Matrix metalloproteinases (MMPs) are involved in the remodeling processes of the extracellular matrix and the basement membrane. Most MMPs are composed of a regulatory, a catalytic, and a hemopexin subunit. In many tumors the expression of MMP-9 correlates with local tumor growth, invasion, and metastasis. To analyze the role of the hemopexin domain in these processes, the MMP-9 hemopexin domain (MMP-9-PEX) was expressed as a glutathione S-transferase fusion protein in Escherichia coli. After proteolytic cleavage, the isolated PEX domain was purified by size exclusion chromatography. In a zymography assay, MMP-9-PEX was able to inhibit MMP-9 activity. The association and dissociation rates for the interaction of MMP-9-PEX with gelatin were determined by plasmon resonance. From the measured rate constants, the dissociation constant was calculated to be K d ‫؍‬ 2,4 ؋ 10 ؊8 M, demonstrating a high affinity between MMP-9-PEX and gelatin. In Boyden chamber experiments the recombinant MMP-9-PEX was able to inhibit the invasion of melanoma cells secreting high amounts of MMP-9 in a dose-dependent manner. These data demonstrate for the first time that the hemopexin domain of MMP-9 has a high affinity binding site for gelatin, and the particular recombinant domain is able to block MMP-9 activity and tumor cell invasion. Because MMP-9 plays an important role in metastasis, this antagonistic effect may be utilized to design MMP inhibition-based cancer therapy.Matrix metalloproteinases (MMPs) 1 are a family of zinc metallo-endopeptidases secreted by cells. They are responsible for most of the turnover of matrix components. The MMPs are produced as zymogens with a signal sequence and propeptide segment that has to be removed during activation. The propeptide domain contains a conserved cysteine that chelates the zinc in the active site. The gelatinases MMP-2 and MMP-9 contain fibronectin type II domains that are inserted in the middle of the catalytic domain, presumably to enhance substrate binding (1). MMP-9 also has a collagen type V-like domain located between the catalytic and the C-terminal hemopexin domain (Fig. 1). All but two MMPs (MMP-7 and MMP-26) contain a regulatory subunit, the hemopexin domain, separated from the catalytic domain by a variable hinge region (2). This domain is thought to confer much of the substrate specificity to the MMPs (3). It is involved in activation as well as inhibition of MMPs (3,4) and may enhance substrate binding and specificity (5). The hinge region also confers specificity to the MMPs either by direct binding of the substrate or by setting the orientation of the hemopexin domain and the catalytic domain (6). The hemopexin domain of MMP-2 is known to bind heparin (7). Heparin has been shown to potentiate the activities of some MMPs, and MMPs are often found associated with heparin sulfate glycosaminoglycans on the cell surface (8). The overall three-dimensional structure of the hemopexin domain is a four-bladed propeller with a calcium binding site nestled in the folds (3). A fragme...

Taking into account our earlier studies, we conclude that most cases of colorectal carcinogenesis are characterized by enhanced expression of MMP-7, -13, -3 and the gelatinases, whereas MMP-1-expression is very inconsistent and not overexpressed in many cases. MMP-7 inhibition as well as inhibition of MMP-13 and MMP-3 may be a useful preventive or therapeutic adjunct in colorectal cancer.

In conclusion, TIMP-1 expression is up-regulated in the early phase of toxic liver injury by proinflammatory cytokines such as TNF-alpha and IL-1beta in rodents. Pharmacological inactivation of these cytokines significantly reduces TIMP-1 gene expression. Our data provide a potential new antifibrotic approach.