The invasion and metastasis of tumor cells has been shown to require proteolytic activity in order to degrade components of the extracellular matrix (ECM). The hydrolysis of the ECM appears to facilitate tumor cell migration contributing to the metastatic dissemination of malignant cells (1). A major group of proteases that has been directly associated with tumor metastasis is the matrix metalloproteinases (MMPs), a family of endopeptidases known to cleave many ECM proteins (1). The MMPs are multidomain proteases that contain a zinc atom in the active site and are produced in a latent inactive form (zymogen) (2). Acquisition of enzymatic activity requires cleavage of the inhibitory N-terminal domain (3). Thus, generation of the active form usually occurs concomitantly with a decrease in molecular mass and exposure of the active site. Once activated, all the MMPs are specifically inhibited by a group of endogenous protease inhibitors known as the tissue inhibitors of metalloproteinases (TIMPs), which bind to the active site inhibiting catalytic activity (4).