title: FLT3 signals via the adapter protein Grb10 and overexpression of Grb10 leads to aberrant cell proliferation in acute myeloid leukemia.
abstract: The adaptor protein Grb10 plays important roles in mitogenic signaling. However, its roles in acute myeloid leukemia (AML) are predominantly unknown. Here we describe the role of Grb10 in FLT3-ITD-mediated AML. We observed that Grb10 physically associates with FLT3 in response to FLT3-ligand (FL) stimulation through FLT3 phospho-tyrosine 572 and 793 residues and constitutively associates with oncogenic FLT3-ITD. Furthermore endogenous Grb10-FLT3 association was observed in OCI-AML-5 cells. Grb10 expression did not alter FLT3 receptor activation or stability in Ba/F3-FLT3 cells. However, expression of Grb10 enhanced FL-induced Akt phosphorylation without affecting Erk or p38 phosphorylation in Ba/F3-FLT3-WT and Ba/F3-FLT3-ITD. Selective Grb10 depletion reduced Akt phosphorylation in Ba/F3-FLT3-WT and OCI-AML-5 cells. Grb10 transduces signal from FLT3 by direct interaction with p85 and Ba/F3-FLT3-ITD cells expressing Grb10 exhibits higher STAT5 activation. Grb10 regulates the cell cycle by increasing cell population in S-phase. Expression of Grb10 furthermore resulted in an increased proliferation and survival of Ba/F3-FLT3-ITD cells as well as increased colony formation in semisolid culture. Grb10 expression was significantly increased in AML patients compared to healthy controls and was also elevated in patients carrying FLT3-ITD mutants. The elevated Grb10 expression partially correlated to relapse as well as to poor prognosis. These results suggest that Grb10 binds to both normal and oncogenic FLT3 and induces PI3K-Akt and STAT5 signaling pathways resulting in an enhanced proliferation, survival and colony formation of hematopoietic cells.
authors.affiliation: Experimental Clinical Chemistry, Wallenberg Laboratory, Department of Laboratory Medicine, Lund University, Skåne University Hospital, 20502 Malmö, Sweden.
authors.forename: Julhash U
authors.initials: JU
authors.lastname: Kazi
authors.forename: Lars
authors.initials: L
authors.lastname: Rönnstrand
mesh_terms: D000818:Animals; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D051383:GRB10 Adaptor Protein / Q000235:genetics / Q000378:metabolism*; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D011379:Prognosis; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D015854:Up-Regulation; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics / Q000378:metabolism*
chemical_list: D050799:STAT5 Transcription Factor; D051383:GRB10 Adaptor Protein; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3; D051057:Proto-Oncogene Proteins c-akt