title: Histone deacetylase inhibitor, trichostatin A induces ubiquitin-dependent cyclin D1 degradation in MCF-7 breast cancer cells.
abstract: BACKGROUND
  Cyclin D1 is an important regulator of G1-S phase cell cycle transition and has been shown to be important for breast cancer development. GSK3beta phosphorylates cyclin D1 on Thr-286, resulting in enhanced ubiquitylation, nuclear export and degradation of the cyclin in the cytoplasm. Recent findings suggest that the development of small-molecule cyclin D1 ablative agents is of clinical relevance. We have previously shown that the histone deacetylase inhibitor trichostatin A (TSA) induces the rapid ubiquitin-dependent degradation of cyclin D1 in MCF-7 breast cancer cells prior to repression of cyclin D1 gene (CCND1) transcription. TSA treatment also resulted in accumulation of polyubiquitylated GFP-cyclin D1 species and reduced levels of the recombinant protein within the nucleus.
  
  
  RESULTS
  Here we provide further evidence for TSA-induced ubiquitin-dependent degradation of cyclin D1 and demonstrate that GSK3beta-mediated nuclear export facilitates this activity. Our observations suggest that TSA treatment results in enhanced cyclin D1 degradation via the GSK3beta/CRM1-dependent nuclear export/26S proteasomal degradation pathway in MCF-7 cells.
  
  
  CONCLUSIONS
  We have demonstrated that rapid TSA-induced cyclin D1 degradation in MCF-7 cells requires GSK3beta-mediated Thr-286 phosphorylation and the ubiquitin-dependent 26S proteasome pathway. Drug induced cyclin D1 repression contributes to the inhibition of breast cancer cell proliferation and can sensitize cells to CDK and Akt inhibitors. In addition, anti-cyclin D1 therapy may be highly specific for treating human breast cancer. The development of potent and effective cyclin D1 ablative agents is therefore of clinical relevance. Our findings suggest that HDAC inhibitors may have therapeutic potential as small-molecule cyclin D1 ablative agents.
authors.affiliation: Department of Cancer Medicine, Imperial College, Hammersmith Hospital, London, W12 0NN, UK. j.alao@imperial.ac.uk
authors.forename: John P
authors.initials: JP
authors.lastname: Alao
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Stavropoulou
authors.forename: Eric W-F
authors.initials: EW
authors.lastname: Lam
authors.forename: R Charles
authors.initials: RC
authors.lastname: Coombes
authors.forename: David M
authors.initials: DM
authors.lastname: Vigushin
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D019938:Cyclin D1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D028884:Karyopherins / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D034622:RNA Interference; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D000111:Acetylcysteine; D019938:Cyclin D1; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D028884:Karyopherins; D007976:Leupeptins; D046988:Proteasome Endopeptidase Complex; D061988:Proteasome Inhibitors; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D000097606:Exportin 1 Protein; C067713:lactacystin; C012589:trichostatin A; C000605506:GSK3B protein, human; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C038753:leptomycin B