The urokinase-type plasminogen activator system in cancer metastasis: a review.
The urokinase-type plasminogen activator (u-PA) system consists of the serine proteinases plasmin and u-PA; the serpin inhibitors alpha2-anti-plasmin, PAI-1 and PAI-2; and the u-PA receptor (u-PAR). Two lines of evidence have strongly suggested an important and apparently causal role for the u-PA system in cancer metastasis: results from experimental model systems with animal tumor metastasis and the finding that high levels of u-PA, PAI-1 and u-PAR in many tumor types predict poor patient prognosis. We discuss here recent observations related to the molecular and cellular mechanisms underlying this role of the u-PA system. Many findings suggest that the system does not support tumor metastasis by the unrestricted enzyme activity of u-PA and plasmin. Rather, pericellular molecular and functional interactions between u-PA, u-PAR, PAI-1, extracellular matrix proteins, integrins, endocytosis receptors and growth factors appear to allow temporal and spatial re-organizations of the system during cell migration and a selective degradation of extracellular matrix proteins during invasion. Differential expression of components of the system by cancer and non-cancer cells, regulated by paracrine mechanisms, appear to determine the involvement of the system in cancer cell-directed tissue remodeling. A detailed knowledge of these processes is necessary for utilization of the therapeutic potential of interfering with the action of the system in cancers.
Andreasen
P A
PA
Department of Molecular and Structural Biology, University of Aarhus, Denmark. pa@mbio.aau.dk
Kjøller
L
L
Christensen
L
L
Duffy
M J
MJ
D000818:Animals; D002465:Cell Movement; D006801:Humans; D009362:Neoplasm Metastasis; D009374:Neoplasms, Experimental / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D055293:Receptors, Urokinase Plasminogen Activator; D012697:Serine Endopeptidases / Q000378:metabolism; D015843:Serpins / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000502:physiology*
C524898:PLAUR protein, human; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D015843:Serpins; D012697:Serine Endopeptidases; D014568:Urokinase-Type Plasminogen Activator