title: FOXO3/FKHRL1 is activated by 5-aza-2-deoxycytidine and induces silenced caspase-8 in neuroblastoma.
abstract: Forkhead box O (FOXO) transcription factors control diverse cellular functions, such as cell death, metabolism, and longevity. We analyzed FOXO3/FKHRL1 expression and subcellular localization in tumor sections of neuroblastoma patients and observed a correlation between nuclear FOXO3 and high caspase-8 expression. In neuroblastoma caspase-8 is frequently silenced by DNA methylation. Conditional FOXO3 activated caspase-8 gene expression but did not change the DNA-methylation pattern of regulatory sequences in the caspase-8 gene. Instead, FOXO3 induced phosphorylation of its binding partner ATM and of the ATM downstream target cAMP-responsive element binding protein (CREB), which was critical for FOXO3-mediated caspase-8 expression. Caspase-8 levels above a critical threshold sensitized neuroblastoma cells to tumor necrosis factor-related apoptosis-inducing ligand-induced cell death. The DNA-demethylating drug 5-Aza-2-deoxycytidine (5-azadC) induced rapid nuclear accumulation of FOXO3, ATM-dependent CREB phosphorylation, and caspase-8 expression in a FOXO3-dependent manner. This indicates that 5-azadC activates the FOXO3-ATM-CREB signaling pathway, which contributes to caspase-8 expression. The combined data suggest that FOXO3 is activated by 5-azadC treatment and triggers expression of caspase-8 in caspase-8-negative neuroblastoma, which may have important implication for metastasis, therapy, and death resistance of this childhood malignancy.
authors.affiliation: Tyrolean Cancer Research Institute, 6020 Innsbruck, Austria.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Geiger
authors.forename: Judith
authors.initials: J
authors.lastname: Hagenbuchner
authors.forename: Martina
authors.initials: M
authors.lastname: Rupp
authors.forename: Heidi
authors.initials: H
authors.lastname: Fiegl
authors.forename: Consolato
authors.initials: C
authors.lastname: Sergi
authors.forename: Bernhard
authors.initials: B
authors.lastname: Meister
authors.forename: Ursula
authors.initials: U
authors.lastname: Kiechl-Kohlendorfer
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ausserlechner
authors.forename: Petra
authors.initials: P
authors.lastname: Obexer
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001483:Base Sequence; D053181:Caspase 8 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D000077209:Decitabine; D004354:Drug Screening Assays, Antitumor; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects*; D057809:HEK293 Cells; D006801:Humans; D009447:Neuroblastoma / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D053221:TNF-Related Apoptosis-Inducing Ligand; D025521:Tumor Suppressor Proteins; D000077209:Decitabine; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D053181:Caspase 8; D001374:Azacitidine