Anti-alpha3 integrin antibody induces the activated form of matrix metalloprotease-2 (MMP-2) with concomitant stimulation of invasion through matrigel by human rhabdomyosarcoma cells

Biologically-active laminin-111 fragment that modulates the epithelial-to-mesenchymal transition in embryonic stem cells

The dynamic interplay between the extracellular matrix and embryonic stem cells (ESCs) constitutes one of the key steps in understanding stem cell differentiation in vitro. Here we report a biologically-active laminin-111 fragment generated by matrix metalloproteinase 2 (MMP2) processing, which is highly up-regulated during differentiation. We show that the β1-chain-derived fragment interacts via α3β1-integrins, thereby triggering the down-regulation of MMP2 in mouse and human ESCs. Additionally, the expression of MMP9 and E-cadherin is up-regulated in mouse ESCs--key players in the epithelial-to-mesenchymal transition. We also demonstrate that the fragment acts through the α3β1-integrin/extracellular matrix metalloproteinase inducer complex. This study reveals a previously unidentified role of laminin-111 in early stem cell differentiation that goes far beyond basement membrane assembly and a mechanism by which an MMP2-cleaved laminin fragment regulates the expression of E-cadherin, MMP2, and MMP9.

Predicting and preventing melanoma invasiveness: advances in clarifying E2F1 function

Malignant melanoma of the skin is one of the most aggressive human cancers with increasing incidence, despite efforts to improve primary prevention. In particular, the prognosis of patients at late stages of the disease has not significantly improved in the last three decades, because systemic therapies have proven disappointing. Thus, metastatic melanoma continues to be a daunting clinical problem. The increasingly high rates of lethal outcome associated with advanced melanoma rely on the acquisition of invasiveness, early metastatic dissemination of tumor cells from their primary sites, and generation of chemoresistance as a consequence of alteration of key molecules involved in the regulation of cell survival. Thus far, extensive studies have been conducted to understand the molecular mechanisms that drive tumor progression, but the specific requirements underlying the aggressive behavior are still widely unknown. Understanding the determinants of this process is key to unveiling its dynamics, especially those that promote invasiveness, and may open new routes for the development of therapeutic strategies that control metastatic spread, and eventually the prevention of life-threatening metastases. Here, we review recent advances on molecular aspects, particularly of E2F1 transcription factor function, in the context of patient data, and discuss the implications for targeting melanoma cells when they begin to invade and metastasize.

Potentiation of cell invasion and matrix metalloproteinase production by alpha3beta1 integrin-mediated adhesion of gastric carcinoma cells to laminin-5

We previously reported that the adhesion of gastric carcinoma cells to the peritoneum mediated by the alpha3beta1 integrin-laminin interaction is a key step in the initial process of peritoneal metastatic dissemination. Carcinoma cells subsequently invade through the intercellular gaps of mesothelial linings. In this study, we examined the role of the interaction of carcinoma cells with laminin-5, which is a major component of submesothelial basement membranes and serves as a high-affinity ligand for alpha3beta1 integrin, in carcinoma cell invasion. Human gastric carcinoma cell lines (MKN1, GT3TKB, and NUGC-4) adhered in an alpha3beta1 integrin-dependent manner to the extracellular matrix deposited by peritoneal mesothelial cells. An in vitro invasion assay using the Boyden chamber system revealed that MKN1 cell migration through the membranes increased when the membranes were coated with matrices produced by mesothelial cells or with laminin-5-containing Matrigel as compared to Matrigel alone. The cell migration promoted by laminin-5-containing Matrigel was inhibited by the presence of anti-alpha3 integrin antibody. When MKN1 cells were cultured in a laminin-5-coated plate, these cells were promoted to produce matrix metalloproteinase (MMP)-9, as assessed by gelatin zymography, enzyme-linked immunosorbent assay, and reverse transcription-polymerase chain reaction. These results suggest that the production of MMP-9 by MKN1 cells was potentiated by the alpha3beta1 integrin-laminin-5 interaction, which facilitated their invasion via degradation of the matrix.

Proteolytic profiling of the extracellular matrix degradome

The profiling of protein function is one of the most challenging scientific tasks in the postgenomic age. Traditional protein expression methodologies have focused only on the quantification of proteins under varying conditions or pathologies. Determining the functional differences between protein populations allows for a more accurate view of the outcomes in normal vs diseased proteomes. Because the presence or absence of a protein's function can affect its complex surroundings (consisting of multiple other proteins and substrates), the study of proteome functionality yields information on protein-protein interactions, amplification cascades, signaling pathways, and posttranslational modifications. Of significant interest are proteinases, as proteolysis is responsible for tight regulation of various cellular and tissue processes. Proteinase activities, or lack there of, alter the proteome makeup by regulating other proteins or by generating cleavage products. This chapter describes current proteolytic profiling technologies using activity or target-based formats. In particular, the analysis of collagenolytic matrix metalloproteinase activity using fluorogenic triple-helical substrates is discussed.

A critical role for tetraspanin CD151 in alpha3beta1 and alpha6beta4 integrin-dependent tumor cell functions on laminin-5

The basement membrane protein laminin-5 supports tumor cell adhesion and motility and is implicated at multiple steps of the metastatic cascade. Tetraspanin CD151 engages in lateral, cell surface complexes with both of the major laminin-5 receptors, integrins alpha3beta1 and alpha6beta4. To determine the role of CD151 in tumor cell responses to laminin-5, we used retroviral RNA interference to efficiently silence CD151 expression in epidermal carcinoma cells. Near total loss of CD151 had no effect on steady state cell surface expression of alpha3beta1, alpha6beta4, or other integrins with which CD151 associates. However, CD151-silenced carcinoma cells displayed markedly impaired motility on laminin-5, accompanied by unusually persistent lateral and trailing edge adhesive contacts. CD151 silencing disrupted alpha3beta1 integrin association with tetraspanin-enriched microdomains, reduced the bulk detergent extractability of alpha3beta1, and impaired alpha3beta1 internalization in cells migrating on laminin-5. Both alpha3beta1- and alpha6beta4-dependent cell adhesion to laminin-5 were also impaired in CD151-silenced cells. Reexpressing CD151 in CD151-silenced cells reversed the adhesion and motility defects. Finally, loss of CD151 also impaired migration but not adhesion on substrates other than laminin-5. These data show that CD151 plays a critical role in tumor cell responses to laminin-5 and reveal promotion of integrin recycling as a novel potential mechanism whereby CD151 regulates tumor cell migration.

Culture of human cervical cancer cells, SiHa, in the presence of fibronectin activates MMP-2

PURPOSE

Several studies indicate that integrin receptors are involved in the regulation of matrix metalloproteinase (MMP) expression. Integrin-ECM ligand interaction leads to phosphorylation of focal adhesion kinase (FAK) and activation of mitogen activated protein kinase pathways. In this present communication, we cultured human cervical cancer cells, SiHa, in the presence of fibronectin to study fibronectin-integrin mediated modulation of MMP activity.

METHODS

SiHa cells were cultured in serum-free medium (SFCM) in the presence of fibronectin, SFCM was collected and gelatin zymography was performed. Western blot, RT-PCR and immunocytochemistry were performed with SiHa cells cultured in the presence of fibronectin.

RESULTS

The culture of SiHa cells in the presence of 50 microg/1.5 ml fibronectin led to expression of pro-MMP-9 and activation of MMP-2 within 2 h. When cells were treated with ERK inhibitor (PD98059) and grown in the presence of fibronectin MMP-2 activation was partially inhibited, but when cells were treated with PI-3K inhibitor (LY294002) and grown in the presence of fibronectin MMP-2 activation was appreciably reduced. Tyrosine phosphorylation of FAK, PI-3K and ERK and nuclear trafficking of ERK were increased in SiHa cells grown in the presence of fibronectin. Increased MT1-MMP mRNA expression and processing of MT1-MMP were also observed in SiHa cells grown in the presence of fibronectin.

CONCLUSIONS

Our findings indicate that the culture of SiHa cells in SFCM in the presence of fibronectin perhaps generates a signalling cascade which leads to the expression of pro-MMP-9 and the activation of MMP-2 within 2 h. The signalling pathways activated seem to be the FAK/ERK/PI-3K pathway.

Prostaglandin E2 enhances pancreatic cancer invasiveness through an Ets-1-dependent induction of matrix metalloproteinase-2

Accumulating evidence suggests an important role for cyclooxygenase-2 (COX-2) in the pathogenesis of a wide range of malignancies. Here we tested the hypothesis that the COX-2 product prostaglandin E(2) (PGE(2)) increases cellular invasive potential by inducing matrix metalloproteinase-2 (MMP-2) expression and activity through an extracellular signal-regulated kinase (ERK)/Ets-1-dependent mechanism in pancreatic cancer. PANC-1 and MIAPaCa-2 pancreatic cancer cells were treated with PGE(2) or rofecoxib, a selective COX-2 inhibitor. MMP-2 expression and activity were assayed using Western blot analysis and zymography, respectively. MMP-2 promoter activity was analyzed with a luciferase-based assay. Ets-1 activity was analyzed using gel shift assay. Ets-1 expression was specifically silenced using RNA interference. Cellular invasive and migratory potentials were determined using a Boyden chamber assay with or without Matrigel, respectively. Exogenous PGE(2) induced MMP-2 expression and activity and increased ERK1/2 phosphorylation, Ets-1 binding activity, and MMP-2 promoter activity. PGE(2) also increased cellular migratory and invasive potentials. The mitogen-activated protein kinase kinase inhibitor PD98059 and Ets-1 silencing each abolished PGE(2)-induced increases in MMP-2 expression. PD98059 and Ets-1 silencing each abrogated the effect of PGE(2) on cellular invasive potential but not on cellular migratory potential. Rofecoxib suppressed MMP-2 expression and activity, Ets-1 binding activity, MMP-2 promoter activity, and cellular migratory and invasive potentials. These results suggest that PGE(2) mediates pancreatic cancer cellular invasiveness through an ERK/Ets-1-dependent induction of MMP-2 expression and activity. They also suggest that COX-2 inhibition may represent a strategy to inhibit invasive potential in pancreatic cancer.

Different pattern of matrix metalloproteinases expression in alveolar versus embryonal rhabdomyosarcoma

BACKGROUND/PURPOSE

The matrix metalloproteinases (MMPs), a family of enzymes that degrade the extracellular matrix (ECM), are important in neoplastic cell invasion and metastasis. Data for rhabdomyosarcoma (RMS), the most frequent soft tissue sarcoma of childhood, are lacking. The aim of this study was to assess their expression in this tumor and to evaluate the correlation with clinicopathologic parameters.

METHODS

Immunohistochemical expression of MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, TIMP-1, and TIMP-2 was investigated in 33 human RMSs, 12 alveolar, and 21 embryonal histologic subtypes (12 high risk and 9 low/standard risk). Evaluation of the results was based on the percent of positive neoplastic cells and on staining intensity (negative, moderate, and strong). In situ zymography was carried out on 4 frozen RMS samples (2 alveolar and 2 high-risk embryonal).

RESULTS

Alveolar type showed a stronger MMP-1, -2 and -9 expression in comparison with embryonal (P = .006, P <.001, and P <.001, respectively). Intratumoral vessels and perivascular ECM were positive for MMP-9 in the majority of RMSs. Both TIMPs had negative results.

CONCLUSIONS

Gelatinases MMP-2 and MMP-9 and collagenase MMP-1 overexpression seem to contribute to the more aggressive phenotype of alveolar rhabdomyoblastic cells. Further characterization of the expression of MMPs and consequent utilization of their inhibitors in aggressive alveolar RMSs might lead to the development of novel anticancer therapies.

Adhesion of gastric carcinoma cells to peritoneum mediated by alpha3beta1 integrin (VLA-3)

The interaction between gastric carcinoma cells and the peritoneal lining is a key step in peritoneal dissemination. In this study, we examined the roles of the beta1 family of integrin receptors in the adhesion of such cells to the peritoneum. The adhesion of several gastric carcinoma cell lines to peritonea excised from mice was inhibited most by an anti-alpha3 integrin antibody and to a lesser extent by an anti-alpha2 integrin antibody. In the peritoneal implantation of NUGC-4 human gastric carcinoma cells in athymic mice, treatment of the cells with anti-alpha2 or anti-alpha3 integrin antibody reduced the number of disseminated nodules; suppression by the anti-alpha3 integrin antibody was stronger than that by the anti-alpha2 integrin antibody. The cDNAs to human alpha2 and alpha3 integrins were introduced into K562 leukemic cells, which were positive for the integrin beta1 subunit but negative for the alpha2 or alpha3 subunit. The alpha3 integrin-transfected cells adhered to excised peritoneum and to a monolayer of peritoneal mesothelial cells more firmly than did the alpha2 integrin-transfected cells or the mock transfectant. Reverse transcription-PCR was used to analyze the expression of laminin-5 and laminin-10/11, which have been reported to serve as high-affinity ligands for alpha3beta1 integrin. mRNA for these laminin isoforms was found in mesothelial cells from the diaphragm and parietal peritoneum. These results strongly suggest that alpha3beta1 integrin plays an essential role in mediating the initial attachment of cancer cells to the peritoneum, leading to the formation of peritoneal metastasis.

RETRACTED: Glucose transporter-1 gene expression is associated with pancreatic cancer invasiveness and MMP-2 activity

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors-in-Chiefs, because an investigation by Harvard Medical School and the Brigham and Women’s Hospital has concluded that Figure 3 is invalid and no underlying research data are available to resolve the discrepancies or validate the reported results.

Physiological and Pathological Roles of α3β1 Integrin

Alpha3beta1 integrin has been considered to be a mysterious adhesion molecule due to the pleiotropy in its ligand-binding specificity. However, recent studies have identified laminin isoforms as high-affinity ligands for this integrin, and demonstrated that alpha3beta1 integrin plays a number of essential roles in development and differentiation, mainly by mediating the establishment and maintenance of epithelial tissues. Furthermore, alpha3beta1 integrin is also implicated in many other biological phenomena, including cell growth and apoptosis, angiogenesis and neural functions. This integrin receptor forms complexes with various other membrane proteins, such as the transmembrane-4 superfamily proteins (tetraspanins), cytoskeletal proteins and signaling molecules. Recently, lines of evidence have been reported showing that complex formation regulates integrin functions in cell adhesion and migration, signal transduction across cell membranes, and cytoskeletal organization. In addition to these roles in physiological processes, alpha3beta1 integrin performs crucial functions in various pathological processes, especially in wound healing, tumor invasion and metastasis, and infection by pathogenic microorganisms.

Fibronectin-induced COX-2 mediates MMP-2 expression and invasiveness of rhabdomyosarcoma

Although accumulating evidence suggests the importance of cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)) in the pathogenesis of many cancers, the mechanism by which this enzyme and its metabolite promote cancer progression is unknown. In this study, we investigated the role of COX-2 in fibronectin-induced up-regulation of rhabdomyosarcoma matrix metalloproteinase (MMP)-2 activity and cellular invasiveness. We tested three human rhabdomyosarcoma cell lines: RMS559, RD, and SJRH30. Cell attachment to fibronectin up-regulated both COX-2 expression and PGE(2) production and concomitantly enhanced MMP-2 activity. Exogenous PGE(2) stimulated MMP-2 promoter activity, increased MMP-2 expression, and increased cellular invasiveness. Aspirin and rofecoxib (non-selective and selective COX-2 inhibitor, respectively) each abolished fibronectin-associated induction of MMP-2 and induced dose-dependent reductions in cellular invasiveness. These data implicated a role for inducible COX-2 and PGE(2) in the regulation of rhabdomyosarcoma cellular invasiveness and MMP-2 activity.

Glucose-induced changes in integrins and matrix-related functions in cultured human glomerular epithelial cells

In cultured human glomerular epithelial cells (HGEC), 25 mM glucose resulted in decreased expression of alpha(3)-, alpha(2)-, and beta(1)-integrins and increased expression of alpha(5)- and alpha(v)beta(3)-integrins. This change was accompanied by decreased binding of HGEC to type IV collagen. In the presence of normal (5 mM) glucose concentration, cell binding to type IV collagen was primarily mediated by alpha(2)beta(1)- and alpha(5)beta(1)-integrins, as indicated by experiments in which cell adhesion to type IV collagen was competed by specific anti-integrin monoclonal antibodies. In the presence of high (25 mM) glucose, the upregulated alpha(5)- and alpha(v)beta(3)-integrins were mainly involved in cell binding to type IV collagen. Furthermore, high glucose decreased expression of matrix metalloproteinase-2 (MMP-2), a collagenase regulated in part by alpha(3)beta(1)-integrin, as suggested by the use of ligand-mimicking antibodies against these integrins, which resulted in release of increased amounts of MMP-2 in the culture medium. Finally, tissue inhibitor of metalloproteinase-2, the specific inhibitor of MMP-2, was upregulated in high glucose and could contribute to matrix accumulation. These changes could help explain basement membrane thickening in diabetes.

Pro-collagen I COOH-terminal trimer induces directional migration and metalloproteinases in breast cancer cells

Breast and prostatic carcinomas, melanoma, and endothelial cell lines are chemoattracted by medium conditioned by mature osteoblasts. The chemoattractant for endothelial cells was identified with C3, carboxyl-terminal trimer of pro-collagen type I. We report that C3 induces directional migration and proliferation, the expression of tissue inhibitor of metalloproteinases-2, pro-metalloproteinase-2 and -9, and their activation in MDA MB231 cells, without changing the expression of tissue inhibitor of metalloproteinases-1 and of metalloproteinase-14. Antiserum against metalloproteinase-2 or -9 or -14, tissue inhibitor of metalloproteinases-1, or GM6001 inhibits the C3-induced migration. Urokinase and its receptor are detected and unchanged upon exposure to C3. The antibody against urokinase or addition of plasminogen activator inhibitor inhibits migration. Blocking antibodies to integrins alpha(2), alpha(6), beta(1), and beta(3) inhibit chemotaxis and do not change urokinase and urokinase receptor expression. Blockage of alpha(2), beta(1), and beta(3) integrins affect differently the induction by C3 of pro-metalloproteinase-2 and -9 and of tissue inhibitor of metalloproteinases-2. Chemotaxis to C3 is also inhibited by genistein, by pertussis toxin, which also inhibits C3-induced pro-metalloproteinase -2 and -9, but not urokinase expression. Wortmannin partially inhibits C3-induced cell migration. Other, but not all, breast carcinoma lines tested responded to C3 with migration and pro-metalloproteinase-2 induction. Presently C3 is the only agent known to induce migration specifically of both endothelial and breast carcinoma cells. The mitogenic and motogenic role of C3 in vitro might prefigure a role in in vivo carcinogenesis and in the establishment of metastasis.

Matrix metalloproteinase-2 is involved in A549 cell migration on laminin-10/11

We have reported that laminin-10/11 strongly promotes migration of A549 human lung carcinoma cells by activating the alpha3beta1 integrin-dependent signaling pathway. To elucidate the mechanism involved, we investigated whether matrix metalloproteinases (MMPs) are involved in cell migration on laminin-10/11. Here, we demonstrate that laminin-10/11, but not fibronectin which does not greatly promote A549 cell movement, stimulated MMP-2 secretion approximately 3-fold. The cell migration-promoting activity of laminin-10/11 was down-regulated by an MMP inhibitor. In addition, cell motility was significantly increased when cells adhered to a mixture of fibronectin and laminin-10/11 with a concomitant decrease of focal contacts, compared with those adhering to fibronectin alone. The enhanced cell migration was partially suppressed by the MMP inhibitor. Furthermore, an anti-alpha3 integrin, but not an anti-alpha5 integrin, antibody induced the activated form of MMP-2. These data suggest that MMP-2 may play an important role in A549 cell migration on laminin-10/11 through an alpha3beta1 integrin-dependent pathway.

Lack of matrix metalloproteinase (MMP)-1 and -3 expression in Ewing sarcoma may be due to loss of accessibility of the MMP regulatory element to the specific fusion protein in vivo

Ewing sarcoma is a malignant bone and soft tissue tumor of children and young adults, which is known to be highly aggressive and invasive. It expresses specific chimeric genes (EWS-FLI-1, EWS-ERG, EWS-ETV1, and EWS-E1AF), the 3' portions of which are all members of the ETS family. ETS-related proteins, such as FLI-1, ERG, and E1AF, transactivate the promoters of matrix metalloproteinase (MMP) genes, which play important roles in the processes of invasion and metastasis. Therefore, we hypothesize that the Ewing sarcoma-specific chimeric genes also transactivate the MMP genes, contributing to the tumor's invasiveness and propensity for metastasis. To verify this hypothesis, we investigated the expression of MMPs in eight Ewing sarcoma cell lines. Surprisingly, MMP-1 and MMP-3 were not expressed at all in any of the cell lines. MMP-9 was expressed in four out of the eight cell lines, and MMP-2 and MT1-MMP in all of the cell lines. Ewing sarcoma-specific chimeric genes have been shown to transactivate the promoter of the MMP-1 gene by the reporter assay, and bind to the putative recognition sites in the MMP regulatory elements by the gel shift assay. However, an in vivo formaldehyde cross-linking study revealed that the chimeric protein did not bind to the predicted ETS recognition sites in the regulatory elements of the MMPs. These results indicate that the absence of the MMP expression in the tumor cells is at least in part due to the loss of accessibility of the ETS recognition sites in the regulatory elements of the MMP genes. Therefore, we should be careful before theorizing simply that a putative binding site is essential for the transcription of critical genes, since the binding of this fusion protein was found to be modulated in tumor cells in this study.

An alternative processing of integrin alpha(v) subunit in tumor cells by membrane type-1 matrix metalloproteinase

Membrane type-1 matrix metalloproteinase (MT1-MMP) and alpha(v)beta(3) integrin are both essential to cell invasion. Maturation of integrin pro-alpha(v)chain (pro-alpha(v)) involves its cleavage by proprotein convertases (PC) to form the disulfide-bonded 125-kDa heavy and 25-kDa light alpha chains. Our report presents evidence of an alternative pathway of pro-alpha(v) processing involving MT1-MMP. In breast carcinoma MCF7 cells deficient in MT1-MMP, pro-alpha(v) is processed by a conventional furin-like PC, and the mature alpha(v) integrin subunit is represented by the 125-kDa heavy chain and the 25-kDa light chain commencing from the N-terminal Asp(891). In contrast, in cells co-expressing alpha(v)beta(3) and MT1-MMP, MT1-MMP functions as an integrin convertase. MT1-MMP specifically cleaves pro-alpha(v), generating a 115-kDa heavy chain with the truncated C terminus and a 25-kDa light chain commencing from the N-terminal Leu(892). PC-cleavable alpha(3) and alpha(5) but not the PC-resistant alpha(2) integrin subunit are also susceptible to MT1-MMP cleavage. These novel mechanisms involved in the processing of integrin alpha subunits underscore the significance and complexity of interactions between MT1-MMP and adhesion receptors and suggest that regulation of integrin functionality may be an important role of MT1-MMP in migrating tumor cells.

Matrix metalloproteinase-2 and -9 in bile as a marker of liver metastasis in colorectal cancer

Matrix metallproteinases (MMP)-2 and -9 are associated with cancer invasion and metastasis. MMP-2 and MMP-9 activities have never been assayed in bile. In the present study we investigated whether MMP-2 and -9 activities in the bile could be a marker for evaluation of liver metastasis in colorectal cancer. Fifty-three patients underwent colorectal resection for histologically verified adenocarcinoma. Twenty-six patients had colorectal cancer without liver metastasis and 27 patients had metastatic liver tumor. Six patients were studied as carcinoma-free control. MMP-2 and MMP-9 activities were assayed in bile using gelatin zymography and quantitated. Active MMP-2 activity of colorectal cancer with liver metastasis group (24.1 +/- 2.5 pixel count) was significantly higher than that of colorectal cancer without liver metastasis group (11.4 +/- 1.3 pixel count) (P < 0.001) or of control group (6.4 +/- 1.0 pixel count) (P < 0.001). Active MMP-9 was not detected in bile. ProMMP-9 activity of colorectal cancer with liver metastasis group (530.3 +/- 127.5 pixel count) was significantly higher than that of colorectal cancer without liver metastasis group (213.9 +/- 33.2 pixel count) (P = 0.008). This is the first report showing that the levels of active MMP-2 and proMMP-9 in bile were significantly higher in liver metastasis of colorectal cancer than in metastasis-free colorectal cancer. The results suggest that activities of active MMP-2 and proMMP-9 in the bile may be useful markers for predicting liver metastasis in colorectal cancer.

Urokinase receptors promote beta1 integrin function through interactions with integrin alpha3beta1

The urokinase receptor (uPAR) is linked to cellular migration through its capacity to promote pericellular proteolysis, regulate integrin function, and mediate cell signaling in response to urokinase (uPA) binding. The mechanisms for these activities remain incompletely defined, although uPAR was recently identified as a cis-acting ligand for the beta2 integrin CD11b/CD18 (Mac-1). Here we show that a major beta1 integrin partner for uPAR/uPA signaling is alpha3. In uPAR-transfected 293 cells uPAR complexed (>90%) with alpha3beta1 and antibodies to alpha3 blocked uPAR-dependent vitronectin (Vn) adhesion. Soluble uPAR bound to recombinant alpha3beta1 in a uPA-dependent manner (K(d) < 20 nM) and binding was blocked by a 17-mer alpha3beta1 integrin peptide (alpha325) homologous to the CD11b uPAR-binding site. uPAR colocalized with alpha3beta1 in MDA-MB-231 cells and uPA (1 nM) enhanced spreading and focal adhesion kinase phosphorylation on fibronectin (Fn) or collagen type I (Col) in a pertussis toxin- and alpha325-sensitive manner. A critical role of alpha3beta1 in uPA signaling was verified by studies of epithelial cells from alpha3-deficient mice. Thus, uPAR preferentially complexes with alpha3beta1, promoting direct (Vn) and indirect (Fn, Col) pathways of cell adhesion, the latter a heterotrimeric G protein-dependent mechanism of signaling between alpha3beta1 and other beta1 integrins.

Phenotypic alterations in Caki-1 cells as a consequence of TIMP-1 overexpression

Maintenance of the extracellular matrix (ECM) is important for tissue integrity and cellular physiology. Normal ECM turnover is regulated by a balance between matrix metalloproteinases and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). In metastasis, this balance favours increased ECM degradation. The objective of this study was to determine the effects of TIMP-1 overexpression on the metastatic process. To this end, we stably transfected a renal carcinoma cell line, Caki-1, with TIMP-1, using a pRc/CMV expression plasmid and LIPOFECTAMINE transfection reagent. The resultant clones displayed increased adhesion on the ECM substratum, including collagen type IV and laminin, and altered invasive capacity through fibronectin and Matrigel, dependent upon the level of TIMP-1 expression. These changes were not due to altered integrin expression, as assessed by flow cytometry. As well as protease inhibitory activity, TIMPs can influence cell proliferation and cell survival. The TIMP-1 clones displayed no changes in proliferation under normal growth conditions, compared with Caki-1 cells. However, under reduced serum conditions, the TIMP-1 clones had a greater percentage of cells in both S (P<0.05) and G(2)/M (P<0.005) phases and less cells in G(0)/G(1) (P<0.001) of the cell cycle than Caki-1 cells. The results confirm a dual role for TIMP-1 in invasion and metastasis, and provide further clues behind the molecular mechanisms in these processes.

Rac1 mediates type I collagen-dependent MMP-2 activation. role in cell invasion across collagen barrier

Cell migration and proteolysis are two essential processes during tumor invasion and metastasis. Matrix metalloproteinase (MMP)-2 (type IV collagenase; gelatinase A), is implicated in tumor metastasis as well as in primary tumor growth. The Rho family of small GTPases regulates the dynamics of actin cytoskeleton associated with cell motility. In this report, we provide evidence that Rac1, one member of Rho-related small GTPases, is a mediator of MMP-2 activation in HT1080 fibrosarcoma cells cultured in three-dimensional collagen gel (3D-col) and that MMP-2 activation is required for Rac1-promoted cell invasion through collagen barrier. Stable expression of dominant negative (Rac1V12N17) and constitutively active Rac1 (Rac1V12), respectively, in HT1080 cells demonstrates that Rac1 promoted cell invasiveness across type I collagen and collagen-dependent MMP-2 activation. Active Rac1 is sufficient to induce MMP-2 activation in cells cultured in fibrin gel, an extracellular matrix component that does not support MMP-2 activation. The Rac1-dependent MMP-2 activation occurred in a cell-associated fashion and required MMP activities. Because the cell membrane-mediated MMP-2 activation requires MT1-MMP and low amount of issue inhibitor of matrix metalloproteinase-2 (TIMP-2), their expression was examined. Rac1 modulated MT1-MMP mRNA level and the accumulation of a 43-kDa form of MT1-MMP protein, in correlation with MMP-2 activation profile. However, TIMP-2 expression was independent of Rac1 activity. The coordinate modulation of MMP-2 activity and MT1-MMP expression/processing by Rac1 is consistent with cell collagenolytic activity. The C-terminal hemopexin-like domain of MMP-2, which interferes with the cell membrane activation of MMP-2, reduced Rac1-promoted cell invasiveness as monitored by collagen invasion assay. These results suggest that collagen-dependent MMP-2 activation and MT1-MMP expression/processing contribute to Rac-promoted tumor cell invasion through interstitial collagen barrier.

Calreticulin is directly involved in anti-alpha3 integrin antibody-mediated secretion and activation of matrix metalloprotease-2

Matrix metalloprotease-2 (MMP-2) plays a pivotal role in cancer invasion and metastasis. Invasive human rhabdomyosarcoma cells (RD) secrete proMMP-2. We recently reported that anti-alpha3 integrin antibody induced the activated form of MMP-2 and enhanced proMMP-2 secretion by RD cells with concomitant enhancement of RD cell invasion. Since recent studies showed that calreticulin interacts with integrin alpha subunit, we hypothesized that calreticulin may be involved in signal transduction of anti-alpha3 integrin antibody-mediated MMP-2 secretion and activation. Here we demonstrate that anti-alpha3 integrin antibody induced a transient enhanced interaction of calreticulin with alpha3 integrin. Transfection of antisense oligonucleotides of calreticulin in RD cells abrogated the interaction between calreticulin and alpha3 integrin, and completely suppressed activation of MMP-2 and enhanced secretion of proMMP-2 induced by anti-alpha3 integrin antibody. Transient overexpression of calreticulin cDNA in RD cells significantly increased secretion of proMMP-2. The results demonstrate for the first time that calreticulin is directly involved in MMP-2 secretion and activation.

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

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

Differential expression of matrix metalloproteinases in labial salivary glands of patients with primary Sjögren's syndrome

OBJECTIVE

To determine the enzymatic activity and cellular localization of matrix metalloproteinases (MMPs) 2, 3, and 9 in labial salivary glands from patients with different degrees of severity of primary Sjogren's syndrome (primary SS).

METHODS

Gelatinase activity was determined by zymography and quantified by densitometry. The specificity of MMPs was determined using protease inhibitors and chelators, as well as activators of the latent forms of these enzymes. The cellular localization of MMPs was carried out using monoclonal antibodies that recognize their latent and active forms.

RESULTS

Labial glands from control subjects and patients showed gelatinase activity for MMP-2 and MMP-9. Activation studies revealed that both enzymes were predominantly present in their latent forms. The highest levels of MMP-9 activity were detected in patients with severe, active, primary SS (except for patients with severe clinical symptoms for extended periods) and correlated with structural and functional glandular changes. MMP-2 activity was almost the same in patients and controls. MMPs were detected by immunolocalization only in acinar and ductal cells and were homogeneously distributed throughout patients' glands. MMP-2 and MMP-9 expression paralleled their gelatinase activity. MMP-3, detectable only with immunologic methods, was absent in control subjects but abundantly expressed in patients. Importantly, MMP protein levels in acinar and ductal cells were independent of either the presence or the proximity of mononuclear infiltrate cells.

CONCLUSION

MMP-3 and MMP-9 expression, as well as MMP-9 catalytic activity, were increased in tissue samples from SS patients in a manner that correlated with the severity of the disease. Most important, increased MMP activity stemmed from exocrine epithelial cells and was not due to infiltrating lymphocytes. Thus, changes in salivary glands as a consequence of proteolysis may lead to severe glandular destruction.

Overexpression of vacuolar ATPase 16-kDa subunit in 10T1/2 fibroblasts enhances invasion with concomitant induction of matrix metalloproteinase-2

Recent studies show that the vacuolar-type H(+)-ATPase (V-ATPase) 16 kDa subunit is expressed on plasma membrane of cancer cells. We hypothesized that V-ATPase 16 kDa subunit is directly involved in cell invasion. In the present study we established transfectants overexpressing V-ATPase 16 kDa subunit at the mRNA level, and found that these transfectants showed an enhanced invasiveness through matrigel with a concomitant increases in secretion of matrix metalloproteinase-2. Moreover, antisense oligonucleotides of the V-ATPase 16 kDa subunit suppressed invasive human A549 cell invasion with concomitant decreases in secretion of matrix metalloproteinase-2. The results suggest that the V-ATPase 16 kDa subunit is directly involved in cell invasion and that matrix metalloproteinase-2 is responsible for promoting the invasion by the V-ATPase 16 kDa subunit.

The expression of metalloproteinase-2, -9, and -14 and of tissue inhibitors-1 and -2 is developmentally modulated during osteogenesis in vitro, the mature osteoblastic phenotype expressing metalloproteinase-14

During osteogenesis, in vitro, of tibial-derived rat osteoblasts (ROB) and derived clones, changes occur in the interactions of mature osteoblasts with the endogenous extracellular matrix (ECM) and these culminate in the formation of tridimensional nodules, which become sites of mineral deposition. We investigated if these changes might be mediated by remodeling of ECM, and we focused our study on the neutral metalloproteinases (MMPs), known agents of matrix remodeling, and on their tissue inhibitors (TIMPs). We report that during in vitro differentiation, osteoblasts express the secreted MMP-2 and -9 and the membrane gelatinase MMP-14. These, along with the tissue inhibitors TIMP-1 and -2, are developmentally regulated according to the maturation stage of osteoblasts. Their levels change in a similar association with osteoblast phenotypic maturation in different populations of ROB, which take different times to complete osteogenesis in vitro. MMP-14 expression coincides in both cell populations with the mature osteoblastic phenotype and is localized in the cells forming nodules. MMP-2 and -9 are expressed diffusely in the osteoblast population. Developmentally associated changes in the activation of MMP-2 are detected, associated in their timing with the expression of MMP-14 in both populations of ROB, and MMP-14 activates pro-MMP-2 in vitro. Expression of messenger RNAs (mRNAs) for the three MMPs increases up to the time of nodule formation. At this stage, TIMP-1 mRNA levels are lowest. TIMP-2 mRNA decreases throughout osteogenesis. In situ hybridization in 7-day-old rat tibias shows the strongest expression of MMP-14 among osteogenic cells, in lining osteoblasts on the newly formed trabeculae under the growth plate, and on the endosteal surface of cortical bone. Our data support the concept that the developmentally regulated expression of MMP-14 triggers localized proteolysis within the osteogenic population, concomitant in vitro to nodule formation.

Functions of alpha3beta1 integrin

alpha3beta1 integrin is a laminin receptor with apparently diverse functions. In epithelial cells it acts as a receptor for the basement membrane, whereas in neuronal and possibly tumor cells it mediates migration. Interactions of alpha3beta1 integrin with tetraspanin proteins may provide clues to how it transduces signals that affect cell behavior.

Induction of matrix metalloproteinases MMP-1 and MMP-2 by co-culture of breast cancer cells and bone marrow fibroblasts

Two invasive breast cancer cell lines (MDA-MB-231 and BT-549) were found to be more adherent and have greater migratory capacity on bone marrow fibroblasts than three non-invasive cell lines (MCF-7, T47D and BT-483). Antibodies to the adhesion molecules CD44, E-cadherin, ICAM- 1, and integrin chains alpha2, alpha3, alpha4, alpha5, alpha6, alpha v, beta1, beta3 and beta7 failed to inhibit breast cancer cell migration through bone marrow fibroblasts. Inhibitors of matrix metalloproteases, 1, 10-phenanthroline, Ro-9790, TIMP-1 and TIMP-2 were able to attenuate the migration of MDA-MB-231 cells through bone marrow fibroblast monolayers suggesting a role for these enzymes in the migration of breast cancer cells through bone marrow adherent layers. Co-culture of MDA-MB-231 cells and bone marrow fibroblasts resulted in augmentation of the levels of the matrix metalloproteases MMP-1 and MMP-2 in culture supernatants. Soluble factors produced by bone marrow fibroblasts were responsible for the increase in MMP-1 levels. However, maximal MMP-2 production was dependent on direct contract between the breast cancer cells and the bone marrow fibroblasts. Modulation of MMP production by cell-cell contact or soluble factors suggests a mechanism by which breast cancer cells can enhance their ability to invade the bone marrow microenvironment.

Integrin alpha(3)-subunit expression modulates alveolar epithelial cell monolayer formation

We investigated expression of the alpha(3)-integrin subunit by rat alveolar epithelial cells (AECs) grown in primary culture as well as the effects of monoclonal antibodies with blocking activity against the alpha(3)-integrin subunit on AEC monolayer formation. alpha(3)-Integrin subunit mRNA and protein were detectable in AECs on day 1 and increased with time in culture. alpha(3)- and beta(1)-integrin subunits coprecipitated in immunoprecipitation experiments with alpha(3)- and beta(1)-subunit-specific antibodies, consistent with their association as the alpha(3)beta(1)-integrin receptor at the cell membrane. Treatment with blocking anti-alpha(3) monoclonal antibody from day 0 delayed development of transepithelial resistance, reduced transepithelial resistance through day 5 compared with that in untreated AECs, and resulted in large subconfluent patches in monolayers viewed by scanning electron microscopy on day 3. These data indicate that alpha(3)- and beta(1)-integrin subunits are expressed in AEC monolayers where they form the heterodimeric alpha(3)beta(1)-integrin receptor at the cell membrane. Blockade of the alpha(3)-integrin subunit inhibits formation of confluent AEC monolayers. We conclude that the alpha(3)-integrin subunit modulates formation of AEC monolayers by virtue of the key role of the alpha(3)beta(1)-integrin receptor in AEC adhesion.

Anti-beta4 integrin antibodies enhance migratory and invasive abilities of human colon adenocarcinoma cells and their MMP-2 expression

Integrin-mediated adhesion of cells to extracellular matrix proteins has been shown to activate various intracellular signaling events. In the present study, we demonstrate that the addition of a monoclonal antibody raised against the beta4 integrin subunit in the culture medium of a clone derived from the colon adenocarcinoma cell line LoVo specifically results in stimulation of cell migration and invasion through reconstituted basement membrane matrices. Moreover, an increase in MMP-2 activity is observed. Conversely, monoclonal anti-alpha6 and anti-beta1 have no effect on MMP-2 expression. The s. c. co-injection of adenocarcinoma cells with antibodies raised against the beta4 integrin subunit to immunosuppressed newborn rats gives rise to tumors displaying altered and disorganized peri-tumoral basement membranes compared with tumors obtained when cells are injected with adenocarcinoma cells alone. Higher metastatic capacity of cells results when they are co-injected with antibodies to the beta4 integrin subunit. Our results suggest that the beta4 subunit of alpha6beta4 integrin, a laminin receptor in colon adenocarcinoma, may be responsible for the specific signals which stimulate cell motility, expression of MMP-2 and tumor invasion.

Integrin alphavbeta3-RGDS interaction mediates fibrin-induced morphological changes of glomerular endothelial cells

BACKGROUND

In our previous studies, we found that intraglomerular deposition of fibrin and its metabolites was related to glomerular sclerosis and reduced renal function. It has been reported that both overlying and underlying fibrin may induce specific morphological changes of cultured endothelial cells from large blood vessels. The dependency of these morphological changes on the integrin alphavbeta3-arginyl-glycyl-aspartyl-serine (RGDS) interaction is still controversial. We hypothesized that glomerular endothelial cells (GECs) stimulated by fibrin might undergo morphological changes through an integrin alphavbeta3-RGDS interaction. Methods. In vitro studies were performed to examine the growing status of GECs stimulated by overlying and underlying fibrin gels in the presence or absence of the following: 50 microg/ml anti-alphavbeta3 integrin monoclonal antibody 23C6 or nonimmune mouse IgG, 1 mg/ml synthetic RGDS or arginyl-glycyl-glycyl-serine (RGGS) peptide, 10 mg/ml sodium heparin, 100 microg/ml cycloheximide, and 10 microM actinomycin D. Fast protein liquid chromatography (FPLC)-purified fibrinogen and the third to fifth passages of human GECs were also used in this study.

RESULTS

GECs developed capillary tube structure after 60 hours of culturing on fibrin gels, and GECs cultured on gelatin-coated plates displayed a monolayer of cobblestone-like cells in the presence or absence of 23C6 and synthetic RGDS peptide. Fibrin-induced capillary tube formation was promoted by 23C6 and inhibited by RGDS peptide, cycloheximide, and actinomycin D. Disorganization of the GEC monolayer was induced by overlying fibrin, but was not induced by overlying agarose gels and glass cover slips or culturing in fibrinogen, 0.05 NIH U/ml thrombin, fibrin supernatants, as well as in fibrin degradation products. Disorganization of GEC monolayer can be induced by both des-AA-fibrin and des-AABB-fibrin and was unaffected by heparin. Furthermore, both 23C6 and synthetic RGDS peptide prevented disorganization of GECs induced by overlying fibrin, whereas nonimmune mouse IgG, synthetic RGGS peptide, cycloheximide, and actinomycin D had no similar effect.

CONCLUSIONS

GECs cultured on fibrin gels may develop capillary structure spontaneously, and GECs covered by fibrin gels may undergo disorganization. Our data suggest that these GEC morphological changes are mediated by an integrin alphavbeta3-RGDS interaction.

Function of alpha3beta1-tetraspanin protein complexes in tumor cell invasion. Evidence for the role of the complexes in production of matrix metalloproteinase 2 (MMP-2)

Tumor cell migration through the three- dimensional extracellular matrix (ECM) environment is an important part of the metastatic process. We have analyzed a role played by the integrin-tetraspanin protein complexes in invasive migration by culturing MDA-MB-231 cells within Matrigel. Using time-lapse video recording, we demonstrated that the Matrigel-embedded cells remain round and exhibit only limited ability for migration by extending short, highly dynamic pseudopodia. The alpha3beta1-tetraspanin protein complexes were clustered on the thin microvilli-like protrusions extending from both the main cell body and pseudopodia. Ligation of the alpha3beta1-tetraspanin protein complexes with monoclonal antibodies specifically stimulates production of matrix metalloproteinase 2 (MMP-2) and induces formation of long invasive protrusions within Matrigel. Accordingly, treatment with the monoclonal antibodies to various tetraspanin proteins and to the alpha3 integrin subunit increases invasive potential of the MDA-MB-231 cells in the Matrigel-penetration assay. A specific inhibitor of phosphoinositide 3-kinase (PI3K), LY294002, negated the effect of the monoclonal antibodies on the morphology of the Matrigel-embedded cells and on production of MMP-2. Interestingly, broad-spectrum inhibitors of protein tyrosine kinases (genistein) and protein tyrosine phosphatases (orthovanadate), and actin filament stabilizing compound (jasplakinolide), also block protrusive activity of the Matrigel-embedded cells but have no effect on the production of MMP-2. These results indicate that alpha3beta1-tetraspanin protein complexes may control invasive migration of tumor cells by using at least two PI3K-dependent signaling mechanisms: through rearrangement of the actin cytoskeleton and by modulating the MMP-2 production.

MMP-2 release and activation in ovarian carcinoma: the role of fibroblasts

The matrix metalloproteinase MMP-2 is up-regulated in epithelial cancers and its mRNA localizes to stromal fibroblasts. In this paper we show that co-culture of ovarian carcinoma cells with fibroblasts resulted in an enhanced release of proMMP-2 and TIMP-2 into the culture medium. Cell-cell interaction was a major factor in this response and carcinoma cells stimulated proMMP-2 release from fibroblasts but not vice versa. Collagen 1, in a dose-dependent fashion, induced activation of proMMP-2 by tumour-derived, but not normal, fibroblasts. Antibody to beta1 integrin also induced proMMP-2 activation by tumour-derived fibroblasts. The activation involved the processing of proMMP-2 by a membrane-bound metalloproteinase. We propose that, in the ovarian tumour microenvironment, interaction between tumour cells and fibroblasts may enhance fibroblast production of the proMMP-2 and TIMP-2. Collagen I, also present in the ovarian tumours, then induces these fibroblasts to activate proMMP-2 even in the presence of TIMP-2. This active MMP-2 can associate with the cell surface of tumour cells and fibroblasts and is used in the processes of tissue remodelling and invasion.

Mechanisms for pro matrix metalloproteinase activation

The activation of pro matrix metalloproteinases (MMPs) by sequential proteolysis of the propeptide blocking the active site cleft is regarded as one of the key levels of regulation of these proteinases. Potential physiological mechanisms including cell-associated plasmin generation by urokinase-like plasminogen activator, or the action of cell surface MT1-MMPs appear to be involved in the initiation of cascades of pro MMP activation. Gelatinase A, collagenase 3 and gelatinase B may be activated by MT-MMP based mechanisms, as evidenced by both biochemical and cell based studies. Hence the regulation of MT-MMPs themselves becomes critical to the determination of MMP activity. This includes activation, assembly at the cell surfaces as TIMP-2 complexes and subsequent inactivation by proteolysis or TIMP inhibition.

The activation of ProMMP-2 (gelatinase A) by HT1080 fibrosarcoma cells is promoted by culture on a fibronectin substrate and is concomitant with an increase in processing of MT1-MMP (MMP-14) to a 45 kDa form

We have assessed the effect of fibronectin and laminin-1 on the expression of molecules involved in the activation pathway of MMP-2, a key proteinase in tissue remodelling. HT1080 fibrosarcoma cells cultured on fibronectin were shown to activate endogenous MMP-2, to a level comparable with that elicited by treatment with phorbol ester. In contrast, the MMP-2 expressed by HT1080 cells cultured on laminin-1 was mainly in the pro- (inactive form). Culture of the cells on peptide fragments of fibronectin derived from the central cell binding domain also promoted MMP-2 activation, indicating that signals via fibronectin binding to integrin receptors may be involved. HT1080 cells cultured on immobilised antibodies to the alpha5 and beta1 integrin subunits secreted levels of active MMP-2 similar to those observed for full length fibronectin, whereas cells cultured on an antibody to the alpha6 integrin subunit secreted mainly proMMP-2. The data demonstrate that the activation of MMP-2 by HT1080 cells is regulated by the nature of the extracellular matrix, and that signals via the alpha5beta1 integrin receptor may be involved in the fibronectin induced up-regulation of MMP-2 activation. We then assessed the effect of fibronectin on the components of the putative MT1-MMP/TIMP-2 ‘receptor’ complex implicated in MMP-2 activation. Levels of TIMP-2 protein expressed by HT1080 cells did not vary detectably between cells cultured on fibronectin or laminin-1. However, the expression of MT1-MMP protein was up-regulated when the cells were cultured on fibronectin, which could be attributed to an increase in levels of a truncated 45 kDa form. Parallel studies using gelatin zymography demonstrated that the up-regulation of the production of the 45 kDa band was concomitant with MMP-2 activation. Inhibitor studies revealed that the truncation of MT1-MMP to a 45 kDa form is MMP mediated, although not inhibited by TIMP-1. In vitro, the 45 kDa form could be generated by cleavage of membrane-bound native MT1-MMP with several recombinant MMPs, including both active MT1-MMP and MMP-2. The implication that either MMP-2 or MT1-MMP can process MT1-MMP to 45 kDa, raises the possibility that truncation of MT1-MMP represents a self-regulatory end-point in the activation pathway of MMP-2.

Enhancement of metastatic activity of colon cancer as influenced by expression of cell surface antigens

BACKGROUND

Cell surface antigens are contributory factors toward metastatic activity. There have been no detailed studies on changes in cell surface antigens of colon cancer cell lines. To control life-threatening metastasis, it is necessary to evaluate what types of changes in cell surface antigens exert an influence on metastatic activity.

MATERIALS AND METHODS

In vivo selection was performed using the human colon cancer-derived cell line KM12SM to obtain variants of metastatic activity. A murine spleen injection-liver metastasis procedure reflecting the latter half of the metastatic process was adopted and repeated four times. Flow cytometric analyses were carried out to detect expression of antigens: Lewis a (Lea), Lewis x (Lex), sialyl Lewis a (sLea), sialyl Lewis x (sLex), E-cadherin, CD44v6, integrin alpha2 (CD49b), integrin alpha3 (CD49c), integrin alpha4 (CD49d), integrin alpha5 (CD49e), and integrin beta1 (CD29).

RESULTS

In vivo selection produced variants with higher metastatic activity. In the original line KM12SM, sLea, E-cadherin, CD49b, CD49c, or CD29 were positive in more than 40% of the cells. After selection, the percentage of cells positive for Lea, sLea, and all examined integrins significantly increased. Lex, sLex, and CD44v6 increased slightly, while E-cadherin decreased slightly.

CONCLUSIONS

In vivo selection and flow cytometric analysis revealed that Lea, sLea, CD49b, CD49c, and CD29 appear to be involved in the increase of metastatic activity. The changes of integrin expression in this study suggest that integrins collaborate in the promotion of adhesion to an extracellular matrix.

Tumor and endothelial cell invasion of basement membranes. The matrigel chemoinvasion assay as a tool for dissecting molecular mechanisms

The spread of cancer cells from a primary tumor to distant organs is the major cause of death of cancer patients. Metastatic lesions are often resistent to cancer therapy because of the progressive phenotypic changes that they have undergone. Several genetic and epigenetic factors, both in the cell and in the host, contribute to the development of tumor progression towards metastases. In this review we will analyze the steps involved in tumor metastases, which can be potential targets for anti-metastatic therapy. One of the most critical events in cancer metastasis is the invasion of basement membranes. An assay which we developed over ten years ago, the matrigel "chemoinvasion" assay, has been a useful tool for studying the mechanisms involved in tumor and endothelial cell invasion of basement membranes and for the screening of anti-invasive agents. Here we will describe the assay and review some of the major results obtained with it.