title: Prostacyclin synthase expression and epigenetic regulation in nonsmall cell lung cancer.
abstract: BACKGROUND
  Prostacyclin synthase (PGIS) metabolizes prostaglandin H(2), into prostacyclin. This study aimed to determine the expression profile of PGIS in nonsmall cell lung cancer (NSCLC) and examine potential mechanisms involved in PGIS regulation.
  
  
  METHODS
  PGIS expression was examined in human NSCLC and matched controls by reverse transcriptase polymerase chain reaction (RT-PCR), Western analysis, and immunohistochemistry. A 204-patient NSCLC tissue microarray was stained for PGIS and cyclooxygenase 2 (COX2) expression. Staining intensity was correlated with clinical parameters. Epigenetic mechanisms underpinning PGIS promoter expression were examined using RT-PCR, methylation-specific PCR, and chromatin immunoprecipitation analysis.
  
  
  RESULTS
  PGIS expression was reduced/absent in human NSCLC protein samples (P < .0001), but not mRNA relative to matched controls. PGIS tissue expression was higher in squamous cell carcinoma (P = .004) and in male patients (P < .05). No significant correlation of PGIS or COX2 expression with overall patient survival was observed, although COX2 was prognostic for short-term (2-year) survival (P < .001). PGIS mRNA expression was regulated by DNA CpG methylation and histone acetylation in NSCLC cell lines, with chromatin remodeling taking place directly at the PGIS gene. PGIS mRNA expression was increased by both demethylation agents and histone deacetylase inhibitors. Protein levels were unaffected by demethylation agents, whereas PGIS protein stability was negatively affected by histone deacetylase inhibitors.
  
  
  CONCLUSIONS
  PGIS protein expression is reduced in NSCLC, and does not correlate with overall patient survival. PGIS expression is regulated through epigenetic mechanisms. Differences in expression patterns between mRNA and protein levels suggest that PGIS expression and protein stability are regulated post-translationally. PGIS protein stability may have an important therapeutic role in NSCLC.
authors.affiliation: Department of Clinical Medicine, Translational Cancer Research Group, Institute of Molecular Medicine, Trinity Centre for Health Sciences, St. James' Hospital, Dublin, Ireland.
authors.forename: Mary-Clare
authors.initials: MC
authors.lastname: Cathcart
authors.forename: Steven G
authors.initials: SG
authors.lastname: Gray
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Baird
authors.forename: Elaine
authors.initials: E
authors.lastname: Boyle
authors.forename: Kathy
authors.initials: K
authors.lastname: Gately
authors.forename: Elaine
authors.initials: E
authors.lastname: Kay
authors.forename: Robert
authors.initials: R
authors.lastname: Cummins
authors.forename: Graham P
authors.initials: GP
authors.lastname: Pidgeon
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: O'Byrne
mesh_terms: D000230:Adenocarcinoma / Q000201:enzymology / Q000235:genetics; D000328:Adult; D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology* / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000201:enzymology / Q000235:genetics; D051546:Cyclooxygenase 2 / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D044127:Epigenesis, Genetic; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000378:metabolism*; D008175:Lung Neoplasms / Q000201:enzymology* / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D011379:Prognosis
chemical_list: D003577:Cytochrome P-450 Enzyme System; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase