Intact vitronectin induces matrix metalloproteinase-2 and tissue inhibitor of metalloproteinases-2 expression and enhanced cellular invasion by melanoma cells

Hypothalamic Oxytocin Neuron Activation Attenuates Intermittent Hypoxia-Induced Hypertension and Cardiac Dysfunction in an Animal Model of Sleep Apnea

BACKGROUND

Obstructive sleep apnea is a prevalent and poorly treated cardiovascular disease that leads to hypertension and autonomic imbalance. Recent studies that restore cardiac parasympathetic tone using selective activation of hypothalamic oxytocin neurons have shown beneficial cardiovascular outcomes in animal models of cardiovascular disease. This study aimed to determine if chemogenetic activation of hypothalamic oxytocin neurons in animals with existing obstructive sleep apnea-induced hypertension would reverse or blunt the progression of autonomic and cardiovascular dysfunction.

METHODS

Two groups of rats were exposed to chronic intermittent hypoxia (CIH), a model of obstructive sleep apnea, for 4 weeks to induce hypertension. During an additional 4 weeks of exposure to CIH, 1 group was treated with selective activation of hypothalamic oxytocin neurons while the other group was untreated.

RESULTS

Hypertensive animals exposed to CIH and treated with daily hypothalamic oxytocin neuron activation had lower blood pressure, faster heart rate recovery times after exercise, and improved indices of cardiac function compared with untreated hypertensive animals. Microarray analysis suggested that, compared with treated animals, untreated animals had gene expression profiles associated with cellular stress response activation, hypoxia-inducible factor stabilization, and myocardial extracellular matrix remodeling and fibrosis.

CONCLUSIONS

In animals already presenting with CIH-induced hypertension, chronic activation of hypothalamic oxytocin neurons blunted the progression of hypertension and conferred cardioprotection after an additional 4 weeks of CIH exposure. These results have significant clinical translation for the treatment of cardiovascular disease in patients with obstructive sleep apnea.

Vitronectin and Its Interaction with PAI-1 Suggests a Functional Link to Vascular Changes in AMD Pathobiology

The pathogenesis of age-related macular degeneration (AMD), a frequent disorder of the central retina, is incompletely understood. Genome-wide association studies (GWAS) suggest a strong contribution of genomic variation in AMD susceptibility. Nevertheless, little is known about biological mechanisms of the disease. We reported previously that the AMD-associated polymorphism rs704C > T in the vitronectin (VTN) gene influences protein expression and functional aspects of encoded vitronectin, a human blood and extracellular matrix (ECM) protein. Here, we refined the association of rs704 with AMD in 16,144 cases and 17,832 controls and noted that rs704 is carried exclusively by the neovascular AMD subtype. Interaction studies demonstrate that rs704 affects the ability of vitronectin to bind the angiogenic regulator plasminogen activator inhibitor 1 (PAI-1) but has no influence on stabilizing its active state. Western blot analysis and confocal imaging reveal a strong enrichment of PAI-1 in the ECM of cultured endothelial cells and RPE cell line ARPE-19 exposed to vitronectin. Large-scale gene expression of VTN and PAI-1 showed positive correlations and a statistically significant increase in human retinal and blood tissues aged 60 years and older. Our results suggest a mechanism by which the AMD-associated rs704 variant in combination with ageing may contribute to the vascular complications in AMD.

Calibrating models of cancer invasion: parameter estimation using approximate Bayesian computation and gradient matching

We present two different methods to estimate parameters within a partial differential equation model of cancer invasion. The model describes the spatio-temporal evolution of three variables-tumour cell density, extracellular matrix density and matrix degrading enzyme concentration-in a one-dimensional tissue domain. The first method is a likelihood-free approach associated with approximate Bayesian computation; the second is a two-stage gradient matching method based on smoothing the data with a generalized additive model (GAM) and matching gradients from the GAM to those from the model. Both methods performed well on simulated data. To increase realism, additionally we tested the gradient matching scheme with simulated measurement error and found that the ability to estimate some model parameters deteriorated rapidly as measurement error increased.

Low expression of the PPARγ-regulated gene thioredoxin-interacting protein accompanies human melanoma progression and promotes experimental lung metastases

The thioredoxin system plays key roles in regulating cancer cell malignancy. Here we identify the Thioredoxin-interacting protein (TXNIP) as a gene, which expression is regulated by PPARγ in melanoma cells. We show that high TXNIP expression levels associate with benign melanocytic lesions, with tumor regression in patients on MAP kinase targeted therapy, with decreased proliferation in patients’ melanoma biopsies, and with cell cycle arrest in human melanoma cell lines. In contrast, reduced TXNIP expression associates with advanced melanoma and with disease progression in patients. TXNIP depletion in human melanoma cells altered the expression of integrin beta-3 and the localization of the integrin alpha-v/beta-3 dimer at their surface. Moreover, TXNIP depletion affected human melanoma cell motility and improved their capacity to colonize mouse lungs in an in vivo assay. This study establishes TXNIP as a PPARγ-regulated gene in melanoma cells, thereby suggesting a link between these two proteins both involved in the regulation of cancer and of energy metabolism. It also reveals that the decrease in TXNIP expression, which is observed in advanced patient tumors, likely favors lung metastatic seeding of malignant cells.

Vitronectin deficiency attenuates hepatic fibrosis in a non-alcoholic steatohepatitis-induced mouse model

Vitronectin (VN), an extracellular matrix protein, is a promising immune biomarker of non-alcoholic steatohepatitis (NASH); however, its precise function remains unclear. This study investigated how VN deficiency contributes to the development of NASH. Towards this aim, wild-type (WT) and VN-/- mice were fed with a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) for 6 and 10 weeks to induce NASH, and the livers were isolated. In WT mice fed with CDAHFD for 6 and 10 weeks, the expression of Vn mRNA and protein was up-regulated compared with that in mice fed with the MF control diet, indicating that VN is regulated in NASH condition. VN-/- mice showed decreased picrosirius red staining in the liver area and Col1a2 mRNA expression levels, compared with WT mice, indicating that the severity of hepatic fibrosis is attenuated in the CDAHFD-fed VN-/- mice. In addition, VN deficiency did not affect the area of lipid droplets in haematoxylin-eosin staining and the mRNA expression levels of fatty acid synthases, Srebp, Acc and Fas in the CDAHFD-fed mice. Moreover, VN deficiency decreased the inflammation score and the mRNA expression levels of Cd11b and F4/80, macrophage markers, as well as Tnf-α and Il-1β, inflammatory cytokines in the CDAHFD-fed mice. Furthermore, VN deficiency decreased the protein and mRNA expression levels of α-smooth muscle actin in the CDAHFD-fed mice, suggesting that VN deficiency inhibits the activation of hepatic stellate cells (HSCs). Our findings indicate that VN contributes to the development of fibrosis in the NASH model mice via modulation of the inflammatory reaction and activation of HSCs.

Structured models of cell migration incorporating molecular binding processes

The dynamic interplay between collective cell movement and the various molecules involved in the accompanying cell signalling mechanisms plays a crucial role in many biological processes including normal tissue development and pathological scenarios such as wound healing and cancer. Information about the various structures embedded within these processes allows a detailed exploration of the binding of molecular species to cell-surface receptors within the evolving cell population. In this paper we establish a general spatio-temporal-structural framework that enables the description of molecular binding to cell membranes coupled with the cell population dynamics. We first provide a general theoretical description for this approach and then illustrate it with three examples arising from cancer invasion.

Clinical significance of serum fibronectin and vitronectin levels in melanoma patients

Fibronectin and vitronectin are the important components of the extracellular matrix proteins. The aim of this study was to determine the clinical significance of these protein serum levels in patients with melanoma. A total of 60 patients with a pathologically confirmed diagnosis of melanoma were enrolled in this study. Serum fibronectin and vitronectin concentrations were determined using the solid-phase sandwich ELISA method. Thirty age-matched and sex-matched healthy controls were included in the analysis. The baseline serum fibronectin and vitronectin levels were significantly higher in patients with melanoma than those in the healthy control group (P<0.001 and P=0.04, respectively). However, known clinical variables including age of the patient, sex, site of lesion, histology, stage of disease, serum lactate dehydrogenase levels, and response to chemotherapy were not found to be correlated with either serum fibronectin or vitronectin concentrations (P>0.05). Moreover, neither serum fibronectin nor vitronectin levels played a prognostic role in outcome in melanoma patients (P=0.47 and 0.24, respectively). In conclusion, serum levels of both fibronectin and vitronectin may be diagnostic markers in melanoma patients. However, their predictive and prognostic values were not determined.

Effects of Blocking αvβ₃ integrin by a recombinant RGD disintegrin on remodeling of wound healing after induction of incisional hernia in rats

PURPOSE

Incisional hernia (IH) is characterized by defective wound healing process. Disba-01, a αvb₃ integrin blocker has shown to control the rate of wound repair and therefore it could be a target for new wound healing therapies.The objective of the study was to determine the changes induced by Disba-01 on repair of wound healing after induced IH in rats.

METHODS

Thirty two male albino rats were submitted to IH and divided into 4 experimental groups: G1, placebo control; G2, DisBa-01-treated; G3, anti-αvβ₃ antibodies-treated and G4, anti-α₂ antibodies-treated. Histological. biochemical and extracellular matrix remodeling analysis of abdominal wall were evaluated.

RESULTS

After 14 days, 100% of the G2 did not present hernia, and the hernia ring was closed by a thin membrane. In contrast, all groups maintained incisional hernia. DisBa-01 also increased the number macrophages and fibroblasts and induced the formation of new vessels. Additionally, MMP-2 was strongly activated only in G2 (P<0.05). Anti- αvβ₃-integrin antibodies produced similar results than Disba-01 but not anti-α₂ integrin blocking antibodies.

CONCLUSION

These results strongly indicate that Disba-01 has an important role in the control of wound healing and the blocking of this integrin may be an interesting therapeutical strategy in IH.

T11TS inhibits glioma angiogenesis by modulation of MMPs, TIMPs, with related integrin αv and TGF-β1 expressions

During glioma development, angiogenesis plays a crucial role in growth and vascularization of primary brain tumors. T11 target structure (T11TS), a bioactive molecule, has been documented as an anti-neoplastic agent in glioma-induced rats and also in human glioma in vitro. This novel molecule induces apoptosis of tumor cells by way of immune potentiation and impairs the glioma cell cycle, but its role in glioma angiogenesis has not been worked out in detail. Matrix metalloproteinases (MMPs) are enzymes promoting tumor angiogenesis by enzymatically remodeling the extracellular matrix and altering surface protein expression such as integrin αv and the matrix-bound proteins like TGF-β1. The present study was formulated to assess the efficacy of T11TS in the modulations of MMP-2 and -9 and their endogenous inhibitors (TIMP-1 and TIMP-2) as well as modulations of integrin αv and TGF-β1 in glioma-induced rats and also on the phenotypic markers of endothelial cells (CD31 and CD34). The parameters used were zymography, western blot, and flow cytometric analyses. It was observed that T11TS administration significantly downregulates the expression of matrix metalloproteinase-2 and -9 along with its ligand integrin αv and upregulates TIMP-1 and TIMP-2. In situ immunofluorescence and FACS results revealed that T11TS administration decreased the expression of the phenotypic markers (CD31/PECAM1, CD34), inhibiting the cell grip and also downregulating TGF-β1 expression (ELISA) from microglia cells in the glioma microenvironment. These results suggest that T11TS suppresses the expression of positive angiogenic growth factors and potentiates the expression of negative regulators in glioma-associated endothelial cells (ECs), resulting in an anti-angiogenic effect on glioma-induced angiogenesis.

Vitronectin--master controller or micromanager?

The concept that the mammalian glycoprotein vitronectin acts as a biological 'glue' and key controller of mammalian tissue repair and remodelling activity is emerging from nearly 50 years of experimental in vitro and in vivo data. Unexpectedly, the vitronectin-knockout (VN-KO) mouse was found to be viable and to have largely normal phenotype. However, diligent observation revealed that the VN-KO animal exhibits delayed coagulation and poor wound healing. This is interpreted to indicate that VN occupies a role in the earliest events of thrombogenesis and tissue repair. VN is the foundation upon which the thrombus grows in an organised structure. In addition to sealing the wound, the thrombus also serves to protect the underlying tissue from oxidation, is a reservoir of mitogens and tissue repair mediators, and provides a provisional scaffold for the repairing tissue. In the absence of VN (e.g., VN-KO animal), this cascade is disrupted before it begins. A wide variety of biologically active species associate with VN. Although initial studies were focused on mitogens, other classes of bioactives (e.g., glycosaminoglycans and metalloproteinases) are now also known to specifically interact with VN. Although some interactions are transient, others are long-lived and often result in multi-protein complexes. Multi-protein complexes provide several advantages: prolonging molecular interactions, sustaining local concentrations, facilitating co-stimulation of cell surface receptors and thereby enhancing cellular/biological responses. We contend that these, or equivalent, multi-protein complexes facilitate VN polyfunctionality in vivo. It is also likely that many of the species demonstrated to associate with VN in vitro, also associate with VN in vivo in similar multi-protein complexes. Thus, the predominant biological function of VN is that of a master controller of the extracellular environment; informing, and possibly instructing cells 'where' to behave, 'when' to behave and 'how' to behave (i.e., appropriately for the current circumstance).

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Interaction of late apoptotic and necrotic cells with vitronectin

Background

Vitronectin is an abundant plasma glycoprotein identified also as a part of extracellular matrix. Vitronectin is substantially enriched at sites of injured, fibrosing, inflamed, and tumor tissues where it is believed to be involved in wound healing and tissue remodeling. Little is known about the mechanism of vitronectin localization into the damaged tissues.

Methodology/Principal Findings

2E12 antibody has been described to bind a subset of late apoptotic cells. Using immunoisolation followed by mass spectrometry, we identified the antigen recognized by 2E12 antibody as vitronectin. Based on flow cytometry, we described that vitronectin binds to the late apoptotic and necrotic cells in cell cultures in vitro as well as in murine thymus and spleen in vivo. Confocal microscopy revealed that vitronectin binds to an intracellular cytoplasmic structure after the membrane rupture.

Conclusions/Significance

We propose that vitronectin could serve as a marker of membrane disruption in necrosis and apoptosis for flow cytometry analysis. Moreover, we suggest that vitronectin binding to dead cells may represent one of the mechanisms of vitronectin incorporation into the injured tissues.

MMP-2 alters VEGF expression via alphaVbeta3 integrin-mediated PI3K/AKT signaling in A549 lung cancer cells

Vascular endothelial growth factor (VEGF) is one of the most important angiogenic growth factors for tumor angiogenesis. Here, we sought to explore whether RNA interference (RNAi) targeting matrix metalloproteinase-2 (MMP-2) could disrupt VEGF-mediated angiogenesis in lung cancer. MMP-2 siRNA inhibited lung cancer cell-induced tube formation of endothelial cells in vitro; addition of recombinant human-MMP-2 restored angiogenesis. MMP-2 transcriptional suppression decreased VEGF, phosphatidylinositol 3-kinase (PI3K) protein levels and AKT phosphorylation in lung cancer cells. In addition, MMP-2 suppression decreased hypoxia inducible factor-1alpha (HIF-1alpha), a transcription factor for VEGF, as determined by electrophoretic mobility shift assay (EMSA). We also show that MMP-2 suppression disrupted PI3K dependent VEGF expression; ectopic expression of myr-AKT restored VEGF inhibition. Further, MMP-2 suppression decreased the interaction of integrin-alphaVbeta3 and MMP-2 as confirmed by immunoprecipitation analyses. Studies with either function blocking integrin-alphaVbeta3 antibody or MMP-2 specific inhibitor (ARP-100) indicate that suppression of MMP-2 decreased integrin-alphaVbeta3-mediated induction of PI3K/AKT leading to decreased VEGF expression. Moreover, A549 xenograft tissue sections from mice that treated with MMP-2 siRNA showed reduced expression of VEGF and the angiogenic marker, factor-VIII. The inhibition of tumor angiogenesis in MMP-2 suppressed tumor sections was associated with decreased co-localization of integrin-alphaVbeta3 and MMP-2. In summary, these data provide new insights into the mechanisms underlying MMP-2-mediated VEGF expression in lung tumor angiogenesis.

Inhibition of Necl-5 (CD155/PVR) reduces glioblastoma dispersal and decreases MMP-2 expression and activity

Patients afflicted with glioblastoma (GBM) have poor survival due to dispersive invasion throughout the brain. Necl-5, a cell surface receptor for vitronectin, is expressed in GBM but not normal brain. In several GBM cell lines Necl-5 promotes migration and invasion but the mechanism is poorly understood. In this study, we show that knockdown of Necl-5 by RNAi results in markedly decreased invasion of A172 GBM cells in a 3-dimensional matrix. There is a concomitant decrease in the expression and activity of matrix metalloproteinase-2 (MMP-2), a known factor in GBM invasion and disease severity. Knockdown of Necl-5 diminishes basal activation of Akt, an established mediator of MMP-2 expression in gliomas. Knockdown of Necl-5 also limits the maximal Akt activation in response to vitronectin, which requires the activity of Integrin-linked kinase (ILK). During migration, Necl-5, Akt and ILK co-localize at focal contacts at the leading edge of the plasma membrane, suggesting that these molecules may act to integrate Akt signaling at the leading edge to induce MMP-2 expression. By virtue of its restricted expression in GBM and its role in invasion, Necl-5 may be an attractive target for limiting MMP-2 production in glioblastoma, and therefore limiting dispersal.

pH dependence of the enzymatic processing of collagen I by MMP-1 (fibroblast collagenase), MMP-2 (gelatinase A), and MMP-14 ectodomain

The proteolytic processing of collagen I by three matrix metalloproteinases (MMPs), a collagenase (MMP-1), a gelatinase (MMP-2), and the ectodomain of a membrane-type metalloproteinase (MMP-14), has been investigated at 37 °C between pH 6.0 and 9.2, a pH range reflecting conditions found in different body compartments under various physiopathological processes. In the proteolytic degradation the native collagen triple helix must be partially unwound to allow the binding of α chains to the protease's active-site cleft. We have found that MMP-1 interacts with the two types of collagen I α chains in a similar fashion, whereas both MMP-2 and MMP-14 bind the two α chains in a different way. The overall enzymatic activity is higher on the α-2 chain for both MMP-1 and MMP-2, whereas the MMP-14 ectodomain preferentially cleaves the α-1 chain. In MMP-2 a marked difference for substrate affinity (higher for the α-1 chain) is overwhelmed by an even more marked propensity to cleave the α-2 chain. As a whole, the three classes of MMPs investigated appear to process collagen I in a significantly different fashion, so various MMPs play different roles in the collagen homeostasis in various compartments (such as bloodstream, synovial fluid, normal and tumoral tissues), where different pH values are observed.

Cell migration-the role of integrin glycosylation

BACKGROUND

Cell migration is an essential process in organ homeostasis, in inflammation, and also in metastasis, the main cause of death from cancer. The extracellular matrix (ECM) serves as the molecular scaffold for cell adhesion and migration; in the first phase of migration, adhesion of cells to the ECM is critical. Engagement of integrin receptors with ECM ligands gives rise to the formation of complex multiprotein structures which link the ECM to the cytoplasmic actin skeleton. Both ECM proteins and the adhesion receptors are glycoproteins, and it is well accepted that N-glycans modulate their conformation and activity, thereby affecting cell-ECM interactions. Likely targets for glycosylation are the integrins, whose ability to form functional dimers depends upon the presence of N-linked oligosaccharides. Cell migratory behavior may depend on the level of expression of adhesion proteins, and their N-glycosylation that affect receptor-ligand binding.

SCOPE OF REVIEW

The mechanism underlying the effect of integrin glycosylation on migration is still unknown, but results gained from integrins with artificial or mutated N-glycosylation sites provide evidence that integrin function can be regulated by changes in glycosylation.

GENERAL SIGNIFICANCE

A better understanding of the molecular mechanism of cell migration processes could lead to novel diagnostic and therapeutic approaches and applications. For this, the proteins and oligosaccharides involved in these events need to be characterized.

Cyr61/CCN1 displays high-affinity binding to the somatomedin B(1-44) domain of vitronectin

Background

Cyr61 is a member of the CCN (Cyr61, connective tissue growth, NOV) family of extracellular-associated (matricellular) proteins that present four distinct functional modules, namely insulin-like growth factor binding protein (IGFBP), von Willebrand factor type C (vWF), thrombospondin type 1 (TSP), and C-terminal growth factor cysteine knot (CT) domain. While heparin sulphate proteoglycans reportedly mediate the interaction of Cyr61 with the matrix and cell surface, the role of other extracellular associated proteins has not been revealed.

Methods and Findings

In this report, surface plasmon resonance (SPR) experiments and solid-phase binding assays demonstrate that recombinant Cyr61 interacts with immobilized monomeric or multimeric vitronectin (VTNC) with K_D in the nanomolar range. Notably, the binding site for Cyr61 was identified as the somatomedin B domain (SMTB ^1–44) of VTNC, which mediates its interaction with PAI-1, uPAR, and integrin αvβ3. Accordingly, PAI-1 outcompetes Cyr61 for binding to immobilized SMTB ^1–44, and Cyr61 attenuates uPAR-mediated U937 adhesion to VTNC. In contrast, isothermal titration calorimetry shows that Cyr61 does not display high-affinity binding for SMTB ^1-44 in solution. Nevertheless, competitive ELISA revealed that multimeric VTNC, heat-modified monomeric VTNC, or SMTB ^1–44 at high concentrations attenuate Cyr61 binding to immobilized VTNC, while monomeric VTNC was ineffective. Therefore, immobilization of VTNC exposes cryptic epitopes that recognize Cyr61 with high affinity, as reported for a number of antibodies, β-endorphin, and other molecules.

Conclusions

The finding that Cyr61 interacts with the SMTB ^1–44 domain suggests that VTNC represent a point of anchorage for CCN family members to the matrix. Results are discussed in the context of the role of CCN and VTNC in matrix biology and angiogenesis.

Analysis of MMP-dependent cell migration and invasion

Analysing cell migration and invasion is of interest to many investigators as they mimic a part of physiological or pathological events. In this chapter, methods to analyse MMP-dependent 2D and 3D cell migration are described in detail. To study 2D cell migration, the phagokinetic track motility assay can be used. To study 3D cell migration, Matrigel invasion assay or microcarrier beads invasion assay can be used to obtain quantitative results.

Fibronectin-integrin mediated signaling in human cervical cancer cells (SiHa)

Interaction between cell surface integrin receptors and extracellular matrix (ECM) components plays an important role in cell survival, proliferation, and migration, including tumor development and invasion of tumor cells. Matrix metalloproteinases (MMPs) are a family of metalloproteinases capable of digesting ECM components and are important molecules for cell migration. Binding of ECM to integrins initiates cascades of cell signaling events modulating expression and activity of different MMPs. The aim of this study is to investigate fibronectin-integrin-mediated signaling and modulation of MMPs. Our findings indicated that culture of human cervical cancer cell (SiHa) on fibronectin-coated surface perhaps sends signals via fibronectin-integrin-mediated signaling pathways recruiting focal adhesion kinase (FAK) extracellular signal regulated kinase (ERK), phosphatidyl inositol 3 kinase (PI-3K), integrin-linked kinase (ILK), nuclear factor-kappa B (NF-kappaB), and modulates expression and activation of mainly pro-MMP-9, and moderately pro-MMP-2 in serum-free culture medium.

Inhibition of experimental choroidal neovascularization in rats by an av-integrin antagonist

PURPOSE

Integrin alpha(v)beta3 is predominantly expressed on endothelial cells in choroidal neovascularization (CNV). We evaluated the efficacy of cyclic RGD (Arg-Gly-Asp) peptide, an alpha(v)-integrin antagonist, in a rat model of laser-induced CNV METHODS: We evaluated the effect of cyclic RGD on the adhesion and cell viability of bovine choroidal endothelial cells (BCECs) by cell counting and the trypan blue dye exclusion test. CNV was induced by laser photocoagulation in female Long Evans rats (day 0), followed by intravitreal administration of one dose of cyclic RGD of 200 (n = 9), 100 (n = 10), 50 (n = 4), or 0 microg (n = 9) on days 9 and 11. We assessed the area of CNV by fluorescein angiography and the thickness microscopically on histologic sections. Neovascular vessels were detected by an antibody against factor VIII.

RESULTS

Cyclic RGD (0.02 to 200 microg/ml) inhibited adhesion of BCECs in a dose-dependent manner without changing the cell viability (p < 0.01). In eyes treated with two injections of 200 or 100 microg of cyclic RGD peptide, the development of CNV was significantly (p < 0.01) inhibited in the area of leakage on fluorescein angiography. Histologically, the CNV membrane was observed beneath the retina and the factor VIII-positive cells and red blood cells were involved. The thickness of the lesions was significantly (p < 0.01) reduced in eyes that received 200 or 100 microg of RGD.

CONCLUSIONS

Cyclic RGD effectively inhibited CNV progression in a rat model of laser-induced CNV, suggesting that this alpha(v)-integrin antagonist may be beneficial in the treatment of CNV.

Lentiviral-mediated miRNA against osteopontin suppresses tumor growth and metastasis of human hepatocellular carcinoma

In our previous study, osteopontin (OPN) was identified as one of the leading genes that promote the metastasis of hepatocellular carcinoma (HCC). However, the mechanism by which OPN promotes metastasis of HCC is not understood. In this study, RNA interference mediated by viral vectors-which could induce a long-lasting down-regulation in gene expression-was applied to analyze the role of OPN in metastasis of HCC. Three lentiviral vectors encoding microRNA against OPN, Lenti.OPNi-1, Lenti.OPNi-2, and Lenti.OPNi-3, were constructed and found to down-regulate the OPN level by 62%, 78%, and 95%, respectively, in HCCLM3 cells which had an overexpression of OPN and a higher metastatic potential. Consequently, both Lenti.OPNi-2 and Lenti.OPNi-3 induced a significant decrease in matrix metalloproteinase (MMP)-2 and urokinase plasminogen activator expression, and led to an obvious inhibition of both in vitro invasion and in vivo lung metastasis of HCCLM3 cells (P < 0.001). Moreover, Lenti.OPNi-3, rather than Lenti.OPNi-2, could also suppress in vitro proliferation and in vivo tumor growth of HCCLM3. Smaller detectable tumors were found in only 50% of mice after implantation of Lenti.OPNi-3-transfected HCCLM3 cells (341 +/- 502.6 mm(3) versus >3500 mm(3) in controls; P < 0.001). Lenti.OPNi-3, not Lenti.OPNi-2, significantly suppressed the MEK/ERK1/2 pathway in HCCLM3 cells. Recombinant OPN was found to induce translocation of p65 into the nucleus of HCC cells and activation of MMP-2 and MEK/ERK/1/2, which were suppressed by the nuclear factor kappaB (NF-kappaB) inhibitor pyrrolidine dithiocarbamate.

CONCLUSION

OPN plays an important role in metastasis as well as tumor growth of HCC, in which different minimum threshold levels of OPN are needed. These effects may occur through activation of the mitogen-activated protein kinase and NF-kappaB pathways, and MMP-2. OPN could be a hopeful target for the control of HCC.

Cysteine cathepsin non-inhibitory binding partners: modulating intracellular trafficking and function

Cysteine cathepsins play a fundamental role in tumor growth, invasion and migration, angiogenesis, and the metastatic cascade. Evidence of their overexpression in a wide array of human tumors has been well documented. Cysteine cathepsins seem to have a characteristic location-function relationship that leads to non-traditional roles such as those in development and pathology. For example, during tumor development, some cysteine cathepsins are found not just within lysosomes, but are also redistributed into presumptive exocytic vesicles at the cell periphery, resulting in their secretion. This altered localization contributes to non-lysosomal functions that have been linked to malignant progression. Mechanisms for altered localization are not well understood, but do include the interaction of cysteine cathepsins with binding partners that modulate intracellular trafficking and association with specific regions on the cell surface.

Matrix metalloproteinase-1 takes advantage of the induced fit mechanism to cleave the triple-helical type I collagen molecule

The collagenases are members of the matrix metalloproteinase family (MMP) that degrade native triple-helical type I collagen. To understand the mechanism by which these enzymes recognize and cleave this substrate, we studied the substrate specificity of a modified form of MMP-1 (FC) in which its active site region (amino acids 212-254) had been replaced with that of MMP-9 (amino acids 395-437). Although this substitution increased the activity of the enzyme toward gelatin and the peptide substrate Mca-PLGL(Dpa)AR-NH2 by approximately 3- and approximately 11-fold, respectively, it decreased the type I collagenolytic activity of the enzyme to 0.13%. The replacement of Gly233, the only amino acid in this region of FC that is conserved in all collagenase family members, with the corresponding Glu residue in MMP-9 resulted in a substantial decrease in the type I collagenolytic activity of the enzyme without affecting its general proteolytic activities. The kinetic parameters of the FC/G233E mutant for the collagen substrate were similar to those of the chimeric enzyme. In addition, substituting Gly233 for Glu in the chimera increased the collagenolytic activity of the enzyme by 12-fold. Interestingly, replacing Glu415 in MMP-9 with Gly, its corresponding residue in FC, endowed the enzyme with type I collagenolytic activity. The catalytic activity of the MMP-9 mutant toward triple-helical type I collagen was 2-fold higher than that of the collagenase chimera. These data in conjunction with the X-ray crystal structure of FC indicate that Gly233 provides the flexibility necessary for the enzyme active site to change conformation upon substrate binding. The flexibility provided by the Gly residue is essential for type I collagenolytic activity.

Methylselenol generated from selenomethionine by methioninase downregulates integrin expression and induces caspase-mediated apoptosis of B16F10 melanoma cells

Melanoma is a highly metastatic cancer resistant to current chemotherapeutic and radiotherapeutic approaches. Several studies have shown that interactions between cancer cells and the extracellular matrix (ECM) are critical for the survival and invasion of metastatic cancer cells. In this study, we examine the effects of methylselenol generated from selenomethionine (SeMet) by methioninase (METase) on cell proliferation, adhesion, and expression of integrins in murine melanoma B16F10 cells, which are metastatic in the lungs of syngeneic C57BL/6J mice. Combined treatment with SeMet-METase decreased the expression of integrins alpha(4), beta(1), alpha(nu), and beta(3), and inhibited melanoma-ECM adhesion. Caspase-mediated apoptosis was induced following loss of cell adherence. Phosphorylation of focal adhesion kinase (FAK) and Akt, related to integrin-mediated survival, were decreased upon treatment with SeMet-METase while phosphorylation of p38, PKC-delta, and IkappaBalpha increased. In the presence of specific inhibitors of p38, PKC-delta, and NF-kappaB, expression of integrins and cell adhesion to ECM were maintained and cell apoptosis was prevented in SeMet-METase-treated melanoma cells. Treatment with caspase inhibitors restored cell viability and blocked poly (ADP-ribose) polymerase (PARP) cleavage, but did not restore integrin expression and cell adhesion to ECMs reduced by SeMet-METase. Based on these results, we propose that combined treatment with SeMet-METase induces caspase-mediated apoptosis in melanoma cells by altering integrin expression and adhesion. Furthermore, activation of p38, PKC-delta, and NF-kappaB is a prerequisite for the down-regulation of integrin expression, followed by detachment-mediated apoptosis.

Transduction of beta3 integrin subunit cDNA confers on human keratinocytes the ability to adhere to gelatin

alphavbeta3 is a multiligand integrin receptor that interacts with fibrinogen (FG), fibrin (FB), fibronectin (FN), vitronectin (VN), and denatured collagen. We previously reported that cultured normal human keratinocytes, like in vivo keratinocytes, do not express alphavbeta3 on the cell surface, and do not adhere to and migrate on FG and FB. Furthermore, we reported that human keratinocytes transduced with beta3 integrin subunit cDNA by a retrovirus-mediated transduction method express alphavbeta3 on the cell surface and adhere to FG, FB, FN, and VN significantly compared with beta-galactosidase (beta-gal) cDNA-transduced keratinocytes (control). In this study, we determined whether these beta3 integrin subunit cDNA-transduced keratinocytes or normal human keratinocytes adhere to denatured collagen (gelatin) using a 1 h cell adhesion assay. beta3 cDNA-transduced keratinocytes adhered to gelatin, whereas no significant adhesion was observed with the control cells (beta-gal cDNA-transduced keratinocytes and normal human keratinocytes). The adhesion to gelatin was inhibited by LM609, a monoclonal antibody to alphavbeta3, and RGD peptides but not by normal mouse IgG1 nor RGE peptides. Thus, transduction of beta3 integrin subunit cDNA confers on human keratinocytes the ability to adhere to denatured collagen (gelatin) as well as to FG, FB, VN, and FN. Otherwise, normal human keratinocytes do not adhere to gelatin. These data support the idea that beta3 cDNA-transduced human keratinocytes can be a good material for cultured epithelium to achieve better take rate with acute or chronic wounds, in which FG, FB, and denatured collagen are abundantly present.

The type I collagen induction of MT1-MMP-mediated MMP-2 activation is repressed by alphaVbeta3 integrin in human breast cancer cells

The influence of alphaVbeta3 integrin on MT1-MMP functionality was studied in human breast cancer cells of differing beta3 integrin status. Overexpression of beta3 integrin caused increased cell surface expression of alphaV integrin and increased cellular adhesion to extracellular matrix (ECM) substrates in BT-549, MDA-MB-231 and MCF-7 cells. beta3 integrin expression also enhanced the migration of breast cancer cells on ECM substrates and enhanced collagen gel contraction. In vivo, alphaVbeta3 cooperated with MT1-MMP to increase the growth of MCF-7 cells after orthotopic inoculation in immunocompromised mice, but had no influence on in vitro proliferation. Despite these stimulatory effects, overexpression of beta3 integrin suppressed the type I collagen (Col I) induced MMP-2 activation in all breast cancer cell lines analyzed. This was also evident in extracts from the MCF-7 tumors in vivo, where MMP-2 activation was stimulated by MT1-MMP transfection, but attenuated with beta3 integrin expression. Although our studies confirm important biological effects of alphaVbeta3 integrin on enhancing cell adhesion and migration, ECM remodeling and tumor growth, beta3 integrin caused reduced MMP-2 activation in response to Col I in vitro, which appears to be physiologically relevant, as it was also seen in tumor xenografts in vivo. The reduction of MMP-2 activation (and thus MT1-MMP activity) by alphaVbeta3 in response to Col I may be important in scenarios where cells which are activated for matrix degradation need to preserve some pericellular collagen, perhaps as a substrate for cell adhesion and migration, thus maintaining a balanced level of proteolysis required for efficient tumor growth.

Reciprocal interactions between adhesion receptor signaling and MMP regulation

A predominant characteristic of metastatic cells is the ability to invade host tissues and establish distant metastatic foci. Release of metastatic cells from a primary tumor results from disruption of tissue architecture and requires reversible modulation of cell-matrix and cell-cell contacts, cytoskeletal rearrangement, and acquisition of enhanced proteolytic potential. Malignant cells produce a spectrum of extracellular proteinases including matrix metalloproteinases (MMPs) that process extracellular matrix components, cell surface proteins, and immune modulators. Dysregulated proteolysis has been implicated in tumor invasion and metastasis in multiple model systems. This review will focus on data that highlight the influence of cell-matrix and cell-cell interactions and their associated signal transduction pathways on proteinase regulation. These data highlight cell adhesion signaling as a mechanism for a versatile cellular proteolytic response to changing microenvironmental cues.

Alpha-V-dependent outside-in signaling is required for the regulation of CD44 surface expression, MMP-2 secretion, and cell migration by osteopontin in human melanoma cells

The level of integrin alpha(v)beta3 and its ligand osteopontin (OPN) has been directly correlated to tumorigenicity of melanoma and other cancer cells. We have previously shown an increase in pp(60c-Src) kinase activity associated with integrin alpha(v)beta3 in melanoma cells (M21) treated with soluble OPN. pp(60c-Src) kinase activity was not observed in melanoma cells expressing alpha(v) that lacks the cytoplasmic domain (alpha(v)995). Results of the current study demonstrate that the amino acid sequence '995RPPQEEQERE1004' in the beta-turn of alpha(v) chain is required for the interaction of pp(60c-Src). Our results suggest that the beta-turn of alpha(v) chain may be indispensable for alpha(v)-associated signaling complex formation and outside-in signaling. To further analyze the alpha(v)beta3 signaling in melanoma cells, we over expressed OPN in M21 cells (M21/OPN). CD44 surface expression and MMP-2 activity in the conditioned medium were increased to a greater extent in M21/OPN cells as compared with M21 or alpha(v)995 cells. Also, M21/OPN cells exhibit increased motility, which is markedly reduced upon treatment with inhibitors to alpha(v) and MMP-2. Our findings suggest that the increase in MMP-2 activity is integrin-dependent as MMP-2 activity is reduced in cells treated with an inhibitor to alpha(v) or in alpha(v)995 cells expressing mutant alpha(v).

Osteopontin: role in cell signaling and cancer progression

Cell migration and degradation of the extracellular matrix (ECM) are crucial steps in tumor progression. Several matrix-degrading proteases, including matrix metalloproteases, are highly regulated by growth factors, cytokines and ECM proteins. Osteopontin (OPN), a chemokine-like, calcified ECM-associated protein, plays a crucial role in determining the metastatic potential of various cancers. Since its first identification in bone, the multifaceted roles of OPN have been an area of intense investigation. Extensive research has elucidated the pivotal role of OPN in regulating the cell signaling that controls tumor progression and metastasis. This review focuses on recent advances in understanding the functional role of the OPN-induced signaling pathway in the regulation of cell migration and tumor progression and the implications for identifying novel targets for cancer therapy.

Metalloproteinases and their inhibitors in tumor angiogenesis

Angiogenesis is the process by which new blood vessels are formed from preexisting vasculature. It is an essential feature of the female reproductive cycle, embryonic development and wound repair. Angiogenesis has also been identified as a causal or contributing factor in several pathologies, including cancer, where it is a rate-limiting step during tumor progression. Matrix metalloproteinases (MMPs) are a family of soluble and membrane-anchored proteolytic enzymes that can degrade components of the extracellular matrix (ECM) as well as a growing number of modulators of cell function. Several of the MMPs, in particular the gelatinases and membrane-type 1 MMP (MT1-MMP), have been linked to angiogenesis. Potential roles for these proteases during the angiogenic process include degradation of the basement membrane and perivascular ECM components, unmasking of cryptic biologically relevant sites in ECM components, modulation of angiogenic factors and production of endogenous angiogenic inhibitors. This review brings together what is currently known about the functions of the MMPs and the closely related ADAM (a disintegrin and metalloproteinase domain) and ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) families in angiogenesis and considers how this information might be useful in manipulation of the angiogenic process, with a view to constraining tumor progression.

Bone microenvironment modulates expression and activity of cathepsin B in prostate cancer

Prostate cancers metastasize to bone leading to osteolysis. Here we assessed proteolysis of DQ-collagen I (a bone matrix protein) and, for comparison, DQ-collagen IV, by living human prostate carcinoma cells in vitro. Both collagens were degraded, and this degradation was reduced by inhibitors of matrix metallo, serine, and cysteine proteases. Because secretion of the cysteine protease cathepsin B is increased in human breast fibroblasts grown on collagen I gels, we analyzed cathepsin B levels and secretion in prostate cells grown on collagen I gels. Levels and secretion were increased only in DU145 cells--cells that expressed the highest baseline levels of cathepsin B. Secretion of cathepsin B was also elevated in DU145 cells grown in vitro on human bone fragments. We further investigated the effect of the bone microenvironment on cathepsin B expression and activity in vivo in a SCID-human model of prostate bone metastasis. High levels of cathepsin B protein and activity were found in DU145, PC3, and LNCaP bone tumors, although the PC3 and LNCaP cells had exhibited low cathepsin B expression in vitro. Our results suggest that tumor-stromal interactions in the context of the bone microenvironment can modulate the expression of the cysteine protease cathepsin B.

Antitumour effects of antiretroviral therapy

Infection by human immunodeficiency virus (HIV) is associated with an increased risk of certain tumours, particularly Kaposi's sarcoma, non-Hodgkin's lymphomas and cervical cancer. However, the incidence of these tumours in HIV-infected patients has decreased significantly since the widespread use of highly active antiretroviral therapy (HAART). This effect cannot be solely explained by the ability of these drugs to suppress HIV replication and thereby reconstitute the immune system. Recent studies have shown that inhibitors of the HIV aspartyl protease, which are widely used in HAART, have direct anti-angiogenic and antitumour effects that are unrelated to their antiviral activity. So these drugs might be used to treat cancer in patients who are not infected with HIV.

Inhibition of proprotein convertases enhances cell migration and metastases development of human colon carcinoma cells in a rat model

Although proprotein convertases are involved in tumor development, nothing is known about their role in metastatic dissemination. To investigate the involvement of convertase inhibition, we used human colon carcinoma cells overexpressing alpha1-antitrypsin Portland (alpha1-PDX, PDX39P cells), a potent convertase inhibitor. We previously reported that these cells bear uncleaved integrin alpha subunits and display an altered attachment to vitronectin that is correlated with defects in the intracellular signaling pathways activated by alphavbeta5 integrin ligation. In this study, we demonstrate that the inhibition of proprotein convertase activity either by overexpression of alpha1-PDX or with the synthetic inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone (dec-RVKR-cmk) led to a significant increase in cell migration supported by the alphavbeta5 integrin. A collagen gel invasion assay showed that PDX39P cells also displayed an invasive ability, contrary to control cells. Moreover, when injected to immunosuppressed newborn rats, PDX39P cells were highly invasive, as they induce 10 times more metastases than mock-transfected cells. In addition, the aggressiveness of PDX39P cells can be greatly reduced by a function-blocking monoclonal antibody (mAb) against the alphav subunit. It thus seems that inhibition of proprotein convertases enhances the in vivo invasiveness of colon tumor cells likely due to an increase in cell migration mediated by alphav integrins.

Osteopontin induces AP-1-mediated secretion of urokinase-type plasminogen activator through c-Src-dependent epidermal growth factor receptor transactivation in breast cancer cells

We have recently reported that osteopontin (OPN) stimulates cell motility and nuclear factor kappaB-mediated secretion of urokinase-type plasminogen activator (uPA) through phosphatidylinositol 3-kinase/Akt signaling pathways in breast cancer cells (Das, R., Mahabeleshwar, G. H., and Kundu, G. C. (2003) J. Biol. Chem. 278, 28593-28606). However, the role(s) of OPN on AP-1-mediated uPA secretion and cell motility and the involvement of c-Src/epidermal growth factor receptor (EGFR) in these processes in breast cancer cells are not well defined. In this study we report that OPN induces alpha(v)beta(3) integrin-mediated c-Src kinase activity in both highly invasive (MDA-MB-231) and low invasive (MCF-7) breast cancer cells. Ligation of OPN with alpha(v)beta(3) integrin induces kinase activity and tyrosine phosphorylation of EGFR in MDA-MB-231 and wild type EGFR-transfected MCF-7 cells, and this was inhibited by the dominant negative form of c-Src (dn c-Src) indicating that c-Src kinase plays a crucial role in this process. OPN induces association between alpha(v)beta(3) integrin and EGFR on the cell membrane in a macromolecular form with c-Src. Furthermore, OPN induces alpha(v)beta(3) integrin/EGFR-mediated ERK1/2 phosphorylation and AP-1 activation. Moreover, dn c-Src also suppressed the OPN-induced phosphatidylinositol (PI) 3-kinase activity in these cells indicating that c-Src acts as master switch in regulating MEK/ERK1/2 and phosphatidylinositol 3-kinase/Akt signaling pathways. OPN-induced ERK phosphorylation, AP-1 activation, uPA secretion, and cell motility were suppressed when cells were transfected with dn c-Src or pretreated with alpha(v)beta(3) integrin antibody, c-Src kinase inhibitor (pp2), EGFR tyrosine kinase inhibitor (PD153035), and MEK-1 inhibitor (PD98059). To our knowledge, this is the first report that OPN induces alpha(v)beta(3) integrin-mediated AP-1 activity and uPA secretion by activating c-Src/EGFR/ERK signaling pathways and further demonstrates a functional molecular link between OPN-induced integrin/c-Src-dependent EGFR phosphorylation and ERK/AP-1-mediated uPA secretion, and all of these ultimately control the motility of breast cancer cells.

Type I collagen-induced MMP-2 activation coincides with up-regulation of membrane type 1-matrix metalloproteinase and TIMP-2 in cardiac fibroblasts

Migration of cardiac fibroblasts is implicated in infarct healing and ventricular remodeling. Activation of matrix metalloproteinases induced by three-dimensional type I collagen, the principal component of the myocardial interstitium, is hypothesized to be essential for this migration. By utilizing primary cultures of cardiac fibroblasts and collagen lattice models, we demonstrated that type I collagen induced MMP-2 activation, and cells undergoing a change from isometric tension to mechanical unloading were associated with increased levels of total and active MMP-2 species. The collagen-induced MMP-2 activation coincided with up-regulated cellular levels of both membrane type 1-matrix metalloproteinase (MT1-MMP) and TIMP-2. A fraction of cellular membrane prepared from cells embedded in the collagen lattice containing active MT1-MMP and TIMP-2 was capable of activating pro-MMP-2, and exogenous TIMP-2 had a biphasic effect on this membrane-mediated MMP-2 activation. Interestingly, the presence of 43-kDa MT1-MMP species in a fraction of intracellular soluble proteins prepared from monolayer cells but not cells embedded in the lattices indicates that MT1-MMP metabolizes differently under the two different culture conditions. Treatment of cells embedded in the lattice with furin inhibitor attenuated pro-MT1-MMP processing and MMP-2 activation and impeded cell migration and invasion. These results suggest that the migration and invasion of cardiac fibroblasts is furin-dependent and that the active species of MT1-MMP and MMP-2 may be involved in both events.

Tendon cells produce gelatinases in response to type I collagen attachment

Cells that carry out wound healing must be able to perform catabolic as well as anabolic functions. As the tendon is a tissue rich in extracellular matrix (ECM) proteins, we hypothesized that cells which participate in tendon healing should be able to produce proteases that would allow the remodeling of such a tissue. To this end, we assessed the ability of endotenon cells isolated from canine flexor digitorum profundus tendon and from surrounding parietal sheath to produce the gelatinases MMP-2 and MMP-9. Endotenon and sheath cells cultured in vitro on polystyrene produced small amounts of MMP-2 and MMP-9 was not detectable. When cultured on polystyrene coated with type I collagen, the cells upregulated MMP-2 production and MMP-9 production was induced. No other ECM protein elicited this response nor did other cell lines respond in this way after attachment to type I collagen. The two gelatinases were identified by immunological methods, ability to bind gelatin, size, metal ion requirement, serine protease inhibitor insensitivity, and APMA activation. For cells grown on collagen-coated plastic, gelatinase upregulation was proportional to the amount of ligand present until saturation was reached. For any group of fresh tendon cells, MMP-2 and MMP-9 upregulation was greater in a three dimensional collagen gel than the highest response from the same group under two dimensional culture conditions. Attachment of the cells to type I collagen increased the ratio of active to inactive MMP-2. Dexamethasone inhibited the upregulation of both MMP-2 and MMP-9. These results show that ECM proteins can influence both the production and the state of activation of these matrix metalloproteinases.

Matrix metalloproteinase expression in breast cancer

BACKGROUND

Matrix metalloproteinases (MMPs) have been implicated as possible mediators of invasion and metastasis in some cancers. Our objective was to investigate which MMPs were constitutively expressed in breast tumor cells versus those that could be up-regulated by a number of agents known to affect MMP expression in other cell systems.

METHODS

We evaluated expression of MMPs 1-16 in breast tumor cell lines MDA-MB-231, T47D, and MCF-7 using semiquantitative RT-PCR and gelatin zymography. Exposure to 12-O-tetradecanoylphorbal-3-acetate (TPA), concanavalin-A (Con-A), the fibronectin-mimetic peptide GRGDSP (RGD), extracellular matrix (ECM) components, and anti-integrin antibodies was used to test for possible MMP up-regulation. Mitogen-activated protein kinase inhibitors (MAPK-I) were used to evaluate signal transduction pathways and regulation of MMP expression.

RESULTS

MMPs 1, 2, 7-11, 13, 14, and 16 were constitutively expressed in some tumor cell lines but not in normal breast epithelial cells. Administration of TPA, Con-A, and RGD increased the expression of MMPs 1, 2, 9, and 10. No MMP up-regulation was seen in MDA-MB-231 or MCF-7 after exposure to ECM components or after exposure to anti-integrin antibodies. MAPK-I had no effect on constitutive MMP expression but reduced or abolished the TPA up-regulation of MMP-9 in MDA-MB-231 and MCF-7.

CONCLUSIONS

Breast tumor cell lines constitutively express a number of MMPs. Because MMP expression can be up-regulated by Con-A, the fibronectin-mimetic peptide RGD, and TPA while being susceptible to inhibition by MAPK antagonists, MAPK signaling appears to play a role in this expression.

Amphiphysin1 inhibits vitronectin-mediated cell adhesion, spreading, and migration in vitro

To investigate the regulatory mechanism of cell adhesion, we have searched for cellular inhibitory factors which prevent cell adhesion. The brain cytosol was found to inhibit the adhesion of various transformed cells to the substratum. An inhibitory 120-kDa protein was purified by sequential column chromatography. Peptide sequencing revealed that the protein is identical to amphiphysin1. GST-amphiphysin1 suppressed the attachment of HeLa cells to the plate when cells were cultured in the serum-containing medium. Vitronectin, a major cell-adhesive protein in serum and a ligand to alpha(v)beta3 integrin, was responsible for this cell attachment, and the vitronectin action was blocked by GST-amphiphysin1. GST-amphiphysin1 also inhibited the vitronectin-mediated spreading and migration of malignant melanoma cells. Furthermore, GST-amphiphysin1 bound directly to vitronectin. These findings point to the interesting possibility that amphiphysin1 could be a useful tool to inhibit cell-adhesive vitronectin.

Role of integrin alpha(v)beta3 in the early phase of liver metastasis: PET and IVM analyses

To clarify the function of integrin alpha(v)beta3 in the early stage of liver metastasis, we investigated the interactions of metastatic cells with their target organ under the actual blood flow by using positron emission tomography (PET). The cells used were CHO-K1 cells and their transfectants bearing human integrin alpha(v)beta3 cDNA (alpha(v)beta3-CHO-K1 cells). The liver accumulation of alpha(v)beta3-CHO-K1 cells was significantly higher than that of CHO-K1 cells after injection via the portal vein, whereas no significant difference was observed in the lung accumulation after tail vein injection, suggesting a specific interaction of alpha(v)beta3-CHO-K1 cells with the hepatic sinusoids. Furthermore, to clarify the precise location of each cell in the liver, i.e., to determine whether individual cells were intravascularly localized or had extravasated, we performed intravital fluorescence microscopy (IVM) on the liver by using stable transfectants bearing the green fluorescent protein (GFP) gene, namely, GFP-CHO-K1 and GFP-alpha(v)beta3-CHO-K1 cells. Both types of cells remained in the hepatic blood vessels 1 h after injection via the portal vein. On the other hand, expression of integrin alpha(v)beta3 promoted the cells to reach the extravascular region after 24 h. These results suggest the possibility that the specific accumulation of alpha(v)beta3-CHO-K1 cells in the liver is followed by migration of the cells into the extravascular region. Interestingly, the adhesion of the two types of cells to hepatic sinusoidal endothelial cells in vitro did not correspond to in vivo accumulation of these cells. Therefore, integrin alpha(v)beta3 may function to promote extravasation of integrin alpha(v)beta3-expressing tumor cells in liver through a process possibly mediated by vitronectin produced by this organ.

Melanoma development and progression: a conspiracy between tumor and host

While a genome-centric paradigm in human cancer development was useful for the understanding of some malignancies such as leukemias, causative molecular defects intrinsic to melanocytes have not been defined in the majority of human melanomas. Recent work, however, has shown that regulatory signals governing melanocytic cell growth and differentiation may originate from the surrounding host cells either directly through physical contact or indirectly through soluble factors and extracellular matrix molecules. In this review, we present experimental systems useful for dissecting melanoma-host interactions and highlight evidence that the tumor microenvironment contributes to the oncogenic process. Thus, melanomagenesis is not merely an act of a single outlaw but a conspiracy orchestrated by multiple partners in the neighborhood who come into play in a precise spatiotemporal order. Defining intercellular molecular dialogues in human skin promises to provide key information for the development of novel treatment strategies that target the functional unit of stroma and tumor.

Interaction of human breast fibroblasts with collagen I increases secretion of procathepsin B

Interactions of stromal and tumor cells with the extracellular matrix may regulate expression of proteases including the lysosomal proteases cathepsins B and D. In the present study, we determined whether the expression of these two proteases in human breast fibroblasts was modulated by interactions with the extracellular matrix component, collagen I. Breast fibroblasts were isolated from non-malignant breast tissue as well as from tissue surrounding malignant human breast tumors. Growth of these fibroblasts on collagen I gels affected cell morphology, but not the intracellular localization of vesicles staining for cathepsin B or D. Cathepsins B and D levels (mRNA or intracellular protein) were not affected in fibroblasts growing on collagen I gels or plastic, nor was cathepsin D secreted from these cells. In contrast, protein expression and secretion of cathepsin B, primarily procathepsin B, was induced by growth on collagen I gels. The induced secretion appeared to be mediated by integrins binding to collagen I, as inhibitory antibodies against alpha(1), alpha(2), and beta(1) integrin subunits prevented procathepsin B secretion from fibroblasts grown on collagen. In addition, procathepsin B secretion was induced when cells were plated on beta(1) integrin antibodies. To our knowledge, this is the first examination of cathepsin B and D expression and localization in human breast fibroblasts and their regulation by a matrix protein. Secretion of the cysteine protease procathepsin B from breast fibroblasts may have physiological and pathological consequences, as proteases are required for normal development and for lactation of the mammary gland, yet can also initiate and accelerate the progression of breast cancer.

Metalloproteinase inhibitor attenuates neointima formation and constrictive remodeling after angioplasty in rats: augmentative effect of alpha(v)beta(3) receptor blockade

Release of matrix metalloproteinases (MMP) from smooth muscle and foam cells following arterial injury facilitates cell migration, neointimal hyperplasia, and vessel wall remodeling. Inhibition of MMP activity using the hydroxamate, zinc-chelating mimicers of collagen, Batimastat and Marimastat, has shown efficacy in reducing constrictive vascular remodeling 6 weeks after experimental angioplasty but not intimal hyperplasia. Vitronectin receptor (alpha(v)beta(3)) blockade interferes with binding of this integrin to MMP-2 and proteolyzed collagen, thereby reducing cell invasion. This study tests the effect of MMP inhibition, with and without vitronectin receptor (alpha(v)beta(3)) blockade, on neointima formation and arterial remodeling in a long-term model (up to 212 months) of balloon injury in vivo. Male Sabra rats were treated with Batimastat (BB-94, British Biotech Pharmaceuticals Ltd., 30 mg/kg, intraperitoneally) and/or the alpha(v)beta(3) receptor inhibiting RGD peptide, G-Pen-GRGDSPCA (GIBCO BRL, 0.1 micromol), administered as a perivascular gel to the common carotid artery after balloon injury. Animals were sacrificed 3, 14, 25, and 75 days (n=21, 23, 22, and 21) after injury. Animals treated with BB-94, peptide, or both had markedly increased absolute luminal area with markedly reduced luminal cross-sectional-area narrowing by neointima and intima-to-media area ratio at all time points except for 3 days after balloon injury versus non-treated, ballooned animals. Combined treatment was significantly more effective than either one alone. Constrictive remodeling, most marked 212 months after balloon injury, was prevented at this time point in all treated animals. The pattern of reduction in luminal narrowing, neointimal formation, and constrictive remodeling across treatment groups correlated very significantly with the reduction in tissue MMP activity as determined by zymography at 3 days. Confirmation of the efficacy of this strategy in larger animals should be the next step toward testing the applicability of this novel approach to the interventional setting.