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Biomedical subjects

Z Werb

Publications and source records attributed to Z Werb.

At least 19 recordsLinked to original sources
PubMed2000

The matrix metalloproteinase stromelysin-1 acts as a natural mammary tumor promoter.

Extracellular matrix-degrading matrix metalloproteinases (MMPs) are invariably upregulated in epithelial cancers and are key agonists in angiogenesis, invasion and metastasis. Yet most MMPs are secreted not by the cancer cells themselves, but by stromal cells within and around the tumor mass. Because the stromal environment can influence tumor formation, and because MMPs can alter this environment, MMPs may also contribute to the initial stages of cancer development. Several recent studies in MMP-overexpressing and MMP-deficient mice support this possibility, but have required carcinogens or pre-existing oncogenic mutations to initiate tumorigenesis. Here we review the spontaneous development of premalignant and malignant lesions in the mammary glands of transgenic mice that express an autoactivating form of MMP-3/stromelysin-1 under the control of the whey acidic protein gene promoter. These changes were absent in nontransgenic littermates and were quenched by co-expression of a human tissue inhibitor of metalloproteinases-1 (TIMP-1) transgene. Thus by altering the cellular microenvironment, stromelysin-1 can act as a natural tumor promoter and enhance cancer susceptibility.

Animals↗
PubMed2000

Proteinases in bone resorption: obvious and less obvious roles.

Bone resorption is critical for the development and the maintenance of the skeleton, and improper regulation of bone resorption leads to pathological situations. Proteinases are necessary for this process. In this review, we show that this need of proteinases is not only because they are required for the solubilization of bone matrix, but also because they are key components of the mechanism that determines where and when bone resorption will be initiated. Moreover, there are indications that proteinases may also determine whether resorption will be followed by bone formation. Some of the proteinases involved in these different steps of the resorption processes were recently identified, as for instance cathepsin K, MMP-9 (gelatinase B), and interstitial collagenase. However, there is also increasing evidence showing that the critical proteinase(s) may vary depending on the bone type or on other factors.

Bone Diseases↗
PubMed2000

Nidogen-1 regulates laminin-1-dependent mammary-specific gene expression.

Nidogen-1 (entactin) acts as a bridge between the extracellular matrix molecules laminin-1 and type IV collagen, and thus participates in the assembly of basement membranes. To investigate the role of nidogen-1 in regulating cell-type-specific gene expression in mammary epithelium, we designed a culture microecosystem in which each component, including epithelial cells, mesenchymal cells, lactogenic hormones and extracellular matrix, could be controlled. We found that primary and established mesenchymal and myoepithelial cells synthesized and secreted nidogen-1, whereas expression was absent in primary and established epithelial cells. In an epithelial cell line containing mesenchymal cells, nidogen-1 was produced by the mesenchymal cells but deposited between the epithelial cells. In this mixed culture, mammary epithelial cells express (beta)-casein in the presence of lactogenic hormones. Addition of either laminin-1 plus nidogen-1, or laminin-1 alone, to mammary epithelial cells induced (beta)-casein production. We asked whether recombinant nidogen-1 alone could signal directly for (beta)-casein. Nidogen-1 did not induce (beta)-casein synthesis in epithelial cells, but it augmented the inductive capacity of laminin-1. These data suggest that nidogen-1 can cooperate with laminin-1 to regulate (beta)-casein expression. Addition of full-length nidogen-1 to the mixed cultures had no effect on (beta)-casein gene expression; however, a nidogen-1 fragment containing the laminin-1 binding domain, but lacking the type IV collagen-binding domain, had a dominant negative effect on (beta)-casein expression. These data point to a physiological role for nidogen-1 in the basement membrane-induced gene expression by epithelial cells.

Animals↗
PubMed1999

Matrix metalloproteinase-9/gelatinase B is required for process outgrowth by oligodendrocytes.

Oligodendrocytes (OLs) extend processes to contact axons as a prerequisite step in myelin formation. As the OL processes migrate toward their axonal targets, they modify adhesion to their substrate, an event that may be regulated by matrix metalloproteinases (MMPs). In the mouse optic nerve, MMP-9/gelatinase B increases during myelin formation. Although tissue inhibitor of metalloproteinase (TIMP)-3 also increases in parallel, the developing optic nerve has focally active MMPs demonstrable by in situ zymography. The distribution of proteolytic activity is similar to that of myelin basic protein, a marker of myelin formation. OLs in culture secrete MMP-9 and express active cell-associated metalloproteinases at the growing tips of their processes. TIMP-1 and a function-perturbing anti-MMP-9 antibody attenuate outgrowth of processes by OLs, indicating a requirement for MMP-9 in process outgrowth. Process reformation is retarded significantly in OLs cultured from MMP-9 null mice, as compared with controls, providing genetic evidence that MMP-9 is necessary for process outgrowth. These data show that MMP-9 facilitates process outgrowth by OLs in vivo and in culture.

Adult↗
PubMed1999

The stromal proteinase MMP3/stromelysin-1 promotes mammary carcinogenesis.

Matrix metalloproteinases (MMPs) are invariably upregulated in the stromal compartment of epithelial cancers and appear to promote invasion and metastasis. Here we report that phenotypically normal mammary epithelial cells with tetracycline-regulated expression of MMP3/stromelysin-1 (Str1) form epithelial glandular structures in vivo without Str1 but form invasive mesenchymal-like tumors with Str1. Once initiated, the tumors become independent of continued Str1 expression. Str1 also promotes spontaneous premalignant changes and malignant conversion in mammary glands of transgenic mice. These changes are blocked by coexpression of a TIMP1 transgene. The premalignant and malignant lesions have stereotyped genomic changes unlike those seen in other murine mammary cancer models. These data indicate that Str1 influences tumor initiation and alters neoplastic risk.

Animals↗
PubMed1999

Inflammatory mast cells up-regulate angiogenesis during squamous epithelial carcinogenesis.

Expression of HPV16 early region genes in basal keratinocytes of transgenic mice elicits a multistage pathway to squamous carcinoma. We report that infiltration by mast cells and activation of the matrix metalloproteinase MMP-9/gelatinase B coincides with the angiogenic switch in premalignant lesions. Mast cells infiltrate hyperplasias, dysplasias, and invasive fronts of carcinomas, but not the core of solid tumors, where they degranulate in close apposition to capillaries and epithelial basement membranes, releasing mast-cell-specific serine proteases MCP-4 (chymase) and MCP-6 (tryptase). MCP-6 is shown to be a mitogen for dermal fibroblasts that proliferate in the reactive stroma, whereas MCP-4 can activate progelatinase B and induce hyperplastic skin to become angiogenic in an in vitro bioassay. Notably, premalignant angiogenesis is abated in a mast-cell-deficient (KITW/KITWWv) HPV16 transgenic mouse. The data indicate that neoplastic progression in this model involves exploitation of an inflammatory response to tissue abnormality. Thus, regulation of angiogenesis during squamous carcinogenesis is biphasic: In hyperplasias, dysplasias, and invading cancer fronts, inflammatory mast cells are conscripted to reorganize stromal architecture and hyperactivate angiogenesis; within the cancer core, upregulation of angiogenesis factors in tumor cells apparently renders them self-sufficient at sustaining neovascularization.

Animals↗
PubMed1999

Transcriptional regulation of stromelysin-1 gene expression is altered during progression of mouse mammary epithelial cells from functionally normal to malignant.

The matrix metalloproteinase stromelysin-1 plays a central role during mammary gland development and tumor progression. To gain insight into the regulation of stromelysin-1 gene expression, the murine stromelysin-1 promoter was cloned and transfected into mouse mammary epithelial cells displaying various degrees of malignancy. A reconstituted basement membrane inhibited stromelysin-1 promoter activity in functionally normal cells, had little effect on moderately malignant cells and up-regulated the promoter in highly malignant cells. Spreading of normal and malignant cells was reduced by a reconstituted basement membrane, compared to a plastic substratum. Preventing spreading by maintenance of cells in suspension culture, regulated stromelysin-1 promoter activity in a manner similar to that on a reconstituted basement membrane. Conversely, increasing spreading by augmenting substratum adhesivity up-regulated stromelysin-1 promoter activity in tumor cells. In cells with reduced spreading in the presence of reconstituted basement membrane and in suspension culture, actin stress fibers were replaced by cortical actin bundles. In tumor cells, but not in functionally normal cells, treatment with phorbol diesters also resulted in accumulation of cortical actin and increased stromelysin-1 promoter activity. Consistent with an epithelial-to-mesenchymal conversion, regulation of stromelysin-1 gene expression in highly malignant cells was similar to its regulation in mammary fibroblasts. We conclude that the switch in transcriptional regulation of stromelysin-1 expression that occurs during epithelial-to-mesenchymal transition and conversion to tumorigenicity is related to altered regulation of signals from the cytoarchitecture.

Actins↗
PubMed1999

Epidermal growth factor receptor function is necessary for normal craniofacial development and palate closure.

Craniofacial malformations are among the most frequent congenital birth defects in humans; cleft palate, that is inadequate fusion of the palatal shelves, occurs with an annual incidence of 1 in 700 to 1 in 1,000 live births among individuals of European descent. The secondary palate arises as bilateral outgrowths from the maxillary processes, and its formation depends on the coordinated development of craniofacial structures including the Meckel's cartilage and the mandible. Cleft lip and palate syndromes in humans are associated with polymorphisms in the gene (TGFA) encoding transforming growth factor-alpha (TGF-alpha), an epidermal growth factor receptor (EGFR) ligand made by most epithelia. Here we have characterized craniofacial development in Egfr-deficient (Egfr-/-) mice. Newborn Egfr-/- mice have facial mediolateral defects including narrow, elongated snouts, underdeveloped lower jaw and a high incidence of cleft palate. Palatal shelf explants from Egfr-/- mice fused, but frequently had residual epithelium in the midline. In addition, morphogenesis of Meckel's cartilage was deficient in cultured mandibular processes from Egfr-/- embryos. The secretion of matrix metalloproteinases (MMPs) was diminished in Egfr-/- explants, consistent with the ability of EGF to increase MMP secretion and with the decreased MMP expression caused by inhibition of Egfr signalling in wild-type explants. Accordingly, inactivation of MMPs in wild-type explants phenocopied the defective morphology of Meckel's cartilage seen in Egfr-/- explants. Our results indicate that EGFR signalling is necessary for normal craniofacial development and that its role is mediated in part by its downstream targets, the MMPs, and may explain the genetic correlation of human cleft palate with polymorphisms in TGFA.

Animals↗
PubMed1999

VEGF couples hypertrophic cartilage remodeling, ossification and angiogenesis during endochondral bone formation.

Hypertrophic chondrocytes in the epiphyseal growth plate express the angiogenic protein vascular endothelial growth factor (VEGF). To determine the role of VEGF in endochondral bone formation, we inactivated this factor through the systemic administration of a soluble receptor chimeric protein (Flt-(1-3)-IgG) to 24-day-old mice. Blood vessel invasion was almost completely suppressed, concomitant with impaired trabecular bone formation and expansion of hypertrophic chondrocyte zone. Recruitment and/or differentiation of chondroclasts, which express gelatinase B/matrix metalloproteinase-9, and resorption of terminal chondrocytes decreased. Although proliferation, differentiation and maturation of chondrocytes were apparently normal, resorption was inhibited. Cessation of the anti-VEGF treatment was followed by capillary invasion, restoration of bone growth, resorption of the hypertrophic cartilage and normalization of the growth plate architecture. These findings indicate that VEGF-mediated capillary invasion is an essential signal that regulates growth plate morphogenesis and triggers cartilage remodeling. Thus, VEGF is an essential coordinator of chondrocyte death, chondroclast function, extracellular matrix remodeling, angiogenesis and bone formation in the growth plate.

Animals↗
PubMed1999

Multiple trophic actions of heparin-binding epidermal growth factor (HB-EGF) in the central nervous system.

The epidermal growth factor (EGF) family of ligands interacts with the epidermal growth factor receptor (EGF-R) to produce numerous direct and indirect actions on central nervous system cells. They induce the proliferation of astrocytes and multipotent progenitors ('stem' cells) and promote the survival and differentiation of postmitotic neurons. Heparin-binding epidermal growth factor (HB-EGF) interacts with both EGF-R and a related receptor, ErbB4, whereas transforming growth factor alpha (TGFalpha) interacts only with EGF-R. Because of the unique characteristics of HB-EGF and the potential utility of EGF family members in brain repair, we examine the effects of HB-EGF on rat and mouse CNS cells in vitro and compare them to those of TGFalpha. We find that, like TGFalpha, HB-EGF stimulates the proliferation of CNS astrocytes and multipotent progenitors. These proliferative effects require the expression of EGF-R, as no such effects are observed in cells derived from EGF-R-/- mice. Both HB-EGF and TGFalpha enhanced the survival of neurons derived from the neocortex and the striatum. Within these neuron-enriched cultures, nestin-positive cells but not neurons express EGF-R mRNA, indicating that the neurotrophic actions of EGF-R ligands are a result of indirect stimulation mediated by non-neuronal cells. The neurotrophic actions of HB-EGF and TGFalpha are accompanied by an elevation in immunoreactive dual phosphorylated mitogen-activated protein kinase (MAP kinase) in neurons, providing evidence that the MAP kinase cascade mediates these actions. In situ hybridization studies demonstrate that HB-EGF mRNA is present within the brainstem as early as E14 and subsequently is found in the developing cortical plate, hippocampus, cerebellar Purkinje cells and ventrobasal thalamus, among other brain areas. These findings indicate that HB-EGF may be an important trophic factor in the developing CNS and is a useful candidate molecule for brain repair strategies.

Animals↗
PubMed1999

alpha1 and alpha2 integrins mediate invasive activity of mouse mammary carcinoma cells through regulation of stromelysin-1 expression.

Tumor cell invasion relies on cell migration and extracellular matrix proteolysis. We investigated the contribution of different integrins to the invasive activity of mouse mammary carcinoma cells. Antibodies against integrin subunits alpha6 and beta1, but not against alpha1 and alpha2, inhibited cell locomotion on a reconstituted basement membrane in two-dimensional cell migration assays, whereas antibodies against beta1, but not against alpha6 or alpha2, interfered with cell adhesion to basement membrane constituents. Blocking antibodies against alpha1 integrins impaired only cell adhesion to type IV collagen. Antibodies against alpha1, alpha2, alpha6, and beta1, but not alpha5, integrin subunits reduced invasion of a reconstituted basement membrane. Integrins alpha1 and alpha2, which contributed only marginally to motility and adhesion, regulated proteinase production. Antibodies against alpha1 and alpha2, but not alpha6 and beta1, integrin subunits inhibited both transcription and protein expression of the matrix metalloproteinase stromelysin-1. Inhibition of tumor cell invasion by antibodies against alpha1 and alpha2 was reversed by addition of recombinant stromelysin-1. In contrast, stromelysin-1 could not rescue invasion inhibited by anti-alpha6 antibodies. Our data indicate that alpha1 and alpha2 integrins confer invasive behavior by regulating stromelysin-1 expression, whereas alpha6 integrins regulate cell motility. These results provide new insights into the specific functions of integrins during tumor cell invasion.

Animals↗
PubMed1999

Defective induction of the transcription factor interferon-stimulated gene factor-3 and interferon alpha insensitivity in human trophoblast cells.

During pregnancy, trophoblast cells of the placenta contact maternal immune cells and yet are protected from attack. One mechanism that may account for this is that trophoblasts show altered expression of major histocompatibility complex (MHC) antigens. The gene for human leukocyte antigen G (HLA-G), a nonclassical gene, is expressed at high levels in trophoblast. Unlike other MHC class I genes, the HLA-G gene lacks an interferon (IFN) response element. Moreover, we demonstrate here that IFN, which regulates classical MHC class I genes in other cell types, does not affect these genes in trophoblast, owing to inactivation of an IFNalpha signaling pathway. Trophoblast cells (JEG-3 and JAR) were found to be selectively refractory to IFN. Specifically, although IFNalpha induced the transcription factors STAT1, STAT2, and IFN regulatory factor-1, and a protective response against encephalomyocarditis virus, it failed to protect the cells from vesicular stomatitis virus, activate a transfected MHC class I gene promoter, and induce the transcription factor IFN-stimulated gene factor (ISGF)-3. The lack of ISGF3 DNA-binding activity apparently was due to diminished p48/ISGF3gamma subunit activity since ISGF3 DNA-binding activity and IFNalpha induction of MHC class I promoter activity were reconstituted by p48/ISGF3gamma supplementation. These data indicate that a specific IFN signaling pathway is inactive in JEG-3 trophoblast cells because of altered activity of p48/ISGF3gamma, and they suggest IFN insensitivity as a mechanism that may help promote feto-placental survival.

Choriocarcinoma↗
PubMed1999

Impaired wound contraction in stromelysin-1-deficient mice.

OBJECTIVE: To determine whether the deletion of stromelysin-1, a single metalloproteinase gene product, will alter the time course and quality of dermal wound repair in mice. SUMMARY BACKGROUND DATA: After dermal injury, a highly coordinated program of events is initiated by formation of a fibrin clot, followed by migration of keratinocytes, contraction of the dermis, recruitment of inflammatory macrophages, formation of granulation tissue with angiogenesis, and finally tissue remodeling. Matrix metalloproteinases are rapidly induced in the dermis and granulation tissue and at the leading edge of the epidermis in the healing wounds. METHODS: Incisional and circular full-thickness wounds 2 to 10 mm were made in the dermis of stromelysin-1-deficient and wild-type mice. The wounds were analyzed for rate of cellular migration and epithelialization. The wound contraction was examined by immunohistochemical staining for alpha-smooth muscle actin and fluorescent staining for fibrillar actin. RESULTS: Independent of the age of the animal, excisional wounds in stromelysin-1-deficient mice failed to contract and healed more slowly than those in wild-type mice. Cellular migration and epithelialization were unaffected in the stromelysin-1-deficient animals. The functional defect in these mice is failure of contraction during the first phase of healing because of inadequate organization of actin-rich stromal fibroblasts. CONCLUSIONS: Excisional dermal wound healing is impaired in mice with a targeted deletion in the stromelysin-1 gene. Incisional wound healing is not affected. These data implicate stromelysin-1 proteolysis during early wound contraction and indicate that stromelysin-1 is crucial for the organization of a multicellular actin network.

Animals↗
PubMed1999

Matrix-degrading proteases and angiogenesis during development and tumor formation.

Embryonic development and tumor progression both require the exquisite coordination of programs for extracellular matrix (ECM) formation and remodeling, and those for angiogenesis and vascular development. Without a vascular supply the normal tissue or tumor is limited in size and organization. Without ECM remodeling the alteration of tissue and tumor boundaries and cellular migrations are limited. Recent insights into the molecular mechanisms regulating the extracellular environment of the growing embryonic tissue or tumors have implicated proteases, the matrix metalloproteinases (MMPs) in particular, in both the process of ECM remodeling and angiogenesis, and in a potential causal relationship between these processes. This review focuses on the roles that MMPs play in regulating three processes in which both proteolysis and vascular development are tightly coordinated: embryo implantation, bone development and tumor progression.

Animals↗
PubMed1999

Signaling through the stromal epidermal growth factor receptor is necessary for mammary ductal development.

Stromal-epithelial interactions are critical in determining patterns of growth, development and ductal morphogenesis in the mammary gland, and their perturbations are significant components of tumorigenesis. Growth factors such as epidermal growth factor (EGF) contribute to these reciprocal stromal-epithelial interactions. To determine the role of signaling through the EGF receptor (EGFR) in mammary ductal growth and branching, we used mice with a targeted null mutation in the Egfr. Because Egfr-/- mice die perinatally, transplantation methods were used to study these processes. When we transplanted neonatal mammary glands under the renal capsule of immuno-compromised female mice, we found that EGFR is essential for mammary ductal growth and branching morphogenesis, but not for mammary lobulo-alveolar development. Ductal growth and development was normal in transplants of mammary epithelium from Egfr-/- mice into wild-type (WT) gland-free fat pads and in tissue recombinants prepared with WT stroma, irrespective of the source of epithelium (StromaWT/Epi-/-, StromaWT/EpiWT). However, ductal growth and branching was impaired in tissue recombinants prepared with Egfr-/- stroma (Stroma-/-/EpiWT, Stroma-/-/Epi-/-). Thus, for ductal morphogenesis, signaling through the EGFR is required only in the stromal component, the mammary fat pad. These data indicate that the EGFR pathway plays a key role in the stromal-epithelial interactions required for mammary ductal growth and branching morphogenesis. In contrast, signaling through the EGFR is not essential for lobulo-alveolar development. Stimulation of lobulo-alveolar development in the mammary gland grafts by inclusion of a pituitary isograft under the renal capsule as a source of prolactin resulted in normal alveolar development in both Egfr-/- and wild-type transplants. Through the use of tissue recombinants and transplantation, we have gained new insights into the nature of stromal-epithelial interactions in the mammary gland, and how they regulate ductal growth and branching morphogenesis.

Animals↗
PubMed1998

Extracellular matrix remodeling during morphogenesis.

The role of proteinases in extracellular matrix remodeling during the developmental program of bone, cartilage, muscle, and epithelial differentiation in the mandibular arch during embryogenesis was investigated. ECM changes accompany morphogenesis during development. The most dramatic changes occur during development of bone and cartilage. The expression of matrix metalloproteinases (MMPs) was altered by regulating expression of MMPs by growth factors, by inhibiting MMP activity, and by genetic ablation of MMPs. The data point to critical roles for MMPs in cartilage development and endochondral bone formation. MMPs appear to regulate not only ECM degradation but also programmed cell death, cell migration, and invasion during these morphogenic processes. The data suggest that matrix metalloproteinases play a pivotal role in the morphogenesis of structures derived from epithelium (oral sulcus), somitic mesoderm (tongue), and cranial neural crest (Meckel's cartilage).

Animals↗
PubMed1998

The significance of matrix metalloproteinases during early stages of tumor progression.

Matrix metalloproteinases (MMPs) orchestrate tissue remodeling and play diverse roles during organ development. They are produced excessively during the course of various pathological conditions, including solid tumors. An important function of MMPs during tumor progression is to provide the proteolytic activity that is necessary both for tumor cells to invade extracellular matrix (ECM) and for neovascularization of tumor tissue by endothelial cells. Recently, independent studies in transgenic animals suggest that MMPs may, in addition, promote very early stages of tumor progression. To investigate this possibility further, we have analyzed the consequences of MMP overexpression in functionally normal and nontumorigenic mouse mammary epithelial cells in culture. Our observations demonstrate that the MMP stromelysin-1 (SL-1) triggers an epigenetic molecular program in mammary epithelial cells that results in a number of phenotypic alterations that eventually culminate in the generation of a malignant tumor-cell phenotype.

Animals↗