The second dimer interface of MT1-MMP, the transmembrane domain, is essential for ProMMP-2 activation on the cell surface

MMP-14 Exhibits Greater Expression, Content and Activity Compared to MMP-15 in Human Renal Carcinoma

Membrane-type metalloproteinases (including MMP-14 and MMP-15) are enzymes involved in the degradation of extracellular matrix components. In cancer, they are involved in processes such as cellular invasion, angiogenesis and metastasis. Therefore, the aim of this study was to evaluate the expression, content and activity of MMP-14 and MMP-15 in human renal cell carcinoma. Samples of healthy kidney tissue (n = 20) and tissue from clear-cell kidney cancer (n = 20) were examined. The presence and contents of the MMPs were assessed using Western blot and ELISA techniques, respectively. Their activity-both actual and specific-was evaluated using fluorimetric analysis. Both control and cancer human kidney tissues contain MMP-14 and MMP-15 enzymes in the form of high-molecular-weight complexes. Moreover, these enzymes occur in both active and latent forms. Their content in cancer tissues is very similar, but with a noteworthy decrease in content with an increase in the kidney cancer grade for both membrane-type metalloproteinases. Even more notable is the highest content of the investigated enzymes represented by MMP-14 in the control tissues. Considering the actual and specific activity outcomes, MMP-14 dominates over MMP-15 in all of the investigated tissues. Nevertheless, we also noted a significant enhancement of the activity of both metalloproteinases with an increase in the grade of renal cancer. The expression and activity of both enzymes were detected in all examined renal cancer tissues. However, our findings suggest that transmembrane metalloproteinase 14 (MMP-14) plays a much more significant and essential role than MMP-15 in the studied renal carcinoma tissues. Therefore, it seems that MMP-14 could be a promising target in the diagnosis, prognosis and therapy of renal cell carcinoma.

Matrix metalloproteinases and tissue inhibitors in multiple myeloma: promote or inhibit?

Matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) play a vital role in the pathogenesis of multiple myeloma (MM), especially for tumor invasion and osteolytic osteopathy. By breaking down extracellular matrix (ECM) components and releasing the proteins composing the ECM and growth factors, as well as their receptors, MMPs affect tissue integrity and promote cancer cell invasion and metastasis. A vital pathophysiological characteristic of MM is the progress of osteolytic lesions, which are brought on by interactions between myeloma cells and the bone marrow microenvironment. MMPs, certainly, are one of the fundamental causes of myeloma bone disease due to their ability to degrade various types of collagens. TIMPs, as important regulators of MMP hydrolysis or activation, also participate in the occurrence and evolution of MM and the formation of bone disease. This review focuses on the role of MMP-1, MMP-2, MMP-7, MMP-9, MMP-13, MMP-14, and MMP-15 and the four types of TIMPs in the invasion of myeloma cells, angiogenesis, osteolytic osteopathy, to offer some novel perspectives on the clinical diagnostics and therapeutics of MM.

Cytoplasmic Tail of MT1-MMP: A Hub of MT1-MMP Regulation and Function

MT1-MMP (MMP-14) is a multifunctional protease that regulates ECM degradation, activation of other proteases, and a variety of cellular processes, including migration and viability in physiological and pathological contexts. Both the localization and signal transduction capabilities of MT1-MMP are dependent on its cytoplasmic domain that constitutes the final 20 C-terminal amino acids, while the rest of the protease is extracellular. In this review, we summarize the ways in which the cytoplasmic tail is involved in regulating and enacting the functions of MT1-MMP. We also provide an overview of known interactors of the MT1-MMP cytoplasmic tail and the functional significance of these interactions, as well as further insight into the mechanisms of cellular adhesion and invasion that are regulated by the cytoplasmic tail.

Proteolytic modulation of tumor microenvironment signals during cancer progression

Under normal conditions, the cellular microenvironment is optimized for the proper functioning of the tissues and organs. Cells recognize and communicate with the surrounding cells and extracellular matrix to maintain homeostasis. When cancer arises, the cellular microenvironment is modified to optimize its malignant growth, evading the host immune system and finding ways to invade and metastasize to other organs. One means is a proteolytic modification of the microenvironment and the signaling molecules. It is now well accepted that cancer progression relies on not only the performance of cancer cells but also the surrounding microenvironment. This mini-review discusses the current understanding of the proteolytic modification of the microenvironment signals during cancer progression.

The Catalytic Domain Mediates Homomultimerization of MT1-MMP and the Prodomain Interferes with MT1-MMP Oligomeric Complex Assembly

Homomultimerization of MT1-MMP (membrane type 1 matrix metalloproteinase) through the hemopexin, transmembrane, and cytoplasmic domains plays a very important role in the activation of proMMP-2 and the degradation of pericellular collagen. MT1-MMP is overexpressed in many types of cancers, and it is considered to be a key enzyme in facilitating cancer cell migration. Since the oligomerization of MT1-MMP is important for its proteolytic activity in promoting cancer invasion, we have further investigated the multimerization by using heterologously expressed MT1-MMP ectodomains in insect cells to gain additional mechanistic insight into this process. We show that the whole ectodomain of MT1-MMP can form dimers and higher-order oligomeric complexes. The enzyme is secreted in its active form and the multimeric complex assembly is mediated by the catalytic domain. Blocking the prodomain removal determines the enzyme to adopt the monomeric structure, suggesting that the prodomain prevents the MT1-MMP oligomerization process. The binding affinity of MT1-MMP to type I collagen is dependent on the oligomeric state. Thus, the monomers have the weakest affinity, while the binding strength increases proportionally with the complexity of the multimers. Collectively, our experimental results indicate that the catalytic domain of MT1-MMP is necessary and sufficient to mediate the formation of multimeric structures.

The Development of Peritoneal Metastasis from Gastric Cancer and Rationale of Treatment According to the Mechanism

In the present article, we describe the normal structure of the peritoneum and review the mechanisms of peritoneal metastasis (PM) from gastric cancer (GC). The structure of the peritoneum was studied by a double-enzyme staining method using alkaline-phosphatase and 5′-nucreotidase, scanning electron microscopy, and immunohistological methods. The fundamental structure consists of three layers, mesothelial cells and a basement membrane (layer 1), macula cribriformis (MC) (layer 2), and submesothelial connective tissue containing blood vessels and initial lymphatic vessels, attached to holes in the MC (layer 3). Macro molecules and macrophages migrate from mesothelial stomata to the initial lymphatic vessels through holes in the MC. These structures are characteristically found in the diaphragm, omentum, paracolic gutter, pelvic peritoneum, and falciform ligament. The first step of PM is spillage of cancer cells (peritoneal free cancer cells; PFCCs) into the peritoneal cavity from the serosal surface of the primary tumor or cancer cell contamination from lymphatic and blood vessels torn during surgical procedures. After PFCCs adhere to the peritoneal surface, PMs form by three processes, i.e., (1) trans-mesothelial metastasis, (2) trans-lymphatic metastasis, and (3) superficial growing metastasis. Because the intraperitoneal (IP) dose intensity is significantly higher when generated by IP chemotherapy than by systemic chemotherapy, IP chemotherapy has a great role in the treatment of PFCCs, superficial growing metastasis, trans-lymphatic metastasis and in the early stages of trans-mesothelial metastasis. However, an established trans-mesothelial metastasis has its own interstitial tissue and vasculature which generate high interstitial pressure. Accordingly, it is reasonable to treat established trans-mesothelial metastasis by bidirectional chemotherapy from both IP and systemic chemotherapy.

MT2-MMP is differentially expressed in multiple myeloma cells and mediates their growth and progression

OBJECTIVE

Membrane type-matrix metalloproteinases (MT-MMPs) are known as key regulators of cancer progression/metastasis. However, their roles in the growth and progression of multiple myeloma (MM) have not been yet elucidated.

METHODS AND MATERIALS

The expression of 6 MT-MMPs in MM, B cell lines, and normal peripheral blood (PB) cells were measured by RT-PCR, qRT-PCR, flow cytometry, western blotting, and immunocytochemistry. B lymphocytes, CD19^-/CD138^-, and CD19^-/CD138⁺ cells, known as malignant plasma cells (MPC), were sorted from bone marrow (BM) aspirations of 10 MM patients, and MT2-MMP expression was examined in these cells using qRT-PCR, flow cytometry and immunohistochemistry, and western blotting. Moreover, the expression of MT2-MMP in BM biopsies from 13 normal individuals and 14 MM patients was analyzed by immunohistochemistry. MT2-MMP was also knocked down in U266 cells using siRNA technology and the adhesion, invasion, migration abilities, and cell proliferation were determined and compared with scrambled ones in both in vitro and in vivo studies.

RESULTS

Our results showed that MT2-MMP expression is significantly higher in MM cell lines and MPC cells than B cell lines and other PB- or BM-derived cells. MT2-MMP is expressed in BM biopsies from all 14 patients with MM, and 67.85% ± 32.38 of BM cells were positive for MT2-MMP. In contrast, only 0.38 ± 0.76 of BM biopsies from normal individuals were positive for MT2-MMP. Importantly, MT2-MMP was expressed in all the patients' BM biopsies at the diagnosis, but not in the remission phase. MT2-MMP siRNA significantly decreased adhesion, invasion, migration, and 3D cell proliferation of U266 cells. Moreover, in the xenographic model, MT2-MMP siRNA prevented the growth and development of plasmacytoma. Taken together, these data demonstrate that MT2-MMP is strongly expressed in MM cells and plays important role in the growth and progression of these cells, suggesting that MT2-MMP is an appropriate biomarker in diagnosis and therapeutic interventions of MM.

Matrix Metalloproteinases Shape the Tumor Microenvironment in Cancer Progression

Cancer progression with uncontrolled tumor growth, local invasion, and metastasis depends largely on the proteolytic activity of numerous matrix metalloproteinases (MMPs), which affect tissue integrity, immune cell recruitment, and tissue turnover by degrading extracellular matrix (ECM) components and by releasing matrikines, cell surface-bound cytokines, growth factors, or their receptors. Among the MMPs, MMP-14 is the driving force behind extracellular matrix and tissue destruction during cancer invasion and metastasis. MMP-14 also influences both intercellular as well as cell-matrix communication by regulating the activity of many plasma membrane-anchored and extracellular proteins. Cancer cells and other cells of the tumor stroma, embedded in a common extracellular matrix, interact with their matrix by means of various adhesive structures, of which particularly invadopodia are capable to remodel the matrix through spatially and temporally finely tuned proteolysis. As a deeper understanding of the underlying functional mechanisms is beneficial for the development of new prognostic and predictive markers and for targeted therapies, this review examined the current knowledge of the interplay of the various MMPs in the cancer context on the protein, subcellular, and cellular level with a focus on MMP14.

The role of MMP-14 in ovarian cancer: a systematic review

AIM

In order to evaluate the role of MMP-14 in ovarian cancer, a systematic review was conducted.

METHODS

In March 2020, a search in Pubmed was performed with MMP-14 and ovarian cancer as search terms. After exclusion of the references not on MMP-14 or ovarian cancer or not in English, the studies found were classified into two categories: basic research and clinicopathological research.

RESULTS

In total, 94 references were found of which 33 were excluded. Two additional articles were found in the reference lists of the included studies. Based on the full texts, another 4 were excluded. Eventually, 59 studies were included in the review, 32 on basic research and 19 on clinicopathological research. 8 studies fell in both categories. The basic research studies show that MMP-14 plays an important role in ovarian cancer in the processes of proliferation, invasion, angiogenesis and metastasis. In clinocopathological research, MMP-14 expression is found in most tumours with characteristics of poor prognosis but this immunohistochemical MMP-14 determination does not seem to be an independent predictor of prognosis.

CONCLUSIONS

From this systematic review of the literature concerning MMP-14 in ovarian cancer it becomes clear that MMP-14 plays various important roles in the pathophysiology of ovarian cancer. The exact translation of these roles in the pathophysiology to the importance of MMP-14 in clinicopathological research in ovarian cancer and possible therapeutic role of anti-MMP-14 agents needs further elucidation.

A common SNP risk variant MT1-MMP causative for Dupuytren's disease has a specific defect in collagenolytic activity

Dupuytren's Disease (DD) is a common fibroproliferative disease of the palmar fascia. We previously identified a causal association with a non-synonymous variant (rs1042704, p.D273N) in MMP14 (encoding MT1-MMP). In this study, we investigated the functional consequences of this variant, and demonstrated that the variant MT1-MMP (MT1-N273) exhibits only 17% of cell surface collagenolytic activity compared to the ancestral enzyme (MT1-D273). Cells expressing both MT1-D273 and MT1-N273 in a 1:1 ratio, mimicking the heterozygous state, possess 38% of the collagenolytic activity compared to the cells expressing MT1-D273, suggesting that MT1-N273 acts in a dominant negative manner. Consistent with the above observation, patient-derived DD myofibroblasts with the alternate allele demonstrated around 30% of full collagenolytic activity detected in ancestral G/G genotype cells, regardless of the heterozygous (G/A) or homozygous (A/A) state. Small angle X-ray scattering analysis of purified soluble Fc-fusion enzymes allowed us to construct a 3D-molecular envelope of MT1-D273 and MT1-N273, and demonstrate altered flexibility and conformation of the ectodomains due to D273 to N substitution. Taking together, rs1042704 significantly reduces collagen catabolism in tissue, which tips the balance of homeostasis of collagen in tissue, contributing to the fibrotic phenotype of DD. Since around 30% of the worldwide population have at least one copy of the low collagenolytic alternate allele, further investigation of rs1042704 across multiple pathologies is needed.

Strategies to Target ADAM17 in Disease: From its Discovery to the iRhom Revolution

For decades, disintegrin and metalloproteinase 17 (ADAM17) has been the object of deep investigation. Since its discovery as the tumor necrosis factor convertase, it has been considered a major drug target, especially in the context of inflammatory diseases and cancer. Nevertheless, the development of drugs targeting ADAM17 has been harder than expected. This has generally been due to its multifunctionality, with over 80 different transmembrane proteins other than tumor necrosis factor α (TNF) being released by ADAM17, and its structural similarity to other metalloproteinases. This review provides an overview of the different roles of ADAM17 in disease and the effects of its ablation in a number of in vivo models of pathological conditions. Furthermore, here, we comprehensively encompass the approaches that have been developed to accomplish ADAM17 selective inhibition, from the newest non-zinc-binding ADAM17 synthetic inhibitors to the exploitation of iRhom2 to specifically target ADAM17 in immune cells.

Regulation of MT1-MMP Activity through Its Association with ERMs

Membrane-bound proteases play a key role in biology by degrading matrix proteins or shedding adhesion receptors. MT1-MMP metalloproteinase is critical during cancer invasion, angiogenesis, and development. MT1-MMP activity is strictly regulated by internalization, recycling, autoprocessing but also through its incorporation into tetraspanin-enriched microdomains (TEMs), into invadopodia, or by its secretion on extracellular vesicles (EVs). We identified a juxtamembrane positively charged cluster responsible for the interaction of MT1-MMP with ERM (ezrin/radixin/moesin) cytoskeletal connectors in breast carcinoma cells. Linkage to ERMs regulates MT1-MMP subcellular distribution and internalization, but not its incorporation into extracellular vesicles. MT1-MMP association to ERMs and insertion into TEMs are independent phenomena, so that mutation of the ERM-binding motif in the cytoplasmic region of MT1-MMP does not preclude its association with the tetraspanin CD151, but impairs the accumulation and coalescence of CD151/MT1-MMP complexes at actin-rich structures. Conversely, gene deletion of CD151 does not impact on MT1-MMP colocalization with ERM molecules. At the plasma membrane MT1-MMP autoprocessing is severely dependent on ERM association and seems to be the dominant regulator of the enzyme collagenolytic activity. This newly characterized MT1-MMP/ERM association can thus be of relevance for tumor cell invasion.

Multicentric osteolytic syndromes represent a phenotypic spectrum defined by defective collagen remodeling

Frank-Ter Haar syndrome (FTHS), Winchester syndrome (WS), and multicentric osteolysis, nodulosis, and arthropathy (MONA) are ultra-rare multisystem disorders characterized by craniofacial malformations, reduced bone density, skeletal and cardiac anomalies, and dermal fibrosis. These autosomal recessive syndromes are caused by homozygous mutation or deletion of respectively SH3PXD2B (SH3 and PX Domains 2B), MMP14 (matrix metalloproteinase 14), or MMP2. Here, we give an overview of the clinical features of 63 previously reported patients with an SH3PXD2B, MMP14, or MMP2 mutation, demonstrating considerable clinical overlap between FTHS, WS, and MONA. Interestingly, the protein products of SH3PXD2B, MMP14, and MMP2 directly cooperate in collagen remodeling. We review animal models for these three disorders that accurately reflect the major clinical features and likewise show significant phenotypical similarity with each other. Furthermore, they demonstrate that defective collagen remodeling is central in the underlying pathology. As such, we propose a nosological revision, placing these SH3PXD2B, MMP14, and MMP2 related syndromes in a novel "defective collagen-remodelling spectrum (DECORS)". In our opinion, this revised nosology better reflects the central role for impaired collagen remodeling, a potential target for pharmaceutical intervention.

MT1-MMP-dependent cell migration: proteolytic and non-proteolytic mechanisms

Membrane-type 1 matrix metalloproteinase (MT1-MMP) is a type I transmembrane proteinase that belongs to the matrix metalloproteinase (MMP) family. It is a potent modifier of cellular microenvironment and promotes cell migration and invasion of a wide variety of cell types both in physiological and pathological conditions. It promotes cell migration by degrading extracellular matrix on the cell surface and creates a migration path, by modifying cell adhesion property by shedding cell adhesion molecules to increase cell motility, and by altering cellular metabolism. Thus, MT1-MMP is a multifunctional cell motility enhancer. In this review, we will discuss the current understanding of the proteolytic and non-proteolytic mechanism of MT1-MMP-dependent cell migration.

Design, synthesis and biological evaluation of bifunctional inhibitors of membrane type 1 matrix metalloproteinase (MT1-MMP)

Collagen degradation and proMMP-2 activation are major functions of MT1-MMP to promote cancer cell invasion. Since both processes require MT1-MMP homodimerization on the cell surface, herein we propose that the use of bifunctional inhibitors of this enzyme could represent an innovative approach to efficiently reduce tumor growth. A small series of symmetrical dimers derived from previously described monomeric arylsulfonamide hydroxamates was synthesized and tested in vitro on isolated MMPs. A nanomolar MT1-MMP inhibitor, compound 6, was identified and then submitted to cell-based assays on HT1080 fibrosarcoma cells. Dimer 6 reduced MT1-MMP-dependent proMMP-2 activation, collagen degradation and collagen invasion in a dose-dependent manner with better results even compared to its monomeric analogue 4. This preliminary study suggests that dimeric MT1-MMP inhibitors might be further developed and exploited as an alternative tool to reduce cancer cell invasion.

MT1-MMP Binds Membranes by Opposite Tips of Its β Propeller to Position It for Pericellular Proteolysis

Critical to migration of tumor cells and endothelial cells is the proteolytic attack of membrane type 1 matrix metalloproteinase (MT1-MMP) upon collagen, growth factors, and receptors at cell surfaces. Lipid bilayer interactions of the substrate-binding hemopexin-like (HPX) domain of MT1-MMP were investigated by paramagnetic nuclear magnetic resonance relaxation enhancements (PREs), fluorescence, and mutagenesis. The HPX domain binds bilayers by blades II and IV on opposite sides of its β propeller fold. The EPGYPK sequence protruding from both blades inserts among phospholipid head groups in PRE-restrained molecular dynamics simulations. Bilayer binding to either blade II or IV exposes the CD44 binding site in blade I. Bilayer association with blade IV allows the collagen triple helix to bind without obstruction. Indeed, vesicles enhance proteolysis of collagen triple-helical substrates by the ectodomain of MT1-MMP. Hypothesized side-by-side MT1-MMP homodimerization would allow binding of bilayers, collagen, CD44, and head-to-tail oligomerization.

Development of a specific affinity-matured exosite inhibitor to MT1-MMP that efficiently inhibits tumor cell invasion in vitro and metastasis in vivo

The membrane-associated matrix metalloproteinase-14, MT1-MMP, has been implicated in pericellular proteolysis with an important role in cellular invasion of collagenous tissues. It is substantially upregulated in various cancers and rheumatoid arthritis, and has been considered as a potential therapeutic target. Here, we report the identification of antibody fragments to MT1-MMP that potently and specifically inhibit its cell surface functions. Lead antibody clones displayed inhibitory activity towards pro-MMP-2 activation, collagen-film degradation and gelatin-film degradation, and were shown to bind to the MT1-MMP catalytic domain outside the active site cleft, inhibiting binding to triple helical collagen. Affinity maturation using CDR3 randomization created a second generation of antibody fragments with dissociation constants down to 0.11 nM, corresponding to an improved affinity of 332-fold with the ability to interfere with cell-surface MT1-MMP functions, displaying IC₅₀ values down to 5 nM. Importantly, the new inhibitors were able to inhibit collagen invasion by tumor-cells in vitro and in vivo primary tumor growth and metastasis of MDA-MB-231 cells in a mouse orthotopic xenograft model. Herein is the first demonstration that an inhibitory antibody targeting sites outside the catalytic cleft of MT1-MMP can effectively abrogate its in vivo activity during tumorigenesis and metastasis.

Ensnaring membrane type 1-matrix metalloproteinase (MT1-MMP) with tissue inhibitor of metalloproteinase (TIMP)-2 using the haemopexin domain of the protease as a carrier: a targeted approach in cancer inhibition

Metastatic cancer cells express Membrane Type 1-Matrix Metalloproteinase (MT1-MMP) to degrade the extracellular matrix in order to facilitate migration and proliferation. Tissue Inhibitor of Metalloproteinase (TIMP)-2 is the endogenous inhibitor of the MMP. Here, we describe a novel and highly effective fusion strategy to enhance the delivery of TIMP-2 to MT1-MMP. We can reveal that TIMP-2 fused to the haemopexin +/− transmembrane domains of MT1-MMP (two chimeras named T2^PEX+TM and T2^PEX) are able to interact with MT1-MMP on the cell surface as well as intracellularly. In the case of T2^PEX+TM, there is even a clear sign of MT1-MMP:T2^PEX+TM aggregation by the side of the nucleus to form aggresomes. In vitro, T2^PEX+TM and T2^PEX suppress the gelatinolytic and invasive abilities of cervical carcinoma (HeLa) and HT1080 fibrosarcoma cancer cells significantly better than wild type TIMP-2. In mouse xenograft, we further demonstrate that T2^PEX diminishes cervical carcinoma growth by 85% relative to the control. Collectively, our findings indicate the effectiveness of the fusion strategy as a potential targeted approach in cancer inhibition.

Expression and Purification of a Matrix Metalloprotease Transmembrane Domain in Escherichia coli

Membrane tethered matrix metalloproteases are bound to the plasma membrane by a glycosylphosphatidylinositol-anchor or a transmembrane domain. To date, most studies of membrane-bound matrix metalloprotease have focused on the globular catalytic and protein-protein interaction domains of these enzymes. However, the transmembrane domains have been poorly studied even though they are known to mediate intracellular signaling via interaction with various cellular proteins. The expression and purification of the transmembrane domain of these proteins can be challenging due to their hydrophobic nature. In this chapter we describe the purification of a transmembrane domain for a membrane-bound matrix metalloprotease expressed in E. coli and its initial characterization by NMR spectroscopy.

A Disintegrin and Metalloproteinase with Thrombospondin Motifs-5 (ADAMTS-5) Forms Catalytically Active Oligomers

The metalloproteinase ADAMTS-5 (A disintegrin and metalloproteinase with thrombospondin motifs) degrades aggrecan, a proteoglycan essential for cartilage structure and function. ADAMTS-5 is the major aggrecanase in mouse cartilage, and is also likely to be the major aggrecanase in humans. ADAMTS-5 is a multidomain enzyme, but the function of the C-terminal ancillary domains is poorly understood. We show that mutant ADAMTS-5 lacking the catalytic domain, but with a full suite of ancillary domains inhibits wild type ADAMTS activity, in vitro and in vivo, in a dominant-negative manner. The data suggest that mutant ADAMTS-5 binds to wild type ADAMTS-5; thus we tested the hypothesis that ADAMTS-5 associates to form oligomers. Co-elution, competition, and in situ PLA experiments using full-length and truncated recombinant ADAMTS-5 confirmed that ADAMTS-5 molecules interact, and showed that the catalytic and disintegrin-like domains support these intermolecular interactions. Cross-linking experiments revealed that recombinant ADAMTS-5 formed large, reduction-sensitive oligomers with a nominal molecular mass of ∼ 400 kDa. The oligomers were unimolecular and proteolytically active. ADAMTS-5 truncates comprising the disintegrin and/or catalytic domains were able to competitively block full-length ADAMTS-5-mediated aggrecan cleavage, measured by production of the G1-EGE(373) neoepitope. These results show that ADAMTS-5 oligomerization is required for full aggrecanase activity, and they provide evidence that blocking oligomerization inhibits ADAMTS-5 activity. The data identify the surface provided by the catalytic and disintegrin-like domains of ADAMTS-5 as a legitimate target for the design of aggrecanase inhibitors.

Transient collagen triple helix binding to a key metalloproteinase in invasion and development

Skeletal development and invasion by tumor cells depends on proteolysis of collagen by the pericellular metalloproteinase MT1-MMP. Its hemopexin-like (HPX) domain binds to collagen substrates to facilitate their digestion. Spin labeling and paramagnetic nuclear magnetic resonance (NMR) detection have revealed how the HPX domain docks to collagen I-derived triple helix. Mutations impairing triple-helical peptidase activity corroborate the interface. Saturation transfer difference NMR suggests rotational averaging around the longitudinal axis of the triple-helical peptide. Part of the interface emerges as unique and potentially targetable for selective inhibition. The triple helix crosses the junction of blades I and II at a 45° angle to the symmetry axis of the HPX domain, placing the scissile Gly∼Ile bond near the HPX domain and shifted ∼25 Å from MMP-1 complexes. This raises the question of the MT1-MMP catalytic domain folding over the triple helix during catalysis, a possibility accommodated by the flexibility between domains suggested by atomic force microscopy images.

Ratio of Active Matrix Metalloproteinases and Proenzymes during Growth and Metastasizing of Mouse Lewis Lung Adenocarcinoma

Ratio between proMMP and active MMP was studied in the dynamics of growth of the Lewis lung adenocarcinoma with lung metastasis. It was shown that tumor growth is associated with an increase in the content of proMMP (day 20; terminal stage), but the level of active MMP in tumor tissue did not signifi cantly change. The development of lung metastasis was accompanied by accumulation of active MMP (days 7, 15, and 20) and a decrease in the content of pro-MMP (days 7, and 20) in comparison with the control. In the spleen of these mice (metastasis-free organ), an increase in the levels of proMMP (day 20) and especially active MMP (days 7, 15, and 20) were found. The results suggest that tumor development shifts the proportion between active MMP and proenzymes in the tumor, lungs with metastasis, and spleen without metastasis.

Membrane-type matrix metalloproteinases: Their functions and regulations

Membrane-type matrix metalloproteinases (MT-MMPs) form a subgroup of the matrix metalloproteinase (MMP) family, and there are 6 MT-MMPs in humans. MT-MMPs are further sub-classified into type I transmembrane-type (MT1, -MT2-, MT3- and MT5-MMPs) and glycosylphosphatidylinositol (GPI)-anchored type (MT4- and MT6-MMPs). In either case MT-MMPs are tethered to the plasma membrane, and this cell surface expression provides those enzymes with unique functionalities affecting various cellular behaviours. Among the 6 MT-MMPs, MT1-MMP is the most investigated enzyme and many of its roles and regulations have been revealed to date, but the potential roles and regulatory mechanisms of other MT-MMPs are gradually getting clearer as well. Further investigations of MT-MMPs are likely to reveal novel pathophysiological mechanisms and potential therapeutic strategies for different diseases in the future.

The fundamental role of mechanical properties in the progression of cancer disease and inflammation

The role of mechanical properties in cancer disease and inflammation is still underinvestigated and even ignored in many oncological and immunological reviews. In particular, eight classical hallmarks of cancer have been proposed, but they still ignore the mechanics behind the processes that facilitate cancer progression. To define the malignant transformation of neoplasms and finally reveal the functional pathway that enables cancer cells to promote cancer progression, these classical hallmarks of cancer require the inclusion of specific mechanical properties of cancer cells and their microenvironment such as the extracellular matrix as well as embedded cells such as fibroblasts, macrophages or endothelial cells. Thus, this review will present current cancer research from a biophysical point of view and will therefore focus on novel physical aspects and biophysical methods to investigate the aggressiveness of cancer cells and the process of inflammation. As cancer or immune cells are embedded in a certain microenvironment such as the extracellular matrix, the mechanical properties of this microenvironment cannot be neglected, and alterations of the microenvironment may have an impact on the mechanical properties of the cancer or immune cells. Here, it is highlighted how biophysical approaches, both experimental and theoretical, have an impact on the classical hallmarks of cancer and inflammation. It is even pointed out how these biophysical approaches contribute to the understanding of the regulation of cancer disease and inflammatory responses after tissue injury through physical microenvironmental property sensing mechanisms. The recognized physical signals are transduced into biochemical signaling events that guide cellular responses, such as malignant tumor progression, after the transition of cancer cells from an epithelial to a mesenchymal phenotype or an inflammatory response due to tissue injury. Moreover, cell adaptation to mechanical alterations, in particular the understanding of mechano-coupling and mechano-regulating functions in cell invasion, appears as an important step in cancer progression and inflammatory response to injuries. This may lead to novel insights into cancer disease and inflammatory diseases and will overcome classical views on cancer and inflammation. In addition, this review will discuss how the physics of cancer and inflammation can help to reveal whether cancer cells will invade connective tissue and metastasize or how leukocytes extravasate and migrate through the tissue. In this review, the physical concepts of cancer progression, including the tissue basement membrane a cancer cell is crossing, its invasion and transendothelial migration as well as the basic physical concepts of inflammatory processes and the cellular responses to the mechanical stress of the microenvironment such as external forces and matrix stiffness, are presented and discussed. In conclusion, this review will finally show how physical measurements can improve classical approaches that investigate cancer and inflammatory diseases, and how these physical insights can be integrated into classical tumor biological approaches.

Basal localization of MT1-MMP is essential for epithelial cell morphogenesis in 3D collagen matrix

The membrane-anchored collagenase membrane type 1 matrix metalloprotease (MT1-MMP) has been shown to play an essential role during epithelial tubulogenesis in 3D collagen matrices; however, its regulation during tubulogenesis is not understood. Here, we report that degradation of collagen in polarized epithelial cells is post-translationally regulated by changing the localization of MT1-MMP from the apical to the basal surface. MT1-MMP predominantly localizes at the apical surface in inert polarized epithelial cells, whereas treatment with HGF induced basal localization of MT1-MMP followed by collagen degradation. The basal localization of MT1-MMP requires the ectodomains of the enzyme because deletion of the MT-loop region or the hemopexin domain inhibited basal localization of the enzyme. TGFβ is a well-known inhibitor of tubulogenesis and our data indicate that its mechanism of inhibition is, at least in part, due to inhibition of MT1-MMP localization to the basal surface. Interestingly, however, the effect of TGFβ was found to be bi-phasic: at high doses it effectively inhibited basal localization of MT1-MMP, whereas at lower doses tubulogenesis and basal localization of MT1-MMP was promoted. Taken together, these data indicate that basal localization of MT1-MMP is a key factor promoting the degradation of extracellular matrix by polarized epithelial cells, and that this is an essential part of epithelial morphogenesis in 3D collagen.

MT-LOOP-dependent localization of membrane type I matrix metalloproteinase (MT1-MMP) to the cell adhesion complexes promotes cancer cell invasion

Localization of membrane type I matrix metalloproteinase (MT1-MMP) to the leading edge is thought to be a crucial step during cancer cell invasion. However, its mechanisms and functional impact on cellular invasion have not been clearly defined. In this report, we have identified the MT-LOOP, a loop region in the catalytic domain of MT1-MMP ((163)PYAYIREG(170)), as an essential region for MT1-MMP to promote cellular invasion. Deletion of the MT-LOOP effectively inhibited functions of MT1-MMP on the cell surface, including proMMP-2 activation, degradation of gelatin and collagen films, and cellular invasion into a collagen matrix. This is not due to loss of the catalytic function of MT1-MMP but due to inefficient localization of the enzyme to β1-integrin-rich cell adhesion complexes at the plasma membrane. We also found that an antibody that specifically recognizes the MT-LOOP region of MT1-MMP (LOOPAb) inhibited MT1-MMP functions, fully mimicking the phenotype of the MT-LOOP deletion mutant. We therefore propose that the MT-LOOP region is an interface for molecular interactions that mediate enzyme localization to cell adhesion complexes and regulate MT1-MMP functions. Our findings have revealed a novel mechanism regulating MT1-MMP during cellular invasion and have identified the MT-LOOP as a potential exosite target region to develop selective MT1-MMP inhibitors.

Review: molecular mechanism of microglia stimulated glioblastoma invasion

Glioblastoma multiforme is one of the deadliest human cancers and is characterized by a high degree of microglia and macrophage infiltration. The role of these glioma infiltrating macrophages (GIMs) in disease progression has been the subject of recent investigation. While initially thought to reflect an immune response to the tumor, the balance of evidence clearly suggests GIMs can have potent tumor-tropic functions and assist in glioma cell growth and infiltration into normal brain. In this review, we focus on the evidence for GIMs aiding mediating glioblastoma motility and invasion. We survey the literature for molecular pathways that are involved in paracrine interaction between glioma cells and GIMs and assess which of these might serve as attractive targets for therapeutic intervention.

The tetraspanin network modulates MT1-MMP cell surface trafficking

The membrane-type 1 matrix metalloproteinase (MT1-MMP) drives fundamental physiological and pathophysiological processes. Among other substrates, MT1-MMP cleaves components of the extracellular matrix and activates other matrix-cleaving proteases such as MMP-2. Trafficking is a highly effective means to modulate MT1-MMP cell surface expression, and hence regulate its function. Here, we describe the complex interaction of MT1-MMP with tetraspanins, their effects on MT1-MMP intracellular trafficking and proteolytic function. Tetraspanins are credited as membrane organizers that form a network within the membrane to regulate the trafficking of associated proteins. In short, we found MT1-MMP to interact with the tetraspanin-associated EWI-2 protein by a yeast two-hybrid screen. Immunoprecipitation analysis confirmed this interaction and further revealed that MT1-MMP also stably interacts with distinct tetraspanins (CD9, CD37, CD53, CD63, CD81, and CD82) and the tetraspanin-like MAL protein. By using different MT1-MMP truncation constructs and mutants, we observed that all tetraspanins and MAL associated with the hemopexin domain of MT1-MMP. Moreover, this interaction was independent of O-glycosylation of MT1-MMP and exclusively occurred in the endoplasmic reticulum. Here, the respective subcellular compartment was identified by fitting the MT1-MMP interaction pattern to a model for post-translational processing of MT1-MMP. In addition, tetraspanins differentially affected the cell surface localization of MT1-MMP, its capacity to activate pro-MMP-2, and the collagen invasion capacity. Interestingly, the degree of tetraspanin-MT1-MMP association did not correlate with its impact on MT1-MMP function. Tetraspanins thus distinctly affect MT1-MMP subcellular localization and function, and may constitute an effective mechanism to control MT1-MMP-dependent proteolysis at the cell surface.

Physical break-down of the classical view on cancer cell invasion and metastasis

Eight classical hallmarks of cancer have been proposed and are well-defined by using biochemical or molecular genetic methods, but are not yet precisely defined by cellular biophysical processes. To define the malignant transformation of neoplasms and finally reveal the functional pathway, which enables cancer cells to promote cancer progression, these classical hallmarks of cancer require the inclusion of specific biomechanical properties of cancer cells and their microenvironment such as the extracellular matrix and embedded cells such as fibroblasts, macrophages or endothelial cells. Nonetheless a main novel ninth hallmark of cancer is still elusive in classical tumor biological reviews, which is the aspect of physics in cancer disease by the natural selection of an aggressive (highly invasive) subtype of cancer cells. The physical aspects can be analyzed by using state-of-the-art biophysical methods. Thus, this review will present current cancer research in a different light and will focus on novel physical methods to investigate the aggressiveness of cancer cells from a biophysicist's point of view. This may lead to novel insights into cancer disease and will overcome classical views on cancer. In addition, this review will discuss how physics of cancer can help to reveal whether cancer cells will invade connective tissue and metastasize. In particular, this review will point out how physics can improve, break-down or support classical approaches to examine tumor growth even across primary tumor boundaries, the invasion of single or collective cancer cells, transendothelial migration of cancer cells and metastasis in targeted organs. Finally, this review will show how physical measurements can be integrated into classical tumor biological analysis approaches. The insights into physical interactions between cancer cells, the primary tumor and the microenvironment may help to solve some "old" questions in cancer disease progression and may finally lead to novel approaches for development and improvement of cancer diagnostics and therapies.

ADAM12 redistributes and activates MMP-14, resulting in gelatin degradation, reduced apoptosis, and increased tumor growth

Matrix metalloproteases (MMPs), in particular MMP-2, -9, and -14, play a key role in various aspects of cancer pathology. Likewise, ADAMs (A Disintegrin And Metalloproteases), including ADAM12, are upregulated in malignant tumors and contribute to the pathology of cancers. Here we showed a positive correlation between MMP-14 and ADAM12 expression in human breast cancer. We demonstrated that in 293-VnR and human breast cancer cells expressing ADAM12 at the cell surface, endogenous MMP-14 was recruited to the cell surface, resulting in its activation. Subsequent to this activation, gelatin degradation was stimulated and tumor-cell apoptosis was decreased, with reduced expression of the pro-apoptotic proteins BCL2L11 and BIK. The effect on gelatin degradation was abrogated by inhibition of the MMP-14 activity and appeared to be dependent on cell-surface αVβ3 integrin localization, but neither the catalytic activity of ADAM12 nor the cytoplasmic tail of ADAM12 were required. The significance of ADAM12-induced activation of MMP-14 was underscored by a reduction in MMP-14–mediated gelatin degradation and abolition of apoptosis-protective effects by specific monoclonal antibodies against ADAM12. Furthermore, orthotopic implantation of ADAM12-expressing MCF7 cells in nude mice produced tumors with increased levels of activated MMP-14 and confirmed that ADAM12 protects tumor cells against apoptosis, leading to increased tumor progression. In conclusion, our data suggest that a ternary protein complex composed of ADAM12, αVβ3 integrin, and MMP-14 at the tumor cell surface regulates MMP-14 functions. This interaction may point to a novel concept for the development of MMP-14–targeting drugs in treating cancer.

Novel MT1-MMP small-molecule inhibitors based on insights into hemopexin domain function in tumor growth

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a promising drug target in malignancy. The structure of MT1-MMP includes the hemopexin domain (PEX) that is distinct from and additional to the catalytic domain. Current MMP inhibitors target the conserved active site in the catalytic domain and, as a result, repress the proteolytic activity of multiple MMPs instead of MT1-MMP alone. In our search for noncatalytic inhibitors of MT1-MMP, we compared the protumorigenic activity of wild-type MT1-MMP with an MT1-MMP mutant lacking PEX (ΔPEX). In contrast to MT1-MMP, ΔPEX did not support tumor growth in vivo, and its expression resulted in small fibrotic tumors that contained increased levels of collagen. Because these findings suggested an important role for PEX in tumor growth, we carried out an inhibitor screen to identify small molecules targeting the PEX domain of MT1-MMP. Using the Developmental Therapeutics Program (National Cancer Institute/NIH), virtual ligand screening compound library as a source and the X-ray crystal structure of PEX as a target, we identified and validated a novel PEX inhibitor. Low dosage, intratumoral injections of PEX inhibitor repressed tumor growth and caused a fibrotic, ΔPEX-like tumor phenotype in vivo. Together, our findings provide a preclinical proof of principle rationale for the development of novel and selective MT1-MMP inhibitors that specifically target the PEX domain.

Nuclear localization of matrix metalloproteinases

Matrix metalloproteinases (MMPs) were originally identified as matrixin proteases that act in the extracellular matrix. Recent works have uncovered nontraditional roles for MMPs in the extracellular space as well as in the cytosol and nucleus. There is strong evidence that subspecialized and compartmentalized matrixins participate in many physiological and pathological cellular processes, in which they can act as both degradative and regulatory proteases. In this review, we discuss the transcriptional and translational control of matrixin expression, their regulation of intracellular sorting, and the structural basis of activation and inhibition. In particular, we highlight the emerging roles of various matrixin forms in diseases. The activity of matrix metalloproteinases is regulated at several levels, including enzyme activation, inhibition, complex formation and compartmentalization. Most MMPs are secreted and have their function in the extracellular environment. MMPs are also found inside cells, both in the nucleus, cytosol and organelles. The role of intracellular located MMPs is still poorly understood, although recent studies have unraveled some of their functions. The localization, activation and activity of MMPs are regulated by their interactions with other proteins, proteoglycan core proteins and / or their glycosaminoglycan chains, as well as other molecules. Complexes formed between MMPs and various molecules may also include interactions with noncatalytic sites. Such exosites are regions involved in substrate processing, localized outside the active site, and are potential binding sites of specific MMP inhibitors. Knowledge about regulation of MMP activity is essential for understanding various physiological processes and pathogenesis of diseases, as well as for the development of new MMP targeting drugs.

Gubernaculum as icebreaker: do matrix metalloproteinases in rodent gubernaculum and inguinal fat pad permit testicular descent?

PURPOSE

Cryptorchidism is the most common male congenital abnormality. The rodent gubernaculum steers the testis from abdomen to scrotum postnatally by eversion and migration through the developing inguinal fat pad (IFP). We hypothesize that extracellular matrix remodeling in/around the gubernaculum is necessary for eversion and migration and is permitted by timed IFP maturation and aimed to examine regional development and matrix metalloproteinase (MMP) content.

METHODS

Embryonic day 19 (E19) and postnatal days 0 and 2 (P0, P2) wild-type Sprague-Dawley rats (n = 10) were prepared for histologic examination (trichrome) and immunohistochemistry (membrane-type MMP-1 [MT1-MMP], MMP2) and analyzed using light/confocal microscopy.

RESULTS

At E19, IFP contained fibroblasts and immature cells in an extensive collagenous extracellular matrix. Cells in the gubernaculum base were cytoplasmic-MT1-MMP-positive (inactive). At P0, the gubernaculum had everted, and adjacent cells were membranous-MT1-MMP-positive (active). At P2, the gubernaculum was migrating through the IFP, and adjacent cells were membranous-MT1-MMP-positive. Adipocyte maturation began cranially in the IFP and proceeded in a craniocaudal gradient until more uniformly mature at P2.

CONCLUSION

The MT1-MMP-positive cells may remodel the gubernaculum for eversion and provide the collagenolysis necessary for migration, like an icebreaking ship, through the IFP, which matures to permit migration through collagen-rich tissue. Disruption of these processes may cause cryptorchidism.

Inhibition of MT1-MMP activity using functional antibody fragments selected against its hemopexin domain

The membrane associated MMP, MT1-MMP, is a critical pericellular protease involved in tumour cell invasion and angiogenesis and is highly up-regulated in numerous human cancers. It therefore represents an exciting new therapeutic cancer-specific target. We have generated recombinant human scFv antibodies against the non-catalytic, hemopexin domain of MT1-MMP that modulate its interactions with collagen. One of these is an effective inhibitor of the invasive capacity of cancer cells and of angiogenesis in model systems. This demonstrates that targeting sites outside the catalytic domain presents a potential novel approach to proteinase inhibition that could have applications in cancer therapeutics.

Structure of collagenase G reveals a chew-and-digest mechanism of bacterial collagenolysis

Collagen constitutes one third of the body protein in humans, reflecting its extraordinary role in health and disease. Of similar importance, therefore, are the idiosyncratic proteases that nature evolved for collagen remodeling. Intriguingly, the most efficient collagenases are those that enable clostridial bacteria to colonize their host tissues, but despite intense studies, the structural and mechanistic basis of these enzymes has remained elusive. Here we present the crystal structure of collagenase G from Clostridium histolyticum at 2.55 Å resolution. By combining the structural data with enzymatic and mutagenesis studies, we derive a conformational two-state model of bacterial collagenolysis, in which the recognition and unraveling of collagen microfibrils into triple helices as well as the unwinding of the latter go hand in hand with collagenase opening and closing.

Regulation of matrix metalloproteinases activity studied in human endometrium as a paradigm of cyclic tissue breakdown and regeneration

When abundant and activated, matrix metalloproteinases (MMPs, or matrixins) degrade most, if not all, constituents of the extracellular matrix (ECM). The resulting massive tissue breakdown is best exemplified in humans by the menstrual lysis and shedding of the endometrium, the mucosa lining the uterus. After menstruation, MMP activity needs to be tightly controlled as the endometrium regenerates and differentiates to avoid abnormal tissue breakdown while allowing tissue repair and fine remodelling to accommodate implantation of a blastocyst. This paper reviews how MMPs are massively present and activated in the endometrium at menstruation, and how their activity is tightly controlled at other phases of the cycle. Progesterone represses expression of many but not all MMPs. Its withdrawal triggers focal expression of MMPs specifically in the areas undergoing lysis, an effect mediated by local cytokines such as interleukin-1α, LEFTY-2, tumour necrosis factor-α and others. MMP-3 is selectively expressed at that time and activates proMMP-9, otherwise present in latent form throughout the cycle. In addition, a large number of neutrophils loaded with MMPs are recruited at menstruation through induction of chemokines, such as interleukin-8. At the secretory phase, progesterone repression of MMPs is mediated by transforming growth factor-β. Tissue inhibitors of metalloproteinases (TIMPs) are abundant at all phases of the cycle to prevent any undue MMP activity, but are likely overwhelmed at menstruation. At other phases of the cycle, MMPs can elude TIMP inhibition as exemplified by recruitment of active MMP-7 to the plasma membrane of epithelial cells, allowing processing of membrane-associated growth factors needed for epithelial repair and proliferation. Finally, receptor-mediated endocytosis through low density lipoprotein receptor-related protein-1 (LRP-1) efficiently clears MMP-2 and -9 at the proliferative and secretory phases. This mechanism is probably essential to prevent any excessive ECM degradation by the active form of MMP-2 that is permanently present. However, shedding of the ectodomain of LRP-1 specifically at menstruation prevents endocytosis of MMPs allowing full degradation of the ECM. Thus endometrial MMPs are regulated at the levels of transcription, release from infiltrating neutrophils, activation, binding to the cell membrane, inhibition by TIMPs and endocytic clearance by LRP-1. This allows tight control during endometrial growth and differentiation but results in a burst of activity for menstrual tissue breakdown. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.

Diffusion of MMPs on the surface of collagen fibrils: the mobile cell surface-collagen substratum interface

Remodeling of the extracellular matrix catalyzed by MMPs is central to morphogenetic phenomena during development and wound healing as well as in numerous pathologic conditions such as fibrosis and cancer. We have previously demonstrated that secreted MMP-2 is tethered to the cell surface and activated by MT1-MMP/TIMP-2-dependent mechanism. The resulting cell-surface collagenolytic complex (MT1-MMP)(2)/TIMP-2/MMP-2 can initiate (MT1-MMP) and complete (MMP-2) degradation of an underlying collagen fibril. The following question remained: What is the mechanism of substrate recognition involving the two structures of relatively restricted mobility, the cell surface enzymatic complex and a collagen fibril embedded in the ECM? Here we demonstrate that all the components of the complex are capable of processive movement on a surface of the collagen fibril. The mechanism of MT1-MMP movement is a biased diffusion with the bias component dependent on the proteolysis of its substrate, not adenosine triphosphate (ATP) hydrolysis. It is similar to that of the MMP-1 Brownian ratchet we described earlier. In addition, both MMP-2 and MMP-9 as well as their respective complexes with TIMP-1 and -2 are capable of Brownian diffusion on the surface of native collagen fibrils without noticeable dissociation while the dimerization of MMP-9 renders the enzyme immobile. Most instructive is the finding that the inactivation of the enzymatic activity of MT1-MMP has a detectable negative effect on the cell force developed in miniaturized 3D tissue constructs. We propose that the collagenolytic complex (MT1-MMP)(2)/TIMP-2/MMP-2 represents a Mobile Cell Surface-Collagen Substratum Interface. The biological implications of MT1-MMP acting as a molecular ratchet tethered to the cell surface in complex with MMP-2 suggest a new mechanism for the role of spatially regulated peri-cellular proteolysis in cell-matrix interactions.

Inhibition of matrix metalloproteinase 14 (MMP-14)-mediated cancer cell migration

Matrix metalloproteinases (MMPs) have been shown to be key players in both extracellular matrix remodeling and cell migration during cancer metastasis. MMP-14, a membrane-anchored MMP, in particular, is closely associated with these processes. The hemopexin (PEX) domain of MMP-14 has been proposed as the modulating region involved in the molecular cross-talk that initiates cell migration through homodimerization of MMP-14 as well as heterodimerization with the cell surface adhesion molecule CD44. In this study, minimal regions required for function within the PEX domain were investigated through a series of substitution mutations. Blades I and IV were found to be involved in cell migration. We found that blade IV is necessary for MMP-14 homodimerization and that blade I is required for CD44 MMP-14 heterodimerization. Cross-talk between MMP-14 and CD44 results in phosphorylation of EGF receptor and downstream activation of the MAPK and PI3K signaling pathways involved in cell migration. Based on these mutagenesis analyses, peptides mimicking the essential outermost strand motifs within the PEX domain of MMP-14 were designed. These synthetic peptides inhibit MMP-14-enhanced cell migration in a dose-dependent manner but have no effect on the function of other MMPs. Furthermore, these peptides interfere with cancer metastasis without affecting primary tumor growth. Thus, targeting the MMP-14 hemopexin domain represents a novel approach to inhibit MMP-14-mediated cancer dissemination.

The dimer interface of the membrane type 1 matrix metalloproteinase hemopexin domain: crystal structure and biological functions

Homodimerization is an essential step for membrane type 1 matrix metalloproteinase (MT1-MMP) to activate proMMP-2 and to degrade collagen on the cell surface. To uncover the molecular basis of the hemopexin (Hpx) domain-driven dimerization of MT1-MMP, a crystal structure of the Hpx domain was solved at 1.7 Å resolution. Two interactions were identified as potential biological dimer interfaces in the crystal structure, and mutagenesis studies revealed that the biological dimer possesses a symmetrical interaction where blades II and III of molecule A interact with blades III and II of molecule B. The mutations of amino acids involved in the interaction weakened the dimer interaction of Hpx domains in solution, and incorporation of these mutations into the full-length enzyme significantly inhibited dimer-dependent functions on the cell surface, including proMMP-2 activation, collagen degradation, and invasion into the three-dimensional collagen matrix, whereas dimer-independent functions, including gelatin film degradation and two-dimensional cell migration, were not affected. These results shed light on the structural basis of MT1-MMP dimerization that is crucial to promote cellular invasion.

Genetic link between obesity and MMP14-dependent adipogenic collagen turnover

OBJECTIVE

In white adipose tissue, adipocytes and adipocyte precursor cells are enmeshed in a dense network of type I collagen fibrils. The fate of this pericellular collagenous web in diet-induced obesity, however, is unknown. This study seeks to identify the genetic underpinnings of proteolytic collagen turnover and their association with obesity progression in mice and humans.

RESEARCH DESIGN AND METHODS

The hydrolysis and degradation of type I collagen at early stages of high-fat diet feeding was assessed in wild-type or MMP14 (MT1-MMP)-haploinsufficient mice using immunofluorescent staining and scanning electron microscopy. The impact of MMP14-dependent collagenolysis on adipose tissue function was interrogated by transcriptome profiling with cDNA microarrays. Genetic associations between MMP14 gene common variants and obesity or diabetes traits were examined in a Japanese cohort (n = 3,653).

RESULTS

In adult mice, type I collagen fibers were cleaved rapidly in situ during a high-fat diet challenge. By contrast, in MMP14 haploinsufficient mice, animals placed on a high-fat diet were unable to remodel fat pad collagen architecture and display blunted weight gain. Moreover, transcriptional programs linking type I collagen turnover with adipogenesis or lipogenesis were disrupted by the associated decrease in collagen turnover. Consistent with a key role played by MMP14 in regulating high-fat diet-induced metabolic programs, human MMP14 gene polymorphisms located in proximity to the enzyme's catalytic domain were closely associated with human obesity and diabetes traits.

CONCLUSIONS

Together, these findings demonstrate that the MMP14 gene, encoding the dominant pericellular collagenase operative in vivo, directs obesogenic collagen turnover and is linked to human obesity traits.

Corneal epithelial MT1-MMP inhibits vascular endothelial cell proliferation and migration

PURPOSE

To determine the effects of corneal epithelial membrane-type 1 matrix metalloproteinase (MT1-MMP) on vascular endothelial migration and proliferation.

METHODS

We generated immortalized wild-type, MT1-MMP knockout and MT1-MMP knock-in corneal epithelial cells. Calf pulmonary arterial endothelial (CPAE) cell proliferation and Boyden chamber migration were assayed.

RESULTS

Conditioned media from MT1-MMP epithelial knockout cells significantly increased CPAE proliferation 5-bromo-2'-deoxy-uridine (BrdU) incorporation, and CPAE migration as compared with wild-type epithelial cells. Conditioned media from knock-in cells reversed the increase in CPAE proliferation, BrdU incorporation and CPAE migration. Knock-in cells transfected with mutant MT1-MMP (E240A) did not abrogate the reversal effect.

CONCLUSIONS

Corneal epithelial MT1-MMP is antiangiogenic. This antiangiogenic activity does not require the catalytic domain.

Inhibitory effects of arresten on bFGF-induced proliferation, migration, and matrix metalloproteinase-2 activation in mouse retinal endothelial cells

PURPOSE

The potential role of arresten (alpha1(IV)NC1) as an endogenous angiogenesis inhibitor in the prevention of bFGF mediated retinal angiogenesis and regulation of matrix metalloproteinase-2 activation has not been explored.

METHODS

Mouse retinal endothelial cells (MREC) were cultured on type IV collagen and treated with basic fibroblast growth factor (bFGF) alone or in the presence of arresten at concentrations ranging from 1 to 10 microg/ml. The proliferation of MRECs were evaluated using 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay, and bFGF stimulated endothelial cell migration was assessed using Boyden chamber. Expression of matrix metalloproteinase-2 (MMP-2) was assessed by reverse transcription polymerase chain reaction (RT-PCR) analysis using RNA isolated from MRECs. Secretion and activation of MMP-2 in arresten-treated conditioned MREC growth medium was determined by gelatin zymography and Western blotting.

RESULTS

Different doses of bFGF induced MREC proliferation was significantly inhibited upon arresten treatment (P < 0.005). The bFGF-induced migration was significantly inhibited by arresten at 1 and 10 microg/ml concentrations (P < 0.01). The bFGF stimulated expression of MMP-2 mRNA and secretion of MMP-2 in MREC was not affected and interestingly activation of MMP-2 was suppressed by arresten in a dose and time dependent manner.

CONCLUSIONS

Inhibitory effects of arresten on proliferation, migration and MMP-2 activation but not on expression and secretion of MMP-2 in MREC; this early work with arresten supports potential therapeutic action in retinal neovascularization dependent disorders.

Navigating ECM barriers at the invasive front: the cancer cell-stroma interface

A seminal event in cancer progression is the ability of the neoplastic cell to mobilize the necessary machinery to breach surrounding extracellular matrix barriers while orchestrating a host stromal response that ultimately supports tissue-invasive and metastatic processes. With over 500 proteolytic enzymes identified in the human genome, interconnecting webs of protease-dependent and protease-independent processes have been postulated to drive the cancer cell invasion program via schemes of daunting complexity. Increasingly, however, a body of evidence has begun to emerge that supports a unifying model wherein a small group of membrane-tethered enzymes, termed the membrane-type matrix metalloproteinases (MT-MMPs), plays a dominant role in regulating cancer cell, as well as stromal cell, traffic through the extracellular matrix barriers assembled by host tissues in vivo. Understanding the mechanisms that underlie the regulation and function of these metalloenzymes as host cell populations traverse the dynamic extracellular matrix assembled during neoplastic states should provide new and testable theories regarding cancer invasion and metastasis.

Matrix invasion by tumour cells: a focus on MT1-MMP trafficking to invadopodia

When migrating away from a primary tumour, cancer cells interact with and remodel the extracellular matrix (ECM). Matrix metalloproteinases (MMPs), and in particular the transmembrane MT1-MMP (also known as MMP-14), are key enzymes in tumour-cell invasion. Results from recent in vitro studies highlight that MT1-MMP is implicated both in the breaching of basement membranes by tumour cells and in cell invasion through interstitial type-I collagen tissues. Remarkably, MT1-MMP accumulates at invadopodia, which are specialized ECM-degrading membrane protrusions of invasive cells. Here we review current knowledge about MT1-MMP trafficking and its importance for the regulation of protease activity at invadopodia. In invasive cells, endocytosis of MT1-MMP by clathrin- and caveolae-dependent pathways can be counteracted by several mechanisms, which leads to protease stabilization at the cell surface and increased pericellular degradation of the matrix. Furthermore, the recent identification of cellular components that control delivery of MT1-MMP to invadopodia brings new insight into mechanisms of cancer-cell invasion and reveals potential pharmacological targets.

Structural and functional bases for allosteric control of MMP activities: can it pave the path for selective inhibition?

The zinc-dependent matrix metalloproteinases (MMPs) belong to a large family of structurally homologous enzymes. These enzymes are involved in a wide variety of biological processes ranging from physiological cell proliferation and differentiation to pathological states associated with tumor metastasis, inflammation, tissue degeneration, and cell death. Controlling the enzymatic activity of specific individual MMPs by antagonist molecules is highly desirable, first, for studying their individual roles, and second as potential therapeutic agents. However, blocking the enzymatic activity with synthetic small inhibitors appears to be an extremely difficult task. Thus, this is an unmet need presumably due to the high structural homology between MMP catalytic domains. Recent reports have recognized a potential role for exosite or allosteric protein regions, distinct from the extended catalytic pocket, in mediating MMP activation and substrate hydrolysis. This raises the possibility that MMP enzymatic and non-enzymatic activities may be modified via antagonist molecules targeted to such allosteric sites or to alternative enzyme domains. In this review, we discuss the structural and functional bases for potential allosteric control of MMPs and highlight potential alternative enzyme domains as targets for designing highly selective MMP inhibitors.

Identification and role of the homodimerization interface of the glycosylphosphatidylinositol-anchored membrane type 6 matrix metalloproteinase (MMP25)

The membrane type (MT) 6 matrix metalloproteinase (MMP) (MMP25) is a glycosylphosphatidylinositol-anchored matrix metalloproteinase (MMP) that is highly expressed in leukocytes and in some cancer tissues. We previously showed that natural MT6-MMP is expressed on the cell surface as a major reduction-sensitive form of M(r) 120, likely representing enzyme homodimers held by disulfide bridges. Among the membrane type-MMPs, the stem region of MT6-MMP contains three cysteine residues at positions 530, 532, and 534 which may contribute to dimerization. A systematic site-directed mutagenesis study of the Cys residues in the stem region shows that Cys(532) is involved in MT6-MMP dimerization by forming an intermolecular disulfide bond. The mutagenesis data also suggest that Cys(530) and Cys(534) form an intramolecular disulfide bond. The experimental observations on cysteines were also investigated by computational studies of the stem peptide, which validate these proposals. Dimerization is not essential for transport of MT6-MMP to the cell surface, partitioning into lipid rafts or cleavage of alpha-1-proteinase inhibitor. However, monomeric forms of MT6-MMP exhibited enhanced autolysis and metalloprotease-dependent degradation. Collectively, these studies establish the stem region of MT6-MMP as the dimerization interface, an event whose outcome imparts protease stability to the protein.