title: Repression of Gadd45alpha by activated FLT3 and GM-CSF receptor mutants contributes to growth, survival and blocked differentiation.
abstract: The tumor suppressor Gadd45alpha was earlier shown to be a repressed target of sustained receptor-mediated ERK1/2 signaling. We have identified Gadd45alpha as a downregulated gene in response to constitutive signaling from two FLT3 mutants (FLT3-ITD and FLT3-TKD) commonly found in AML, and a leukemogenic GM-CSF receptor trans-membrane mutant (GMR-V449E). GADD45A mRNA downregulation is also associated with FLT3-ITD(+) AML. Sustained ERK1/2 signaling contributes significantly to receptor-mediated downregulation of Gadd45alpha mRNA in FDB1 cells expressing activated receptor mutants, and in the FLT3-ITD(+) cell line MV4;11. Knockdown of Gadd45alpha with shRNA led to increased growth and survival of FDB1 cells and enforced expression of Gadd45alpha in FDB1 cells expressing FLT3-ITD or GMR-V449E resulted in reduced growth and viability. Gadd45alpha overexpression in FLT3-ITD(+) AML cell lines also resulted in reduced growth associated with increased apoptosis and G(1)/S cell cycle arrest. Overexpression of Gadd45alpha in FDB1 cells expressing GMR-V449E was sufficient to induce changes associated with myeloid differentiation suggesting Gadd45alpha downregulation contributes to the maintenance of receptor-induced myeloid differentiation block. Thus, we show that ERK1/2-mediated downregulation of Gadd45alpha by sustained receptor signaling contributes to growth, survival and arrested differentiation in AML.
authors.affiliation: Division of Haematology, Institute of Medical and Veterinary Science, Hanson Institute, Adelaide, South Australia, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Perugini
authors.forename: C H
authors.initials: CH
authors.lastname: Kok
authors.forename: A L
authors.initials: AL
authors.lastname: Brown
authors.forename: C R
authors.initials: CR
authors.lastname: Wilkinson
authors.forename: D G
authors.initials: DG
authors.lastname: Salerno
authors.forename: S M
authors.initials: SM
authors.lastname: Young
authors.forename: S M
authors.initials: SM
authors.lastname: Diakiw
authors.forename: I D
authors.initials: ID
authors.lastname: Lewis
authors.forename: T J
authors.initials: TJ
authors.lastname: Gonda
authors.forename: R J
authors.initials: RJ
authors.lastname: D'Andrea
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D015536:Down-Regulation / Q000235:genetics; D015470:Leukemia, Myeloid, Acute / Q000209:etiology / Q000473:pathology*; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3; D009154:Mutation / Q000502:physiology*; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000502:physiology*; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics / Q000502:physiology*; D000097642:GADD45 Proteins
chemical_list: D018797:Cell Cycle Proteins; D048052:Mitogen-Activated Protein Kinase 3; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D051941:fms-Like Tyrosine Kinase 3; C499072:Gadd45a protein, mouse; D000097642:GADD45 Proteins; C497970:FLT3 protein, human