title: IGF-1 suppresses Bim expression in multiple myeloma via epigenetic and posttranslational mechanisms.
abstract: Insulin-like growth factor-1 (IGF-1) is an important growth and survival factor in multiple myeloma (MM). Here, we demonstrate that IGF-1 induces significant down-regulation of the proapoptotic BH3-only protein Bim in MM cells. Reduced Bim levels by RNA interference (RNAi) protected cells from drug-induced cell death. The IGF-1-mediated down-regulation of Bim was the result of (1) reduced transcription by activation of the Akt pathway and inactivation of the transcription factor FoxO3a, (2) increased proteasome-mediated degradation of the Bim extra-long protein by activation of the mitogen-activated protein kinase pathway, and (3) epigenetic regulation of both the Bim and the FoxO3a promoter. Treatment of cells with the histone deacetylase inhibitor LBH589 resulted in a clear up-regulation in the expression of Bim. Furthermore, the methylation inhibitor 5-aza-2'deoxycytidine (decitabine) significantly increased the effects of LBH589. On IGF-1 treatment, the Bim promoter region was found to be unmethylated, whereas chromatin immunoprecipitation analysis of the IGF-1-treated cells showed both a reduced histone H3 tail Lys9 (H3K9) acetylation and an increased H3K9 dimethylation, which contributed actively to its silencing. These data identify a new mechanism in the IGF-1-dependent survival of MM cells and emphasize the need for IGF-1-targeted drug therapy.
authors.affiliation: Department of Hematology and Immunology, Vrije Universiteit Brussel, B-1090 Brussels, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: De Bruyne
authors.forename: Tomas J
authors.initials: TJ
authors.lastname: Bos
authors.forename: Frans
authors.initials: F
authors.lastname: Schuit
authors.forename: Els
authors.initials: E
authors.lastname: Van Valckenborgh
authors.forename: Eline
authors.initials: E
authors.lastname: Menu
authors.forename: Lieven
authors.initials: L
authors.lastname: Thorrez
authors.forename: Peter
authors.initials: P
authors.lastname: Atadja
authors.forename: Helena
authors.initials: H
authors.lastname: Jernberg-Wiklund
authors.forename: Karin
authors.initials: K
authors.lastname: Vanderkerken
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D000072224:Bcl-2-Like Protein 11; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D015536:Down-Regulation / Q000502:physiology; D044127:Epigenesis, Genetic / Q000502:physiology*; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D020868:Gene Silencing; D006657:Histones / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007074:Immunoglobulin G / Q000494:pharmacology; D007211:Indoles; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D008558:Melphalan / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009101:Multiple Myeloma / Q000235:genetics* / Q000473:pathology; D000077767:Panobinostat; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins / Q000235:genetics*
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D006657:Histones; D006877:Hydroxamic Acids; D007074:Immunoglobulin G; D007211:Indoles; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; C051713:antineoplastic agent K 18; D007334:Insulin-Like Growth Factor I; D000077767:Panobinostat; D019869:Phosphatidylinositol 3-Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D008558:Melphalan