title: E-cadherin gene re-expression in chronic lymphocytic leukemia cells by HDAC inhibitors.
abstract: BACKGROUND
  The tumor suppressor gene E-cadherin gene is frequently silenced in chronic lymphocytic leukemia (CLL) cells and results in wnt-pathway activation. We analyzed the role of histone epigenetic modifications in E-cadherin gene silencing.
  
  
  METHODS
  CLL specimens were treated with histone deacetylase inhibitor (HDACi) MS-275 and analyzed for E-cadherin expression with western blot and RT-PCR analysis. The downstream effects of HDACi treated leukemic cells were studied by analyzing the effect on wnt-pathway signaling. HDACi induced alterations in E-cadherin splicing were investigated by transcript specific real time PCR analysis.
  
  
  RESULTS
  Treatment of CLL specimens with histone deacetylase inhibitors (HDACi) treatment resulted in an increase of the E-cadherin RNA transcript (5 to 119 fold increase, n=10) in eight out of ten CLL specimens indicating that this gene is down regulated by histone hypoacetylation in a majority of CLL specimens. The E-cadherin re-expression in CLL specimens was noted by western blot analysis as well. Besides epigenetic silencing another mechanism of E-cadherin inactivation is aberrant exon 11 splicing resulting in an alternatively spliced transcript that lacks exon 11 and is degraded by the non-sense mediated decay (NMD) pathway. Our chromatin immunoprecipitation experiments show that HDACi increased the acetylation of histones H3 and H4 in the E-cadherin promoter region. This also affected the E-cadherin exon 11 splicing pattern as HDACi treated CLL specimens preferentially expressed the correctly spliced transcript and not the exon 11 skipped aberrant transcript. The re-expressed E- cadherin binds to β-catenin with inhibition of the active wnt-beta-catenin pathway in these cells. This resulted in a down regulation of two wnt target genes, LEF and cyclinD1 and the wnt pathway reporter.
  
  
  CONCLUSIONS
  The E-cadherin gene is epigenetically modified and hypoacetylated in CLL leukemic cells. Treatment of CLL specimens with HDACi MS-275 activates transcription from this silent gene with expression of more correctly spliced E-cadherin transcripts as compared to the aberrant exon11 skipped transcripts that in turn inhibits the wnt signaling pathway. The data highlights the role of epigenetic modifications in altering gene splicing patterns.
authors: Division of Hematology-Oncology, Greater Los Angeles VA Healthcare Center, UCLA School of Medicine, 11301 Wilshire Blvd, LA, CA 90073, USA.
authors: Gwen
authors: G
authors: Jordaan
authors: Wei
authors: W
authors: Liao
authors: Sanjai
authors: S
authors: Sharma
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism; D057890:Epigenomics; D005091:Exons; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D016147:Genes, Tumor Suppressor / Q000187:drug effects*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012326:RNA Splicing / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D060449:Wnt Signaling Pathway / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D015820:Cadherins; D056572:Histone Deacetylase Inhibitors