Heparan sulfate proteoglycans as extracellular docking molecules for matrilysin (matrix metalloproteinase 7)

Matrilysin (MMP-7) induces homotypic adhesion of human colon cancer cells and enhances their metastatic potential in nude mouse model

Matrilysin (MMP-7) is thought to contribute to invasive growth and metastasis of colon carcinoma and many other human cancers. The present study demonstrates that treatment of human colon carcinoma cells with active matrilysin induces cell aggregation in vitro and promotes liver metastasis in nude mice. When two kinds of colon carcinoma cell lines were incubated with active matrilysin, this enzyme efficiently bound to the cell surface and induced loose cell aggregation, which led to E-cadherin-mediated tight cell aggregation. Synthetic MMP inhibitors inhibited both the membrane binding of matrilysin and matrilysin-induced cell aggregation, while TIMP-2 inhibited only the cell aggregation. Two other active MMPs, stromelysin and gelatinase A, neither bound to cell membrane nor induced cell aggregation. Tumor cells in loose cell aggregates could reaggregate even after they were freed from matrilysin and dispersed. When injected into the spleen of nude mice, the tumor cells in the stable aggregates produced much larger metastatic nodules in the livers than control cells and those in the loose aggregates. These results suggest that matrilysin may enhance metastatic potential of tumor cells by processing a cell surface protein(s) and thereby inducing loose and then tight aggregation of tumor cells.

Calcium-induced activation and truncation of promatrix metalloproteinase-9 linked to the core protein of chondroitin sulfate proteoglycans

In the leukemic macrophage cell-line THP-1, a fraction of the secreted matrix metalloproteinase 9 (MMP-9) is linked to the core protein of chondroitin sulfate proteoglycans (CSPG). Unlike the monomeric and homodimeric forms of MMP-9, the addition of exogenous CaCl2 to the proMMP-9/CSPG complex resulted in an active gelatinase due to the induction of an autocatalytic removal of the N-terminal prodomain. In addition, the MMP-9 was released from the CSPG through a process that appeared to be a stepwise truncation of both the CSPG core protein and a part of the C-terminal domain of the gelatinase. The calcium-induced activation and truncation of the MMP-9/CSPG complex was independent of the concentration of the complex, inhibited by the MMP inhibitors EDTA, 1,10-phenanthroline and TIMP-1, but not by general inhibitors of serine, thiol and acid proteinases. This indicated that the activation and truncation process was not due to a bimolecular reaction, but more likely an intramolecular reaction. The negatively charged chondroitin sulfate chains in the proteoglycan were not involved in this process. Other metal-containing compounds like amino-phenylmercuric acetate (APMA), NaCl, ZnCl2 and MgCl2 were not able to induce activation and truncation of the proMMP-9 in this heterodimer. On the contrary, APMA inhibited the calcium-induced process, whereas high concentrations of either MgCl2 or NaCl had no effect. Our results indicate that the interaction between the MMP-9 and the core protein of the CSPG was the causal factor in the calcium-induced activation and truncation of the gelatinase, and that this process was not due to a general electrostatic effect.

Matrilysin (matrix metalloproteinase-7) mediates E-cadherin ectodomain shedding in injured lung epithelium

Matrilysin (matrix metalloproteinase-7) is highly expressed in lungs of patients with pulmonary fibrosis and other conditions associated with airway and alveolar injury. Although matrilysin is required for closure of epithelial wounds ex vivo, the mechanism of its action in repair is unknown. We demonstrate that matrilysin mediates shedding of E-cadherin ectodomain from injured lung epithelium both in vitro and in vivo. In alveolar-like epithelial cells, transfection of activated matrilysin resulted in shedding of E-cadherin and accelerated cell migration. In vivo, matrilysin co-localized with E-cadherin at the basolateral surfaces of migrating tracheal epithelium, and the reorganization of cell-cell junctions seen in wild-type injured tissue was absent in matrilysin-null samples. E-cadherin ectodomain was shed into the bronchoalveolar lavage fluid of bleomycin-injured wild-type mice, but was not shed in matrilysin-null mice. These findings identify E-cadherin as a novel substrate for matrilysin and indicate that shedding of E-cadherin ectodomain is required for epithelial repair.

Role of collagen type II and perlecan in skeletal development

The cartilage extracellular matrix is composed of a dense collagen network that entraps a range of other specialized proteins important for the proper formation and function of the tissue. Loss of two abundant cartilage components, type II collagen and perlecan, has drastic effects on skeletal development. Both collagen II and perlecan mutants have severe and lethal chondrodysplasia characterized by disorganized growth plate, lack of collagen network, defective endochondral bone formation, and abnormal intervertebral disk development. To test whether the reduced collagen density in the perlecan-null cartilage is due to enhanced activity of collagen-degrading proteinases, we have analyzed gelatinase expression and activity in the mutant tissue. Immunohistochemical analysis revealed a weak, but clear, expansion of MMP-9 deposition into the hypertrophic zone of the perlecan-null growth plate. However, in situ and SDS-PAGE zymography showed that the activity of gelatinases (MMP-2 and MMP-9) is not altered in perlecan-null cartilage, suggesting that they are not primarily linked to the reduced fibrillar network observed in the mutant. Likewise, intercrossing of perlecan mutants onto an MMP-9-null background could not rescue the ultrastructural abnormalities of the perlecan-deficient cartilage.

Heparanase and tumor invasion patterns in human oral squamous cell carcinoma xenografts

The role of heparanase, an endo-beta-glucuronidase specifically degrading heparan sulfate (HS) glycosaminoglycans, in the mechanism of cancer cell invasion was investigated. Three human oral squamous cell carcinoma (SCC) cell lines (i.e., HSC-2, HSC-3 and LMF4), exhibiting various degrees of invasiveness to their surrounding tissues, were xenografted to the tongue of SCID mice in order to establish experimental cancer foci. Cancer cells and their surrounding tissues were examined for the expression of heparanase mRNA by an in situ hybridization technique, and for various basement membrane (BM)-associated molecules (i.e., perlecan, laminins and type IV collagen) by immunohistochemical procedures. BM structures surrounding cancer tissues were also examined by electron microscopy. Increasing levels of heparanase mRNA expression were observed with the progression of cancer invasiveness, as manifested by the destruction of BM structures. Enhanced heparanase enzyme activities in cancer tissues with more invasive properties were demonstrated by the disappearance of HS glycosaminoglycans in the face of retained HS proteoglycan core proteins. These results demonstrated a positive correlation between the heparanase enzyme activities and the invasiveness of human oral SCC. The roles of heparanase in cancer cell invasion were not precisely clarified by the present morphological study, but the enhanced heparanase activity in an early phase of BM destruction by cancer cells suggested the participation of this enzyme from the early phase of cancer invasion.

Secretory proprotein convertases PACE4 and PC6A are heparin-binding proteins which are localized in the extracellular matrix. Potential role of PACE4 in the activation of proproteins in the extracellular matrix

PACE4, PC6 and furin are potent subtilisin-like proprotein convertases (SPCs) which are responsible for the activation of transforming growth factor-beta (TGFbeta)-related factors such as bone morphogenetic proteins. Heparan sulfate proteoglycan within the extracellular matrix (ECM) is known to regulate the biological activity of various differentiation factors including TGFbeta-related molecules. PACE4 binds tightly to heparin and its heparin-binding region was found to be a cationic stretch of amino acids between residues 743 and 760. Furthermore, PACE4 was detected in the extracellular material fraction of the HEK293 cells, defined as the material remaining on the culture plate following the removal of the cells from the plate. PACE4 bound to the extracellular fraction was selectively dislodged by heparin into the culture medium. Heparin has no inhibitory activity against PACE4. Similarly, PC6A is also able to bind to heparin, whereas soluble furin does not. In human placenta, PACE4 is mainly present in syncytiotrophoblasts and can be released by heparin. These results suggest that PACE4 and PC6 are unique SPC family proteases that anchor heparan sulfate proteoglycans at the ECM. The interaction between PACE4 and heparan sulfate proteoglycans might play an important role in the delicate spatiotemporal regulation of TGFbeta-related factors' biological activity.

The matrix metalloproteinase 9 (mmp-9) hemopexin domain is a novel gelatin binding domain and acts as an antagonist

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 x 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.

Cytotoxic cell granule-mediated apoptosis. Characterization of the macromolecular complex of granzyme B with serglycin

We have recently shown that the physiological mediator of granule-mediated apoptosis is a macromolecular complex of granzymes and perforin complexed with the chondroitin-sulfate proteoglycan, serglycin (Metkar, S. S., Wang, B., Aguilar-Santelises, M., Raja, S. M., Uhlin-Hansen, L., Podack, E., Trapani, J. A., and Froelich, C. J. (2002) Immunity 16, 417-428). We now report our biophysical studies establishing the nature of granzyme B-serglycin (GrB.SG) complex. Dynamic laser light scattering studies establish that SG has a hydrodynamic radius of approximately 140 +/- 23 nm, comparable to some viral particles. Agarose mobility shift gels and surface plasmon resonance (SPR), show that SG binds tightly to GrB and has the capacity to hold 30-60 GrB molecules. SPR studies also indicate equivalent binding affinities (K(d) approximately 0.8 microm), under acidic (granule pH) and neutral isotonic conditions (extra-cytoplasmic pH), for GrB.SG interaction. Finally, characterization of GrB.SG interactions within granules revealed complexes of two distinct molecular sizes, one held approximately 4-8 molecules of GrB, whereas the other contained as many as 32 molecules of GrB or other granule proteins. These studies provide a firm biophysical basis for our earlier reported observations that the proapoptotic granzyme is exocytosed predominantly as a macromolecular complex with SG.

Cell surface targeting of pregnancy-associated plasma protein A proteolytic activity. Reversible adhesion is mediated by two neighboring short consensus repeats

The activities of insulin-like growth factor (IGF)-I and -II are regulated by IGF-binding proteins (IGFBPs). Cleavage of IGFBP-4 by the metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) causes release of bound IGF and has been established in several biological systems including the human reproductive system. Using flow cytometry, we first demonstrate that PAPP-A reversibly binds to the cell surface of several cell types analyzed. Heparin and heparan sulfate, but not dermatan or chondroitin sulfate, effectively compete for PAPP-A surface binding, and because incubation of cells with heparinase abrogated PAPP-A adhesion, binding is probably mediated by a cell surface heparan sulfate proteoglycan. Furthermore, the proteolytic activity of PAPP-A is preserved while bound to cells, suggesting that adhesion functions to target its activity to the vicinity of the IGF receptor, decreasing the probability that released IGF is captured by another IGFBP molecule before receptor binding. This mechanism potentially functions in both autocrine and paracrine regulation, as PAPP-A need not be synthesized in a cell to which it adheres. A truncated PAPP-A variant without the five short consensus repeats in the C-terminal third of the 1547-residue PAPP-A subunit, lacked surface binding. We also show that PAPP-A2, a recently discovered IGFBP-5 proteinase with homology to PAPP-A, does not bind cells. This finding allowed further mapping of the PAPP-A adhesion site to short consensus repeat modules 3 and 4 by the expression and analysis of nine PAPP-A/PAPP-A2 chimeras. Interestingly, the proteolytically inactive, disulfide-bound complex of PAPP-A and the proform of eosinophil major basic protein (proMBP), PAPP-A.proMBP, shows only weak surface binding, probably because the adhesion site of PAPP-A is occupied by heparan sulfate, known to be covalently bound to proMBP. This hypothesis was further substantiated by demonstrating that heparinase treatment of PAPP-A.proMBP restores surface binding. We finally propose a model in which IGF bioactivity is regulated by reversible cell surface binding of PAPP-A, which in turn is regulated by proMBP.

Matrix metalloproteinases in tumor-host cell communication

The microenvironment or stroma immediately surrounding tumor cells consists of a three-dimensional extracellular matrix (ECM) and stromal cells such as fibroblasts and inflammatory cells. The matrix metalloproteinases (MMPs) constitute a family of over 24 members, which collectively are capable of degrading virtually the entire ECM. Strict regulation of MMP expression is critical in order to maintain proper ECM homeostasis, but in disease states such as cancer there is often a high level of MMP activity at the tumor-stroma interface. Several studies have documented the importance of MMP-mediated ECM destruction in the successful dissemination of several tumor types, but it has become increasingly clear that they are also involved in earlier stages of tumorigenesis. MMPs are implicated in a wide variety of roles that can assist tumor initiation, growth, migration, angiogenesis, the selection of apoptosis-resistant subpopulations, and in invasion and metastasis. Interestingly, the factors responsible for many of these effects are derived from the cell surfaces of the tumor or stromal cells or are embedded in the ECM. Therefore, the MMPs can no longer be thought of solely as ECM destructionists, but as part of an elegant communication system through which the tumor interacts with the stroma.

Matrilysin shedding of syndecan-1 regulates chemokine mobilization and transepithelial efflux of neutrophils in acute lung injury

The influx of inflammatory cells to sites of injury is largely directed by signals from the epithelium, but how these cells form chemotactic gradients is not known. In matrilysin null mice, neutrophils remained confined in the interstitium of injured lungs and did not advance into the alveolar space. Impaired transepithelial migration was accompanied by a lack of both shed syndecan-1, a heparan sulfate proteoglycan, and KC, a CXC chemokine, in the alveolar fluid. KC was bound to shed syndecan-1, and it was not detected in the lavage of syndecan-1 null mice. In vitro, matrilysin cleaved syndecan-1 from the surface of cells. Thus, matrilysin-mediated shedding of syndecan-1/KC complexes from the mucosal surface directs and confines neutrophil influx to sites of injury.

Involvement of the mural thrombus as a site of protease release and activation in human aortic aneurysms

Acquired abdominal aortic aneurysms are usually associated with a mural thrombus through which blood continues to flow. Some early data suggest that aneurysmal evolution correlates with the biological activity of the thrombus. Our hypothesis was therefore that the thrombus could adsorb blood components and store, release, and participate in the activation of proteases involved in aneurysmal evolution. For this purpose, we have explored both the metalloproteinase and fibrinolytic systems in the thrombus and the wall of human aneurysms. We have first investigated blood clot formation and lysis in vitro. Spontaneous clotting induces a release of promatrix metalloproteinase (pro-MMP)-9 into the serum that was fourfold higher than in paired control plasma (P < 0.001). Fibrinolysis progressively released more MMP-9 in a time-dependent manner (P < 0.01). After selective isolation, we demonstrated that polymorphonuclear leukocytes are the main source of MMP-9 release during clot formation. Protease content was then analyzed in 35 mural thrombi and walls of human abdominal aortic aneurysms sampled during surgical repair. In 15 aneurysms, the liquid phase at the interface between the thrombus and the wall was sampled separately. Both thrombus and wall contained MMP-2 and MMP-9 but the ratio MMP-9/MMP-2 was higher in the thrombus than in the wall. The liquid interface also contained active MMP-9. Immunohistochemistry of the thrombus confirmed these findings, showing the presence of polymorphonuclear leukocytes at the luminal pole of the thrombus, co-localizing with MMP-9 storage. In contrast, MMP-3 and MMP-7 were only present in the aneurysmal wall. Plasminogen was present in the mural thrombus but plasmin activity was present in both thrombus and wall. In the liquid interface, plasmin-alpha(2)-anti-plasmin complexes were detected demonstrating in vivo the activation of plasminogen. In contrast, u-PA and t-PA were detectable only in the wall, suggesting that plasminogen present in the thrombus could be activated by factors secreted by the arterial wall. This was demonstrated in vitro, in which co-incubation of thrombus and wall extracts generated plasmin in the presence of a fibrin matrix and activated MMPs. In conclusion, our study strongly suggests that the mural thrombus, by trapping polymorphonuclear leukocytes and adsorbing plasma components could act as a source of proteases in aneurysms that may play a critical role in enlargement and rupture.

Matrix metalloproteinase 9 (MMP-9/gelatinase B) proteolytically cleaves ICAM-1 and participates in tumor cell resistance to natural killer cell-mediated cytotoxicity

Shedding of intercellular adhesion molecule 1 (ICAM-1) is believed to play a role in tumor cell resistance to cell-mediated cytotoxicity. However, the mechanism whereby ICAM-1 is shed from the surface of tumor cells remains unclear. In this study, we have addressed the possibility that matrix metalloproteinases are implicated in ICAM-1 shedding. Our observations suggest a functional relationship between ICAM-1 and matrix metalloproteinase 9 (MMP-9) whereby ICAM-1 provides a cell surface docking mechanism for proMMP-9, which, upon activation, proteolytically cleaves the extracellular domain of ICAM-1 leading to its release from the cell surface. MMP-9-dependent shedding of ICAM-1 is found to augment tumor cell resistance to natural killer (NK) cell-mediated cytotoxicity. Taken together, our observations propose a mechanism for ICAM-1 shedding from the cell surface and provide support for MMP involvement in tumor cell evasion of immune surveillance.

Matrix-directed regulation of pericellular proteolysis and tumor progression

The microenvironment of cancer cells, composed of extracellular matrix (ECM) macromolecules, plays a pivotal function in tumor progression. ECM preexisting modules or cryptic sites revealed by partial enzymatic hydrolysis positively or negatively regulate matrix metalloproteinase (MMP) expression and activation, further influencing matrix invasion by cancer cells. Pericellular activation of gelatinase A (MMP-2) proceeds via the formation of a complex involving its inhibitor, TIMP-2, its activator(s), MT-MMPs and alphavbeta3 integrin forming a docking system. This proteinase has been invariably linked to cancer cell invasive potential and is often predictive of a poor survival. MMP-2 degrades most ECM macromolecules and appears to act as a main 'decryptase'. ECM modulation of MMP-2 activation pathway thus influences angiogenesis and tumor growth. For instance the noncollagenous domain of alpha3 chain of type IV collagen, through alphavbeta3 integrin binding, inhibits both MT1-MMP and alphavbeta3 integrin expression from melanoma cells and empedes cell migration and proliferation. At the opposite, a particular module in elastin (VGVAPG) with type VIII beta turn conformation stimulates MT1-MMP and proMMP-2 activation through binding to S-gal elastin receptor, and increases the matrix invasive capacity of several cancer cell lines and endothelial cells. Endocytosis emerges as a main mechanism controlling MMP-2, and also other MMPs; it proceeds via the formation of a MMP-thrombospondin(s) complex further recognized by the LRP scavenger receptor. ECM undergoes conspicuous variations with aging linked to alterations of tissue organization and post-translational modifications of matrix constituents that modify cell-matrix interactions and MMP-2 activation pathway.

The integrin alpha(v)beta8 mediates epithelial homeostasis through MT1-MMP-dependent activation of TGF-beta1

Integrins, matrix metalloproteases (MMPs), and the cytokine TGF-beta have each been implicated in homeostatic cell behaviors such as cell growth and matrix remodeling. TGF-beta exists mainly in a latent state, and a major point of homeostatic control is the activation of TGF-beta. Because the latent domain of TGF-beta1 possesses an integrin binding motif (RGD), integrins have the potential to sequester latent TGF-beta (SLC) to the cell surface where TGF-beta activation could be locally controlled. Here, we show that SLC binds to alpha(v)beta8, an integrin expressed by normal epithelial and neuronal cells in vivo. This binding results in the membrane type 1 (MT1)-MMP-dependent release of active TGF-beta, which leads to autocrine and paracrine effects on cell growth and matrix production. These data elucidate a novel mechanism of cellular homeostasis achieved through the coordination of the activities of members of three major gene families involved in cell-matrix interactions.

Heparin and non-heparin-like dextrans differentially modulate endothelial cell proliferation: in vitro evaluation with soluble and crosslinked polysaccharide matrices

Proliferation of endothelial cells (ECs) is a cellular step of particular importance for implanted cardiovascular biomaterials. Heparin and some synthetic water-soluble non-anticoagulant polysaccharides derived from dextran and bearing anionic carboxymethyl and hydrophobic benzylamine groups were first investigated for their effects on EC proliferation in vitro. The results assessed by cell counting, 3H-thymidine uptake, and flow cytometry analysis, showed that the derivatized dextran-bearing hydrophobic groups stimulated the EC growth in the presence of serum, whereas native dextran or dextran-bearing anionic carboxymethyl groups were inactive and heparin was slightly inhibitory. Then, we showed that the derivatized dextran enhanced EC proliferation by potentiation of the mitogenic activities of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2), two potent EC growth factors. In the presence of 2 nM of derivatized dextran, a 3-fold and 13-fold increase of 3H-thymidine uptake was obtained with VEGF and FGF-2, respectively. Finally, proliferation of ECs was investigated on crosslinked gels made of polysaccharides. It is of interest that EC proliferation was higher on gels containing the derivatized dextran than on plain hydrogels, and heparinized gels inhibited cell proliferation. From the obtained results, we propose that the synthetic non-heparin-like dextran may be of interest as a coating for the endothelialization of cardiovascular biomaterials.

CD44 anchors the assembly of matrilysin/MMP-7 with heparin-binding epidermal growth factor precursor and ErbB4 and regulates female reproductive organ remodeling

CD44 is a facultative proteoglycan implicated in cell adhesion and trafficking, as well as in tumor survival and progression. We demonstrate here that CD44 heparan sulfate proteoglycan (CD44HSPG) recruits proteolytically active matrix metalloproteinase 7 (matrilysin, MMP-7) and heparin-binding epidermal growth factor precursor (pro-HB-EGF) to form a complex on the surface of tumor cell lines, postpartum uterine and lactating mammary gland epithelium, and uterine smooth muscle. The HB-EGF precursor within this complex is processed by MMP-7, and the resulting mature HB-EGF engages and activates its receptor, ErbB4, leading to, among other events, cell survival. In CD44(-/-) mice, postpartum uterine involution is accelerated and maintenance of lactation is impaired. In both uterine and mammary epithelia of these mice, MMP-7 localization is altered and pro-HB-EGF processing as well as ErbB4 activation are decreased. Our observations provide a mechanism for the assembly and function of a cell surface complex composed of CD44HSPG, MMP 7, HB-EGF, and ErbB4 that may play an important role in the regulation of physiological tissue remodeling.

Matrix metalloproteinases in lung biology

Despite much information on their catalytic properties and gene regulation, we actually know very little of what matrix metalloproteinases (MMPs) do in tissues. The catalytic activity of these enzymes has been implicated to function in normal lung biology by participating in branching morphogenesis, homeostasis, and repair, among other events. Overexpression of MMPs, however, has also been blamed for much of the tissue destruction associated with lung inflammation and disease. Beyond their role in the turnover and degradation of extracellular matrix proteins, MMPs also process, activate, and deactivate a variety of soluble factors, and seldom is it readily apparent by presence alone if a specific proteinase in an inflammatory setting is contributing to a reparative or disease process. An important goal of MMP research will be to identify the actual substrates upon which specific enzymes act. This information, in turn, will lead to a clearer understanding of how these extracellular proteinases function in lung development, repair, and disease.

Ventilator-induced lung injury upregulates and activates gelatinases and EMMPRIN: attenuation by the synthetic matrix metalloproteinase inhibitor, Prinomastat (AG3340)

Mechanical ventilation has become an indispensable therapeutic modality for patients with respiratory failure. However, a serious potential complication of MV is the newly recognized ventilator-induced acute lung injury. There is strong evidence suggesting that matrix metalloproteinases (MMPs) play an important role in the development of acute lung injury. Another factor to be considered is extracellular matrix metalloproteinase inducer (EMMPRIN). EMMPRIN is responsible for inducing fibroblasts to produce/secrete MMPs. In this report we sought to determine: (1) the role played by MMPs and EMMPRIN in the development of ventilator-induced lung injury (VILI) in an in vivo rat model of high volume ventilation; and (2) whether the synthetic MMP inhibitor Prinomastat (AG3340) could prevent this type of lung injury. We have demonstrated that high volume ventilation caused acute lung injury. This was accompanied by an upregulation of gelatinase A, gelatinase B, MT1-MMP, and EMMPRIN mRNA demonstrated by in situ hybridization. Pretreatment with the MMP inhibitor Prinomastat attenuated the lung injury caused by high volume ventilation. Our results suggest that MMPs play an important role in the development of VILI in rat lungs and that the MMP-inhibitor Prinomastat is effective in attenuating this type of lung injury.

Structural Analysis of the α2 Integrin I Domain/Procollagenase-1 (Matrix Metalloproteinase-1) Interaction

Previous studies have established that ligation of keratinocyte alpha(2)beta(1) integrin by type I collagen induces expression of matrix metalloproteinase-1 (MMP-1) and that MMP-1 activity is required for the alpha(2)beta(1) integrin-dependent migration of primary keratinocytes across collagenous matrices. We now present evidence that MMP-1 binds the alpha(2)beta(1) integrin via the I domain of the alpha(2) integrin subunit. Using an enzyme-linked immunosorbent assay with purified human MMP-1 and recombinant alpha(2) integrin I domain, we showed that the alpha(2) integrin I domain specifically bound in a divalent cation-dependent manner to both the pro and active forms of MMP-1, but not to MMP-3 or MMP-13. Although both the I domain and MMP-1 bind divalent cations, MMP-1 bound, in a divalent cation-dependent manner, to alpha(2) integrin I domains containing metal ion-dependent adhesion sites motif mutations that prevent divalent cation binding to the I domain, demonstrating that the metal ion dependence is a function of MMP-1. Using a series of MMP-1-MMP-3 and MMP-1-MMP-13 chimeras, we determined that both the linker domain and the hemopexin-like domain of MMP-1 were required for optimal binding to the I domain. The alpha(2) integrin/MMP-1 interaction described here extends an emerging paradigm in matrix biology involving anchoring of proteinases to the cell surface to regulate their biological activities.

Pro-collagenase-1 (Matrix Metalloproteinase-1) Binds the α2β1 Integrin upon Release from Keratinocytes Migrating on Type I Collagen

In injured skin, collagenase-1 (matrix metalloproteinase-1 (MMP-1)) is induced in migrating keratinocytes. This site-specific expression is regulated by binding of the alpha(2)beta(1) integrin with dermal type I collagen, and the catalytic activity of MMP-1 is required for keratinocyte migration. Because of this functional association among substrate/ligand, receptor, and proteinase, we assessed whether the integrin also directs the compartmentalization of MMP-1 to its matrix target. Indeed, pro-MMP-1 co-localized to sites of alpha(2)beta(1) contacts in migrating keratinocytes. Furthermore, pro-MMP-1 co-immunoprecipitated with alpha(2)beta(1) from keratinocytes, and alpha(2)beta(1) co-immunoprecipitated with pro-MMP-1. No other MMPs bound alpha(2)beta(1), and no other integrins interacted with MMP-1. Pro-MMP-1 also provided a substrate for alpha(2)beta(1)-dependent adhesion of platelets. Complex formation on keratinocytes was most efficient on native type I collagen and reduced or ablated on denatured or cleaved collagen. Competition studies suggested that the alpha(2) I domain interacts with the linker and hemopexin domains of pro-MMP-1, not with the pro-domain. These data indicate that the interaction of pro-MMP-1 with alpha(2)beta(1) confines this proteinase to points of cell contact with collagen and that the ternary complex of integrin, enzyme, and substrate function together to drive and regulate keratinocyte migration.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in human fetal testis and ovary

Matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) are major regulators of tissue remodelling of the extracellular matrix (ECM) and may also be involved in the control of growth factor availability. We have investigated their production and localization in the developing human gonad during mid-gestation using zymographic techniques and immunohistochemistry. The secretion of MMP-2, MMP-9 and all four TIMP was demonstrated from both testis and ovary, with the predominant gelatinase produced by both being MMP-2. In the testis, MMP-1, MMP-2, MMP-9 and all TIMP family members were localized to the interstitium and to varying degrees within the tubules. MMP-9 and TIMP-4 were abundant in both Sertoli cells and gonocytes and MMP-1 and TIMP-1 were localized in particular to Sertoli cells. In the ovary, all TIMP and MMP-1, MMP-2 and MMP-9 were localized to the oogonium/oocyte cytoplasm with varying intensities and MMP-1, TIMP-2 and TIMP-3 were also detected in the ovarian stroma. This study demonstrates that MMP-1, MMP-2, MMP-9 and all TIMP family members are secreted by the developing ovary and testis and are localized to specific cell and tissue sites. MMP and TIMP are likely to play a role in ECM remodelling during gonadal development and also in the cell and matrix interactions that control a range of cellular functions.

Heparin-Enhanced Zymographic Detection of Matrilysin and Collagenases

Unlike the gelatinases (MMP-2 and -9), matrilysin (MMP-7) and collagenases (MMP-1 and -13) are difficult to detect at low levels in conventional casein or gelatin zymography. In this report, heparin was used to enhance the zymographic assays for MMP-7, -1, and -13. With the addition of heparin to the enzyme sample, MMP-7 can be detected at a level of 30 pg in transferrin zymography and MMP-1 and -13 can be detected at a level of 0.2 ng in gelatin zymography. Carboxymethylated transferrin is used instead of casein as a substrate for assaying rat MMP-7. This substrate does not require a prerun step or substrate cross-linking to give uniform staining and clear band formation. It is necessary for heparin to run to the same region of the gel as the enzyme to produce its enhancing effect. For MMP-7 movement of heparin and enzyme is almost equal; for the collagenases it is necessary to add heparin to each well after the electrophoretic run is underway. Possible mechanisms of activity enhancement are discussed.

Heparan sulfate proteoglycans in invasion and metastasis

Because heparan sulfate proteoglycans mediate cell adhesion and control the activities of numerous growth and motility factors, they play a critical role in regulating the metastatic behavior of tumor cells. Due to their utilitarian nature, heparan sulfate proteoglycans may at times act as inhibitors of cell invasion and at other times as promoters of cell invasion, with their function being determined by their location (cell surface or extracellular matrix), the heparin-binding molecules they associate with, the presence of modifying enzymes (proteases, heparanases) and the precise structural characteristics of the proteoglycan. Also, the tissue type and pathophysiological state of the tumor influence proteogylcan function. This review summarizes our current knowledge of the role heparan sulfate proteoglycans play in regulating tumor cell metastasis, proposes mechanisms of how these molecules function and examines the potential for discovery of new therapeutic approaches designed to block metastatic cancer.

Expression of heparanase in oral cancer cell lines and oral cancer tissues

In the process of metastasis, cancer cells secrete several enzymes which degrade extracellular matrices (ECMs) and basement membranes (BMs) of blood vessels. One of them, heparanase, has been reported to be an important enzyme when metastatic cancer cells invade blood vessels. The enzyme cleaves heparan sulfate (HS), a main component of ECM and BM. In the present study, HS-degrading ability of several human oral cancer cell lines (HSC2, HSC3, HSC4, Ca9-22, NA, ACC3 and Ab-J) and tissues derived from human oral squamous cell carcinomas (both metastatic and non-metastatic) were investigated by measuring heparanase activities and levels of heparanase mRNA by a quantitative reverse transcriptase-polymerase chain reaction. The catalytic activities and the mRNA levels of heparanase showed a good agreement. Clinical demonstration of cancer metastasis generally correlated with high levels of heparanase activity and its mRNA. The results suggest that heparanase activity and its mRNA level are good diagnostic parameters for evaluating the metastatic properties of human oral cancer cells.

How matrix metalloproteinases regulate cell behavior

The matrix metalloproteinases (MMPs) constitute a multigene family of over 25 secreted and cell surface enzymes that process or degrade numerous pericellular substrates. Their targets include other proteinases, proteinase inhibitors, clotting factors, chemotactic molecules, latent growth factors, growth factor-binding proteins, cell surface receptors, cell-cell adhesion molecules, and virtually all structural extracellular matrix proteins. Thus MMPs are able to regulate many biologic processes and are closely regulated themselves. We review recent advances that help to explain how MMPs work, how they are controlled, and how they influence biologic behavior. These advances shed light on how the structure and function of the MMPs are related and on how their transcription, secretion, activation, inhibition, localization, and clearance are controlled. MMPs participate in numerous normal and abnormal processes, and there are new insights into the key substrates and mechanisms responsible for regulating some of these processes in vivo. Our knowledge in the field of MMP biology is rapidly expanding, yet we still do not fully understand how these enzymes regulate most processes of development, homeostasis, and disease.

Critical appraisal of the use of matrix metalloproteinase inhibitors in cancer treatment

Experimental studies performed prior to 1990 led to the widely held belief that matrix metalloproteinases (MMPs) produced by cancer cells are of critical importance in tumor invasion and metastasis. Based on this evidence, the pharmaceutical industry produced several well tolerated, orally active MMP inhibitors (MMPIs) which demonstrated efficacy in mouse cancer models. Phase III clinical trials initiated in 1997-98 using marimastat, prinomastat (AG3340), and BAY 12-9566 alone or in combination with standard chemotherapy in patients with advanced cancers (lung, prostate, pancreas, brain, GI tract) have recently been reported; no clinical efficacy was demonstrated. Bayer and Agouron have discontinued their ongoing Phase III drug trials of MMPIs in advanced cancer. In retrospect, the failure of MMPIs to alter disease progression in metastatic cancer might have been anticipated since MMPs appear to be important in early aspects of cancer progression (local invasion and micrometastasis) and may no longer be required once metastases have been established. Our understanding of MMP pathophysiology in cancer has expanded considerably in the past 10 years. Current views indicate that: (1) most MMPs in tumors are made by stromal cells, not carcinoma cells; (2) cancer cells induce stromal cells to synthesize MMPs using extracellular matrix metalloproteinase inducer (EMMPRIN) and cytokine stimulatory mechanisms; and (3) MMPs promote cell migration and the release of growth factors sequestered in the extracellular matrix. MMPs have a dual function in tumor angiogenesis: MMP-2 and MT1-MMP are required in breaking down basement membrane barriers in the early stage of angiogenesis, while other MMPs are involved in the generation of an angiogenic inhibitor, angiostatin. In spite of considerable recent progress in identifying multiple roles of MMPs in disease, our understanding of MMP function in cancer is far from complete (see Table 1). Based on accumulated data, it is recommended that future MMPI trials focus on: (1) patients with early stage cancer; (2) the use of MMPIs along with chemotherapy; (3) the measurement of MMPs in tumor tissue and blood as a means of identifying patients who are more likely to respond to MMPI therapy; and (4) identification of biomarkers that reflect activation or inhibition of MMPs in vivo.

Matrix metalloproteinases in tumor invasion and metastasis

Extensive work on the mechanisms of tumor invasion and metastasis has identified matrix metalloproteinases (MMPs) as key players in the events that underlie tumor dissemination. Studies using natural and synthetic MMP inhibitors, as well as tumor cells transfected with cDNAs encoding the MMPs characterized thus far have provided compelling evidence that MMP activity can induce or enhance tumor survival, invasion and metastasis. Because of the ability of MMPs to degrade extracellular matrix (ECM) proteins, the principal mechanism whereby MMPs promote tumor development has been thought to be the proteolytic breakdown of tissue barriers to invasion and the associated facilitation of circulating tumor cell extravasation. However, recent evidence stemming from the use of novel experimental approaches indicates that MMPs do not play a major role in the process of extravasation itself. Rather, they appear to promote intravasation (the process of penetrating the circulation following invasion of blood vessels) and regulate the relationship between tumor cells and host tissue stroma subsequent to extravasation. In addition, the discoveries that a growing number of proteolytically active MMPs may localize to the cell surface in association with adhesion receptors, and that MMP substrates include latent cytokines and growth factors, provide a new conceptual framework for the mechanisms whereby MMPs influence tumor behavior.

Characterization of METH-1/ADAMTS1 processing reveals two distinct active forms

METH-1/ADAMTS1 is a member of a newly described family of genes that contain metalloprotease, disintegrin, and thrombospondin-like motifs. We have recently shown that METH-1 protein is a potent inhibitor of angiogenesis. Here, we demonstrate that secreted human pro-METH-1 is processed in two consecutive steps to release both p87 and p65 active forms. The p87 form lacks the N-terminal prodomain and p65 results from an additional processing event in the C-terminal end. Generation of p87 was blocked with specific inhibitors of furin, and incubation of pro-METH-1 with purified furin released the p87 fragment but not p65. Generation of p65 required preformation of p87 and was suppressed by inhibitors of matrix metalloproteases. We demonstrate that matrix metalloproteases 2, 8, and 15 were able to release p65 when p87 was used as substrate. This second processing step removes two thrombospondin repeats from the carboxyl-terminal end of p87-METH-1 and alters the affinity of the protein to heparin and endothelial cultures. Furthermore, this deletion was associated with a reduced activity upon suppression of endothelial cell proliferation. We hypothesize that METH-1 processing is relevant for the modulation of the anti-angiogenic properties displayed by the protein.

TIMP-3 binds to sulfated glycosaminoglycans of the extracellular matrix

Of the four known tissue inhibitors of metalloproteinases (TIMPs), TIMP-3 is distinguished by its tighter binding to the extracellular matrix. The present results show that glycosaminoglycans such as heparin, heparan sulfate, chondroitin sulfates A, B, and C, and sulfated compounds such as suramin and pentosan efficiently extract TIMP-3 from the postpartum rat uterus. Enzymatic treatment by heparinase III or chondroitinase ABC also releases TIMP-3, but neither one alone gives complete release. Confocal microscopy shows colocalization of heparan sulfate and TIMP-3 in the endometrium subjacent to the lumen of the uterus. Immunostaining of TIMP-3 is lost upon digestion of tissue sections with heparinase III and chondroitinase ABC. The N-terminal domain of human TIMP-3 was expressed and found to bind to heparin with affinity similar to that of full-length mouse TIMP-3. The A and B beta-strands of the N-terminal domain of TIMP-3 contain two potential heparin-binding sequences rich in lysine and arginine; these strands should form a double track on the outer surface of TIMP-3. Synthetic peptides corresponding to segments of these two strands compete for heparin in the DNase II binding assay. TIMP-3 binding may be important for the cellular regulation of activity of the matrix metalloproteinases.