Clinical & Experimental Metastasis

, Volume 34, Issue 2, pp 155–169

Activated thrombin-activatable fibrinolysis inhibitor attenuates the angiogenic potential of endothelial cells: potential relevance to the breast tumour microenvironment

  • Zainab A. Bazzi
  • Jennifer Balun
  • Dora Cavallo-Medved
  • Lisa A. Porter
  • Michael B. Boffa
Research Paper

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.

Keywords

TAFI Angiogenesis Breast cancer Plasminogen Endothelial cells 

Abbreviations

BME

Basement membrane extract

CM

Conditioned media

ε-ACA

ε-aminocaproic acid

ECM

Extracellular matrix

HUVECs

Human umbilical vein endothelial cells

MMPs

Matrix metalloproteinases

PAS

Plasminogen activation system

PTCI

Potato tuber carboxypeptidase inhibitor

TAFI

Thrombin-activatable fibrinolysis inhibitor

TAFIa

Activated thrombin-activatable fibrinolysis inhibitor

TM

Thrombomodulin

tPA

Tissue-type plasminogen activator

uPA

Urokinase plasminogen activator

uPAR

Urokinase plasminogen activator receptor

VEGF

Vascular endothelial growth factor

Supplementary material

10585_2017_9837_MOESM1_ESM.pdf (324 kb)
Supplementary material 1 (PDF 324 KB)

Copyright information

© Springer Science+Business Media Dordrecht 2017

Authors and Affiliations

  1. 1.Department of Chemistry and BiochemistryUniversity of WindsorWindsorCanada
  2. 2.Department of Biochemistry, Room 4245A Robarts Research InstituteUniversity of Western OntarioLondonCanada
  3. 3.Department of Biological SciencesUniversity of WindsorWindsorCanada

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