Laminin-111 derived peptides AG73 and C16 regulate invadopodia activity of a human adenoid cystic carcinoma cell line

Adenoid cystic carcinoma is a frequently occurring malignant salivary gland neoplasm with high level of recurrence and distant metastasis long time after treatment. Metastatic tumor cells that actively migrate and invade surrounding tissues rely on invadopodia to degrade extracellular matrix (ECM) barriers. Invadopodia are actin-rich membrane protrusions that localize enzymes required for ECM degradation. Breakdown of ECM macromolecules releases fragments and bioactive peptides. We have already demonstrated that laminin-111 and its derived peptides regulate migration, invasion and protease activity of adenocarcinoma cells. Here we addressed the role of laminin-111 peptides AG73 and C16 in invadopodia activity of cells (CAC2) derived from human adenoid cystic carcinoma. CAC2 cells were treated by AG73 and C16, and subjected to fluorescent gelatin substrate degradation assay. In this assay invadopodia activity areas appear as black dots in a fluorescent background. Both peptides significantly increased invadopodia formation and activity compared to controls. We analyzed putative receptors and signaling pathways related to peptide effects. β1 integrin silencing by siRNA decreased AG73- and C16-induced invadopodia. Furthermore inhibition of Rac1 and ERK signaling pathways decreased both C16- and AG73-related invadopodia activities. We propose that laminin-111 peptides AG73 and C16 increase invadopodia activity in CAC2 cells through β1 integrin. Rac1 and ERK1/2 signaling pathways would transduce signals generated by both peptides.     

Matrix metalloproteinase activity synergizes with alpha2beta1 integrins to enhance collagen remodeling

Cell-matrix interactions transmit a wealth of information about the extracellular environment. In return, a variety of responses from the cell are initiated by changes in the matrix. One such response involves the positive regulation of matrix metalloproteinases (MMPs) by alpha2beta1 integrin attaching to a specific extracellular matrix component, collagen. This study explores the relationship between mechanical and biochemical functions of alpha2beta1 integrins as it pertains to regulating matrix remodeling. To understand this relationship, the individual influences of MMP activity and alpha2beta1 integrin function on collagen gel contraction were studied. We have observed little evidence of mutual participation in matrix remodeling by the alpha2beta1 integrin and MMP activity in cell models where alpha2 is minimally expressed. In cells expressing high levels of alpha2, we see an increase in gel contraction that is enhanced by MMP activity. Measuring tension as it builds within the gel reveals that alpha2beta1 integrin presence correlates with force output but is insensitive to MMP activity. These data strongly suggest that alpha2beta1 regulates collagen gel remodeling through multiple simultaneous mechanisms including force generation and modulation of MMP activity.     

Syndecan-1 and -4 differentially regulate oncogenic K-ras dependent cell invasion into collagen through α2β1 integrin and MT1-MMP

Syndecans function as co-receptors for integrins on different matrixes. Recently, syndecan-1 has been shown to be important for α2β1 integrin-mediated adhesion to collagen in tumor cells by regulating cell adhesion and migration on two-dimensional collagen. However, the function of syndecans in supporting α2β1 integrin interactions with three-dimensional (3D) collagen is less well studied. Using loss-of-function and overexpression experiments we show that in 3D collagen syndecan-4 supports α2β1-mediated collagen matrix contraction. Cell invasion through type I collagen containing 3D extracellular matrix (ECM) is driven by α2β1 integrin and membrane type-1 matrix metalloproteinase (MT1-MMP). Here we show that mutational activation of K-ras correlates with increased expression of α2β1 integrin, MT1-MMP, syndecan-1, and syndecan-4. While K-ras-induced α2β1 integrin and MT1-MMP are positive regulators of invasion, silencing and overexpression of syndecans demonstrate that these proteins inhibit cell invasion into collagen. Taken together, these data demonstrate the existence of a complex interplay between integrin α2β1, MT1-MMP, and syndecans in the invasion of K-ras mutant cells in 3D collagen that may represent a mechanism by which tumor cells become more invasive and metastatic.     

Syndecan-1-mediated cell spreading requires signaling by alphavbeta3 integrins in human breast carcinoma cells

Syndecans are cell surface heparan sulfate proteoglycans with regulatory roles in cell adhesion, proliferation, and differentiation [Annu. Rev. Biochem. 68 (1999) 729]. While the syndecan heparan sulfate chains are essential for matrix binding, less is known about the signaling role of their core proteins. To mimic syndecan-specific adhesion, MDA-MB-231 mammary carcinoma cells were plated on antibodies against syndecan-4 or syndecan-1. While cells adherent via syndecan-4 spread, cells adherent via syndecan-1 do not. However, cells adherent via syndecan-1 can be induced to spread by Mn(2+), suggesting that activation of a beta(1) or beta(3) integrin partner is required. Surprisingly, pretreatment of cells with a function-activating beta(1) antibody does not induce spreading, whereas function-blocking beta(1) integrin antibodies do, suggesting involvement of a beta(1)-to-beta(3) integrin cross-talk. Indeed, blockade of beta(1) integrin activation induces alpha(v)beta(3) integrin activation detectable by soluble fibrinogen binding. Spreading in response to syndecan-1 is independent of integrin-ligand binding. Furthermore, competition with soluble murine syndecan-1 ectodomain, which does not disrupt cell adhesion, nonetheless blocks the spreading mechanism. These data suggest that the ectodomain of the syndecan-1 core protein directly participates in the formation of a signaling complex that signals in cooperation with alpha(v)beta(3) integrins; signaling via this complex is negatively regulated by beta(1) integrins.     

RGD-independent cell adhesion via a tissue transglutaminase-fibronectin matrix promotes fibronectin fibril deposition and requires syndecan-4/2 and {alpha}5{beta}1 integrin co-signaling

Fibronectin (FN) deposition mediated by fibroblasts is an important process in matrix remodeling and wound healing. By monitoring the deposition of soluble biotinylated FN, we show that the stress-induced TG-FN matrix, a matrix complex of tissue transglutaminase (TG2) with its high affinity binding partner FN, can increase both exogenous and cellular FN deposition and also restore it when cell adhesion is interrupted via the presence of RGD-containing peptides. This mechanism does not require the transamidase activity of TG2 but is activated through an RGD-independent adhesion process requiring a heterocomplex of TG2 and FN and is mediated by a syndecan-4 and β1 integrin co-signaling pathway. By using α5 null cells, β1 integrin functional blocking antibody, and a α5β1 integrin targeting peptide A5-1, we demonstrate that the α5 and β1 integrins are essential for TG-FN to compensate RGD-induced loss of cell adhesion and FN deposition. The importance of syndecan-2 in this process was shown using targeting siRNAs, which abolished the compensation effect of TG-FN on the RGD-induced loss of cell adhesion, resulting in disruption of actin skeleton formation and FN deposition. Unlike syndecan-4, syndecan-2 does not interact directly with TG2 but acts as a downstream effector in regulating actin cytoskeleton organization through the ROCK pathway. We demonstrate that PKCα is likely to be the important link between syndecan-4 and syndecan-2 signaling and that TG2 is the functional component of the TG-FN heterocomplex in mediating cell adhesion via its direct interaction with heparan sulfate chains.     

A peptide derived from tenascin-C induces beta1 integrin activation through syndecan-4

Tenascin-C (TN-C) is unique for its cell adhesion modulatory function. We have shown that TNIIIA2, a synthetic 22-mer peptide derived from TN-C, stimulated beta1 integrin-mediated cell adhesion of nonadherent and adherent cell types, by inducing activation of beta1 integrin. The active site of TNIIIA2 appeared cryptic in the TN-C molecule but was exposed by MMP-2 processing of TN-C. The following results suggest that cell surface heparan sulfate (HS) proteoglycan (HSPG), including syndecan-4, participated in TNIIIA2-induced beta1 integrin activation: 1) TNIIIA2 bound to cell surface HSPG via its HS chains, as examined by photoaffinity labeling; 2) heparitinase I treatment of cells abrogated beta1 integrin activation induced by TNIIIA2; 3) syndecan-4 was isolated by affinity chromatography using TNIIIA2-immobilized beads; 4) small interfering RNA-based down-regulation of syndecan-4 expression reduced TNIIIA2-induced beta1 integrin activation, and consequent cell adhesion to fibronectin; 5) overexpression of syndecan-4 core protein enhanced TNIIIA2-induced activation of beta1 integrin. However, treatments that targeted the cytoplasmic region of syndecan-4, including ectopic expression of its mutant truncated with the cytoplasmic domains and treatment with protein kinase Calpha inhibitor G?6976, did not influence the TNIIIA2 activity. These results suggest that a TNIIIA2-related matricryptic site of the TN-C molecule, exposed by MMP-2 processing, may have bound to syndecan-4 via its HS chains and then induced conformational change in beta1 integrin necessary for its functional activation. A lateral interaction of beta1 integrin with the extracellular region of the syndecan-4 molecule may be involved in this conformation change.     

p190RhoGAP is the convergence point of adhesion signals from alpha 5 beta 1 integrin and syndecan-4

The fibronectin receptors alpha(5)beta(1) integrin and syndecan-4 cocluster in focal adhesions and coordinate cell migration by making individual contributions to the suppression of RhoA activity during matrix engagement. p190Rho-guanosine triphosphatase-activating protein (GAP) is known to inhibit RhoA during the early stages of cell spreading in an Src-dependent manner. This paper dissects the mechanisms of p190RhoGAP regulation and distinguishes the contributions of alpha(5)beta(1) integrin and syndecan-4. Matrix-induced tyrosine phosphorylation of p190RhoGAP is stimulated solely by engagement of alpha(5)beta(1) integrin and is independent of syndecan-4. Parallel engagement of syndecan-4 causes redistribution of the tyrosine-phosphorylated pool of p190RhoGAP between membrane and cytosolic fractions by a mechanism that requires direct activation of protein kinase C alpha by syndecan-4. Activation of both pathways is necessary for the efficient regulation of RhoA and, as a consequence, focal adhesion formation. Accordingly, we identify p190RhoGAP as the convergence point for adhesive signals mediated by alpha(5)beta(1) integrin and syndecan-4. This molecular mechanism explains the cooperation between extracellular matrix receptors during cell adhesion.     

Syndecan- and integrin-binding peptides synergistically accelerate cell adhesion

Integrins and syndecans mediate cell adhesion to extracellular matrix and their synergistic cooperation is implicated in cell adhesion processes. We previously identified two active peptides, AG73 and EF1, from the laminin α1 chain LG4 module, that promote cell attachment through syndecan- and α2β1 integrin-binding, respectively. Here, we examined time-dependent cell attachment on the mixed peptides AG73/EF1. The AG73/EF1 promoted stronger and more rapid cell attachment, spreading, FAK phosphorylation that reached a maximum at 20 min than that on AG73 (40 min) or EF1 (90 min) supplied singly. Thus, the syndecan- and α2β1 integrin-binding peptides synergistically affect cells and accelerate cell adhesion.     

Syndecan-1 signals independently of beta1 integrins during Raji cell spreading

Syndecan-1-expressing Raji lymphoid cells (Raji-S1 cells) bind and spread rapidly when attaching to matrix ligands that contain heparan sulfate-binding domains. However, these ligands also contain binding sites for integrins, which are widely known to signal, raising the question of whether the proteoglycan core protein participates in generation of the signal for spreading. To address this question, the spreading of the Raji-S1 cells is examined on ligands specific for either beta1 integrins, known to be present on the Raji cells, or the syndecan-1 core protein. The cells adhere and spread on invasin, a ligand that activates beta1 integrins, the IIICS fragment of fibronectin, which is a specific ligand for the alpha4beta1 integrin, or mAb281.2, an antibody specific for the syndecan-1 core protein. The signaling resulting from adhesion to the syndecan-specific antibody appears integrin independent as (i) the morphology of the cells spreading on the antibody is distinct from spreading initiated by the integrins alone; (ii) spreading on the syndecan or integrin ligands is affected differently by the kinase inhibitors tyrphostin 25, genistein, and staurosporine; and (iii) spreading on the syndecan-specific antibody is not disrupted by blocking beta1 integrin activation with mAb13, a beta1 inhibitory antibody. These data demonstrate that ligation of syndecan-1 initiates intracellular signaling and suggest that this signaling occurs when cells expressing syndecan-1 adhere to matrix ligands containing heparan sulfate-binding domains.     

Betaig-h3 interacts with alpha3beta1 integrin to promote adhesion and migration of human hepatoma cells

betaig-h3 is a TGF-induced extracellular matrix (ECM) protein. Our previous evidence suggests that beta ig-h3 may promote adhesion and invasion potential of human hepatoma cells, but the mechanism underlying this process is still unknown. The present study identifies a pivotal role for molecules of the beta ig-h3 signal transduction pathway. We demonstrated that beta ig-h3 co-immunoprecipitated with alpha 3beta 1 integrin in human 7721 hepatoma cells. The addition of alpha 3beta 1 integrin antibodies inhibited the elevated adhesion and migration in beta ig-h3-over-expressing 7721 cells, but not in beta ig-h3 siRNA transfected 7721 cells. The expression and activity of integrin downstream molecules FAK and paxillin show a positive correlation with beta ig-h3 expression in different human hepatoma cells. Levels of focal adhesions and stress fibers were decreased in beta ig-h3 siRNA transfected 7721 cells. We suggest that by interaction with alpha 3beta 1 integrin, beta ig-h3 activates FAK-paxillin signaling linkage, leads to cytoskeleton reorganization, and thus enhances the metastatic potentials of human hepatoma cells.     

MMP-2 functions as a negative regulator of chondrogenic cell condensation via down-regulation of the FAK-integrin beta1 interaction

Matrix metalloprotease-2 (MMP-2) has the capacity to degrade cartilage extracellular matrix molecules, the turnover of which is an essential event in chondrogenesis. Here, we investigated the functional role of MMP-2 in chondrogenesis of leg bud mesenchymal cells. Small interference RNA (siRNA)-mediated knockdown of mmp-2 promoted precartilage condensation and chondrogenesis. Treatment with bafilomycin A1, an MMP-2 activator, or GM6001, an MMP inhibitor, at the pre-condensation stage resulted in the inhibition or promotion of chondrogenesis, respectively. By comparison, treatment at the post-condensation stage had little or no effect on chondrogenesis. These results indicate that MMP-2 is involved in the regulation of cell condensation. Inhibition of MMP-2 activity by mmp-2 specific siRNA increased the protein level of fibronectin, and integrins alpha5 and beta1. The interaction between focal adhesion kinase (FAK) and integrin beta1 leading to tyrosine phosphorylation of FAK was also enhanced. Moreover, inactivation of p38MAPK down-regulated the level of MMP-2 mRNA and activity, and increased mesenchymal cell condensation in parallel with enhanced phosphorylation of FAK. Taken together, our data indicate that MMP-2 mediates the inhibitory signals of p38MAPK during mesenchymal cell condensation by functioning as a negative regulator of focal adhesion activity regulated by FAK via interactions with fibronectin through integrin beta1.     

Syndecan-2 overexpression regulates adhesion and migration through cooperation with integrin α2

Syndecan-2, a transmembrane heparan sulfate proteoglycan, is known to serve as an adhesion receptor, but details of the regulatory mechanism governing syndecan-2 cell adhesion and migration remain unclear. Here, we examined this regulatory mechanism, showing that overexpression of syndecan-2 enhanced collagen adhesion, cell migration and invasion of normal rat intestinal epithelial cells (RIE1), and increased integrin α2 expression levels. Interestingly, RIE1 cells transfected with either syndecan-2 or integrin α2 showed similar adhesion and migration patterns, and a function-blocking anti-integrin α2 antibody abolished syndecan-2-mediated adhesion and migration. Consistent with these findings, transfection of integrin α2 siRNA diminished syndecan-2-induced cell migration in HCT116 human colon cancer cells. Taken together, these results demonstrate a novel cooperation between syndecan-2 and integrin α2β1 in adhesion-mediated cell migration and invasion. This interactive dynamic might be a possible mechanism underlying the tumorigenic activities of colon cancer cells.     

The short arm of laminin gamma2 chain of laminin-5 (laminin-332) binds syndecan-1 and regulates cellular adhesion and migration by suppressing phosphorylation of integrin beta4 chain

The proteolytic processing of laminin-5 at the short arm of the gamma2 chain (gamma2sa) is known to convert this laminin from a cell adhesion type to a motility type. Here, we studied this mechanism by analyzing the functions of gamma2sa. In some immortalized or tumorigenic human cell lines, a recombinant gamma2sa, in either soluble or insoluble (coated) form, promoted the adhesion of these cells to the processed laminin-5 (Pr-LN5), and it suppressed their migration stimulated by serum or epidermal growth factor (EGF). Gamma2sa also suppressed EGF-induced tyrosine phosphorylation of integrin beta4 and resultant disruption of hemidesmosome-like structures in keratinocytes. Gamma2sa bound to syndecan-1, and this binding, as well as its cell adhesion activity, was blocked by heparin. By analyzing the activities of three different gamma2sa fragments, the active site of gamma2sa was localized to the NH(2)-terminal EGF-like sequence (domain V or LEa). Suppression of syndecan-1 expression by the RNA interference effectively blocked the activities of domain V capable of promoting cell adhesion and inhibiting the integrin beta4 phosphorylation. These results demonstrate that domain V of the gamma2 chain negatively regulates the integrin beta4 phosphorylation, probably through a syndecan-1-mediated signaling, leading to enhanced cell adhesion and suppressed cell motility.     

Requirement for tyrosine kinase-ERK1/2 signaling in alpha 1 beta 1 integrin-mediated collagen matrix remodeling by rat mesangial cells

Abnormal mesangial extracellular matrix remodeling by mesangial cells (MCs) is the hallmark of progressive glomerulonephritis (GN). We recently showed, using a type I collagen gel contraction assay, that alpha 1 beta 1 integrin-dependent MC adhesion and migration are necessary cell behaviors for collagen matrix remodeling. To further determine the mechanism of alpha 1 beta 1 integrin-mediated collagen remodeling, we studied the signaling pathways of MCs that participate in the regulation of collagen gel contraction. Immunoprecipitation and phosphotyrosine detection revealed that gel contraction is associated with the enhanced activity and phosphorylation of ERK1/2 by MCs. The tyrosine kinase inhibitors herbimycin and genistein inhibited collagen gel contraction dose dependently. Furthermore, targeting ERK1/2 activity with a MEK inhibitor, PD98059, and antisense ERK1/2 hindered gel contraction in a dose-dependent manner. Similar inhibitory effects on gel contraction and ERK1/2 phosphorylation were observed when MC-mediated gel contraction was performed in the presence of function-blocking anti-alpha1 or anti-beta1 integrin antibodies. However, cell adhesion and migration assays indicated that PD98059 and antisense ERK1/2 blocked alpha 1 beta 1 integrin-dependent MC migration, but did not interfere with collagen adhesion, although there was a marked decrease in ERK1/2 phosphorylation and ERK1/2 protein expression in cell adhesion on type I collagen. None of the above could affect membrane expression of alpha 1 beta 1 integrin. These results suggested that ERK1/2 activation is critical for the alpha 1 beta 1 integrin-dependent MC migration necessary for collagen matrix reorganization. We therefore conclude that ERK1/2 may serve as a possible target for pharmacological inhibition of pathological collagen matrix formation in GN.     

The function role and synergic effect of syndecan-1 for mifepristone in uterine leiomyoma

The study intends to investigate the regulation of syndecan-1 in human uterine leiomyoma cells. Human syndecan-1 levels were detected by Western blot in uterus leimyoma''s tissue. The efficacy of syndecan-1 silencing on the cell proliferation, metalloproteinases and extracellular matrix were determined through Cell Counting Kit (CCK8) assay and Western blot assay, respectively. We compared the respective and combined effect of mifepristone and syndecan-1 on cell proliferation and the expression of metalloproteinases and extracellular matrix (ECM) in human uterine leiomyoma cells. The inhibitory effects of Syndecan-1 silencing on proliferation, ECM and Matrix Metalloproteinase (MMP) were observed in human uterine leiomyoma cells. Furthermore, syndecan-1 inhibition enhanced the effects of mifepristone against uterine leiomyoma cell proliferation. The expression of MMPs and ECM components in human uterine leiomyoma cells was decreased dramatically after syndecan-1 silencing, which was promoted after mifepristone treatment. Altogether, syndecan-1 silencing enhanced the efficacy of mifepristone on the uterine leiomyoma cell proliferation and ECM formation. Therefore, targeting syndecan-1 represents a novel therapeutic strategy to treat uterine leiomyoma.     

Fibronectin-tissue transglutaminase matrix rescues RGD-impaired cell adhesion through syndecan-4 and beta1 integrin co-signaling

Heterotropic association of tissue transglutaminase (TG2) with extracellular matrix-associated fibronectin (FN) can restore the adhesion of fibroblasts when the integrin-mediated direct binding to FN is impaired using RGD-containing peptide. We demonstrate that the compensatory effect of the TG-FN complex in the presence of RGD-containing peptides is mediated by TG2 binding to the heparan sulfate chains of the syndecan-4 cell surface receptor. This binding mediates activation of protein kinase Calpha (PKCalpha) and its subsequent interaction with beta(1) integrin since disruption of PKCalpha binding to beta(1) integrins with a cell-permeant competitive peptide inhibits cell adhesion and the associated actin stress fiber formation. Cell signaling by this process leads to the activation of focal adhesion kinase and ERK1/2 mitogen-activated protein kinases. Fibroblasts deficient in Raf-1 do not respond fully to the TG-FN complex unless either the full-length kinase competent Raf-1 or the kinase-inactive domain of Raf-1 is reintroduced, indicating the involvement of the Raf-1 protein in the signaling mechanism. We propose a model for a novel RGD-independent cell adhesion process that could be important during tissue injury and/or remodeling whereby TG-FN binding to syndecan-4 activates PKCalpha leading to its association with beta(1) integrin, reinforcement of actin-stress fiber organization, and MAPK pathway activation.     

Importance of syndecan-4 and syndecan -2 in osteoblast cell adhesion and survival mediated by a tissue transglutaminase-fibronectin complex

Tissue transglutaminase (TG2) has been identified as an important extracellular crosslinking enzyme involved in matrix turnover and in bone differentiation. Here we report a novel cell adhesion/survival mechanism in human osteoblasts (HOB) which requires association of FN bound TG2 with the cell surface heparan sulphates in a transamidase independent manner. This novel pathway not only enhances cell adhesion on FN but also mediates cell adhesion and survival in the presence of integrin competing RGD peptides. We investigate the involvement of cell surface receptors and their intracellular signalling molecules to further explore the pathway mediated by this novel TG-FN heterocomplex. We demonstrate by siRNA silencing the crucial importance of the cell surface heparan sulphate proteoglycans syndecan-2 and syndecan-4 in regulating the compensatory effect of TG-FN on osteoblast cell adhesion and actin cytoskeletal formation in the presence of RGD peptides. By use of immunoprecipitation and inhibitory peptides we show that syndecan-4 interacts with TG2 and demonstrate that syndecan-2 and the α5β1 integrins, but not α4β1 function as downstream modulators in this pathway. Using function blocking antibodies, we show activation of α5β1 occurs by an inside out signalling mechanism involving activation and binding of protein kinase PKCα and phosphorylation of focal adhesion kinase (FAK) at Tyr⁸⁶¹ and activation of ERK1/2.     

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.