title: DNA hypomethylation of the COX-2 gene promoter is associated with up-regulation of its mRNA expression in eutopic endometrium of endometriosis.
abstract: BACKGROUND
  Accumulated evidence reveals that cyclooxygenase-2 (COX-2) was overexpressed in eutopic endometrium of endometriosis, which may play a critical role in the pathogenesis of endometriosis. However, few studies have been performed to explore the molecular mechanisms underlying the abnormal high expression of COX-2 in endometriosis. Considering the fact that a number of recent studies have shown DNA methylation affecting some genes in endometriosis, the present study was therefore aimed to determine whether the observed high expression COX-2 in endometriosis is caused by the hypomethylation of CpG island within the promoter of this gene.
  
  
  METHODS
  The endometrial tissues were collected from 60 women with endometriosis (endometriosis group) and 20 women without endometriosis (control group). The methylation status of COX-2 was examined by methylation specific PCR. Quantitative real-time RT-PCR was performed to measure COX-2 mRNA level in endometrial tissues.
  
  
  RESULTS
  The frequency of promoter hypermethylation of COX-2 was lower in eutopic endometrium of the endometriosis group (41.7%) than that in the control group (75.0%), P < 0.05. COX-2 mRNA level in the eutopic endometrium of the endometriosis group was 2.61-fold higher than that in the control group (P < 0.01). COX-2 mRNA level in unmethylated endometrium of the endometriosis group or the control group was 2.39-fold and 2.66-fold, respectively, higher than that in the methylated endometrium of the same group (P < 0.01).
  
  
  CONCLUSIONS
  The hypomethylation within the promoter of COX-2 may be responsible for the elevated gene expression in eutopic endometrium of endometriosis.
authors.affiliation: Department of Obstetrics & Gynecology, Shengjing Hospital Affiliated to China Medical University, Shenyang, People's Republic of China. wangdb@sj-hospital.org
authors.forename: DanBo
authors.initials: D
authors.lastname: Wang
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.forename: Chiyuan
authors.initials: C
authors.lastname: Zhang
authors.forename: Fang
authors.initials: F
authors.lastname: Ren
authors.forename: Tong
authors.initials: T
authors.lastname: Li
mesh_terms: D000328:Adult; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics / Q000378:metabolism; D016022:Case-Control Studies; D018899:CpG Islands; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D004715:Endometriosis / Q000235:genetics* / Q000473:pathology; D004717:Endometrium / Q000378:metabolism / Q000473:pathology*; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D008875:Middle Aged; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: C497252:CEBPD protein, human; D012333:RNA, Messenger; D051743:CCAAT-Enhancer-Binding Protein-delta; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human