SRC is a signaling mediator in FLT3-ITD- but not in FLT3-TKD-positive AML

TY - JOUR

T1 - SRC is a signaling mediator in FLT3-ITD- but not in FLT3-TKD-positive AML

AU - Leischner, Hannes

AU - Albers, Corinna

AU - Grundler, Rebekka

AU - Razumovskaya, Elena

AU - Spiekermann, Karsten

AU - Bohlander, Stefan

AU - Rönnstrand, Lars

AU - Götze, Katharina

AU - Peschel, Christian

AU - Duyster, Justus

PY - 2012/4/26

Y1 - 2012/4/26

N2 - 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.

AB - 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.

KW - Animals

KW - Blotting, Western

KW - Cell Proliferation

KW - Cells, Cultured

KW - Flow Cytometry

KW - Humans

KW - Immunoprecipitation

KW - Leukemia, Myeloid, Acute

KW - Mice

KW - Mice, Inbred C3H

KW - NIH 3T3 Cells

KW - Phosphorylation

KW - Protein-Tyrosine Kinases

KW - RNA, Small Interfering

KW - STAT5 Transcription Factor

KW - Signal Transduction

KW - Tandem Repeat Sequences

KW - fms-Like Tyrosine Kinase 3

KW - src Homology Domains

KW - src-Family Kinases

KW - Comparative Study

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1182/blood-2011-07-365726

DO - 10.1182/blood-2011-07-365726

M3 - SCORING: Journal article

C2 - 22411868

VL - 119

SP - 4026

EP - 4033

JO - BLOOD

JF - BLOOD

SN - 0006-4971

IS - 17

ER -