In vivo evidence that the stromelysin-3 metalloproteinase contributes in a paracrine manner to epithelial cell malignancy

Metalloproteases as potential therapeutic targets in arthritis treatment

Dysregulated proteolysis of the extracellular matrix of articular cartilage represents a unifying hallmark of the arthritides, and has been a target for therapeutic intervention for some time, although clinical efficacy has been elusive. Members of the 'A disintegrin and metalloprotease with thrombospondin motifs' and matrix metalloprotease families are considered to be collectively responsible for cartilage catabolism, such that inhibition of these activities is theoretically a highly attractive strategy for preventing further proteolytic damage. This review outlines the biology of these metalloproteases and what we have learnt from inhibition studies and transgenics, and highlights the important questions that this information raises for the future development of therapeutics directed towards metalloproteases for arthritis treatment.

Matrix metalloproteinases stimulate epithelial-mesenchymal transition during tumor development

Matrix metalloproteinases (MMPs) are a family of more than 28 enzymes that were initially identified on the basis of their ability to cleave most elements of the extracellular matrix (ECM) but have subsequently been found to be upregulated in nearly every tumor type. As digestion of the ECM is essential for tumor invasion and metastasis, MMPs have been studied for their role in these later stages of tumor development. More recently, exposure to these enzymes has been found to impact cellular signaling pathways that stimulate cell growth at early stages of tumor progression. MMPs have also been found to cleave intracellular targets and so inducing mitotic abnormalities and genomic instability. Emerging evidence indicates that tumor-associated MMPs can also stimulate processes associated with epithelial-mesenchymal transition (EMT), a developmental process that is activated in tumor cells during cell invasion and metastasis. Investigations of potential therapeutic MMP inhibitors aimed at blocking the protumorigenic tissue alterations induced by MMPs have been complicated by the side effects associated with nonspecific inhibition of normal physiological processes; recent investigations have shown how delineation of the extracellular targets and intracellular signaling pathways by which MMP action on cancer cells can induce EMT provides insight into novel therapeutic targets. Here, we provide an overview of recent findings of MMP action in tumors and the mechanisms by which MMPs induce both phenotypic and genotypic alterations that facilitate tumor progression.

MT1-MMP is required for efficient tumor dissemination in experimental metastatic disease

Membrane-type I matrix metalloproteinase (MT1-MMP) is associated with multiple forms of cancer including mammary cancer. To directly evaluate the significance of MT1-MMP expression in tumor progression and metastasis using a genetically induced cancer model, we crossed MT1-MMP-deficient mice to MMTV-polyoma virus middle T-antigen (PyMT) mice. Expression of PyMT in the MT1-MMP-deficient background consistently resulted in hyperplasia of the mammary gland as seen in wild-type PyMT littermates. Following orthotopic transplantation of PyMT+ glands into the cleared mammary fat pad of syngeneic recipient mice, MT1-MMP-deficient tumors were palpable earlier than wild-type tumors. Moreover, MT1-MMP-deficient tumors grew to the experimental end point size quicker than control tumors, but demonstrated markedly reduced ability to metastasize to the lungs of recipient mice. Accordingly, MT1-MMP-deficient mice displayed an overall reduction in metastasis count of 50%. MT1-MMP was expressed solely in the stroma of PyMT-induced tumors and those metastatic nodules that formed in the lungs were devoid of MT1-MMP expression. Stromal fibroblasts isolated from MT1-MMP-deficient tumors did not degrade type I collagen suggesting that efficient dissemination of tumor cells is dependent on stromal cell remodeling of the tumor environment. The data demonstrate directly that MT1-MMP-mediated proteolysis by stromal cells is important in the metastatic process.

Breast cancer progression: insights into multifaceted matrix metalloproteinases

The restricted view of matrix metalloproteinases (MMPs) as simple destroyers of extracellular matrix components has largely ignored their substantial contribution in many aspects of cancer development and metastatic dissemination. Over the last few years, the relevance of MMPs in the processing of a large array of extracellular and cell surface-associated proteins has grown considerably. Our knowledge about the complex functions of MMPs and how their contribution may differ throughout cancer progression is rapidly expanding. These new findings provide several explanations for the lack of success of MMP inhibition in clinical trials. A complete understanding of MMP biology is needed before considering them, their substrates or their products as therapeutic targets. In this review, we explore the different faces of MMP implication in breast cancer progression by considering both clinical and fundamental aspects.

Regulation of extracellular matrix remodeling and cell fate determination by matrix metalloproteinase stromelysin-3 during thyroid hormone-dependent post-embryonic development

Interactions between cells and extracellular matrix (ECM), in particular the basement membrane (BM), are fundamentally important for the regulation of a wide variety of physiological and pathological processes. Matrix metalloproteinases (MMP) play critical roles in ECM remodeling and/or regulation of cell-ECM interactions because of their ability to cleave protein components of the ECM. Of particular interest among MMP is stromelysin-3 (ST3), which was first isolated from a human breast cancer and also shown to be correlated with apoptosis during development and invasion of tumor cells in mammals. We have been using intestinal remodeling during thyroid hormone (TH)-dependent amphibian metamorphosis as a model to study the role of ST3 during post-embryonic tissue remodeling and organ development in vertebrates. This process involves complete degeneration of the tadpole or larval epithelium through apoptosis and de novo development of the adult epithelium. Here, we will first summarize expression studies by us and others showing a tight spatial and temporal correlation of the expression of ST3 mRNA and protein with larval cell death and adult tissue development. We will then review in vitro and in vivo data supporting a critical role of ST3 in TH-induced larval epithelial cell death and ECM remodeling. We will further discuss the potential mechanisms of ST3 function during metamorphosis and its broader implications.

Resident stromal cell-derived MMP-9 promotes the growth of colorectal metastases in the liver microenvironment

Colorectal cancer, the second leading cause of cancer deaths in the United States, has a high probability of metastasizing to the liver. Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases that are implicated in cancer metastasis and many aspects of tumor progression. Using a splenic injection experimental metastasis model, mice that are genetically deficient in MMP-9 demonstrated a nearly 2-fold decrease in liver weight compared with wild type (WT) mice following injection with MC38 syngeneic colorectal cancer cells. Bioluminesence imaging data demonstrates an early negative effect on tumor growth in MMP-9 null mice when compared with WT controls. Reconstitution of the bone marrow in MMP-9-/- mice with cells competent to produce MMP-9 did not recapitulate the WT phenotype of overwhelming burden of metastatic disease in the liver. In situ hybridization revealed the presence of MMP-9 mRNA in both MC38 tumor cells and in surrounding stromal cells, and immunostaining with anti MMP-9 was consistent with MMP-9 expression by resident liver Kupffer cells. Stromal-derived MMP-9 contributes to the establishment and growth of colorectal metastases in the liver. Stromal MMP-9 was derived from resident cells, most likely Kupffer cells, as opposed to infiltrating bone marrow-derived cells and the effect of stromal MMP-9 was independent of expression of MMP-9 by tumor cells. Stromal-derived MMP-9 may represent an important target for selective inhibition in the treatment of metastases. (c) 2007 Wiley-Liss, Inc.

Signal transducer and activator of transcription 3 activation promotes invasive growth of colon carcinomas through matrix metalloproteinase induction

Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in colorectal carcinomas (CRCs). Here, we define the relationship between STAT3 function and the malignant properties of colon carcinoma cells. Elevated activation of STAT3 enhances invasive growth of the CRC cell lines. To address mechanisms through which STAT3 influences invasiveness, the protease mRNA expression pattern of CRC biopsies was analyzed and correlated with the STAT3 activity status. These studies revealed a striking coincidence of STAT3 activation and strong expression of matrix metalloproteinases MMP-1, -3, -7, and -9. Immunohistological examination of CRC tumor specimens showed a clear colocalization of MMP-1 and activated STAT3. Experimentally induced STAT3 activity in CRC cell lines enhanced both the level of MMP-1 mRNA and secreted MMP-1 enzymatic activity. A direct connection of STAT3 activity and transcription from the MMP-1 promoter was shown by reporter gene experiments. Moreover, high-affinity binding of STAT3 to STAT recognition elements in both the MMP-1 and MMP-3 promoter was demonstrated. Xenograft tumors arising from implantation of CRC cells into nude mice showed simultaneous appearance and colocalization of p-Y-STAT3 and MMP-1 expression. Our results link aberrant activity of STAT3 in CRC to malignant tumor progression through upregulated expression of MMPs.

siRNA targeted against matrix metalloproteinase 11 inhibits the metastatic capability of murine hepatocarcinoma cell Hca-F to lymph nodes

Matrix metalloproteinase-11 (MMP-11) belongs to the particular member of MMP family, a group of zinc-dependent endopeptidases involved in tumor progression, invasion and metastasis. MMP-11 is strongly expressed in tumor cells and stromal fibroblasts located in the immediate vicinity of tumor. This study investigated the possible role of MMP-11 expression in mouse hepatocarcinoma cell line Hca-F with highly lymphatic metastasis potential by RNA interference (RNAi) approach. The results showed that a small interfering RNA (siRNA) targeted against MMP-11 significantly impeded Hca-F cells proliferation and colony formation in soft agar, as well as resulted in Hca-F cell apoptosis. This reduction of MMP-11 expression also led to the decreased migration and adhesion of Hca-F cells dramatically both in vitro and in vivo. Furthermore, in vivo metastasis assay indicated that down-regulation of MMP-11 expression in Hca-F cells attenuated the metastatic potential of Hca-F cells to peripheral lymph nodes. These data together provide compelling evidence into the function of MMP-11 and suggest that MMP-11 act as a tumor lymphatic metastasis-associated gene, and could represent a new potential target for gene therapy.

Matrix metalloproteinases and the regulation of tissue remodelling

Matrix metalloproteinases (MMPs) were discovered because of their role in amphibian metamorphosis, yet they have attracted more attention because of their roles in disease. Despite intensive scrutiny in vitro, in cell culture and in animal models, the normal physiological roles of these extracellular proteases have been elusive. Recent studies in mice and flies point to essential roles of MMPs as mediators of change and physical adaptation in tissues, whether developmentally regulated, environmentally induced or disease associated.

Extracellular proteolysis in transgenic mouse models of breast cancer

Growth and invasion of breast cancer require extracellular proteolysis in order to physically restructure the tissue microenvironment of the mammary gland. This pathological tissue remodeling process depends on a collaboration of epithelial and stromal cells. In fact, the majority of extracellular proteases are provided by stromal cells rather than cancer cells. This distinct expression pattern is seen in human breast cancers and also in transgenic mouse models of breast cancer. The similar expression patterns suggest that transgenic mouse models are ideally suited to study the role of extracellular proteases in cancer progression. Here we give a status report on protease intervention studies in transgenic models. These studies demonstrate that proteases are involved in all stages of breast cancer progression from carcinogenesis to metastasis. Transgenic models are now beginning to provide vital mechanistic insight that will allow us to combat breast cancer invasion and metastasis with new protease-targeted drugs.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

Evidence for a cooperative role of gelatinase A and membrane type-1 matrix metalloproteinase during Xenopus laevis development

Matrix metalloproteinases (MMPs) are a large family of extracellular or membrane-bound proteases. Their ability to cleave extracellular matrix (ECM) proteins has implicated a role in ECM remodeling to affect cell fate and behavior during development and in pathogenesis. We have shown previously that membrane-type 1 (MT1)-MMP [corrected] is coexpressed temporally and spatially with the MMP gelatinase A (GelA) in all cell types of the intestine and tail where GelA is expressed during Xenopus laevis metamorphosis, suggesting a cooperative role of these MMPs in development. Here, we show that Xenopus GelA and MT1-MMP interact with each other in vivo and that overexpression of MT1-MMP and GelA together in Xenopus embryos leads to the activation of pro-GelA. We further show that both MMPs are expressed during Xenopus embryogenesis, although MT1-MMP gene is expressed earlier than the GelA gene. To investigate whether the embryonic MMPs play a role in development, we have studied whether precocious expression of these MMPs alters development. Our results show that overexpression of both MMPs causes developmental abnormalities and embryonic death by a mechanism that requires the catalytic activity of the MMPs. More importantly, we show that coexpression of wild type MT1-MMP and GelA leads to a cooperative effect on embryonic development and that this cooperative effect is abolished when the catalytic activity of either MMP is eliminated through a point mutation in the catalytic domain. Thus, our studies support a cooperative role of these MMPs in embryonic development, likely through the activation of pro-GelA by MT1-MMP.

Modifying the soil to affect the seed: role of stromal-derived matrix metalloproteinases in cancer progression

In the 1980's, as the importance of matrix metalloproteinases (MMPs) in cancer progression was discovered, it was recognized that in most tumors these proteases were abundantly and sometimes exclusively expressed not by tumor cells, but by normal host-derived cells like fibroblasts, vascular endothelial cells, myofibroblasts, pericytes or inflammatory cells that contribute to the tumor microenvironment. Later experiments in mice deficient in specific MMPs revealed that host-derived MMPs play a critical role not only in tumor cell invasion, but also in carcinogenesis, angiogenesis, vasculogenesis and metastasis. Tumor cells secrete many factors, cytokines and chemokines that directly or indirectly increase the expression of these MMPs in the tumor microenvironment where they exert extracellular matrix (ECM) degrading and sheddase activities. The knowledge of the complex role that stromal-derived MMPs play in the interaction between tumor cells and stromal cells should allow us to consider specific windows in cancer treatment when MMP inhibition could have a valuable therapeutic effect.

Matrix metalloproteinases and tumor metastasis

Functions of individual matrix metalloproteinases (MMPs) differentially expressed by tumor cells and stromal cells, are finely regulated by their spatial as well as temporal interactions with distinct cellular and extracellular components of the tumor microenvironment and also distant pre-metastatic sites. Certain aspects of MMP involvement in tumor metastasis such as tumor-induced angiogenesis, tumor invasion, and establishment of metastatic foci at the secondary site, have received extensive attention that resulted in an overwhelming amount of experimental and observational data in favor of critical roles of MMPs in these processes. In particular, dependency of tumor angiogenesis on the activity of MMPs, especially that of MMP-9, renders this step possibly the most effective target of synthetic MMP inhibitors. MMP functioning in other stages of metastasis, including the escape of individual tumor cells from the primary tumor, their intravasation, survival in circulation, and extravasation at the secondary site, have not yet received enough consideration, resulting in insufficient or controversial data. The major pieces of evidence that are most compelling and clearly determine the role and involvement of MMPs in the metastatic cascade are provided by molecular genetic studies employing knock-out or transgenic animals and tumor cell lines, modified to overexpress or downregulate a specific MMP. Findings from all of these studies implicate different functional mechanisms for both tumor and stromal MMPs during distinct steps of the metastatic cascade and indicate that MMPs can exhibit pro-metastatic as well as anti-metastatic roles depending on their nature and the experimental setting. This dual function of individual MMPs in metastasis has become a major focus of this review.

Exploring the tumour environment: cancer-associated fibroblasts as targets in cancer therapy

Stroma cells contribute to the microenvironment that is essential for cancer growth, invasion and metastatic progression. Fibroblasts, often termed myofibroblasts or cancer-associated fibroblasts (CAFs), represent the most abundant cell type in the tumour stroma. The demonstrated tumour-promoting capacities of CAFs has increased the interest to exploit them as drug targets for anticancer therapy. Although single factors, such as platelet-derived growth factor, transforming growth factor-beta1, hepatocyte growth factor and matrix metalloproteinases have been identified as mediators in the fibroblast tumour interaction, the morphological and functional differences of CAFs compared with their normal counterparts are only incompletely understood. Recently, novel global methods for gene expression profiling were applied to comprehensively characterise CAFs from breast, pancreas, colon and basal cell cancer in their in situ environment. The analysis of different CAF preparations revealed regulated genes that were previously not described in the tumour-stroma context. Additionally, besides a few striking overlaps, the comparison of the gene lists indicates a high level of heterogeneity in the expression pattern of CAFs from different tumour types. Together, these studies emphasise the importance of cross-talk between stromal and malignant cells of the tumour. It is likely that the continued characterisation of this interaction, and the molecular identification of key mediators, will provide insights into tumour biology and suggest novel therapeutic options.

Collagenase in cranial morphogenesis

Collagen is the most abundant extracellular matrix protein in connective tissues of higher animals. The growth of connective tissues is intimately linked to the ability to model and remodel the collagen-rich matrices of the organism at critical points during development and growth to allow expansion and adaptation of tissue interfaces. The mammalian cranium is one such place where collagen remodeling is required for proper growth, and this review explores the consequences of abrogated collagen remodeling as they materialize in a mouse model deficient for the membrane type 1 matrix metalloproteinase.

Transcriptional regulation of the Xenopus laevis Stromelysin-3 gene by thyroid hormone is mediated by a DNA element in the first intron

The matrix metalloproteinase (MMP) stromelysin-3 (ST3) (MMP11) was first isolated as a breast cancer-associated gene and is expressed in diverse human carcinomas and various developmental processes involving apoptosis. The Xenopus laevis ST3 is highly up-regulated by thyroid hormone (T3) during amphibian metamorphosis, and its expression is spatially and temporally correlated with apoptosis in different tissues. Furthermore, it has been shown in vivo and in organ cultures to play a critical role in regulating T3-induced epithelial cell death during intestinal metamorphosis. Earlier studies suggest that ST3 is a direct T3 response gene, although a thyroid hormone response element (TRE) was not found in the initial analysis of the ST3 promoter. Here, we have identified a strong TRE consisting of two nearly perfect direct repeats of the consensus nuclear hormone receptor binding element AGGTCA separated by 4 bp in the first intron of the Xenopus ST3 gene. We show that the heterodimers of T3 receptor (TR) and 9-cis-retinoic acid receptor bind to the TRE both in vitro and in vivo in the context of chromatin. Furthermore, T3 induces strong activation of the promoter through the intronic TRE. Interestingly, although the unliganded TR/9-cis-retinoic acid receptor was able to recruit corepressors to the promoter, it had little repressive effect on the promoter in vivo. These results suggest that the intronic TRE mediates the inductive effect of T3 and that promoter context plays an important role in gene repression by unliganded TR.

Successful ovulation in plasminogen-deficient mice treated with the broad-spectrum matrix metalloproteinase inhibitor galardin

Many studies have suggested the hypothesis that the plasminogen activator (PA) system and the matrix metalloproteinase (MMP) system, either separately or in combination, may provide the proteolytic activity that is required for rupture of the follicular wall at the time of ovulation. Our recent studies on ovulation in plasminogen (plg)-deficient mice have, however, shown that plasmin is not required for normal ovulation, leading us to the hypothesis that MMPs may be a more important source of proteolysis for this process. To investigate the role of MMPs and also the possibility of a functional overlap or synergy between the MMP and PA systems during ovulation, we have studied ovulation efficiency in wild-type and plg-deficient mice treated with the broad-spectrum MMP inhibitor galardin. We found that in both wild-type mice and heterozygous plg-deficient (plg+/-) mice that had been treated with galardin prior to ovulation, there was a mild (18-20%) reduction in ovulation efficiency. Surprisingly, galardin treatment of plg-deficient (plg-/-) mice only caused an additional 14% reduction in ovulation efficiency as compared to vehicle-treated plg-/- mice. Our data therefore suggest that although MMPs may play a role in degradation of the follicular wall, they may not be obligatory for ovulation. In contrast to previous studies on tissue remodeling during wound healing and placental development, we have demonstrated that there is no obvious functional overlap or synergy between the PA and MMP systems, which has previously been thought to be essential for the ovulatory process.

Matrix metalloproteinase-9 from bone marrow-derived cells contributes to survival but not growth of tumor cells in the lung microenvironment

The role of specific stromal-derived matrix metalloproteinases (MMPs) was analyzed in experimental metastasis assays in wild-type and either MMP-9, MMP-7, or MMP-2 null mice. MMP-9 null mice showed an 81% reduction in Lewis lung carcinoma tumor number, whereas MMP-7 null mice showed a 42% increase in tumor number, and there was no difference in tumor number in MMP-2 null mice compared with wild-type controls. Similarly, in an orthotopic model of lung cancer, 50% fewer MMP-9 null mice were able to establish tumors in the lung compared with control mice, although the size of the tumors was not different. The effect of MMP-9 on lung tumor colonization was dependent on the expression of MMP-9 from bone marrow-derived cells and is most likely contributed by neutrophils. To examine temporal effects of stromal MMP-9, bioluminescence imaging from luciferase-expressing human lung cancer-derived A549 cells revealed that there were fewer tumor cells in the lungs of MMP-9 null mice as early as 19 hours after injection compared with control mice, with no difference in subsequent growth rates. Six hours after injection of tumor cells, MMP-9 null mice showed a 4-fold increase in the percent of tumor cells undergoing apoptosis compared with control mice. We conclude that MMP-9 from the bone marrow contributes to the early survival and establishment of tumors in the lung and has no effect on subsequent growth. These results provide insights into the failure of MMP inhibitors in clinical trials in patients with late-stage lung cancer.

Effect of different ERK2 protein localizations on prognosis of patients with invasive breast carcinoma

Mitogen-activated protein kinase (MAP kinase) pathways represent a cascade of phosphorylation events, including three pivotal kinases, Raf, MEK and ERK1/2, which have been implicated in the pathogenesis of cancer. We examined 151 cases of invasive breast carcinoma by immunohistochemistry and compared the ERK2 expression with clinicopathological parameters, MMP-11 immunoexpression and patients' survival. ERK2 immunoexpression was detected in the cytoplasm and nucleus of cancer cells in 37.7% and 19.2% of cases, respectively. Nuclear ERK2 was inversely correlated with ER (p = 0.039), whereas cytoplasmic ERK2 was positively correlated with MMP-11 in fibroblasts (p = 0.032) and more often expressed in lobular than ductal carcinomas (p = 0.026). Nuclear ERK2 expression was found to be an independent prognostic factor of shortened overall survival of patients (p = 0.040), while cytoplasmic ERK2 had an independent, favorable effect on both disease-free and overall survival (p < 0.0001 and p = 0.002, respectively). These findings suggest that the different subcellular localizations of ERK2 seem to be related to different, possibly contradictory, effects on patient survival.

Stromelysin-3 is a potent negative regulator of adipogenesis participating to cancer cell-adipocyte interaction/crosstalk at the tumor invasive front

The initial invasive processes during cancer development remain largely unknown. Stromelysin-3/matrix metalloproteinase 11 (ST3/MMP11) is associated with tumor invasion and poor prognosis. We present novel evidence that adipocytes present at human breast tumor invasive front are induced by cancer cells to express ST3. Using mouse syngeneic model, light and electron microscopy showed that in ST3-deficient mice but not in wild-type mice, forced cancer cell-adipocyte interaction/crosstalk results in adipocyte membrane alteration, allowing cancer cell fat infiltration and death. Thus, adipocytes are involved in initial cancer cell survival into connective tissue, and this effect is ST3 mediated. This suggested that ST3 might play a role in adipocyte metabolism. Accordingly, ST3-deficient mice exhibited fat excess and increased mRNA levels of peroxisome proliferator-activated receptor gamma (PPARgamma) and adipocyte protein 2 (aP2) adipogenic markers, indicating that, in vivo, ST3 negatively regulates fat homeostasis. Moreover, ST3-deficient mouse embryonic fibroblasts exhibited a dramatic enhanced potential to differentiate into adipocytes associated with increased PPARgamma and aP2 expression, and recombinant ST3 treatment reverted their differentiation. Thus, in vitro, ST3 reduces adipocyte differentiation in an autocrine manner. High fibroblasts/adipocytes ratio is a stroma feature, and peritumoral fibroblast origin remains debated. Our results support the concept that invading cancer cells aberrantly restore the negative ST3 function on adipogenesis into proximal adipocytes/preadipocytes, leading to the accumulation/maintenance of a particular peritumoral fibroblast subpopulation. Accordingly, in human breast tumors, we observed that ST3-expressing peritumoral fibroblasts are distinct from alpha-smooth muscle actin-expressing myofibroblasts. This constitutes the first report of implication of a MMP in cancer cell-adipocyte interaction/crosstalk during early steps of connective tissue invasion.

Expression of stromelysin-3 (matrix metalloproteinase-11) in macrophages of murine thymus following thymocyte apoptosis

High expression of stromelysin-3 (ST-3), also known as matrix metalloproteinase-11, has been implicated in tumor progression and intense tissue remodeling. Nonetheless, details of the cell type(s) expressing ST-3 are less well defined. Here, we report that ST-3 expression was elevated in mouse thymus following thymocyte apoptosis after administration of anti-CD3 Ab. TUNEL analysis revealed that many thymocytes in the cortical region were induced to apoptotic cell death 14 h after the injection. After an additional 2-6 h, ST-3 expression in the thymus was more apparent. Co-staining analysis by anti-ST-3 and F4/80 Abs showed that most F4/80-positive macrophages were also positive for ST-3. Murine peritoneal macrophages were found to constitutively express ST-3, and exposure to apoptotic cells hardly affected ST-3 expression in the macrophages. Taken together, our results indicate that ST-3 is not involved in the execution process of thymocyte apoptosis, and the increased levels of ST-3 in the thymus may be due to the presence of macrophages responsible for clearance of apoptotic cells.

Functions for proteinases in the ovulatory process

The ovary is a unique and dynamic organ in respect to rapid and extensive degrees of tissue development and remodeling that are periodically repeated in the female reproductive activity. Ovulation is a directed and sequential process accompanied by broad-spectrum proteolysis and culminates in the follicular rupture to release the matured oocyte. This review will focus on the potential roles of six representative proteinases that are involved in various aspects of ovulatory processes: matrix metalloproteinases (MMPs), plasminogen activator (PA)/plasmin, a disintegrin and metalloproteinase domain with thrombospondin motif (ADAMTS), cathepsin-L, pregnancy-associated plasma protein-A (PAPP-A), and bone morphogenetic protein 1/mammalian Tolloid (BMP-1/mTld). Based on the studies of expression and function, these selected proteinases provide and share diverse functions ranging from cleaving components of the extracellular matrix (ECM) to modulating non-ECM molecules, such as various growth factors and their binding proteins. Consistently, the genetic deletion of each individual gene in mice shows their functional overlap in the reproductive activity.

Phase I trial of the matrix metalloproteinase inhibitor marimastat combined with carboplatin and paclitaxel in patients with advanced non-small cell lung cancer

PURPOSE

Marimastat is an orally bioavailable inhibitor of matrix metalloproteinases. A phase I study was initiated to determine whether conventional doses of carboplatin and paclitaxel are tolerated when combined with marimastat and to assess the influence of marimastat on paclitaxel pharmacokinetics.

EXPERIMENTAL DESIGN

Three dose levels were evaluated. Marimastat (10 or 20 mg oral administration b.i.d.) was administered continuously with paclitaxel (175 or 200 mg/m(2) as a 3-hour i.v. infusion) and carboplatin (at a dose providing an area under the free drug plasma concentration-time curve of 7 mg min/mL) administered each 3 weeks. Toxicity and response were evaluated throughout the intended four cycles of combined therapy. The plasma pharmacokinetics of paclitaxel was determined in each patient both without concurrent marimastat and after receiving marimastat for 1 week.

RESULTS

Twenty-two chemotherapy-naive patients with stage IIIb (27%) or stage IV (73%) non-small cell lung cancer were enrolled. Their median age was 56 years (range, 39-73 years), 50% were female, and their performance status (Eastern Cooperative Oncology Group) ranged from 0 to 2. Treatment was well tolerated, as 18 (82%) of the patients completed all four cycles of chemotherapy without dose-limiting toxicity. Grade 2 musculoskeletal toxicities were reported in 3 of 12 patients receiving marimastat (20 mg b.i.d.). Nine patients required dose reductions, predominantly related to low-grade myelosuppression. Partial responses occurred in 12 of 21 (57%) evaluable patients with disease stabilization in another 5 (19%). Marimastat had no effect on paclitaxel pharmacokinetics.

CONCLUSIONS

The administration of marimastat (10 mg b.i.d.) with paclitaxel (200 mg/m(2)) and carboplatin at an area under the free drug plasma concentration-time curve of 7 mg min/mL was well tolerated with no apparent pharmacokinetic interaction. Study of this drug combination in the adjuvant setting should be considered if tissue inhibition of matrix metalloproteinase activity can first be shown.

Tumor-stroma interactions: their role in the control of tumor cell invasion

The development and progression of tumors result from the concerted activity not only of tumor cells with neighboring cells e.g., fibroblasts and inflammatory cells. Host-tumor interactions are considered critical in tumor invasion and metastasis. In vitro studies as well as established in vivo models have analysed the reciprocal effects of tumor-host interactions for the tumor invasion process. These studies have shown that modifications in the extracellular matrix composition surrounding the tumors as well as alterations in the expression of tumor cell receptors or in the expression of growth factors/cytokines and proteases, are critical regulators of a developing tumor. We shortly review the most important and well characterized mechanisms involved in the progression of tumor cells through tissues, especially those participating in cellular communication, cell adhesion, and proteolysis.

From a unique cell to metastasis is a long way to go: clues to stromelysin-3 participation

Stromelysin-3 (ST3) overexpression is associated with poor patient clinical outcome in numerous carcinomas. The ST3 is expressed by peritumoral fibroblast-like cells. Review of the literature shows that ST3 is an active partner of cancer cells along the whole natural cancer history, and is essential for optimal tumor development as it reduces death of cancer cells invading adjacent connective tissues at the primary tumor site. Paradoxically, ST3 lowers metastasis development in vivo in mice. However, this beneficial effect does not counterbalance the deleterious anti-apoptotic function of ST3.

A Causative Role of Stromelysin-3 in Extracellular Matrix Remodeling and Epithelial Apoptosis during Intestinal Metamorphosis in Xenopus laevis

The matrix metalloproteinases are a family of proteases capable of degrading various components of the extracellular matrix. Expression studies have implicated the involvement of the matrix metalloproteinase stromelysin-3 (ST3) in tissue remodeling and pathogenesis. However, the in vivo role of ST3 has been difficult to study because of a lack of good animal models. Here we used intestinal remodeling during thyroid hormone-dependent metamorphosis of Xenopus laevis as a model to investigate in vivo the role of ST3 during postembryonic organ development in vertebrates. We generated transgenic tadpoles expressing ST3 under control of a heat shock-inducible promoter. We showed for the first time in vivo that wild type ST3 but not a catalytically inactive mutant was sufficient to induce larval epithelial cell death and fibroblast activation, events that normally occur only in the presence of thyroid hormone. We further demonstrated that these changes in cell fate are associated with altered gene expression in the intestine and remodeling of the intestinal basal lamina. These results thus suggest that ST3 regulates cell fate and tissue morphogenesis through direct or indirect ECM remodeling.

Stromelysin 3, Ets-1, and vascular endothelial growth factor expression in oral precancerous and cancerous lesions: correlation with microvessel density, progression, and prognosis

PURPOSE

Identification of molecular changes characteristic of development and progression of oral cancer are of paramount importance for effective intervention. Stromelysin 3 (MMP11) is a unique matrix metalloproteinase shown to have dual function during cancer progression. The transcription factor Ets-1 and vascular endothelial growth factor (VEGF) are important proangiogenic factors in cancer. This study was designed to test the hypothesis that concomitant expression of stromelysin 3, Ets-1, and/or VEGF affects the development, progression, and prognosis of oral cancer.

PATIENTS AND METHODS

Immunohistochemical analysis of stromelysin 3, Ets-1, VEGF, and platelet/endothelial cell adhesion molecule 1 (a marker for intratumoral microvessel density) was carried out in serial paraffin embedded tissue sections of 220 oral squamous cell carcinomas (OSCC), 90 precancerous lesions (59 hyperplasias and 31 dysplasias), and 81 matched histologically normal oral tissues.

RESULTS

Ets-1, VEGF, and stromelysin 3 expression independently correlated with increased intratumoral microvessel density in precancerous lesions (P = 0.05, 0.001, and 0.026, respectively) as well as in SCCs (P = 0.005, 0.01, and 0.031, respectively). Logistic regression analysis revealed that concomitant expression of stromelysin 3 and Ets-1 (stromelysin 3(+)/ Ets-1(+) phenotype; odds ratio, 3.7; P = 0.001) was the most significant predictor for transition to precancerous stage, whereas dual expression of stromelysin 3 and VEGF (stromelysin 3(+)/ VEGF(+) phenotype; odds ratio, 2.07; P = 0.004) was the most important predictor for progression from precancerous stage to frank malignancy. Intriguingly, Ets-1 expression was significantly associated with VEGF expression and stromelysin 3 expression in precancerous tissues as well as OSCCs. Follow-up data for 144 patients for a maximum period of 115 months showed that VEGF [hazards ratio (HR), 4.532; P = 0.004] and Ets-1 (HR = 2.182; P = 0.049) expression significantly correlated with reduced disease-free survival in univariate analysis. In bivariate analysis, patients harboring Ets-1(+)/VEGF(+) phenotype had the worst survival (median disease-free survival, 50 months; HR, 2.943; P = 0.003). Multivariate analysis using Cox's proportional hazards model showed that increased VEGF expression was the most significant adverse prognosticator in OSCC patients (HR, 4.470; P = 0.004).

CONCLUSIONS

In conclusion, this study provides the first evidence of concomitant expression of stromelysin 3, VEGF, and Ets-1 in clinical specimens in different stages of development of oral cancer. In early stages, concomitant expression of stromelysin 3 and Ets-1 favors the development of a precancerous state, whereas dual expression of stromelysin 3 and VEGF is associated with progression from precancerous to cancerous state. VEGF expression is an adverse prognosticator for disease-free survival.

Suppression of tumor development and metastasis formation in mice lacking the S100A4(mts1) gene

The S100A4(mts1) protein stimulates metastatic spread of tumor cells. An elevated expression of S100A4 is associated with poor prognosis in many human cancers. Dynamics of tumor development were studied in S100A4-deficient mice using grafts of CSML100, highly metastatic mouse mammary carcinoma cells. A significant delay in tumor uptake and decreased tumor incidences were observed in S100A4(-/-) mice compared with the wild-type controls. Moreover, tumors developed in S100A4(-/-) mice never metastasize. Immunohistochemical analyses of these tumors revealed reduced vascularity and abnormal distribution of host-derived stroma cells. Coinjection of CSML100 cells with immortalized S100A4(+/+) fibroblasts partially restored the dynamics of tumor development and the ability to form metastasis. These fibroblasts were characterized by an enhanced motility and invasiveness in comparison with S100A4(-/-) fibroblasts, as well as by the ability to release S100A4 into the tumor environment. Taken together, our results point to a determinative role of host-derived stroma cells expressing S100A4 in tumor progression and metastasis.

Modulation of monocyte matrix metalloproteinase-2 by breast adenocarcinoma cells

Introduction

The presence of monocyte and macrophage cells in growing breast tumors, and the positive relationship between the degree of immune cell infiltration and tumor growth, suggest a possible paracrine growth regulatory function of immune cells in breast cancer.

Method

To better understand the interaction between monocytes and breast cancer cells, in vitro matrix metalloproteinase and tissue inhibitor of metalloproteinase activity was assessed from the THP-1 myeloid cell line in response to conditioned media from two breast cancer cell lines, MCF-7 and MDA-MB-231.

Results

Enzymography and immunoblotting revealed increased MMP-2 as well as increased levels of TIMP-1 and TIMP-2. Furthermore, a significant increase in the invasive potential of MCF-7 and MDA-MB-231 cells was noted in response to THP-1 cell-conditioned media.

Conclusion

These data demonstrate that monocyte cells in the breast tumor microenvironment play an important role in the modulation of MMPs, which may have a significant effect on the control of tumor growth and metastatic spread.

Upregulation of matrix metalloproteinases (MMPs) in breast cancer xenografts: a major induction of stromal MMP-13

In human breast cancer (HBC), as with many carcinoma systems, most matrix metalloproteinases (MMPs) are largely expressed by the stromal cells, whereas the tumour cells are relatively silent in MMP expression. To determine the tissue source of the most relevant MMPs, we xenografted HBC cell lines and HBC tissues into the mammary fat pad (MFP) or bone of immunocompromised mice and measured the expression of human and mouse MMP-2, -9, -11, -13, membrane-type-1 MMP (MT1-MMP), MT2-MMP and MT3-MMP by species-specific real-time quantitative RT-PCR. Our data confirm a stromal origin for most tumour-associated MMPs and indicate marked and consistent upregulation of stromal (mouse) MMP-13 and MT1-MMP in all xenografts studied, irrespective of implantation in the MFP or bone environments. In addition, we show increased expression of both human MMP-13 and human MT1-MMP by the MDA-MB-231 tumour cells grown in the MFP compared to in vitro production. MMP protein and activity data confirm the upregulation of MMP mRNA production and indicate an increase in the activated MMP-2 species as a result of tumour implantation. These data directly demonstrate tumour induction of MMP production by stromal cells in both the MFP and bone environments. These xenografts are a valuable means for examining in vivo production of MMPs and suggest that MMP-13 and MT1-MMP will be relevant targets for inhibiting breast cancer progression.

Is desmoplasia a protective factor for survival in patients with colorectal carcinoma?

BACKGROUND & AIMS

The role of desmoplasia in colorectal carcinoma progression is unclear and the presence of collagen stroma may represent a barrier against cancer diffusion and vascular invasion or a stroma to build up and support the tumor. The aim of this study was to evaluate the effect of desmoplastic response on long-term survival of patients who underwent radical resection for colorectal carcinoma.

METHODS

The study included 429 patients who underwent radical colorectal resection for cancer with a median follow-up period of 72.8 months.

RESULTS

At univariate analysis significant associations were observed between desmoplasia and histologic type, parietal infiltration, growth pattern, and staging. No associations were found between desmoplasia and the other clinical and histologic parameters. The multivariate analysis stratified for tumor stage revealed that the factor showing the most favorable influence on time to death was desmoplasia. The presence of desmoplasia was likely to decrease the failure rate to a third of the rate experienced by patients without desmoplasia. Parietal infiltration was associated with an increased risk for a shortened time to death.

CONCLUSIONS

Our results favor the view that desmoplasia is a protective factor for survival in patients with colorectal carcinoma. This finding is consistent with the hypothesis that desmoplasia may prevent cancer invasiveness by building a barrier against tumor diffusion.

Tumour-stroma interactions in carcinogenesis: basic aspects and perspectives

In contrast to the conventional notion regarding tumour development as a cell autonomous process in which the major participants were the cancer cells, increasing evidence attributes important role in the stromal components, namely fibroblasts, and view the tumour as a heterogenous mixture of different cell types. These different types of cells, being cancer cells, fibroblasts, endothelial cells, and others, interact reciprocally and play an almost equally important role in the manifestation of certain aspects of the malignant phenotype. The elucidation of the mechanistic base of such interactions, besides the contribution to understand fundamental aspects of tumour cell biology, promises important applications in diagnosis, prognosis and therapy of the disease.

Catalytically inactive human cathepsin D triggers fibroblast invasive growth

The aspartyl-protease cathepsin D (cath-D) is overexpressed and hypersecreted by epithelial breast cancer cells and stimulates their proliferation. As tumor epithelial-fibroblast cell interactions are important events in cancer progression, we investigated whether cath-D overexpression affects also fibroblast behavior. We demonstrate a requirement of cath-D for fibroblast invasive growth using a three-dimensional (3D) coculture assay with cancer cells secreting or not pro-cath-D. Ectopic expression of cath-D in cath-D-deficient fibroblasts stimulates 3D outgrowth that is associated with a significant increase in fibroblast proliferation, survival, motility, and invasive capacity, accompanied by activation of the ras-MAPK pathway. Interestingly, all these stimulatory effects on fibroblasts are independent of cath-D proteolytic activity. Finally, we show that pro-cath-D secreted by cancer cells is captured by fibroblasts and partially mimics effects of transfected cath-D. We conclude that cath-D is crucial for fibroblast invasive outgrowth and could act as a key paracrine communicator between cancer and stromal cells, independently of its catalytic activity.

Reduced metastasis of transgenic mammary cancer in urokinase-deficient mice

A prominent phenotype of plasmin deficiency in mice is reduced metastasis in the MMTV-PymT transgenic breast cancer model. Proteolytically active plasmin is generated from inactive plasminogen by one of 2 activators, uPA or tPA. We now find that uPA deficiency alone significantly reduces metastasis >7-fold in the MMTV-PymT model. We studied a cohort of 55 MMTV-PymT transgenic mice, either uPA-deficient or wild-type controls. Tumor incidence, latency, growth rate and final primary tumor burden were not significantly affected by uPA deficiency. In contrast, average lung metastasis volume was reduced from 1.58 mm(3) in wild-type controls to 0.21 mm(3) in uPA-deficient mice (p = 0.023). Tumor cell dissemination to brachial lymph nodes was also reduced from 53% (28/53) in wild-type controls to 31% (17/54) in uPA-deficient mice (p = 0.032). Mice without plasminogen display a severe pleiotropic phenotype. By comparison, spontaneous phenotypes are modest in uPA-deficient mice, probably because they still have active tPA. We show that metastasis is strongly and selectively decreased in uPA-deficient mice, suggesting that uPA-directed antimetastatic therapy would be efficacious and have limited side effects.

Matrix metalloproteinase 11 depletion inhibits cell proliferation in gastric cancer cells

Our previous study has shown that matrix metalloproteinase 11 (MMP11) is highly expressed in tumor cell lines and primary tumor of gastric cancer (GC). In order to reveal the correlation between expression of MMP11 and biological features of GC cell, we have constructed the recombinant plasmids producing hairpin small interfering RNA (siRNA) to target MMP11 mRNA using a vector-based RNA interference technology. Stable transfection of recombinants into GC cell line BGC823 specifically depleted the mRNA and protein of MMP11 as demonstrated by RT-PCR and Western blotting analysis. The siRNA-treated cells exhibited significantly decreased growth ability compared with mock transfectants and parental BGC823 cells. Furthermore, colony formation of MMP11 deficient cells was dramatically inhibited in soft agar and tumorigenicity was reduced in nude mice, respectively. These results provide new insights into the function of MMP11 and suggest that MMP11 may play an important role in the control of cell proliferation and tumor development in GC.

Anti-invasive, antitumoral, and antiangiogenic efficacy of a pyrimidine-2,4,6-trione derivative, an orally active and selective matrix metalloproteinases inhibitor

PURPOSE

The implication of matrix metalloproteinases (MMPs) in the major stages of cancer progression has fueled interest in the design of synthetic MMP inhibitors (MMPIs) as a novel anticancer therapy. Thus far, drugs used in clinical trials are broad-spectrum MMPIs the therapeutic index of which proved disappointingly low. The development of selective MMPIs for tumor progression-associated MMPs is, thus, likely to offer improved therapeutic possibilities.

EXPERIMENTAL DESIGN

The anti-invasive capacity of a series of pyrimidine-trione derivatives was tested in vitro in a chemoinvasion assay, and the most potent compound was further evaluated in vivo in different human tumor xenograft models. The activity of this novel selective MMPI was compared with BB-94, a broad-spectrum inhibitor.

RESULTS

Ro-28-2653, an inhibitor with high selectivity for MMP-2, MMP-9, and membrane type 1 (MT1)-MMP, showed the highest anti-invasive activity in vitro. In vivo, Ro-28-2653 reduced the growth of tumors induced by the inoculation of different cell lines producing MMPs and inhibited the tumor-promoting effect of fibroblasts on breast adenocarcinoma cells. Furthermore, Ro-28-2653 reduced tumor vascularization and blocked angiogenesis in a rat aortic ring assay. In contrast, BB-94 up-regulated MMP-9 expression in tumor cells and promoted angiogenesis in the aortic ring assay.

CONCLUSION

Ro-28-2653, a selective and orally bioavailable MMPI with inhibitory activity against MMPs expressed by tumor and/or stromal cells, is a potent antitumor and antiangiogenic agent. In contrast to broad-spectrum inhibitors, the administration of Ro-28-2653 was not associated with the occurrence of adverse side effects that might hamper the therapeutic potential of these drugs.

Tumour-stroma interaction: cancer-associated fibroblasts as novel targets in anti-cancer therapy?

Stroma cells, together with extracellular matrix components, provide the microenvironment that is pivotal for cancer cell growth, invasion and metastatic progression. Characteristic stroma alterations accompany or even precede the malignant conversion of epithelial cells. Crucial in this process are fibroblasts, also termed myofibroblasts or cancer-associated fibroblasts (CAFs) that are located in the vicinity of the neoplastic epithelial cells. They are able to modify the phenotype of the epithelial cells by direct cell-to-cell contacts, through soluble factors or by modification of extracellular matrix components. Seminal functional studies in various cancer types, including breast, colon, prostate and lung cancer, have confirmed the concept that fibroblasts can determine the fate of the epithelial cell, since they are able to promote malignant conversion as well as to revert tumour cells to a normal phenotype. This review focuses on characteristic changes of fibroblasts in cancer and provides the experimental background elucidating functional properties of CAFs in the carcinogenic process. A possible implication in lung carcinogenesis is emphasised. Finally, a laser-capture- and microarray-based approach is presented, which comprehensively characterises carcinoma-associated fibroblasts in their in vivo environment for the identification of potential targets for anti-cancer therapy.

Prognostic Significance of Stromelysin-3 and Tissue Inhibitor of Matrix Metalloproteinase-2 in Esophageal Cancer

OBJECTIVE

Stromelysins (matrix metalloproteinases: MMP-10 or ST-2 and MMP-11 or ST-3) and tissue inhibitors of matrix metalloproteinases (TIMP-1 and 2) have been shown to be associated with human tumor progression, invasion and metastasis. The aim of the present study was to determine the prognostic significance of these proteins in esophageal squamous cell carcinoma (ESCC).

METHODS

Immunohistochemical analysis was carried out in 65 surgically resected ESCCs and 49 distant histologically normal esophageal tissues and 16 cases of dysplasias. Statistical analyses were performed to determine the associations between the protein expression and clinicopathological parameters and survival of esophageal cancer patients.

RESULTS

Expression of ST-2, ST-3, TIMP-1 and TIMP-2 was observed in 43/65 (66%), 51/65 (78%), 43/65 (66%) and 47/65 (72%) ESCC cases, respectively. Univariate analysis showed that TIMP-2 expression was associated with tumor site (OR = 2.63, p = 0.017). TIMP-1+/TIMP-2+ phenotype was inversely correlated with nodal invasiveness of the tumor (OR = 0.4, p = 0.04). Interestingly, p53 expression was associated with increased levels of ST-3 (OR = 0.11, p = 0.02) and TIMP-1 (OR = 3.2, p = 0.007) suggesting possible involvement of p53 in the regulation of these proteins. An increased expression of ST-2, ST-3, TIMP-1 and TIMP-2 was observed in 11/16 (69%), 7/17 (44%), 11/16 (69%) and 8/16 (50%) dysplasias also suggesting that these alterations are early events in esophageal tumorigenesis. All the ESCC patients were followed up postesophagectomy for a maximum period of 59 months (mean disease-free survival = 12 months). Kaplan-Meier survival analysis showed that patients with ST-3-positive and TIMP-2-negative carcinoma had a significantly shorter disease-free survival (median disease-free survival time of 4 months) as compared to patients in the other groups (median disease-free survival time of 20 months; p = 0.0016). To our knowledge this is the first report showing that ST-3+/TIMP-2- phenotype remained of significant predictive value for disease-free survival (p = 0.0007) in multivariate analysis including a conventional clinicopathological factor, tumor stage (p = 0.051).

CONCLUSION

Our results suggest that ST-3+/TIMP-2- phenotype is an adverse prognosticator in esophageal cancer patients.

Friends or foes - bipolar effects of the tumour stroma in cancer

The restricted view of tumour progression as a multistep process defined by the accumulation of mutations in cancer cells has largely ignored the substantial contribution of the tumour microenvironment to malignancy. Even though the seed and soil hypothesis of Paget dates to 1889, it has been less than two decades since researchers have included the tumour microenvironment in their analyses of tumour progression. What have we recently learned from studying tumour-stroma interactions, and will this help to define new targets for therapy?

Tumor cell-mediated induction of the stromal factor stromelysin-3 requires heterotypic cell contact-dependent activation of specific protein kinase C isoforms

Stromelysin-3 (ST3, MMP-11) has been shown to be strongly overexpressed in stromal fibroblasts of most invasive human carcinomas. However, the molecular mechanisms leading to ST3 expression in nonmalignant fibroblasts remain unknown. The aim of the present study was to analyze the signaling pathways activated in normal pulmonary fibroblasts after their interaction with non-small cell lung cancer (NSCLC) cells and leading to ST3 expression. The use of selective signaling pathway inhibitors showed that conventional and novel protein kinase Cs (PKC) were required for ST3 induction, whereas Src kinases exerted a negative control. We observed by both conventional and real time confocal microscopy that green fluorescent protein-tagged PKCalpha and PKCepsilon, but not PKCdelta, transfected in fibroblasts, accumulate selectively at the cell-cell contacts between fibroblasts and tumor cells. In agreement, RNAi-mediated depletion of PKCalpha and PKCepsilon, but not PKCdelta significantly decreased co-culture-dependent ST3 production. Finally, a tetracycline-inducible expression model allowed us to confirm the central role of these PKC isoforms and the negative regulatory function of c-Src in the control of ST3 expression. Altogether, our data emphasize signaling changes occurring in the tumor microenvironment that may define new stromal targets for therapeutic intervention.

Characterization of and osteoarthritis susceptibility in ADAMTS-4-knockout mice

OBJECTIVE

To determine the importance of the enzymatic activity of ADAMTS-4 in normal growth and development and to evaluate the role of ADAMTS-4 in the progression of osteoarthritis (OA).

METHODS

We generated catalytic domain-deleted ADAMTS-4-transgenic mice and performed extensive gross and histologic analyses of various organs. The mice were challenged by surgical induction of joint instability leading to OA, to determine the importance of the enzymatic activity of ADAMTS-4 in the progression of the disease. The response of wild-type (WT) and ADAMTS-4-knockout (ADAMTS-4-KO) articular cartilage to interleukin-1 and retinoic acid challenge in vitro was also evaluated.

RESULTS

ADAMTS-4-KO mice up to 1 year of age exhibited no gross or histologic abnormalities in 36 tissue sites examined. Despite evidence of ADAMTS-4 expression and activity in growth plates of WT mice, catalytic silencing of this proteinase caused no abnormalities in skeletal development, growth, or remodeling. There was no effect of ADAMTS-4 knockout on the progression or severity of OA 4 weeks or 8 weeks after surgical induction of joint instability. Enzymatic cleavage of aggrecan at the TEGE(373-374)ARGS site was clearly evident after exposure of articular cartilage from ADAMTS-4-KO mice to inflammatory cytokines.

CONCLUSION

Although expression of the ADAMTS-4 gene has been found in many tissues throughout the body, deletion of enzymatic activity did not appear to have any effect on normal growth and physiology. Our study provides evidence that ADAMTS-4 is the primary aggrecanase in murine growth plates; however, deletion of its enzymatic activity did not affect normal long bone remodeling. Our results also lead to the hypothesis that, in the mouse, ADAMTS-4 is not the primary enzyme responsible for aggrecan degradation at the TEGE(373-374)ARGS site. The elucidation of the relative importance of ADAMTS-4 in the pathologic process of human OA will require examination of human OA tissues and evidence of disease modification in patients following therapeutic intervention.

Matrix metalloproteinases and their tissue inhibitors in the developing neonatal mouse uterus

Postnatal development of the mouse uterus involves differentiation and development of the endometrial glands as well as the myometrium. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in extracellular matrix breakdown and morphogenesis of many epitheliomesenchymal organs. As a first step to understanding their roles in postnatal mouse uterine development, MMPs and TIMPs found to be expressed in the neonatal mouse uterus by microarray analysis were localized by in situ hybridization. The MMP-2 mRNA was detected only in the uterine stroma, whereas the MMP-10 mRNA was present only in the uterine epithelium from Postnatal Day (PND) 3 to PND 9. All other MMPs (MMP-11, MMP-14, and MMP-23) as well as TIMP-1, TIMP-2, and TIMP-3 were detected in both epithelial and stromal cells of the endometrium, but not in the myometrium. Uterine extracts were then analyzed by gelatin and casein gel zymography to detect active gelatinases and stromelysins, respectively. Five major gelatinase bands of activity were detected and inhibited by the MMP inhibitors, EDTA or 1,10-phenanthroline, but not by PMSF, a serine protease inhibitor. Western blot analysis confirmed the presence of MMP-2 and MMP-9 proteins in the uterus. Immunoreactive MMP-9 protein was detected only in the endometrial stroma, whereas immunoreactive MMP-2 protein was detected in both the stroma and epithelium of the uterus. Casein zymography detected three major bands of activity ( approximately 54, 63, and 80 kDa) that were inhibited by the serine protease inhibitor, PMSF, but not by the MMP inhibitors, EDTA or 1,10-phenanthroline, suggesting that they were serine proteases. These results support the hypothesis that MMPs and TIMPs regulate postnatal development of the mouse uterus.

Membrane associated proteases and their inhibitors in tumour angiogenesis

Cell surface proteolysis is an important mechanism for generating biologically active proteins that mediate a range of cellular functions and contribute to biological processes such as angiogenesis. Although most studies have focused on the plasminogen system and matrix metalloproteinases (MMPs), recently there has been an increase in the identification of membrane associated proteases, including serine proteases, ADAMs, and membrane-type MMPs (MT-MMPs). Normally, protease activity is tightly controlled by tissue inhibitors of MMPs (TIMPs) and plasminogen activator inhibitors (PAIs). The balance between active proteases and inhibitors is thought to determine the occurrence of proteolysis in vivo. High concentrations of proteolytic system components correlate with poor prognosis in many cancers. Paradoxically, high (not low) PAI-1 or TIMP concentrations predict poor survival in patients with various cancers. Recent observations indicate a much more complex role for protease inhibitors in tumour progression and angiogenesis than initially expected. As knowledge in the field of protease biology has improved, the unforeseen complexities of cell associated enzymes and their interaction with physiological inhibitors have emerged, often revealing unexpected mechanisms of action.

Breast adenocarcinoma liver metastases, in contrast to colorectal cancer liver metastases, display a non-angiogenic growth pattern that preserves the stroma and lacks hypoxia

Although angiogenesis is a prerequisite for the growth of most human solid tumours, alternative mechanisms of vascularisation can be adopted. We have previously described a non-angiogenic growth pattern in liver metastases of colorectal adenocarcinomas (CRC) in which tumour cells replace hepatocytes at the tumour–liver interface, preserving the liver architecture and co-opting the sinusoidal blood vessels. The aim of this study was to determine whether this replacement pattern occurs during liver metastasis of breast adenocarcinomas (BC) and whether the lack of an angiogenic switch in such metastases is due to the absence of hypoxia and subsequent vascular fibrinogen leakage. The growth pattern of 45 BC liver metastases and 28 CRC liver metastases (73 consecutive patients) was assessed on haematoxylin- and eosin-stained tissue sections. The majority of the BC liver metastases had a replacement growth pattern (96%), in contrast to only 32% of the CRC metastases (P<0.0001). The median carbonic anhydrase 9 (CA9) expression (M75 antibody), as a marker of hypoxia, (intensity × % of stained tumour cells) was 0 in the BC metastases and 53 in the CRC metastases (P<0.0001). There was CA9 expression at the tumour–liver interface in only 16% of the BC liver metastases vs 54% of the CRC metastases (P=0.002). There was fibrin (T2G1 antibody) at the tumour-liver interface in only 21% of the BC metastases vs 56% of the CRC metastases (P=0.04). The median macrophage count (Chalkley morphometry; KP-1 anti-CD68 antibody) at the interface was 4.3 and 7.5, respectively (P<0.0001). Carbonic anhydrase 9 score and macrophage count were positively correlated (r=0.42; P=0.002) in all metastases. Glandular differentiation was less in the BC liver metastases: 80% had less than 10% gland formation vs only 7% of the CRC metastases (P<0.0001). The liver is a densely vascularised organ and can host metastases that exploit this environment by replacing the hepatocytes and co-opting the vasculature. Our findings confirm that a non-angiogenic pattern of liver metastasis indeed occurs in BC, that this pattern of replacement growth is even more prevalent than in CRC, and that the process induces neither hypoxia nor vascular leakage.

Pro-matrix metalloproteinase-2 transfection increases orthotopic primary growth and experimental metastasis of MDA-MB-231 human breast cancer cells in nude mice

The ability to activate pro-matrix metalloproteinase (pro-MMP)-2 via membrane type-MMP is a hallmark of human breast cancer cell lines that show increased invasiveness, suggesting that MMP-2 contributes to human breast cancer progression. To investigate this, we have stably transfected pro-MMP-2 into the human breast cancer cell line MDA-MB-231, which lacks MMP-2 expression but does express its cell surface activator, membrane type 1-MMP. Multiple clones were derived and shown to produce pro-MMP-2 and to activate it in response to concanavalin A. In vitro analysis showed that the pro-MMP-2-transfected clones exhibited an increased invasive potential in Boyden chamber and Matrigel outgrowth assays, compared with the parental cells or those transfected with vector only. When inoculated into the mammary fat pad of nude mice, each of the MMP-2-tranfected clones grew faster than each of the vector controls tested. After intracardiac inoculation into nude mice, pro-MMP-2-transfected clones showed a significant increase in the incidence of metastasis to brain, liver, bone, and kidney compared with the vector control clones but not lung. Increased tumor burden was seen in the primary site and in lung metastases, and a trend toward increased burden was seen in bone, however, no change was seen in brain, liver, or kidney. This data supports a role for MMP-2 in breast cancer progression, both in the growth of primary tumors and in their spread to distant organs. MMP-2 may be a useful target for breast cancer therapy when refinement of MMP inhibitors provides for MMP-specific agents.

MT1‐MMP: A tethered collagenase

Gene ablation in mice offers a powerful tool to assay in vivo the role of selected molecules. Numerous new mouse models of matrix metalloproteinases (MMP) deficiency have been developed in the past 5 years and have yielded a new understanding of the role of MMPs while also putting to rest assumptions based on data predating the days of mouse models. The phenotype of the MT1-MMP deficient mouse is one example which illustrates the sometimes rather surprising insights into extracellular matrix remodeling in development and growth that can be gained with mouse genetics. While MT1-MMP appears to play little or no role in embryonic development, loss of this enzyme results in progressive impairment of postnatal growth and development affecting both the skeleton and the soft connective tissues. The underlying pathologic mechanism is loss of an indispensable collagenolytic activity, which remains essentially uncompensated. Our findings demonstrate that growth and maintenance of the skeleton requires coordinated and simultaneous MT1-MMP-dependent remodeling of all soft tissue attachments (ligaments, tendons, joint capsules). We note that the phenotype of the MT1-MMP deficient mouse bears no resemblance to those of mice deficient in MMP-2 and tissue inhibitors of metallo-proteinase (TIMP)-2 all but dispelling the view that activation of MMP-2 by the MT1-MMP/TIMP-2/proMMP-2 axis plays a significant role in growth and development throughout life. It is of interest to note that loss of a single catabolic function such as selective collagen degradation mediated by MT1-MMP gives rise to profound impairment of a number of both anabolic and catabolic functions.