title: Inhibition of HUVEC tubulogenesis by hederacolchiside-A1 is associated with plasma membrane cholesterol sequestration and activation of the Ha-Ras/MEK/ERK cascade.
abstract: OBJECTIVE
  Neoangiogenesis is critical to cancer proliferation and metastasis and constitutes an attractive target for cancer therapy. It has previously been demonstrated that hederacolchiside-A1 (HCol-A1), a triterpenoid saponin from Hedera colchica Koch, has antimelanoma potential. The goal of this study was to evaluate, in vitro, if in addition to its tumoricidal effect on melanoma cells, HCol-A1 might affect endothelial cell network formation.
  
  
  METHODS
  We investigated whether HCol-A1 affects matrigel-induced tubulogenesis and inhibits the viability (WST-1 assay) of human umbilical vein endothelial cells (HUVECs). To provide structure-activity relationships (SAR), studies were conducted on HCol-A1, oleanolic acid and hederacolchiside A (HCol-A), a triterpenoid saponin which possess the same sugar sequence as Hcol-A1. Plasma membrane cholesterol sequestration was studied by labelling with [3H]cholesterol and assayed with HCol-A1-cholesterol complexes. HCol-A1 signalling was investigated using immunoassays.
  
  
  RESULTS
  In contrast to HCol-A and oleanolic acid, HCol-A1 inhibited matrigel-induced angiogenesis at micromolar concentration. Plasma membrane cholesterol sequestration was found to be critical for this activity. Activation of the Ras/MEK/ERK cascade appears to be one of the mechanisms by which Hcol-A1 affects HUVEC network formation. The predominant activation of the Ha-Ras isoform, which decreases HUVEC-tolerance to apoptosis, might contribute to the high susceptibility of this cell line to HCol-A1.
  
  
  CONCLUSIONS
  Since cholesterol sequestration affects cell confluence-dependent remodelling of endothelial membranes and vascular endothelial growth factor receptor-2 activity, these results raise the possibility that Hcol-A1 might slow-down cancer proliferation and metastasis in vivo by inhibiting critical aspects of neoangiogenesis. Further in vivo studies are needed to verify this hypothesis.
authors.affiliation: Laboratoire de Pharmacognosie et Biotechnologies, Faculté de Pharmacie, UMR-INSERM U-484-UdA-CJP, Place H Dunant, Rue Montalembert, BP 184, 63001, Clermont-Fd Cedex, France. chantal.barthomeuf@u-clermont1.fr
authors.forename: Chantal
authors.initials: C
authors.lastname: Barthomeuf
authors.forename: Dominique
authors.initials: D
authors.lastname: Boivin
authors.forename: Richard
authors.initials: R
authors.lastname: Béliveau
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D002784:Cholesterol / Q000097:blood; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D009389:Neovascularization, Pathologic / Q000517:prevention & control*; D009828:Oleanolic Acid / Q000494:pharmacology; D012503:Saponins / Q000494:pharmacology*; D014471:Umbilical Veins; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D012503:Saponins; C467827:hederacolchisid A1; C412406:hederacolchiside A; D009828:Oleanolic Acid; D002784:Cholesterol; D048051:p38 Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; D018631:ras Proteins