Membrane-type 1 matrix metalloproteinase-mediated progelatinase A activation in non-tumorigenic and tumorigenic human keratinocytes

Matrix Metalloproteinases (MMPs) in Targeted Drug Delivery: Synthesis of a Potent and Highly Selective Inhibitor against Matrix Metalloproteinase- 7

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of zinc endopeptidases that play a key role in both physiological and pathological tissue degradation. MMPs have reportedly shown great potentials in the degradation of the Extracellular Matrix (ECM), have shown great potentials in targeting bioactive and imaging agents in cancer treatment. MMPs could provoke Epithelial to Mesenchymal Transition (EMT) of cancer cells and manipulate their signaling, adhesion, migration and invasion to promote cancer cell aggressiveness. Therefore, targeting and particularly inhibiting MMPs within the tumor microenvironment is an effective strategy for cancer treatment. Based on this idea, different MMP inhibitors (MMPIs) have been developed to manipulate the tumor microenvironment towards conditions appropriate for the actions of antitumor agents. Studies are ongoing to improve the selectivity and specificity of MMPIs. Structural optimization has facilitated the discovery of selective inhibitors of the MMPs. However, so far no selective inhibitor for MMP-7 has been proposed.

AIMS

This study aims to comprehensively review the potentials and advances in applications of MMPs particularly MMP-7 in targeted cancer treatment approaches with the main focus on targeted drug delivery. Different targeting strategies for manipulating and inhibiting MMPs for the treatment of cancer are discussed. MMPs are upregulated at all stages of expression in cancers. Different MMP subtypes have shown significant targeting applicability at the genetic, protein, and activity levels in both physiological and pathophysiological conditions in a variety of cancers. The expression of MMPs significantly increases at advanced cancer stages, which can be used for controlled release in cancers in advance stages.

METHODS

Moreover, this study presents the synthesis and characteristics of a new and highly selective inhibitor against MMP-7 and discusses its applications in targeted drug delivery systems for therapeutics and diagnostics modalities.

RESULTS

Our findings showed that the structure of the inhibitor P3' side chains play the crucial role in developing an optimized MMP-7 inhibitor with high selectivity and significant degradation activities against ECM.

CONCLUSION

Optimized NDC can serve as a highly potent and selective inhibitor against MMP-7 following screening and optimization of the P3' side chains, with a Ki of 38.6 nM and an inhibitory selectivity of 575 of MMP-7 over MMP-1.

Epithelial-to-mesenchymal transition and invadopodia markers in breast cancer: Lumican a key regulator

A great hallmark of breast cancer is the absence or presence of estrogen receptors ERα and ERβ, with a dominant role in cell proliferation, differentiation and cancer progression. Both receptors are related with Epithelial-to-Mesenchymal Transition (EMT) since there is a relation between ERs and extracellular matrix (ECM) macromolecules expression, and therefore, cell-cell and cell-ECM interactions. The endocrine resistance of ERα endows epithelial cells with increased aggressiveness and induces cell proliferation, resulting into a mesenchymal phenotype and an EMT status. ERα signaling may affect the transcriptional factors which govern EMT. Knockdown or silencing of ERα and ERβ in MCF-7 and MDA-MB-231 breast cancer cells respectively, provoked pivotal changes in phenotype, cellular functions, mRNA and protein levels of EMT markers, and consequently the EMT status. Mesenchymal cells owe their migratory and invasive properties to invadopodia, while in epithelial cells, lamellipodia and filopodia are mostly observed. Invadopodia, are actin-rich protrusions of plasma membrane, promoting proteolytic degradation of ECM and tumor invasion. Cortactin and MMP-14 govern the formation and principal functions of invadopodia. In vitro experiments proved that lumican inhibits cortactin and MMP-14 expression, alters the formation of lamellipodia and transforms mesenchymal cells into epithelial-like. Conclusively, lumican may inhibit or even reverse the several metastatic features that EMT endows in breast cancer cells. Therefore, a lumican-based anti-cancer therapy which will pharmacologically target and inhibit EMT might be interesting to be developed.

Strategies to Target Matrix Metalloproteinases as Therapeutic Approach in Cancer

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that are capable of degrading numerous extracellular matrix (ECM) components thus participating in physiological and pathological processes. Apart from the remodeling of ECM, they affect cell-cell and cell-matrix interactions and are implicated in the development and progression of various diseases such as cancer. Numerous studies have demonstrated that MMPs evoke epithelial to mesenchymal transition (EMT) of cancer cells and affect their signaling, adhesion, migration and invasion to promote cancer cell aggressiveness. Various studies have suggested MMPs as suitable targets for treatment of malignancies, and several MMP inhibitors (MMPIs) have been developed. Although initial trials have failed to establish MMPIs as anticancer agents due to lack of specificity and side effects, new MMPIs have been developed with improved action that are currently being investigated. Furthermore, novel strategies that target MMPs for improving drug delivery and regulating their activity in tumors are presented. This review summarizes the implication of MMPs in cancer progression and discusses the advancements in their targeting.

Lumican Inhibits SNAIL-Induced Melanoma Cell Migration Specifically by Blocking MMP-14 Activity

Lumican, a small leucine rich proteoglycan, inhibits MMP-14 activity and melanoma cell migration in vitro and in vivo. Snail triggers epithelial-mesenchymal transitions endowing epithelial cells with migratory and invasive properties during tumor progression. The aim of this work was to investigate lumican effects on MMP-14 activity and migration of Snail overexpressing B16F1 (Snail-B16F1) melanoma cells and HT-29 colon adenocarcinoma cells. Lumican inhibits the Snail induced MMP-14 activity in B16F1 but not in HT-29 cells. In Snail-B16F1 cells, lumican inhibits migration, growth, and melanoma primary tumor development. A lumican-based strategy targeting Snail-induced MMP-14 activity might be useful for melanoma treatment.

Lumican - derived peptides inhibit melanoma cell growth and migration

Lumican, a small leucine-rich proteoglycan of the extracellular matrix, presents potent anti-tumor properties. Previous works from our group showed that lumican inhibited melanoma cell migration and tumor growth in vitro and in vivo. Melanoma cells adhered to lumican, resulting in a remodeling of their actin cytoskeleton and preventing their migration. In addition, we identified a sequence of 17 amino acids within the lumican core protein, named lumcorin, which was able to inhibit cell chemotaxis and reproduce anti-migratory effect of lumican in vitro. The aim of the present study was to characterize the anti-tumor mechanism of action of lumcorin. Lumcorin significantly decreased the growth in monolayer and in soft agar of two melanoma cell lines - mice B16F1 and human SK-MEL-28 cells - in comparison to controls. Addition of lumcorin to serum free medium significantly inhibited spontaneous motility of these two melanoma cell lines. To characterize the mechanisms involved in the inhibition of cell migration by lumcorin, the status of the phosphorylation/dephosphorylation of proteins was examined. Inhibition of focal adhesion kinase phosphorylation was observed in presence of lumcorin. Since cancer cells have been shown to migrate and to invade by mechanisms that involve matrix metalloproteinases (MMPs), the expression and activity of MMPs were analyzed. Lumcorin induced an accumulation of an intermediate form of MMP-14 (~59kDa), and inhibited MMP-14 activity. Additionally, we identified a short, 10 amino acids peptide within lumcorin sequence, which was able to reproduce its anti-tumor effect on melanoma cells. This peptide may have potential pharmacological applications.

Lumican effects in the control of tumour progression and their links with metalloproteinases and integrins

Lumican is a member of the small leucine-rich proteoglycan family. It is present in numerous extracellular matrices of different tissues, such as muscle, cartilage, and cornea. In skin, lumican is present as a glycoprotein. It plays a critical role in collagen fibrillogenesis, as shown by knocking out of its gene in mice. A direct link between lumican expression and melanoma progression and metastasis has been demonstrated. Lumican was shown to impede tumour cell migration and invasion by directly interacting with the α2β1 integrin. In addition, an active sequence of the lumican core protein, called lumcorin, was identified as being responsible for inhibition of melanoma cell migration. Lumican was also shown to exert angiostatic properties by downregulating the proteolytic activity associated with endothelial cell membranes, particularly matrix metalloproteinase (MMP)-14 and MMP-9. Globally, lumican appears to be a potent agent for inhibiting tumour progression rather than tumorigenesis. However, progressive changes in proteoglycans occur in the tumour environment. The complexity and diversity of proteoglycan structure might be responsible for a variety of functions that regulate cell behaviour. Through their core protein and their glycosaminoglycan chains, proteoglycans can interact with growth factors and chemokines. These interactions affect cell signalling, motility, adhesion, growth, and apoptosis. This review summarizes recent data concerning lumican control of tumour progression in different cancers, with a particular focus on its interactions with MMPs and integrins. Its potential therapeutic implications are discussed.

Role of matrix metalloproteinases in epithelial migration

In response to injury, epithelial cells migrate across the denuded tissue to rapidly close the wound and restore barrier, thereby preventing the entry of pathogens and leakage of fluids. Efficient, proper migration requires a range of processes, acting both inside and out of the cell. Among the extracellular responses is the expression of various matrix metalloproteinases (MMPs). Though long thought to ease cell migration simply by breaking down matrix barriers, findings from various models demonstrate that MMPs facilitate (and sometimes repress) cell movement by other means, such as affecting the state of cell-matrix interactions or proliferation. In this Prospect, we review some key data indicting how specific MMPs function via their activity as proteinases to control closure of epithelial wounds.

Matrix metalloproteinase (MMP) and TGF beta 1-stimulated cell migration in skin and cornea wound healing

Cell migration during wound healing is a complex process that involves the expression of a number of growth factors and cytokines. One of these factors, transforming growth factor-beta (TGFbeta) controls many aspects of normal and pathological cell behavior. It induces migration of keratinocytes in wounded skin and of epithelial cells in damaged cornea. Furthermore, this TGFbeta-induced cell migration is correlated with the production of components of the extracellular matrix (ECM) proteins and expression of integrins and matrix metalloproteinases (MMPs). MMP digests ECMs and integrins during cell migration, but the mechanisms regulating their expression and the consequences of their induction remain unclear. It has been suggested that MMP-14 activates cellular signaling processes involved in the expression of MMPs and other molecules associated with cell migration. Because of the manifold effects of MMP-14, it is important to understand the roles of MMP-14 not only the cleavage of ECM but also in the activation of signaling pathways.

MMP-14 mediated MMP-9 expression is involved in TGF-beta1-induced keratinocyte migration

The importance of expression of matrix metalloproteinase (MMP) in keratinocyte migration is well established, but its role remains unclear. Here we investigated the function of MMP-14 in TGF-beta1-induced keratinocyte migration. TGF-beta1 stimulated cell migration and the expression of MMP-2, -9 in HaCaT human keratinocyte cells. When we lowered MMP-14 mRNA with siRNA, cell migration, and MMP-9 expression decreased. Furthermore, the MMP-14 siRNA also reduced activation of JNK in response to TGF-beta1, and a JNK-specific inhibitor decreased both cell migration and MMP-9 expression. Taken together, these results suggest that TGF-beta1-induced HaCaT cell migration is mediated by MMP-14, which regulates MMP-9 expression via JNK signaling.

Human Mast Cell-Derived Gelatinase B (Matrix Metalloproteinase-9) Is Regulated by Inflammatory Cytokines: Role in Cell Migration

Mast cells are key effectors in the pathogenesis of inflammatory and tissue destructive diseases such as rheumatoid arthritis (RA). These cells contain specialized secretory granules loaded with bioactive molecules including cytokines, growth factors, and proteases that are released upon activation. This study investigated the regulation of matrix metalloproteinase MMP-9 (gelatinase B) in human mast cells by cytokines that are known to be involved in the pathogenesis of RA. Immunohistochemical staining of synovial tissue showed abundant expression of MMP-9 by synovial tissue mast cells in patients with RA but not in normal controls. The expression, activity, and production of MMP-9 in mast cells was confirmed by RT-PCR, zymography, and Western blotting using cord blood-derived human mast cells (CB-HMC). Treatment of CB-HMC with TNF-alpha significantly increased the expression of MMP-9 mRNA and up-regulated the activity of MMP-9 in a time- and dose-dependent manner. By contrast, IFN-gamma inhibited MMP-9 mRNA and protein expression. The cytokine-mediated regulation of MMP-9 was also apparent in the human mast cell line (HMC-1) and in mouse bone marrow-derived mast cells. Furthermore, TNF-alpha significantly increased the invasiveness of CB-HMC across Matrigel-coated membranes while the addition of IFN-gamma, rTIMP-1, or pharmacological MMP inhibitors significantly reduced this process. These observations suggest that MMP-9 is not a stored product in mast cells but these cells are capable of producing this enzyme under inflammatory conditions that may facilitate the migration of mast cell progenitors to sites of inflammation and may also contribute to local tissue damage.

Expression of laminin 5 by parental and c-Ha-ras-transformed HaCaT keratinocytes in organotypic cultures

Tumor cells traverse the basement membrane zone and gain access to the underlying mesenchyme to eventually form metastases. Laminin 5 is a major component of the basement membrane and connects keratinocytes at the level of hemidesmosomes to the mesenchyme. Underneath invading tumor cells anti-laminin 5 staining is diminished, and laminin 5 degradation products can stimulate cell migration and epidermal growth factor (EGF) receptor signaling. To investigate laminin 5 expression in parental HaCaT and tumorigenic c-Ha-ras-transformed HaCaT II-4rt keratinocytes, the cells were cultivated under monolayer and organotypic culture conditions. In monolayer cultures, HaCaT and c-Ha-ras-transformed HaCaT II-4rt keratinocytes secreted comparable amounts of laminin 5. After 7 days of organotypic cultures, collagen IV, beta4-integrin, nidogen and laminin 5 were detected along the epithelial-mesenchymal interface of parental HaCaT keratinocytes, while staining for these proteins was patchy or absent in the organotypic cultures with c-Ha-ras-transformed HaCaT II-4rt cells. Immunoblotting analysis confirmed absence of laminin 5 deposition in organotypic cultures of c-Ha-ras-transformed HaCaT II-4rt while the protein was detected in organotypic cultures of HaCaT keratinocytes. Surprisingly, however, the alpha3 and gamma2 laminin chain transcripts were strongly induced in c-Ha-ras-transformed HaCaT II-4rt cells by organotypic culture conditions, indicating that invasive epidermal tumor cells retain high mRNA levels for laminin 5 chains and suggesting an autocrine/paracrine induction of the laminin chain mRNAs. Moreover, as laminin 5 was absent in organotypic cultures of c-Ha-ras-transformed HaCaT II-4rt cells, it suggests immediate degradation of the protein. Degradation products may further contribute to the malignant phenotype by enhancing cellular migration and EGF-receptor activation.

Matrix metalloproteinases of epithelial origin in facial sebum of patients with acne and their regulation by isotretinoin

Acne vulgaris is a skin disorder of the sebaceous follicles, involving hyperkeratinization and perifollicular inflammation. Matrix metalloproteinases (MMP) have a predominant role in inflammatory matrix remodeling and hyperproliferative skin disorders. We investigated the expression of MMP and tissue inhibitors of MMP (TIMP) in facial sebum specimens from acne patients, before and after treatment with isotretinoin. Gelatin zymography and Western-blot analysis revealed that sebum contains proMMP-9, which was decreased following per os or topical treatment with isotretinoin and in parallel to the clinical improvement of acne. Sebum also contains MMP-1, MMP-13, TIMP-1, and TIMP-2, as assessed by ELISA and western blot, but only MMP-13 was decreased following treatment with isotretinoin. The origin of MMP and TIMP in sebum is attributed to keratinocytes and sebocytes, since we found that HaCaT keratinocytes in culture secrete proMMP-2, proMMP-9, MMP-1, MMP-13, TIMP-1, and TIMP-2. SZ95 sebocytes in culture secreted proMMP-2 and proMMP-9, which was also confirmed by microarray analysis. Isotretinoin inhibited the arachidonic acid-induced secretion and mRNA expression of proMMP-2 and -9 in both cell types and of MMP-13 in HaCaT keratinocytes. These data indicate that MMP and TIMP of epithelial origin may be involved in acne pathogenesis, and that isotretinoin-induced reduction in MMP-9 and -13 may contribute to the therapeutic effects of the agent in acne.

Loss of intercellular adhesion activates a transition from low- to high-grade human squamous cell carcinoma

The relationship between loss of intercellular adhesion and the biologic properties of human squamous cell carcinoma is not well understood. We investigated how abrogation of E-cadherin-mediated adhesion influenced the behavior and phenotype of squamous cell carcinoma in 3D human tissues. Cell-cell adhesion was disrupted in early-stage epithelial tumor cells (HaCaT-II-4) through expression of a dominant-negative form of E-cadherin (H-2Kd-Ecad). Three-dimensional human tissue constructs harboring either H-2Kd-Ecad-expressing or control II-4 cells (pBabe, H-2Kd-EcadDeltaC25) were cultured at an air-liquid interface for 8 days and transplanted to nude mice; tumor phenotype was analyzed 2 days and 2 and 4 weeks later. H-2Kd-Ecad-expressing tumors demonstrated a switch to a high-grade aggressive tumor phenotype characterized by poorly differentiated tumor cells that infiltrated throughout the stroma. This high-grade carcinoma revealed elevated cell proliferation in a random pattern, loss of keratin 1 and diffuse deposition of laminin 5 gamma2 chain. When II-4 cell variants were seeded into type I collagen gels as an in vitro assay for cell migration, we found that only E-cadherin-deficient cells detached, migrated as single cells and expressed N-cadherin. Function-blocking studies demonstrated that this migration was matrix metalloproteinase-dependent, as GM-6001 and TIMP-2, but not TIMP-1, could block migration. Gene expression profiles revealed that E-cadherin-deficient II-4 cells demonstrated increased expression of proteases and cell-cell and cell-matrix proteins. These findings showed that loss of E-cadherin-mediated adhesion plays a causal role in the transition from low- to high-grade squamous cell carcinomas and that the absence of E-cadherin is an important prognostic marker in the progression of this disease.

Tumor-stroma interactions: their role in the control of tumor cell invasion

The development and progression of tumors result from the concerted activity not only of tumor cells with neighboring cells e.g., fibroblasts and inflammatory cells. Host-tumor interactions are considered critical in tumor invasion and metastasis. In vitro studies as well as established in vivo models have analysed the reciprocal effects of tumor-host interactions for the tumor invasion process. These studies have shown that modifications in the extracellular matrix composition surrounding the tumors as well as alterations in the expression of tumor cell receptors or in the expression of growth factors/cytokines and proteases, are critical regulators of a developing tumor. We shortly review the most important and well characterized mechanisms involved in the progression of tumor cells through tissues, especially those participating in cellular communication, cell adhesion, and proteolysis.

Inhibition of basement membrane formation by a nidogen-binding laminin gamma1-chain fragment in human skin-organotypic cocultures

Basement membranes generally determine different tissue compartments in complex organs, such as skin, playing not only an important structural but also a regulatory role. We have previously demonstrated the formation of a regular basement membrane in organotypic three-dimensional (3D)-cocultures of human skin keratinocytes and fibroblasts by indirect immunofluorescence and transmission electron microscopy. In this assembly process, cross-linking of type IV collagen and the laminin gamma1 chain by nidogen is considered a crucial step. For a functional proof, we have now competitively inhibited nidogen binding to laminin in 3D-cocultures with a recombinant laminin gamma1 fragment (gamma1III3-5 module) spanning this binding site. Repeated treatment abolished the deposition of nidogen at the epithelial-matrix interface but also greatly perturbed the presence of other matrix constituents such as laminin and perlecan. This effect persisted over the entire observation period of 10 to 21 days. In contrast, some components of the basement membrane zone were only moderately affected, with the laminin-5 isoform (gamma2 chain), type IV collagen and integrin alpha6ss4 still showing a distinct staining at their regular position, when seen by light microscopy. Furthermore, epidermal morphology and differentiation remained largely normal as indicated by the regular location of keratins K1/K10 and also of late differentiation markers. Ultrastructural examination demonstrated that the gamma1 fragment completely suppressed any formation of basement membrane structures (lamina densa) and also of hemidesmosomal adhesion complexes. As a consequence of hemidesmosome deficiency, keratin filament bundles were not attached to the ventral basal cell aspect. These findings were further substantiated by immuno-electron microscopy, revealing either loss or drastic reduction and dislocation of basement membrane and hemidesmosomal components. Taken together, in this simplified human skin model (representing a 'closed system') a functional link has been demonstrated between compound structures of the extra- and intracellular space at the junctional zone providing a basis to interfere at distinct points and in a controlled fashion.

Mammalian tolloid metalloproteinase, and not matrix metalloprotease 2 or membrane type 1 metalloprotease, processes laminin-5 in keratinocytes and skin

Laminin-5, a major adhesive ligand for epithelial cells, undergoes processing of its gamma2 and alpha3 chains. This study investigated the mechanism of laminin-5 processing by keratinocytes. BI-1 (BMP-1 isoenzyme inhibitor-1), a selective inhibitor of a small group of astacin-like metalloproteinases, which includes bone morphogenetic protein 1 (BMP-1), mammalian Tolloid (mTLD), mammalian Tolloid-like 1 (mTLL-1), and mammalian Tolloid-like 2 (mTLL-2), inhibited the processing of laminin-5 gamma2 and alpha3 chains in keratinocyte cultures in a dose-dependent manner. In a proteinase survey, all BMP-1 isoenzymes processed human laminin-5 gamma2 and alpha3 chains to 105- and 165-kDa fragments, respectively. In contrast, MT1-MMP and MMP-2 did not cleave the gamma2 chain of human laminin-5 but processed the rat laminin gamma2 chain to an 80-kDa fragment. An immunoblot and quantitative PCR survey of the BMP-1 isoenzymes revealed expression of mTLD in primary keratinocyte cultures but little or no expression of BMP-1, mTLL-1, or mTLL-2. mTLD was shown to cleave the gamma2 chain at the same site as the previously identified BMP-1 cleavage site. In addition, mTLD/BMP-1 null mice were shown to have deficient laminin-5 processing. Together, these data identify laminin-5 as a substrate for mTLD, suggesting a role for laminin-5 processing by mTLD in the skin.

Inhibition of matrix metalloproteinase-14 in osteosarcoma cells by clodronate

BACKGROUND

Bisphosphonates reduce the bone metastasis formation and angiogenesis but the exact molecular mechanisms involved are unclear. Progelatinase A (proMMP-2; 78 KDa) is activated up during the tumor spread and metastasis by a cell surface-associated matrix metalloproteinase (membrane-type matrix metalloproteinase [MT1-MMP] or MMP-14).

MATERIAL AND METHODS

We evaluated the effects of a bisphosphonate (clodronate) on MT1-MMP mRNA expression and protein production, catalytic activity and proteolytic activation of proMMP-2 by cultured human MG-63 osteosarcoma cells.

RESULTS

Clodronate, at therapeutically attainable noncytotoxic concentrations, dose-dependently inhibited phorbol myristic acetate (PMA)-induced proteolytic activation of proMMP-2 by human MG-63 osteosarcoma cells. Clodronate also downregulated the PMA-induced expression of MT1-MMP mRNA and protein production in human MG-63 osteosarcoma cells, as evidenced by Northern analysis and fluorescent immunohistochemistry. Furthermore, clodronate inhibited directly and dose-dependently MT1-MMP activity, and the MT1-MMP inhibition by clodronate was reduced in the presence of an increased (5 mM) Ca(2+) concentrations when compared to physiological (1 mM) Ca(2+) concentrations.

CONCLUSION

We conclude that (1) the extracellular/cell-associated mechanism of bisphosphonate involves inhibition of MT1-MMP catalytic activity eventually by chelation, and that (2) intracellular mechanism involves downregulation of induced MT1-MMP mRNA and protein expression. The inhibition and downregulation of MT1-MMP by clodronate can be related to their ability to reduce MG-63 osteosarcoma cell invasion and spread. These findings may, at least in part, explain at molecular level the antitumor and antibone resorption activities of clodronate observed in clinical studies.

Calcium regulation of matrix metalloproteinase-mediated migration in oral squamous cell carcinoma cells

Activation of matrix metalloproteinase 2 (MMP-2) has been shown to play a significant role in the behavior of cancer cells, affecting both migration and invasion. The activation process requires multimolecular complex formation involving pro-MMP-2, membrane type 1-MMP (MT1-MMP), and tissue inhibitor of metalloproteinases-2 (TIMP-2). Because calcium is an important regulator of keratinocyte function, we evaluated the effect of calcium on MMP regulation in an oral squamous cell carcinoma line (SCC25). Increasing extracellular calcium (0.09-1.2 mm) resulted in a dose-dependent increase in MT1-MMP-dependent pro-MMP-2 activation. Despite the requirement for MT1-MMP in the activation process, no changes in MT1-MMP expression, cell surface localization, or endocytosis were apparent. However, increased generation of the catalytically inactive 43-kDa MT1-MMP autolysis product and decline in the TIMP-2 levels in conditioned media were observed. The decrease in TIMP-2 levels in the conditioned media was prevented by a broad spectrum MMP inhibitor, suggesting that calcium promotes recruitment of TIMP-2 to MT1-MMP on the cell surface. Despite the decline in soluble TIMP-2, no accumulation of TIMP-2 in cell lysates was seen. Blocking TIMP-2 degradation with bafilomycin A1 significantly increased cell-associated TIMP-2 levels in the presence of high calcium. These data suggest that the decline in TIMP-2 is because of increased calcium-mediated MT1-MMP-dependent degradation of TIMP-2. In functional studies, increasing calcium enhanced MMP-dependent cellular migration on laminin-5-rich matrix using an in vitro colony dispersion assay. Taken together, these results suggest that changes in extracellular calcium can regulate post-translational MMP dynamics and thus affect the cellular behavior of oral squamous cell carcinoma.

Membrane type 1 matrix metalloproteinase regulates cellular invasiveness and survival in cutaneous epidermal cells

Membrane type 1 matrix metalloproteinase is a member of the membrane-anchored matrix metalloproteinase family and is involved in tissue remodeling events ranging from tumor invasion and angiogenesis to growth and development. We sought to clarify the role of membrane type 1 matrix metalloproteinase in cutaneous epidermal cells using anti-sense cDNA expression in human keratinocytes. Modulation of membrane type 1 matrix metalloproteinase transcript and protein levels was achieved via retroviral expression of a 5' 1.4 kb anti-sense membrane type 1 matrix metalloproteinase construct and a 3.4 kb full-length sense membrane type 1 matrix metalloproteinase construct in primary and immortalized keratinocytes and SCC-25 cells. Maximal reductions were observed 48-72 h after transduction with 1.4 kb anti-sense membrane type 1 matrix metalloproteinase construct that correlated with significant decreased pro-matrix metalloproteinase-2 activation. Functionally, we found decreased cell migration, reduced cellular proliferation, and increased apoptotic nuclear fragmentation after 1.4 kb anti-sense membrane type 1 matrix metalloproteinase construct expression. Our findings suggest a role for membrane type 1 matrix metalloproteinase in human cutaneous epidermal cell invasion and survival mechanisms in vivo.

Cumulative influence of matrix metalloproteinase-1 and -2 in the migration of melanoma cells within three-dimensional type I collagen lattices

During melanoma progression, migrating cells must cross human dermis, a type I collagen-rich tissue. We have show that MMP-1 and MMP-2 act in a cumulative manner in the in vitro invasion of a three-dimensional type I collagen matrix by melanoma cells. Two melanoma cell lines (M1Dor and M3Da) previously reported to secrete proMMP-2 in a direct relationship with their tumorigenic potential into nude mice were used (F. Capon et al., 1999, Clin. Exp. Metastasis 17, 463-469). The highly tumorigenic cell line (M3Da) displayed a five-fold faster migration rate in type I collagen matrix, compared to its lower tumorigenic counterpart (M1Dor). In parallel, activation of proMMP-2 was evidenced in M3Da- but not M1Dor-populated collagen lattices. Such enzyme activation was associated with a significant decrease in TIMP-2 and TIMP-1 production. Agents known to interfere with proMMP-2 activation, i.e., excess TIMP-2, furin convertase inhibitor, and alphavbeta3 blocking antibody, reduced by 30-40% the type I collagen invasive capacity of M3Da cells. By comparison, batimastat, a wide-spectrum MMP inhibitor, exhibited a more pronounced inhibitory effect (>70%). It suggested that other collagenases than MMP-2 could participate in type I collagen invasion. Collagenase-3 (MMP-13) was produced at low levels by melanoma cells whatever the cell culture conditions. In contrast, M3Da and M1Dor cells secreted collagenase-1 (MMP-1) following 48 h of culture on plastic dishes. Growing melanoma cells in type I collagen gel did not modify enzyme production, but induced proMMP-1 activation in M3Da but not M1Dor cell-populated lattices. Blocking the plasmin-mediated proMMP-1 activation by aprotinin inhibited type I collagen gel invasion by 30%. Since the combination of aprotinin and furin convertase inhibitor reduced collagen invasiveness by melanoma cells to a level comparable to that attained with batimastat, we conclude that both MMP-2 and MMP-1 are involved in such tissue invasion.