Histone deacetylase inhibitor LBH589 reactivates silenced estrogen receptor alpha (ER) gene expression without loss of DNA hypermethylation

Cancer Biol Ther. 2007 Jan;6(1):64-9. doi: 10.4161/cbt.6.1.3549.


Our previous studies demonstrated that inhibition of histone deacetylases (HDACs) by trichostatin A reactivates estrogen receptor alpha (ER) gene expression in ER-negative breast cancer cells. Here, we use the clinically relevant HDAC inhibitor, LBH589 (LBH) to explore the roles of HDAC in ER gene silencing. In the ER-negative human breast cancer lines, MDA-MB-231 and MDA-MB-435, treatment with LBH for 24 hours restored ER mRNA and protein expression without a concomitant demethylation of the CpG island at the ER promoter. The expression of ER mRNA was sustained at least 96 hours after withdrawal of LBH treatment. Restoration of ER expression by LBH enhanced 4-hydroxy-tamoxifen sensitivity in MDA-MB-231 cells. The molecular mechanisms by which LBH reactivated silenced ER gene in MDA-MB-231 cells were examined with emphasis on chromatin structure reorganization. By chromatin immunoprecipitation analysis, LBH treatment released DNMT1, HDAC1, and the H3 lysine 9 (H3-K9) methyltransferase SUV39H 1 from the ER promoter. Such changes were associated with an active chromatin formation manifested as accumulation of acetylated histones H3 and H4, a decrease in methylated H3-K9, and an impaired binding of heterochromatin protein 1 (HP1 alpha) at the promoter. Our findings suggest that HDAC inhibitors could restore expression of the silenced ER gene by reorganizing the heterochromatin-associated proteins without alteration in promoter DNA hypermethylation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / enzymology*
  • Breast Neoplasms / genetics
  • Cell Line, Tumor
  • Chromatin Immunoprecipitation
  • DNA (Cytosine-5-)-Methyltransferase 1
  • DNA (Cytosine-5-)-Methyltransferases / drug effects
  • DNA (Cytosine-5-)-Methyltransferases / metabolism
  • DNA Methylation
  • Estrogen Receptor alpha / genetics*
  • Estrogen Receptor alpha / metabolism
  • Gene Expression / drug effects
  • Gene Silencing / drug effects*
  • Heterochromatin / drug effects
  • Heterochromatin / metabolism
  • Histone Deacetylase 1
  • Histone Deacetylase Inhibitors*
  • Histone Deacetylases / drug effects
  • Histone Deacetylases / metabolism
  • Humans
  • Hydroxamic Acids / pharmacology
  • Indoles
  • Methyltransferases / drug effects
  • Methyltransferases / metabolism
  • Panobinostat
  • Promoter Regions, Genetic / drug effects
  • RNA, Messenger / analysis
  • Repressor Proteins / drug effects
  • Repressor Proteins / metabolism


  • Estrogen Receptor alpha
  • Heterochromatin
  • Histone Deacetylase Inhibitors
  • Hydroxamic Acids
  • Indoles
  • RNA, Messenger
  • Repressor Proteins
  • Panobinostat
  • SUV39H1 protein, human
  • Methyltransferases
  • DNA (Cytosine-5-)-Methyltransferase 1
  • DNA (Cytosine-5-)-Methyltransferases
  • DNMT1 protein, human
  • HDAC1 protein, human
  • Histone Deacetylase 1
  • Histone Deacetylases