title: CXCR7 is induced by hypoxia and mediates glioma cell migration towards SDF-1α.
abstract: BACKGROUND
  Glioblastomas, the most common and malignant brain tumors of the central nervous system, exhibit high invasive capacity, which hinders effective therapy. Therefore, intense efforts aimed at improved therapeutics are ongoing to delineate the molecular mechanisms governing glioma cell migration and invasion.
  
  
  METHODS
  In order to perform the studies, we employed optimal cell culture methods and hypoxic conditions, lentivirus-mediated knockdown of protein expression, Western Blot analysis, migration assays and immunoprecipitation. We determined statistical significance by unpaired t-test.
  
  
  RESULTS
  In this report, we show that U87MG, LN229 and LN308 glioma cells express CXCR7 and that exposure to hypoxia upregulates CXCR7 protein expression in these cell lines. CXCR7-expressing U87MG, LN229 and LN308 glioma cells migrated towards stromal-derived factor (SDF)-1α/CXCL12 in hypoxic conditions in the Boyden chamber assays. While shRNA-mediated knockdown of CXCR7 expression did not affect the migration of any of the three cell lines in normoxic conditions, we observed a reduction in the migration of LN229 and LN308, but not U87MG, glioma cells towards SDF-1α in hypoxic conditions. In addition, knockdown of CXCR7 expression in LN229 and LN308 glioma cells decreased levels of SDF-1α-induced phosphorylation of ERK1/2 and Akt. Inhibiting CXCR4 in LN229 and LN308 glioma cells that were knocked down for CXCR7 did not further reduce migration towards SDF-1α in hypoxic conditions and did not affect the levels of phosphorylated ERK1/2 and Akt. Analysis of immunoprecipitated CXCR4 from LN229 and LN308 glioma cells revealed co-precipitated CXCR7.
  
  
  CONCLUSIONS
  Taken together, our findings indicate that both CXCR4 and CXCR7 mediate glioma cell migration towards SDF-1α in hypoxic conditions and support the development of therapeutic agents targeting these receptors.
authors.affiliation: Microvascular and Molecular Neuro-oncology Laboratory, New York University Langone Medical Center, New York, NY, USA.
authors.forename: Mine
authors.initials: M
authors.lastname: Esencay
authors.forename: Yasmeen
authors.initials: Y
authors.lastname: Sarfraz
authors.forename: David
authors.initials: D
authors.lastname: Zagzag
mesh_terms: D015153:Blotting, Western; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D054377:Chemokine CXCL12 / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D047468:Immunoprecipitation; D009361:Neoplasm Invasiveness / Q000473:pathology; D054387:Receptors, CXCR / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000378:metabolism*
chemical_list: C501896:ACKR3 protein, human; C515255:CXCL12 protein, human; C527276:CXCR4 protein, human; D054377:Chemokine CXCL12; D054387:Receptors, CXCR; D019718:Receptors, CXCR4