Matrix metalloproteinase-7 degrades all insulin-like growth factor binding proteins and facilitates insulin-like growth factor bioavailability

Acute regulation of IGF-I by alterations in post-exercise macronutrients

This investigation sought to examine the contributions of exercise and nutrient replenishment on in vivo regulation of the insulin-like growth factor-I (IGF-I) axis components. Eight college-aged males completed three high-intensity interval training (HIIT) protocols followed by three post-exercise nutritional protocols: (1) placebo (EX); (2) carbohydrate only (CHO); and (3) essential amino acid/carbohydrate (EAA/CHO). Samples were analyzed for growth hormone (GH), free IGF-I, IGFBP-1, IGFBP-2, insulin, hematocrit, hemoglobin, serum leucine, matrix metalloproteinase-9 (MMP-9) proteolytic activity, and presence of IGFBP-3 protease activity. No evidence for IGFBP-3 proteolysis was observed. Significant increases in [free IGF-I] and [leucine] were observed in the EAA/CHO group only. Significant differences were noted in [IGFBP-1] and [IGFBP-2] across conditions. Significant increases in [GH] and MMP-9 activity were observed in all groups. These results indicate that post-exercise macronutrient ratio is a determinant of [free IGF-I], [IGFBP-1 and -2] and may play a role in modulating the IGF-I axis in vivo.

A bioresponsive hydrogel tuned to chondrogenesis of human mesenchymal stem cells

Cartilage tissue engineering aims to replace damaged or diseased tissue with a functional regenerate that restores joint function. Scaffolds are used to deliver cells and facilitate tissue development, but they can also interfere with the structural assembly of the cartilage matrix. Biodegradable scaffolds have been proposed as a means to improve matrix deposition and the biomechanical properties of neocartilage. The challenge is designing scaffolds with appropriate degradation rates, ideally such that scaffold degradation is proportional to matrix deposition. In this study, we developed a bioresponsive hydrogel with cell-mediated degradation aligned to the chondrogenic differentiation of human mesenchymal stem cells (hMSCs). We identified matrix metalloproteinase 7 (MMP7) as an enzyme with a temporal expression pattern that corresponded with cartilage development. By embedding MMP7 peptide substrates within a poly(ethylene glycol) diacrylate backbone, we built MMP7-sensitive hydrogels with distinct degradation rates. When MMP7-sensitive scaffolds were compared with nondegradable scaffolds in vitro, photoencapsulated hMSCs produced neocartilage constructs with more extensive collagenous matrices, as demonstrated through immunohistochemistry and biochemical quantification of matrix molecules. Furthermore, these changes translated into an increased dynamic compressive modulus. This work presents a practical strategy for designing biomaterials uniquely tuned to individual biological processes.

The role of matrix metalloproteinases in cystic fibrosis lung disease

Significant airway remodelling is a major component of the increased morbidity and mortality observed in cystic fibrosis (CF) patients. These airways feature ongoing leukocytic inflammation and unrelenting bacterial infection. In contrast to acute bacterial pneumonia, CF infection is not cleared efficiently and the ensuing inflammatory response causes tissue damage. This structural damage is mainly a result of free proteolytic activity released by infiltrated neutrophils and macrophages. Major proteases in this disease are serine and matrix metalloproteases (MMPs). While the role of serine proteases, such as elastase, has been characterised in detail, there is emerging evidence that MMPs could play a key role in the pathogenesis of CF lung disease. This review summarises studies linking MMPs with CF lung disease and discusses the potential value of MMPs as future therapeutic targets in CF and other chronic lung diseases.

A candidate targeting molecule of insulin-like growth factor-I receptor for gastrointestinal cancers

Advances in molecular research in cancer have brought new therapeutic strategies into clinical usage. One new group of targets is tyrosine kinase receptors, which can be treated by several strategies, including small molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAbs). Aberrant activation of growth factors/receptors and their signal pathways are required for malignant transformation and progression in gastrointestinal (GI) carcinomas. The concept of targeting specific carcinogenic receptors has been validated by successful clinical application of many new drugs. Type I insulin-like growth factor (IGF) receptor (IGF-IR) signaling potently stimulates tumor progression and cellular differentiation, and is a promising new molecular target in human malignancies. In this review, we focus on this promising therapeutic target, IGF-IR. The IGF/IGF-IR axis is an important modifier of tumor cell proliferation, survival, growth, and treatment sensitivity in many malignant diseases, including human GI cancers. Preclinical studies demonstrated that downregulation of IGF-IR signals reversed the neoplastic phenotype and sensitized cells to anticancer treatments. These results were mainly obtained through our strategy of adenoviruses expressing dominant negative IGF-IR (IGF-IR/dn) against gastrointestinal cancers, including esophagus, stomach, colon, and pancreas. We also summarize a variety of strategies to interrupt the IGFs/IGF-IR axis and their preclinical experiences. Several mAbs and TKIs targeting IGF-IR have entered clinical trials, and early results have suggested that these agents have generally acceptable safety profiles as single agents. We summarize the advantages and disadvantages of each strategy and discuss the merits/demerits of dual targeting of IGF-IR and other growth factor receptors, including Her2 and the insulin receptor, as well as other alternatives and possible drug combinations. Thus, IGF-IR might be a candidate for a molecular therapeutic target in human GI carcinomas.

Roles of matrix metalloproteinases in cancer progression and their pharmacological targeting

Matrix metalloproteinases (MMPs) consist of a multigene family of zinc-dependent extracellular matrix (ECM) remodeling endopeptidases implicated in pathological processes, such as carcinogenesis. In this regard, their activity plays a pivotal role in tumor growth and the multistep processes of invasion and metastasis, including proteolytic degradation of ECM, alteration of the cell-cell and cell-ECM interactions, migration and angiogenesis. The underlying premise of the current minireview is that MMPs are able to proteolytically process substrates in the extracellular milieu and, in so doing, promote tumor progression. However, certain members of the MMP family exert contradicting roles at different stages during cancer progression, depending among other factors on the tumor stage, tumor site, enzyme localization and substrate profile. MMPs are therefore amenable to therapeutic intervention by synthetic and natural inhibitors, providing perspectives for future studies. Multiple therapeutic agents, called matrix metalloproteinase inhibitors (MMPIs) have been developed to target MMPs, attempting to control their enzymatic activity. Even though clinical trials with these compounds do not show the expected results in most cases, the field of MMPIs is ongoing. This minireview critically evaluates the role of MMPs in relation to cancer progression, and highlights the challenges, as well as future prospects, for the design, development and efficacy of MMPIs.

Association between a functional polymorphism (-1195T>C) in the IGFBP5 promoter and head and neck cancer risk

BACKGROUND

To the best of our knowledge, no studies to date have evaluated roles of insulin-like growth factor binding protein 5 (IGFBP5) polymorphisms in risk of squamous cell carcinoma of the head and neck (SCCHN).

METHODS

A hospital-based study of 1082 patients with SCCHN and 1120 cancer-free controls was performed to investigate associations between 2 functional polymorphisms, -1195T>C and -709G>C, in the IGFBP5 promoter region and SCCHN risk.

RESULTS

We demonstrated that the transcription factor, activator protein 1 (AP-1), differentially bound to T or C variants at -1195 in the promoter to regulate the IGFBP5 promoter activity and that the C variant genotypes were associated with deferential risk of late-stage SCCHN, compared to the TT genotype, particularly for human papillomavirus (HPV)-unrelated sites (adjusted odds ratio [OR], 2.21; 95% confidence interval [CI], 1.19-4.11 for CC vs TT).

CONCLUSION

The IGFBP5 -1195T>C polymorphism is functional and may potentially be a biomarker for susceptibility to late-stage SCCHN.

Physiology and pathophysiology of matrix metalloproteases

Matrix metalloproteases (MMPs) comprise a family of enzymes that cleave protein substrates based on a conserved mechanism involving activation of an active site-bound water molecule by a Zn(2+) ion. Although the catalytic domain of MMPs is structurally highly similar, there are many differences with respect to substrate specificity, cellular and tissue localization, membrane binding and regulation that make this a very versatile family of enzymes with a multitude of physiological functions, many of which are still not fully understood. Essentially, all members of the MMP family have been linked to disease development, notably to cancer metastasis, chronic inflammation and the ensuing tissue damage as well as to neurological disorders. This has stimulated a flurry of studies into MMP inhibitors as therapeutic agents, as well as into measuring MMP levels as diagnostic or prognostic markers. As with most protein families, deciphering the function(s) of MMPs is difficult, as they can modify many proteins. Which of these reactions are physiologically or pathophysiologically relevant is often not clear, although studies on knockout animals, human genetic and epigenetic, as well as biochemical studies using natural or synthetic inhibitors have provided insight to a great extent. In this review, we will give an overview of 23 members of the human MMP family and describe functions, linkages to disease and structural and mechanistic features. MMPs can be grouped into soluble (including matrilysins) and membrane-anchored species. We adhere to the 'MMP nomenclature' and provide the reader with reference to the many, often diverse, names for this enzyme family in the introduction.

PDEF is a negative regulator of colon cancer cell growth and migration

ETS is a family of transcriptional regulators with functions in most biological processes. Dysregulated ETS factor function leads to altered expression of multiple genes that play critical roles in many of the processes required for cancer progression. While the Ets family gene, prostate-derived ETS factor (PDEF), is expressed in epithelial tissues including prostate, breast, and colon, PDEF protein expression has been found to be reduced or lost during prostate and breast cancer progression. The goal of this study was to examine the expression and biologic impact of altered PDEF expression in colon cancer. PDEF mRNA and protein are not detectable in several colon-cancer-derived cell lines. Re-expression of PDEF in colon cancer cells inhibits growth and migration. Growth affects are due to altered cellular proliferation, indicated by increased altered cell population in G(1) and S phases of the cell cycle, as well as increased apoptosis. Relevant to its modulation of growth and migration phenotypes, PDEF expression resulted in altered expression of genes with established roles in cell cycle, motility, and invasion. Furthermore, chromatin immunoprecipitation studies show that p21 and urokinase plasminogen activator (uPA) are direct PDEF transcriptional targets. While non-tumor colon epithelium expresses PDEF mRNA and protein, the majority of tumors showed decreased mRNA and/or protein expression. In human tumor tissue samples, PDEF expression was inversely correlated with the expression levels of uPA. Collectively, the data support the model that PDEF is a negative regulator of tumor progression by modulating the expression of growth and migration promoting genes.

Role of insulin-like growth factor binding protein 2 in lung adenocarcinoma: IGF-independent antiapoptotic effect via caspase-3

Insulin-like growth factor (IGF) signaling plays a pivotal role in cell proliferation and mitogenesis. Secreted IGF-binding proteins (IGFBPs) are important modulators of IGF bioavailability; however, their intracellular functions remain elusive. We sought to assess the antiapoptotic properties of intracellular IGFBP-2 in lung adenocarcinomas. IGFBP-2 overexpression resulted in a decrease in procaspase-3 expression; however, it did not influence the phosphorylation status of either IGF receptor or its downstream targets, including Akt and extracellular signal-regulated kinase. Apoptosis induced by camptothecin was significantly inhibited by IGFBP-2 overexpression in NCI-H522 cells. Conversely, selective knockdown of IGFBP-2 using small-interfering RNA resulted in an increase in procaspase-3 expression and sensitization to camptothecin-induced apoptosis in NCI-H522 cells. LY294002, an inhibitor of phosphatidyl-inositol 3-kinase, caused a decrease in IGFBP-2 levels and enhanced apoptosis in combination with camptothecin. Immunohistochemistry demonstrated that intracellular IGFBP-2 was highly expressed in lung adenocarcinomas compared with normal epithelium. Intracellular IGFBP-2 and procaspase-3 were expressed in a mutually exclusive manner. These findings suggest that intracellular IGFBP-2 regulates caspase-3 expression and contributes to the inhibitory effect on apoptosis independent of IGF. IGFBP-2, therefore, may offer a novel therapeutic target and serve as an antiapoptotic biomarker for lung adenocarcinoma.

Disease-associated extracellular matrix suppresses osteoblastic differentiation of human periodontal ligament cells via MMP-1

Fibronectin (FN) fragments found in chronic inflammatory diseases, including periodontal disease and arthritis, may contribute to tissue destruction in part via induction of matrix metalloproteinases (MMPs). We previously showed that the 120-kDa FN fragment containing the central cell binding domain (120FN) dose dependently induces MMP-1 (collagenase-1) in human periodontal ligament (PDL) cells, whereas intact FN did not elicit this response. Recently, we found that an increase in MMP-1 expression is accompanied by a decreased osteoblastic phenotype in PDL cells. We hypothesized that 120FN inhibits osteoblastic differentiation of PDL cells by inducing MMP-1. Effects of increasing concentrations of 120FN on MMP-1 expression and on osteoblastic markers were assessed in cultured PDL cells using Western blotting, qRT-PCR, and collagen degradation and alkaline phosphatase (AP) activity assays. The 120FN dose dependently increased MMP-1 expression and activity, concomitant with a decrease in AP activity. The increase in collagenase activity was largely attributed to increased MMP-1 expression. Concurrent with the decrease in AP activity, the 120FN reduced baseline and dexamethasone-induced gene expression of specific osteoblastic markers, Runx2 and osteonectin, and diminished mineralized nodule formation. Finally, siRNA inhibition of 120FN-induced MMP-1 reduced collagenase expression and rescued the AP phenotype to baseline levels. These findings suggest that disease-associated 120FN, in addition to having direct effects on tissue destruction by upregulating MMPs, could contribute to disease progression by impeding osteoblastic differentiation of osteogenic PDL cells and, consequently, diminish bone regeneration.

Metalloproteases and the degradome

Metalloproteases comprise a heterogeneous group of proteolytic enzymes whose main characteristic is the utilization of a metal ion to polarize a water molecule and perform hydrolytic reactions. These enzymes represent the most densely populated catalytic class of proteases in many organisms and play essential roles in multiple biological processes. In this chapter, we will first present a general description of the complexity of metalloproteases in the context of the degradome, which is defined as the complete set of protease genes encoded by the genome of a certain organism. We will also discuss the functional relevance of these enzymes in a large variety of biological and pathological conditions. Finally, we will analyze in more detail three families of metalloproteases: ADAMs (a disintegrin and metalloproteinase), ADAMTSs (ADAMs with thrombospondin domains), and MMPs (matrix metalloproteinases) which have a growing relevance in a number of human pathologies including cancer, arthritis, neurodegenerative disorders, and cardiovascular diseases.

Identification of the amniotic fluid insulin-like growth factor binding protein-1 phosphorylation sites and propensity to proteolysis of the isoforms

Insulin-like growth factor binding protein-1 (IGFBP-1) is the major secreted protein of human decidual cells during gestation and, as a modulator of insulin-like growth factors or by independent mechanisms, regulates embryonic implantation and growth. The protein is phosphorylated and this post-translational modification is regulated in pregnancy and represents an important determinant of its biological activity. We have isolated, from human normal amniotic fluid collected in the weeks 16-18, the intact nonphosphorylated IGFBP-1 and five electrophoretically distinct phosphoisoforms and have determined their in vivo phosphorylation state. The unmodified protein was the most abundant component and mono-, bi-, tri- and tetraphosphorylated forms were present in decreasing amounts. The phosphorylation sites of IGFBP-1 were identified by liquid chromatography-tandem mass spectrometry analysis of the peptides generated with trypsin, chymotrypsin and Staphylococcus aureus V8 protease. Five serines were found to be phosphorylated and, of these, four are localized in the central, weakly conserved, region, at positions 95, 98, 101 and 119, whereas one, Ser169, is in the C-terminal domain. The post-translational modification predominantly involves the hydrophilic stretch of amino acids representing a potential PEST sequence (proline, glutamic acid, serine, threonine) and our results show that the phosphorylation state influences the propensity of IGFBP-1 to proteolysis.

Insulin-like growth factor-I receptor blockade reduces the invasiveness of gastrointestinal cancers via blocking production of matrilysin

Insulin-like growth factor-I receptor (IGF-IR) signaling is required for carcinogenicity and proliferation of gastrointestinal (GI) cancers. We have previously shown significant therapeutic activity for recombinant adenoviruses expressing dominant-negative insulin-like growth factor-I receptor (IGF-IR/dn), including suppression of tumor invasion. In this study, we sought to evaluate the mechanism of inhibition of invasion and the relationship between IGF-IR and matrix metalloproteinase (MMP) activity in GI carcinomas. We analyzed the role of IGF-IR on invasion in three GI cancer cell lines, colorectal adenocarcinoma, HT29; pancreatic adenocarcinoma, BxPC3 and gastric adenocarcinoma, MKN45, using a modified Boyden chamber method and subcutaneous xenografts in nude mice. The impact of IGF-IR signaling on the expression of MMPs and the effects of blockade of matrilysin or IGF-IR on invasiveness were assessed using recombinant adenoviruses, a tyrosine kinase inhibitor NVP-AEW541 and antisense matrilysin. Invasive subcutaneous tumors expressed several MMPs. IGF-IR/dn reduced the expression of these MMPs but especially matrilysin (MMP-7). Insulin-like growth factor (IGF) stimulated secretion of matrilysin and IGF-IR/dn blocked IGF-mediated matrilysin induction in three GI cancers. Both IGF-IR/dn and inhibition of matrilysin reduced in vitro invasion to the same degree. NVP-AEW541 also reduced cancer cell invasion both in vitro and in murine xenograft tumors via suppression of matrilysin. Thus, blockade of IGF-IR is involved in the suppression of cancer cell invasion through downregulation of matrilysin. Strategies of targeting IGF-IR may have significant therapeutic utility to prevent invasion and progression of human GI carcinomas.

Matrix metalloproteinase-9 interplays with the IGFBP2-IGFII complex to promote cell growth and motility in astrocytomas

Insulin-like growth factor II (IGFII) acts as a potent mitogen for several tumor types and has been reported to positively influence astrocytoma cell growth and motility. In the central nervous system, IGFII bioavailability is mainly modulated by insulin-like growth factor binding protein 2 (IGFBP2), which sequestrates IGFII and therefore prevents its interaction with the type-1 IGF receptor (IGF-IR). Proteolysis of IGFBP2 is the predominant mechanism recognized to reduce the binding affinity of IGFBP2 for IGFII, thus favoring dissociation of IGFII from the IGFBP2-IGFII complex. It is known that certain proteases involved in astrocytoma malignancy, such as matrix metalloproteinase-7 (MMP-7), plasmin, and cathepsin D, are able to proteolyze IGFBP2 in vitro. The present study aims to investigate whether other proteases expressed by astrocytomas, specifically MMP-2, MMP-9, and membrane-type 1 matrix metalloprotease (MT1-MMP), are able to proteolyze the IGFBP2-IGFII complex. Our results show the following: (i) MMP-9 proteolyzes the IGFBP2-IGFII complex in vitro, while MMP-2 and MT1-MMP do not; (ii) this MMP-9-induced IGFBP2-IGFII complex proteolysis releases free IGFII, which contributes to enhance the motility and the growth of LN229 astrocytoma cells. Furthermore, this study also highlights that the formation of the IGFBP2-IGFII complex inhibits IGFBP2's cell motility promoting effect by reducing the pool of free IGFBP2. In conclusion, MMP-9-induced IGFBP2 proteolysis may be regarded as an important post-translational event involved in astrocytoma aggressiveness. These new findings support drug targeting of MMP-9 as an interesting approach in the treatment of astrocytoma.

Expression, regulation and functional characterization of matrix metalloproteinase-3 of human trophoblast

MMP-3 has been detected in human placenta and reduced expression of the enzyme was observed in invasive trophoblasts of patients with severe preeclampsia. However, detailed expression pattern, regulation and biological properties of the placental protease have not been elucidated so far. RT-PCR analyses, Western blotting and enzyme activity assays revealed that pro- and active form of MMP-3 were predominantly expressed in purified first trimester villous trophoblasts, in invasive cytotrophoblasts of differentiating explant cultures and in trophoblastic SGHPL-4 cells. Accordingly, immunofluorescene of first trimester placental tissues detected MMP-3 mainly in villous and extravillous cytotrophoblasts. IL-1beta, an inducer of MMP-3 in decidual cells, increased secretion and activity of the protease in trophoblast supernatants in a dose- and time-dependent manner. IL-1beta-stimulated production of the enzyme was suppressed in the presence of inhibitors of MAPK and AKT signalling. Similar to recombinant MMP-3, MMP-3 in supernatants of IL-1beta-stimulated decidual stromal or SGHPL-4 cells degraded IGFBP-1 in vitro resulting in the appearance of cleavage products at approximately 25, 22, 17, 14 and 11kD. However, cleavage assays using recombinant MMP-2 suggested that the gelatinase may contribute to IGFBP-1 degradation in trophoblast supernatants. Despite its effects on MMP-3 expression IL-1beta failed to significantly alter invasion of SGHPL-4 cells through Matrigel-coated transwells. In conclusion, the data suggest that invasive trophoblast cell models secrete bioactive MMP-3. Inducible expression of the protease involves MAPK and AKT signalling. In addition to the decidua, MMP-3 of trophoblasts may contribute to the regulation of the IGF system by degrading IGFBP-1.

Genetic polymorphisms in the MMP-7 gene and breast cancer survival

Matrix metalloproteinase-7 (MMP-7) is a small secreted proteolytic enzyme with broad substrate specificity. Its expression has been shown to be associated with tumor invasion, metastasis and survival for a variety of cancers. We systematically evaluated single nucleotide polymorphisms (SNPs) in MMP-7 in relation to breast cancer survival in a large follow-up study. Included were 1,079 breast cancer cases that were recruited from 1996 to 1998 and followed for a median of 7.1 years as part of the Shanghai Breast Cancer Study (SBCS). Eleven SNPs, including 2 known functional promoter SNPs, were analyzed using the Affymetrix Targeted Genotyping System. Associations with survival were evaluated by Cox proportional hazards regression and Kaplan-Meier functions. Statistically significant associations with disease-free and/or overall survival (OS) were found for 5 polymorphisms; these associations were explained primarily by 2 SNPs (rs11568818 and rs11225297) that were in high linkage disequilibrium (LD) with the others. Patients homozygous for the rs11568818 rare allele (G) had a significantly worse prognosis (OS HR: 6.7, 95% CI: 2.4-18.6) than patients homozygous for the common allele (A). Significantly improved survival was seen for patients with the rs11225297 T allele, and this association occurred in a dose-response manner; patients with AT (OS HR: 0.7, 95% CI: 0.5-0.9) and TT (OS HR: 0.3, 95% CI: 0.1-0.8) fared better than patients with AA (p-value for trend: 0.001). Thus, common MMP-7 genetic polymorphisms were found to be significant determinants of survival among Chinese women with breast cancer.

Degradation of soluble VEGF receptor-1 by MMP-7 allows VEGF access to endothelial cells

Vascular endothelial growth factor (VEGF) signaling in endothelial cells serves a critical role in physiologic and pathologic angiogenesis. Endothelial cells secrete soluble VEGF receptor-1 (sVEGFR-1/sFlt-1), an endogenous VEGF inhibitor that sequesters VEGF and blocks its access to VEGF receptors. This raises the question of how VEGF passes through this endogenous VEGF trap to reach its membrane receptors on endothelial cells, a step required for VEGF-driven angiogenesis. Here, we show that matrix metalloproteinase-7 (MMP-7) degrades human sVEGFR-1, which increases VEGF bioavailability around the endothelial cells. Using a tube formation assay, migration assay, and coimmunoprecipitation assay with human umbilical vein endothelial cells (HUVECs), we show that the degradation of sVEGFR-1 by MMP-7 liberates the VEGF(165) isoform from sVEGFR-1. The presence of MMP-7 abrogates the inhibitory effect of sVEGFR-1 on VEGF-induced phosphorylation of VEGF receptor-2 on HUVECs. These data suggest that VEGF escapes the sequestration by endothelial sVEGFR-1 and promotes angiogenesis in the presence of MMP-7.

MMP-1 (collagenase-1) and MMP-13 (collagenase-3) differentially regulate markers of osteoblastic differentiation in osteogenic cells

Previous studies have demonstrated an inverse relationship between constitutive or stimulated collagenase expression and osteoblastic phenotype of osteogenic cells. However, the direct effects of cell-secreted collagenases on osteoblastic differentiation, and the precise contributions of the key collagenolytic MMPs, MMP-1 and -13 to the modulation of specific osteoblastic markers have not been elucidated. Early passage osteogenic human periodontal ligament (PDL) cells were exposed to exogenous collagenase-1 in the presence and absence of dexamethasone. Alternatively, endogenous collagenases were modulated by transfecting the cells with cDNA or siRNA to MMP-1 and/or -13. Specific osteoblastic markers and collagenase expression and activity were then assayed. Increasing concentrations of exogenous collagenase or endogenous MMP-1 and -13 produced a dose-dependent decrease in AP activity. Conversely, a dose-dependent increase in AP activity was observed with increasing concentrations of MMP-1 or MMP-13 siRNA. Overexpression of MMP-1 resulted in a significant decrease in Runx2, osteonectin (ON), osteopontin (OP), bone sialoprotein (BSP) and osteocalcin (OC), but an increase in osterix (Osx) mRNA levels. In contrast, knockdown of MMP-1 caused a significant increase in Runx2, ON, OP, BSP and OC levels and a decrease in Osx levels. MMP-13 overexpression resulted in diminished levels of Osx, OP and BSP, while its knockdown caused a significant increase in Osx and OP levels and a significant decrease in ON levels. The accretion of matrix molecules including collagen I(alpha1) in cell-matrix extracts paralleled the changes in their respective mRNAs. Simultaneous suppression of both MMP-1 and -13 resulted in significant increases in all osteoblastic markers assayed. MMP-1 and -13 differentially regulate osteoblastic markers and their combined suppression is important for the elaboration of an osteoblastic phenotype in PDL cells.

Plasma matrix metalloproteinase-7 as a metastatic marker and survival predictor in patients with renal cell carcinomas

We evaluated the clinical usefulness of plasma matrix metalloproteinase-7 (MMP-7) as a diagnostic and prognostic biomarker in patients with renal cell carcinoma (RCC). MMP-7 was quantified in plasma of 50 healthy subjects and 97 RCC patients using a Fluorokine MultiAnalyte Profiling assay. RCC patients were stratified into the following groups: without metastases (N0M0; n = 39), with lymph nodes (N1M0; n = 13), and with distant metastases (M1; n = 45). Diagnostic performance of MMP-7 was analyzed by the receiver operating characteristics (ROC) curve. Kaplan-Meier analysis and the Cox regression model were used to estimate the impact of MMP-7 on the cancer-specific survival outcome of RCC patients. MMP-7 was significantly higher in both metastatic groups N1M0 and M1 (medians, 3.82 and 3.34 microg/L) compared to N0M0 group or controls (medians, 1.85 and 1.64 microg/L; all P < 0.001). In ROC analysis, the area under the ROC curve of MMP-7 was 0.80 in the detection of metastases in RCC (P < 0.0001). In the Kaplan-Meier analysis, patients with MMP-7 above the 95th percentile of controls showed less favorable survival rates compared to those with normal MMP-7 (log-rank test, 15.7; P < 0.0001). High MMP-7 was associated with cancer-related mortality estimated by univariate Cox regression (risk ratio, 4.34, 95% CI, 1.12-10.6; P = 0.032). The multivariate Cox regression model determined MMP-7 (risk ratio, 2.70, 95% CI, 1.39-5.24; P = 0.003) and metastases (risk ratio, 5.81, 95% CI, 2.77-12.2; P < 0.0001) as independent determinants of cancer-related survival outcomes. In conclusion, increased plasma MMP-7 could be related to metastatic disease and poor prognosis in patients with RCC.

Matrix metalloproteinases 7 and 9 and their types 1 and 4 tissue inhibitors in tumors and plasma of patients with colorectal cancer

Enzyme immunoassays showed significantly elevated content of matrix metalloproteinase 7 and type 1 tissue inhibitor of metalloproteinases in tumors compared to adjacent histologically unchanged mucosa of patients with colorectal cancer; the levels of metalloproteinase 9 and type 4 tissue inhibitor of metalloproteinases were virtually the same in the tumors and mucosa. Plasma concentrations of the studied proteins did not correlate with their levels in the tumor, did not surpass the normal, and did not decease after removal of the primary tumor in the majority of patients.

Matrix metalloproteinase-2 regulates vascular patterning and growth affecting tumor cell survival and invasion in GBM

Glioblastoma multiforme (GBM) is one the most aggressive brain tumors due to the fast and invasive growth that is partly supported by the presence of extensive neovascularization. The matrix metalloproteinase MMP-2 has been associated with invasive and angiogenic properties in gliomas and is a marker of poor prognosis. Since MMP-2 is expressed in both tumor cells and endothelial cells in GBM, we generated genetically engineered MMP-2 knockout (MMP-2ko) GBM to examine the importance of the spatial expression of MMP-2 in tumor and/or normal host-derived cells. MMP-2-dependent effects appeared to be dose-dependent irrespective of its expression pattern. GBM completely devoid of MMP-2 exhibited markedly increased vascular density associated with vascular endothelial growth factor receptor 2 (VEGFR2) activation and enhanced vascular branching and sprouting. Surprisingly, despite the high vascular density, tumor cells were more prone to apoptosis, which led to prolonged survival of tumor-bearing mice, suggesting that the increased vascularity is not functional. Congruently, tumor vessels were poorly perfused, exhibited lower levels of VEGFR2, and did not undergo proper maturation because pericytes of MMP-2ko tumors were not activated and were less abundant. As a result of impaired and dysfunctional angiogenesis, MMP-2ko GBM became more invasive, predominantly by migrating along blood vessels into the brain parenchyma.

Activity of ulilysin, an archaeal PAPP-A-related gelatinase and IGFBP protease

Human growth and development are conditioned by insulin-like growth factors (IGFs), which have also implications in pathology. Most IGF molecules are sequestered by IGF-binding proteins (IGFBPs) so that exertion of IGF activity requires disturbance of these complexes. This is achieved by proteolysis mediated by IGFBP proteases, among which the best characterised is human PAPP-A, the first member of the pappalysin family of metzincins. We have previously identified and studied the only archaeal homologue found to date, Methanosarcina acetivorans ulilysin. This is a proteolytically functional enzyme encompassing a pappalysin catalytic domain and a pro-domain involved in maintenance of latency of the zymogen, proulilysin. Once activated, the protein hydrolyses IGFBP-2 to -6 and insulin chain beta in vitro. We report here that ulilysin is also active against several other substrates, viz (azo)casein, azoalbumin, and extracellular matrix components. Ulilysin has gelatinolytic but not collagenolytic activity. Moreover, the proteolysis-resistant skeletal proteins actin and elastin are also cleaved, as is fibrinogen, but not plasmin and alpha1-antitrypsin from the blood coagulation cascade. Ulilysin develops optimal activity at pH 7.5 and strictly requires peptide bonds preceding an arginine residue, as determined by means of a novel fluorescence resonance energy transfer assay, thus pointing to biotechnological applications as an enzyme complementary to trypsin.

Evidence supporting proteolytic cleavage of insulin-like growth factor binding protein-1 (IGFBP-1) protein in amniotic fluid

OBJECTIVE

The purpose of this study was to determine if: 1) insulin-like growth factor binding protein-1 (IGFBP-1) in amniotic fluid (AF) exhibited proteolytic cleavage in cases of intra-amniotic inflammation; and 2) if the matrix metalloproteinases (MMP-3, MMP-8, MMP-9) in AF are associated with the degradation of IGFBP-1 in AF.

METHODS

AF samples (n=20) were obtained from preterm gestations with and without intra-amniotic inflammation. The form of IGFBP-1 in AF was assessed by Western blot analysis and AF MMP-8 concentration was measured by ELISA. Densitometric analysis of Western blot was performed and the fragmented/intact IGFBP-1 ratio was calculated. Proteolysis of AF IGFBP-1 by MMPs was evaluated by incubating AF with exogenous human MMP-3, MMP-8 or MMP-9, and by incubating recombinant human IGFBP-1 in AF with and without inflammation.

RESULTS

1) IGFBP-1 was present in AF without inflammation as an intact form; however, the fragmented form was dominant in AF with inflammation; 2) the ratio of fragmented/intact IGFBP-1 was significantly higher in AF with inflammation than in AF without inflammation; 3) a higher ratio of fragmented/intact IGFBP-1 was associated with a higher concentration of MMP-8; 4) in-vitro proteolysis experiments showed that AF IGFBP-1 was degraded by exogenous human MMP-3, MMP-8 and MMP-9; 5) recombinant human IGFBP-1 was fragmented in AF with inflammation, but not in AF without inflammation.

CONCLUSION

The fragmented form of AF IGFBP-1 was significantly increased in AF with intra-amniotic inflammation, and MMPs produced in AF with intra-amniotic inflammation were associated with the proteolytic change of AF IGFBP-1.

Modeling growth factor activity during proinflammatory stress: methodological considerations in assessing cytokine modulation of IGF binding proteins released by cultured bovine kidney epithelial cells

The present research was conducted to model potential mechanisms through which IGFBPs might be affected by a key proinflammatory response initiating cytokine tumor necrosis factor (TNF-)-alpha. Madin-Darby bovine kidney epithelial (MDBK) cells, known to release IGFBPs in response to several stimuli, were grown under several conditions and challenged with forskolin (F) or recombinant TNF-alpha for 24h. Forskolin increased IGFBP-3 gene expression and media content of BP-3 protein. TNF-alpha increased basal and augmented F-mediated IGFBP-3 gene expression. However, TNF-alpha effects on the measurable media content of IGFBPs were influenced by culture conditions; in the absence of added protease inhibitors (PIs) or sufficient media albumin concentration (high BSA, 1mg/ml), the effect of TNF-alpha was to decrease (P<0.02) measurable IGFBPs. In the presence of PI and high BSA, media IGFBP-3 levels were shown to be increased by TNF-alpha consistent with the gene expression data. Changes in media IGFBP-3 protease activity were examined further to explain the observed effects of TNF-alpha on production and destruction of IGFBPs in media. When recombinant human IGFBP-3 (500 ng/ml) was added to PI-free, low BSA 100 microg/ml) media from TNF-treated MDBK cells, less than 10% of the BP-3 was recognizable by Western blot in 30 min; conversely, inclusion of High BSA and PI in media resulted in attenuation of the protease effect on the IGFBPs. The data suggest that the MDBK model of cellular response to proinflammatory stimulus is affected by culture conditions and that TNF-alpha affects media content of IGFBPs through effects on IGFBP gene expression coupled with degradation of IGFBPs via enhanced proteolytic enzyme release.

Modifying IGF1 activity: an approach to treat endocrine disorders, atherosclerosis and cancer

Insulin-like growth factor 1 (IGF1) is a polypeptide hormone that has a high degree of structural similarity to human proinsulin. Owing to its ubiquitous nature and its role in promoting cell growth, strategies to inhibit IGF1 actions are being pursued as potential adjunctive measures for treating diseases such as short stature, atherosclerosis and diabetes. In addition, most tumour cell types possess IGF1 receptors and conditions in the tumour microenvironment, such as hypoxia, can lead to enhanced responsiveness to IGF1. Therefore, inhibiting IGF1 action has been proposed as a specific mechanism for potentiating the effects of existing anticancer therapies or for directly inhibiting tumour cell growth.

Individual matrix metalloproteinases control distinct transcriptional responses in airway epithelial cells infected with Pseudomonas aeruginosa

Airway epithelium is the initial point of host-pathogen interaction in Pseudomonas aeruginosa infection, an important pathogen in cystic fibrosis and nosocomial pneumonia. We used global gene expression analysis to determine airway epithelial transcriptional responses dependent on matrilysin (matrix metalloproteinase 7 [MMP-7]) and stromelysin-2 (MMP-10), two MMPs induced by acute P. aeruginosa pulmonary infection. Extraction of differential gene expression (EDGE) analysis of gene expression changes in P. aeruginosa-infected organotypic tracheal epithelial cell cultures from wild-type, Mmp7-/-, and Mmp10-/- mice identified 2,091 matrilysin-dependent and 1,628 stromelysin-2-dependent genes that were differentially expressed. Key node network analysis showed that these MMPs controlled distinct gene expression programs involved in proliferation, cell death, immune responses, and signal transduction, among other host defense processes. Our results demonstrate discrete roles for these MMPs in regulating epithelial responses to Pseudomonas infection and show that a global genomics strategy can be used to assess MMP function.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

Glial activation and matrix metalloproteinase release in cerebral malaria

Although neurological symptoms associated with cerebral malaria (CM) are largely reversible, recent studies suggest that lasting neurological sequelae can occur. This may be especially true for children, in whom persistent deficits include problems with memory and attention. Because the malaria parasite is not thought to enter the brain parenchyma, lasting deficits are likely related to factors including the host response to disease. Studies with a rodent model, and with human postmortem tissue, suggest that glial activation occurs with CM. In this review, the authors will highlight studies focused on such activation in CM. Likely causes will be discussed, which include ischemia and activation of blood brain barrier endothelial cells. The potential consequences of glial activation will also be discussed, highlighting the possibility that glial-derived proteinases contribute to structural damage of the central nervous system (CNS). Of note, for the purposes of this focused review, glial activation will refer to the activation of astrocytes and microglial cells; discussion of oligodendroglial cells will not be included. In addition, although events thought to be critical to the pathogenesis of CM and glial activation will be covered, a comprehensive review of cerebral malaria will not be presented. Excellent reviews are already available, including Coltel et al (2004; Curr Neurovasc Res 1: 91-110), Medana and Turner (2006; Int J Parasitol 36: 555-568), and Hunt et al (2006; Int J Parasitol 36: 569-582).

The matrix metalloproteinases and CNS plasticity: an overview

The matrix metalloproteinases (MMPs) are expressed in response to pro-inflammatory stimuli and other triggers. The MMPs cleave numerous substrates including extracellular matrix components, cytokines and growth factors. In the CNS, while most studied in the context of disease, the many physiological functions of the MMPs are now becoming appreciated. This review provides an overview of the growing body of evidence for physiological roles of MMPs both in CNS development and in CNS plasticity in normal brain functioning, including learning and memory, as well as in CNS repair and reorganization as part of the neuroimmune response to injury.

Matrix metalloproteinase-7 triggers the matricrine action of insulin-like growth factor-II via proteinase activity on insulin-like growth factor binding protein 2 in the extracellular matrix

Many growth factors and cytokines are immobilized on the extracellular matrix (ECM) by binding to glycosaminoglycans and are stored in an inactive form in the cellular microenvironment. However, the mechanisms of ECM-bound growth factor or cytokine activation have not been well documented. We showed that the insulin-like growth factor type-1 receptor (IGF-1R) was rapidly phosphorylated after the addition of matrix metalloproteinase (MMP)-7 to a serum-starved human colon cancer cell line (HT29) and that phosphorylation was completely inhibited by an IGF-II neutralizing antibody. In the ECM of this cell line, IGF-II and IGF binding protein (BP)-2 coexisted, but IGFBP-2 disappeared from the ECM fraction after treatment with MMP-7 or heparinase III. On the other hand, in a cell line in which IGF-1R was overexpressed, IGF-1R was phosphorylated by supernatant from the MMP-7-treated ECM fraction of HT29 but not by that from a heparinase-III-treated ECM fraction. We also demonstrated that MMP-7 degrades IGFBP-2 in vitro at three cleavage sites (peptide bonds E(151)-L(152), G(175)-L(176) and K(181)-L(182)), which have not been documented previously. Taken together, these results demonstrate that MMP-7 generates bioactive IGF-II by degrading the IGF-II/IGFBP-2 complex binding to heparan sulfate proteoglycan in the ECM, resulting in IGF-II-induced signal transduction. This evidence indicates that some ECM-associated growth factors enhance their ability to bind to their receptors by some proteases in the tumor microenvironment. This mechanism of action ('protease-triggered matricrine') represents an attractive model for understanding ECM-tumor interactions.

The role of the IGF system in cancer growth and metastasis: overview and recent insights

IGF-I receptor (IGF-IR) signaling and functions are mediated through the activities of a complex molecular network of positive (e.g., type I IGF) and negative (e.g., the type II IGF receptor, IGF-IIR) effectors. Under normal physiological conditions, the balance between the expression and activities of these molecules is tightly controlled. Changes in this delicate balance (e.g., overexpression of one effector) may trigger a cascade of molecular events that can ultimately lead to malignancy. In recent years, evidence has been mounting that the IGF axis may be involved in human cancer progression and can be targeted for therapeutic intervention. Here we review old and more recent evidence on the role the IGF system in malignancy and highlight experimental and clinical studies that provide novel insights into the complex mechanisms that contribute to its oncogenic potential. Controversies arising from conflicting evidence on the relevance of IGF-IR and its ligands to human cancer are discussed. Our review highlights the importance of viewing the IGF axis as a complex multifactorial system and shows that changes in the expression levels of any one component of the axis, in a given malignancy, should be interpreted with caution and viewed in a wider context that takes into account the expression levels, state of activation, accessibility, and functionality of other interacting components. Because IGF targeting for anticancer therapy is rapidly becoming a clinical reality, an understanding of this complexity is timely because it is likely to have an impact on the design, mode of action, and clinical outcomes of newly developed drugs.

Hemopexin domains as multifunctional liganding modules in matrix metalloproteinases and other proteins

The heme-binding hemopexin consists of two, four-bladed propeller domains connected by a linker region. Hemopexin domains are found in different species on the phylogenetic tree and in the human species represented in hemopexin, matrix metalloproteinases (MMPs), vitronectin, and products of the proteoglycan 4 gene. Hemopexin and hemopexin domains of human proteins fulfill functions in activation of MMPs, inhibition of MMPs, dimerization, binding of substrates or ligands, cleavage of substrates, and endocytosis by low-density lipoprotein receptor-related protein-1 (LRP-1; CD91) and LRP-2 (megalin, GP330). Insights into the structures and functions of hemopexin (domains) form the basis for positive or negative interference with the formation of molecular complexes and hence, might be exploited therapeutically in inflammation, cancer, and wound healing.

Substrate specificity of a metalloprotease of the pappalysin family revealed by an inhibitor and a product complex

Human pappalysin-1 is a multi-domain metalloprotease engaged in the homeostasis of insulin-like growth factors and the founding member of the pappalysin family within the metzincin clan of metalloproteases. We have recently identified an archaeal relative, ulilysin, encompassing only the protease domain. It is a 262-residue active protease with a novel 3D structure with two subdomains separated by an active-site cleft. Despite negligible overall sequence similarity, noticeable similarity is found with other metzincin prototypes, adamalysins/ADAMs and matrix metalloproteinases. Ulilysin has been crystallised in a product complex with an arginine-valine dipeptide occupying the active-site S(1') and S(2') positions and in a complex with the broad-spectrum hydroxamic acid-based metalloprotease inhibitor, batimastat. This molecule inhibits mature ulilysin with an IC(50) value of 61 microM under the conditions assayed. The binding of batimastat to ulilysin evokes binding to vertebrate matrix metalloproteases but is much weaker. These data give insight into substrate specificity and mechanism of action and inhibition of the novel pappalysin family.

Molecular Analysis of Ulilysin, the Structural Prototype of a New Family of Metzincin Metalloproteases

The metzincin clan encompasses several families of zinc-dependent metalloproteases with proven function both in physiology and pathology. They act either as broad spectrum protein degraders or as sheddases, operating through limited proteolysis. Among the structurally uncharacterized metzincin families are the pappalysins, of which the most thoroughly studied member is human pregnancy-associated plasma protein A (PAPP-A), a heavily glycosylated 170-kDa multidomain protein specifically cleaving insulin-like growth factor (IGF)-binding proteins (IGFBPs). Proulilysin is a 38-kDa archaeal protein that shares sequence similarity with PAPP-A but encompasses only the pro-domain and the catalytic domain. It undergoes calcium-mediated autolytic activation, and the mature protein adopts a three-dimensional structure with two subdomains separated by an active site cleft containing the catalytic zinc ion. This structure is reminiscent of human members of the adamalysin/ADAMs (a disintegrin and a metalloprotease) family of metzincins. A bound dipeptide yields information on the substrate specificity of ulilysin, which specifically hydrolyzes IGFBP-2 to -6, insulin, and extracellular matrix proteins but not IGFBP-1 or IGF-II. Accordingly, ulilysin has higher proteolytic efficiency and a broader substrate specificity than human PAPP-A. The structure of ulilysin represents a prototype for the catalytic domain of pappalysins.

Role of matrix metalloproteinase-7 (matrilysin) in human cancer invasion, apoptosis, growth, and angiogenesis

Matrix metalloproteinase (MMP)-7, also known as matrilysin, is a "minimal domain MMP" that exhibits proteolytic activity against components of the extracellular matrix (ECM). Matrilysin is frequently overexpressed in human cancer tissues and is associated with cancer progression. Tumorigenesis is a multistep process involving cell growth, invasion, metastasis, and angiogenesis. Matrilysin has been shown to play important roles not only in degradation of ECM proteins, but also in the regulation of several biochemical processes such as activation, degradation, and shedding of non-ECM proteins. This minire-view provides a summary of the current literature on the roles of matrilysin in tumorigenesis with a focus on the roles of modifications of non-ECM proteins by matrilysin and other related MMPs in tumorigenesis. Proteolysis of insulin-like growth factor binding protein by matrilysin results in increased bioavailability of insulin-like growth factors and enhanced cellular proliferation. Matrilysin has also been implicated in the ectodomain shedding of several cell surface molecules. Heparin-binding epidermal growth factor precursor (proHB-EGF) is cleaved by matrilysin into mature HB-EGF, which promotes cellular proliferation. Membrane-bound Fas ligand (FasL) is cleaved into soluble FasL, which increases apoptosis of cells adjacent to tumor cells. E-cadherin is converted to soluble E-cadherin to promote invasion. Tumor necrosis factor (TNF)-alpha precursor is cleaved to release soluble TNF-alpha to increase apoptosis. We propose that these matrilysin-mediated pathways provide the necessary and logical mechanisms to promote cancer progression.