Activation of progelatinase A (MMP-2) by neutrophil elastase, cathepsin G, and proteinase-3: A role for inflammatory cells in tumor invasion and angiogenesis

Gelatinase A (MMP‐2), a matrix metalloproteinase (MMP) involved in tumor invasion and angiogenesis, is secreted as an inactive zymogen (proMMP‐2) and activated by proteolytic cleavage. Here we report that polymorphonuclear neutrophil (PMN)‐derived elastase, cathepsin G, and proteinase‐3 activate proMMP‐2 through a mechanism that requires membrane‐type 1 matrix metalloproteinase (MT1‐MMP) expression. Immunoprecipitation of human PMN‐conditioned medium with a mixture of antibodies to elastase, cathepsin G, and proteinase‐3 abolished proMMP‐2 activation, whereas individual antibodies were ineffective. Incubation of HT1080 cells with either purified PMN elastase or cathepsin G or proteinase‐3 resulted in dose‐and time‐dependent proMMP‐2 activation. Addition of PMN‐conditioned medium to MT1‐MMP expressing cells resulted in increased proMMP‐2 activation and in vitro invasion of extracellular matrix (ECM), but had no effect with cells that express no MT1‐MMP. MMP‐2 activation by PMN‐conditioned medium or purified elastase was blocked by the elastase inhibitor α1‐antitrypsin but not by Batimastat, an MMP inhibitor, showing that elastase activation of MMP‐2 is not mediated by MMP activities. The PMN‐conditioned medium‐induced increase in cell invasion was blocked by Batimastat as well as by α1‐antitrypsin, showing that PMN serine proteinases trigger a proteinase cascade that entails proMMP‐2 activation: this gelatinase is the downstream effector of the proinvasive activity of PMN proteinases. These findings indicate a novel role for PMN‐mediated inflammation in a variety of tissue remodeling processes including tumor invasion and angiogenesis. © 2001 Wiley‐Liss, Inc.