title: Roundabout4 suppresses glioma-induced endothelial cell proliferation, migration and tube formation in vitro by inhibiting VEGR2-mediated PI3K/AKT and FAK signaling pathways.
abstract: OBJECTIVE
  Endothelial cell (EC) proliferation, migration, and tube formation are the critical steps for tumor angiogenesis, which is involved in the formation of new tumor blood vessels. Roundabout4 (Robo4), a new member of Robo proteins family, is specifically expressed in endothelial cells. This study aimed to investigate the effects of Robo4 on glioma-induced endothelial cell proliferation, migration and tube formation in vitro.
  
  
  RESULTS
  We found that Robo4 was endogenously expressed in Human Brain Microvascular Endothelial Cells (HBMECs), while Robo4 was significantly down-regulated in endothelial cells cultured in glioma conditioned medium. Robo4 over-expression remarkably suppressed glioma-induced endothelial cell proliferation, migration and tube formation in vitro. In addition, Robo4 influenced the glioma-induced angiogenesis via binding to its ligand Slit2. Further studies demonstrated that the knockdown of Robo4 up-regulated the phosphorylation of VEGFR2, PI3K, AKT and FAK in EC cultured in glioma conditioned medium. VEGFR2 inhibitor SU-1498, AKT inhibitor LY294002 and FAK inhibitor 14 (FAK inhibitor) blocked the Robo4 knockdown-mediated alteration in glioma angiogenesis in vitro.
  
  
  CONCLUSIONS
  Our results proved that Robo4 suppressed glioma-induced endothelial cell proliferation, migration and tube formation in vitro by inhibiting VEGR2-mediated activation of PI3K/AKT and FAK signaling pathways.
authors.affiliation: Department of Neurosurgery, Shengjing Hospital of China Medical University, Shenyang, China.
authors.forename: Heng
authors.initials: H
authors.lastname: Cai
authors.forename: Yixue
authors.initials: Y
authors.lastname: Xue
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.forename: Yi
authors.initials: Y
authors.lastname: Hu
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Wang
authors.forename: Wenjing
authors.initials: W
authors.lastname: Liu
authors.forename: Zhiqing
authors.initials: Z
authors.lastname: Li
authors.forename: Yunhui
authors.initials: Y
authors.lastname: Liu
mesh_terms: D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D002934:Cinnamates / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005910:Glioma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D018919:Neovascularization, Physiologic / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000098552:Slit Homolog 2 Protein; D000097905:Roundabout Proteins
chemical_list: D002867:Chromones; D002934:Cinnamates; D017077:Culture Media, Conditioned; D051417:Focal Adhesion Kinase 1; D036341:Intercellular Signaling Peptides and Proteins; D009025:Morpholines; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D011956:Receptors, Cell Surface; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; D000098552:Slit Homolog 2 Protein; C462951:ROBO4 protein, human; D000097905:Roundabout Proteins; C483044:SU 1498; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C496050:PTK2 protein, human