title: Activated thrombin-activatable fibrinolysis inhibitor attenuates the angiogenic potential of endothelial cells: potential relevance to the breast tumour microenvironment.
abstract: Thrombin-activatable fibrinolysis inhibitor (TAFI) is a basic carboxypeptidase zymogen present in blood plasma. Proteolytic activation of TAFI by thrombin, thrombin in complex with the endothelial cell cofactor thrombomodulin, or plasmin results in an enzyme (TAFIa) that removes carboxyl-terminal lysine residues from protein and peptide substrates, including cell-surface plasminogen receptors. TAFIa is therefore capable of inhibiting plasminogen activation in the pericellular milieu. Since plasminogen activation has been linked to angiogenesis, TAFIa could therefore have anti-angiogenic properties, and indeed TAFIa has been shown to inhibit endothelial tube formation in a fibrin matrix. In this study, the TAFI pathway was manipulated by providing exogenous TAFI or TAFIa or by adding a potent and specific inhibitor of TAFIa. We found that TAFIa elicited a series of anti-angiogenic responses by endothelial cells, including decreased endothelial cell proliferation, cell invasion, cell migration, tube formation, and collagen degradation. Moreover, TAFIa decreased tube formation and proteolysis in endothelial cell culture grown alone and in co-culture with breast cancer cell lines. In accordance with these findings, inhibition of TAFIa increased secretion of matrix metalloprotease proenzymes by endothelial and breast cancer cells. Finally, treatment of endothelial cells with TAFIa significantly inhibited plasminogen activation. Taken together our results suggest a novel role for TAFI in inhibiting tumour angiogenic behaviors in breast cancer.
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada.|Department of Biochemistry, Room 4245A Robarts Research Institute, University of Western Ontario, 1151 Richmond Street North, London, ON, N5B 3P7, Canada.
authors.forename: Zainab A
authors.initials: ZA
authors.lastname: Bazzi
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Balun
authors.affiliation: Department of Biological Sciences, University of Windsor, Windsor, ON, Canada.
authors.forename: Dora
authors.initials: D
authors.lastname: Cavallo-Medved
authors.affiliation: Department of Biological Sciences, University of Windsor, Windsor, ON, Canada.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Porter
authors.affiliation: Department of Biochemistry, Room 4245A Robarts Research Institute, University of Western Ontario, 1151 Richmond Street North, London, ON, N5B 3P7, Canada. mboffa@uwo.ca.
authors.forename: Michael B
authors.identifier: 0000-0003-1211-3064
authors.initials: MB
authors.lastname: Boffa
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology*; D025901:Carboxypeptidase B2 / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D018920:Coculture Techniques; D024141:Collagen Type IV / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D042783:Endothelial Cells / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000494:pharmacology; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000188:drug therapy*; D010958:Plasminogen / Q000037:antagonists & inhibitors; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: D024141:Collagen Type IV; D004792:Enzyme Precursors; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D010958:Plasminogen; C585364:CPB2 protein, human; D025901:Carboxypeptidase B2; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2; C579270:MMP9 protein, human; D020780:Matrix Metalloproteinase 9
keywords: Angiogenesis; Breast cancer; Endothelial cells; Plasminogen; TAFI