title: FoxO transcription factors suppress Myc-driven lymphomagenesis via direct activation of Arf.
abstract: FoxO transcription factors play critical roles in cell cycle control and cellular stress responses, and abrogation of FoxO function promotes focus formation by Myc in vitro. Here we show that stable introduction of a dominant-negative FoxO moiety (dnFoxO) into Emu-myc transgenic hematopoietic stem cells accelerates lymphoma development in recipient mice by attenuating Myc-induced apoptosis. When expressed in Emu-myc; p53(+/-) progenitor cells, dnFoxO alleviates the pressure to inactivate the remaining p53 allele in upcoming lymphomas. Expression of the p53 upstream regulator p19(Arf) is virtually undetectable in most dnFoxO-positive Myc-driven lymphomas. We find that FoxO proteins bind to a distinct site within the Ink4a/Arf locus and activate Arf expression. Moreover, constitutive Myc signaling induces a marked increase in nuclear FoxO levels and stimulates binding of FoxO proteins to the Arf locus. These data demonstrate that FoxO factors mediate Myc-induced Arf expression and provide direct genetic evidence for their tumor-suppressive capacity.
authors.affiliation: Institute of Molecular Biology and Tumor Research, 35033 Marburg, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Bouchard
authors.forename: Soyoung
authors.initials: S
authors.lastname: Lee
authors.forename: Viola
authors.initials: V
authors.lastname: Paulus-Hock
authors.forename: Christoph
authors.initials: C
authors.lastname: Loddenkemper
authors.forename: Martin
authors.initials: M
authors.lastname: Eilers
authors.forename: Clemens A
authors.initials: CA
authors.lastname: Schmitt
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D004622:Embryo, Mammalian; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D016259:Genes, myc / Q000502:physiology*; D016158:Genes, p53 / Q000502:physiology; D008223:Lymphoma / Q000235:genetics* / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic
chemical_list: C417743:Cdkn2a protein, mouse; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C474033:FoxO3 protein, mouse; C525394:FoxO4 protein, mouse; C467200:Foxo1 protein, mouse; C525395:Foxo6 protein, mouse