Previous reports showed that urokinase plasminogen activator (uPA) converts plasminogen to plasmin which then activates matrix metalloproteinases (MMPs). Here, we report that uPA directly cleaved pro-MMP-9 in a time-dependent manner at both C- and N-terminus and generated two gelatinolytic bands. uPA-activated-MMP-9 efficiently degraded fibronectin and blocked by uPA inhibitor B428 and recombinant tissue inhibitor of metalloproteinase-1 (TIMP-1). B428 inhibited basal and PMA-induced active MMP-9 in glioblastomas (GBM) U1242 cell media as well as cell invasion in vitro. A combination of MMP-9 and uPA antibodies more significantly inhibited U1242 cell invasion than uPA or MMP-9 antibody alone. Both uPA and MMP-9 were highly expressed in U1242 cell and GBM patient specimens. Furthermore, two active MMP-9 fragments with identical molecular weights to the uPA-activated MMP-9 products were detected in GBM patient specimens. These results suggest that uPA-mediated direct activation of MMP-9 may promote GBM cell invasion. (C) 2008 Elsevier Inc. All rights reserved.