title: Histone deacetylase inhibitors down-regulate bcl-2 expression and induce apoptosis in t(14;18) lymphomas.
abstract: Histone deacetylase (HDAC) inhibitors are promising antitumor agents, but they have not been extensively explored in B-cell lymphomas. Many of these lymphomas have the t(14;18) translocation, which results in increased bcl-2 expression and resistance to apoptosis. In this study, we examined the effects of two structurally different HDAC inhibitors, trichostatin A (TSA) and sodium butyrate (NaB), on the cell cycle, apoptosis, and bcl-2 expression in t(14;18) lymphoma cells. We found that in addition to potent cell cycle arrest, TSA and NaB also dramatically induced apoptosis and down-regulated bcl-2 expression, and overexpression of bcl-2 inhibited TSA-induced apoptosis. The repression of bcl-2 by TSA occurred at the transcriptional level. Western blot analysis and quantitative chromatin immunoprecipitation (ChIP) assay showed that even though HDAC inhibitors increased overall acetylation of histones, localized histone H3 deacetylation occurred at both bcl-2 promoters. TSA treatment increased the acetylation of the transcription factors Sp1 and C/EBPalpha and decreased their binding as well as the binding of CBP and HDAC2 to the bcl-2 promoters. Mutation of Sp1 and C/EBPalpha binding sites reduced the TSA-induced repression of bcl-2 promoter activity. This study provides a mechanistic rationale for the use of HDAC inhibitors in the treatment of human t(14;18) lymphomas.
authors.affiliation: Center for Molecular Biology in Medicine, Veterans Affairs, Palo Alto Health Care System, Palo Alto, CA, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Duan
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Heckman
authors.forename: Linda M
authors.initials: LM
authors.lastname: Boxer
mesh_terms: D000107:Acetylation / Q000187:drug effects; D017209:Apoptosis; D001463:Barbiturates / Q000494:pharmacology; D001665:Binding Sites / Q000235:genetics; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002883:Chromosomes, Human, Pair 14; D002887:Chromosomes, Human, Pair 18; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D056464:Histone Deacetylase 2; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism / Q000502:physiology; D006657:Histones / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D016393:Lymphoma, B-Cell / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011494:Protein Kinases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012097:Repressor Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D014178:Translocation, Genetic
chemical_list: D001463:Barbiturates; D022762:CCAAT-Enhancer-Binding Proteins; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012097:Repressor Proteins; C012589:trichostatin A; D011494:Protein Kinases; C065999:Sp1 kinase; D056464:Histone Deacetylase 2; D006655:Histone Deacetylases; C032232:barbituric acid