The Antitumor Properties of the α3(IV)-(185-203) Peptide from the NC1 Domain of Type IV Collagen (Tumstatin) Are Conformation-dependent

Bacteria-mediated tumor-targeted delivery of tumstatin (54-132) significantly suppresses tumor growth in mouse model by inhibiting angiogenesis and promoting apoptosis

Tumor growth is an angiogenesis-dependent process and accompanied by the formation of hypoxic areas. Tumstatin is a tumor-specific angiogenesis inhibitor that suppresses the proliferation and induces the apoptosis of tumorous vascular endothelial cells. VNP20009, an attenuated Salmonella typhimurium strain, preferentially accumulates in the hypoxic areas of solid tumors. In this study, a novel Salmonella-mediated targeted expression system of tumstatin (VNP-Tum5) was developed under the control of the hypoxia-induced J23100 promoter to obtain anti-tumor efficacy in mice. Treatment with VNP-Tum5 effectively suppressed tumor growth and prolonged survival in the mouse model of B16F10 melanoma. VNP-Tum5 exhibited a higher efficacy in inhibiting the proliferation and inducing the necrosis and apoptosis of B16F10 cells in vitro and in vivo compared with VNP (control). VNP-Tum5 significantly inhibited the proliferation and migration of mouse umbilical vascular endothelial cells to impede angiogenesis. VNP-Tum5 downregulated the expression of anti-vascular endothelial growth factor A, platelet endothelial cell adhesion molecule-1, phosphorylated phosphoinositide 3 kinase, and phosphorylated protein kinase B and upregulated the expression of cleaved-caspase 3 in tumor tissues. This study is the first to use tumstatin-transformed VNP20009 as a tumor-targeted system for treatment of melanoma by combining anti-tumor and anti-angiogenic effects.

Tumor Microenvironment: Extracellular Matrix Alterations Influence Tumor Progression

The tumor microenvironment (TME) is composed of various cell types embedded in an altered extracellular matrix (ECM). ECM not only serves as a support for tumor cell but also regulates cell-cell or cell-matrix cross-talks. Alterations in ECM may be induced by hypoxia and acidosis, by oxygen free radicals generated by infiltrating inflammatory cells or by tumor- or stromal cell-secreted proteases. A poorer diagnosis for patients is often associated with ECM alterations. Tumor ECM proteome, also named cancer matrisome, is strongly altered, and different ECM protein signatures may be defined to serve as prognostic biomarkers. Collagen network reorganization facilitates tumor cell invasion. Proteoglycan expression and location are modified in the TME and affect cell invasion and metastatic dissemination. ECM macromolecule degradation by proteases may induce the release of angiogenic growth factors but also the release of proteoglycan-derived or ECM protein fragments, named matrikines or matricryptins. This review will focus on current knowledge and new insights in ECM alterations, degradation, and reticulation through cross-linking enzymes and on the role of ECM fragments in the control of cancer progression and their potential use as biomarkers in cancer diagnosis and prognosis.

Tumstatin fragment selectively inhibits neutrophil infiltration in experimental asthma exacerbation

BACKGROUND

Asthma is a chronic inflammatory disease with structural changes present. Burgess and colleagues recently found tumstatin markedly reduced in adult asthmatic lung tissue compared with nonasthmatics. ECM fragments such as tumstatin are named matrikines and act independently of the parent molecule. The role of Col IV matrikines in neutrophil inflammation (eg. exacerbation in asthma) has not been investigated to date. Severe adult asthma phenotypes are dominated by neutrophilic inflammation and show a high frequency of severe exacerbations.

OBJECTIVE

This study sought to investigate the role of a novel active region within tumstatin (CP17) and its implication in neutrophil inflammatory responses related to asthma exacerbation.

METHODS

For reactive oxygen production, isolated neutrophils were preincubated with peptides or vehicle for 1 hour and stimulated (PMA). Luminescence signal was recorded (integration over 10 seconds) for 1.5 hours. Neutrophil migration was performed according to the SiMA protocol. Mice were sensitized to OVA/Alumn by intraperitoneal (i.p.) injections. Mice were then treated with CP17, vehicle (PBS) or scrambled peptide (SP17) after OVA exposure (days 27 and 28, polyI:C stimulation). All animals were killed on day 29 with lung function measurement, histology and lavage.

RESULTS

CP17 decreased total ROS production rate to 52.44% (0.5 μmol/L, P < 0.05 vs SP17), reduced the in vitro directionality (vs SP17, P = 1 × 10^-6 ) and migration speed (5 μmol/L, P = 1 × 10^-3 ). In vivo application of CP17 decreased neutrophil inflammation ~1.8-fold (P < 0.001 vs SP17) and reduced numbers of mucus-producing cells (-29%, P < 0.05).

CONCLUSION

CP17 reduced the ROS production rate, migrational speed and selectively inhibited neutrophil accumulation in the lung interstitium and lumen.

CLINICAL RELEVANCE

CP17 may serve as a potential precursor for drug development to combat overwhelming neutrophil inflammation.

Conformation-dependent binding of a Tetrastatin peptide to αvβ3 integrin decreases melanoma progression through FAK/PI3K/Akt pathway inhibition

Tetrastatin, a 230 amino acid sequence from collagen IV, was previously demonstrated to inhibit melanoma progression. In the present paper, we identified the minimal active sequence (QKISRCQVCVKYS: QS-13) that reproduced the anti-tumor effects of whole Tetrastatin in vivo and in vitro on melanoma cell proliferation, migration and invasion. We demonstrated that QS-13 binds to SK-MEL-28 melanoma cells through the α_vβ₃ integrin using blocking antibody and β3 integrin subunit siRNAs strategies. Relevant QS-13 conformations were extracted from molecular dynamics simulations and their interactions with α_Vβ₃ integrin were analyzed by docking experiments to determine the binding areas and the QS-13 amino acids crucial for the binding. The in silico results were confirmed by in vitro experiments. Indeed, QS-13 binding to SK-MEL-28 was dependent on the presence of a disulfide-bound as shown by mass spectroscopy and the binding site on α_Vβ₃ was located in close vicinity to the RGD binding site. QS-13 binding inhibits the FAK/PI₃K/Akt pathway, a transduction pathway that is largely involved in tumor cell proliferation and migration. Taken together, our results demonstrate that the QS-13 peptide binds α_vβ₃ integrin in a conformation-dependent manner and is a potent antitumor agent that could target cancer cells through α_Vβ₃.

Discovering Cell-Adhesion Peptides in Tissue Engineering: Beyond RGD

As an alternative to natural extracellular matrix (ECM) macromolecules, cell-adhesion peptides (CAPs) have had tremendous impact on the design of cell culture platforms, implants, and wound dressings. However, only a handful of CAPs have been utilized. The discrepancy in ECM composition strongly affects cell behavior, so it is paramount to reproduce such differences in synthetic systems. This Opinion article presents strategies inspired from high-throughput screening techniques implemented in drug discovery to exploit the potential of a growing CAP library. These strategies are expected to promote the use of a broader spectrum of CAPs, which in turn could lead to improved cell culture models, implants, and wound dressings.

Type XIX collagen: A new partner in the interactions between tumor cells and their microenvironment

Type XIX collagen is a minor collagen that is associated with the basement membrane zone that belongs to the FACIT family (Fibril-Associated Collagens with Interrupted Triple helices). The FACIT family is composed of type IX, XII, XIV, XVI, XX, XXI, XXII and XIX collagens, which share many highly conserved structural motifs: a short NC1 domain, a thrombospondin-like N-terminal domain (TSPN), and numerous cysteine residues. The main role of FACITs is to ensure the integrity and stability of the extracellular matrix and its fibrillar collagen network by regulating the formation and size of the collagen fibrils. Type XIX collagen was discovered in a human rhabdomyosarcoma cell line. The collagen α1(XIX) chain is composed of 5 triple-helical domains (COL) interrupted by 6 non-triple-helical (NC) domains with a short, C-terminal, 19 amino acid non-collagenous domain (NC1). This collagen is involved in the differentiation of muscle cells, central nervous system development, and formation of the esophagus. Type XIX collagen is associated with the basement membrane zone, like type XVIII and XV collagens. Its short NC1(XIX) C-terminal domain inhibits the migration and invasion of melanoma cells. It also exerts a strong anti-angiogenic effect by inhibiting MMP-14 and VEGF expression. NC1(XIX) binding to αvβ3 integrin decreases the phosphorylation of proteins involved in the FAK (Focal Adhesion Kinase)/PI3K (PhosphoInositide 3-Kinase)/Akt (protein kinase B)/mTOR (Mammalian Target Of Rapamycin) pathway. On the other hand, NC1(XIX) induces an increase in GSK3β activity by decreasing its level of phosphorylation. The inhibition of this pathway could explain the anti-tumor properties of the NC1(XIX) domain.

Extracellular Matrix Glycoprotein-Derived Synthetic Peptides Differentially Modulate Glioma and Sarcoma Cell Migration

Glycoproteins of the extracellular matrix (ECM) regulate proliferation, migration, and differentiation in numerous cell lineages. ECM functions are initiated by small peptide sequences embedded in large constituents that are recognized by specific cellular receptors. In this study, we have investigated the biological effects of peptides derived from collagen type IV and tenascin-C compared to the well-known RGD peptide originally discovered in fibronectin. The influence of glycoproteins and corresponding peptides on the migration of the glioma cell lines U-251-MG and U-373-MG and the sarcoma line S-117 was studied. When the cell lines were tested in a modified Boyden chamber assay on filters coated with the ECM glycoproteins, glioma cells showed a strong migration response on tenascin-C and the basal lamina constituent collagen IV, in contrast to S-117 cells. In order to identify relevant stimulatory motifs, peptides derived from fibronectin (6NHX-GRGDSF), tenascin-C (TN-C, VSWRAPTA), and collagen type IV (MNYYSNS) were compared, either applied in solution in combination with ECM glycoprotein substrates, in solution in the presence of untreated membranes, or coated on the filters of the Boyden chambers. Using this strategy, we could identify the novel tenascin-C-derived peptide motif VSWRAPTA as a migration stimulus for glioma cells. Furthermore, while kin peptides generally blocked the effects of the respective homologous ECM proteins, unexpected effects were observed in heterologous situations. There, in several cases, addition of soluble peptides strongly boosted the response to the coated ECM proteins. We propose that peptides may synergize or antagonize each other by stimulating different signaling pathways.

Matrikines from basement membrane collagens: a new anti-cancer strategy

BACKGROUND

Tumor microenvironment is a complex system composed of a largely altered extracellular matrix with different cell types that determine angiogenic responses and tumor progression. Upon the influence of hypoxia, tumor cells secrete cytokines that activate stromal cells to produce proteases and angiogenic factors. In addition to stromal ECM breakdown, proteases exert various pro- or anti-tumorigenic functions and participate in the release of various ECM fragments, named matrikines or matricryptins, capable to act as endogenous angiogenesis inhibitors and to limit tumor progression.

SCOPE OF REVIEW

We will focus on the matrikines derived from the NC1 domains of the different constitutive chains of basement membrane-associated collagens and mainly collagen IV.

MAJOR CONCLUSIONS

The putative targets of the matrikine control are the proliferation and invasive properties of tumor or inflammatory cells, and the angiogenic and lymphangiogenic responses. Collagen-derived matrikines such as canstatin, tumstatin or tetrastatin for example, decrease tumor growth in various cancer models. Their anti-cancer activities comprise anti-proliferative effects on tumor or endothelial cells by induction of apoptosis or cell cycle blockade and the induction of a loss of their migratory phenotype. They were used in various preclinical therapeutic strategies: i) induction of their overexpression by cancer cells or by the host cells, ii) use of recombinant proteins or synthetic peptides or structural analogues designed from the structure of the active sequences, iii) used in combined therapies with conventional chemotherapy or radiotherapy.

GENERAL SIGNIFICANCE

Collagen-derived matrikines strongly inhibited tumor growth in many preclinical cancer models in mouse. They constitute a new family of anti-cancer agents able to limit cancer progression. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

[Matrikines: a new anticancer therapeutic strategy]

Tumor microenvironment is a complex system composed of a largely altered extracellular matrix (ECM) with different cell types that determine the angiogenic response. Upon the influence of hypoxia, tumor cells secrete cytokines that activate stromal cells to produce proteases and angiogenic factors. The proteases degrade the stromal ECM and participate in the release of various ECM fragments, named matrikines or matricryptins, capable to control tumor invasion and metastasis dissemination. We will focus on the matrikines derived from the NC1 domains of the different constitutive chains of basement membrane-associated collagens and mainly collagen IV. The putative targets of the matrikine action are the proliferation and invasive properties of tumor or inflammatory cells, and the angiogenic and lymphangiogenic responses. For example, canstatin, tumstatin and tetrastatin, respectively derived from the NC1 domains of α2, α3 and α4 chains of collagen IV, inhibit in vivo tumor growth in various experimental cancer models. Their anti-cancer activity comprises an anti-proliferative effect on tumor cells and on endothelial cells by induction of cell apoptosis or cell cycle blockade and the induction of a loss of their migratory phenotype. Matrikines constitute a new family of potent anticancer agents that could be used under various therapeutic strategies: i) induction of their overexpression by cancer cells or by the host cells, ii) use of recombinant proteins or synthetic peptides or structural analogues designed from the structure of the active sequences. These matrikines could be used in combination with conventional chemotherapy or radiotherapy to limit tumor progression.

Tetrastatin, the NC1 domain of the α4(IV) collagen chain: a novel potent anti-tumor matrikine

BACKGROUND

NC1 domains from α1, α2, α3 and α6(IV) collagen chains were shown to exert anti-tumor or anti-angiogenic activities, whereas the NC1 domain of the α4(IV) chain did not show such activities so far.

METHODOLOGY/PRINCIPAL FINDINGS

We demonstrate in the present paper that the NC1 α4(IV) domain exerts a potent anti-tumor activity both in vitro and in an experimental human melanoma model in vivo. The overexpression of NC1 α4(IV) in human UACC-903 melanoma cells strongly inhibited their in vitro proliferative (-38%) and invasive (-52%) properties. MT1-MMP activation was largely decreased and its cellular distribution was modified, resulting in a loss of expression at the migration front associated with a loss of migratory phenotype. In an in vivo xenograft model in athymic nude mice, the subcutaneous injection of NC1 α4(IV)-overexpressing melanoma cells induced significantly smaller tumors (-80% tumor volume) than the Mock cells, due to a strong inhibition of tumor growth. Exogenously added recombinant human NC1 α4(IV) reproduced the inhibitory effects of NC1 α4(IV) overexpression in UACC-903 cells but not in dermal fibroblasts. An anti-αvβ3 integrin blocking antibody inhibited cell adhesion on recombinant human NC1 α4(IV) substratum. The involvement of αvβ3 integrin in mediating NC1 α4(IV) effect was confirmed by surface plasmon resonance (SPR) binding assays showing that recombinant human NC1 α4(IV) binds to αvβ3 integrin (K(D) = 148 ± 9.54 nM).

CONCLUSION/SIGNIFICANCE

Collectively, our results demonstrate that the NC1 α4(IV) domain, named tetrastatin, is a new endogenous anti-tumor matrikine.

Matrikines and the lungs

The extracellular matrix is a complex network of fibrous and nonfibrous molecules that not only provide structure to the lung but also interact with and regulate the behaviour of the cells which it surrounds. Recently it has been recognised that components of the extracellular matrix proteins are released, often through the action of endogenous proteases, and these fragments are termed matrikines. Matrikines have biological activities, independent of their role within the extracellular matrix structure, which may play important roles in the lung in health and disease pathology. Integrins are the primary cell surface receptors, characterised to date, which are used by the matrikines to exert their effects on cells. However, evidence is emerging for the need for co-factors and other receptors for the matrikines to exert their effects on cells. The potential for matrikines, and peptides derived from these extracellular matrix protein fragments, as therapeutic agents has recently been recognised. The natural role of these matrikines (including inhibitors of angiogenesis and possibly inflammation) make them ideal targets to mimic as therapies. A number of these peptides have been taken forward into clinical trials. The focus of this review will be to summarise our current understanding of the role, and potential for highly relevant actions, of matrikines in lung health and disease.

Characterization of Type I and IV Collagens by Raman Microspectroscopy: Identification of Spectral Markers of the Dermo-Epidermal Junction

Type I and IV collagens are important constituents of the skin. Type I collagen is found in all dermal layers in high proportion, while type IV collagen is localized in the basement membrane of the dermo-epidermal junction (DEJ). These proteins are strongly altered during aging or cancer progression. Although they possess amino acid compositions which, are close, they present also important structural differences inducing specific physicochemical properties. Raman spectroscopy is based on a nondestructive interaction of the light with the matter. This technique permits to probe the intrinsic molecular composition of the samples without staining or particular preparation. The aim of our research is to study the correlation between the molecular conformations of type I and IV collagens and their Raman features. We showed that signals specific of each protein can be revealed and that they translate structural differences between the two collagens. From this collagens spectral characterization, the analysis of skin sections also permitted to identify spectral markers of dermis, epidermis, and epidermis/dermis interface. These preliminary results represent basic data for further studies, particularly to probe skin molecular alterations induced by chronologic aging.

Integrin-mediated cell-matrix interaction in physiological and pathological blood vessel formation

Physiological as well as pathological blood vessel formation are fundamentally dependent on cell-matrix interaction. Integrins, a family of major cell adhesion receptors, play a pivotal role in development, maintenance, and remodeling of the vasculature. Cell migration, invasion, and remodeling of the extracellular matrix (ECM) are integrin-regulated processes, and the expression of certain integrins also correlates with tumor progression. Recent advances in the understanding of how integrins are involved in the regulation of blood vessel formation and remodeling during tumor progression are highlighted. The increasing knowledge of integrin function at the molecular level, together with the growing repertoire of integrin inhibitors which allow their selective pharmacological manipulation, makes integrins suited as potential diagnostic markers and therapeutic targets.

Neural differentiation regulated by biomimetic surfaces presenting motifs of extracellular matrix proteins

The interaction between cells and the extracellular matrix (ECM) is essential during development. To elucidate the function of ECM proteins on cell differentiation, we developed biomimetic surfaces that display specific ECM peptide motifs in a controlled manner. Presentation of ECM domains for collagen, fibronectin, and laminin influenced the formation of neurites by differentiating PC12 cells. The effect of these peptide sequences was also tested on the development of adult neural stem/progenitor cells. In this system, collagen I and fibronectin induced the formation of beta-III-tubulin positive cells, whereas collagen IV reduced such differentiation. Biomimetic surfaces composed of multiple peptide types enabled the combinatorial effects of various ECM motifs to be studied. Surfaces displaying combined motifs were often predictable as a result of the synergistic effects of ECM peptides studied in isolation. For example, the additive effects of fibronectin and laminin resulted in greater expression of beta-III-tubulin positive cells, whereas the negative effect of the collagen IV domain was canceled out by coexpression of collagen I. However, simultaneous expression of certain ECM domains was less predictable. These data highlight the complexity of the cellular response to combined ECM signals and the need to study the function of ECM domains individually and in combination.

The YSNSG cyclopeptide derived from tumstatin inhibits tumor angiogenesis by down-regulating endothelial cell migration

We previously demonstrated that the CNYYSNS peptide derived from tumstatin inhibited in vivo tumor progression. The YSNS motif formed a beta-turn crucial for biological activity. More recently, a YSNSG cyclopeptide with a constrained beta-turn on the YSNS residues was designed. Intraperitoneal administration of the YSNSG cyclopeptide inhibited in vivo melanoma progression more efficiently than the native linear peptide. In the present article, we showed that the YSNSG cyclopeptide also triggered an inhibition of in vivo tumor neovascularization and we further analyzed its in vitroantiangiogenic effect. The YSNSG cyclopeptide did not alter endothelial cell proliferation but inhibited cell migration by 83% in an in vitro wound healing model. The inhibition was mediated by a decrease in active MT1-MMP at the migration front as well as a decrease in u-PA and u-PAR expression. The cyclopeptide also altered beta1-integrin distribution in endothelial cell lamellipodia, induced a strong decrease in the phosphorylated focal adhesion kinase (p125(FAK)), disorganized F-actin stress fibers and decreased the number of lamellipodia, resulting in a non migratory phenotype. Our results confirm the YSNSG cyclopeptide as a potent antitumor agent, through both the inhibition of invasive properties of tumor cells and the antiangiogenic activity.

The anti-tumor properties of two tumstatin peptide fragments in human gastric carcinoma

AIM

The aim was to study the anti-tumor activities and mechanisms of two synthetic peptide fragments of tumstatin (alpha3 (IV) NC1 domain) in human gastric carcinoma cells in vitro and in vivo.

METHODS

MTT assay and cell cycle assay were used to study the anti-tumor and anti-angiogenic activities of two peptide fragments in vitro. Apoptosis induced by the two peptide fragments was demonstrated by TUNEL assay and morphological observation. The orthotopic tumor model was established to investigate the activities of two peptide fragments in vivo. Intratumor vascularization and the expressions of VEGF, bFGF, Fas, FasL, Bax, Bcl-2, and caspase 3 were determined using immunohistochemistry and Western blot analysis.

RESULTS

Peptide 19 inhibited SGC-7901 proliferation and induced apoptosis both in vitro and in vivo. Notably, peptide 21 suppressed the proliferation of HUVEC-12 cells in vitro. Each peptide arrested both cell lines at the G(0)/G(1) phase of the cell cycle, and they also synergistically suppressed in vitro and in vivo tumor growth. Immunohistochemistry and Western blot analysis revealed the strong expression of Fas, FasL and caspase 3 in orthotopic tumor tissues treated with peptide 19 alone or in combination with peptide 21. Decreased expressions of VEGF and bFGF and decreased microvessel density (MVD) in orthotopic tumor tissues were seen in mice treated with peptide 21 alone or in combination with peptide 19.

CONCLUSION

Two tumstatin peptide fragments facilitate two unique antitumor activities. Thus, they are drug candidates in the treatment of gastric carcinoma.

Update on Endogenous Inhibitors of Angiogenesis

Angiogenesis is regulated by a local balance between the levels of endogenous stimulators and inhibitors of angiogenesis. Understanding of the mechanism of angiogenesis has advanced significantly since the discovery of two members of the family of angiogenesis stimulators, i.e., vascular endothelial growth factor family proteins and angiopoietins. These factors act on endothelial cells to stimulate angiogenesis. In contrast, most of angiogenesis inhibitors do not seem to have such characteristics. Very few genes encoding molecules that selectively inhibit angiogenesis have been discovered. This review will focus on our current understanding of endogenous inhibitors of angiogenesis.

Targeting the early steps of Abeta16-22 protofibril disassembly by N-methylated inhibitors: a numerical study

Aggregation of the Abeta1-40/Abeta1-42 peptides is a key factor in Alzheimer's disease. Though the inhibitory effect of N-methylated Abeta16-22 (mAbeta16-22) peptides is well characterized in vitro, there is little information on how they disassemble full-length Abeta fibrils or block fibril formation. Here, we report coarse-grained implicit solvent molecular dynamics (MD) and replica exchange molecular dynamics (REMD) simulations on Abeta16-22 and mAbeta16-22 monomers, and then a preformed six-chain Abeta16-22 bilayer with either four copies of Abeta16-22 or four copies of mAbeta16-22. Our simulations show that the effect of N-methylation on mAbeta16-22 monomer is to reduce the density of compact forms. While 100 ns MD trajectories do not reveal any significant differences between the two ten-chain systems, the REMD simulations totaling 1 micros help understand the first steps of Abeta16-22 protofibril disassembly by N-methylated inhibitors. Notably, we find that mAbeta16-22 preferentially interacts with Abeta16-22 by blocking both beta-sheet extension and lateral association of layers, but also by intercalation of the inhibitors allowing sequestration of Abeta16-22 peptides. This third binding mode is particularly appealing for blocking Abeta fibrillogenesis.

Inhibitory effect of Abrus abrin-derived peptide fraction against Dalton's lymphoma ascites model

Peptides derived from larger molecules that are important modulators in cancer regression are becoming leads for development of therapeutic drugs. It has been reported that Abrus abrin, isolated from the seeds of Abrus precatorius, showed in vitro and in vivo antitumor properties by the induction of apoptosis. The present study was designed to evaluate the in vivo therapeutic effectiveness of abrin-derived peptide (ABP) fraction in Dalton's lymphoma (DL) mice model. The lethal dose (LD(50)) of ABP was found to be 2.25 mg/kg body weight and further the acute toxicity was determined with sublethal doses in normal mice. The acute toxicity like body weight, peripheral blood cell count, lympho-hematological and biochemical parameters remained unaffected till 200 microg/kg body weight of ABP. The sublethal doses of ABP showed very significant growth inhibitory properties in vivo DL mice model. There were 24%, 70.8% and 89.7% reductions in DL cell survival in 25, 50 and 100 microg/kg body weight of ABP, respectively. Analysis of the growth inhibitory mechanism in DL cells revealed nuclear fragmentation, and condensation with the appearance of the sub-G(0)/G(1) peak is indicative of apoptosis. Further, the Western blotting showed that apoptosis was mediated by the reduction in the ratio of Bcl-2 and Bax protein expression, and activation of caspase-3 through the release of cytochrome c in DL cells. Kaplan-Meier survival analysis showed an effective antitumor response (104.6 increase in life span (ILS) %) with a dose of 100 microg/kg body weight.

Replica exchange molecular dynamics simulations of coarse-grained proteins in implicit solvent

Current approaches aimed at determining the free energy surface of all-atom medium-size proteins in explicit solvent are slow and are not sufficient to converge to equilibrium properties. To ensure a proper sampling of the configurational space, it is preferable to use reduced representations such as implicit solvent and/or coarse-grained protein models, which are much lighter computationally. Each model must be verified, however, to ensure that it can recover experimental structures and thermodynamics. Here we test the coarse-grained implicit solvent OPEP model with replica exchange molecular dynamics (REMD) on six peptides ranging in length from 10 to 28 residues: two alanine-based peptides, the second beta-hairpin from protein G, the Trp-cage and zinc-finger motif, and a dimer of a coiled coil peptide. We show that REMD-OPEP recovers the proper thermodynamics of the systems studied, with accurate structural description of the beta-hairpin and Trp-cage peptides (within 1-2 A from experiments). The light computational burden of REMD-OPEP, which enables us to generate many hundred nanoseconds at each temperature and fully assess convergence to equilibrium ensemble, opens the door to the determination of the free energy surface of larger proteins and assemblies.

Changes in the localization of collagens IV and VIII in corneas obtained from patients with posterior polymorphous corneal dystrophy

Posterior polymorphous corneal dystrophy (PPCD) is a hereditary bilateral disorder affecting primarily the endothelium and Descemet's membrane (DM). The aim of this study was to determine the changes in the presence and localization of the alpha1-alpha6 collagen IV chains and alpha1, alpha2 collagen VIII chains in Czech patients with PPCD. Twelve corneal buttons from ten PPCD patients who underwent corneal grafting, as well as eight unaffected corneas, were used. Enzymatic indirect immunohistochemistry was performed on cryosections using antibodies against the alpha1-alpha6 collagen IV chains and alpha1, alpha2 collagen VIII chains. The intensity of the signal was examined separately in the basal membrane of the epithelium (BME), stroma and DM. More than 50% of PPCD specimens exhibited positivity for alpha1 and alpha2 collagen IV chains in the BME and in the posterior stroma, while no staining was detected in these areas in control specimens. The signal for the alpha1 and alpha2 collagen IV chains was more intense in DM of PPCD corneas compared to controls and it was shifted from the stromal side (in control tissue) to the endothelial side of DM (in the patients). A less intensive signal in PPCD corneas for the alpha3 and alpha5 chains in DM and an accumulation of alpha3-alpha5 in the posterior stroma in diseased corneas were the only differences in staining for the alpha3-alpha6 collagen IV chains. The alpha1 collagen VIII chain was detected on both the endothelial and the stromal sides of DM in 90% of patients with PPCD, compared with the prevailing localization on the stromal side of DM in control corneas. A change in the localization of the alpha2 collagen VIII chain in DM from vertically striated features in control specimens to double line positivity in the DM of PPCD corneas and positive staining in the posterior collagenous layer of four patients were also detected. In three PPCD patients a fibrous pannus located under the BME, positive for alpha1-alpha3, alpha5 collagen IV chains and alpha1 collagen VIII chain, was observed. The increased expression of the alpha1, alpha2 collagen IV and alpha1 collagen VIII chains and the change in their localization in DM may contribute to the increased endothelial proliferative capacity observed in PPCD patients.

Deletion 2q36.2q36.3 with multiple renal cysts and severe mental retardation

Interstitial 2q36 deletion is a rare event. We report on a patient with a de novo del(2)(q36.2q36.3) interstitial deletion of the long arm of chromosome 2 diagnosed by classical banding. The phenotype comprised facial dysmorphism, enlarged kidneys with multiple renal cysts, abnormal minora labia, asymmetric lower limbs with dysplastic patella, and severe mental retardation. By physical mapping, using array-comparative genomic hybridisation (CGH) confirmed by Fluorescent In Situ Hybridisation (FISH), the breakpoints of the deletion were mapped and the size of the deletions was measured: 5.61+/-0.19Mb. A skin biopsy was analysed using electronic microscopy showing an alteration of the structure and organisation of the dermal and peri-neuronal basement membrane. The relation between the phenotype and the deletion of both COL4A4 and COL4A3 genes, located in 2q36.3 loci, as well as the disruption of TRIP12 were discussed.

Energy landscapes of the monomer and dimer of the Alzheimer's peptide Abeta(1-28)

The cytotoxicity of Alzheimer's disease has been linked to the self-assembly of the 4042 amino acid of the amyloid-beta (Abeta) peptide into oligomers. To understand the assembly process, it is important to characterize the very first steps of aggregation at an atomic level of detail. Here, we focus on the N-terminal fragment 1-28, known to form fibrils in vitro. Circular dichroism and NMR experiments indicate that the monomer of Abeta(1-28) is alpha-helical in a membranelike environment and random coil in aqueous solution. Using the activation-relaxation technique coupled with the OPEP coarse grained force field, we determine the structures of the monomer and of the dimer of Abeta(1-28). In agreement with experiments, we find that the monomer is predominantly random coil in character, but displays a non-negligible beta-strand probability in the N-terminal region. Dimerization impacts the structure of each chain and leads to an ensemble of intertwined conformations with little beta-strand content in the region Leu17-Ala21. All these structural characteristics are inconsistent with the amyloid fibril structure and indicate that the dimer has to undergo significant rearrangement en route to fibril formation.

Inhibition of tumor angiogenesis by tumstatin: insights into signaling mechanisms and implications in cancer regression

Growing tumors develop additional new blood vessels to meet the demand for adequate nutrients and oxygen, a process called angiogenesis. Cancer is a highly complex disease promoted by excess angiogenesis; interfering with this process poses for an attractive approach for controlling tumor growth. This hypothesis led to the identification of endogenous angiogenesis inhibitors generated from type IV collagen, a major component of vascular basement membrane (VBM). Type IV collagen and the angiogenesis inhibitors derived from it are involved in complex roles, than just the molecular construction of basement membranes. Protease degradation of collagens in VBM occurs in various physiological and pathological conditions and produces several peptides. Some of these peptides are occupied in the regulation of functions conflicting from those of their original integral molecules. Tumstatin (alpha3(IV)NC1), a proteolytic C-terminal non-collagenous (NC1) domain from type IV collagen alpha3 chain has been highlighted recently because of its potential role in anti-angiogenesis, however its biological actions are not limited to these processes. alpha3(IV)NC1 inhibits proliferation by promoting endothelial cell apoptosis and suppresses diverse tumor angiogenesis, thus making it a potential candidate for future cancer therapy. The present review surveys the physiological functions of type IV collagen and discovery of alpha3(IV)NC1 as an antiangiogenic protein with a comprehensive overview of the knowledge gained by us towards understanding its signaling mechanisms.

Enhanced cell attachment using a novel cell culture surface presenting functional domains from extracellular matrix proteins

Many factors contribute to the creation and maintenance of a realistic environment for cell growth in vitro, e.g. the consistency of the growth medium, the addition of supplements, and the surface on which the cells grow. The nature of the surface on which cells are cultured plays an important role in their ability to attach, proliferate, migrate and function. Components of the extracellular matrix (ECM) are often used to coat glass or plastic surfaces to enhance cell attachment in vitro. Fragments of ECM molecules can be immobilised on surfaces in order to mimic the effects seen by whole molecules. In this study we evaluate the application of a novel technology for the immobilisation of functional domains of known ECM proteins in a controlled manner on a surface. By examining the adherence of cultured PC12 cells to alternative growth surfaces, we show that surfaces coated with motifs from collagen I, collagen IV, fibronectin and laminin can mimic surfaces coated with the corresponding whole molecules. Furthermore, we show that the adherence of cells can be controlled by modifying the hydropathic properties of the surface to either enhance or inhibit cell attachment. Collectively, these data demonstrate the application of a new technology to enable optimisation of cell growth in the tissue culture laboratory.

Signaling mechanisms of endogenous angiogenesis inhibitors derived from type IV collagen

Vascular basement membrane (VBM) derived molecules are regulators of certain biological activities such as cell growth, differentiation and angiogenesis. Angiogenesis is regulated by a systematic controlled balance between VBM derived antiangiogenic factors and proangiogenic growth factors. In the normal physiological state, equilibrium is maintained between the antiangiogenic and proangiogenic factors. The antiangiogenic factors (molecules), which are generated by the proteolytic cleavage of the VBM, include; α1 chain non-collagenous (NC1) domain of type XVIII collagen (endostatin) and the NC1 domains from the alpha chains of Type IV collagen considered as endogenous angiogenesis inhibitors. These collagen derived NC1 domains have a pivotal role in the regulation of tumor angiogenesis, thus making them attractive alternate candidates for cancer therapies. In this review we illustrate a comprehensive overview of the knowledge gained from the signaling mechanisms of Type IV collagen derived endogenous inhibitors in angiogenesis.

Structural and Antitumor Properties of the YSNSG Cyclopeptide Derived from Tumstatin

We previously demonstrated that the NC1[alpha3(IV)185-191] CNYYSNS peptide inhibited in vivo tumor progression. The YSNS motif formed a beta turn crucial for biological activity. The aim of the present study was to design a YSNSG cyclopeptide with a constrained beta turn on the YSNS residues more stable than CNYYSNS. By nuclear magnetic resonance and molecular modeling, we demonstrated that the YSNSG cyclopeptide actually adopted the expected beta-turn conformation. It promoted melanoma cell adhesion and prevented their adhesion to the native peptide. It inhibited in vitro cell proliferation and migration through Matrigel by downregulating proteolytic cascades. Moreover, intraperitoneal administration of the YSNSG cyclopeptide inhibited melanoma progression far more efficiently than the native peptide. The increased solubility and stability at low pH of the YSNSG cyclopeptide suggest this peptide as a potent antitumor therapeutic agent.

Structural basis for the functions of endogenous angiogenesis inhibitors

Tipping the angiogenic balance between pro- and antiangiogenic stimuli to favor vasculature induction and enhanced angiogenesis is a key event in the growth and progression of tumors. Recently, we demonstrated that the genetic loss of normal physiological levels of individual endogenous inhibitors of angiogenesis leads to a change in the balance between proangiogenic stimulators and their inhibitors, thus favoring enhanced angiogensis and increased tumor growth. Therefore, these endogenous angiogenesis inhibitors provide a physiological threshold against the induction of angiogenesis. The antiangiogenic activities of endostatin, tumstatin, and thrombospondin-1 are evaluated and correlated with their three-dimensional structure and active sites, deriving a structural basis for their activities. Collectively, structural analysis of all three inhibitors demonstrates that the active antiangiogenic sites on these molecules are exposed on the surface and available to bind their putative integrin receptors on proliferating endothelial cells.

Differential expression of basement membrane collagen-IV α1 to α6 chains during oral carcinogenesis

This study aimed to resolve if basement membrane (BM) collagen alpha chains undergo remodeling during oral carcinogenesis. Using immunohistochemistry and transmission electron microscopy, we found that BMs in oral epithelial dysplasias (OED: mild, n=10; moderate, n=10; severe, n=10) and carcinoma in situ (CIS) (n=10) differed from normal mucosa (n=6) and oral epithelial hyperplasia (n=5) in showing: (1) excessive lamina densa-like material ultrastructurally, and (2) stronger immunoexpression for alpha5(IV) than for alpha1(IV), alpha2(IV), and alpha6(IV) chains-findings that implicate these molecules' role as an adhesive template for the attachment and persistence of basal dysplastic cells. Incipient loss of BM integrity in CIS, where alpha5(IV)/alpha6(IV) chains were more frequently absent than alpha1(IV)/alpha2(IV) chains, suggests that alpha(IV) network disruption is crucial for progression of dysplastic cells into the extracellular compartment, marking transition into the invasive phase. In carcinomatous BM, the disappearance of alpha(IV) chains was more severe in poorly differentiated oral squamous cell carcinoma (OSCC) (n=10) than in well-differentiated OSCC (n=10). In all samples examined, alpha3(IV) and alpha4(IV) chains were absent. These findings taken together suggest that BM collagen-IV alpha chains undergo remodeling where selective increase and loss of these molecules are probably early and late events, respectively, during progression of oral dysplasia to cancer.

Vascular basement membrane-derived multifunctional peptide, a novel inhibitor of angiogenesis and tumor growth

Vascular basement membrane-derived multifunctional peptide (VBMDMP) gene (fusion gene of the human immunoglobulin G3 upper hinge region and two tumstatin-derived fragments) obtained by chemical synthesis was cloned into vector pUC19, and introduced into the expression vector pGEX-4T-1 to construct a prokaryotic expression vector pGEX-4T-1-VBMDMP. Recombinant VBMDMP produced in Escherichia coli has been shown to have significant activity of antitumor growth and antimetastasis in Lewis lung carcinoma transplanted into mouse C57Bl/6. In the present study, we have studied the ability of rVBMDMP to inhibit endothelial cell tube formation and proliferation, to induce apoptosis in vitro, and to suppress tumor growth in vivo. The experimental results showed that rVBMDMP potently inhibited proliferation of human endothelial (HUVEC-12) cells and human colon cancer (SW480) cells in vitro, with no inhibition of proliferation in Chinese hamster ovary (CHO-K1) cells. rVBMDMP also significantly inhibited human endothelial cell tube formation and suppressed tumor growth of SW480 cells in a mouse xenograft model. These results suggest that rVBMDMP is a powerful therapeutic agent for suppressing angiogenesis and tumor growth.

Exploring the early steps of amyloid peptide aggregation by computers

The assembly of normally soluble proteins into amyloid fibrils is a hallmark of neurodegenerative diseases. Because protein aggregation is very complex, involving a variety of oligomeric metastable intermediates, the detailed aggregation paths and structural characterization of the intermediates remain to be determined. Yet, there is strong evidence that these oligomers, which form early in the process of fibrillogenesis, are cytotoxic. In this paper, we review our current understanding of the underlying factors that promote the aggregation of peptides into amyloid fibrils. We focus here on the structural and dynamic aspects of the aggregation as observed in state-of-the-art computer simulations of amyloid-forming peptides with an emphasis on the activation-relaxation technique.

Tumstatin, the NC1 domain of alpha3 chain of type IV collagen, is an endogenous inhibitor of pathological angiogenesis and suppresses tumor growth

Angiogenesis, the formation of new blood vessels, is required for physiological development of vertebrates and repair of damaged tissue, but in the pathological setting contributes to progression of cancer. During tumor growth, angiogenesis is supported by up-regulation of angiogenic stimulators (pro-angiogenic) and down-regulation of angiogenic inhibitors (anti-angiogenic). The switch to the angiogenic phenotype (angiogenic switch) allows the tumors to grow and facilitate metastasis. The bioactive NC1 domain of type IV collagen alpha3 chain, called tumstatin, imparts anti-tumor activity by inducing apoptosis of proliferating endothelial cells. Tumstatin binds to alphaVbeta3 integrin via a mechanism independent of the RGD-sequence recognition and inhibits cap-dependent protein synthesis in the proliferating endothelial cells. The physiological level of tumstatin is controlled by matrix metalloproteinase-9, which most effectively cleaves it from the basement membrane and its physiological concentration in the circulation keeps pathological angiogenesis and tumor growth in check. These findings suggest that tumstatin functions as an endogenous inhibitor of pathological angiogenesis and functions as a novel suppressor of proliferating endothelial cells and growth of tumors.

Endogenous inhibitors of angiogenesis

Angiogenesis, the formation of new blood vessels, is required for many pathologic processes, including invasive tumor growth as well as physiologic organ/tissue maintenance. Angiogenesis during development and adulthood is likely regulated by a balance between endogenous proangiogenic and antiangiogenic factors. It is speculated that tumor growth requires disruption of such balance; thus, the angiogenic switch must be turned "on" for cancer progression. If the angiogenic switch needs to be turned on to facilitate the tumor growth, the question remains as to what the physiologic status of this switch is in the adult human body; is it "off," with inhibitors outweighing the stimulators, or maintained at a fine "balance," keeping the proangiogenic properties of many factors at a delicate "activity" balance with endogenous inhibitors of angiogenesis. The physiologic status of this balance is important to understand as it might determine an individual's predisposition to turn the switch on during pathologic events dependent on angiogenesis. Conceivably, if the physiologic angiogenesis balance in human population exists somewhere between off and even balance, an individual's capacity and rate to turn the switch on might reflect their normal physiologic angiogenic status. In this regard, although extensive knowledge has been gained in our understanding of endogenous growth factors that stimulate angiogenesis, the activities associated with endogenous inhibitors are poorly understood. In this review, we will present an overview of the knowledge gained in studies related to the identification and characterization of 27 different endogenous inhibitors of angiogenesis.

Canstatin acts on endothelial and tumor cells via mitochondrial damage initiated through interaction with alphavbeta3 and alphavbeta5 integrins

Canstatin, the noncollagenous domain of collagen type IV alpha-chains, belongs to a series of collagen-derived angiogenic inhibitors. We have elucidated the functional receptors and intracellular signaling induced by canstatin that explain its strong antitumor efficacy in vivo. For this purpose, we generated a canstatin-human serum albumin (CanHSA) fusion protein, employing the HSA moiety as an expression tag. We show that CanHSA triggers a crucial mitochondrial apoptotic mechanism through procaspase-9 cleavage in both endothelial and tumor cells, which is mediated through cross-talk between alphavbeta3- and alphavbeta5-integrin receptors. As a point of reference, we employed the first three kringle domains of angiostatin (K1-3), fused with HSA, which, in contrast to CanHSA, act only on endothelial cells through alphavbeta3-integrin receptor-mediated activation of caspase-8 alone, without ensuing mitochondrial damage. Taken together, these results provide insights into how canstatin might exert its strong anticancer effect.

Recombinant alpha2(IV)NC1 domain inhibits tumor cell-extracellular matrix interactions, induces cellular senescence, and inhibits tumor growth in vivo

Cellular interaction with the extracellular matrix is thought to be a critical event in controlling angiogenesis and tumor growth. In our previous studies, genetically distinct noncollagenous (NC) domains of type-IV collagen were shown to interact with integrin receptors expressed on the surface of endothelial cells. Moreover, these NC1 domains were shown to inhibit angiogenesis in vivo. Here, we provide evidence that a recombinant form of the alpha2(IV)NC1 domain of type-IV collagen could bind integrins alpha1beta1 and alphavbeta3 expressed on melanoma cells and inhibit tumor cell adhesion in a ligand-specific manner. Systemic administration of recombinant alpha2(IV)NC1 domain potently inhibited M21 melanoma tumor growth within full thickness human skin and exhibited a dose-dependent inhibition of tumor growth in nude mice. Interestingly, alpha2(IV)NC1 domain enhanced cellular senescence in tumor cells in vitro and in vivo. Taken together, these results suggest that recombinant alpha2(IV)NC1 domain is not only a potent anti-angiogenic reagent, but it also directly impacts tumor cell behavior. Thus, alpha2(IV)NC1 domain represents a potent inhibitor of tumor growth by impacting both endothelial and tumor cell compartments.

Matrikines in the regulation of extracellular matrix degradation

The term "matrikines" was coined for designating peptides liberated by partial proteolysis of extracellular matrix macromolecules, which are able to regulate cell activities. Among these peptides, some of them may modulate proliferation, migration, protease production, or apoptosis. In this review, we summarize the activity of matrikines derived from elastin and interstitial or basement membrane collagens on the regulation of matrix metalloproteinases expression and/or activation, and on the plasminogen/plasmin system. Due to their activity, matrikines may play a significant role in physiological or pathological processes such as wound healing or tumor invasion.

Matrix revolutions: ‘tails’ of basement-membrane components with angiostatic functions

Angiogenesis, the creation of neovasculature from native blood vessels, is a prerequisite for many physiological and pathological processes. Recently, C-terminal tail fragments of several basement-membrane proteins such as endostatin, tumstatin and endorepellin have been shown to inhibit angiogenesis. Although there seems to be little or no homology among them, a common theme is that these fragments modulate endothelial cells by distinct interactions with integrins and activate distinct intracellular signaling cascades that often lead to disruption of the actin cytoskeleton. In this article, we focus on recent advances regarding the mechanism of action of these angiostatic fragments and the emerging concept of similarities among them, with the underlying premise that appreciating these similarities might lead to improved therapeutics.

Nanoscale imaging and quantification of local proteolytic activity

Proteolytic cleavage of extracellular matrix (ECM) is a critical feature of tumor cell invasion, and affects cancer cell growth, differentiation, apoptosis, and migration. Malignant cells secrete most proteases as inactive proenzymes that undergo proteolytic cleavage for activation, and proteolytic activity is elevated in close proximity to these cells. Therefore, local activity rather than protease concentration determines ECM proteolysis. Precise quantification of local proteolytic activity, functional investigation, and high resolution imaging of morphological ECM alterations have proven difficult. In this study, we present a novel approach for measuring proteolytic activity in the microenvironment of cells by using atomic force microscopy (AFM). Amelanotic melanoma cells (A7-clone) were seeded on fluorescent gelatin or collagen-IV coatings. Proteolysis reduced fluorescence of these coatings. Fluorescence microscopy (FM) in combination with AFM was used to maneuver the AFM-tip to tumor cell induced proteolytic spots. AFM enabled nanoscale volume measurement, three-dimensional reconstruction of single proteins and demonstrated that ECM cleavage is restricted to the proteolytic microenvironment of cancer cells. This method detected significant decreases in molecular weight of protein clusters (-76.6%), matrix volume (-46.6%), and height (-38.1%) between intact and proteolyzed gelatin. Similar parameter changes were demonstrated without FM, by AFM-scanning gelatin in close proximity to invasive cells. Furthermore, AFM depicted significantly stronger local degradation of gelatin than collagen-IV by A7-cells. Taken together, AFM allows specific quantification and imaging of local proteolytic processes at a nanometer level, thus providing a unique method for the functional evaluation of invasiveness and metastatic potential of tumor cells in small scale samples.

Control of melanoma cell invasion by type IV collagen

Malignant melanoma is the leading cause of death from diseases of the skin. This review summarizes the data from the literature and our laboratory addressing the effects of type IV collagen on melanoma progression. Many different sequences from type IV collagen promote melanoma cell adhesion, migration and invasion. The triple helical conformation of the collagenous domain plays a critical role in some of these interactions. However, recent studies from our group demonstrated that a sequence from the alpha3(IV) NC1 domain inhibits melanoma cell proliferation, migration and invasion by decreasing MMP production and activation. Peptide sequences from the alpha1(IV), alpha2(IV) and alpha3(IV) chains named arresten, canstatin and tumstatin, respectively were shown to inhibit angiogenesis. Further investigations regarding the inhibitory effects of the alpha(IV) NC1 domains will have a paramount relevance for the design of efficient strategies to limit melanoma development.