HT-1080 FIBROSARCOMA CELL-MATRIX DEGRADATION AND INVASION ARE INHIBITED BY THE MATRIX-ASSOCIATED SERINE-PROTEASE INHIBITOR TFPI-2 33 KDA MSPI/

The urokinase-urokinase receptor system plays a dominant role in the d egradation and invasion of extracellular matrix (ECM) by tumor cells. In this system, urokinase bound to its cell receptor converts plasmino gen to plasmin, a broad-spectrum serine protease that participates in the degradation and invasion of connective tissues by tumor cells. In this study, we evaluated whether these activities of plasmin are inhib ited by a newly characterized human 32 kDa recombinant serine protease inhibitor called trypsin/tissue factor pathway inhibitor-2 (rTFPI-2). We found that rTFPI-2 dose-dependently inhibited fluid-phase plasmin as well as plasmin generated on the ECM and/or the cell surface of MT- 1080 fibrosarcoma cells. The degradation of radiolabeled matrix as wel l as Matrigel invasion by these tumor cells is also inhibited by rTFPI -2 in a dose dependent fashion. We have reported that rTFPI-2 is ident ical to 33 kDa extracellular matrix-associated serine protease inhibit or (33 kDa MSPI), whereas the 31 and 27 kDa MSPIs are under-glycosylat ed forms of the 33 kDa MSPI. We therefore evaluated the ability of MSP Is from the ECM of dermal fibroblasts to inhibit plasmin and found tha t the plasmin activity was effectively blocked by the MSPIs. We have a lso evaluated whether the MT-1080 cells synthesize and secrete the MSP Is and found that the synthesis and secretion of the MSPIs was undetec table in these cells. Collectively, our results suggest that rTFPI-2/3 3 kDa MSPI inhibits plasmin on the tumor cell and ECM surfaces as well as the degradation and invasion of matrix by MT-1080 fibrosarcoma cel ls. (C) 1998 Wiley-Liss, Inc.