Antisense RNA-induced reduction in murine TIMP levels confers oncogenicity on Swiss 3T3 cells

TIMP-2 expression modulates human melanoma cell adhesion and motility

Invasion of cells across extracellular matrix barriers requires attachment of cells to the matrix, creation of a proteolytic defect in the matrix, and migration of the cells through the defect. To date, alterations in the balance between matrix metalloproteinases (MMPs) and their inhibitors have been shown to alter cellular invasion only through effects on matrix degradation. We used a retroviral infection system to over- and underproduce tissue inhibitor of metalloproteinase-2 (TIMP-2) in human A2058 melanoma cells. Our results indicate that altering the balance of MMPs and TIMP-2 through genetic manipulation of TIMP-2 production modulates not only proteolysis of the extracellular matrix but also cell attachment to the extracellular matrix and motility of cells through matrix components. Altering the production of TIMP-2 also results in the ability of cells to form foci. These results implicate the MMPs and their inhibitors in all aspects of the cellular invasion cascade. This supports the hypothesis that highly invasive cell lines establish a balance of MMPs and inhibitors that is optimal for invasion, and alteration of this balance in either direction results in perturbation of the invasive phenotype.

Inhibition of growth of human tumor cells in nude mice by a metalloproteinase inhibitor

The effects of a new metalloproteinase inhibitor, BE16627B [L-N-(N-hydroxy-2-isobutylsuccinynamoyl)-seryl-L-valine, MW: 375.2] isolated from microbial cultures, on human tumor cell growth in nude mice were investigated. BE16627B inhibited metalloproteinases in enzyme assays, as well as gelatinolysis and collagenolysis in cell cultures. BE16627B at 100 micrograms/ml showed no apparent cytotoxicity to human tumor cells in culture and its LD50 in mice was more than 1,000 mg/kg (i.p.). The effects of BE16627B on the in vivo growth of 2 human tumor cell lines were examined: HT1080 fibrosarcoma, which overproduces metalloproteinases, and HCT116 colon carcinoma, which barely secretes metalloproteinases. When BE16627B was administered to mice at 2 mg/mouse/day by an osmotic pump implanted s.c. for 3 weeks from 1 week after i.v. inoculation of HT1080 cells, the number and size of nodules of HT1080 cells on the lung surface were reduced to 24.3 and 46.4%, respectively, of those of controls, and the increase in lung weight due to tumor-cell growth was inhibited 85.5% without body-weight loss. Moreover, BE16627B inhibited 71.2% of the growth of HT1080 cells inoculated s.c. into mice under the same conditions, but did not significantly inhibit the s.c. growth of HCT116 human colon-carcinoma cells. Thus, BE16627B inhibited metalloproteinase-dependent human tumor-cell growth as well as lung colonization without showing cytotoxicity in nude mice.

Antisense-mediated reduction in insulin-like growth factor-I receptor expression suppresses the malignant phenotype of a human alveolar rhabdomyosarcoma

The expression of the insulin-like growth factors (IGFs) and their receptors has been linked to cellular proliferation and tumorigenicity in a number of model systems. Since rhabdomyosarcoma cells express IGF-I receptors, an autocrine or paracrine loop involving this receptor and its ligands could be responsible in part for the growth characteristics of this tumor. To assess directly the role of the IGF-I receptor in rhabdomyosarcoma cell growth and tumorigenicity, a human alveolar rhabdomyosarcoma cell line with high IGF-I receptor expression was transfected with an amplifiable IGF-I receptor antisense expression vector. Four unique, transfected clones were analyzed and found to have reduced IGF-I receptor expression relative to the parental line. Integration of the antisense sequence was demonstrated by Southern blot analysis, and expression of antisense message in these clones was shown by S1 nuclease protection assay. Reduced IGF-I receptor surface expression in the transfectants was shown by decreased immunofluorescence with an IGF-I receptor monoclonal antibody and by decreased IGF-I binding as measured by Scatchard analysis. These clones had markedly reduced growth rates in vitro, impaired colony formation in soft agar, and failed to form tumors in immunodeficient mice when compared with vector-transfected clones. These results demonstrate that reduction of IGF-I receptor expression can inhibit both the in vitro and in vivo growth of a human rhabdomyosarcoma cell line and suggest a role for the IGF-I receptor in mediating neoplastic growth in this mesenchymally derived tumor.

Serum levels of a tissue inhibitor of metalloproteinases-1 (TIMP-1) in bladder cancer patients

Tissue inhibitors of metalloproteinases (TIMP-1 and -2) are common inhibitors of matrix metallo-proteinases (MMPs), thereby blocking degradation of extracellular matrix components. TIMP-1 and -2 have been reported to exhibit inhibitory activities against tumor invasion and metastasis. We measured the serum TIMP-1 levels in 16 healthy volunteers and in 69 patients with bladder cancer using a sandwich enzyme immunoassay, and evaluated the correlation between serum TIMP-1 levels and clinicopathological features. Patients with bladder cancer showed significantly higher serum TIMP-1 levels (251.1 +/- 96.0 ng/ml; p < 0.01) than those of healthy volunteers (168.5 +/- 33.2 ng/ml), and a positive correlation between the TIMP-1 level and invasion and metastasis was observed. This is considered to be the result of the reactive production of TIMP-1 in cancerous tissues. Thus, serum TIMP-1 levels may become a reliable clinical marker of the progression of bladder cancer.

Type-IV collagenase and tissue inhibitor of metalloproteinase in ovarian cancer tissues

OBJECTIVE

We examined the specific expression of gelatinase/type-IV collagenase and tissue inhibitor of metalloproteinase (TIMP) in clinical ovarian cancer tissue.

METHODS

Molecular weight-specific gelatinase/type-IV collagenase activity was examined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis in which substrate was included (zymography). The expression of TIMP mRNA was examined by Northern blot analysis.

RESULTS

Zymography revealed that in ovarian cancer the activity of a 92-kDa gelatinase/type-IV collagenase was always greater than that of a 64-kDa gelatinase/type-IV collagenase in contrast to the situation in the normal ovary. Northern blot analysis revealed no remarkable difference of TIMP mRNA expression between cancer and normal ovarian tissues.

CONCLUSIONS

These results indicate that the higher activity of the 92-kDa gelatinase/type-IV collagenase enzyme, relative to that of the 64-kDa enzyme, is involved in the malignant phenotype of ovarian cancer, while the inhibitor of these enzymes, TIMP, is distributed in a widespread fashion in the tissue, and its levels are not correlated with the malignancy.

Purification and characterization of two collagenase inhibitors from mouse sarcoma 180 conditioned medium

We have previously shown that mouse sarcoma 180 cells produce vascular endothelial growth factor [VEGF; Rosenthal et al., 1990, Growth Factors, 4: 53-59], an endothelial mitogen that stimulates angiogenesis. Recent reports have implicated metalloproteinases and their inhibitors in the regulation of vascular morphogenesis, tumor invasion, and metastasis. We report here that mouse sarcoma 180 cells produce two collagenase inhibitors. These inhibitors were purified by heparin-Sepharose affinity chromatography, gel filtration, and C4 reverse phase h.p.l.c. Analytical gel electrophoresis of the purified inhibitors (MS-22 and MS-31) revealed molecular masses of 22,000 and 31,000 Da under reducing conditions, and 20,000 and 30,000 Da under nonreducing conditions, respectively. The NH2-terminal amino acid sequence of MS-22 was identical to that of tissue inhibitor of metalloproteinases type 2 (TIMP-2) produced by human melanoma cells [Stetler-Stevenson et al., 1989, J. Biol. Chem. 264: 17374-17378) over the first 30 amino acids. The NH2-terminal amino acid sequence of MS-31 was identical to that of murine TIMP-1 [Gewert et al., 1989, EMBO J 6:651-657]. Statistical analysis of the amino acid composition data of these two mouse sarcoma 180-derived collagenase inhibitors confirms the identification of MS-22 as TIMP-2 and MS-31 as TIMP-1.

Expression and localization of matrix-degrading metalloproteinases during colorectal tumorigenesis

The metalloproteinase matrilysin is widely expressed in the epithelial tumor cells of malignant colorectal adenocarcinomas. Approximately 50% of benign adenomas also express low levels of matrilysin that is focally localized. The expression of stromelysin-1, stromelysin-3, and gelatinase A was observed in the stromal component of several carcinomas and was not present in adenomatous tissue. The expression of interstitial collagenase and gelatinase B was observed in occasional adenomas and carcinomas. Stromelysin-2 transcripts were not detectable in any of the samples examined. Tissue inhibitor of metalloproteinase-1 gene expression was widespread and was observed in both epithelial and stromal cells of adenomas and carcinomas. These results indicate that matrilysin gene expression is an early event in colorectal tumorigenesis and that the expression of stromelysin-1, stromelysin-3, and gelatinase A is primarily a late event. The observed gene expression patterns suggest that matrilysin may participate in early events in tumor progression and that multiple members of the metalloproteinase family may work in concert to facilitate late-stage tumor invasion and metastasis.

TIMP-1 protein expression is stimulated by IL-1 beta and IL-6 in primary rat hepatocytes

Degradation of extracellular matrix proteins is performed by metalloproteinases which are inhibited by tissue inhibitors of metalloproteinases (TIMP). We expressed the murine TIMP-1 protein in E. coli and prepared a polyclonal antiserum against the recombinant protein. Using this antiserum we studied the biosynthesis and glycosylation of murine TIMP-1 protein in COS-7 cells transfected with a TIMP-1 expression plasmid by metabolic labeling and indirect immunofluorescence studies. In primary rat hepatocytes we show for the first time that TIMP-1 protein expression is up-regulated upon stimulation with IL-1 beta and IL-6. Since TIMP-1 is induced during the acute phase reaction it could possibly be involved in the pathogenesis of liver fibrosis.

Gene encoding a novel murine tissue inhibitor of metalloproteinases (TIMP), TIMP-3, is expressed in developing mouse epithelia, cartilage, and muscle, and is located on mouse chromosome 10

Remodeling of the extracellular matrix (ECM) is an essential component of normal development and is also involved in the pathogenesis of arthritis and the spread of cancer. The matrix metalloproteinases and their natural inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), play an important role in this context. We have isolated mouse cDNA clones encoding a novel member of the TIMP family, designated TIMP-3. We have assigned the Timp-3 locus to the [C1-D1] region of mouse chromosome 10 using both genetic and cytogenetic methods. The conceptual translation product of the Timp-3 cDNA shows a high degree of similarity with ChIMP-3, a recently cloned chicken metalloproteinase inhibitor, as well as significant structural similarity with the amino acid sequences of the previously isolated members of this family, TIMP-1 and TIMP-2. The pattern of expression of Timp-3 in the developing mouse embryo is distinct from that previously reported for Timp-1. Timp-3 is expressed in cartilage and skeletal muscle, in myocardium, in the skin, oral and nasal epithelium, in the newborn mouse liver, in the epithelium of some tubular structures such as the developing bronchial tree, oesophagus, colon, urogenital sinus, bile duct, in the kidney, salivary glands, and in the choroid plexus of the brain. The patterns of Timp-3 expression in surface epithelia and in the epithelial lining of many tubular organs suggests that TIMP-3 may be involved in regulating ECM remodeling during the folding of epithelia and during the formation, branching, and expansion of epithelial tubes. In the mouse placenta, expression is seen in the trophoblast, raising the possibility that TIMP-3 may be involved in regulating trophoblastic invasion of the uterus. We propose a role for TIMP-3 in musculoskeletal and cardiac development, in the morphogenesis of certain epithelial structures, and placental implantation.

Inhibition of angiogenesis by tissue inhibitor of metalloproteinase

Matrix proteases play a critical role in cell invasion and migration, including the process of angiogenesis. The ability of specific factors to induce angiogenic responses correlates with their stimulation of matrix protease synthesis and release. Using an in vivo angiogenesis assay, the endothelial cell response to known angiogenic factors, basic fibroblast growth factor (bFGF) and adipocyte conditioned medium, was blocked by an inhibitor of matrix metalloproteinase activity, TIMP-1. The TIMP effect was mediated, at least in part, through the inhibition of endothelial cell migration, as determined by the ability of TIMP to block chemotaxis in a Boyden chamber assay. These results indicate that the inhibition of migration is a direct effect on the endothelial cells and does not require accessory cells. An additional observation was that the RNA levels for TIMP were significantly reduced in differentiated adipocytes, compared to undifferentiated F442A controls. Therefore, the acquisition of an angiogenic phenotype may involve not only the induction of positive factors, but also the suppression of angiogenesis inhibitors.

Direct evidence linking expression of matrix metalloproteinase 9 (92-kDa gelatinase/collagenase) to the metastatic phenotype in transformed rat embryo cells

Members of the matrix metalloproteinase (MMP) family have been implicated in the metastasis of tumor cells, but no direct evidence linking any given member of the MMP family to metastatic behavior has been presented. Rat embryo cells transformed by the Ha-ras and v-myc oncogenes or by Ha-ras alone are metastatic in nude mice and release the 92-kDa gelatinase/collagenase (MMP-9), whereas those transformed by Ha-ras plus the adenovirus E1A gene are not metastatic and do not release MMP-9. Here we demonstrate that MMP-9 expression can be induced in these tumorigenic but nonmetastatic rat cells by transfection with an MMP-9 expression vector. Transfection of a MMP-9 expression vector, but not control DNAs, conferred metastatic capacity on the nonmetastatic cells. The majority of colonies isolated after continued passage either in vivo or in vitro had lost the MMP-9 expression vector. However, occasional cells were isolated from metastases which retained MMP-9 expression after passage. These cells retained metastatic capacity. In contrast, cells isolated after losing MMP-9 expression also lost the ability to metastasize. These results provide direct evidence that MMP-9 has a role in tumor metastasis.

Stimulation of TIMP-1 and metalloproteinase production in co-cultures of human tumor cells and human fibroblasts

The co-cultures of five different human tumor cell lines with human normal fibroblasts significantly stimulated the production of tissue inhibitors of metalloproteinases-1 (TIMP-1) when compared to cultures of individual cells. In the co-culture of T24 human urinary bladder carcinoma cells and CCD18 human fibroblasts, production of both TIMP-1 and metalloproteinases was stimulated, and the stimulatory effects were dependent on the cellular ratio between the fibroblasts and carcinoma cells. On day 6 of culture, collagenase and stromelysin were stimulated at a ratio of CCD18 fibroblasts to T24 cells of 1:0.1, while the maximum TIMP-1 production occurred at a ratio of 1:1. Thus, the cellular ratio in the interaction of carcinoma cells with host fibroblasts affects the production of TIMP-1 and metalloproteinases and hence modulates the balance between them.

Expression of type-IV collagenases in human tumor cell lines that can form liver colonies in chick embryos

Chick embryo has been used as a model system for evaluating the metastatic potential of tumor cells. We have previously demonstrated that expression of the tissue inhibitor of matrix metalloproteinase-I (TIMP-I) gene can suppress liver colonization of tumor cels in chick embryo, probably by inhibiting the activity of matrix metalloproteinases (MMP) produced by tumor cells. In an attempt to identify MMP associated with liver colonization, we examined 24 human tumor cell lines for their potential to form metastatic colonies in chick-embryo liver after the cells had been inoculated into the chorioallantoic membrane (CAM) vein. We compared the results with the mRNA expression of MMP (MMP-I, MMP-2, MMP-3, MMP-9) studied previously. Three of 8 cell lines from mesenchymal tumors (fibrosarcoma HT1080, osteosarcomas SK-ES and MNNG/HOS) and 2 of 16 cell lines from epithelial tumors (gastric carcinoma KKLS and bladder carcinoma T24) proliferated in the livers. MMP-2 and MMP-9 were the enzymes whose transcripts were more frequently expressed in these 5 metastatic cell lines (MMP-1; 2/5, MMP-2; 4/5, MMP-3; 0/5, MMP-9; 3/5), but other cell lines that did not form liver colonies expressed the transcripts at lower frequency (MMP-2; 7/19, MMP-9; 3/19). Although either or both MMP-2 and MMP-9 transcripts were expressed in 4 of the 5 metastatic cell lines, they were undetectable in T24 cells. However, induced expression of both enzymes was detected by immunostaining in the T24 cells colonized in the liver. Thus, type-IV collagenases expressed by tumor cells may play a role in facilitating colonization in chick embryos.

Branching N-linked oligosaccharides in breast cancer

Tumor progression in rodent and human tumors is commonly associated with changes in glycoprotein glycosylation, in particular increased beta 1-6GlcNAc-branching, a regulatory step in expression of polylactosamine and extended-chain Lewis antigens. Loss of the branched oligosaccharides in murine tumor cells either due to somatic mutation, or treatment of the cells with the oligosaccharide processing inhibitor swainsonine, blocks tumor cells invasion in vitro and reduces solid tumor growth in vivo. Swainsonine and other inhibitors of N-linked oligosaccharide processing may be useful anti-cancer drugs, a premise which has begun to be tested in humans.

Matrix degrading metalloproteinases

Matrix degrading metalloproteinases are enzymes that degrade proteins in tissue extracellular matrices. These proteinases exhibit specific, well defined properties that allow them to be classified into a family of enzymes. They are secreted by various cell types as the cells effect their surrounding extracellular matrix. Such effects occur during normal physiologic tissue remodeling but also during pathologic processes such as tumor cell invasion and metastases. Currently there are seven proteases classified as members of the matrix metalloproteinase family and there are two putative members. Direct correlations can be made between the matrix metalloproteinases and normal tissue functions such as bone remodeling, uterine and mammary gland function and ovulation. The matrix metalloproteinases are also strongly associated with cancer progression in that they function to degrade epithelial basement membrane and stromal matrices in many different malignancies including brain tumors.

Tumor invasion, proteolysis, and angiogenesis

In this review, some of the current literature on the regulation of proteolysis and angiogenesis during tumor invasion is discussed. Due to the critical location of brain tumors, an understanding of tumor cell interactions with the local environment is particularly relevant. Tissue breakdown during tumor invasion is associated with proteolytic activity, mediated by tumor cells, and surrounding host cells. This review covers two classes of proteinases and inhibitors that have commonly been associated with tumor invasion i.e., plasminogen activator (PA)/plasmin and matrix metalloproteinases (MMP) with special emphasis on the MMP inhibitors, TIMP-1 and TIMP-2. At different steps of the metastatic process, tumor cells interact with endothelial cells. Tumor cells also stimulate the formation of new vessels through the expression of specific angiogenic molecules. At least eight angiogenic molecules have been purified, sequenced and cloned, four of which are discussed here. Regulation of angiogenic activity has been the focus of intense studies recently, and a wide range of synthetic and natural angiogenesis inhibitors have been discovered. Targeting of angiogenic molecules and tumor vasculature may prove useful in future cancer therapeutic strategies.

The role of tissue inhibitor of metalloproteinase-1 in specific aspects of cancer progression and reproduction

Tissue inhibitors of metalloproteinases (TIMPs) are specific inhibitors of the multi member family of matrix metalloproteinases (MMPs). Since MMP function is fundamental to events that require tissue remodelling, TIMPs regulate normal biological processes by inhibiting MMPs, and are of importance in pathological conditions. In this chapter we review evidence for the suppressive role of TIMP-1 in the malignant progression of cancer and of its regulatory function in controlling invasion during blastocyst implantation and development.

Protease inhibitors: role and potential therapeutic use in human cancer

Proteases and protease inhibitors have been increasingly recognised as important factors in the physiopathology of human diseases, and our understanding of their role in cancer has dramatically increased over the last decade. We have obtained causal evidence linking proteases to tumour invasion and metastasis, and have become aware of genuine mechanisms used by tumour cells to optimise the use of proteases in the pericellular matrix. Many synthetic and natural inhibitors of these proteases have also been characterised, and their mechanisms of interaction with their corresponding enzymes are progressively unveiled as the X-ray crystal structures of these enzymes and their inhibitors are now reported. It has also become evident that many of these inhibitors, in addition to preventing the dissemination of cancer cells, have an inhibitory effect on tumour growth. Thus protease inhibitors are emerging as potentially therapeutic tools to treat cancer. In this article, recent studies on the role of proteases and their inhibitors in cancer are reviewed, and current ideas on their potential use as therapeutic agents are discussed.

Development of an in vitro extracellular matrix assay for studies of brain tumor cell invasion

Invasion of brain by tumor cells is an inherent feature of the malignant phenotype. Assays to quantitate invasiveness should provide a powerful tool to investigate this phenomenon. We have developed a modified in vitro assay to measure tumor cell invasion, attachment, and chemotaxis using a barrier of the complex basement membrane Matrigel on gelatin-coated filters. Within 5 hours, 7.8% of U251MGp and 2.6% of SF126 human malignant glioma cells invaded the Matrigel and filter, compared with 0.8% of normal human leptomeningeal cells. The extent of invasion was directly proportional to incubation time and filter pore size and inversely proportional to the Matrigel concentration. Cells from exponentially growing U251MGp cultures invaded more readily (10.9%) than cells from plateau-phase cultures (2.3%); however, labeling studies with bromodeoxyuridine showed that quiescent cells and rapidly dividing cells were equally capable of invading. This suggests that the mechanisms underlying invasion by malignant glioma cells are distinct from those underlying proliferation and indicates the need for therapy aimed specifically at invasive behavior. In a practical application of this assay to test a potential anti-invasive strategy, monoclonal antibodies to the beta subunit of an integrin receptor mediating attachment to the extracellular matrix inhibited invasion by U251MGp cells in a dose-dependent manner. This assay should allow evaluation of the cellular and molecular basis of brain tumor progression and perhaps aid the development of rationally designed drugs that limit tumor invasion. It may also allow prediction of the clinical behavior of neoplasms in individual patients.

Cytokine regulation of metalloproteinase gene expression

Matrix metalloproteinases belong to a family of zinc-dependent enzymes capable of degrading extracellular matrix and basement membrane components. Their expression is greatly modulated by cytokines and growth factors and involves the gene products of the Fos and Jun families of oncogenes. After extra(peri)cellular activation, their activity can be further controlled by specific tissue inhibitors of metalloproteinases. A correct balance between these regulatory mechanisms is necessary to ensure matrix remodeling in normal physiological processes such as embryonic development, but the overexpression of these enzymes may initiate or contribute to pathological situations such as cartilage degradation in rheumatoid arthritis or to tumor progression and metastasis. Delineation of the mechanisms of metalloproteinase and metalloproteinase inhibitors gene expression, understanding of their mode of interactions, and characterization of their patterns of expression in various tissues in normal and pathological states will lead to new therapeutic strategies to counteract the deleterious effects of matrix metalloproteinases in human disease.

Localization by in situ hybridization of mRNAs encoding stromelysin 3 and tissue inhibitors of metallo-proteinases TIMP-1 and TIMP-2 in human head and neck carcinomas

The presence and distribution of mRNAs encoding a matrix metalloproteinase (MMP) stromelysin 3 and two tissue inhibitors of MMP, TIMP1 and TIMP-2 have been studied by in situ hybridization of 18 human epidermoid head and neck carcinomas and four normal tissues. We found that in 16 tumors out of 18, stromelysin 3 mRNAs were only expressed by fibroblasts which were in close contact to invasive cancer cells. Tumor cells and normal tissues were not labeled. TIMP-1 mRNAs were detected in well differentiated cancer cells and in endothelial cells in all the cancers. In 13 out of the 18 carcinomas, TIMP-2 mRNAs were localized in only a few stromal cells near well differentiated invasive cancer cells and in endothelial cells. The significant expression of TIMP-1 and TIMP-2 mRNAS may lead to less aggressive MMPs, especially in the case of stromelysin 3, in the invasive process of the stroma.

Tissue inhibitor of metalloproteinases-2 inhibits bFGF-induced human microvascular endothelial cell proliferation

Tissue inhibitor of metalloproteinase-2 (TIMP-2), a protease inhibitor that binds to the latent and active forms of 72 kDa type IV collagenase (gelatinase A), was found to inhibit the in vitro proliferation of human microvascular endothelial (HME) cells stimulated with bFGF and 5% serum. The maximal inhibitory effect of TIMP-2 on incorporation of 3H-thymidine was evident 24 hours after bFGF stimulation of these cells and ranged between 45 and 60%. The half-maximal effective concentration of TIMP-2 was 107 +/- 12 nM (S.D.). In contrast, TIMP-1 was not found to slow the growth of HME cells. The inhibition of cell proliferation observed with TIMP-2 was not mimicked by addition to the culture medium of BB94, a general matrix metalloproteinase inhibitor, nor antibodies to the 72 kDa type IV collagenase. In addition to growth, two other cell functions associated with the angiogenic process were tested for sensitivity to TIMP-2. Cell adhesion to tissue culture plastic was slightly stimulated by TIMP-2, and cell migration was inhibited with short-term exposure to TIMP-2, but neither process was affected by longer-term exposure. The ability of TIMP-2 to inhibit cultured endothelial cell proliferation independent of protease inhibitory activity suggests that TIMP-2 may have additional actions which may limit neovascularization associated with solid tumor growth and metastasis in vivo.

Molecular and cellular analysis of basement membrane invasion by human breast cancer cells in Matrigel-based in vitro assays

In vitro analyses of basement membrane invasiveness employing Matrigel (a murine tumor extract rich in basement membrane components) have been performed on human breast cancer model systems. Constitutive invasiveness of different human breast cancer (HBC) cell lines has been examined as well as regulation by steroid hormones, growth factors, and oncogenes. Carcinoma cells exhibiting a mesenchymal-like phenotype (vimentin expression, lack of cell border associated uvomorulin) show dramatically increased motility, invasiveness, and metastatic potential in nude mice. These findings support the hypothesis that epithelial to mesenchymal transition (EMT)-like events may be instrumental in the metastatic progression of human breast cancer. The MCF-7 subline MCF-7ADR appears to have undergone such a transition. The importance of such a transition may be reflected in the emergence of vimentin expression as an indicator of poor prognosis in HBC. Matrix degradation and laminin recognition are highlighted as potential targets for antimetastatic therapy, and analyses of laminin attachment and the matrix metalloproteinase (MMP) family in HBC cell lines are summarized. Matrigel-based assays have proved useful in the study of the molecular mechanisms of basement membrane invasiveness, their regulation in HBC cells, and their potential as targets for antimetastatic therapy.

Brainstem and other malignant gliomas: II. Possible mechanisms of brain infiltration by tumor cells

Gliomas that arise in the brain stem and other malignant gliomas constitute approximately 60% of all brain tumors and have eluded effective therapy, in part because they are able to infiltrate the normal brain. Histopathologic studies have confirmed the presence of infiltrating tumor cells very distant from the glioma mass. We review the neuroimaging and pathologic features of glioma-cell infiltration and some of the complex cellular and biochemical determinants of tumor-cell motility and invasiveness. Understanding how glioma cells become motile and invasive is pivotal to therapeutically targeting the machinery that enables gliomas to infiltrate the brain.

Tissue inhibitor of metalloproteinases (TIMP, aka EPA): structure, control of expression and biological functions

The TIMPs play an important role in regulating the activity of the secreted metalloproteinases (collagenases, stromelysins, gelatinases). Two different TIMPS have been well characterized, each capable of inhibiting all tested eukaryotic metalloproteinases but showing specific binding to a particular gelatinase at a site distinct from the active site. They influence the activation of the prometalloproteinase and act to modulate proteolysis of extracellular matrix, notably during tissue remodeling and inflammatory processes. On certain cell types, they can exhibit growth factor-like activity, and they can inhibit the tumorigenic and metastatic phenotype of cancer cells.

Expression of a potential metastasis suppressor gene (nm23) in thyroid neoplasms

Identification of multiple clinical and pathologic prognostic factors in differentiated thyroid cancer has permitted some degree of risk stratification. However, these clinical indices fail to distinguish potential intrinsic differences in tumor virulence. The nm23 gene has been identified as a potential metastasis suppressor gene that is homologous to nucleoside diphosphate kinases. Studies in human breast cancer have shown a significant inverse correlation between nm23 levels and nodal involvement/tumor recurrence. Given the possible clinical utility of a marker of metastatic potential in the management of thyroid carcinoma, we examined 34 thyroid neoplasms and a human medullary thyroid cancer (MTC) cell line (TT) for nm23 expression. Normalized nm23 expression was assessed by Northern analysis of tumor RNA. nm23 Expression (tumor expression/TT cell expression, mean +/- SE) was 1.14 +/- 0.15* in MTCs (n = 5), 0.70 +/- 0.10* in follicular cancers (n = 6), 0.51 +/- 0.11 in papillary cancers (n = 19), and 0.31 +/- 0.03 in follicular adenomas (n = 4) (*p < 0.05 when compared to adenomas). Within histologic groups, we found no correlation between nm23 expression and nodal involvement of distant metastases. Our results indicate that thyroid neoplasms of different histologies express varying levels of the nm23 transcript. Although nm23 expression seems diminished in metastatic breast cancer, it appears not to be the case in metastatic thyroid cancer. The nm23 gene may therefore have different roles in the evolution and metastases of different neoplasms.

Role and regulation of expression of 92-kDa type-IV collagenase (MMP-9) in 2 invasive squamous-cell-carcinoma cell lines of the oral cavity

The present study was undertaken to determine the role of the metalloproteinase MMP-9 in the invasive phenotype of squamous-cell carcinoma of the oral cavity and the regulation of its expression. Zymographic analysis of conditioned medium from 2 highly invasive squamous-cell-carcinoma cell lines indicated large amounts of an enzyme which was indistinguishable, in size (92 kDa) from the MMP-9 pro-enzyme. Conversion of the 92-kDa gelatinase into a lower-molecular-weight species (84 kDa), identical in size to the activated gelatinase, was evident when both cell lines, which are avid secretors of urokinase, were cultured in the presence of plasminogen. Penetration of an extracellular-matrix-coated filter was dramatically reduced in the presence of the collagenase inhibitor, tissue inhibitor of metalloproteinase-2, suggesting a critical role for MMP-9 in the invasive process. Immunohistochemical studies demonstrating the presence of MMP-9 in tumor cells of resected squamous-cell cancers suggested that secretion of this collagenase by cells in vitro was reflective of the in vivo setting. Since several phorbol-ester response elements are present in the MMP-9 promoter, we determined the role of protein-kinase-C pathways in the regulation of MMP-9 expression in cultured SCC. Treatment of cells with PMA resulted in a more-than-20-fold increase in the level of protein and mRNA. Conversely, culturing of cells in the presence of the protein-kinase-C inhibitor, calphostin-C, led to a dose-dependent decrease in the amount of MMP-9 mRNA and protein, suggesting that the constitutive expression of this collagenase reflects activation of this signal transduction pathway. In summary, our data suggest that, for a sub-population of squamous-cell carcinomas, secreted MMP-9 is an important determinant of the invasive phenotype, and that the expression of this metalloproteinase is regulated by protein-kinase-C pathways.

Antisense profilaggrin RNA delays and decreases profilaggrin expression and alters in vitro differentiation of rat epidermal keratinocytes

Ichthyosis vulgaris is an epidermal disorder in which profilaggrin expression is decreased or absent. To determine whether the ichthyosis vulgaris phenotype could be mimicked by eliminating profilaggrin expression, a rat epidermal cell line was transfected with a plasmid that directs the constitutive expression of an RNA that is antisense to normal profilaggrin mRNA. Non-transfected and neomycin-resistant cells not containing antisense plasmid that were grown in the neomycin analogue G418 served as controls. Immunoblot and immunofluorescence analysis showed that profilaggrin protein expression and processing to filaggrin were delayed by 3 to 4 d and decreased in transfected cells. Profilaggrin mRNA was detected in both control and transfected cells only after the cells reached confluence, whereas antisense RNA was detected in transfectants at all times, even prior to confluence. Ultrastructural examination revealed that keratohyalin granules were decreased in number, globular, and heterogeneous in appearance in transfected cells in-contrast to angular structures seen in control cells. Unexpectedly, stratification was impaired, intermediate filaments were noticeably reduced, and cornified cell envelope formation was delayed in transfectants. Unlike ichthyosis vulgaris keratinocytes, where keratin expression is unaffected, appearance of K1 and K10 was delayed and K1/K10 synthesis was delayed and decreased in transfected cells. The precipitous drop in 35S-methionine incorporation into cytoskeletal protein seen at confluence in control cells was delayed by 3 d in transfected cells. We conclude that, rather than producing the ichthyosis vulgaris phenotype, antisense profilaggrin RNA has more broad-reaching effects on in vitro differentiation of rat epidermal keratinocytes.

Adhesion molecules and their role in cancer metastasis

This article describes various adhesion molecules and reviews evidence to support a mechanistic role for adhesion molecules in the process of cancer metastasis. A variety of evidence supports the involvement of specific adhesion molecules in metastasis. 1. For example, some cancer cells metastasize to specific organs, irrespective of the first organ encountered by the circulating cancer cells. This ability to colonize a specific organ has been correlated with the preferential adhesion of the cancer cells to endothelial cells derived from the target organ. This suggests that cancer cell/endothelial cell adhesion is involved in cancer cell metastasis and that adhesion molecules are expressed on the endothelium in an organ-specific manner. 2. Further, inclusion of peptides that inhibit cell adhesion, such as the YIGSR- or RGD-containing peptides, is capable of inhibiting experimental metastasis. 3. Metastasis can be enhanced by acute or chronic inflammation of target vessels, or by treatment of animals with inflammatory cytokines, such as interleukin-1. In vitro, cancer cell/endothelial cell adhesion can be enhanced by pretreating the endothelial cell monolayer with cytokines, such as interleukin-1 or tumor necrosis factor-alpha. This suggests that, in addition to organ-specific adhesion molecules, a population of inducible endothelial adhesion molecules is involved and is relevant to metastasis. 4. Further support for this model is found in the comparison to leukocyte/endothelial adhesion during leukocyte trafficking. Convincing evidence exists, both in vivo and in vitro, to demonstrate an absolute requirement for leukocyte/endothelial adhesion before leukocyte extravasation can occur. The relevance of this comparison to metastasis is reinforced by the observation that some of the adhesion molecules involved in leukocyte/endothelial adhesion are also implicated in cancer cell/endothelial adhesion. The involvement of adhesion molecules suggests a potential therapy for metastasis based on interrupting adhesive interactions that would augment other treatments for primary tumors.

Temporal expression of tissue inhibitors of metalloproteinases in mouse reproductive tissues during gestation

Tissue inhibitors of metalloproteinases (TIMPs) appear to play an important regulatory role in tissue remodelling and invasion by malignant cells. Since pregnancy involves morphological changes in existing maternal tissues, as well as a strictly controlled invasion by fetal trophoblasts, we have examined the temporal expression of TIMP-1, TIMP-2, and specific metalloproteinases in the mouse uterus, decidua, placenta, amnion, and ovaries throughout gestation by examining mRNA levels on northern and slot blots. Maximal levels of TIMP-1 mRNA were observed from day 6 to day 10 in the uterus, decidua, and placenta. In clear contrast to the early burst of TIMP-1 mRNA accumulation, the level of TIMP-2 mRNA increased steadily throughout gestation in the uterus, decidua, and amnion, while in the placenta it showed a sevenfold increase after day 14. In amnion, TIMP-1 was induced specifically on day 18. Interestingly, the normally high level of TIMP-1 mRNA seen in the ovaries of virgin mice was low during gestation, until day 18 and postpartum, when a sixfold increase over the levels in virgin ovary was observed. In contrast, ovarian TIMP-2 mRNA showed a marginal increase during gestation. The temporal pattern of 72 kDa gelatinase type A followed that of TIMP-2 in the decidua and ovary. Stromelysin-2 mRNA was detected at term only in ovary and decidua. Our data show that the temporal accumulation of TIMP-1 and TIMP-2 mRNA is precisely coordinated in each of the tissue compartments and is independently regulated during the in vivo remodeling of reproductive tissues in gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of plasminogen activators, metalloproteinases and the tissue inhibitor of metalloproteinase-1 in the metastatic process of human salivary-gland adenocarcinoma cells

An in vitro system has been established in which conversion from non-metastasizing to metastasizing adenocarcinoma cells can be induced, and subsequently subjected to analysis of the expression of proteases and tissue inhibitor of metalloproteinases-1 (TIMP-1). A human salivary-gland adenocarcinoma cell clone HSGc, with no metastatic ability, was exposed to N-methyl-N-nitrosourea (MNU). Following exposure to MNU, cells with altered morphology were cloned. Upon s.c. inoculation into nude mice, MNU-treated HSGc clones formed metastatic foci in various organs, and then 5 metastasizing clones were isolated. Evaluation of expression of tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), metalloproteinases and TIMP-1 was performed by means of enzyme immunoassay, zymogram, or immunoblot. MNU-treated HSGc and metastasizing clones were found to secrete high levels of tPA, while HSGc produced undetectable levels of this enzyme. Expression of uPA was not observed in any of the cell clones. When the secretion of gelatinolytic enzymes was examined, metastasizing clones produced higher levels of 57- and 32-kDa, but not of 92- or 72-kDa gelatinases, as compared to HSGc cells. Although TIMP-1 was detected in all cell clones, metastasizing clones secreted less TIMP-1 than HSGc cells; in addition, one metastasizing clone produced TIMP-1 with a molecular weight distinct from that of 28-kDa TIMP-1. Our results suggest that the acquisition of metastatic ability by human salivary-gland tumor cells is closely associated with increased secretion of several metalloproteinases as well as decreased or altered TIMP-1 expression.

Inhibition of N-linked oligosaccharide processing in tumor cells is associated with enhanced tissue inhibitor of metalloproteinases (TIMP) gene expression

Previous studies on tumor-cell glycosylation mutants and drugs which inhibit oligosaccharide processing suggest that expression of sialylated and highly branched complex-type N-linked oligosaccharides is required for efficient tumor-cell metastasis. These observations prompted the present investigation, in order to determine whether loss of sialylated and highly branched complex-type oligosaccharide in cellular glycoproteins might affect the expression of genes, particularly of genes which can influence the malignant phenotypes. Swainsonine, an inhibitor of Golgi alpha-mannosidase II, has previously been shown to inhibit invasion in vitro and reduces solid tumor in vivo. Metastatic sub-lines of the SP1 murine mammary carcinoma cells cultured in the presence of swainsonine for 48 hr showed approximately 3-fold enhancement of TIMP mRNA levels, while urokinase (uPA) transcripts remained unchanged. To determine whether swainsonine's effect on TIMP mRNA levels was related to inhibition of oligosaccharide processing, we examined somatic glycosylation mutants with processing defects which attenuate metastatic potential. The Golgi UDP-Gal transport defect in murine MDAY-D2 lymphoma cells, Chinese hamster ovary cells (CHO) and human MeWo melanoma cells (i.e., D35W25, Lec8, 3S5 cell lines, respectively) was associated with increased TIMP mRNA levels. A revertant of Lec8 showed a return to the wild-type levels of TIMP mRNA, consistent with a causal relationship between the glycosylation mutation and TIMP gene expression. Similarly, CHO and MDAY-D2 mutants defective in GlcNAc-TV (i.e., Lec4 and KBL-1 respectively), which also reduces metastatic potential, showed increases in TIMP transcript levels. Nuclear run-on assays showed that transcription of the TIMP gene was increased in cells where N-linked oligosaccharide processing was inhibited either by swainsonine or by a glycosylation mutation. The results suggest that cell-specific patterns of glycoprotein glycosylation in human, murine and hamster cell lines affects the transcription of select genes, including TIMP, which may influence the invasive phenotype.

Effects of thiol protease inhibitors on cell cycle and proliferation of vascular smooth muscle cells in culture

Smooth muscle proliferation is a prominent feature of the vascular response to mechanical injury. Accordingly, modulation of proliferation has important therapeutic implications for angioplasty restenosis. We have identified a subclass of thiol protease inhibitors (TPIs) that reversibly inhibit bovine aortic smooth muscle cell (BASMC) proliferation in vitro. To define the nature of this inhibition, an evaluation of selected steps in the cell cycle was undertaken. Treatment of BASMCs with benzyloxycarbonyl-Leu-norleucinal (calpeptin) at 100 microM and acetyl-Leu-Leu-norleucinal (TPI-1) at 50 microM was shown to cause a block of platelet-derived growth factor-BB as well as serum-inducible cell cycle progression at a point before the G1-S boundary, reducing the percentage of bromodeoxyuridine-positive cells from 87% to 5% over a 24-hour labeling period. Addition of TPI-1 at various times after serum addition to serum-deprived BASMCs showed 80% of the maximal block of DNA synthesis even when added 6 hours after serum. The cell cycle progression block was gradually lost as the delay from serum to TPI-1 application was increased from 6 to 12 hours. By Northern analysis of mRNA after serum addition, TPI-1 caused a fourfold decrease in the transient elevation of fos and myc proto-oncogene as well as a decrease in the levels of both muscle and nonmuscle actin mRNA induced early after serum addition. Flow cytometric analysis of DNA content and synthesis in BASMCs treated with TPI-1 or calpeptin additionally revealed the presence of a distinct cell cycle block in the G2-M compartment. In the aggregate, these results suggest the existence of more than one molecular site potentially involved in inhibition by TPI of cell cycling in BASMCs.

Expression of human recombinant 72 kDa gelatinase and tissue inhibitor of metalloproteinase-2 (TIMP-2): characterization of complex and free enzyme

The human 72 kDa gelatinase/type IV collagenase is a metalloproteinase that is thought to play a role in metastasis and angiogenesis. The 72 kDa progelatinase can be isolated from conditioned media as a complex with the tissue inhibitor of metalloproteinase-2 (TIMP-2). To investigate 72 kDa gelatinase-TIMP-2 interactions and to compare the activity of the complex versus that of the free enzyme, we have expressed and purified human 72 kDa progelatinase and TIMP-2 as single proteins in a recombinant vaccinia virus mammalian cell expression system. The recombinant 72 kDa progelatinase was able to bind TIMP-2, and it digested gelatin and collagen type IV after activation by p-aminophenylmercuric acid (APMA). The specific activity of the recombinant free enzyme was 20-fold higher than the activity of an APMA-treated stoichiometric complex of recombinant 72 kDa progelatinase and TIMP-2. Also, TIMP-2 caused an 86% inhibition of activity when added to the activated enzyme at a 1:1 molar ratio. Activation of the free recombinant 72 kDa progelatinase yielded the 62 kDa species and two fragments of 46 and 35 kDa that cross-reacted with monoclonal antibodies to the 72 kDa proenzyme. TIMP-2 inhibited the conversion of the recombinant proenzyme to the 62 kDa species and the appearance of the 45 and 35 kDa bands. These results suggest that TIMP-2 is not only a potent inhibitor of the activated enzyme but also prevents the generation of low-molecular-mass species and full enzymic activity from the zymogen.

Resolution of TIMP-free and TIMP-complexed 70kDa progelatinase from culture medium of Rous sarcoma virus-transformed chicken embryo fibroblasts

Chicken embryo fibroblasts (CEF) produce a 70kDa progelatinase, a member of the matrix metalloproteinase family, and secrete elevated levels of the enzyme upon transformation by Rous sarcoma virus (RSV). This enzyme can be purified by affinity chromatography complexed with a 21kDa tissue inhibitor of metalloproteinases (TIMP)-like molecule. Gel-filtration of the purified progelatinase suggests the presence of a mixed population of enzyme: a TIMP-complexed and a TIMP-free progelatinase. These two species were separated by Mono Q FPLC in the absence of denaturants. Quantitation of the purified progelatinase reveals that the transformed RSVCEF produce more TIMP-free enzyme than the normal CEF. Native PAGE analysis indicates that purified TIMP-free progelatinase is capable of binding to TIMP and generating a TIMP-complexed progelatinase. Treatment of the TIMP-free gelatinase with organomercurials results in a rapid conversion to the active 62kDa species and indicates that the TIMP-free progelatinase is more susceptible to activation than the TIMP-complexed progelatinase.

Matrix metalloproteinases: a review

Matrix metalloproteinases (MMPs) are a family of nine or more highly homologous Zn(++)-endopeptidases that collectively cleave most if not all of the constituents of the extracellular matrix. The present review discusses in detail the primary structures and the overlapping yet distinct substrate specificities of MMPs as well as the mode of activation of the unique MMP precursors. The regulation of MMP activity at the transcriptional level and at the extracellular level (precursor activation, inhibition of activated, mature enzymes) is also discussed. A final segment of the review details the current knowledge of the involvement of MMP in specific developmental or pathological conditions, including human periodontal diseases.

Role of matrix metalloproteinases in invasion and metastasis: biology, diagnosis and inhibitors

The processes of tumour invasion and subsequent metastasis are the most lethal aspects of cancer. Whilst many factors are involved, the matrix metalloproteinases (MMPs) have been implicated as key-rate limiting enzymes in the invasive process. This family consisting of eight members of similar structure, can be roughly divided into three groups based on substrate specificity. All are secreted in a latent form and require proteolytic cleavage for activation. The expression of these enzymes is regulated at the transcriptional level by a variety of growth factors and oncogenes. They are also regulated at the protein level by a family of specific inhibitors called the tissue inhibitors of metalloproteinases (TIMPs). Studies in human tumour samples have shown a positive correlation between metalloproteinase expression and metastatic potential. The levels of metalloproteinase expression have been manipulated using molecular biology techniques in several cell lines and shown a similar correlation. These results suggest that an understanding of metalloproteinase expression and proteolytic activity may lead to the development of effective therapeutic agents with the potential to reduce the incidence of metastatic cancer.

Antisense suppression of transferrin receptor gene expression in a human hepatoma cell (HuH-7) line

A recombinant plasmid carrying human transferrin receptor cDNA in reverse orientation downstream from the human cytomegalovirus immediate early promoter/enhancer element was introduced into the HuH-7 human hepatoma cell line by lipofection. Cell surface transferrin binding and iron uptake from transferrin each decreased by about 50% in stable transfectants bearing integrated antisense DNA expression vector. Northern blot analysis indicated that the abundance of target transferrin receptor message was not altered by antisense RNA. These results suggest that the antisense transcript interferes with expression of the endogenous transferrin receptor gene at the level of translation.

Involvement of AP1 and PEA3 binding sites in the regulation of murine tissue inhibitor of metalloproteinases-1 (TIMP-1) transcription

Transcription of tissue inhibitor of metalloproteinases-1 (TIMP-1), a secreted protein that regulates the activities of the metalloproteinases, collagenase and stromelysin, is activated by serum growth factors. Transient transfection experiments have revealed several regions of cis-acting regulatory sequences involved in the response of the murine TIMP-1 gene to serum. One area is in the vicinity of the promoter, consisting of a non-consensus binding site (5'-TGAGTAA-3' at -59/-53) for transcription factor AP1 and an adjacent 24 bp region of dyad symmetry that contains a PEA3-binding site. A second is an upstream region (-1020 to -780) that acts as an enhancer when linked to a heterologous promoter, and contains a consensus AP1 binding site (at -803/ -797). Gel retardation assays revealed differences between nuclear factors in mouse C3H10T1/2 cells that bound to the TIMP(-59/ -53)AP1 site and a consensus collagenase TRE (TPA-response element). The TIMP(-59/ -53)AP1 site is a promiscuous motif that binds c-Fos/c-Jun AP1 translated in vitro and is an effective competitor for binding of nuclear AP1 factors to the consensus TRE, but in addition it binds factors that do not associate with the consensus TRE. The TIMP(-59/ -53)AP1 motif and the dyad symmetry region stimulated expression from a thymidine kinase promoter in an additive fashion, and competition experiments showed that excess copies of these factor binding sites reduced expression from a reporter plasmid driven by the TIMP-1 promoter. Our data show that binding sites for AP1 and PEA3 transcription factors are involved in the regulation of TIMP-1 transcription, which suggests that the coordinated induction of TIMP-1, collagenase and stromelysin may be achieved through the actions of a shared set of nuclear transcription factors. However, the properties of the TIMP-1(-59/ -53)AP1 motif likely reflect an additional type of transcriptional regulation restricted to TIMP-1.