Internal Medicine III, Klinikum rechts der Isar, Technical University of Munich, Ismaningerstrasse 22, Munich, Germany.
authors.forename: Hannes
authors.initials: H
authors.lastname: Leischner
authors.forename: Corinna
authors.initials: C
authors.lastname: Albers
authors.forename: Rebekka
authors.initials: R
authors.lastname: Grundler
authors.forename: Elena
authors.initials: E
authors.lastname: Razumovskaya
authors.forename: Karsten
authors.initials: K
authors.lastname: Spiekermann
authors.forename: Stefan
authors.initials: S
authors.lastname: Bohlander
authors.forename: Lars
authors.initials: L
authors.lastname: Rönnstrand
authors.forename: Katharina
authors.initials: K
authors.lastname: Götze
authors.forename: Christian
authors.initials: C
authors.lastname: Peschel
authors.forename: Justus
authors.initials: J
authors.lastname: Duyster
mesh_terms: D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D047468:Immunoprecipitation; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D008809:Mice, Inbred C3H; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D020080:Tandem Repeat Sequences / Q000235:genetics*; D051941:fms-Like Tyrosine Kinase 3 / Q000378:metabolism*; D018909:src Homology Domains; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D034741:RNA, Small Interfering; D050799:STAT5 Transcription Factor; C497970:FLT3 protein, human; D011505:Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; D019061:src-Family Kinases