title: Specific interaction of tissue-type plasminogen activator (t-PA) with annexin II on the membrane of pancreatic cancer cells activates plasminogen and promotes invasion in vitro.
abstract: BACKGROUND
  Overexpression of tissue plasminogen activator (t-PA) in pancreatic cancer cells promotes invasion and proliferation in vitro and tumour growth and angiogenesis in vivo.
  
  
  OBJECTIVE
  To understand the mechanisms by which t-PA favours cancer progression, we analysed the surface membrane proteins responsible for binding specifically t-PA and studied the contribution of this interaction to the t-PA promoted invasion of pancreatic cancer cells.
  
  
  METHODS
  The ability of t-PA to activate plasmin and a fluorogenic plasmin substrate was used to analyse the nature of the binding of active t-PA to cell surfaces. Specific binding was determined in two pancreatic cancer cell lines (SK-PC-1 and PANC-1), and complex formation analysed by co-immunoprecipitation experiments and co-immunolocalisation in tumours. The functional role of the interaction was studied in Matrigel invasion assays.
  
  
  RESULTS
  t-PA bound to PANC-1 and SK-PC-1 cells in a specific and saturable manner while maintaining its activity. This binding was competitively inhibited by specific peptides interfering with the interaction of t-PA with annexin II. The t-PA/annexin II interaction on pancreatic cancer cells was also supported by co-immunoprecipitation assays using anti-t-PA antibodies and, reciprocally, with antiannexin II antibodies. In addition, confocal microscopy showed t-PA and annexin II colocalisation in tumour tissues. Finally, disruption of the t-PA/annexin II interaction by a specific hexapeptide significantly decreased the invasive capacity of SK-PC-1 cells in vitro.
  
  
  CONCLUSIONS
  t-PA specifically binds to annexin II on the extracellular membrane of pancreatic cancer cells where it activates local plasmin production and tumour cell invasion. These findings may be clinically relevant for future therapeutic strategies based on specific drugs that counteract the activity of t-PA or its receptor annexin II, or their interaction at the surface level.
authors.affiliation: Unitat de Recerca Biomèdica, Hospital Materno-Infantil, Hospitals Vall d'Hebrón, Pg Vall d'Hebrón 119-129, 08035 Barcelona, Spain.
authors.forename: V M
authors.initials: VM
authors.lastname: Díaz
authors.forename: M
authors.initials: M
authors.lastname: Hurtado
authors.forename: T M
authors.initials: TM
authors.lastname: Thomson
authors.forename: J
authors.initials: J
authors.lastname: Reventós
authors.forename: R
authors.initials: R
authors.lastname: Paciucci
mesh_terms: D017306:Annexin A2 / Q000378:metabolism*; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000378:metabolism / Q000502:physiology; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D010958:Plasminogen / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000378:metabolism* / Q000502:physiology; D014407:Tumor Cells, Cultured
chemical_list: D017306:Annexin A2; D009363:Neoplasm Proteins; D010958:Plasminogen; D010959:Tissue Plasminogen Activator