Abstract
The expression of several components of the plasminogen–plasmin (P–P) system in tumor
tissues has been shown to have prognostic significance in many human cancers, including
those of the breast, prostate, lung, brain, ovary, stomach, colon, rectum, oral cavity,
kidney, and bone. Mechanisms of action of the individual components have been extensively
studied in tumor cells in vitro and in animal models. By interrupting various putative
pathways involved in tumor progression in several experimental tumor models in animals,
varying degrees of tumor control have been achieved. However, these efforts have thus
far not been able to exert any impact in oncologic clinical practice. A possible explanation
is our incomplete understanding of the complex involvement of the P–P system and its
interactions with other tumorigenic factors. In this article, the role of various
members of the P–P system in cancer is reviewed. Proteolysis via the urokinase-type
plasminogen activator–plasminogen activation pathway tends to enhance tumor growth
and invasion, and its natural inhibitor plasminogen activator inhibitor type 1 may
also enhance tumor growth through the inhibition of apoptosis, enhancing cell proliferation
and the promotion of angiogenesis. Meaningful drug designs for therapeutic intervention
require a thorough understanding of the role of all of the components involved in
this complex mechanism of tumor progression.
Keywords
uPA - PAI-1 - uPA receptor - plasmin