title: FoxO3a nuclear localization and its association with β-catenin and Smads in IFN-α-treated hepatocellular carcinoma cell lines.
abstract: Interferon-α2b (IFN-α2b) reduces proliferation and increases apoptosis in hepatocellular carcinoma cells by decreasing β-catenin/TCF4/Smads interaction. Forkhead box O-class 3a (FoxO3a) participates in proliferation and apoptosis and interacts with β-catenin and Smads. FoxO3a is inhibited by Akt, IκB kinase β (IKKβ), and extracellular-signal-regulated kinase (Erk), which promote FoxO3a sequestration in the cytosol, and accumulates in the nucleus upon phosphorylation by c-Jun N-terminal kinase (JNK) and p38 mitogen-activated kinase (p38 MAPK). We analyzed FoxO3a subcellular localization, the participating kinases, FoxO3a/β-catenin/Smads association, and FoxO3a target gene expression in IFN-α2b-stimulated HepG2/C3A and Huh7 cells. Total FoxO3a and Akt-phosphorylated FoxO3a levels decreased in the cytosol, whereas total FoxO3a levels increased in the nucleus upon IFN-α2b stimulus. IFN-α2b reduced Akt, IKKβ, and Erk activation, and increased JNK and p38 MAPK activation. p38 MAPK inhibition blocked IFN-α2b-induced FoxO3a nuclear localization. IFN-α2b enhanced FoxO3a association with β-catenin and Smad2/3/7. Two-step coimmunoprecipitation experiments suggest that these proteins coexist in the same complex. The expression of several FoxO3a target genes increased with IFN-α2b. FoxO3a knockdown prevented the induction of these genes, suggesting that FoxO3a acts as mediator of IFN-α2b action. Results suggest a β-catenin/Smads switch from TCF4 to FoxO3a. Such events would contribute to the IFN-α2b-mediated effects on cellular proliferation and apoptosis. These results demonstrate new mechanisms for IFN-α action, showing the importance of its application in antitumorigenic therapies.
authors.affiliation: Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario , Rosario, Argentina .
authors.forename: María Paula
authors.initials: MP
authors.lastname: Ceballos
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Parody
authors.forename: Ariel Darío
authors.initials: AD
authors.lastname: Quiroga
authors.forename: María Laura
authors.initials: ML
authors.lastname: Casella
authors.forename: Daniel Eleazar
authors.initials: DE
authors.lastname: Francés
authors.forename: María Cecilia
authors.initials: MC
authors.lastname: Larocca
authors.forename: Cristina Ester
authors.initials: CE
authors.lastname: Carnovale
authors.forename: María de Luján
authors.initials: Mde L
authors.lastname: Alvarez
authors.forename: María Cristina
authors.initials: MC
authors.lastname: Carrillo
mesh_terms: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000276:immunology / Q000628:therapy*; D002467:Cell Nucleus / Q000378:metabolism*; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D056945:Hep G2 Cells; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D016898:Interferon-alpha / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D051785:Smad Proteins / Q000378:metabolism*; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C495270:CTNNB1 protein, human; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D016898:Interferon-alpha; D034741:RNA, Small Interfering; D051785:Smad Proteins; C532096:TCF4 protein, human; D000073940:Transcription Factor 4; D014157:Transcription Factors; D051176:beta Catenin; D048051:p38 Mitogen-Activated Protein Kinases