title: Paired-box gene 2 is down-regulated in endometriosis and correlates with low epidermal growth factor receptor expression.
abstract: BACKGROUND
  Paired-box 2 (Pax2) is involved in the development of the female genital tract and has been associated with endometrial pathologies. The expression of Pax2 is induced by epidermal growth factor (EGF) and estrogens. In the present study, Pax2 expression and regulation were investigated in endometriosis.
  
  
  RESULTS
  Pax2 protein expression was assessed by immunohistochemistry in the eutopic (i.e. inside the uterus) and ectopic tissue (endometriosis) from 11 patients. Immunoreactivity was high in the endometrium, with strong epithelial and weaker stromal staining. Similar expression patterns of Pax2 were observed in the endometrium of women without endometriosis (n = 12). The mRNA level of Pax2 was assessed by real-time PCR in the eutopic and ectopic endometria of 14 patients and in the endometrium from women without endometriosis (n = 20). Pax2 expression was lower in endometriotic lesions than that in the eutopic endometrium of patients (P< 0.001) and controls (P= 0.007). Three possible mechanisms determining low Pax2 expression were investigated: EGF signalling, CpG DNA methylation of the Pax2 promoter and steroid response. The mRNA level of the EGF receptor (EGFR1) was assessed in the samples used for Pax2 mRNA assessment. A significant correlation between EGFR1 and Pax2 in both eutopic and ectopic tissues was observed (R = 0.58; slope regression line, 0.81; 95% CI: 0.09-1.52 and R = 0.54; slope regression line, 2.51; 95% CI: 0.02-4.99, respectively). CpG DNA methylation was analyzed by methyl-specific PCR in two regions of the Pax2 promoter but they were unmethylated in all samples. Steroid responsiveness was assessed using endometrial explant cultures and Pax2 was not regulated by either 17β-estradiol or progesterone.
  
  
  CONCLUSIONS
  In endometriosis patients, Pax2 is down-regulated in the lesions compared with the eutopic tissue, possibly due to low EGF signalling.
authors.affiliation: School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: A A
authors.initials: AA
authors.lastname: de Graaff
authors.forename: B
authors.initials: B
authors.lastname: Delvoux
authors.forename: K K
authors.initials: KK
authors.lastname: Van de Vijver
authors.forename: C M
authors.initials: CM
authors.lastname: Kyama
authors.forename: T M
authors.initials: TM
authors.lastname: D'Hooghe
authors.forename: G A J
authors.initials: GA
authors.lastname: Dunselman
authors.forename: A
authors.initials: A
authors.lastname: Romano
mesh_terms: D000328:Adult; D019175:DNA Methylation / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics*; D004715:Endometriosis / Q000235:genetics*; D004717:Endometrium / Q000737:chemistry; D004815:Epidermal Growth Factor / Q000502:physiology; D066246:ErbB Receptors / Q000235:genetics* / Q000502:physiology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D051762:PAX2 Transcription Factor / Q000032:analysis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000502:physiology
chemical_list: D051762:PAX2 Transcription Factor; C497318:PAX2 protein, human; D012333:RNA, Messenger; D004815:Epidermal Growth Factor; D066246:ErbB Receptors