title: A sequential treatment of depsipeptide followed by 5-azacytidine enhances Gadd45beta expression in hepatocellular carcinoma cells.
abstract: BACKGROUND
  DNA methylation can influence histone modification and gene expression. The growth-arrest DNA damage inducible gene 45beta (Gadd45beta) has been reported as a potential diagnostic marker for aggressive hepatocellular carcinoma. In this study, the synergistic effect of the histone deacetylase inhibitor depsipeptide and the DNA methyltransferase inhibitor 5-azacytidine on the Gadd45beta gene expression in human liver cells was examined.
  
  
  METHODS
  The effects of depsipeptide and 5-azacytidine in CL-48, HepG2 and Hep3B cells were examined by PCR, cell viability test, Western blot and chromatin immunoprecipitation assay.
  
  
  RESULTS
  Two microM depsipeptide reactivated Gadd45beta gene expression considerably within 4 h in HepG2 cells, but not in CL-48 or Hep3B cells. Up to 10 microM 5-azacytidine had no reactivation effect on Gadd45beta. A sequential treatment of depsipeptide+5-azacytidine (but not 5-azacytidine+depsipeptide) exhibited a synergistic effect on Gadd45beta gene reactivation in the HepG2 cells.
  
  
  CONCLUSIONS
  The results show for the first time that histone acetylation in sequence with hypermethylation can override transcriptional repression. Our results provide a novel insight into the epigenetics-based strategy for treating human liver cancer.
authors.affiliation: Department of Clinical and Molecular Pharmacology, City of Hope National Medical Center, Duarte, California 91010, USA.
authors.forename: Chunling
authors.initials: C
authors.lastname: Jiang
authors.forename: Bingsen
authors.initials: B
authors.lastname: Zhou
authors.forename: Kenneth
authors.initials: K
authors.lastname: Fan
authors.forename: Eric
authors.initials: E
authors.lastname: Heung
authors.forename: Lijun
authors.initials: L
authors.lastname: Xue
authors.forename: Xiyong
authors.initials: X
authors.lastname: Liu
authors.forename: Mark
authors.initials: M
authors.lastname: Kirschbaum
authors.forename: Yun
authors.initials: Y
authors.lastname: Yen
mesh_terms: D000943:Antigens, Differentiation / Q000096:biosynthesis* / Q000235:genetics; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001374:Azacitidine / Q000008:administration & dosage; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D047630:Depsipeptides / Q000008:administration & dosage; D004334:Drug Administration Schedule; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D014158:Transcription, Genetic / Q000187:drug effects; D000097642:GADD45 Proteins
chemical_list: D000943:Antigens, Differentiation; D001374:Azacitidine; D047630:Depsipeptides; D056572:Histone Deacetylase Inhibitors; C086470:GADD45B protein, human; D000097642:GADD45 Proteins