INVASION OF BRAIN-TISSUE BY PRIMARY GLIOMA - EVIDENCE FOR THE INVOLVEMENT OF UROKINASE-TYPE PLASMINOGEN-ACTIVATOR AS AN ACTIVATOR OF TYPE-IV COLLAGENASE

The immunocharacterization of a metalloproteinase isolated from rat glioma cell conditioned medium is described and confirms that the enzyme is identical to type IV collagenase. Free, active plasminogen activator (PA) and PA-PAI complexes were identified as being secreted by the same cells. Using affinity-purified metalloproteinase we demonstrate that the enzyme can be partially activated by u-PA but not by plasmin in vitro. On the basis of these findings and previous published work we propose a scheme for the proteolytic degradation of normal brain tissue during tumour invasion. © 1992 Academic Press, Inc.