Cellular membrane type-1 matrix metalloproteinase (MT1-MMP) cleaves C3b, an essential component of the complement system

Regulation of the terminal complement cascade in adipose tissue for control of its volume, cellularity, and fibrosis

White adipose tissue (WAT) is a reservoir for various pathogens and their products, such as lipopolysaccharides. Therefore, it must be equipped with a defense mechanism connected with the activation of innate immunity. This explains the phenomenon that adipocytes express components of the classical and alternative complement pathways, which can be activated even in the absence of opportunistic pathogens. Terminal stages of the complement pathway are related to the production of membrane attack complexes and, thus, can cause lysis of pathogens, as well as autolysis of host adipocytes, contributing to the regulation of the cellularity in WAT. Complement-induced autolysis of adipocytes is counteracted by a number of cellular defense mechanisms. This versatility of activation and suppression processes enables a broad range of adaptability to physiological contexts, ranging from the development of hypertrophic WAT to lipodystrophy. Pathogen-induced activation of the complement pathway in WAT also induces a profibrotic phenotype. These processes may also be involved in the regulation of insulin resistance in adipocytes. This explains the dual immune/metabolic role of the complement pathway in WAT: the pathway is an integral part of the immune response but also potently involved in the control of volume and cellularity of WAT under both physiological and pathological conditions.

Is the endotoxin-complement cascade the major driver in lipedema?

Lipedema is a poorly understood disorder of adipose tissue characterized by abnormal but symmetrical deposition of subcutaneous white adipose tissue (WAT) in proximal extremities. Here, we propose that the underlying cause for lipedema could be triggered by a selective accumulation of bacterial lipopolysaccharides (LPS; also known as endotoxin) in gluteofemoral WAT. Together with a malfunctioning complement system, this induces low-grade inflammation in the depot and raises its uncontrollable expansion. Correspondingly, more attention should be paid in future research to the endotoxemia prevalent in patients with lipedema. We would like to propose that proper management of endotoxemia can reduce the progression and even improve the state of disease in patients with lipedema.

Multi-omics investigation of the resistance mechanisms of pomalidomide in multiple myeloma

Background

Despite significant therapeutic advances over the last decade, multiple myeloma remains an incurable disease. Pomalidomide is the third Immunomodulatory drug that is commonly used to treat patients with relapsed/refractory multiple myeloma. However, approximately half of the patients exhibit resistance to pomalidomide treatment. While previous studies have identified Cereblon as a primary target of Immunomodulatory drugs' anti-myeloma activity, it is crucial to explore additional mechanisms that are currently less understood.

Methods

To comprehensively investigate the mechanisms of drug resistance, we conducted integrated proteomic and metabonomic analyses of 12 plasma samples from multiple myeloma patients who had varying responses to pomalidomide. Differentially expressed proteins and metabolites were screened, and were further analyzed using pathway analysis and functional correlation analysis. Also, we estimated the cellular proportions based on ssGSEA algorithm. To investigate the potential role of glycine in modulating the response of MM cells to pomalidomide, cell viability and apoptosis were analyzed.

Results

Our findings revealed a consistent decrease in the levels of complement components in the pomalidomide-resistant group. Additionally, there were significant differences in the proportion of T follicular helper cell and B cells in the resistant group. Furthermore, glycine levels were significantly decreased in pomalidomide-resistant patients, and exogenous glycine administration increased the sensitivity of MM cell lines to pomalidomide.

Conclusion

These results demonstrate distinct molecular changes in the plasma of resistant patients that could be used as potential biomarkers for identifying resistance mechanisms for pomalidomide in multiple myeloma and developing immune-related therapeutic strategies.

Cell mediated ECM-degradation as an emerging tool for anti-fibrotic strategy

Investigation into the role of cells with respect to extracellular matrix (ECM) remodeling is still in its infancy. Particularly, ECM degradation is an indispensable process during the recovery from fibrosis. Cells with ECM degradation ability due to the secretion of various matrix metalloproteinases (MMPs) have emerged as novel contributors to the treatment of fibrotic diseases. In this review, we focus on the ECM degradation ability of cells associated with the repertoire of MMPs that facilitate the attenuation of fibrosis through the inhibition of ECM deposition. Besides, innovative approaches to engineering and characterizing cells with degradation ability, as well as elucidating the mechanism of the ECM degradation, are also illustrated. Studies conducted to date on the use of cell-based degradation for therapeutic purposes to combat fibrosis are summarized. Finally, we discuss the therapeutic potential of cells with high degradation ability, hoping to bridge the gap between benchside research and bedside applications in treating fibrotic diseases.

Emerging roles of MT-MMPs in embryonic development

Membrane-type matrix metalloproteinases (MT-MMPs) are cell membrane-tethered proteinases that belong to the family of the MMPs. Apart from their roles in degradation of the extracellular milieu, MT-MMPs are able to activate through proteolytic processing at the cell surface distinct molecules such as receptors, growth factors, cytokines, adhesion molecules, and other pericellular proteins. Although most of the information regarding these enzymes comes from cancer studies, our current knowledge about their contribution in distinct developmental processes occurring in the embryo is limited. In this review, we want to summarize the involvement of MT-MMPs in distinct processes during embryonic morphogenesis, including cell migration and proliferation, epithelial-mesenchymal transition, cell polarity and branching, axon growth and navigation, synapse formation, and angiogenesis. We also considered information about MT-MMP functions from studies assessed in pathological conditions and compared these data with those relevant for embryonic development.

Integrin-linked kinase activity modulates the pro-metastatic behavior of ovarian cancer cells

Epithelial ovarian cancer (EOC) is the most fatal gynecologic cancer in the U.S., resulting in >14,000 deaths/year. Most women are diagnosed at late stage with widely disseminated intra-peritoneal metastatic disease, resulting in a 5-year survival rate of <30%. EOCs spread via direct extension and exfoliation into the peritoneal cavity, adhesion to peritoneal mesothelial cells, mesothelial cell retraction to expose sub-mseothelial matrix and anchoring in the type I collagen-rich matrix to generate secondary lesions. As a molecular-level understanding of EOC metastasis may identify novel therapeutic targets, the current study evaluated the expression and activity of integrin-linked kinase (ILK), a Ser/Thr protein kinase activated upon integrin-mediated adhesion. Results show that ILK is co-expressed in EOC with the pro-metastatic enzyme membrane type 1 matrix metalloproteinase (MT1-MMP) and catalyzed phosphorylation of the cytoplasmic tail of the proteinase. Downregulation of ILK expression or activity reduced adhesion to and invasion of collagen gels and organotypic meso-mimetic cultures. As an initial early event in EOC metastasis is integrin-mediated adhesion, these results suggest that further evaluation of ILK inhibitors as anti-metastatic agents in EOC is warranted.

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.

Functional characterization of Anopheles matrix metalloprotease 1 reveals its agonistic role during sporogonic development of malaria parasites

The ability to invade tissues is a unique characteristic of the malaria stages that develop/differentiate within the mosquitoes (ookinetes and sporozoites). On the other hand, tissue invasion by many pathogens has often been associated with increased matrix metalloprotease (MMP) activity in the invaded tissues. By employing cell biology and reverse genetics, we studied the expression and explored putative functions of one of the three MMPs encoded in the genome of the malaria vector Anopheles gambiae, namely, the Anopheles gambiae MMP1 (AgMMP1) gene, during the processes of blood digestion, midgut epithelium invasion by Plasmodium ookinetes, and oocyst development. We show that AgMMP1 exists in two alternative isoforms resulting from alternative splicing; one secreted (S-MMP1) and associated with hemocytes, and one membrane type (MT-MMP1) enriched in the cell attachment sites of the midgut epithelium. MT-MMP1 showed a remarkable response to ookinete midgut invasion manifested by increased expression, enhanced zymogen maturation, and subcellular redistribution, all indicative of an implication in the midgut epithelial healing that accompanies ookinete invasion. Importantly, RNA interference (RNAi)-mediated silencing of the AgMMP1 gene revealed a postinvasion protective function of AgMMP1 during oocyst development. The combined results link for the first time an MMP with vector competence and mosquito-Plasmodium interactions.

The Complex Interaction of Matrix Metalloproteinases in the Migration of Cancer Cells through Breast Tissue Stroma

Breast cancer mortality is directly linked to metastatic spread. The metastatic cell must exhibit a complex phenotype that includes the capacity to escape from the primary tumour mass, invade the surrounding normal tissue, and penetrate into the circulation before proliferating in the parenchyma of distant organs to produce a metastasis. In the normal breast, cellular structures change cyclically in response to ovarian hormones leading to regulated cell proliferation and apoptosis. Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases. Their primary function is degradation of proteins in the extracellular matrix to allow ductal progression through the basement membrane. A complex balance between matrix metalloproteinases and their inhibitors regulate these changes. These proteinases interact with cytokines, growth factors, and tumour necrosis factors to stimulate branching morphologies in normal breast tissues. In breast cancer this process is disrupted facilitating tumour progression and metastasis and inhibiting apoptosis increasing the life of the metastatic cells. This paper highlights the role of matrix metalloproteinases in cell progression through the breast stroma and reviews the complex relationships between the different proteinases and their inhibitors in relation to breast cancer cells as they metastasise.

Role of C5b-9 complement complex and response gene to complement-32 (RGC-32) in cancer

Complement system activation plays an important role in both innate and acquired immunity, with the activation of complement and the subsequent formation of C5b-9 terminal complement complex on cell membranes inducing target cell death. Recognition of this role for C5b-9 leads to the assumption that C5b-9 might play an antitumor role. However, sublytic C5b-9 induces cell cycle progression by activating signal transduction pathways and transcription factors in cancer cells, indicating a role in tumor promotion for this complement complex. The induction of the cell cycle by C5b-9 is dependent upon the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/FOXO1 and ERK1 pathways in a Gi protein-dependent manner. C5b-9 also induces response gene to complement (RGC)-32, a gene that plays a role in cell cycle promotion through activation of Akt and the CDC2 kinase. RGC-32 is expressed by tumor cells and plays a dual role in cancers, in that it has both a tumor suppressor role and tumor-promoting activity. Thus, through the activation of tumor cells, the C5b-9-mediated induction of the cell cycle plays an important role in tumor proliferation and oncogenesis.

Serum proteomic profiling for the early diagnosis of colorectal cancer

No ideal serum biomarker currently exists for the early diagnosis of colorectal cancer (CRC). Magnetic bead-based fractionation coupled with MALDI-TOF MS was used to screen serum samples from CRC patients, healthy controls, and other cancer patients. A diagnostic model with five proteomic features (m/z 1778.97, 1866.16, 1934.65, 2022.46, and 4588.53) was generated using Fisher algorithm with best performance. The Fisher-based model could discriminate CRC patients from the controls with 100% (46/46) sensitivity and 100% (35/35) specificity in the training set, 95.6% (43/45) sensitivity and 83.3% (35/42) specificity in the test set. We further validated the model with 94.4% (254/269) sensitivity and 75.5% (83/110) specificity in the external independent group. In other cancers group, the Fisher-based model classified 25 of 46 samples (54.3%) as positive and the other 21 as negative. With FT-ICR-MS, the proteomic features of m/z 1778.97, 1866.16, 1934.65, and 2022.46, of which intensities decreased significantly in CRC, were identified as fragments of complement C3f. Therefore, the Fisher-based model containing five proteomic features was able to effectively differentiate CRC patients from healthy controls and other cancers with a high sensitivity and specificity, and may be CRC-specific. Serum complement C3f, which was significantly decreased in CRC group, may be relevant to the incidence of CRC.

Detection of the heterogeneous O-glycosylation profile of MT1-MMP expressed in cancer cells by a simple MALDI-MS method

Background

Glycosylation is an important and universal post-translational modification for many proteins, and regulates protein functions. However, simple and rapid methods to analyze glycans on individual proteins have not been available until recently.

Methods/Principal Findings

A new technique to analyze glycopeptides in a highly sensitive manner by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) using the liquid matrix 3AQ/CHCA was developed recently and we optimized this technique to analyze a small amount of transmembrane protein separated by SDS-PAGE. We used the MALDI-MS method to evaluate glycosylation status of membrane-type 1 matrix metalloproteinase (MT1-MMP). O-glycosylation of MT1-MMP is reported to modulate its protease activity and thereby to affect cancer cell invasion. MT1-MMP expressed in human fibrosarcoma HT1080 cells was immunoprecipitated and resolved by SDS-PAGE. After in-gel tryptic digestion of the protein, a single droplet of the digest was applied directly to the liquid matrix on a MALDI target plate. Concentration of hydrophilic glycopeptides within the central area occurred due to gradual evaporation of the sample solution, whereas nonglycosylated hydrophobic peptides remained at the periphery. This specific separation and concentration of the glycopeptides enabled comprehensive analysis of the MT1-MMP O-glycosylation.

Conclusions/Significance

We demonstrate, for the first time, heterogeneous O-glycosylation profile of a protein by a whole protein analysis using MALDI-MS. Since cancer cells are reported to have altered glycosylation of proteins, this easy-to-use method for glycopeptide analysis opens up the possibility to identify specific glycosylation patterns of proteins that can be used as new biomarkers for malignant tumors.

Vitamin D binding protein isoforms as candidate predictors of disease extension in childhood arthritis

INTRODUCTION

Juvenile idiopathic arthritis (JIA) comprises a poorly understood group of chronic autoimmune diseases with variable clinical outcomes. We investigated whether the synovial fluid (SF) proteome could distinguish a subset of patients in whom disease extends to affect a large number of joints.

METHODS

SF samples from 57 patients were obtained around time of initial diagnosis of JIA, labeled with Cy dyes and separated by two-dimensional electrophoresis. Multivariate analyses were used to isolate a panel of proteins which distinguish patient subgroups. Proteins were identified using MALDI-TOF mass spectrometry with expression verified by immunochemical methods. Protein glycosylation status was confirmed by hydrophilic interaction liquid chromatography.

RESULTS

A truncated isoform of vitamin D binding protein (VDBP) is present at significantly reduced levels in the SF of oligoarticular patients at risk of disease extension, relative to other subgroups (p<0.05). Furthermore, sialylated forms of immunopurified synovial VDBP were significantly reduced in extended oligoarticular patients (p<0.005).

CONCLUSION

Reduced conversion of VDBP to a macrophage activation factor may be used to stratify patients to determine risk of disease extension in JIA patients.

Oxymatrine inhibits MMP-2 expression and reduces cell invasion in human pancreatic carcinoma cell line SW1990

AIM: To examine the effects of treatment with oxymatrine (OM) on MMP-2 expression and cell invasion in human pancreatic carcinoma cell line SW1990.

METHODS: Cultured SW1990 cells were randomly divided into two groups: control group and OM group. The OM group was further divided into three subgroups, which were treated with three different doses of OM (1, 2 and 4 g/L). MMP-2 expression in SW1990 cells was analyzed by real-time RT-PCR. Cell invasion, migration and proliferation were measured by scratch assay, transwell invasion assay and MTT assay, respectively.

RESULTS: The expression levels of MMP-2 mRNA in SW1990 cells in the three OM subgroups were significantly lower than that in the control group (0.53 ± 0.03, 0.42 ± 0.02, 0.29 ± 0.03 vs 0.70 ± 0.03, all P < 0.05). The invasion of cells in the three OM subgroups was markedly lower than that in the control group (325 ± 64.43, 206 ± 84.76, 124 ± 46.78 vs 498 ± 78.54, all P < 0.05). The mobility of cells in the three OM subgroups was also significantly lower than that in the control group (385.0 ± 58.9, 287.0 ± 79.8, 186.0 ± 60.9 vs 586.0 ± 85.8, all P < 0.05).

CONCLUSION: OM reduces the invasion of SW1990 cells possibly by inhibiting the expression of MMP-2.

Diagnostic and prognostic biomarker discovery strategies for autoimmune disorders

Current clinical, laboratory or radiological parameters cannot accurately diagnose or predict disease outcomes in a range of autoimmune disorders. Biomarkers which can diagnose at an earlier time point, predict outcome or help guide therapeutic strategies in autoimmune diseases could improve clinical management of this broad group of debilitating disorders. Additionally, there is a growing need for a deeper understanding of multi-factorial autoimmune disorders. Proteomic platforms offering a multiplex approach are more likely to reflect the complexity of autoimmune disease processes. Findings from proteomic based studies of three distinct autoimmune diseases are presented and strategies compared. It is the authors' view that such approaches are likely to be fruitful in the movement of autoimmune disease treatment away from reactive decisions and towards a preventative stand point.

Stratification and monitoring of juvenile idiopathic arthritis patients by synovial proteome analysis

Juvenile idiopathic arthritis (JIA) comprises a poorly understood group of chronic, childhood onset, autoimmune diseases with variable clinical outcomes. We investigated whether profiling of the synovial fluid (SF) proteome by a fluorescent dye based, two-dimensional gel (DIGE) approach could distinguish patients in whom inflammation extends to affect a large number of joints, early in the disease process. SF samples from 22 JIA patients were analyzed: 10 with oligoarticular arthritis, 5 extended oligoarticular and 7 polyarticular disease. SF samples were labeled with Cy dyes and separated by two-dimensional electrophoresis. Multivariate analyses were used to isolate a panel of proteins which distinguish patient subgroups. Proteins were identified using MALDI-TOF mass spectrometry with expression further verified by Western immunoblotting and immunohistochemistry. Hierarchical clustering based on the expression levels of a set of 40 proteins segregated the extended oligoarticular from the oligoarticular patients (p < 0.05). Expression patterns of the isolated protein panel have also been observed over time, as disease spreads to multiple joints. The data indicates that synovial fluid proteome profiles could be used to stratify patients based on risk of disease extension. These protein profiles may also assist in monitoring therapeutic responses over time and help predict joint damage.

Immune evasion of Enterococcus faecalis by an extracellular gelatinase that cleaves C3 and iC3b

Enterococcus faecalis (Ef) accounts for most cases of enterococcal bacteremia, which is one of the principal causes of nosocomial bloodstream infections (BSI). Among several virulence factors associated with the pathogenesis of Ef, an extracellular gelatinase (GelE) has been known to be the most common factor, although its virulence mechanisms, especially in association with human BSI, have yet to be demonstrated. In this study, we describe the complement resistance mechanism of Ef mediated by GelE. Using purified GelE, we determined that it cleaved the C3 occurring in human serum into a C3b-like molecule, which was inactivated rapidly via reaction with water. This C3 convertase-like activity of GelE was shown to result in a consumption of C3 and thus inhibited the activation of the complement system. Also, GelE was confirmed to degrade an iC3b that was deposited on the Ag surfaces without affecting the bound C3b. This proteolytic effect of GelE against the major complement opsonin resulted in a substantial reduction in Ef phagocytosis by human polymorphonuclear leukocytes. In addition, we verified that the action of GelE against C3, which is a central component of the complement cascade, was human specific. Taken together, it was suggested that GelE may represent a promising molecule for targeting human BSI associated with Ef.

Pharmacoproteomics of a metalloproteinase hydroxamate inhibitor in breast cancer cells: dynamics of membrane type 1 matrix metalloproteinase-mediated membrane protein shedding

Broad-spectrum matrix metalloproteinase (MMP) inhibitors (MMPI) were unsuccessful in cancer clinical trials, partly due to side effects resulting from limited knowledge of the full repertoire of MMP substrates, termed the substrate degradome, and hence the in vivo functions of MMPs. To gain further insight into the degradome of MMP-14 (membrane type 1 MMP) an MMPI, prinomastat (drug code AG3340), was used to reduce proteolytic processing and ectodomain shedding in human MDA-MB-231 breast cancer cells transfected with MMP-14. We report a quantitative proteomic evaluation of the targets and effects of the inhibitor in this cell-based system. Proteins in cell-conditioned medium (the secretome) and membrane fractions with levels that were modulated by the MMPI were identified by isotope-coded affinity tag (ICAT) labeling and tandem mass spectrometry. Comparisons of the expression of MMP-14 with that of a vector control resulted in increased MMP-14/vector ICAT ratios for many proteins in conditioned medium, indicating MMP-14-mediated ectodomain shedding. Following MMPI treatment, the MMPI/vehicle ICAT ratio was reversed, suggesting that MMP-14-mediated shedding of these proteins was blocked by the inhibitor. The reduction in shedding or the release of substrates from pericellular sites in the presence of the MMPI was frequently accompanied by the accumulation of the protein in the plasma membrane, as indicated by high MMPI/vehicle ICAT ratios. Considered together, this is a strong predictor of biologically relevant substrates cleaved in the cellular context that led to the identification of many undescribed MMP-14 substrates, 20 of which we validated biochemically, including DJ-1, galectin-1, Hsp90alpha, pentraxin 3, progranulin, Cyr61, peptidyl-prolyl cis-trans isomerase A, and dickkopf-1. Other proteins with altered levels, such as Kunitz-type protease inhibitor 1 and beta-2-microglobulin, were not substrates in biochemical assays, suggesting an indirect affect of the MMPI, which might be important in drug development as biomarkers or, in preclinical phases, to predict systemic drug actions and adverse side effects. Hence, this approach describes the dynamic pattern of cell membrane ectodomain shedding and its perturbation upon metalloproteinase drug treatment.

Highly specific inhibition of C1q globular-head binding to human IgG: a novel approach to control and regulate the classical complement pathway using an engineered single chain antibody variable fragment

We sought to specifically regulate the binding of human C1q, and thus the activation of the first complement component, via the construction of a single chain antibody variable binding region fragment (scFv) targeting the C1q globular heads. Here we describe details of the construction, expression and evaluation of this scFv, which was derived from a high-affinity hybridoma (Qu) specific for the C1q globular heads. The scFv was comprised of the Qu variable heavy chain domain (VH) linked to the Qu variable light chain domain (VL) and was termed scFv-QuVHVL. When mixed with either purified C1q or with human serum as a source of C1, scFv-QuVHVL bound to C1q and competitively restricted the interaction of C1q or C1 with immobilized IgG or with IgG1 antibody-coated cells, and prevented the activation of native C1 in human serum as determined by analyses of C1-mediated C4 deposition and fluid-phase C4 conversion. However scFv-QuVHVL could be manipulated to become a C1 activator when it was irreversibly immobilized onto microtiter ELISA plates, prior to contact with human serum complement. This functional dichotomy can be a useful tool in selectively elucidating, differentiating, inducing or inhibiting specific roles of human C1q and the classical complement pathway in complement-mediated physiological processes. We project that once fully humanized, fluid-phase scFv-QuVHVL could become a useful therapeutic in limiting inadvertent host tissue damage elicited by the classical complement pathway.

Construction of antisense MT1-MMP vector and its inhibitory effects on invasion of human ovarian cancer cells

Membrane-type 1 matrix metalloproteinase (MT1-MMP/MMP-14) plays crucial roles in tumor cell growth, invasion, and angiogenesis. To clarify whether the endogenously expressed MT1-MMP in metastatic human ovarian carcinoma cell lines SKOV3 plays a critical role in tumor cell invasiveness, antisense MT1-MMP cloned in eukaryotic expression vector pMMP14as was transferred into SKOV3 cells. 48h after transfection, decreased expression of endogenous MT1-MMP protein was detected in pMMP14as-transfected SKOV3 cells and the activation of pro-MMP2 was inhibited markedly. The mean percentage of invasive cells was (62.50 +/- 5.30) % in pMMP14as-transfected cells, which was obviously less than that (97.20 +/- 6.90) % in the control. Thus, antisense MT1-MMP effectively inhibited the endogenous MT1-MMP expression and the invasiveness in SKOV3 cells, suggesting that MT1-MMP may be a therapeutic target molecule for human invasive ovarian cancers.

The biochemical, biological, and pathological kaleidoscope of cell surface substrates processed by matrix metalloproteinases

Matrix metalloproteinases (MMPs) constitute a family of more than 20 endopeptidases. Identification of specific matrix and non-matrix components as MMP substrates showed that, aside from their initial role as extracellular matrix modifiers, MMPs play significant roles in highly complex processes such as the regulation of cell behavior, cell-cell communication, and tumor progression. Thanks to the comprehensive examination of the expanded MMP action radius, the initial view of proteases acting in the soluble phase has evolved into a kaleidoscope of proteolytic reactions connected to the cell surface. Important classes of cell surface molecules include adhesion molecules, mediators of apoptosis, receptors, chemokines, cytokines, growth factors, proteases, intercellular junction proteins, and structural molecules. Proteolysis of cell surface proteins by MMPs may have extremely diverse biological implications, ranging from maturation and activation, to inactivation or degradation of substrates. In this way, modification of membrane-associated proteins by MMPs is crucial for communication between cells and the extracellular milieu, and determines cell fate and the integrity of tissues. Hence, insights into the processing of cell surface proteins by MMPs and the concomitant effects on physiological processes as well as on disease onset and evolution, leads the way to innovative therapeutic approaches for cancer, as well as degenerative and inflammatory diseases.

Increase diagnostic efficacy by combined use of fingerprint markers in mass spectrometry—Plasma peptidomes from nasopharyngeal cancer patients for example

OBJECTIVES

There is no plasma marker for detecting nasopharyngeal cancer (NPC). We developed a bead-based affinity fractionated proteomic method to search potential plasma markers for NPC.

DESIGN AND METHODS

Affinity purification of heparinized plasma with Cu-chelated beads and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis were used to screen potential NPC markers. We compiled MS protein profiles for 47 patients with NPC and compared them to profiles from 28 healthy controls. The spectra were statistically analyzed using flexAnalysis and ClinProt bioinformatics software. Diagnostic efficacy was evaluated by determination of the assay sensitivity and specificity of each marker.

RESULTS

Twelve mass fingerprint markers differing between cancer and control spectra were found. The sensitivities of these NPC markers are various ranging from 36% to 83%, and the specificities were all over 90%. Combine use of these markers significantly increases diagnostic efficacy. In which, the combined markers (2020 Da and 4635 Da) possess best discriminator with high sensitivity (94%) and specificity (93%). We further identify a C3 fragment, C3f, that may serve as a biomarker for NPC.

CONCLUSION

The combined use of mass fingerprint markers in plasma proteome will enhance diagnostic efficacy for NPC. This method can be applied to search for novel plasma markers for cancers.

Complement 3d: from molecular adjuvant to target of immune escape mechanisms

C3d is a fragment of the complement factor C3 and is generated in the course of complement activation. When bound to antigen in single or multiple copies, the B cell receptor and complement receptor 2 become co-crosslinked resulting in decreased or increased B cell responses depending on the valence of the antigen-C3d construct. When antigen-C3d constructs are used for the purpose of generating a protective immune response (vaccines), they may either enhance the expected response or suppress it depending on the nature of the antigen. Various pathogens use C3d to evade the immune system by inhibiting complement activation, invading and homing in host cells or masking immunogenic areas of pathogen proteins. Therefore, future vaccination strategies for infectious diseases and cancer employing C3d as a molecular adjuvant need to be carefully evaluated before choosing a target antigen in order to take advantage of the adjuvant effect of the complement component while avoiding potential vaccine complications associated with immune escape mechanisms.

Interference with the complement system by tumor cell membrane type-1 matrix metalloproteinase plays a significant role in promoting metastasis in mice

Neoplasms have developed strategies to protect themselves against the complement-mediated host immunity. Invasion- and metastasis-promoting membrane type-1 (MT1) matrix metalloproteinase (MMP) is strongly associated with many metastatic cancer types. The relative importance of the individual functions of MT1-MMP in metastasis was, however, unknown. We have now determined that the expression of murine MT1-MMP in murine melanoma B16F1 cells strongly increased the number of metastatic loci in the lungs of syngeneic C57BL/6 mice. In contrast, MT1-MMP did not affect the number of metastatic loci in complement-deficient C57BL/6-C3-/- mice. Our results indicated, for the first time, that the anticomplement activity of MT1-MMP played a significant role in promoting metastasis in vivo and determined the relative importance of the anticomplement activity in the total metastatic effect of this multifunctional proteolytic enzyme. We believe that our results shed additional light on the functions of MT1-MMP in cancer and clearly make this protease a promising drug target in metastatic malignancies.

Mislocalization and unconventional functions of cellular MMPs in cancer

MMPs are multifunctional enzymes capable of targeting the extracellular matrix, growth factors, cytokines and cell surface-associated adhesion and signaling receptors. The cellular localization and the activity of MMPs are tightly controlled at both the transcriptional and the post-transcriptional levels. Mislocalization and presentation in unconventional cellular compartments provide MMPs with an opportunity to cleave previously unidentified proteins. This review is focused on two, entirely different MMPs, one of which is membrane-tethered and another of which is soluble (MT1-MMP and MMP-26, respectively) from twenty four known human MMPs. Our recent studies determined that both of these enzymes functioned at unexpected cellular compartments and it was resulted in the identification of novel proteolytic pathways, whose significance we only partially comprehend as of this writing. It is reasonable, however, to hypothesize from these data that many individual MMPs perform in a similar manner and display a much broader range of functions compared to what we earlier thought.

O-Glycosylation Regulates Autolysis of Cellular Membrane Type-1 Matrix Metalloproteinase (MT1-MMP)

MT1-MMP is a key enzyme in cancer cell invasion and metastasis. The activity of cellular MT1-MMP is regulated by furin-like proprotein convertases, TIMPs, shedding, autoproteolysis, dimerization, exocytosis, endocytosis, and recycling. Our data demonstrate that, in addition to these already known mechanisms, MT1-MMP is regulated by O-glycosylation of its hinge region. Insignificant autolytic degradation is characteristic for naturally expressed, glycosylated, MT1-MMP. In turn, extensive autolytic degradation, which leads to the inactivation of the protease and the generation of its C-terminal membrane-tethered degraded species, is a feature of overexpressed MT1-MMP. We have determined that incomplete glycosylation stimulates extensive autocatalytic degradation and self-inactivation of MT1-MMP. Self-proteolysis commences during the secretory process of MT1-MMP through the cell compartment to the plasma membrane. The strongly negatively charged sialic acid is the most important functional moiety of the glycopart of MT1-MMP. We hypothesize that sialic acid of the O-glycosylation cassette restricts the access of the catalytic domain to the hinge region and to the autolytic cleavage site and protects MT1-MMP from autolysis. Overall, our results point out that there is a delicate balance between glycosylation and self-proteolysis of MT1-MMP in cancer cells and that when this balance is upset the catalytically potent MT1-MMP pool is self-proteolyzed.

Postoperative serum proteomic profiles may predict metastatic relapse in high-risk primary breast cancer patients receiving adjuvant chemotherapy

A total of 30-50% of early breast cancer (EBC) patients considered as high risk using standard prognostic factors develop metastatic recurrence despite standard adjuvant systemic treatment. A means to better predict clinical outcome is needed to optimize and individualize therapeutic decisions. To identify a protein signature correlating with metastatic relapse, we performed surface-enhanced laser desorption/ionization-time of flight mass spectrometry profiling of early postoperative serum from 81 high-risk EBC patients. Denatured and fractionated serum samples were incubated with IMAC30 and CM10 ProteinChip arrays. Several protein peaks were differentially expressed according to clinical outcome. By combining partial least squares and logistic regression methods, we built a multiprotein model that correctly predicted outcome in 83% of patients. The 5-year metastasis-free survival in 'good prognosis' and 'poor prognosis' patients as defined using the multiprotein index were strikingly different (83 and 22%, respectively; P<0.0001, log-rank test). In a multivariate Cox regression including conventional pathological factors and multiprotein index, the latter retained the strongest independent prognostic significance for metastatic relapse. Major components of the multiprotein index included haptoglobin, C3a complement fraction, transferrin, apolipoprotein C1 and apolipoprotein A1. Therefore, postoperative serum protein pattern may have an important prognostic value in high-risk EBC.

AFM study of complement system assembly initiated by antigen-antibody complex

The shape and size of complement system C1 components assembled on a SiO2 surface after classical activation by antigen-antibody complex was determined by tapping mode atomic force microscopy (AFM). The SiO2 substrate was silanized and bovine leukemia virus proteins gp51 were covalently bound to the SiO2 substrate. Self-assembly of complement system proteins was investigated by AFM. Uniform coating of silanized surface by gp51 proteins was observed by AFM. After incubation of gp51 coated substrate in anti-gp51 antibody containing solution, Ag-Ab complexes were detected on the substrate surface by AFM. Then after treatment of Ag-Ab complex modified substrate by guinea-pig blood serum containing highly active complement system proteins for 3 minutes and 30 minutes features 2–3 times and 5–8 times higher in diameter and in height if compared with those observed after formation of Ag-Ab complex, were observed respectively on the surface of SiO2. This study revealed that AFM might be applied for the imaging of complement system assembly and provides valuable information that can be used to complement other well-established techniques.

Membrane type-1 matrix metalloproteinase (MT1-MMP) exhibits an important intracellular cleavage function and causes chromosome instability

Elevated expression of membrane type-1 matrix metalloproteinase (MT1-MMP) is closely associated with malignancies. There is a consensus among scientists that cell surface-associated MT1-MMP is a key player in pericellular proteolytic events. Now we have identified an intracellular, hitherto unknown, function of MT1-MMP. We demonstrated that MT1-MMP is trafficked along the tubulin cytoskeleton. A fraction of cellular MT1-MMP accumulates in the centrosomal compartment. MT1-MMP targets an integral centrosomal protein, pericentrin. Pericentrin is known to be essential to the normal functioning of centrosomes and to mitotic spindle formation. Expression of MT1-MMP stimulates mitotic spindle aberrations and aneuploidy in non-malignant cells. Volumes of data indicate that chromosome instability is an early event of carcinogenesis. In agreement, the presence of MT1-MMP activity correlates with degraded pericentrin in tumor biopsies, whereas normal tissues exhibit intact pericentrin. We believe that our data show a novel proteolytic pathway to chromatin instability and elucidate the close association of MT1-MMP with malignant transformation.

Non-proteolytic, receptor/ligand interactions associate cellular membrane type-1 matrix metalloproteinase with the complement component C1q

Membrane type-1 matrix metalloproteinase (MT1-MMP), a prototypic member of the membrane-tethered MMP family, is an essential component of a cellular proteolysis apparatus. Recognition of protein cleavage targets followed by proteolysis is a main function of MT1-MMP. For the first time, however, we present evidence that MT1-MMP and other structurally related membrane MMPs bind C1q, the recognition unit of the first component of complement C1 that initiates activation of the classical pathway of complement. These interactions involve the catalytic domain of MT1-MMP and the C1q globular domain. In silico modeling followed by mutagenesis and the in vitro and cell-based binding studies showed that the His(171)-Glu-Lys-Gln-Ala-Asp(176) and Val(223)-Arg-Asn(224) peptide sequences of MT1-MMP are directly involved in the binding with C1q. These sequence regions are spatially distant from the active site of the protease. As a result, the catalytically active and the catalytically latent forms of cellular MT1-MMP are both efficient in binding with C1q. In agreement, despite the MT1-MMP/C1q interactions, C1q is totally resistant to MT1-MMP proteolysis. The discovery of the unconventional, receptor/ligand-like interactions of MT1-MMP with C1q, an essential component of immunity, is a significant step toward a more complete understanding of the role of this membrane-tethered protease in cancer.