The urokinase receptor (CD87) represents a central mediator of growth factor-induced endothelial cell migration

Summary

Angiogenesis, the sprouting of blood vessels form pre-existing vasculature after injury or in neoplastic diseases, is initiated by growth factor-induced endothelial cell migration. Recently, the major angiogenic growth factor VEGF₁₆₅ has become the target of therapeutic interventions. However, this approach has been clinically proven to be of limited efficacy, which might be due to the fact that tumour angiogenesis is not only induced by VEGF, but also by a variety of other growth factors. Thus, the identification of a common downstream mediator of growth-factor-induced endothelial cell migration is mandatory to effectively interfere with (tumour-) angiogenesis. We found that the urokinase-type plas-minogen activator (uPA)-system, which affects proteolytic as well as adhesive capacities, represents an essential regulatory mechanism in growth factor-induced endothelial cell migration and invasion. This mechanism was not limited to VEGF₁₆₅, but mediated pro-angiogenic endothelial cell behaviour induced by various growth factors. Thus, VEGF165, VEGF-E, FGF-2, EGF as well as HGF induced a PI3k-dependent activation of pro-uPA when bound to uPAR, which led to an increase in cell surface fibrinolytic activity. As a consequence, uPAR became internalised and redistributed via LDLR-proteins. Interference with these events led to a reduced migratory response of endothelial cells towards VEGF in vitro as well as endothelial cell invasion in vivo. These data give first evidence that the uPA-system, which represents the only level-of-evidence-1 cancer biomarker system for prognosis and/or prediction in node negative breast cancer, might directly affect (tumour-) angiogenesis.

Keywords

uPA/plasminogen system - angiogenesis - endothelial cells - growth factors

^* Deceased August 28^th, 2010.

• References

• 1 Carmeliet P. Mechanisms of angiogenesis and arteriogenesis. Nat Med 2000; 06: 389-395.
• 2 Schmidt-Erfurth UE. et al. Efficacy and safety of monthly versus quarterly ranibizumab treatment in neovascular age-related macular degeneration: the EXCITE study. Ophthalmology 2011; 118: 831-839.
• 3 Gerger A. et al. Molecular predictors of response to antiangiogenesis therapies. Cancer J 2011; 17: 134-141.
• 4 Fischer C. et al. FLT1 and its ligands VEGFB and PlGF: drug targets for anti-angiogenic therapy?. Nat Rev Cancer 2008; 08: 942-956.
• 5 Ferrara N. Vascular endothelial growth factor: basic science and clinical progress. Endocr Rev 2004; 25: 581-611.
• 6 Smith HW, Marshall CJ. Regulation of cell signalling by uPAR. Nat Rev Mol Cell Biol 2010; 11: 23-36.
• 7 Prager GW. et al. Vascular endothelial growth factor (VEGF) induces rapid prourokinase (pro-uPA) activation on the surface of endothelial cells. Blood 2004; 103: 955-962.
• 8 Prager GW. et al. Vascular Endothelial Growth Factor Receptor-2-Induced Initial Endothelial Cell Migration Depends on the Presence of the Urokinase Receptor. Circ Res 2004; 94: 1562-1570.
• 9 Nykjaer A. et al. Recycling of the urokinase receptor upon internalization of the uPA:serpin complexes. EMBO J 1997; 16: 2610-2620.
• 10 Tarui T. et al. Urokinase-type plasminogen activator receptor (CD87) is a ligand for integrins and mediates cell-cell interaction. J Biol Chem 2001; 276: 3983-3990.
• 11 Wei Y. et al. Regulation of integrin function by the urokinase receptor. Science 1996; 273: 1551-1555.
• 12 Felsenfeld DP. et al. Ligand binding regulates the directed movement of beta1 integrins on fibroblasts. Nature 1996; 383: 438-440.
• 13 Lauffenburger DA, Horwitz AF. Cell migration: a physically integrated molecular process. Cell 1996; 84: 359-369.
• 14 Lawson MA, Maxfield FR. Ca(2+)- and calcineurin-dependent recycling of an integrin to the front of migrating neutrophils. Nature 1995; 377: 75-79.
• 15 Schwarz HP. et al. Involvement of low-density lipoprotein receptor-related protein (LRP) in the clearance of factor VIII in von Willebrand factor-deficient mice. Blood 2000; 95: 1703-1708.
• 16 Mechtcheriakova D. et al. Specificity, diversity, and convergence in VEGF and TNF-alpha signaling events leading to tissue factor up-regulation via EGR-1 in endothelial cells. FASEB J 2001; 15: 230-242.
• 17 Huber J. et al. The Isoprostane 8-iso-PGE(2) Stimulates Endothelial Cells to Bind Monocytes via Cyclic AMP- and p38 MAP Kinase-Dependent Signaling Pathways. Antioxid Redox Signal 2003; 05: 163-169.
• 18 Carmeliet P. Angiogenesis in life, disease and medicine. Nature 2005; 438: 932-936.
• 19 Mochizuki Y. et al. Negative regulation of urokinase-type plasminogen activator production through FGF-2-mediated activation of phosphoinositide 3-kinase. Oncogene 2002; 21: 7027-7033.
• 20 Zubilewicz A. et al. Two distinct signalling pathways are involved in FGF2-stimulated proliferation of choriocapillary endothelial cells: a comparative study with VEGF. Oncogene 2001; 20: 1403-1413.
• 21 Karsan A. et al. Fibroblast growth factor-2 inhibits endothelial cell apoptosis by Bcl-2-dependent and independent mechanisms. Am J Pathol 1997; 151: 1775-1784.
• 22 Matsumoto T. et al. p38 MAP kinase negatively regulates endothelial cell survival, proliferation, and differentiation in FGF-2-stimulated angiogenesis. J Cell Biol 2002; 156: 149-160.
• 23 Hirata A. et al. Direct inhibition of EGF receptor activation in vascular endothelial cells by gefitinib ('Iressa', ZD1839). Cancer Sci 2004; 95: 614-618.
• 24 Sengupta S. et al. Targeting of mitogen-activated protein kinases and phosphatidylinositol 3 kinase inhibits hepatocyte growth factor/scatter factor-induced angiogenesis. Circulation 2003; 107: 2955-2961.
• 25 Goldman E. The growth of malignant disease in man and the lower animals with special reference to the vascular system. Lancet 1907; 02: 1236-1240.
• 26 Folkman J. Tumor angiogenesis: therapeutic implications. N Engl J Med 1971; 285: 1182-1186.
• 27 Prager GW, Poettler M. Angiogenesis in cancer. Basic mechanisms and therapeutic advances. Hamostaseologie 2012; 32: 105-114.
• 28 Cassidy J. et al. Randomized phase III study of capecitabine plus oxaliplatin compared with fluorouracil/folinic acid plus oxaliplatin as first-line therapy for metastatic colorectal cancer. J Clin Oncol 2008; 26: 2006-2012.
• 29 Saltz LB. et al. Bevacizumab in combination with oxaliplatin-based chemotherapy as first-line therapy in metastatic colorectal cancer: a randomized phase III study. J Clin Oncol 2008; 26: 2013-2019.
• 30 Loges S. et al. Silencing or fueling metastasis with VEGF inhibitors: antiangiogenesis revisited. Cancer Cell 2009; 15: 167-170.
• 31 Malla RR. et al. Cathepsin B and uPAR knockdown inhibits tumor-induced angiogenesis by modulating VEGF expression in glioma. Cancer Gene Ther 2011; 18: 419-434.
• 32 Alexander RA. et al. VEGF-induced endothelial cell migration requires urokinase receptor (uPAR)-dependent integrin redistribution. Cardiovasc Res 2012; 94: 125-135.
• 33 Czekay RP. et al. Plasminogen activator inhibitor-1 detaches cells from extracellular matrices by inactivating integrins. J Cell Biol 2003; 160: 781-791.
• 34 Prager GW. et al. Urokinase mediates endothelial cell survival via induction of the X-linked inhibitor of apoptosis protein. Blood 2009; 113: 1383-1390.
• 35 Brunner PM. et al. Density enhanced phosphatase-1 down-regulates urokinase receptor surface expression in confluent endothelial cells. Blood 2011; 117: 4154-4161.
• 36 Schmitt M. et al. Clinical utility of level-of-evidence-1 disease forecast cancer biomarkers uPA and its inhibitor PAI-1. Expert Rev Mol Diagn 2010; 10: 1051-1067.
• 37 Buchler P. et al. Transcriptional regulation of urokinase-type plasminogen activator receptor by hypoxia-inducible factor 1 is crucial for invasion of pancreatic and liver cancer. Neoplasia 2009; 11: 196-206.
• 38 Kietzmann T. et al. Induction of the plasminogen activator inhibitor-1 gene expression by mild hypoxia via a hypoxia response element binding the hypoxia-inducible factor-1 in rat hepatocytes. Blood 1999; 94: 4177-4185.
• 39 Paez-Ribes M. et al. Antiangiogenic therapy elicits malignant progression of tumors to increased local invasion and distant metastasis. Cancer Cell 2009; 15: 220-231.
• 40 Ebos JM. et al. Accelerated metastasis after short-term treatment with a potent inhibitor of tumor angiogenesis. Cancer Cell 2009; 15: 232-239.
• 41 Nozaki S. et al. Targeting urokinase-type plasminogen activator and its receptor for cancer therapy. Anticancer Drugs 2006; 17: 1109-1117.
• 42 Kenny HA. et al. Targeting the urokinase plasminogen activator receptor inhibits ovarian cancer metastasis. Clin Cancer Res 2011; 17: 459-471.