ACTIVATION OF TUMOR-CELL MATRIX METALLOPROTEINASE-2 BY NEUTROPHIL PROTEINASES REQUIRES EXPRESSION OF MEMBRANE-TYPE-1 MATRIX METALLOPROTEINASE

Background. Matrix metalloproteinase-2 (MMP-2), an enzyme involved in tumor invasion, is secreted as an inactive proenzyme and requires inte raction with membrane-type 1 MMP (MT1-MMP) for activation. We have pre viously demonstrated that polymorphonuclear neutrophils (PMNs) release a soluble factor(s) that activates pro-MMP-2. Therefore, we tested th e hypothesis that PMN-derived proteinases act in concert with MT1-MMP to activate pro-MMP-2. Methods. Human HT-1080 cells transfected with M T1-MMP cDNA (HT-SE) or the corresponding antisense cDNA (HT-AS) or an empty vector (HT-V), which expressed differing levels of MT1-MMP, were incubated with serum-free human PMN-conditioned medium with or withou t proteinase inhibitors. The culture supernatants were analyzed by gel atin zymography. Results. HT-1080 cells expressing basal (HT-V) or low levels (HT-AS) of MT1-MMP secreted il MMP-2 in proenzyme form (72 kd) . HT-1080 cells with high levels of MT2-MMP (HT-SE) secreted proMMP-2 and a 68 kd intermediate activation product. Addition of PMN-condition ed medium to either HT-SE or HT-V clones resulted in dose-dependent ge neration of active, 62 kd MMP-2. In contrast, when PMN-conditioned med ium was added to HT-AS clones, no MMP-2 activation occurred. Conclusio ns. PMN-derived serine proteinases act in concert with MT1-MMP to acti vate proMMP-2. This finding indicates a potential role for inflammator y cells in promoting extracellular matrix breakdown during tumor invas ion.