title: Bioavailability of VEGF in tumor-shed vesicles depends on vesicle burst induced by acidic pH.
abstract: Tumor angiogenesis is regulated by a dynamic cross-talk between tumor cells and the host microenvironment. Because membrane vesicles shed by tumor cells are known to mediate several tumor-host interactions, we determined whether vesicles might also stimulate angiogenesis. Vesicles shed by human ovarian carcinoma cell lines CABA I and A2780 stimulated the motility and invasiveness of endothelial cells in vitro. Enzyme-linked immunosorbent assay and Western blot analysis revealed relevant amounts of vascular endothelial growth factor (VEGF) and the two matrix metalloproteinases MMP-2 and MMP-9, but not fibroblast growth factor-2, contained in shed vesicles. An A2780 cell-derived clone transfected to overexpress VEGF shed the same amount of vesicles as did a control clone, but contained significantly more VEGF within the vesicles. Despite a greater amount of VEGF in vesicles of the overexpressing clone, vesicles of both clones stimulated endothelial cell motility to comparable levels, suggesting that VEGF was stored within the vesicle and was unavailable. Only following vesicle burst induced by acidic pH (a characteristic of the tumor microenvironment) was VEGF released, leading to significantly higher stimulation of cell motility. Thus, tumor-shed membrane vesicles carry VEGF and release it in a bioactive form in conditions typical of the tumor microenvironment.
authors.affiliation: Department of Oncology, Mario Negri Institute for Pharmacological Research, Bergamo, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Taraboletti
authors.forename: Sandra
authors.initials: S
authors.lastname: D'Ascenzo
authors.forename: Ilaria
authors.initials: I
authors.lastname: Giusti
authors.forename: Daniela
authors.initials: D
authors.lastname: Marchetti
authors.forename: Patrizia
authors.initials: P
authors.lastname: Borsotti
authors.forename: Danilo
authors.initials: D
authors.lastname: Millimaggi
authors.forename: Raffaella
authors.initials: R
authors.lastname: Giavazzi
authors.forename: Antonio
authors.initials: A
authors.lastname: Pavan
authors.forename: Vincenza
authors.initials: V
authors.lastname: Dolo
mesh_terms: D000818:Animals; D001682:Biological Availability; D002417:Cattle; D045744:Cell Line, Tumor; D002465:Cell Movement; D002478:Cells, Cultured; D003470:Culture Media; D004730:Endothelium, Vascular / Q000166:cytology / Q000473:pathology* / Q000502:physiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009361:Neoplasm Invasiveness; D009389:Neovascularization, Pathologic / Q000473:pathology*; D010051:Ovarian Neoplasms / Q000098:blood supply* / Q000473:pathology*; D014471:Umbilical Veins; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000493:pharmacokinetics*
chemical_list: D003470:Culture Media; D042461:Vascular Endothelial Growth Factor A