Membrane Type 1 Matrix Metalloproteinase Regulates Collagen-Dependent Mitogen-Activated Protein/Extracellular Signal-Related Kinase Activation and Cell Migration

Cytoplasmic Tail of MT1-MMP: A Hub of MT1-MMP Regulation and Function

MT1-MMP (MMP-14) is a multifunctional protease that regulates ECM degradation, activation of other proteases, and a variety of cellular processes, including migration and viability in physiological and pathological contexts. Both the localization and signal transduction capabilities of MT1-MMP are dependent on its cytoplasmic domain that constitutes the final 20 C-terminal amino acids, while the rest of the protease is extracellular. In this review, we summarize the ways in which the cytoplasmic tail is involved in regulating and enacting the functions of MT1-MMP. We also provide an overview of known interactors of the MT1-MMP cytoplasmic tail and the functional significance of these interactions, as well as further insight into the mechanisms of cellular adhesion and invasion that are regulated by the cytoplasmic tail.

Concanavalin A as a promising lectin-based anti-cancer agent: the molecular mechanisms and therapeutic potential

Concanavalin A (ConA), the most studied plant lectin, has been known as a potent anti-neoplastic agent for a long time. Since initial reports on its capacity to kill cancer cells, much attention has been devoted to unveiling the lectin's exact molecular mechanism. It has been revealed that ConA can bind to several receptors on cancerous and normal cells and modulate the related signaling cascades. The most studied host receptor for ConA is MT1-MMP, responsible for most of the lectin's modulations, ranging from activating immune cells to killing tumor cells. In this study, in addition to studying the effect of ConA on signaling and immune cell function, we will focus on the most up-to-date advancements that unraveled the molecular mechanisms by which ConA can induce autophagy and apoptosis in various cancer cell types, where it has been found that P73 and JAK/STAT3 are the leading players. Moreover, we further discuss the main signaling molecules causing liver injury as the most significant side effect of the lectin injection. Altogether, these findings may shed light on the complex signaling pathways controlling the diverse responses created via ConA treatment, thereby modulating these complex networks to create more potent lectin-based cancer therapy.

Analysis of the expression and prognostic value of MT1-MMP, β1-integrin and YAP1 in glioma

Increased expression of membrane type 1-matrix metalloproteinase (MT1-MMP/MMP14) is associated with the development of many cancers. MT1-MMP may promote the entry of yes-associated protein1 (YAP1) into the nucleus by regulating the regulation of β1-integrin. The purpose of this study was to investigate the effects of MT1-MMP, β1-integrin and YAP1 on the prognosis of gliomas. The expression of proteins was detected by bioinformatics and immunohistochemistry. The relationship between three proteins and clinicopathological parameters was analyzed by the χ² test. Survival analysis was used to investigate the effects of three proteins on prognosis. The results showed that high expressions of MT1-MMP, β1-integrin and YAP1 were found in glioblastoma (GBM) compared with lower-grade glioma (LGG). There was a significantly positive correlation between MT1-MMP and β1-integrin (r = 0.387), MT1-MMP and YAP1 (r = 0.443), β1-integrin and YAP1 (r = 0.348). Survival analysis showed that patients with overexpression of MT1-MMP, β1-integrin and YAP1 had a worse prognosis. YAP1 expression was the independent prognostic factor for progression-free survival (PFS). There was a statistical correlation between the expression of MT1-MMP and YAP1 and isocitrate dehydrogenase 1 (IDHl) mutation. Thus, this study suggested that MT1-MMP, β1-integrin and YAP1, as tumor suppressors, are expected to be promising prognostic biomarkers and therapeutic targets for glioma patients.

TGF-β1 facilitates MT1-MMP-mediated proMMP-9 activation and invasion in oral squamous cell carcinoma cells

Matrix metalloproteinase (MMP)-2 and MMP-9, also known as gelatinases or type IV collagenases, are recognized as major contributors to the proteolytic degradation of extracellular matrix during tumor invasion. Latent MMP-2 (proMMP-2) is activated by membrane type 1 MMP (MT1-MMP) on the cell surface of tumor cells. We previously reported that cell-bound proMMP-9 is activated by the MT1-MMP/MMP-2 axis in HT1080 cells treated with concanavalin A in the presence of exogenous proMMP-2. However, the regulatory mechanism of proMMP-9 activation remains largely unknown. Transforming growth factor (TGF)-β1 is frequently overexpressed in tumor tissues and is associated with tumor aggressiveness and poor prognosis. In this study, we examined the role of TGF-β1 on MT1-MMP-mediated proMMP-9 activation using human oral squamous cell carcinoma cells. TGF-β1 significantly increased the expression of MMP-9. By adding exogenous proMMP-2, TGF-β1-induced proMMP-9 was activated during collagen gel culture, which was suppressed by the inhibition of TGF-β1 signaling or MT1-MMP activity. This MT1-MMP-mediated proMMP-9 activation was needed to facilitate TGF-β1-induced cell invasion into collagen gel. Thus, TGF-β1 may facilitate MT1-MMP-mediated MMP-9 activation and thereby stimulate invasion of tumor cells in collaboration with MT1-MMP and MMP-2.

Lumican Inhibits In Vivo Melanoma Metastasis by Altering Matrix-Effectors and Invadopodia Markers

It was reported that lumican inhibits the activity of metalloproteinase MMP-14 and melanoma cell migration in vitro and in vivo. Moreover, Snail triggers epithelial-to-mesenchymal transition and the metastatic potential of cancer cells. Therefore, the aim of this study was to examine the effect of lumican on Mock and Snail overexpressing melanoma B16F1 cells in vivo. Lung metastasis was analyzed after intravenous injections of Mock-B16F1 and Snail-B16F1 cells in Lum+/+ and Lum-/- mice. At day 14, mice were sacrificed, and lungs were collected. The number of lung metastatic nodules was significantly higher in mice injected with Snail-B16F1 cells as compared to mice injected with Mock-B16F1 cells confirming the pro-metastatic effect of Snail. This effect was stronger in Lum-/- mice as compared to Lum+/+, suggesting that endogenous lumican of wild-type mice significantly inhibits metastasis to lungs. Scanning electron and confocal microscopy investigations demonstrated that lumican inhibits the development of elongated cancer cell phenotypes which are known to develop invadopodia releasing MMPs. Moreover, lumican was shown to affect the expression of cyclin D1, cortactin, vinculin, hyaluronan synthase 2, heparanase, MMP-14 and the phosphorylation of FAK, AKT, p130 Cas and GSK3α/β. Altogether, these data demonstrated that lumican significantly inhibits lung metastasis in vivo, as well as cell invasion in vitro, suggesting that a lumican-based strategy targeting Snail-induced metastasis could be useful for melanoma treatment.

Nuclear factor-κB plays an important role in Tamarixetin-mediated inhibition of matrix metalloproteinase-9 expression

Flavonoids possess a broad spectrum of pharmacological properties, including anti-cancer, anti-oxidant and immunomodulatory activities. The current study explored the potential of some less-studied flavonoids in inhibiting Matrix Metalloproteinase-9 (MMP-9), a prominent biomarker, upregulated in a variety of cancers and known to promote migration and invasion of cancer cells. Amongst these, Tamarixetin, a naturally occurring flavonoid derivative of Quercetin, demonstrated significant dose-dependent inhibition of MMP-9 expression. Furthermore, a substantial inhibition of migration, invasion and clonogenic potential of HT1080 cells was also observed in the presence of Tamarixetin, which further suggests its role as a potential anti-cancer agent. It is noteworthy that Tamarixetin inhibits nuclear translocation as well the activity of nuclear factor kappa B (NFκB), both of which are functions essential for the activation of MMP-9 in promoting tumorigenesis. Additionally, the endogenous regulators of MMP-9 that tightly control its activity were also modulated by Tamarixetin, as evident from the 1.9 fold increase in the expression of Tissue Inhibitor of Metalloproteinase-1 (TIMP-1), with a concomitant 2.2 fold decrease in Matrix Metalloproteinase-14 (MMP-14) expression. The results obtained were further corroborated in three dimensional (3D) tumor models, which showed significant inhibition of MMP-9 activity as well as reduced invasive potential in the presence of Tamarixetin. Taken together, our observations demonstrate for the first time, the anti-invasive potential of Tamarixetin in cancer cells, indicating its possible use as a template for novel therapeutic applications.

Coronin 1C inhibits melanoma metastasis through regulation of MT1-MMP-containing extracellular vesicle secretion

Coronin 1C is overexpressed in multiple tumors, leading to the widely held view that this gene drives tumor progression, but this hypothesis has not been rigorously tested in melanoma. Here, we combined a conditional knockout of Coronin 1C with a genetically engineered mouse model of PTEN/BRAF-driven melanoma. Loss of Coronin 1C in this model increases both primary tumor growth rates and distant metastases. Coronin 1C-null cells isolated from this model are more invasive in vitro and produce more metastatic lesions in orthotopic transplants than Coronin 1C-reexpressing cells due to the shedding of extracellular vesicles (EVs) containing MT1-MMP. Interestingly, these vesicles contain melanosome markers suggesting a melanoma-specific mechanism of EV release, regulated by Coronin 1C, that contributes to the high rates of metastasis in melanoma.

Simple and cost-effective assay for isolating invasive living cells

A modified invasion assay using a three-dimensional collagen gel was developed that enables isolation of invasive living cells; it was named the invading cell trapping (iCT) assay. A small cell strainer consisting of a nylon mesh with 40-μm² pores was used, and collagen gel layers formed across the membrane. Test cells were seeded in the lower gel layer and invasive cells were attracted upward and trapped in the upper gel. After incubation, the collagen gel layers in cell strainers were easily separated and living cells in the gel were counted and analyzed. An advantage of the iCT assay is that it can capture living invasive cells in the upper gel while leaving noninvasive ones in the lower layer. Further enrichment of the two cell populations can be achieved by repeating the assay. Thus, the iCT assay allows comparative analysis of invasive versus noninvasive cells.

Screening, Identification, and Characterization of an Affinity Peptide Specific to MT1-MMP and Its Application in Tumor Imaging

Membrane type-1 matrix metalloproteinase (MT1-MMP) plays a crucial role in many physiological and pathological processes, especially in tumor invasion and metastasis. Bioimaging of this key molecule may find wide usage in various applications. MT-loop is a unique sequence of MT1-MMP and locates in the surface of the protein. In our previous studies, AF7p, an affinity peptide that targeting the MT-loop domain of MT1-MMP, was identified by screening a phage display (Ph.D.) peptide library. However, the target of AF7p is a synthetic sequence which lacked native conformation of the MT-loop region; thus, the binding affinity and specificity in reality may not be optimal. In this study, we considered the 3-dimensional (3-D) conformation of the MT-loop area in the MT1-MMP molecule and designed a novel strategy to screen the Ph.D. peptide library. The peptide we obtained showed a better binding affinity to WT-MT1-MMP than AF7p as observed through enzyme-linked immunosorbent assay (ELISA) and biolayer interferometry (BLI). The new peptide labeled and attached MT1-MMP expression cell lines HT1080 and did not show any toxicity to cells. Furthermore, for in vivo imaging, HT1080 tumor-bearing mice with higher MT1-MMP expression accumulated more Cy5.5-HS7 than mice with MT1-MMP low-expression cell lines A549 at tumor sites, and the half-life of HS7 was longer than that of AF7p, as confirmed by ex vivo imaging of the main organs. These results suggest the feasibility of using the subtraction biopanning strategy to screen the affinity peptide targeting MT-loop regions and HS7 is a superior probe for noninvasively imaging MT1-MMP expression in MT1-MMP-positive tumor models. It provides impetus for further studies to use HS7 in early diagnosis of tumors and in peptide-mediated drugs.

The role of miR-497-5p in myofibroblast differentiation of LR-MSCs and pulmonary fibrogenesis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal fibrotic lung disease characterized by profound changes in stem cell differentiation, epithelial cell phenotypes and fibroblast proliferation. In our study, we found that miR-497-5p was significantly upregulated both during myofibroblast differentiation of lung resident mesenchymal stem cells (LR-MSCs) and in the lung tissues of a pulmonary fibrosis model. In addition, as determined by luciferase assays and Western blot analysis, reversion-inducing cysteine-rich protein with kazal motifs (Reck) was identified to be one of the target genes of miR-497-5p, and Reck could suppress the expression of matrix metalloproteinase-2 (Mmp2) and Mmp9, which could activate latent transforming growth factor-β1 (TGF-β1). To test the potential therapeutic significance of this miRNA, we modulated the expression of miR-497-5p in LR-MSCs and relevant animal models. The results demonstrated that upregulation of miR-497-5p could induce LR-MSCs to differentiate into myofibroblasts and promote pulmonary fibrogenesis, while inhibition of its expression could effectively retard these processes. In conclusion, our work supports that controlling pulmonary fibrogenesis via inhibition of miR-497-5p expression may provide a potential therapeutic strategy for IPF.

FAK, talin and PIPKIγ regulate endocytosed integrin activation to polarize focal adhesion assembly

Integrin endocytic recycling is critical for cell migration, yet how recycled integrins assemble into new adhesions is unclear. By synchronizing endocytic disassembly of focal adhesions (FAs), we find that recycled integrins reassemble FAs coincident with their return to the cell surface and dependent on Rab5 and Rab11. Unexpectedly, endocytosed integrins remained in an active but unliganded state in endosomes. FAK and Src kinases co-localized with endocytosed integrin and were critical for FA reassembly by regulating integrin activation and recycling, respectively. FAK sustained the active integrin conformation by maintaining talin association with Rab11 endosomes in a type I phosphatidylinositol phosphate kinase (PIPKIγ)-dependent manner. In migrating cells, endocytosed integrins reassembled FAs polarized towards the leading edge, and this polarization required FAK. These studies identify unanticipated roles for FA proteins in maintaining endocytosed integrin in an active conformation. We propose that the conformational memory of endocytosed integrin enhances polarized reassembly of FAs to enable directional cell migration.

Membrane Type 1 Matrix Metalloproteinase Regulates Monocyte Migration and Collagen Destruction in Tuberculosis

Tuberculosis (TB) remains a global pandemic and drug resistance is rising. Multicellular granuloma formation is the pathological hallmark of Mycobacterium tuberculosis infection. The membrane type 1 matrix metalloproteinase (MT1-MMP or MMP-14) is a collagenase that is key in leukocyte migration and collagen destruction. In patients with TB, induced sputum MT1-MMP mRNA levels were increased 5.1-fold compared with matched controls and correlated positively with extent of lung infiltration on chest radiographs (r = 0.483; p < 0.05). M. tuberculosis infection of primary human monocytes increased MT1-MMP surface expression 31.7-fold and gene expression 24.5-fold. M. tuberculosis-infected monocytes degraded collagen matrix in an MT1-MMP-dependent manner, and MT1-MMP neutralization decreased collagen degradation by 73%. In human TB granulomas, MT1-MMP immunoreactivity was observed in macrophages throughout the granuloma. Monocyte-monocyte networks caused a 17.5-fold increase in MT1-MMP surface expression dependent on p38 MAPK and G protein-coupled receptor-dependent signaling. Monocytes migrating toward agarose beads impregnated with conditioned media from M. tuberculosis-infected monocytes expressed MT1-MMP. Neutralization of MT1-MMP activity decreased this M. tuberculosis network-dependent monocyte migration by 44%. Taken together, we demonstrate that MT1-MMP is central to two key elements of TB pathogenesis, causing collagen degradation and regulating monocyte migration.

Discoidin domain receptor 1 controls linear invadosome formation via a Cdc42-Tuba pathway

In tumor cells, the collagen receptor DDR1 collaborates with Cdc42 and its guanine exchange factor Tuba to promote linear invadosome formation and increase their matrix-invading activity.

Accumulation of type I collagen fibrils in tumors is associated with an increased risk of metastasis. Invadosomes are F-actin structures able to degrade the extracellular matrix. We previously found that collagen I fibrils induced the formation of peculiar linear invadosomes in an unexpected integrin-independent manner. Here, we show that Discoidin Domain Receptor 1 (DDR1), a collagen receptor overexpressed in cancer, colocalizes with linear invadosomes in tumor cells and is required for their formation and matrix degradation ability. Unexpectedly, DDR1 kinase activity is not required for invadosome formation or activity, nor is Src tyrosine kinase. We show that the RhoGTPase Cdc42 is activated on collagen in a DDR1-dependent manner. Cdc42 and its specific guanine nucleotide-exchange factor (GEF), Tuba, localize to linear invadosomes, and both are required for linear invadosome formation. Finally, DDR1 depletion blocked cell invasion in a collagen gel. Altogether, our data uncover an important role for DDR1, acting through Tuba and Cdc42, in proteolysis-based cell invasion in a collagen-rich environment.

Vinculin negatively regulates transcription of MT1-MMP through MEK/ERK pathway

Vinculin regulates a variety of cellular functions partly through stabilization of tumor suppressor PTEN. In order to study the role of vinculin in tumor progression other than PTEN stabilization, vinculin was knocked down in PTEN-deficient squamous cell carcinoma HSC-4 cells. Knockdown of vinculin induced phenotypical change by reducing cell-cell and cell-extracellular matrix adhesions, and enhanced MT1-MMP expression at transcription level and subsequent cell migration. Up-regulation of MT1-MMP transcription by vinculin knockdown was abrogated by ERK inhibition. These results suggest that vinculin negatively regulates malignant phenotype of tumor cells including MT1-MMP transcription through MEK/ERK pathway.

Icotinib inhibits the invasion of Tca8113 cells via downregulation of nuclear factor κB-mediated matrix metalloproteinase expression

Icotinib is an epidermal growth factor receptor tyrosine kinase inhibitor, which has been revealed to inhibit proliferation in tumor cells. However, the effect of icotinib on cancer cell metastasis remains to be explained. This study examines the effect of icotinib on the migration and invasion of squamous cells of tongue carcinoma (Tca8113 cells) in vitro. The results of the Boyden chamber invasion assay demonstrated that icotinib reduced cell invasion, suppressed the protein levels of matrix metalloproteinases (MMPs), MMP-2 and MMP-9, and increased the expression of tissue inhibitor of metalloproteinase-1. In addition, icotinib was found to significantly decrease the protein levels of nuclear factor κB (NF-κB) p65, which suggested that icotinib inhibits NF-κB activity. Furthermore, treatment with the NF-κB inhibitor, pyrrolidine dithiocarbamate, suppressed cell invasion and MMP-2 expression. These results suggested that icotinib inhibits the invasion of Tca8113 cells by downregulating MMP via the inactivation of the NF-κB signaling pathways.

Membrane-type 1 matrix metalloproteinase regulates fibronectin assembly and N-cadherin adhesion

Fibronectin matrix formation requires the increased cytoskeletal tension generated by cadherin adhesions, and is suppressed by membrane-type 1 matrix metalloproteinase (MT1-MMP). In a co-culture of Rat1 fibroblasts and MT1-MMP-silenced HT1080 cells, fibronectin fibrils extended from Rat1 to cell-matrix adhesions in HT1080 cells, and N-cadherin adhesions were formed between Rat1 and HT1080 cells. In control HT1080 cells contacting with Rat1 fibroblasts, cell-matrix adhesions were formed in the side away from Rat1 fibroblasts, and fibronectin assembly and N-cadherin adhesions were not formed. The role of N-cadherin adhesions in fibronectin matrix formation was studied using MT1-MMP-silenced HT1080 cells. MT1-MMP knockdown promoted fibronectin matrix assembly and N-cadherin adhesions in HT1080 cells, which was abrogated by double knockdown with either integrin β1 or fibronectin. Conversely, inhibition of N-cadherin adhesions by its knockdown or treatment with its neutralizing antibody suppressed fibronectin matrix formation in MT1-MMP-silenced cells. These results demonstrate that fibronectin assembly initiated by MT1-MMP knockdown results in increase of N-cadherin adhesions, which are prerequisite for further fibronectin matrix formation.

The role of matrix metalloproteinase in the intimal sarcoma-like cells derived from endarterectomized tissues from a chronic thromboembolic pulmonary hypertension patient

Sarcoma-like cells (SCLs) were derived from endarterectomized tissue of a single chronic thromboembolic pulmonary hypertension (CTEPH) patient during incubation of those thrombi at second passage as described at our previous report. These cells had malignant potential, with an increased expression of matrix metalloproteinase-14 (MMP-14), leading to tumor emboli within pulmonary arteries in in vivo studies. The purpose of this study was to perform a more detailed evaluation of the characteristics of SCLs, and to elucidate the role of the increased expression of MMP-14 expression in the growth and death of these cells. In order to elucidate the characteristics of SCLs and to confirm the protein expression of MMP-14, three-dimentional culture, invasion assays, a Western blot analysis and immunohistochemical studies were performed. To examine the role of MMP-14 in tumorigenesis, the metalloproteinase inhibitor, batimastat, was administered to SCID mice which were subcutaneously injected with SCLs. Those mice were sacrificed on day 14 and the tumor volume was evaluated. A Western blot analysis showed the increased expression of MMP-14 in comparison to the expression in lung adenocarcinoma cells (A549). Immunohistochemistry showed that SCLs were positive for vimentin, MMP-14, MMP-2 and CD44. However, endothelial markers, such as CD31 and von Willebrand factor (vWF), were negative. The in vivo studies demonstrated that batimastat could suppress the growth of the subcutaneous tumors formed by the SCLs. This study suggested that MMPs had critical roles on the pathological activities of SCLs and that batimastat might have anti-proliferative and anti-invasive effects on these cells.

CD26 expression on T-anaplastic large cell lymphoma (ALCL) line Karpas 299 is associated with increased expression of versican and MT1-MMP and enhanced adhesion

Background

CD26/dipeptidyl peptidase IV (DPPIV) is a multifunctional membrane protein with a key role in T-cell biology and also serves as a marker of aggressive cancers, including T-cell malignancies.

Methods

Versican expression was measured by real-time RT-PCR and Western blots. Gene silencing of versican in parental Karpas 299 cells was performed using transduction-ready viral particles. The effect of versican depletion on surface expression of MT1-MMP was monitored by flow cytometry and surface biotinylation. CD44 secretion/cleavage and ERK (1/2) activation was followed by Western blotting. Collagenase I activity was measured by a live cell assay and in vesicles using a liquid-phase assay. Adhesion to collagen I was quantified by an MTS assay.

Results

Versican expression was down-regulated in CD26-depleted Karpas 299 cells compared to the parental T-ALCL Karpas 299 cells. Knock down of versican in the parental Karpas 299 cells led to decreased MT1-MMP surface expression as well as decreased CD44 expression and secretion of the cleaved form of CD44. Parental Karpas 299 cells also exhibited higher collagenase I activity and greater adhesion to collagenase I than CD26-knockdown or versican-knockdown cells. ERK activation was also highest in parental Karpas 299 cells compared to CD26-knockdown or versican-knockdown clones.

Conclusions

Our data indicate that CD26 has a key role in cell adhesion and invasion, and potentially in tumorigenesis of T-cell lines, through its association with molecules and signal transduction pathways integral to these processes.

MT-LOOP-dependent localization of membrane type I matrix metalloproteinase (MT1-MMP) to the cell adhesion complexes promotes cancer cell invasion

Localization of membrane type I matrix metalloproteinase (MT1-MMP) to the leading edge is thought to be a crucial step during cancer cell invasion. However, its mechanisms and functional impact on cellular invasion have not been clearly defined. In this report, we have identified the MT-LOOP, a loop region in the catalytic domain of MT1-MMP ((163)PYAYIREG(170)), as an essential region for MT1-MMP to promote cellular invasion. Deletion of the MT-LOOP effectively inhibited functions of MT1-MMP on the cell surface, including proMMP-2 activation, degradation of gelatin and collagen films, and cellular invasion into a collagen matrix. This is not due to loss of the catalytic function of MT1-MMP but due to inefficient localization of the enzyme to β1-integrin-rich cell adhesion complexes at the plasma membrane. We also found that an antibody that specifically recognizes the MT-LOOP region of MT1-MMP (LOOPAb) inhibited MT1-MMP functions, fully mimicking the phenotype of the MT-LOOP deletion mutant. We therefore propose that the MT-LOOP region is an interface for molecular interactions that mediate enzyme localization to cell adhesion complexes and regulate MT1-MMP functions. Our findings have revealed a novel mechanism regulating MT1-MMP during cellular invasion and have identified the MT-LOOP as a potential exosite target region to develop selective MT1-MMP inhibitors.

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.

MT1-MMP prevents growth inhibition by three dimensional fibronectin matrix

The extracellular microenvironment plays a key role in regulation of cellular functions and growth control. We show here that membrane-type 1 matrix metalloproteinase (MT1-MMP) acts as a growth promoter in confluent culture. When MT1-MMP was silenced in HT1080 fibrosarcoma cells, cells created three dimensional (3D) fibronectin matrix in a confluent culture, and growth of cells embedded within it was retarded. Formation of 3D fibronectin matrix initiated by MT1-MMP silencing was impeded by knockdown of either FN or integrin β₁, which resulted in restoration of cell growth. When cells in 3D fibronectin matrix were treated with integrin β₁ inhibitory antibody, cells underwent S phase entry. These results suggest that MT1-MMP prevents growth suppression by 3D fibronectin matrix, which is mediated through integrin β₁.

MT1-MMP modulates bFGF-induced VEGF-A expression in corneal fibroblasts

The cornea is physiologically avascular. Following a corneal injury, wound healing often proceeds without neovascularization (NV); however, corneal NV may be induced during wound healing in certain inflammatory, infectious, degenerative, and traumatic states. Such states disrupt the physiologic balance between pro-angiogenic and antiangiogenic mediators, favoring angiogenesis. Contributors to such states are matrix metalloproteinases (MMPs), which are key factors in both extracellular matrix remodeling and angiogenesis. Similarly, vascular endothelial growth factor A (VEGF-A) and basic fibroblast growth factor (bFGF) exert pro-angiogenic effects. Here, we elaborate on the facilitative role of MMPs-specifically Membrane Type 1 MMP (MT1-MMP, MMP14)-in corneal NV. Additionally, we provide new insight into the signaling relating to MT1-MMP, Ras, and ERK in the bFGF-induced VEGF-A expression pathways within the corneal fibroblasts.

MT1-MMP expression level status dictates the in vitro action of lupeol on inflammatory biomarkers MMP-9 and COX-2 in medulloblastoma cells

Local inflammation-induced extracellular matrix structural changes are a prerequisite to neoplastic invasion by pediatric intracranial tumors. Accordingly, increased expression of matrix metalloproteinases MMP-2 and MMP-9, two inflammation-induced matrix metalloproteinases (MMPs), may further aid the transformed cells either to infiltrate adjacent tissues or to enter the peripheral circulation. In the context of neuroinflammation, MMP-9 has been linked to processes such as blood-brain barrier opening and invasion of neural tissue by blood-derived immune cells. Given its reported anti-inflammatory and anticancer properties, we investigated the in vitro pharmacological effects of lupeol, a diet-derived triterpenoid, on MMP-9 and cyclooxygenase (COX)-2 expressions in a pediatric medulloblastoma DAOY cell line model. Lupeol was unable to inhibit the increased MMP-9 and COX-2 expression in phorbol 12-myristate 13-acetate (PMA)-treated cells, but was rather found to synergize with PMA to induce both biomarkers' expression. A contribution of the membrane type-1 (MT1)-MMP was also revealed, since lupeol/PMA treatments triggered proMMP-2 activation, and that MT1-MMP gene silencing reversed the combined effects of lupeol/PMA on both MMP-9 and COX-2. The mRNA stabilizing factor HuR was also found increased in the combined lupeol/PMA treatment, suggesting stabilization processes of the MMP-9 and COX-2 transcripts. We postulate that lupeol's anti-inflammatory properties may exert better pharmacological action within low MT1-MMP expressing tumors. Furthermore, these evidences add up to the new pleiotropic molecular mechanisms of action of MT1-MMP, and prompt for evaluating the future in vitro pharmacological properties of lupeol under pro-inflammatory experimental set-up.

Concanavalin-A-induced autophagy biomarkers requires membrane type-1 matrix metalloproteinase intracellular signaling in glioblastoma cells

Pre-clinical trials for cancer therapeutics support the anti-neoplastic properties of the lectin from Canavalia ensiformis (Concanavalin-A, ConA) in targeting apoptosis and autophagy in a variety of cancer cells. Given that membrane type-1 matrix metalloproteinase (MT1-MMP), a plasma membrane-anchored matrix metalloproteinase, is a glycoprotein strongly expressed in radioresistant and chemoresistant glioblastoma that mediates pro-apoptotic signalling in brain cancer cells, we investigated whether MT1-MMP could also signal autophagy. Among the four lectins tested, we found that the mannopyranoside/glucopyranoside-binding ConA, which is also well documented to trigger MT1-MMP expression, increases autophagic acidic vacuoles formation as demonstrated by Acridine Orange cell staining. Although siRNA-mediated MT1-MMP gene silencing effectively reversed ConA-induced autophagy, inhibition of the MT1-MMP extracellular catalytic function with Actinonin or Ilomastat did not. Conversely, direct overexpression of the recombinant Wt-MT1-MMP protein triggered proMMP-2 activation and green fluorescent protein-microtubule-associated protein light chain 3 puncta indicative of autophagosomes formation, while deletion of MT1-MMP's cytoplasmic domain disabled such autophagy induction. ConA-treated U87 cells also showed an upregulation of BNIP3 and of autophagy-related gene members autophagy-related protein 3, autophagy-related protein 12 and autophagy-related protein 16-like 1, where respective inductions were reversed when MT1-MMP gene expression was silenced. Altogether, we provide molecular evidence supporting the pro-autophagic mechanism of action of ConA in glioblastoma cells. We also highlight new signal transduction functions of MT1-MMP within apoptotic and autophagic pathways that often characterize cancer cell responses to chemotherapeutic drugs.

ERK1/2 regulate exocytosis through direct phosphorylation of the exocyst component Exo70

The exocyst is a multiprotein complex essential for exocytosis and plasma membrane remodeling. The assembly of the exocyst complex mediates the tethering of post-Golgi secretory vesicles to the plasma membrane prior to fusion. Elucidating the mechanisms regulating exocyst assembly is important for the understanding of exocytosis. Here we show that the exocyst component Exo70 is a direct substrate of the extracellular signal-regulated kinases 1/2 (ERK1/2). ERK1/2 phosphorylation enhances the binding of Exo70 to other exocyst components and promotes the assembly of the exocyst complex in response to epidermal growth factor (EGF) signaling. We further demonstrate that ERK1/2 regulates exocytosis, because blocking ERK1/2 signaling by a chemical inhibitor or the expression of an Exo70 mutant defective in ERK1/2 phosphorylation inhibited exocytosis. In tumor cells, blocking Exo70 phosphorylation inhibits matrix metalloproteinase secretion and invadopodia formation. ERK1/2 phosphorylation of Exo70 may thus coordinate exocytosis with other cellular events in response to growth factor signaling.

Phosphorylation of membrane type 1-matrix metalloproteinase (MT1-MMP) and its vesicle-associated membrane protein 7 (VAMP7)-dependent trafficking facilitate cell invasion and migration

In multicellular organisms, uncontrolled movement of cells can contribute to pathological conditions, such as multiple sclerosis and cancer. In highly aggressive tumors, the expression of matrix metalloproteinases (MMPs) is linked to the capacity of tumor cells to invade surrounding tissue and current research indicates that the membrane-anchored membrane type 1-matrix metalloproteinase (MT1-MMP) has a central role in this process. Endocytosis and trafficking of MT1-MMP are essential for its proper function, and here we examine the phosphorylation, internalization, and recycling of this enzyme, and the associated biochemical signaling in HeLa and HT-1080 fibrosarcoma cells. Activation of protein kinase C with phorbol 12-myristate 13-acetate resulted in phosphorylation of endogenous MT1-MMP at Thr(567) in vivo. Mutation of Thr(567) to alanine (to mimic non-phosphorylated MT1-MMP) reduced internalization of MT1-MMP, whereas mutation of Thr(567) to glutamic acid (to mimic phosphorylation) resulted in decreased levels of MT1-MMP on the cell surface. The endosomal trafficking and recycling of MT1-MMP was found to be dependent upon Rab7 and VAMP7, and blocking the function of these proteins reduced cell migration and invasion. Intracellular trafficking of MT1-MMP was observed to be coupled to the trafficking of integrin α5 and phosphorylation of ERK that coincided with this was dependent on phosphorylation of MT1-MMP. Together, these results reveal important roles for MT1-MMP phosphorylation and trafficking in both cell signaling and cell invasion.

Membrane-type 1 matrix metalloproteinase regulates fibronectin assembly to promote cell motility

Fibronectin (FN) matrix assembly is an essential process in normal vertebrate development, which is frequently lost in tumor cells. Here we show that membrane-type 1 matrix metalloproteinase (MT1-MMP) regulates FN matrix assembly. MT1-MMP knockdown induced FN assembly in breast carcinoma cells. Ectopic expression of MT1-MMP reduced specifically the assembled FN matrix level without affecting whole FN production in fibroblasts. Treatment of fibrosarcoma HT1080 cells with dexamethasone (DEX) enhanced FN synthesis, resulting in short fibrils but not dense matrix formation. Combined treatment of DEX and MT1-MMP inhibitor accelerated FN matrix assembly, which mediated cellular adhesion and reduced cell migration and invasion. These results indicate that MT1-MMP stimulates cell migration and invasion by negatively regulating FN assembly.

Glycodelin-A protein interacts with Siglec-6 protein to suppress trophoblast invasiveness by down-regulating extracellular signal-regulated kinase (ERK)/c-Jun signaling pathway

During placentation, the cytotrophoblast differentiates into the villous cytotrophoblast and the extravillous cytotrophoblast. The latter invades the decidualized endometrium. Glycodelin-A (GdA) is abundantly synthesized by the decidua but not the trophoblast. Previous data indicate that GdA suppresses the invasion of trophoblast cell lines by down-regulating proteinase expression and activities. This study addresses the signaling pathway involved in the above phenomenon. GdA was found to suppress phosphorylation of ERKs and expression of their downstream effector c-Jun, a component of the transcription factor activator protein-1 (AP-1). The involvement of ERKs and c-Jun in suppressing trophoblast invasion and biosynthesis of proteinases was confirmed by using siRNA knockdown and pharmacological inhibitors. Desialylation reduced binding affinity of GdA toward and invasion suppressive activities on the trophoblast. Co-immunoprecipitation showed that Siglec-6 on the trophoblast was the binding protein of GdA. The binding of GdA to Siglec-6 was sialic acid-dependent. Treatment with anti-Siglec-6 antibody abolished the invasion suppressive activities of GdA. These results show that GdA interacts with Siglec-6 to suppress trophoblast invasiveness by down-regulating the ERK/c-Jun signaling pathway.

Transforming growth factor Beta regulates proliferation and invasion of rat placental cell lines

Implantation of an embryo in the endometrium is a critical step for continuation of pregnancy, and implantation failure is a major cause of infertility. In rats, the implantation process involves invasion of the endometrial epithelial lining by the trophoblastic cells in order to reach the underlying stromal cells. Transforming growth factor beta (TGFB) is a multifunctional cytokine that regulates proliferation, differentiation, and invasiveness of multiple cell lineages. We used rat HRP-1 and RCHO-1 placental cell lines to perform this study. HRP-1 cells were derived from midgestation chorioallantoic placental explants of the outbred Holtzman rat, whereas RCHO-1 cells were established from a rat choriocarcinoma. MTT proliferation assays revealed that each TGFB isoform decreased HRP-1 cell growth in a dose-dependent manner, whereas RCHO-1 cells were resistant to the growth-suppressive effect of TGFB1 and TGFB3. Only TGFB2 reduced RCHO-1 cell proliferation. Activation of ERK, MAPK14 (p38 MAPK), or SMAD pathways is known to play a role in cell proliferation, and we found that TGFB activates these pathways in both HRP-1 and RCHO-1 cells in an isoform-specific manner. MTT proliferation assays revealed that ERK pathway is partially implicated in TGFB3-reduced HRP-1 cell proliferation. Hoechst nuclear staining and caspase-3 cleavage demonstrated that TGFB isoforms failed to induce apoptosis in both cell lines. Matrigel invasion assays showed that both HRP-1 and RCHO-1 cells exhibit intrinsic invasive ability under untreated conditions. The capacity of HRP-1 cells to invade the Matrigel was selectively increased by TGFB2 and TGFB3, whereas all TGFB isoforms could increase the invasiveness of RCHO-1 cells. These important functional studies progressively reveal a key role for TGFB in regulating proliferation and invasiveness of placental cells.

MEK inhibition potentiates the activity of Hsp90 inhibitor 17-AAG against pancreatic cancer cells

The Ras/Raf/MEK/ERK signaling has been implicated in uncontrolled cell proliferation and tumor progression in pancreatic cancer. The purpose of this study is to evaluate the antitumor activity of MEK inhibitor U0126 in combination with Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) in pancreatic cancer cells. Western blotting showed that 17-AAG caused a 2- to 3-fold transient activation of MEK/ERK signaling in pancreatic cancer cells. The activation sustained for 6 h before phospho-ERK (p-ERK) destabilization. The selective MEK inhibitor U0126 completely abolished 17-AAG induced ERK1/2 activation and resulted in more than 80% of phospho-ERK degradation after only 15 min treatment. Moreover, U0126 had complementary effect on 17-AAG regulated oncogenic and cell cycle related proteins. Although 17-AAG downregulated cyclin D1, cyclin E, CDK4 and CDK6, it led to cyclin A and CDK2 accumulation, which was reversed by the addition of U0126. Antiproliferation assay showed that combination of U0126 and 17-AAG resulted in synergistic cytotoxic effect. More importantly, 17-AAG alone only exhibited moderate inhibition of cell migration in vitro, while addition of U0126 dramatically enhanced the inhibitory effect by 2- to 5-fold. Taken together, these data demonstrate that MEK inhibitor U0126 potentiates the activity of Hsp90 inhibitor 17-AAG against pancreatic cancer cells. The combination of Hsp90 and MEK inhibition could provide a promising avenue for the treatment of pancreatic cancer.

Stromal fibroblasts from the interface zone of human breast carcinomas induce an epithelial-mesenchymal transition-like state in breast cancer cells in vitro

Fibroblasts were extracted from tissue in tumor burden zones, distal normal zones and interface zones between tumor and normal tissue of human breast carcinomas, and the corresponding fibroblasts were designated as cancer-associated fibroblasts (CAFs), normal zone fibroblasts (NFs) and interface zone fibroblasts (INFs). The crosstalk between three types of fibroblasts and breast cancer cells was evaluated using an in vitro direct co-culture model. We found that INFs grew faster and expressed higher levels of fibroblast activation protein than did NFs and CAFs. Compared with CAFs and NFs, INFs grown with breast cancer cells were significantly more effective in inducing an epithelial-mesenchymal transition (EMT) in cancer cells, as indicated by induction of vimentin and N-cadherin and downregulation of E-cadherin. This EMT process was also accompanied by activation of extracellular signal-regulated kinase (ERK) and modulation of membrane-type 1 matrix metalloproteinase (MT1-MMP) expression. Additionally, INFs promoted breast cell migration to a larger extent compared with NFs and CAFs. Taken together, these findings indicate that INFs isolated from the tumor interface zone exhibited more robust biological modulatory activity than did NFs and CAFs isolated from normal and tumor zones of the same tumor tissue, suggesting that the interface zone of the tumor represents a dynamic region vital to tumor progression.

Improved bioengineered cartilage tissue formation following cyclic compression is dependent on upregulation of MT1-MMP

The generation of bioengineered cartilage tissue suitable for transplantation is a potential therapy to treat damaged cartilage. We have shown previously that the physical and biomechanical properties of bioengineered cartilage can be improved by the application of 30 min of cyclic compression by a mechanism involving sequential upregulation of gene and protein levels of membrane type-1 matrix metalloproteinase (MT1-MMP) and MMP-13. In the current study, we demonstrated that MT1-MMP is critical to this response, as blocking the upregulation of MT1-MMP prevented the improvement in tissue formation. MT1-MMP seems to act by inducing tissue remodeling as evidenced by the presence of aggrecan degradation products by Western blot analysis and increased release of matrix molecules into the media. Release of these molecules was diminished when MT1-MMP upregulation was prevented. This matrix degradation was likely due to MT1-MMP, as under conditions where MMP-13 expression is maintained (stimulation in the presence of MT1-MMP siRNA) the release of these matrix molecules into the media was still prevented. It also appears that MT1-MMP does not regulate MMP-13 gene expression, as MT1-MMP-siRNA pretreatment had no effect on MMP-13 expression following mechanical stimulation. Further analysis of the anabolic genes and proteins involved in mechanically stimulated cartilage will lead to better understanding of the mechanism(s) underlying tissue formation yielding improved bioengineered cartilage.

MT1-MMP and integrins: Hand-to-hand in cell communication

Integrins are transmembrane adhesion receptors essential for cell communication with the environment and in particular with the extracellular matrix (ECM). ECM components can be processed by several enzymes; one of the largest families involved in this task being matrix metalloproteinases (MMPs). MT1-MMP (membrane type 1-matrix metalloproteinase) is a membrane-anchored MMP with important roles in processes such as tissue development, tumor invasion, and angiogenesis. In addition to its catalytic-dependent functions, MT1-MMP can interact, via its cytosolic tail, with intracellular components, and trigger signaling pathways that impact cell decisions. These features make MT1-MMP similar to integrins, because both are able to integrate events in the extracellular and intracellular milieus. Accordingly, it is probably no coincidence that MT1-MMP often associates and functionally cooperates with distinct integrins at specific cellular compartments. In this review, we discuss aspects of the molecular and functional interplay between MT1-MMP and integrins in distinct cellular and biological contexts.

MEK inhibition suppresses cell invasion and migration in ovarian cancers with activation of ERK1/2

The extracellular-regulated kinase (ERK) signaling pathway plays an important role in regulating the malignant potential of a cancer cell. However, the effect of ERK signaling on cancer metastasis is not clearly understood. In the present study, we examined the status of ERK activation in 88 ovarian carcinomas in order to clarify the clinicopathological and prognostic significance of phosphorylated ERK1/2 (p-ERK1/2). p-ERK1/2 expression was identified in 37 (42%) of 88 ovarian carcinomas. There was no significant correlation between p-ERK1/2 expression and any of the clinicopathological factors tested. No significant correlation between p-ERK1/2 expression and overall survival was found in patients with ovarian carcinoma treated with platinum and taxane chemotherapy (P=0.426). Next, to clarify the role of ERK1/2 activation in ovarian cancers, we inactivated ERK1/2 in ovarian cancer cells using the MEK inhibitor, CI-1040, which prevents ERK1/2 activation. Based on simulated wound healing and invasion chamber assays, we found that the motility and invasion of ES2 and MPSC1 cells with p-ERK1/2 were significantly reduced (P<0.01) after treatment with CI-1040. By contrast, CI-1040 did not have any effect on KF28 cells, which were negative for p-ERK1/2. Twist was down-regulated simultaneously with p-ERK1/2 following treatment of ES2 and MPSC1 cells with CI-1040. Immunohistochemistry of ovarian carcinoma tissue revealed that the increased expression of p-ERK1/2 significantly correlated with Twist expression (P<0.01). The findings in this study provide new insight into the biological role of ERK signaling in ovarian carcinomas. Additionally, our observations have an important therapeutic implication for patients with ovarian cancers that express p-ERK1/2 as these patients may potentially benefit from CI-1040 therapy.

MT1-MMP promotes cell growth and ERK activation through c-Src and paxillin in three-dimensional collagen matrix

Membrane-type 1 matrix metalloproteinase (MT1-MMP) is essential for tumor invasion and growth. We show here that MT1-MMP induces extracellular signal-regulated kinase (ERK) activation in cancer cells cultured in collagen gel, which is indispensable for their proliferation. Inhibition of MT1-MMP by MMP inhibitor or small interfering RNA suppressed activation of focal adhesion kinase (FAK) and ERK in MT1-MMP-expressing cancer cells, which resulted in up-regulation of p21(WAF1) and suppression of cell growth in collagen gel. Cell proliferation was also abrogated by the inhibitor against ERK pathway without affecting FAK phosphorylation. MT1-MMP and integrin alpha(v)beta(3) were shown to be involved in c-Src activation, which induced FAK and ERK activation in collagen gel. These MT1-MMP-mediated signal transductions were paxillin dependent, as knockdown of paxillin reduced cell growth and ERK activation, and co-expression of MT1-MMP with paxillin induced ERK activation. The results suggest that MT1-MMP contributes to proliferation of cancer cells in the extracellular matrix by activating ERK through c-Src and paxillin.

Decursinol angelate blocks transmigration and inflammatory activation of cancer cells through inhibition of PI3K, ERK and NF-kappaB activation

Inflammation is known to be closely associated with the development of cancer. Decursinol angelate (DA), a coumarin compound isolated from Angelica gigas and related compounds have been shown to possess potent anti-inflammatory activities. However, little is known about their effects on the inflammatory processes associated with cancer. In this study, the anti-inflammatory effect of DA was evaluated in cancer cell lines with respect to cellular invasion through the extracellular matrix (ECM) and the expression of pro-inflammatory mediators such as cytokine, cell adhesion molecules and matrix metalloproteinase (MMP)-9. DA inhibited the invasion of fibrosarcoma cell line, HT1080 and breast cancer cell line, MDA-MB-231 in the Matrigel invasion assay. DA-mediated suppression of cancer cell invasion was accomplished by suppression of PI3K activity known to be associated with cytoskeletal rearrangement related to cellular migration. DA also suppressed the adhesion of cancer cells to ECM mediated by down-regulation of beta(1)-integrin expression levels. Furthermore, DA inhibited the expression of pro-inflammatory cytokines and MMP-9 through suppression of PI3K, ERK and NF-kappaB activation. These results demonstrate that DA suppresses invasion and inflammatory activation of cancer cells through modulation of PI3K/AKT, ERK and NF-kappaB. These anti-inflammatory activities of DA may contribute to its anti-cancer activity.

Coordinate action of membrane-type matrix metalloproteinase-1 (MT1-MMP) and MMP-2 enhances pericellular proteolysis and invasion

Membrane-type matrix metalloproteinase-1 (MT1-MMP) mediates cleavage of not only MMP-2/gelatinase A for activation, but also a variety of substrates including type I collagen (reviewed in Cancer Sci 2005; 96: 212-7). MMP-2 activation involves tissue inhibitor of MMP (TIMP)-2 as a bridging molecule between MT1-MMP and pro-MMP-2. Thus, net activity of MT1-MMP and MMP-2 is regulated in a complex manner depending on TIMP-2 concentration. During invasive growth of tumor cells in type I collagen matrix, MT1-MMP initiates denaturation of collagen into gelatin, which is subsequently digested further by MMP-2 adjacent to MT1-MMP. Coordinate action of MT1-MMP and MMP-2 may facilitate pericellular proteolysis, and enhance not only tumor invasion/migration but also cell growth. Tetraspanins as binding proteins of MT1-MMP regulate MT1-MMP subcellular localization and compartmentalization, leading to efficient MMP-2 activation and proteolysis coupled with cellular function.

Troglitazone inhibits vascular endothelial growth factor-induced angiogenic signaling via suppression of reactive oxygen species production and extracellular signal-regulated kinase phosphorylation in endothelial cells

Thiazolidinediones, peroxisome proliferators-activated receptor gamma (PPARgamma) ligands, have been recognized as a potential therapeutic agents for the treatment of pathological neovascularization. In the present study, we examined the molecular mechanism by which troglitazone (TROG), a PPARgamma agonist, exerts its inhibitory action in vascular endothelial growth factor (VEGF)-induced angiogenesis signaling. In an in vitro angiogenesis model using human umbilical vein endothelial cells, TROG (20 muM) significantly suppressed VEGF-induced cell proliferation and invasion of the cells into the Matrigel basement membrane, which was not reversed by treatment with PPAR antagonists, GW9662 (10 muM) and bisphenol A diglycidyl ether (10 muM). TROG also blocked VEGF-induced reactive oxygen species (ROS) production and its downstream extracellular signal-regulated kinase (ERK) phosphorylation, and this inhibitory effect was not reversed by GW9662 (10 muM). The antiangiogenic activity of TROG correlated with suppression of VEGF-induced matrix metalloproteinase (MMP)-2 and membrane type 1 (MT1)-MMP expression. In addition, the effects of TROG on VEGF-induced MMP-2 and MT1-MMP expression were comparable to those of the NADPH oxidase inhibitor diphenylene iodium (10 muM) and ERK inhibitor PD98056 (10 muM). Furthermore, in an in vivo angiogenesis system using a chick chorioallantoic membrane model, TROG dose-dependently inhibited VEGF-induced angiogenesis, which was similar to the inhibitory effect of N-acetylcysteine on VEGF-induced angiogenesis. The results suggest that the inhibitory effects of TROG on VEGF-induced angiogenesis were mediated through the suppression of VEGF-induced ROS production and ERK phosphorylation.

Collagen I regulates matrix metalloproteinase-2 activation in osteosarcoma cells independent of S100A4

This work investigates the effect of cell-collagen I interactions on the synthesis and activation of MMP-2, as well as synthesis of MT1-MMP and TIMP-1, by using an in vitro model with 3D fibrillar and 2D monomeric collagen. In order to reveal whether the metastasis-associated protein S100A4 can influence the cell's response to the two forms of collagen, osteosarcoma cell lines with high and low endogenous levels of S100A4 were used. Attachment of osteosarcoma cells to 3D fibrillar and 2D monomeric collagen resulted in opposite effects on MMP-2 activation. Attachment to 3D fibrillar collagen decreased activation of proMMP-2, with a corresponding reduction in MT1-MMP. By contrast, attachment to monomeric collagen increased the amount of fully active MMP-2. This was caused by a reduction in TIMP-1 levels when cells were attached to monomeric 2D collagen. The effect of collagen on proMMP-2 activation was independent of endogenous S100A4 levels, whereas synthesis of TIMP-1 was dependent on S100A4. When cells were attached to monomeric collagen, cells with a high level of S100A4 showed a greater reduction in the synthesis of TIMP-1 than did those with a low level of S100A4. Taken together, this study shows that synthesis and activation of MMP-2 is affected by interactions between osteosarcoma cells and collagen I in both fibrillar and monomeric form.

Targeting migration inducting gene-7 inhibits carcinoma cell invasion, early primary tumor growth, and stimulates monocyte oncolytic activity

Expression of Migration inducting gene-7 (Mig-7) is limited to tumor cells and to date not found in normal tissues. Multiple tumor microenvironment factors, such as epidermal and hepatocyte growth factors, in concert with alphavbeta5 integrin ligation, induce Mig-7 mRNA expression. Gain or loss of Mig-7 protein studies shows that Mig-7 promotes invasion of colon and endometrial carcinoma cells. These data led us to hypothesize that targeting Mig-7 through various methods could decrease invasion, enhance monocyte cell killing of tumor cells, and inhibit disease progression. To begin testing this hypothesis, an in vitro chemoinvasion assay of endometrial carcinoma cells treated with Mig-7-specific or control antibodies was used. Mig-7 antibody significantly reduced invasion by >60% compared with controls. In another approach to test this hypothesis, an in vitro analysis of peptide-stimulated human peripheral blood monocyte cells and their killing of MCF-7 breast carcinoma cells was used. Mig-7 peptide treatment increased monocyte cell tumor necrosis factor expression and killing of MCF-7 cells 30-fold over no peptide stimulation and 3-fold over MUC-1 or control peptide treatments. Furthermore, stably expressing Mig-7-specific short hairpin RNA resulted in significantly reduced Mig-7 protein levels and early primary tumor growth in a xenograft nude mouse model. Reduced phosphorylation of ERK1/2, Akt, and S6 kinase as well as decreased membrane-type 1 matrix metalloproteinase activity were mechanisms through which Mig-7 protein caused these effects. Based on these collective data, Mig-7 expression could be a potential candidate for future targeted cancer therapies.

Emerging concepts in the regulation of membrane-type 1 matrix metalloproteinase activity

Pericellular proteolysis mediated by membrane-type 1 matrix metalloproteinase (MT1-MMP) represents an essential component of the cellular machinery involved in the dissolution and penetration of ECM barriers by tumor cells. Although most studies on the proinvasive properties of MT1-MMP have focused on its unusually broad proteolytic activity towards several ECM components and cell surface receptors, recent evidence indicate that the cytoplasmic domain of the enzyme also actively participates in tumor cell invasion by regulating the cell surface localization of MT1-MMP as well as the activation of signal transduction cascades. The identification of the molecular events by which the intracellular domain of MT1-MMP links proteolysis of the surrounding matrix by the enzyme to modification of cell function may thus provide important new information on the mechanisms by which this enzyme controls the invasive behavior of neoplastic cells in vivo.

Membrane type-1 matrix metalloproteinase potentiates basic fibroblast growth factor-induced corneal neovascularization

Corneal neovascularization is one of the leading causes of blindness. The aim of this study was to evaluate the pro-angiogenic role of corneal fibroblast-derived membrane type-1 matrix metalloproteinase (MT1-MMP) on basic fibroblast growth factor (bFGF)-induced corneal neovascularization in vivo and in vitro. Immunohistochemical studies demonstrated that MT1-MMP was expressed in keratocytes and immortalized corneal fibroblast cell lines. Vascular endothelial growth factor protein levels were increased after bFGF-stimulation of wild-type fibroblast cells compared with MT1-MMP knockout fibroblast cells. Corneal vascularization was significantly increased after a combination of bFGF pellet implantation and naked MT1-MMP DNA injection in wild-type mouse corneas compared with either bFGF pellet implantation or naked MT1-MMP DNA-injected corneas. Western blotting analysis of the phosphorylation levels of the key signaling molecules (p38, JNK, and ERK) demonstrated that phosphorylation levels of both p38 and JNK were diminished after bFGF stimulation of MT1-MMP knockout cells compared with wild-type and MT1-MMP knockin cells. These results suggest that MT1-MMP potentiates bFGF-induced corneal neovascularization, likely by modulating the bFGF signal transduction pathway.

Activation of matrix metalloproteinase-2 (MMP-2) by membrane type 1 matrix metalloproteinase through an artificial receptor for proMMP-2 generates active MMP-2

The suggested model for pro-matrix metalloproteinase-2 (proMMP-2) activation by membrane type 1 MMP (MT1-MMP) implicates the complex between MT1-MMP and tissue inhibitor of MMP-2 (TIMP-2) as a receptor for proMMP-2. To dissect this model and assess the pathologic significance of MMP-2 activation, an artificial receptor for proMMP-2 was created by replacing the signal sequence of TIMP-2 with cytoplasmic/transmembrane domain of type II transmembrane mosaic serine protease (MSP-T2). Unlike TIMP-2, MSP-T2 served as a receptor for proMMP-2 without inhibiting MT1-MMP, and generated TIMP-2-free active MMP-2 even at a low level of MT1-MMP. Thus, MSP-T2 did not affect direct cleavage of the substrate testican-1 by MT1-MMP, whereas TIMP-2 inhibited it even at the level that stimulates proMMP-2 processing. Expression of MSP-T2 in HT1080 cells enhanced MMP-2 activation by endogenous MT1-MMP and caused intensive hydrolysis of collagen gel. Expression of MSP-T2 in U87 glioma cells, which express a trace level of endogenous MT1-MMP, induced MMP-2 activation and enhanced cell-associated protease activity, activation of extracellular signal-regulated kinase, and metastatic ability into chick embryonic liver and lung. MT1-MMP can exert both maximum MMP-2 activation and direct cleavage of substrates with MSP-T2, which cannot be achieved with TIMP-2. These results suggest that MMP-2 activation by MT1-MMP potentially amplifies protease activity, and combination with direct cleavage of substrate causes effective tissue degradation and enhances tumor invasion and metastasis, which highlights the complex role of TIMP-2. MSP-T2 is a unique tool to analyze physiologic and pathologic roles of MMP-2 and MT1-MMP in comparison with TIMP-2.

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.

Molecular signature of MT1-MMP: transactivation of the downstream universal gene network in cancer

Invasion-promoting MT1-MMP is directly linked to tumorigenesis and metastasis. Our studies led us to identify those genes, the expression of which is universally linked to MT1-MMP in multiple tumor types. Genome-wide expression profiling of MT1-MMP-overexpressing versus MT1-MMP-silenced cancer cells and a further data mining analysis of the preexisting expression database of 190 human tumors of 14 cancer types led us to identify 11 genes, the expression of which correlated firmly and universally with that of MT1-MMP (P < 0.00001). These genes included regulators of energy metabolism (NNT), trafficking and membrane fusion (SLCO2A1 and ANXA7), signaling and transcription (NR3C1, JAG1, PI3K delta, and CK2 alpha), chromatin rearrangement (SMARCA1), cell division (STK38/NDR1), apoptosis (DAPK1), and mRNA splicing (SNRPB2). Our subsequent extensive analysis of cultured cells, tumor xenografts, and cancer patient biopsies supported our data mining. Our results suggest that transcriptional reprogramming of the specific downstream genes, which themselves are associated with tumorigenesis, represents a distinctive "molecular signature" of the proteolytically active MT1-MMP. We suggest that the transactivation activity of MT1-MMP contributes to the promigratory cell phenotype, which is induced by this tumorigenic proteinase. The activated downstream gene network then begins functioning in unison with MT1-MMP to rework the signaling, transport, cell division, energy metabolism, and other critical cell functions and to commit the cell to migration, invasion, and, consequently, tumorigenesis.