title: Upregulated autocrine vascular endothelial growth factor (VEGF)/VEGF receptor-2 loop prevents apoptosis in haemangioma-derived endothelial cells.
abstract: BACKGROUND
  The autocrine vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR)-2 loop is required to maintain the transformed phenotype of many tumours, in part, by preventing apoptotic cell death in response to many different stimuli. However, it is unclear whether constitutive VEGF/VEGFR-2 activation in haemangioma-derived endothelial cells (HaemECs) can lead to a general suppression of apoptosis.
  
  
  OBJECTIVE
  The objective of this study was to investigate whether the autocrine VEGF loop promotes HaemEC survival via its receptor, VEGFR-2.
  
  
  METHODS
  HaemECs and human umbilical vein endothelial cells (HUVECs) were serum-starved for 12-48 h. Cell apoptosis was measured. The potential mechanisms of VEGF/VEGFR-2-induced HaemEC survival were investigated, and the role of the autocrine VEGF/VEGFR-2 loop in preventing propranolol-induced apoptotic HaemEC death was also analysed.
  
  
  RESULTS
  Compared with HUVECs, HaemECs showed increased resistance to apoptosis induced by serum starvation. Upregulated VEGF/VEGFR-2 signalling in HaemECs induced an autocrine signalling loop, which resulted in Akt activation. Furthermore, this activation of Akt was necessary for VEGF/VEGFR-2-induced protection against serum deprivation-induced HaemEC apoptosis. In addition, Bcl-2, which functions as an anti-apoptotic factor and direct downstream target of PI3K/Akt, was decreased by the inhibition of VEGF/VEGFR-2, which led to an increase in caspase-3 activity, caspase-9 activity and HaemEC apoptosis. Moreover, HaemECs acquired greater resistance to propranolol treatment than HUVECs, whereas inhibition of VEGF/VEGFR-2 signalling in HaemECs sensitized these cells to propranolol-induced apoptosis.
  
  
  CONCLUSIONS
  Our results demonstrate that upregulation of the autocrine VEGF/VEGFR-2 loop can induce general resistance to apoptotic stimuli in HaemECs.
authors.affiliation: Division of Oncology, Department of Pediatric Surgery, Children's Hospital of Fudan University, 399 Wanyuan Road, Shanghai, 201102, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Ji
authors.forename: S
authors.initials: S
authors.lastname: Chen
authors.forename: K
authors.initials: K
authors.lastname: Li
authors.forename: X
authors.initials: X
authors.lastname: Xiao
authors.forename: T
authors.initials: T
authors.lastname: Xu
authors.forename: S
authors.initials: S
authors.lastname: Zheng
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D042783:Endothelial Cells / Q000502:physiology; D006391:Hemangioma / Q000503:physiopathology*; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D010793:Phthalazines / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D015854:Up-Regulation / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000502:physiology*
chemical_list: D000319:Adrenergic beta-Antagonists; D020533:Angiogenesis Inhibitors; D016895:Culture Media, Serum-Free; D010793:Phthalazines; D011412:Propanolamines; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D042461:Vascular Endothelial Growth Factor A; C026777:ICI 118551; C404768:vatalanib; D011433:Propranolol; D040301:Vascular Endothelial Growth Factor Receptor-2; D051057:Proto-Oncogene Proteins c-akt