A sequential treatment of depsipeptide followed by 5-azacytidine enhances Gadd45beta expression in hepatocellular carcinoma cells.
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.
Jiang
Chunling
C
Department of Clinical and Molecular Pharmacology, City of Hope National Medical Center, Duarte, California 91010, USA.
Zhou
Bingsen
B
Fan
Kenneth
K
Heung
Eric
E
Xue
Lijun
L
Liu
Xiyong
X
Kirschbaum
Mark
M
Yen
Yun
Y
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
D000943:Antigens, Differentiation; D001374:Azacitidine; D047630:Depsipeptides; D056572:Histone Deacetylase Inhibitors; C086470:GADD45B protein, human; D000097642:GADD45 Proteins