title: Epigenetic silencing of the LDOC1 tumor suppressor gene in ovarian cancer cells.
abstract: OBJECTIVE
  Due to very unspecific symptoms ovarian cancer often is diagnosed only at a late stage of the disease. Thus, morbidity and mortality of the patients are high. Even the established tumor marker CA12-5 shows only low specificity, rising the need for alternative biomarkers capable of detecting early stages of ovarian cancer. We analyzed the expression of the tumor suppressor candidate gene LDOC1 (leucine zipper downregulated in cancer 1) as a potential early biomarker in ovarian cancer cell lines.
  
  
  METHODS
  A total of seven ovarian cancer cell lines were analyzed by RT-PCR (reverse transcriptase polymerase chain reaction) and real-time PCR for expression of LDOC1. Verification of promoter methylation was performed using methylation-specific primers on bisulfite-modified genomic DNA.
  
  
  RESULTS
  Three out of seven ovarian cancer cell lines showed a complete loss of LDOC1 gene expression. LDOC1 silencing was caused neither by gene deletion nor gene rearrangements, but by methylation and subsequent inactivation of the concerned promoter as proofed by methylation specific primers. Similarly, promoter methylation could be inhibited by adding AdC (5-aza-2'-deoxycytidine), an inhibitor of DNA methyltransferases. As a result, a reactivation of the LDOC1 gene was seen.
  
  
  CONCLUSIONS
  The tumor suppressor gene LDOC1 in ovarian cancer cell lines is downregulated by promoter methylation and thus may serve as an early biomarker. Further investigation will show if detection of methylated LDOC1 in peripheral blood has both adequate sensitivity and specificity for a timely non-invasive detection of ovarian cancer.
authors.affiliation: Division of Infectious Diseases in Gynaecology and Obstetrics, First Department of Obstetrics and Gynaecology, Ludwig-Maximilians-University Munich, Maistrasse 11, 80337, Munich, Germany.
authors.forename: Marie-Luise
authors.initials: ML
authors.lastname: Buchholtz
authors.forename: Ansgar
authors.initials: A
authors.lastname: Brüning
authors.forename: Ioannis
authors.initials: I
authors.lastname: Mylonas
authors.forename: Julia
authors.initials: J
authors.lastname: Jückstock
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001374:Azacitidine / Q000031:analogs & derivatives; D014408:Biomarkers, Tumor / Q000235:genetics; D002460:Cell Line; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D000077209:Decitabine; D004791:Enzyme Inhibitors; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor / Q000187:drug effects; D006801:Humans; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D014408:Biomarkers, Tumor; D017931:DNA Primers; D004791:Enzyme Inhibitors; D000077209:Decitabine; D015254:DNA Modification Methylases; D001374:Azacitidine