title: Hypoxia differentially regulated CXCR4 and CXCR7 signaling in colon cancer.
abstract: BACKGROUND
  HIF-1α and CXCR4/CXCL12 have crucial roles in the metastatic process of colorectal cancer. Our aim was to study the significance of targeting HIF-1α and the CXCR4/CXCL12 axis in colorectal cancer to prevent the dissemination process in vitro.
  
  
  METHODS
  We investigated CXCR4 and CXCR7 mRNA and protein expression in human colon carcinomas and the modulation of their expression by hypoxia and HIF-1α in colon cancer cell lines. The migration of tumor cells in a Boyden chamber was studied after CXCR4 inhibition with siRNA or the CXCR4/CXCL12 neutraligand, chalcone 4.
  
  
  RESULTS
  Analysis of a cohort of colon polyps and chromosome-unstable carcinomas showed that the expression of CXCR4 and CXCR7 was similar to that of the normal mucosa in the polyps and early-stage carcinomas but significantly increased in late stage carcinomas. Our data demonstrate that hypoxia strongly induced the expression of CXCR4 transcript and protein at the cell membrane, both regulated by HIF-1α, whereas CXCR7 expression was independent of hypoxia. After transient hypoxia, CXCR4 levels remained stable at the cell membrane up to 48 hours. Furthermore, reducing CXCR4 expression impaired CXCL12-induced Akt phosphorylation, whereas Erk activation remained unchanged. In contrast, reducing CXCR7 expression did not affect Akt nor Erk activation. In the presence of CXCR4 or CXCR7 siRNAs, a significant reduction in cell migration occurred (37% and 17%, respectively). Although irinotecan inhibited cell migration by 20% (p <0.001), the irinotecan and chalcone 4 combination further increased inhibition to 40% (p <0.001).
  
  
  CONCLUSIONS
  We demonstrated, for the first time, that hypoxia upregulated CXCR4 but not CXCR7 expression in tumor cells and that the CXCR4 receptor protein level remains high at the cell membrane when the tumor cells return to normoxia for up to 48 hours. In addition we showed the interest to inhibit the CXCR4 signaling by inhibiting both the HIF-1α and CXCR4/CXCL12 pathway. CXCR4 seems to be a relevant target because it is continuously expressed and functional both in normoxic and hypoxic conditions in tumor cells.
authors.forename: Benoît
authors.initials: B
authors.lastname: Romain
authors.forename: Muriel
authors.initials: M
authors.lastname: Hachet-Haas
authors.forename: Serge
authors.initials: S
authors.lastname: Rohr
authors.forename: Cécile
authors.initials: C
authors.lastname: Brigand
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Galzi
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Gaub
authors.forename: Erwan
authors.initials: E
authors.lastname: Pencreach
authors.affiliation: Université de Strasbourg (UdS), EA 3430 Progression tumorale et microenvironnement, Approches translationnelles et Epidémiologie, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Bâtiment U1113, 3 Avenue Molière, 67200 Strasbourg, France. dominique.guenot@inserm.fr.
authors.forename: Dominique
authors.initials: D
authors.lastname: Guenot
mesh_terms: D015687:Cell Hypoxia / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D054387:Receptors, CXCR / Q000096:biosynthesis* / Q000235:genetics; D019718:Receptors, CXCR4 / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction
chemical_list: C501896:ACKR3 protein, human; C527276:CXCR4 protein, human; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D054387:Receptors, CXCR; D019718:Receptors, CXCR4; D051057:Proto-Oncogene Proteins c-akt