Membrane-type matrix metalloproteinases (MT-MMPs) in cell invasion

Activated gelatinase A is reportedly associated with tumor spread. We identified a novel matrix metalloproteinase that localizes on the cell surface and mediate the activation of progelatinase A. Thus, this progelatinase A activator was named membrane-type matrix metalloproteinase (MT1-MMP). Following the first discovery of MT1-MMP, two other MT-MMPs which can activate progelatinase A were identified (MT2 and MT3-MMP, respectively). Among these three MT-MMPs, MT1-MMP is most often overexpressed in malignant tumor tissues, including lung and stomach carcinomas that contain activated gelatinase A. This suggests that MT1-MMP is most closely associated with the activation of progelatinase A in these tumor tissues. The expression of MT1-MMP also induced binding of gelatinase A to the cell surface by functioning as a receptor. The cell surface localization of proteinases has advantages over pericellular proteolysis. MT1-MMP and its family may play a central role in the cell surface localization and activation of progelatinase A and via this mechanism, tumor cells use exogenous progelatinase A to mediate the proteolysis associated with invasion and metastasis.