title: Roles for c-Myc in self-renewal of hematopoietic stem cells.
abstract: Notch and HOXB4 have been reported to expand hematopoietic stem cells (HSCs) in vitro. However, their critical effector molecules remain undetermined. We found that the expression of c-myc, cyclin D2, cyclin D3, cyclin E, and E2F1 was induced or enhanced during Notch1- or HOXB4-induced self-renewal of murine HSCs. Since c-Myc can act as a primary regulator of G(1)/S transition, we examined whether c-Myc alone can induce self-renewal of HSCs. In culture with stem cell factor, FLT3 ligand, and IL-6, a 4-hydroxytamoxifen-inducible form of c-Myc (Myc/ERT) enabled murine Lin(-)Sca-1(+) HSCs to proliferate with the surface phenotype compatible with HSCs for more than 28 days. c-Myc activated by 4-hydroxytamoxifen augmented telomerase activities and increased the number of CFU-Mix about 2-fold in colony assays. Also, in reconstitution assays, HSCs expanded by c-Myc could reconstitute hematopoiesis for more than 6 months. As for the mechanism of c-myc induction by Notch1, we found that activated forms of Notch1 (NotchIC) and its downstream effector recombination signal-binding protein-J kappa (RBP-VP16) can activate the c-myc promoter through the element between -195 bp and -161 bp by inducing the DNA-binding complex. Together, these results suggest that c-Myc can support self-renewal of HSCs as a downstream mediator of Notch and HOXB4.
authors.affiliation: Department of Hematology and Oncology, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Satoh
authors.forename: Itaru
authors.initials: I
authors.lastname: Matsumura
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tanaka
authors.forename: Sachiko
authors.initials: S
authors.lastname: Ezoe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sugahara
authors.forename: Masao
authors.initials: M
authors.lastname: Mizuki
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Shibayama
authors.forename: Eri
authors.initials: E
authors.lastname: Ishiko
authors.forename: Jun
authors.initials: J
authors.lastname: Ishiko
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakajima
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Kanakura
mesh_terms: D000818:Animals; D002455:Cell Division; D019938:Cyclin D1 / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D018398:Homeodomain Proteins / Q000502:physiology; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface / Q000502:physiology; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D014157:Transcription Factors / Q000502:physiology
chemical_list: C090460:HOXB4 protein, human; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D013629:Tamoxifen; D019938:Cyclin D1; C016601:afimoxifene