Expression of human recombinant 72 kDa gelatinase and tissue inhibitor of metalloproteinase-2 (TIMP-2): characterization of complex and free enzyme

Tissue Inhibitor of Metalloprotease-2 (TIMP-2): Bioprocess Development, Physicochemical, Biochemical, and Biological Characterization of Highly Expressed Recombinant Protein

Tissue inhibitor of metalloprotease-2 (TIMP-2) is a secreted 21 kDa multifunctional protein first described as an endogenous inhibitor of matrix metalloproteinases (MMPs) that prevents breakdown of the extracellular matrix often observed in chronic diseases. TIMP-2 diminishes the level of growth factor-mediated cell proliferation in vitro, as well as neoangiogenesis and tumor growth in vivo independent of its MMP inhibitory activity. These physiological properties make TIMP-2 an excellent candidate for further preclinical development as a biologic therapy of cancer. Here we present a straightforward bioprocessing methodology that yields >35 mg/L recombinant human TIMP-2 6XHis-tagged protein (rhTIMP-2) from suspension cultures of HEK-293-F cells. Enhanced rhTIMP-2-6XHis yields were achieved by optimization of both TIMP-2 cDNA codon sequence and cell culture conditions. Using a two-step chromatographic process, we achieved >95% purity with minimal processing losses. Purified rhTIMP-2-6XHis was free of mouse antigen contamination. Circular dichroism spectroscopy indicated a well-folded rhTIMP-2-6XHis that is highly stable and refractory to pH changes. Two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance of full length rhTIMP-2-6XHis also indicated a monodisperse, well-folded protein preparation. Purified rhTIMP-2-6XHis inhibited MMP-2 enzymatic activity in a dose-dependent fashion with an IC50 of ∼1.4 nM. Pretreatment of A549 lung cancer and JygMC(A) triple-negative breast cancer cells with rhTIMP-2-6XHis in low-nanomolar amounts inhibited EGF-induced proliferation to basal (unstimulated) levels. This study therefore not only offers a robust bioprocess methodology for rhTIMP-2 production but also characterizes critical physicochemical and biological attributes that are useful for monitoring quality control of the production process.

Matrix Metalloproteinases, Vascular Remodeling, and Vascular Disease

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that degrade various proteins in the extracellular matrix (ECM). Typically, MMPs have a propeptide sequence, a catalytic metalloproteinase domain with catalytic zinc, a hinge region or linker peptide, and a hemopexin domain. MMPs are commonly classified on the basis of their substrates and the organization of their structural domains into collagenases, gelatinases, stromelysins, matrilysins, membrane-type (MT)-MMPs, and other MMPs. MMPs are secreted by many cells including fibroblasts, vascular smooth muscle (VSM), and leukocytes. MMPs are regulated at the level of mRNA expression and by activation through removal of the propeptide domain from their latent zymogen form. MMPs are often secreted in an inactive proMMP form, which is cleaved to the active form by various proteinases including other MMPs. MMPs degrade various protein substrates in ECM including collagen and elastin. MMPs could also influence endothelial cell function as well as VSM cell migration, proliferation, Ca²⁺ signaling, and contraction. MMPs play a role in vascular tissue remodeling during various biological processes such as angiogenesis, embryogenesis, morphogenesis, and wound repair. Alterations in specific MMPs could influence arterial remodeling and lead to various pathological disorders such as hypertension, preeclampsia, atherosclerosis, aneurysm formation, as well as excessive venous dilation and lower extremity venous disease. MMPs are often regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP ratio often determines the extent of ECM protein degradation and tissue remodeling. MMPs may serve as biomarkers and potential therapeutic targets for certain vascular disorders.

Decreased homodimerization and increased TIMP-1 complexation of uteroplacental and uterine arterial matrix metalloproteinase-9 during hypertension-in-pregnancy

Preeclampsia is a complication of pregnancy manifested as hypertension-in-pregnancy (HTN-Preg) and often intrauterine growth restriction (IUGR). Placental ischemia could be an initiating event, but the molecular mechanisms are unclear. To test the hypothesis that dimerization of matrix metalloproteinases (MMPs) plays a role in HTN-Preg and IUGR, the levels/activity of MMP-9, tissue inhibitor of metalloproteinase (TIMP-1), and their dimerization forms were measured in the placenta, uterus, and uterine artery of normal pregnant (Preg) rats and a rat model of reduced uteroplacental perfusion pressure (RUPP). Consistent with our previous report, blood pressure (BP) was higher, pup weight was lower, and gelatin zymography showed different gelatinolytic activity for pro-MMP-9, MMP-9, pro-MMP-2 and MMP-2 in RUPP vs Preg rats. Careful examination of the zymograms showed additional bands at 200 and 135kDa. Western blots with MMP-9 antibody suggested that the 200kDa band was a MMP-9 homodimer. Western blots with TIMP-1 antibody as well as reverse zymography suggested that the 135kDa band was a MMP-9/TIMP-1 complex. The protein levels and gelatinase activity of MMP-9 homodimer were decreased while MMP-9/TIMP-1 complex was increased in placenta, uterus and uterine artery of RUPP vs Preg rats. The epidermal growth factor (EGF) receptor blocker erlotinib and protein kinase C (PKC) inhibitor bisindolylmaleimide decreased MMP-9 homodimer and increased MMP-9/TIMP-1 complex in placenta, uterus and uterine artery of Preg rats. EGF and the PKC activator phorbol-12,13-dibutyrate (PDBu) reversed the decreases in MMP-9 homodimer and the increases in MMP-9/TIMP-1 complex in tissues of RUPP rats. Thus, the increased BP and decreased pup weight in placental ischemia model of HTN-Preg are associated with a decrease in MMP-9 homodimer and an increase in MMP-9/TIMP-1 complex in placenta, uterus, and uterine artery, which together would cause a net decrease in MMP-9 activity and reduce uteroplacental and vascular remodeling in the setting of HTN-Preg and IUGR. Enhancing EGFR/PKC signaling may reverse the MMP-9 unfavorable dimerization patterns and thereby promote uteroplacental and vascular remodeling in preeclampsia.

Biochemical and Biological Attributes of Matrix Metalloproteinases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that are involved in the degradation of various proteins in the extracellular matrix (ECM). Typically, MMPs have a propeptide sequence, a catalytic metalloproteinase domain with catalytic zinc, a hinge region or linker peptide, and a hemopexin domain. MMPs are commonly classified on the basis of their substrates and the organization of their structural domains into collagenases, gelatinases, stromelysins, matrilysins, membrane-type (MT)-MMPs, and other MMPs. MMPs are secreted by many cells including fibroblasts, vascular smooth muscle (VSM), and leukocytes. MMPs are regulated at the level of mRNA expression and by activation of their latent zymogen form. MMPs are often secreted as inactive pro-MMP form which is cleaved to the active form by various proteinases including other MMPs. MMPs cause degradation of ECM proteins such as collagen and elastin, but could influence endothelial cell function as well as VSM cell migration, proliferation, Ca²⁺ signaling, and contraction. MMPs play a role in tissue remodeling during various physiological processes such as angiogenesis, embryogenesis, morphogenesis, and wound repair, as well as in pathological conditions such as myocardial infarction, fibrotic disorders, osteoarthritis, and cancer. Increases in specific MMPs could play a role in arterial remodeling, aneurysm formation, venous dilation, and lower extremity venous disorders. MMPs also play a major role in leukocyte infiltration and tissue inflammation. MMPs have been detected in cancer, and elevated MMP levels have been associated with tumor progression and invasiveness. MMPs can be regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP ratio often determines the extent of ECM protein degradation and tissue remodeling. MMPs have been proposed as biomarkers for numerous pathological conditions and are being examined as potential therapeutic targets in various cardiovascular and musculoskeletal disorders as well as cancer.

Identification and characterization of the precursor of chicken matrix metalloprotease 2 (pro-MMP-2) in hen egg

Using zymography and mass spectrometry, we identified for the first time the precursor of chicken matrix metalloprotease 2 (pro-MMP-2) as a complex with TIMP-2 (tissue inhibitor of metalloproteinases) in egg white and yolk. Real-time polymerase chain reaction confirmed that MMP-2 and its inhibitors TIMP-2 and TIMP-3 were expressed all along the oviduct and in the liver of laying hens. We also demonstrated that the processing of pro-MMP-2 into mature MMP-2 by serine proteases does not occur in vivo, although purified pro-MMP-2 undergoes proteolytic maturation by these proteases in vitro. Moreover, the relative pro-MMP-2 activity assessed by gelatin zymography was shown to decrease in egg white during the storage of unfertilized or fertilized eggs. However, the mature form of 62 kDa MMP-2 could not be detected. The fact that MMP-2 is found as a proform in fresh eggs suggests that the activity of this metalloprotease is regulated under specific conditions during embryonic development.

The value and correlation between PRL-3 expression and matrix metalloproteinase activity and expression in human gliomas

Local invasion of tumor cells is characteristic of most human glioma invasions. It is associated with increased motility and a potential to degrade the extracellular matrix. Matrix metalloproteinases (MMPs) have been proved to be a main process in local invasion of brain tumor. PRL-3 is a new protein tyrosine phosphatase which would also degrade the extracellular matrix and has been proved to be expressed in liver metastases derived from colorectal cancer. In this study, we sought to investigate the expression of PRL-3 in glioma tissues and investigate the relationship between MMPs (MMP2, MMP9, membrane-type matrix metalloproteinase 1 [MT1-MMP]) activity and expression in gliomas. The modifications of in situ hybridization of mRNA phosphatase of regenerating liver-3 (PRL-3) methods are preformed in the study of paraffin-embedded slides. The immunohistochemistry and gelatin zymography are used to detect the expression of PRL-3 and activity of MMPs. The results show that PRL-3 mRNA and antibody of PRL-3 are detected in glioma tissues mainly in grades IV and III, only a little in grade II, but not in normal brain tissue and glioma grade I. MMP2 and MMP9 are observed mainly in glioma tissues of grades IV and III in activity and expression. MT1-MMP protein is located in glioma tissues and vessel endothelial cells. This is the first report of detecting PRL-3 expression in gliomas, especially in grades III and IV, which may play an important role in progression of gliomas. PRL-3, MMP2 and MT1-MMP cooperatively contribute to gliomas invasion. Intermediate MMP2 (MT1-MMP, TIMP-2, MMP2 trimeric complex) is detected in high grades of glioma tissues by gelatin zymography and may be a marker indicating latent malignance of gliomas.

Peripheral blood stem cell mobilization: the CXCR2 ligand GRObeta rapidly mobilizes hematopoietic stem cells with enhanced engraftment properties

Chemokines direct the movement of leukocytes, including hematopoietic stem and progenitor cells, and can mobilize hematopoietic cells from marrow to peripheral blood where they can be used for transplantation. In this review, we will discuss the stem cell mobilizing activities and mechanisms of action of GRObeta, a CXC chemokine ligand for the CXCR2 receptor. GRObeta rapidly mobilizes short- and long-term repopulating cells in mice and/or monkeys and synergistically enhances mobilization responses when combined with the widely used clinical mobilizer, granulocyte colony-stimulating factor (G-CSF). The hematopoietic graft mobilized by GRObeta contains significantly more CD34(neg), Sca-1+, c-kit+, lineage(neg) (SKL) cells than the graft mobilized by G-CSF. In mice, stem cells mobilized by GRObeta demonstrate a competitive advantage upon long-term repopulation analysis and restore neutrophil and platelet counts significantly faster than cells mobilized by G-CSF. Even greater advantage in repopulation and restoration of hematopoiesis are observed with stem cells mobilized by the combination of GRObeta and G-CSF. GRObeta-mobilized SKL cells demonstrate enhanced adherence to vascular cell adhesion molecule-1 and VCAM(pos) endothelial cells and home more efficiently to bone marrow in vivo. The marrow homing ability of GRObeta-mobilized cells is less dependent on the CXCR4/SDF-1 axis than cells mobilized by G-CSF. The mechanism of mobilization by GRObeta requires active matrix metalloproteinase-9 (MMP-9), which results from release of pro-MMP-9 from peripheral blood, and marrow neutrophils, which alters the stoichiometry between pro-MMP-9 and its inhibitor tissue inhibitor of metalloproteinase-1, resulting in MMP-9 activation. The efficacy and rapid action of GRObeta and lack of proinflammatory activity make it an attractive agent to supplement mobilization by G-CSF. In addition, GRObeta may also have clinical mobilizing efficacy on its own, reducing the overall time and costs associated with peripheral blood stem cell transplantation.

Intraplatelet signaling mechanisms of the priming effect of matrix metalloproteinase-2 on platelet aggregation

OBJECTIVE

Platelets contain and release some matrix metalloproteinases (MMPs), enzymes involved in the degradation of extracellular matrix, and one of these (MMP-2) exerts a proaggregatory effect. We explored the signal transduction mechanisms activated by MMP-2 in human blood platelets.

METHODS AND RESULTS

Recombinant, human MMP-2, added before stimulation with subthreshold doses of different agonists, potentiated platelet activation, calcium influx, IP3 formation, and pleckstrin phosphorylation. Wortmannin and LY29400, two PI3-K inhibitors, suppressed the potentiating effects of MMP-2 and preincubation with MMP-2 enhanced the thrombin-induced association of the p85alpha PI3-K subunit with the cytoskeleton and increased the phosphorylation of PKB. Protein tyrosine kinase inhibitors, MAP kinase inhibitors, PLA2 inhibitors, cyclooxygenase inhibitors and antagonists of the P2Y1 and P2Y12 receptors did not affect the potentiating activity of MMP-2 on platelets.

CONCLUSION

Our data show that MMP-2, at a concentration released by activated platelets, facilitates platelet activation acting at the level of a second messenger system common to different agonists and related to the activation of PI3-K. Platelet-released MMP-2 may contribute to platelet activation in vivo.

Breast cancer cells induce stromal fibroblasts to express MMP-9 via secretion of TNF-alpha and TGF-beta

We used 2D-cocultures employing fibroblasts of different genetic backgrounds and MCF10A-derived human breast epithelial cells of increasingly malignant potential to investigate tumor-stroma interactions in breast cancer and to identify possible signaling pathways involved. Tumor cells induced expression of matrix-metalloproteinase 9 (MMP-9) in fibroblasts in a pattern dependent on the degree of their malignancy. In-situ zymography localized the main gelatinolytic activity around stromal cells in cocultures and xenografted tumors. Use of Smad3 knockout fibroblasts, small molecule inhibitors, and neutralizing antibodies showed that MMP-9 expression was induced by tumor cell-derived TNF-alpha and TGF-beta, dependent on Smad-, Ras-, and PI3-kinase-signaling, and likewise modulated by subsequent HGF- and EGF-signaling. Together, our results indicate that MMP-9 levels in tumor fibroblasts are regulated by a complex tumor-stroma cross-talk, involving multiple ligands and cellular signaling pathways.

The effects of high glucose and atorvastatin on endothelial cell matrix production

BACKGROUND

Statins are known to enhance atherosclerotic plaque stability through influences on extracellular matrix homeostasis. Net matrix production reflects the relative balance of matrix production and degradation through enzymes such as matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitor of MMP (TIMPs). The effects of statins on endothelial cell production of these parameters following co-exposure with a proatherogenic stimulus such as high glucose are not known.

METHODS

Human endothelial cells were exposed for 72 h to 5 mm (control) or 25 mm (high) glucose +/- atorvastatin (1 micromol/l). Extracellular matrix homeostasis was assessed by measuring matrix metalloproteinase (MMP)-2 secretion, tissue inhibitor of MMP (TIMP)-1 and -2 secretion and net collagen IV production. Results were expressed as percentage +/- SEM of control values.

RESULTS

Exposure to high glucose increased cellular collagen IV expression to 190.1 +/- 11.7% (P < 0.0001) of control levels. No change in MMP-2 secretion (111.6 +/- 5.2%; P > 0.05) was observed but both TIMP-1 and TIMP-2 expression were increased to 136.3 +/- 6.4% and 144.0 +/- 27.5%, respectively (both P < 0.05). The presence of atorvastatin in high glucose conditions reduced collagen IV expression to 136.1 +/- 20.6%. This was paralleled by increased secretion of MMP-2 to 145.8 +/- 7.8% (P < 0.01), increased TIMP-2 expression to 208.0 +/- 21.3% (P < 0.005 compared with high glucose) but no change in TIMP-1 expression (155.1 +/- 14.6%) compared with high glucose alone. The presence of atorvastatin in control conditions did not affect levels of collagen IV expression (114.5 +/- 13.2%).

CONCLUSIONS

Endothelial cell exposure to high glucose was associated with a MMP/TIMP profile that increased extracellular matrix production which was attenuated by concurrent exposure to atorvastatin. Consequently, a mechanism by which the atherosclerotic plaque regression that is observed in patients taking these drugs has been demonstrated.

Identification, purification and partial characterization of tissue inhibitor of matrix metalloproteinase-2 in bovine pulmonary artery smooth muscle

Bovine pulmonary artery smooth muscle possesses the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) as revealed by Western immunoblot study of its cytosol fraction with bovine polyclonal TIMP-2 antibody. This potent polypeptide inhibitor of matrix metalloproteinases (MMPs) was purified to homogeneity from cytosol fraction of bovine pulmonary artery smooth muscle. This inhibitor was purified by ammonium sulfate precipitation followed by gelatin sepharose and lentil lectin sepharose affinity chromatography and continuous elution electrophoresis by Prep Cell Model 491 (Bio-Rad, USA). SDS-PAGE revealed that the inhibitor has an apparent molecular mass of 21 kDa and was confirmed as TIMP-2 by (i) Western immunoblot assay using bovine polyclonal TIMP-2 antibody; and also by (ii) amino terminal amino acid sequence analysis of the purified inhibitor is found to be identical with TIMP-2 obtained from other sources. The purified 21 kDa inhibitor was found to be active against matrix metalloproteinase-2 (MMP-2, 72 kDa gelatinase) and matrix metalloproteinase-9 (MMP-9, 92 kDa gelatinase), the ambient MMPs in the pulmonary artery smooth muscle. The inhibitor was also found to be sensitive to the activated 72 kDa gelatinase-TIMP-2 complex and also active human interstitial collagenase. By contrast, it was found to be insensitive to the serine proteases: trypsin and plasmin. The inhibitor was heat and acid resistant and it had the sensitivity to trypsin degradation and reduction-alkylation. Treatment of the inhibitor with hydrogen peroxide, superoxide generating system (hypoxanthine plus xanthine oxidase) and peroxynitrite inactivated the inhibitor.

Pro-MMP-9 activation by the MT1-MMP/MMP-2 axis and MMP-3: role of TIMP-2 and plasma membranes

MMP-9 (gelatinase B) is produced in a latent form (pro-MMP-9) that requires activation to achieve catalytic activity. Previously, we showed that MMP-2 (gelatinase A) is an activator of pro-MMP-9 in solution. However, in cultured cells pro-MMP-9 remains in a latent form even in the presence of MMP-2. Since pro-MMP-2 is activated on the cell surface by MT1-MMP in a process that requires TIMP-2, we investigated the role of the MT1-MMP/MMP-2 axis and TIMPs in mediating pro-MMP-9 activation. Full pro-MMP-9 activation was accomplished via a cascade of zymogen activation initiated by MT1-MMP and mediated by MMP-2 in a process that is tightly regulated by TIMPs. We show that TIMP-2 by regulating pro-MMP-2 activation can also act as a positive regulator of pro-MMP-9 activation. Also, activation of pro-MMP-9 by MMP-2 or MMP-3 was more efficient in the presence of purified plasma membrane fractions than activation in a soluble phase or in live cells, suggesting that concentration of pro-MMP-9 in the pericellular space may favor activation and catalytic competence.

Complex pattern of membrane type 1 matrix metalloproteinase shedding. Regulation by autocatalytic cells surface inactivation of active enzyme

Membrane type 1 matrix metalloproteinase (MT1-MMP) is a type I transmembrane MMP shown to play a critical role in normal development and in malignant processes. Emerging evidence indicates that MT1-MMP is regulated by a process of ectodomain shedding. Active MT1-MMP undergoes autocatalytic processing on the cell surface, leading to the formation of an inactive 44-kDa fragment and release of the entire catalytic domain. Analysis of the released MT1-MMP forms in various cell types revealed a complex pattern of shedding involving two major fragments of 50 and 18 kDa and two minor species of 56 and 31-35 kDa. Protease inhibitor studies and a catalytically inactive MT1-MMP mutant revealed both autocatalytic (18 kDa) and non-autocatalytic (56, 50, and 31-35 kDa) shedding mechanisms. Purification and sequencing of the 18-kDa fragment indicated that it extends from Tyr(112) to Ala(255). Structural and sequencing data indicate that shedding of the 18-kDa fragment is initiated at the Gly(284)-Gly(285) site, followed by cleavage between the conserved Ala(255) and Ile(256) residues near the conserved methionine turn, a structural feature of the catalytic domain of all MMPs. Consistently, a recombinant 18-kDa fragment had no catalytic activity and did not bind TIMP-2. Thus, autocatalytic shedding evolved as a specific mechanism to terminate MT1-MMP activity on the cell surface by disrupting enzyme integrity at a vital structural site. In contrast, functional data suggest that the non-autocatalytic shedding generates soluble active MT1-MMP species capable of binding TIMP-2. These studies suggest that ectodomain shedding regulates the pericellular and extracellular activities of MT1-MMP through a delicate balance of active and inactive enzyme-soluble fragments.

Transforming growth factor-beta1 triggers hepatocellular carcinoma invasiveness via alpha3beta1 integrin

Metastasis occurrence in the course of hepatocellular carcinoma (HCC) severely affects prognosis and survival. We have shown that HCC invasive cells express alpha3beta1-integrin whereas noninvasive cells do not. Here we show that transforming growth factor (TGF)-beta1 stimulates alpha3-integrin expression at a transcriptional level in noninvasive HCC cells, causing transformation into a motile and invasive phenotype. Such activities are inhibited by neutralizing anti-alpha3- but not anti-alpha6-integrin monoclonal antibodies. HCC invasive cells secrete abundant levels of active TGF-beta1 in comparison with noninvasive cells, but in the latter, addition of active matrix metalloproteinases-2 increases the concentration of active TGF-beta1. In this way, the cells express alpha3-integrin at a transcriptional level and acquire motility on Ln-5. By contrast, an anti-TGF-beta1-neutralizing antibody reduces alpha3-integrin expression and the invasive ability of HCC invading cells. In HCC patients, TGF-beta1 serum concentrations and alpha3-integrin expression are strongly correlated. The integrin, absent in normal and peritumoral liver parenchyma, is abundantly expressed in HCC primary and metastatic tissue. In particular, patients with metastasis show higher levels of TGF-beta1 serum concentrations and stronger expression of TGF-beta1 and alpha3-integrin in HCC tissues. In conclusion, TGF-beta1 may play an important role in HCC invasiveness by stimulating alpha3-integrin expression, and could therefore be an important target for new therapies.

Structural insight into the complex formation of latent matrix metalloproteinase 2 with tissue inhibitor of metalloproteinase 2

Matrix metalloproteinases (MMPs) are a family of multidomain enzymes involved in the physiological degradation of connective tissue, as well as in pathological states such as tumor invasion and arthritis. Apart from transcriptional regulation, MMPs are controlled by proenzyme activation and a class of specific tissue inhibitors of metalloproteinases (TIMPs) that bind to the catalytic site. TIMP-2 is a potent inhibitor of MMPs, but it has also been implicated in a unique cell surface activation mechanism of latent MMP-2/gelatinase A/type IV collagenase (proMMP-2), through its binding to the hemopexin domain of proMMP-2 on the one hand and to a membrane-type MMP activator on the other. The present crystal structure of the human proMMP-2/TIMP-2 complex reveals an interaction between the hemopexin domain of proMMP-2 and the C-terminal domain of TIMP-2, leaving the catalytic site of MMP-2 and the inhibitory site of TIMP-2 distant and spatially isolated. The interfacial contact of these two proteins is characterized by two distinct binding regions composed of alternating hydrophobic and hydrophilic interactions. This unique structure provides information for how specificity for noninhibitory MMP/TIMP complex formation is achieved.

Design, synthesis, and characterization of potent, slow-binding inhibitors that are selective for gelatinases

Gelatinases have been shown to play a key role in angiogenesis and tumor metastasis. Small molecular weight synthetic inhibitors for these enzymes are highly sought for potential use as anti-metastatic agents. Virtually all of the known inhibitors of matrix metalloproteinases (MMPs) are broad spectrum. We report herein the synthesis and kinetic characterization of two compounds, 4-(4-phenoxyphenylsulfonyl)butane-1,2-dithiol (compound 1) and 5-(4-phenoxyphenylsulfonyl)pentane-1,2-dithiol (compound 2), that are potent and selective gelatinase inhibitors. These compounds are slow, tight-binding inhibitors of gelatinases (MMP-2 and MMP-9) with K(i) values in the nanomolar range. In contrast, competitive inhibition of the catalytic domain of membrane-type 1 metalloproteinase (MMP-14(cat)) with comparable K(i) values (K(i) approximately 200 nm) was observed. Binding to stromelysin (MMP-3) was substantially weaker, with K(i) values in the micromolar range (K(i) approximately 10 microm). No binding to matrilysin (MMP-7) and collagenase 1 (MMP-1) was detected at inhibitor concentrations up to 60 microm. We have previously shown that synthetic MMP inhibitors work synergistically with TIMP-2 in the promotion of pro-MMP-2 activation by MT1-MMP in a process that depends on the affinity of the inhibitor toward MT1-MMP. It is shown herein that the dithiols are significantly less efficient (>100-fold) than marimastat, a broad-spectrum MMP inhibitor, in enhancing pro-MMP-2 activation in cells infected to express MT1-MMP, consistent with the lower affinity of the dithiols toward MT1-MMP. Thus, in contrast to broad-spectrum MMP inhibitors, the dithiols are less likely to promote MT1-MMP-dependent pro-MMP-2 activation in the presence of TIMP-2, while maintaining their ability to inhibit active MMP-2 effectively.

Human hepatocellular carcinoma (HCC) cells require both alpha3beta1 integrin and matrix metalloproteinases activity for migration and invasion

Hepatocellular carcinoma (HCC) is the most frequent malignant tumor of the liver; prognosis depends on the tendency to metastasize. Cancer cell invasion is regulated by proteolytic remodeling of extracellular matrix components and by integrin expression. We have shown that matrix metalloproteinase-2 (MMP-2) and membrane-type-1 matrix metalloproteinase (MT1-MMP) cleave Laminin-5 (Ln-5), stimulating cell migration. Here we report that all HCC cells express MT1-MMP, migrate on Ln-1 and Collagen IV, whereas only HCC cells that express alpha3beta1 integrin secrete detectable levels of gelatinases, migrate on Ln-5, and invade through a reconstituted basement membrane (BM). Migration on Ln-5 is blocked by BB-94, an MMP inhibitor, and by MIG1, a monoclonal antibody that hinders migration on MMP-2-cleaved Ln-5. Invasion through a reconstituted BM is also inhibited by BB-94. HCC alpha3beta1-negative cells migrate on Ln-1 and Collagen IV, but not on Ln-5, and do not invade through a reconstituted BM, although they express MT1-MMP. Anti-alpha3beta1 blocking antibodies inhibit gelatinase activation, cell motility, and cell invasion through MATRIGEL: In vivo, alpha3beta1 integrin and Ln-5 are expressed in HCC tissue but not in normal liver. In conclusion, our data suggest that both alpha3beta1 integrin and gelatinase activity are required for HCC migration and invasion.

Phorbol ester tumour promoter mediated altered expression and regulation of matrix metalloproteinase-2 in a H-ras transformed cell line capable of benign tumour formation

The matrix metalloproteinases (MMPs) are thought to play key roles in tumour formation and malignant progression. The present study demonstrates alterations in the regulation of matrix metalloproteinase-2 (MMP-2) expression in response to the phorbol ester tumour promoter, PMA, in a H-ras transformed cell line, NR3, which is capable of benign tumour formation. PMA treatment of NR3 cells resulted in decreased expression of MMP-2 mRNA levels. Following a lag period, an accompanying change in gelatinolytic activity was also found. These PMA-mediated alterations in MMP-2 mRNA levels were independent of de novo protein synthesis and involved both transcriptional and post-transcriptional events. Most notably, PMA regulates MMP-2 mRNA expression through a mechanism involving message de-stabilization. Additionally, protein kinase C mediated events were found to play a role(s) in the regulation of MMP-2 message expression in NR3 cells. This study demonstrates several novel aspects regarding the regulation of MMP-2 expression in a H-ras transformed cell line and thereby provides further insight into the altered growth regulatory programs associated with H-ras mediated cellular transformation.

Tissue inhibitor of metalloproteinase (TIMP)-2 acts synergistically with synthetic matrix metalloproteinase (MMP) inhibitors but not with TIMP-4 to enhance the (Membrane type 1)-MMP-dependent activation of pro-MMP-2

The membrane-type 1 matrix metalloproteinase (MT1-MMP) has been shown to be a key enzyme in tumor angiogenesis and metastasis. MT1-MMP hydrolyzes a variety of extracellular matrix components and is a physiological activator of pro-MMP-2, another MMP involved in malignancy. Pro-MMP-2 activation by MT1-MMP involves the formation of an MT1-MMP.tissue inhibitors of metalloproteinases 2 (TIMP-2). pro-MMP-2 complex on the cell surface that promotes the hydrolysis of pro-MMP-2 by a neighboring TIMP-2-free MT1-MMP. The MT1-MMP. TIMP-2 complex also serves to reduce the intermolecular autocatalytic turnover of MT1-MMP, resulting in accumulation of active MT1-MMP (57 kDa) on the cell surface. Evidence shown here in Timp2-null cells demonstrates that pro-MMP-2 activation by MT1-MMP requires TIMP-2. In contrast, a C-terminally deleted TIMP-2 (Delta-TIMP-2), unable to form ternary complex, had no effect. However, Delta-TIMP-2 and certain synthetic MMP inhibitors, which inhibit MT1-MMP autocatalysis, can act synergistically with TIMP-2 in the promotion of pro-MMP-2 activation by MT1-MMP. In contrast, TIMP-4, an efficient MT1-MMP inhibitor, had no synergistic effect. These studies suggest that under certain conditions the pericellular activity of MT1-MMP in the presence of TIMP-2 can be modulated by synthetic and natural (TIMP-4) MMP inhibitors.

Inactivating mutation of the mouse tissue inhibitor of metalloproteinases-2(Timp-2) gene alters proMMP-2 activation

To understand the biologic function of TIMP-2, a member of the tissue inhibitors of metalloproteinases family, an inactivating mutation was introduced in the mouse Timp-2 gene by homologous recombination. Outbred homozygous mutants developed and procreated indistinguishably from wild type littermates, suggesting that fertility, development, and growth are not critically dependent on TIMP-2. Lack of functional TIMP-2, however, dramatically altered the activation of proMMP-2 both in vivo and in vitro. Fully functional TIMP-2 is essential for efficient activation of proMMP-2 in vivo. No evidence of successful functional compensation was observed. The results illustrate the duality of TIMP-2 function, i.e. at low concentrations, TIMP-2 exerts a "catalytic" or enhancing effect on cell-mediated proMMP-2 activation, whereas at higher concentrations, TIMP-2 inhibits the activation and/or activity of MMP-2.

Binding of active (57 kDa) membrane type 1-matrix metalloproteinase (MT1-MMP) to tissue inhibitor of metalloproteinase (TIMP)-2 regulates MT1-MMP processing and pro-MMP-2 activation

Previous studies have shown that membrane type 1-matrix metalloproteinase (MT1-MMP) (MMP-14) initiates pro-MMP-2 activation in a process that is tightly regulated by the level of tissue inhibitor of metalloproteinase (TIMP)-2. However, given the difficulty in modulating TIMP-2 levels, the direct effect of TIMP-2 on MT1-MMP processing and on pro-MMP-2 activation in a cellular system could not be established. Here, recombinant vaccinia viruses encoding full-length MT1-MMP or TIMP-2 were used to express MT1-MMP alone or in combination with various levels of TIMP-2 in mammalian cells. We show that TIMP-2 regulates the amount of active MT1-MMP (57 kDa) on the cell surface whereas in the absence of TIMP-2 MT1-MMP undergoes autocatalysis to a 44-kDa form, which displays a N terminus starting at Gly(285) and hence lacks the entire catalytic domain. Neither pro-MT1-MMP (N terminus Ser(24)) nor the 44-kDa form bound TIMP-2. In contrast, active MT1-MMP (N terminus Tyr(112)) formed a complex with TIMP-2 suggesting that regulation of MT1-MMP processing is mediated by a complex of TIMP-2 with the active enzyme. Consistently, TIMP-2 enhanced the activation of pro-MMP-2 by MT1-MMP. Thus, under controlled conditions, TIMP-2 may act as a positive regulator of MT1-MMP activity by promoting the availability of active MT1-MMP on the cell surface and consequently, may support pericellular proteolysis.

Fibroblast activation protein, a dual specificity serine protease expressed in reactive human tumor stromal fibroblasts

Proteolytic degradation of extracellular matrix (ECM) components during tissue remodeling plays a pivotal role in normal and pathological processes including wound healing, inflammation, tumor invasion, and metastasis. Proteolytic enzymes in tumors may activate or release growth factors from the ECM or act directly on the ECM itself, thereby facilitating angiogenesis or tumor cell migration. Fibroblast activation protein (FAP) is a cell surface antigen of reactive tumor stromal fibroblasts found in epithelial cancers and in granulation tissue during wound healing. It is absent from most normal adult human tissues. FAP is conserved throughout chordate evolution, with homologues in mouse and Xenopus laevis, whose expression correlates with tissue remodeling events. Using recombinant and purified natural FAP, we show that FAP has both dipeptidyl peptidase activity and a collagenolytic activity capable of degrading gelatin and type I collagen; by sequence, FAP belongs to the serine protease family rather than the matrix metalloprotease family. Mutation of the putative catalytic serine residue of FAP to alanine abolishes both enzymatic activities. Consistent with its in vivo expression pattern determined by immunohistochemistry, FAP enzyme activity was detected by an immunocapture assay in human cancerous tissues but not in matched normal tissues. This study demonstrates that FAP is present as an active cell surface-bound collagenase in epithelial tumor stroma and opens up investigation into physiological substrates of its novel, tumor-associated dipeptidyl peptidase activity.

Quantitative zymography of matrix metalloproteinases by measuring hydroxyproline: application to gelatinases A and B

Gelatinases A and B are metalloproteinases involved in the degradation of the extracellular matrix. Detection and quantification of these enzymes in physiological and pathological conditions such as rheumatoid arthritis, tumor invasion and metastasis may be clinically useful. Gelatin zymography is an electrophoretic technique specific for gelatinases. It can be used to detect the activity of both the active and latent forms. We have standardized this technique for the active and latent forms of gelatinase A and for the latent form of gelatinase B. We measured the extent of gelatin degradation with an EDC scanning densitometer (Helena). The value recorded was directly proportional to the amount of enzyme. Gelatinase activity was quantified from the gel by assaying hydroxyproline as an index of gelatin breakdown. Gelatin zymography was found to be useful in characterizing gelatinases A and B by their molecular weights and measuring their specific activity by a standardized analysis of the degraded gelatin substrate.

Expression of MMP-2 and MMP-9, their inhibitors, and the activator MT1-MMP in primary breast carcinomas

Enhanced expression of the type IV collagenases MMP-2 and MMP-9, or lack of their inhibitors TIMP-1 and TIMP-2, has been associated with tumour invasion and metastatic potential in several experimental models. Regulation of enzyme activity is clearly a key step in tumour invasion, and recently a potent activator of MMP-2, the membrane-associated MT1-MMP, has been described and characterized. Using an immunohistochemical approach, this study has examined the expression and distribution of the type IV collagenases, their inhibitors, and the activator MT1-MMP, in a series of 79 infiltrating ductal carcinomas (IDCs), 8 tubular carcinomas, and 27 infiltrating lobular carcinomas (ILCs). MMP-2 and MT1-MMP were expressed in more than 90 per cent of all carcinomas, with predominantly stromal and tumour cell cytoplasmic staining. However, reactivity localized on tumour cell membranes was recorded for MMP-2 in 34 per cent of cases with a monoclonal antibody and 55 per cent of cases with a polyclonal antibody, and for MT1-MMP in 68 per cent of tumours. In each case, this pattern of staining was significantly associated with the presence of lymph node metastasis (p=0.001, p=0. 008, and p=0.1, respectively). Both tumour cell and stromal staining was observed for TIMP-2, but there was no correlation with metastatic status. The 92 kD gelatinase MMP-9 was expressed by 68 per cent of carcinomas, either in the stromal compartment or by tumour cells. There was a highly significant correlation between the expression pattern of MMP-9 and tumour type, with ILCs displaying greater frequency and more homogeneous cytoplasmic staining than IDCs (p=0.0004). Staining for TIMP-1 was seen in the stroma and also in relation to small blood vessels, with more than 90 per cent of tumours showing this staining pattern using a polyclonal antibody. This study indicates distinct patterns of expression for different MMPs and demonstrates the potential importance of the MMP-2/MT1-MMP system in breast tumour progression. The association of MMP-9 with the infiltrating lobular phenotype may reveal novel mechanisms of control for this metalloproteinase.

Biophysical and functional characterization of full-length, recombinant human tissue inhibitor of metalloproteinases-2 (TIMP-2) produced in Escherichia coli. Comparison of wild type and amino-terminal alanine appended variant with implications for the mechanism of TIMP functions

Matrix metalloproteinases (MMPs) function in the remodeling of the extracellular matrix that is integral for many normal and pathological processes. The tissue inhibitor of metalloproteinases family, including tissue inhibitor of metalloproteinases-2 (TIMP-2), regulates the activity of these multifunctional metalloproteinases. TIMP family members are proteinase inhibitors that contain six conserved disulfide bonds, one involving an amino-terminal cysteine residue that is critical for MMP inhibitor activity. TIMP-2 has been expressed in Escherichia coli, folded from insoluble protein, and functionally characterized. The wild type protein inhibited gelatinase A (MMP-2), whereas a variant with an alanine appended to the amino terminus (Ala+TIMP-2) was inactive. Removal of amino-terminal alanine by exopeptidase digestion restored protease inhibitor activity. This confirms the mechanistic importance of the amino-terminal amino group in the metalloproteinase inhibitory activity, as originally suggested from the x-ray structure of a complex of MMP-3 with TIMP-1 and a complex of TIMP-2 with MT-1-MMP. The Ala+TIMP-2 variant exhibited conformational, pro-MMP-2 complex formation and fibroblast growth modulating properties of the wild type protein. These findings demonstrate that Ala+TIMP-2 is an excellent biochemical tool for examining the specific role of MMP inhibition in the multiple functions ascribed to TIMPs.

Expression of matrix metalloprotease-2-cleaved laminin-5 in breast remodeling stimulated by sex steroids

The extracellular matrix plays an important role in breast remodeling. We have shown that matrix metalloprotease-2 (MMP2) cleaves laminin-5 (Ln-5), a basement membrane component, generating a fragment called gamma2x. Human breast epithelial cells, while constitutively immobile on intact Ln-5, acquire a motile phenotype on MMP2-cleaved Ln-5. We hypothesize that this mechanism may underlie cell mobilization across the basement membrane during branching morphogenesis in breast development regulated by sex steroids. We report that the expression of MMP2 and cleavage of Ln-5 correlate well with tissue remodeling and epithelial rearrangement of the breast both in vivo and in vitro. Thus, the Ln-5 gamma2x fragment was detected by immunoblotting in sexually mature, pregnant, and postweaning, but not in prepubertal or lactating mammary glands. Furthermore, cleaved Ln-5, as well as MMP2, became detectable in remodeling glands from sexually immature rats treated with sex steroids. In rat mammary gland explants, epithelial reorganization and luminal cell morphological changes were induced by the addition of exogenous MMP2, in parallel to the appearance of cleaved Ln-5. Similar effects were observed in epithelial monolayers plated on human Ln-5 and exposed to MMP2. These results suggest that cleavage of Ln-5 by MMP2 might be regulated by sex steroids and that it may contribute to breast remodeling under physiological and possibly pathological conditions.

Production of gelatinases and tissue inhibitors of matrix metalloproteinases by equine ovarian stromal cells In vitro

Matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) play very important roles in extracellular matrix (ECM) remodeling in ovarian follicle growth and ovulation. Equine follicles are embedded in cortex that is at the center of the ovary, and they must expand/emigrate to the fossa, the only site in the ovary for ovulation. Therefore, equine ovarian stromal cells (EOSC) are probably involved in ECM remodeling during follicle growth. This study examined whether cultured EOSC synthesize gelatinases and TIMPs, molecules essential for ECM remodeling in other systems. Results showed that cultured EOSC (passage 3-8) had a fibroblast-like morphology and were positive for alpha-smooth muscle actin and type I procollagen by immunostaining. Gelatinase A (MMP-2), gelatinase B (MMP-9), TIMP-1, and TIMP-2 were present in EOSC-conditioned medium, and TIMP-3 in ECM of EOSC. Transforming growth factor beta significantly stimulated the activity of gelatinases A and B and TIMP-1 in conditioned medium from EOSC (p < 0.05). Phorbol 12-myristate 13-acetate also significantly stimulated the activity of gelatinases A and B and TIMP-1 in conditioned medium and of TIMP-3 in ECM (p < 0.05). Our results suggest that EOSC produce important components of the ECM remodeling machinery and, therefore, may play a role in the ECM remodeling during follicle growth in this species.

Glycosylation and NH2-terminal domain mutants of the tissue inhibitor of metalloproteinases-1 (TIMP-1)

Mutants in the tissue inhibitor of metalloproteinases-1 (TIMP-1) protein have been created by site-directed mutagenesis and expressed in HeLa cells, using a recombinant vaccinia virus system. Removal of either or both glycosylation sites yielded proteins which retained wild-type inhibitory activity against both human fibroblast-type collagenase (FIB-CL) and Mr 72000 gelatinase (GL). However, the double glycosylation mutant protein was expressed at a level that was 2-4-fold lower than that of the wild-type or the single site glycosylation mutants. The 'tiny-TIMP' COOH-terminal deletion mutant that lacks the last 57 residues was also inhibitory, but the dose-response curve suggested that the interaction with the Mr 72000 gelatinase had been altered. A number of replacement mutants in the highly conserved NH2-terminal domain, including replacement of P5A and P8A or a double mutation in the VIRAK sequence which is absolutely conserved in all TIMPs in all species (VIRAK to VIAAA), also yielded functional proteins capable of inhibiting FIB-CL and Mr 72000 GL and of forming SDS-resistant complexes with FIB-CL. None of the above manipulations abolished inhibitory function suggesting that binding of the inhibitor by the enzyme involves multiple interactions.

Cytokine inducible matrix metalloproteinase expression in immortalized rat chondrocytes is independent of nitric oxide stimulation

The objective of this study was to determine if an immortalized mammalian chondrocyte cell line had a profile of matrix metalloproteinase (MMP) expression that was consistent with what has been reported for primary chondrocytes in vitro and in vivo. A combination of zymography, Western, and Northern analysis was used to examine the expression of MMPs that are relevant to cartilage degradation. Both interleukin-1beta and tumor necrosis factor alpha induced a 4- to 9-fold increase in the level of MMP-9 expression in conditioned media, and a 17- to 24-fold increase in MMP-3 mRNA. Other compounds such as basic fibroblast growth factor and staurosporine each increased MMP-9 expression individually and potentiated the effects of the two cytokines. Transforming growth factor beta had no positive or inhibitory effects. N-methyl arginine blocked the increase in nitric oxide observed following treatment with the cytokines but did not prevent the increased expression of MMPs. The pattern of metalloproteinase expression observed in IRC cells and the response to cytokines is very similar to what has been reported during the pathogenesis of osteoarthritis. The IRC cells should be useful as a model system to study basic mechanisms controlling chondrocyte MMP expression and to identify pharmacological modulators of this process.

Cloning, expression, and characterization of chicken tissue inhibitor of metalloproteinase-2 (TIMP-2) in normal and transformed chicken embryo fibroblasts

Rous sarcoma virus-transformed chicken embryo fibroblasts (RSVCEF), when compared to normal CEF, produce elevated levels of matrix metalloproteinase-2 (MMP-2) that exists in a form free of complexed tissue inhibitor of metalloproteinase-2 (TIMP-2). In order to ascertain whether the increased levels of TIMP-free MMP-2 in RSVCEF cultures are due to diminished expression of TIMP-2 or alterations in TIMP-2 that diminish its MMP-2 binding ability, it was necessary to clone, characterize, and express chicken TIMP-2 cDNA. The TIMP-2 cDNA was cloned from a chick embryo lambda gt11 library by RT-PCR using primers based on amino-acid sequences determined from isolated TIMP-2. The deduced amino acid sequence for chicken TIMP-2 is 81% identical to human TIMP-2; most of the sequence differences lie in the carboxyl terminal portion of chicken TIMP-2. Northern analysis of mRNA levels in CEF and RSVCEF demonstrates that TIMP-2 mRNA levels are increased in RSVCEF. However, TIMP-2 protein levels, relative to proMMP-2 levels, appear to decrease upon transformation and suggest additional control of TIMP-2 at the post-transcriptional level. Addition of recombinantly expressed TIMP-2 to RSVCEF cultures causes a disappearance of TIMP-free (TF) proMMP-2 with a corresponding increase in the TIMP-complexed (TC) proMMP-2 levels, demonstrating that TF proMMP-2 is capable of converting to TC pro-MMP-2 when free TIMP-2 is available. Surprisingly, RSVCEF cultures manifest a TIMP-2 population that is not complexed to MMP-2, despite the coexistence of TIMP-free proMMP-2. Gel-filtration analysis indicates that this uncomplexed TIMP-2 exhibits an apparent molecular weight of 50 kDa, indicating it is not free TIMP-2 and that it exists in transformed cultures in a noncovalent complex with an undefined molecule. Thus transformed cells can alter the TIMP-2/MMP-2 balance by transcriptional and post-translational modifications, yielding a population of inhibitor-free, proteolytically active MMP2.

Interaction of matrix metalloproteinases-2 and -9 with pregnancy zone protein and alpha2-macroglobulin

The binding of matrix metalloproteinases-2 and -9 to pregnancy zone protein and alpha2-macroglobulin was studied. The binding was demonstrated by formation of dimeric as well as tetrameric complexes of pregnancy zone protein and by the formation of alpha2-macroglobulin complexes with fast and intermediate mobility in native gel electrophoresis. The complex formation was confirmed by the use of 125I-labeled matrix metalloproteinase-2. The cleavage sites in the "bait" regions following formation of high-molecular-weight complexes of matrix metalloproteinases with the alpha-macroglobulins were determined by protein sequence analysis. Pregnancy zone protein was cleaved at Thr693-Tyr694 and alpha2-macroglobulin at Gly679-Leu680 and Arg696-Leu697 by matrix metalloproteinase-2. Matrix metalloproteinase-9 cleaved alpha2-macroglobulin at the same site as matrix metalloproteinase-2, but cleavage of pregnancy zone protein was at Leu753-Ser754. The sequences of the bands, visualized in the SDS gel, of approximately 90 and 165 kDa or higher molecular weight complexes were the same. This indicates that the matrix metalloproteinases cleaved the inhibitors with or without binding to them. The present results suggest that matrix metalloproteinases-2 and -9 may interact with pregnancy zone protein and alpha2-macroglobulin in vivo.

Induction of cell migration by matrix metalloprotease-2 cleavage of laminin-5

Structural changes in the extracellular matrix are necessary for cell migration during tissue remodeling and tumor invasion. Specific cleavage of laminin-5 (Ln-5) by matrix metalloprotease-2 (MMP2) was shown to induce migration of breast epithelial cells. MMP2 cleaved the Ln-5 gamma2 subunit at residue 587, exposing a putative cryptic promigratory site on Ln-5 that triggers cell motility. This altered form of Ln-5 is found in tumors and in tissues undergoing remodeling, but not in quiescent tissues. Cleavage of Ln-5 by MMP2 and the resulting activation of the Ln-5 cryptic site may provide new targets for modulation of tumor cell invasion and tissue remodeling.

Inhibition of osteolytic bone metastasis of breast cancer by combined treatment with the bisphosphonate ibandronate and tissue inhibitor of the matrix metalloproteinase-2

Multiple steps are involved in the metastasis of cancer cells from primary sites to distant organs. These steps should be considered in the design of pharmacologic approaches to prevent or inhibit the metastatic process. In the present study, we have compared the effects of inhibiting several steps involved in the bone metastatic process individually with inhibition of both together. The steps we chose were matrix metalloproteinase (MMP) secretion, likely involved in tumor cell invasion, and osteoclastic bone resorption, the final step in the process. We used an experimental model in which inoculation of human estrogen-independent breast cancer MDA-231 cells into the left cardiac ventricle of female nude mice causes osteolytic lesions in bone. To inhibit cancer invasiveness, the tissue inhibitor of the MMP-2 (TIMP-2), which is a natural inhibitor of MMPs, was overexpressed in MDA-231 cells. To inhibit bone resorption, a potent bisphosphonate, ibandronate (4 microg/mouse) was daily administered subcutaneously. Nude mice received either; (a) nontransfected MDA-231 cells; (b) nontransfected MDA231 cells and ibandronate; (c) TIMP-2-transfected MDA-231 cells; or (d) TIMP-2-transfected MDA-231 cells and ibandronate. In mice from group a, radiographs revealed multiple osteolytic lesions. However, in mice from group b or group c, osteolytic lesions were markedly decreased. Of particular note, in animals from group d receiving both ibandronate and TIMP-2-transfected MDA-231 cells, there were no radiologically detectable osteolytic lesions. Survival rate was increased in mice of groups c and d. There was no difference in local enlargement in the mammary fat pad between nontransfected and TIMP-2-transfected MDA-231 cells. These results suggest that inhibition of both MMPs and osteoclastic bone resorption are more efficacious treatment for prevention of osteolytic lesions than either alone, and suggest that when therapies are designed based on the uniqueness of the bone microenvironment and combined with several common steps in the metastatic process, osteolytic bone metastases can be more efficiently and selectively inhibited.

Control of type IV collagenase activity by components of the urokinase-plasmin system: a regulatory mechanism with cell-bound reactants

The urokinase-type plasminogen activator (uPA) and the matrix-degrading metalloproteinases MMP-2 and MMP-9 (type IV collagenases/gelatinases) have been implicated in a variety of invasive processes, including tumor invasion, metastasis and angiogenesis. MMP-2 and MMP-9 are secreted in the form of inactive zymogens that are activated extracellularly, a fundamental process for the control of their activity. The physiological mechanism(s) of gelatinase activation are still poorly understood; their comprehension may provide tools to control cell invasion. The data reported in this paper show multiple roles of the uPA-plasmin system in the control of gelatinase activity: (i) both gelatinases are associated with the cell surface; binding of uPA and plasmin(ogen) to the cell surface results in gelatinase activation without the action of other metallo- or acid proteinases; (ii) inhibition of uPA or plasminogen binding to the cell surface blocks gelatinase activation; (iii) in soluble phase plasmin degrades both gelatinases; and (iv) gelatinase activation and degradation occur in a dose- and time-dependent manner in the presence of physiological plasminogen and uPA concentrations. Thus, the uPA-plasmin system may represent a physiological mechanism for the control of gelatinase activity.

Activation of progelatinase A and progelatinase A/TIMP-2 complex by membrane type 2-matrix metalloproteinase

C-terminal truncated membrane-type 2 matrix metalloproteinase (MT2-MMP1-269), comprising prodomain and catalytic domain, was expressed as a soluble protein in Escherichia coli. Unlike the corresponding form of MT1-MMP, which can be isolated as a 31 kDa protein, MT2-MMP1-269 proved to be comparatively instable, and already the freshly isolated preparation displayed several proteins in SDS-PAGE representing MT2-MMP1-269 (33 kDa) and four N-truncated forms with N-termini methionine32 (30 kDa), isoleucine37 (30 kDa), leucine84 (24 kDa), and leucine93 (22 kDa), the catalytic domain. After thawing of frozen preparations the 33 and the 30 kDa proforms were no longer detectable in SDS-PAGE, and only the 24 and 22 kDa forms remained. The catalytic domain of MT2-MMP activated progelatinase A as well as the progelatinase A/TMP-2 complex by cleaving the 72 kDa progelatinase A to yield 67 kDa gelatinase A, which is then transformed into 62 kDa gelatinase A. The 62 kDa form is about twice as active as the 67 kDa form towards the synthetic substrate N-(2,4)-dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg. No significant difference in activity was found between free and complexed gelatinase A forms. the activation of the progelatinase A/TIMP-2 complex proceeds in two steps: At first MT2-MMP is inhibited by the progelatinase A/TIMP-2/MT2-MMP, complex, whereby a ternary complex, progelatinase A/TIMP-2/ MT-2MMP is generated. This ternary complex is then activated by excess MT2-MMP. Our results suggest a mechanism for spatially regulated extracellular gelatinase A activity mediated by activation with membrane-type MMPs; Free gelatinase A is released into the extracellular space, while gelatinase A/TIMP-2 bound to MT-MMP remains anchored on the cell surface.

Mechanisms of glioma invasion: role of matrix-metalloproteinases

One of the most lethal properties of high grade gliomas is their ability to invade the surrounding normal brain tissue, as infiltrated cells often escape surgical resection and inevitably lead to tumour recurrence. The consequent poor prognosis and survival rate underscore the need to further understand and target the cellular mechanisms that underly tumour invasiveness. Proteases which degrade the surrounding stromal cells and extracellular matrix proteins have been demonstrated to be critical effectors of invasion for tumours of both central and peripheral origin. Within the nervous system, the role of metalloproteinases as well as other classes of proteases in mediating the invasive phenotype of high grade gliomas has been an intense area of research. We present in this article a review of this literature and address the possibility that these proteases and the biochemical pathways that regulate their expression, such as protein kinase C, may represent potential targets in the therapy of high grade gliomas.

Expression of tissue inhibitor of metalloproteinases TIMP-2 in human colorectal cancer--a predictor of tumour stage

The aim of this study was to investigate whether immunohistochemical staining patterns of tissue inhibitor of metalloproteinases TIMP-2 and matrix metalloproteinases MMP-2 and MMP-9 can be predictors of tumour stage and survival time in colorectal cancer. Frozen tumour sections from 212 patients operated on between January 1987 and November 1990 were investigated. Three mouse monoclonal antibodies--T2-101 against TIMP-2, CA-4001 against MMP-2 and GE-213 against MMP-9--were used. Positive expression of TIMP-2 (a) in basement membranes and (b) diffusely in stroma with (c) subglandular enhancement was found significantly (P < 0.01, P < 0.05, P < 0.05) more often in localized tumours than in tumours with regional or distant metastases. Neither pattern correlated with tumour differentiation. Patterns (a) and (c) correlated with longer survival time (P < 0.05); (b) reached near significance (P < 0.07). When the survival analyses were restricted to potentially cured patients, neither pattern could foretell death from cancer. Positive expression of MMP-2 in tumour epithelium and of MMP-9 in tumour-infiltrating macrophages were both independent of tumour stage and were without correlation with survival time. A large number of MMP-9-positive macrophages correlated (P < 0.05) with poor tumour differentiation, whereas weak or absent epithelial MMP-2 staining reached near significance (P < 0.08). Exploration of TIMP-2 expression is valuable for the discrimination between macroscopically localized and metastatic colorectal cancer, but it cannot predict which of the potentially cured patients are likely to have micrometastases. MMP-2 and MMP-9 stainings are of minor value in staging and prognostic prediction.

Expression of functional recombinant human procathepsin B in mammalian cells

Cathepsin B has been implicated in numerous pathobiological processes. In order to study its interactions with other proteins implicated in these processes, quantities of functional recombinant cathepsin B are needed. Therefore, we expressed recombinant human procathepsin B in mammalian cells (BSC-1 monkey kidney cells and HeLa human cervical carcinoma cells) using a vaccinia virus expression system. The recombinant human procathepsin B appeared to be authentic and expressed in its native conformation as indicated by: (1) N-terminal sequencing; (2) molecular size; (3) processing intracellularly to mature double-chain cathepsin B; (4) in vitro cleavage by pepsin to mature cathepsin B coincident with appearance of activity against a selective synthetic substrate; and (5) substrate/inhibitor profiles. This is the first report of the expression of functional recombinant human procathepsin B in mammalian cells. We also report a single-step immunoaffinity purification procedure for the isolation of electrophoretically pure proenzyme. By the methodologies described, human procathepsin B can now be obtained in high yield. This should facilitate studies of its interactions with protease inhibitors, other proteases, extracellular matrices, cell-surface proteins and biological substrates that may be of relevance to the pathobiological functions of this enzyme.

Matrix metalloproteinase 2 releases active soluble ectodomain of fibroblast growth factor receptor 1

Recent studies have demonstrated the existence of a soluble fibroblast growth factor (FGF) receptor type 1 (FGFR1) extracellular domain in the circulation and in vascular basement membranes. However, the process of FGFR1 ectodomain release from the plasma membrane is not known. Here we report that the 72-kDa gelatinase A (matrix metalloproteinase type 2, MMP2) can hydrolyze the Val368-Met369 peptide bond of the FGFR1 ectodomain, eight amino acids upstream of the transmembrane domain, thus releasing the entire extracellular domain. Similar results were obtained regardless of whether FGF was first bound to the receptor or not. The action of MMP2 abolished binding of FGF to an immobilized recombinant FGFR1 ectodomain fusion protein and to Chinese hamster ovary cells overexpressing FGFR1 The released recombinant FGFR1 ectodomain was able to bind FGF after MMP2 cleavage, suggesting that the cleaved soluble receptor maintained its FGF binding capacity. The activity of MMP2 could not be reproduced by the 92-kDa gelatinase B (MMP9) and was inhibited by tissue inhibitor of metalloproteinase type 2. These studies demonstrate that FGFR1 may be a specific target for MMP2 on the cell surface, yielding a soluble FGF receptor that may modulate the mitogenic and angiogenic activities of FGF.

Expression of matrix metalloproteinase gelatinases A and B by cultured epithelial cells from human bronchial explants

To investigate the role of human bronchial epithelial cells (HBECs) in the maintenance and remodeling of the extracellular matrix, we evaluated the expression by HBECs of 72- and 92-kDa gelatinases under basal conditions and after exposure to bacterial lipopolysaccharides (LPS). Confluent HBECs from explants were cultured in plastic dishes coated with type I and III collagens. Gelatin zymography of HBEC-conditioned media showed constitutive major 92-kDa and minor 72-kDa gelatinases recognized by specific human antibodies and totally inhibited by the metalloproteinase inhibitor EDTA. The identification of the two matrix metalloproteinases was confirmed by quantitative reverse transcription-polymerase chain reaction. Identical patterns of gelatinase expression were observed with repetitive primary cultures issued from the same explants. Zymography showed that exposure of HBECs to LPS induced 2- and 20-fold increases in 92-kDa gelatinase production and activation, respectively, as well as a smaller increase in activated 68-kDa gelatinase. With [3H]gelatin substrate, elevated metallogelatinolytic activity (138 microgram of hydrolyzed gelatin/48 h/10(6) cells) was also observed, whereas no activity was detected in the absence of LPS. A human epithelial cell line (16HBE14o-) exhibited the same basal profile of gelatinase activity, but this profile remained unchanged after exposure to LPS. Quantitative reverse transcription-polymerase chain reaction demonstrated only minimal changes in 92-kDa mRNA levels in response to LPS, but the half-life of 92-kDa gelatinase mRNA was increased with exposure to LPS. In contrast, concomitant slight increases in 72-kDa gelatinase protein and mRNA were found, suggesting that the control mechanisms regulating the expression of 92- and 72-kDa gelatinases by HBECs in response to LPS are divergent. All these data allowed us to propose that HBECs may be actively involved in the physiological and physiopathological remodeling of the airway basement membrane.

Metalloproteinase activity secreted by fibrogenic cells in the processing of prolysyl oxidase. Potential role of procollagen C-proteinase

Lysyl oxidase is secreted from fibrogenic cells as a 50-kDa proenzyme that is proteolytically processed to the mature enzyme in the extracellular space. To characterize the secreted proteinase activity, a truncated, recombinant form of lysyl oxidase was prepared as a proteinase substrate containing the sequence of the propeptide cleavage region. The processing proteinase activity secreted by cultured fibrogenic cells resists inhibitors of serine or aspartyl proteinases as well as tissue inhibitor of matrix metalloproteinases-2 (MMP-2) but is completely inhibited by metal ion chelators. Known metalloproteinases were tested for their activity toward this substrate. Carboxyl-terminal procollagen proteinase (C-proteinase), MMP-2, and conditioned fibrogenic cell culture medium cleave the lysyl oxidase substrate to the size of the mature enzyme. The NH2-terminal sequence generated by arterial smooth muscle conditioned medium and the C-proteinase but not by MMP-2, i.e. Asp-Asp-Pro-Tyr, was identical to that previously identified in mature lysyl oxidase isolated from connective tissue. The C-proteinase activity against the model substrate was inhibited by a synthetic oligopeptide mimic of the cleavage sequence (Ac-Met-Val-Gly-Asp-Asp-Pro-Tyr-Asn-amide), whereas this peptide also inhibited the generation of lysyl oxidase activity in the medium of fetal rat lung fibroblasts in culture. In toto, these results identify a secreted metalloproteinase activity participating in the activation of prolysyl oxidase, identify inhibitors of the processing activity, and implicate procollagen C-proteinase in this role.

Matrix metalloproteinase 9 (gelatinase B) is expressed in multinucleated giant cells of human giant cell tumor of bone and is associated with vascular invasion

Human giant cell tumor (GCT) consists of multinucleated giant cells and mononuclear stromal cells, and is characterized by frequent vascular invasion without distant metastases. To study the role of matrix metalloproteinases (MMPs) in the vascular invasion, we examined production of MMP-1 (tissue collagenase), -2 (gelatinase A), -3 (stromelysin-1), -9 (gelatinase B), and tissue inhibitors of metalloproteinases (TIMP-1 and -2) in GCT. MMP-9 was highly and predominantly expressed in giant cells by both immunohistochemistry and in situ hybridization. Expression of other MMPs was also observed in some cases but was inconstant. Sandwich enzyme immunoassays demonstrated that MMP-9 is the predominant MMP secreted by GCT. There was a definite imbalance between the amounts of MMP-9 and those of TIMPs in the culture media of GCT, leading to detectable gelatinolytic activity in an assay using 14C-gelatin. Gelatin zymography demonstrated the main activity at about 90 kd, which was identified as the zymogen of MMP-9 by immunoblotting. Immunohistochemistry for type IV collagen and laminin, major basement membrane components, showed that disappearance of the proteins is closely associated with MMP-9-positive giant cells. These results indicate the production of MMP-9 by multinucleated giant cells and suggest that the metalloproteinase may contribute to proteolysis associated with vascular invasion and local bone resorption in human GCT.

Increased expression of 72-kd type IV collagenase (MMP-2) in human aortic atherosclerotic lesions

MMP-2, a secreted 72-kd metalloproteinase that specifically degrades type IV collagen as well as denatured collagens, has been implicated in smooth muscle cell migration. To evaluate the possible contribution of this enzyme to the formation and progression of the atherosclerotic lesion, the expression of MMP-2 was studied in human aortic tissue. MMP-2 was visualized in frozen sections of the aortic wall by an immunofluorescent technique with a polyclonal antibody. Expression of MMP-2 in the aortic extracts was also studied by zymography and Western blotting. Our results reveal that a greater amount of MMP-2 is present in fatty streaks and atherosclerotic plaques as compared with normal regions of the aorta. Immunoblotting analysis showed that MMP-2 was expressed in atherosclerotic plaque > fatty streak > normal aortic wall in a ratio of approximately 4:2:1. Zymograms show that both forms (activated and latent) of MMP-2 increased in the atherosclerotic plaques. The presence of macrophages, detected by an immunohistochemical technique in some areas of higher MMP-2 expression suggests that these cells are a possible source of MMP-2. We conclude that MMP-2 collagenase may have a role in the formation and progression of the atherosclerotic lesion and may be involved in clinical complications of atherosclerosis, such as fissure and rupture, leading to thrombosis.

Steps involved in activation of the pro-matrix metalloproteinase 9 (progelatinase B)-tissue inhibitor of metalloproteinases-1 complex by 4-aminophenylmercuric acetate and proteinases

The precursor of matrix metalloproteinase 9 (pro-MMP-9, progelatinase B) noncovalently binds to tissue inhibitor of metalloproteinases (TIMP)-1 through the C-terminal domain of each molecule. We have isolated the proMMP-9.TIMP-1 complex from the medium of human fibrosarcoma HT-1080 cells and investigated the activation processes of the complex by 4-aminophenylmercuric acetate, trypsin, and matrix metalloproteinase 3 (MMP-3, stromelysin 1). The treatment of the proMMP-9.TIMP-1 complex with 4-aminophenylmercuric acetate or trypsin converts proMMP-9 to lower molecular weight species corresponding to active forms, but no gelatinolytic activity is detected. The lack of enzymic activity results from binding of TIMP-1 to the activated MMP-9. The treatment of the proMMP-9.TIMP-1 complex with a possible physiological proMMP-9 activator, MMP-3, does not reveal any gelatinolytic activity unless the molar ratio of MMP-3 to the complex exceeds 1. This is due to the inhibition of MMP-3 by TIMP-1 forming a ternary proMMP-9.TIMP-1.MMP-3 complex. The formation of the ternary complex weakens the interaction between proMMP-9 and TIMP-1, resulting in partial dissociation of the complex into proMMP-9 and the TIMP-1.MMP-3 complex. When MMP-3 is in excess, the propeptide is completely processed, and the full activity of MMP-9 is detected. Similarly, the proMMP-9.TIMP-1 complex inhibits MMP-1 (interstitial collagenase) and in turn renders the proMMP-9 activable by a catalytic amount of MMP-3. These results suggest that formation of the proMMP-9.TIMP-1 complex regulates extracellular matrix breakdown in tissue by switching the predominant MMP activity from one type to another.

Generation and activity of the ternary gelatinase B/TIMP-1/LMW-stromelysin-1 complex

Incubation of progelatinase B, isolated from human polymorphonuclear leukocytes, with TIMP-1 leads to the formation of the progelatinase B/TIMP-1 complex. This complex behaves like a Janus in a similar manner as we previously described for the progelatinase A/TIMP-2 complex. It shows the properties of TIMP-1 and is a better inhibitor for gelatinase A than for gelatinase B. Treatment with trypsin leads to activation of the binary complex. The activity, however, amounts only to slightly more than 10% of the activity of free gelatinase B, not complexed with TIMP-1. When the progelatinase B/TIMP-1 complex inhibits an active matrix metalloproteinase, a ternary complex is generated that after activation displays a distinct higher proteolytic activity than the active binary complex. The active binary complex cannot be transformed into the active ternary complex.

Steps involved in activation of the complex of pro-matrix metalloproteinase 2 (progelatinase A) and tissue inhibitor of metalloproteinases (TIMP)-2 by 4-aminophenylmercuric acetate

Tissue inhibitor of metalloproteinases (TIMP)-2 forms a noncovalent complex with the precursor of matrix metalloproteinase 2 (proMMP-2, progelatinase A) through interaction of the C-terminal domain of each molecule. We have isolated the proMMP-2-TIMP-2 complex from the medium of human uterine cervical fibroblasts and investigated the processes involved in its activation by 4-aminophenylmercuric acetate (APMA). The treatment of the complex with APMA-activated proMMP-2 by disrupting the Cys73-Zn2+ interaction of the zymogen. This is triggered by perturbation of the proMMP-2 molecule, but not by the reaction of the SH group of Cys73 with APMA. The 'activated' proMMP-2 (proMMP-2*) formed a new complex with TIMP-2 by binding to the N-terminal inhibitory domain of the inhibitor without processing the propeptide. Thus the APMA-treated proMMP-2*-TIMP-2 complex exhibited no gelatinolytic activity. In the presence of a small amount of free MMP-2, however, proMMP-2* in the complex was converted into the 65 kDa MMP-2 by proteolytic attack of MMP-2, but the complex did not exhibit gelatinolytic activity. The gelatinolytic activity detected after APMA treatment was solely derived from the activation of free proMMP-2. The removal of the propeptide of the proMMP-2* bound to TIMP-2 was also observed by MMP-3 (stromelysin 1), but not by MMP-1 (interstitial collagenase). MMP-3 cleaved the Asn80-Tyr81 bond of proMMP-2*. On the other hand, when MMP-3 was incubated with the proMMP-2-TIMP-2 complex, it bound to TIMP-2 and rendered proMMP-2 readily activatable by APMA. These results indicate that the blockage of TIMP-2 of the complex with an active MMP is essential for the activation of proMMP-2 when it is complexed with TIMP-2.

Cell surface binding of TIMP-2 and pro-MMP-2/TIMP-2 complex

Tissue inhibitor of metalloproteinases (TIMP-2) is a low molecular weight proteinase inhibitor capable of inhibiting activated matrix metalloproteinases (MMPs). TIMP-2 is found both free and in a 1:1 stoichiometric complex with the pro-enzyme form of MMP-2 (pro-MMP-2/TIMP-2 complex). We have measured the binding of recombinant TIMP-2 to intact HT-1080 and MCF-7 cells. HT-1080 cells in suspension bound 125I-labeled rTIMP-2 with a Kd of 2.5 nM and 30,000 sites/cell. Monolayers of MCF-7 cells were similarly found to bind [125I]rTIMP-2 with a Kd of 1.6 nM and 25,000 sites/cell. Specific binding of MMP-2 alone to HT-1080 cells was not observed; however, pro-MMP-2/TIMP-2 complex was capable of binding to the surface of HT-1080 cells in a TIMP-2-dependent manner. Binding of rTIMP-2 was not competed by the presence of TIMP-1. These results suggest that rTIMP-2 alone binds directly to the cell surface of HT-1080 and MCF-7 cell lines, and TIMP-2 is capable of localizing MMP-2 to the surface of HT-1080 cells via interaction with a specific binding site.