title: COUP-TFI modifies CXCL12 and CXCR4 expression by activating EGF signaling and stimulates breast cancer cell migration.
abstract: BACKGROUND
  The orphan receptors COUP-TF (chicken ovalbumin upstream promoter transcription factor) I and II are members of the nuclear receptor superfamily that play distinct and critical roles in vertebrate organogenesis. The involvement of COUP-TFs in cancer development has recently been suggested by several studies but remains poorly understood.
  
  
  METHODS
  MCF-7 breast cancer cells overexpressing COUP-TFI and human breast tumors were used to investigate the role of COUP-TFI in the regulation of CXCL12/CXCR4 signaling axis in relation to cell growth and migration. We used Immunofluorescence, western-blot, RT-PCR, Formaldehyde-assisted Isolation of Regulatory Elements (FAIRE) assays, as well as cell proliferation and migration assays.
  
  
  RESULTS
  Previously, we showed that COUP-TFI expression is enhanced in breast cancer compared to normal tissue. Here, we report that the CXCL12/CXCR4 signaling pathway, a crucial pathway in cell growth and migration, is an endogenous target of COUP-TFI in breast cancer cells. The overexpression of COUP-TFI in MCF-7 cells inhibits the expression of the chemokine CXCL12 and markedly enhances the expression of its receptor, CXCR4. Our results demonstrate that the modification of CXCL12/CXCR4 expression by COUP-TFI is mediated by the activation of epithelial growth factor (EGF) and the EGF receptor. Furthermore, we provide evidence that these effects of COUP-TFI increase the growth and motility of MCF-7 cells in response to CXCL12. Cell migration toward a CXCL12 gradient was inhibited by AMD3100, a specific antagonist of CXCR4, or in the presence of excess CXCL12 in the cell culture medium. The expression profiles of CXCR4, CXCR7, CXCL12, and COUP-TFI mRNA in 82 breast tumors and control non-tumor samples were measured using real-time PCR. CXCR4 expression was found to be significantly increased in the tumors and correlated with the tumor grade, whereas the expression of CXCL12 was significantly decreased in the tumors compared with the healthy samples. Significantly higher COUP-TFI mRNA expression was also detected in grade 1 tumors.
  
  
  CONCLUSIONS
  Together, our mechanistic in vitro assays and in vivo results suggest that a reduction in chemokine CXCL12 expression, with an enhancement of CXCR4 expression, provoked by COUP-TFI, could be associated with an increase in the invasive potential of breast cancer cells.
authors.forename: Antoine
authors.initials: A
authors.lastname: Boudot
authors.forename: Gwenneg
authors.initials: G
authors.lastname: Kerdivel
authors.forename: Sylvain
authors.initials: S
authors.lastname: Lecomte
authors.forename: Gilles
authors.initials: G
authors.lastname: Flouriot
authors.forename: Mireille
authors.initials: M
authors.lastname: Desille
authors.forename: Florence
authors.initials: F
authors.lastname: Godey
authors.forename: Jean
authors.initials: J
authors.lastname: Leveque
authors.forename: Patrick
authors.initials: P
authors.lastname: Tas
authors.forename: Yves
authors.initials: Y
authors.lastname: Le Dréan
authors.affiliation: Institut de Recherche en Santé-Environnement-Travail (IRSET), INSERM U1085, Université de Rennes 1, Equipe TREC, Biosit, Rennes, France. farzad.pakdel@univ-rennes1.fr.
authors.forename: Farzad
authors.initials: F
authors.lastname: Pakdel
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D051838:COUP Transcription Factor I / Q000235:genetics / Q000378:metabolism*; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D054377:Chemokine CXCL12 / Q000096:biosynthesis*; D004815:Epidermal Growth Factor / Q000096:biosynthesis / Q000378:metabolism*; D066246:ErbB Receptors / Q000096:biosynthesis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D011401:Promoter Regions, Genetic; D019718:Receptors, CXCR4 / Q000096:biosynthesis*; D015398:Signal Transduction
chemical_list: D051838:COUP Transcription Factor I; C515255:CXCL12 protein, human; C527276:CXCR4 protein, human; D054377:Chemokine CXCL12; C497589:NR2F1 protein, human; D019718:Receptors, CXCR4; D004815:Epidermal Growth Factor; D066246:ErbB Receptors