title: Inhibition of DNA methyltransferase activity and expression by treatment with the pan-deacetylase inhibitor panobinostat in hepatocellular carcinoma cell lines.
abstract: BACKGROUND
  Hepatocellular carcinoma (HCC) still represents an unmet medical need. Epigenetic inactivation of tumor suppressor genes like RASSF1A or APC by overexpression of DNA methyltransferases (DNMTs) has been shown to be common in HCC and to be linked to the overall prognosis of patients. Inhibitors of protein and histone deacetylases (DACi) have been demonstrated to possess strong anti-tumor effects in HCC models.
  
  
  METHODS
  We therefore investigated whether DACi also has any influence on the expression and activity of DNMTs and methylated target genes in HepG2 and Hep3B cell culture systems and in a xenograft model by immunohistochemistry, westernblotting, RT-qPCR and methylation-specific PCR.
  
  
  RESULTS
  Our findings demonstrate a rapid inhibition of DNMT activity 6 h after treatment with 0.1 μM of the pan-DACi panobinostat. A downregulation of DNMT mRNAs and protein were also observed at later points in time. This loss of DNMT activity and expression was paralleled by a diminished methylation of the target genes RASSF1A and APC and a concomitant re-expression of APC mRNA and protein. Analysis of HepG2 xenograft specimens confirmed these results in vivo.
  
  
  CONCLUSIONS
  We suggest a dual mode of action of DACi on DNA methylation status: a rapid inhibition of enzyme activity due to interference with posttranslational acetylation and a delayed effect on transcriptional control of DNMT genes by HDAC or miRNA mechanisms.
authors.affiliation: Department of Medicine 1, University Hospital Erlangen, Ulmenweg 18, Erlangen, 91054, Germany. steffen.zopf@uk-erlangen.de
authors.forename: Steffen
authors.initials: S
authors.lastname: Zopf
authors.forename: Matthias
authors.initials: M
authors.lastname: Ocker
authors.forename: Daniel
authors.initials: D
authors.lastname: Neureiter
authors.forename: Beate
authors.initials: B
authors.lastname: Alinger
authors.forename: Susanne
authors.initials: S
authors.lastname: Gahr
authors.forename: Markus F
authors.initials: MF
authors.lastname: Neurath
authors.forename: Pietro
authors.initials: P
authors.lastname: Di Fazio
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors* / Q000235:genetics*; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D056945:Hep G2 Cells; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D000077767:Panobinostat; D014183:Transplantation, Heterologous
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D007211:Indoles; D000077767:Panobinostat; D015254:DNA Modification Methylases