Elevated NCOR1 disrupts PPARalpha/gamma signaling in prostate cancer and forms a targetable epigenetic lesion

Sebastiano Battaglia, Orla Maguire, James L Thorne, Laura B Hornung, Craig L Doig, Song Liu, Lara E Sucheston, Anna Bianchi, Farhat L Khanim, Lyndon M Gommersall, Henry S O Coulter, Serena Rakha, Ian Giddings, Laura P O'Neill, Colin S Cooper, Christopher J McCabe, Christopher M Bunce, Moray J Campbell

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)

Abstract

The loss of anti-proliferative responsiveness in prostate cancer cell lines toward ligands for vitamin D receptor, retinoic acid receptors/retinoid X receptors and peroxisome proliferator activated receptor (PPAR)alpha/gamma may entail underlying epigenetic events, as ligand insensitivity reflects significantly altered messenger RNA expression of corepressors and histone-modifying enzymes. Expression patterns were dependent on phases of the cell cycle and associated with repressed basal gene expression of vitamin D receptor and PPARalpha/gamma target genes, for example CDKN1A [encodes p21((waf1/cip1))]. Elevated nuclear corepressor 1 (NCOR1) and nuclear corepressor 2/silencing mediator of retinoic acid and thyroid hormone receptor protein levels were detected in prostate cancer cell lines compared with non-malignant counterparts. Knockdown of the corepressor NCOR1 significantly elevated basal expression of a cohort of target genes, including CDKN1A. Both chemical [histone deacetylases inhibitor (HDACi)] and NCOR1 knockdown targeting enhanced anti-proliferative sensitivity toward PPARalpha/gamma ligands in prostate cancer cell lines. Pursuing PPARalpha/gamma signaling, microarray approaches were undertaken to identify pathways and genes regulated uniquely by a combination of PPARalpha/gamma activation and HDAC inhibition. Again, HDACi and knockdown approaches demonstrated that elevated NCOR1 expression and activity distorted PPARalpha/gamma gene targets centered on, for example cell cycle control, including CDKN1A and TGFBRAP1. Quantitative real time polymerase chain reaction validation and chromatin immunoprecipitation assays both confirmed that elevated NCOR1 disrupted the ability of PPARalpha/gamma to regulate key target genes (CDKN1A and TGFBRAP1). Interrogation of these relationships in prostate cancer samples using principal component and partial correlation analyses established significant interdependent relationships between NCOR1-PPARalpha/gamma and representative target genes, independently of androgen receptor expression. Therefore, we conclude that elevated NCOR1 distorts the actions of PPARalpha/gamma selectively and generates a potential epigenetic lesion with diagnostic and prognostic significance.
Original languageEnglish
Pages (from-to)1650-60
Number of pages11
JournalCarcinogenesis
Volume31
Issue number9
DOIs
Publication statusPublished - Sep 2010

Keywords

  • Apoptosis
  • Blotting, Western
  • Cell Cycle
  • Cell Proliferation
  • Chromatin Immunoprecipitation
  • Cyclin-Dependent Kinase Inhibitor p21
  • Epigenesis, Genetic
  • Gene Expression Profiling
  • Histone Deacetylase Inhibitors
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Male
  • Nuclear Receptor Co-Repressor 1
  • Oligonucleotide Array Sequence Analysis
  • PPAR alpha
  • PPAR gamma
  • Prostate
  • Prostatic Neoplasms
  • RNA, Messenger
  • Receptors, Calcitriol
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction
  • Tumor Markers, Biological

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