The urokinase-type plasminogen activator system in cancer metastasis: a review

Int J Cancer. 1997 Jul 3;72(1):1-22. doi: 10.1002/(sici)1097-0215(19970703)72:1<1::aid-ijc1>;2-z.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Cell Movement
  • Humans
  • Neoplasm Metastasis*
  • Neoplasms, Experimental / metabolism
  • Receptors, Cell Surface / metabolism
  • Receptors, Urokinase Plasminogen Activator
  • Serine Endopeptidases / metabolism
  • Serpins / metabolism
  • Urokinase-Type Plasminogen Activator / physiology*


  • PLAUR protein, human
  • Receptors, Cell Surface
  • Receptors, Urokinase Plasminogen Activator
  • Serpins
  • Serine Endopeptidases
  • Urokinase-Type Plasminogen Activator