title: FLT3-ITD up-regulates MCL-1 to promote survival of stem cells in acute myeloid leukemia via FLT3-ITD-specific STAT5 activation.
abstract: Myeloid cell leukemia-1 (MCL-1) is an essential survival factor for hematopoiesis. In humans, hematopoietic stem cells (HSCs) express MCL-1 at the highest level in response to FMS-like tyrosine kinase-3 (FLT3) signaling. We here show that this FLT3-dependent stem cell maintenance system also plays a critical role in survival of leukemic stem cells (LSCs) in acute myeloid leukemia (AML). The CD34(+)CD38(-) LSC fraction expresses high levels of FLT3 as well as MCL-1, even compared with normal HSCs. Treatment with FLT3 ligand induced further MCL-1 up-regulation in LSCs in all AML cases tested. Interestingly, the group of samples expressing the highest levels of MCL-1 constituted AML with FLT3-internal tandem duplications (ITD). In FLT3-ITD AML cell lines, cells expressed a high level of MCL-1, and an inhibition of MCL-1 induced their apoptotic cell death. A tyrosine kinase inhibitor suppressed MCL-1 expression, and induced apoptosis that was reversed by the enforced MCL-1 expression. Finally, transduction of FLT3-ITD into HSCs strongly activated MCL-1 expression through its signal transducer and activator of transcription 5 (STAT5)-docking domains. This effect was completely abrogated when STAT5 activation was blocked. Thus, the acquisition of FLT3-ITD ensures LSC survival by up-regulating MCL-1 via constitutive STAT5 activation that is independent of wild-type FLT3 signaling.
authors.affiliation: Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
authors.forename: Goichi
authors.initials: G
authors.lastname: Yoshimoto
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Miyamoto
authors.forename: Siamak
authors.initials: S
authors.lastname: Jabbarzadeh-Tabrizi
authors.forename: Tadafumi
authors.initials: T
authors.lastname: Iino
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Rocnik
authors.forename: Yoshikane
authors.initials: Y
authors.lastname: Kikushige
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mori
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shima
authors.forename: Hiromi
authors.initials: H
authors.lastname: Iwasaki
authors.forename: Katsuto
authors.initials: K
authors.lastname: Takenaka
authors.forename: Koji
authors.initials: K
authors.lastname: Nagafuji
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Mizuno
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Niiro
authors.forename: Gary D
authors.initials: GD
authors.lastname: Gilliland
authors.forename: Koichi
authors.initials: K
authors.lastname: Akashi
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002470:Cell Survival; D004789:Enzyme Activation / Q000502:physiology; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D020080:Tandem Repeat Sequences; D015854:Up-Regulation; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics* / Q000378:metabolism
chemical_list: D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D050799:STAT5 Transcription Factor; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3