In order to investigate the role of matrix metalloproteinases (MMP) in tumor invasion and metastases, we have focused on the multilevel regulation of these enzymes. Studies have shown that in contrast with other members of the MMP enzyme family, 72 kDa gelatinase A levels are increased in response to TGFbeta1, are unaffected by the tumor promoting phorbol esters, and show elevated levels in colorectal, breast, thyroid, ovarian and bladder tumor tissues when compared with adjacent normal mucosa tissues. We have identified a cellular activation mechanism which is cell surface associated and specific for the 72 kDa gelatinase A enzyme, and which can be induced by pretreatment with phorbol esters or concanavalin A. This cellular activation mechanism does not affect other members of the collagenase gene family. This activation mechanism appears to require cell surface binding of the gelatinase A enzyme, and we have identified a putative gelatinase A receptor. We have studied the structure of the latent enzyme TIMP-2 complex through production of enzyme deletion mutants and enzyme inhibitor cross linking studies. These studies demonstrate that the 72 kDa gelatinase A has at least two TIMP-2 binding domains. The principal binding domain is located in the C-terminal, hemopexin-like domain of the enzyme. This binding site is available in the latent enzyme form. The second binding site is at the enzyme active site and only becomes available following organomercurial mediated enzyme activation. Finally, antipeptide antibodies against the 92 kDa gelatinase B, interstitial collagenase, stromelysin-1 and stromelysin-2 have been prepared and characterized.
