The alpha 3(IV)185-206 peptide from noncollagenous domain 1 of type IV collagen interacts with a novel binding site on the beta 3 subunit of integrin alpha Vbeta 3 and stimulates focal adhesion kinase and phosphatidylinositol 3-kinase phosphorylation

Angiogenesis Inhibition by a Short 13 Amino Acid Peptide Sequence of Tetrastatin, the α4(IV) NC1 Domain of Collagen IV

Angiogenesis is defined as the formation of new capillaries by sprouting from the pre-existing microvasculature. It occurs in physiological and pathological processes particularly in tumor growth and metastasis. α1, α2, α3, and α6 NC1 domains from type IV collagen were reported to inhibit tumor angiogenesis. We previously demonstrated that the α4 NC1 domain from type IV collagen, named Tetrastatin, inhibited tumor growth in a mouse melanoma model. The inhibitory activity was located in a 13 amino acid sequence named QS-13. In the present paper, we demonstrate that QS-13 decreases VEGF-induced-angiogenesis in vivo using the Matrigel plug model. Fluorescence molecular tomography allows the measurement of a 65% decrease in Matrigel plug angiogenesis following QS-13 administration. The results are confirmed by CD31 microvessel density analysis on Matrigel plug slices. QS-13 peptide decreases Human Umbilical Vein Endothelial Cells (HUVEC) migration and pseudotube formation in vitro. Relevant QS-13 conformations were obtained from molecular dynamics simulations and docking. A putative interaction of QS-13 with α₅β₁ integrin was investigated. The interaction was confirmed by affinity chromatography, solid phase assay, and surface plasmon resonance. QS-13 binding site on α₅β₁ integrin is located in close vicinity to the RGD binding site, as demonstrated by competition assays. Collectively, our results suggest that QS-13 exhibits a mighty anti-angiogenic activity that could be used in cancer treatment and other pathologies with excessive angiogenesis such as hemangioma, psoriasis or diabetes.

Cellular Substrates for Cell-Based Tissue Engineering of Human Corneal Endothelial Cells

Corneal endothelial tissue engineering aims to find solutions for blindness due to endothelial dysfunction. A suitable combination of endothelial cells, substrates and environmental cues should be deployed for engineering functional endothelial tissues. This manuscript reviews up-to-date topics of corneal endothelial tissue engineering with special emphasis on biomaterial substrates and their properties, efficacy, and mechanisms of supporting functional endothelial cells in vitro.

New Insights into the Role of Basement Membrane-Derived Matricryptins in the Heart

The extracellular matrix (ECM), which contributes to structural homeostasis as well as to the regulation of cellular function, is enzymatically cleaved by proteases, such as matrix metalloproteinases and cathepsins, in the normal and diseased heart. During the past two decades, matricryptins have been defined as fragments of ECM with a biologically active cryptic site, namely the 'matricryptic site,' and their biological activities have been initially identified and clarified, including anti-angiogenic and anti-tumor effects. Thus, matricryptins are expected to be novel anti-tumor drugs, and thus widely investigated. Although there are a smaller number of studies on the expression and function of matricryptins in fields other than cancer research, some matricryptins have been recently clarified to have biological functions beyond an anti-angiogenic effect in heart. This review particularly focuses on the expression and function of basement membrane-derived matricryptins, including arresten, canstatin, tumstatin, endostatin and endorepellin, during cardiac diseases leading to heart failure such as cardiac hypertrophy and myocardial infarction.

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.

Regulation of spermatogenesis by a local functional axis in the testis: role of the basement membrane-derived noncollagenous 1 domain peptide

Spermatogenesis takes place in the epithelium of the seminiferous tubules of the testes, producing millions of spermatozoa per day in an adult male in rodents and humans. Thus, multiple cellular events that are regulated by an array of signaling molecules and pathways are tightly coordinated to support spermatogenesis. Here, we report findings of a local regulatory axis between the basement membrane (BM), the blood-testis barrier (BTB), and the apical ectoplasmic specialization (apical ES; a testis-specific, actin-rich adherens junction at the Sertoli cell-spermatid interface) to coordinate cellular events across the seminiferous epithelium during the epithelial cycle. In short, a biologically active fragment, noncollagenous 1 (NC1) domain that is derived from collagen chains in the BM, was found to modulate cell junction dynamics at the BTB and apical ES. NC1 domain from the collagen α3(IV) chain was cloned into a mammalian expression vector, pCI-neo, with and without a collagen signal peptide. We also prepared a specific Ab against the purified recombinant NC1 domain peptide. These reagents were used to examine whether overexpression of NC1 domain with high transfection efficacy would perturb spermatogenesis, in particular, spermatid adhesion (i.e., inducing apical ES degeneration) and BTB function (i.e., basal ES and tight junction disruption, making the barrier leaky), in the testis in vivo We report our findings that NC1 domain derived from collagen α3(IV) chain-a major structural component of the BM-was capable of inducing BTB remodeling, making the BTB leaky in studies in vivo Furthermore, NC1 domain peptide was transported across the epithelium via a microtubule-dependent mechanism and is capable of inducing apical ES degeneration, which leads to germ cell exfoliation from the seminiferous epithelium. Of more importance, we show that NC1 domain peptide exerted its regulatory effect by disorganizing actin microfilaments and microtubules in Sertoli cells so that they failed to support cell adhesion and transport of germ cells and organelles (e.g., residual bodies, phagosomes) across the seminiferous epithelium. This local regulatory axis between the BM, BTB, and the apical ES thus coordinates cellular events that take place across the seminiferous epithelium during the epithelial cycle of spermatogenesis.-Chen, H., Mruk, D. D., Lee, W. M., Cheng, C. Y. Regulation of spermatogenesis by a local functional axis in the testis: role of the basement membrane-derived noncollagenous 1 domain peptide.

The anti-tumor NC1 domain of collagen XIX inhibits the FAK/ PI3K/Akt/mTOR signaling pathway through αvβ3 integrin interaction

Type XIX collagen is a minor collagen associated with basement membranes. It was isolated for the first time in a human cDNA library from rhabdomyosarcoma and belongs to the FACITs family (Fibril Associated Collagens with Interrupted Triple Helices). Previously, we demonstrated that the NC1 domain of collagen XIX (NC1(XIX)) exerts anti-tumor properties on melanoma cells by inhibiting their migration and invasion. In the present work, we identified for the first time the integrin αvβ3 as a receptor of NC1(XIX). Moreover, we demonstrated that NC1(XIX) inhibits the FAK/PI3K/Akt/mTOR pathway, by decreasing the phosphorylation and activity of the major proteins involved in this pathway. On the other hand, NC1(XIX) induced an increase of GSK3β activity by decreasing its degree of phosphorylation. Treatments targeting this central signaling pathway in the development of melanoma are promising and new molecules should be developed. NC1(XIX) seems to have the potential for the design of new anti-cancer drugs.

Matricryptins Network with Matricellular Receptors at the Surface of Endothelial and Tumor Cells

The extracellular matrix (ECM) is a source of bioactive fragments called matricryptins or matrikines resulting from the proteolytic cleavage of extracellular proteins (e.g., collagens, elastin, and laminins) and proteoglycans (e.g., perlecan). Matrix metalloproteinases (MMPs), cathepsins, and bone-morphogenetic protein-1 release fragments, which regulate physiopathological processes including tumor growth, metastasis, and angiogenesis, a pre-requisite for tumor growth. A number of matricryptins, and/or synthetic peptides derived from them, are currently investigated as potential anti-cancer drugs both in vitro and in animal models. Modifications aiming at improving their efficiency and their delivery to their target cells are studied. However, their use as drugs is not straightforward. The biological activities of these fragments are mediated by several receptor families. Several matricryptins may bind to the same matricellular receptor, and a single matricryptin may bind to two different receptors belonging or not to the same family such as integrins and growth factor receptors. Furthermore, some matricryptins interact with each other, integrins and growth factor receptors crosstalk and a signaling pathway may be regulated by several matricryptins. This forms an intricate 3D interaction network at the surface of tumor and endothelial cells, which is tightly associated with other cell-surface associated molecules such as heparan sulfate, caveolin, and nucleolin. Deciphering the molecular mechanisms underlying the behavior of this network is required in order to optimize the development of matricryptins as anti-cancer agents.

Multilevel regulation of matrix metalloproteinases in tissue homeostasis indicates their molecular specificity in vivo

The matrix metalloproteinases (MMPs) play a crucial role in irreversible remodeling of the extracellular matrix (ECM) in normal homeostasis and pathological states. Accumulating data from various studies strongly suggest that MMPs are tightly regulated, starting from the level of gene expression all the way to zymogen activation and endogenous inhibition, with each level controlled by multiple factors. Recent in vivo findings indicate that cell-ECM and cell-cell interactions, as well as ECM bio-active products, contribute an additional layer of regulation at all levels, indicating that individual MMP expression and activity in vivo are highly coordinated and tissue specific processes.

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.

A new anti-tumor strategy based on in vivo tumstatin overexpression after plasmid electrotransfer in muscle

The NC1 domains from the different α(IV) collagen chains were found to exert anti-tumorigenic and/or anti-angiogenic activities. A limitation to the therapeutic use of these matrikines is the large amount of purified recombinant proteins, in the milligram range in mice that should be administered daily throughout the experimental procedures. In the current study, we developed a new therapeutic approach based on tumstatin (NC1α3(IV)) overexpression in vivo in a mouse melanoma model. Gene electrotransfer of naked plasmid DNA (pDNA) is particularly attractive because of its simplicity, its lack of immune responsiveness and its safety. The pDNA electrotransfer in muscle mediates a substantial gene expression that lasts several months. A pVAX1© vector containing the tumstatin cDNA was injected into the legs of C57BL/6 mice and submitted to electrotranfer. Sera were collected at different times and tumstatin was quantified by ELISA. Tumstatin secretion reached a plateau at day 21 with an expression level of 12 μg/mL. For testing the effects of tumstatin expression on tumor growth in vivo, B16F1 melanoma cells were subcutaneously injected in mice 7 days after empty pVAX1© (Mock) or pVAX1©-tumstatin electrotransfer. Tumstatin expression triggered a large decrease in tumor growth and an increase in mouse survival. This new therapeutic approach seems promising to inhibit tumor progression in vivo.

Arresten, a collagen-derived angiogenesis inhibitor, suppresses invasion of squamous cell carcinoma

The turnover of extracellular matrix liberates various cryptic molecules with novel biological activity. Among these are the collagen-derived anti-angiogenic fragments, some of which are suggested to affect carcinoma cells also directly. Arresten is an endogenous angiogenesis inhibitor that is derived from the non-collagenous domain of the basement membrane collagen IV α1 chain. As the mere prevention of tumor angiogenesis leads to hypoxia that can result in selection of more aggressive cell types and reduces the efficacy of chemotherapy, we aimed here to elucidate how arresten influences the aggressive human carcinoma cells. Arresten efficiently inhibited migration and invasion of HSC-3 tongue carcinoma cells in culture and in an organotypic model. Subcutaneous Arr-HSC xenografts grew markedly more slowly in nude mice and showed reduced tumor cell proliferation, vessel density and local invasiveness. In the organotypic assay, HSC-3 cells overproducing arresten (Arr-HSC) showed induction of cell death. In monolayer culture the Arr-HSC cells grew in aggregated cobblestone-like clusters and, relative to the control cells, showed increased expression and localization of epithelial marker E-cadherin in cell-cell contacts. Application of electric cell-substrate impedance sensing (ECIS) further supported our observations on altered morphology and motility of the Arr-HSC cells. Administration of a function-blocking α1 integrin antibody abolished the impedance difference between the Arr-HSC and control cells suggesting that the effect of arresten on promotion of HSC-3 cell-cell contacts and cell spreading is at least partly mediated by α1β1 integrin. Collectively, our data suggest novel roles for arresten in the regulation of oral squamous carcinoma cell proliferation, survival, motility and invasion through the modulation of cell differentiation state and integrin signaling.

[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.

Regulation of endothelial cell functions by basement membrane- and arachidonic acid-derived products

Angiogenesis, the formation of new blood vessels from preexisting vasculature, is required for normal physiological as well as pathological events. The angiogenic process requires endothelial cells to proliferate, migrate, and undergo tubulogenesis. These multistep processes necessitate secretion of pro-angiogenic growth factors, activation of specific intracellular signaling, and interaction of endothelial cells with basement membrane (BM) extracellular matrix components. The generation and release of angiogenic molecules are highly regulated and are influenced by numerous factors, including BM-derived fragments, proteolytic enzymes, as well as metabolites of arachidonic acid (AA). The interactions between these key modulators of angiogenesis is extremely complex, as AA metabolites can regulate the synthesis of soluble angiogenic factors, BM components, as well as enzymes capable of cleaving BM components, which result in the generation of pro- and/or anti-angiogenic products. Furthermore, some BM-derived fragments can alter the expression of AA-converting enzymes and consequently the synthesis of angiogenic factors. In this review we describe the relationship between BM components and AA metabolites with respect to the regulation of endothelial cell functions in health and disease.

Interaction of Xiphophorus and murine Fyn with focal adhesion kinase

The Src family kinase/Focal Adhesion Kinase (FAK) complex is a signaling platform playing a crucial role in transformation downstream of oncogenic growth factor receptors. In the case of melanoma in Xiphophorus fish, the oncogenic EGF receptor orthologue Xiphophorus melanoma receptor kinase (Xmrk) effects continuous activation of the Src family kinase Fyn, but not of the other family members Src or Yes. Here, Fyn is strongly involved in promoting many tumorigenic events. Although Fyn is expressed in most mammalian tissues, there are only few reports of its involvement in the development of solid tumors. To find out whether the prominent role of Xiphophorus Fyn is based on an altered binding to its important binding partner FAK when compared to its mammalian Fyn counterparts, we performed yeast-two-hybrid analyses. We compared Xiphophorus and murine Fyn with respect to their binding to full-length and truncated FAK constructs. We found that interaction with FAK occurs similarly for Xiphophorus and mouse Fyn. Both phosphorylated FAK residue Y397 and FAK proline-rich domain are involved in Fyn binding. We also found interaction of FAK and Fyn in human melanoma cell lines. These data suggest a possible, yet unrecognized role of Fyn in the tumorigenesis of human melanoma, too.

The CXC-chemokine CXCL4 interacts with integrins implicated in angiogenesis

The human CXC-chemokine CXCL4 is a potent inhibitor of tumor-induced angiogenesis. Considering that CXCL4 is sequestered in platelet alpha-granules and released following platelet activation in the vicinity of vessel wall injury, we tested the hypothesis that CXCL4 might function as a ligand for integrins. Integrins are a family of adhesion receptors that play a crucial role in angiogenesis by regulating early angiogenic processes, such as endothelial cell adhesion and migration. Here, we show that CXCL4 interacts with alphavbeta3 on the surface of alphavbeta3-CHO. More importantly, human umbilical vein endothelial cells adhere to immobilized CXCL4 through alphavbeta3 integrin, and also through other integrins, such as alphavbeta5 and alpha5beta1. We further demonstrate that CXCL4-integrin interaction is of functional significance in vitro, since immobilized CXCL4 supported endothelial cell spreading and migration in an integrin-dependent manner. Soluble CXCL4, in turn, inhibits integrin-dependent endothelial cell adhesion and migration. As a whole, our study identifies integrins as novel receptors for CXCL4 that may contribute to its antiangiogenic effect.

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.

Mammalian collagen IV

Four decades have passed since the first discovery of collagen IV by Kefalides in 1966. Since then collagen IV has been investigated extensively by a large number of research laboratories around the world. Advances in molecular genetics have resulted in identification of six evolutionary related mammalian genes encoding six different polypeptide chains of collagen IV. The genes are differentially expressed during the embryonic development, providing different tissues with specific collagen IV networks each having unique biochemical properties. Newly translated alpha-chains interact and assemble in the endoplasmic reticulum in a chain-specific fashion and form unique heterotrimers. Unlike most collagens, type IV collagen is an exclusive member of the basement membranes and through a complex inter- and intramolecular interactions form supramolecular networks that influence cell adhesion, migration, and differentiation. Collagen IV is directly involved in a number of genetic and acquired disease such as Alport's and Goodpasture's syndromes. Recent discoveries have also highlighted a new and direct role for collagen IV in the development of rare genetic diseases such as cerebral hemorrhage and porencephaly in infants and hemorrhagic stroke in adults. Years of intensive investigations have resulted in a vast body of information about the structure, function, and biology of collagen IV. In this review article, we will summarize essential findings on the structural and functional relationships of different collagen IV chains and their roles in health and disease.

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.

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.

Integrin alpha3beta1, a novel receptor for alpha3(IV) noncollagenous domain and a trans-dominant Inhibitor for integrin alphavbeta3

Exogenous soluble human alpha3 noncollagenous (NC1) domain of collagen IV inhibits angiogenesis and tumor growth. These biological functions are attributed to the binding of alpha3NC1 to integrin alphavbeta3. However, in some tumor cells that express integrin alphavbeta3, the alpha3NC1 domain does not inhibit proliferation, suggesting that integrin alphavbeta3 expression is not sufficient to mediate the anti-tumorigenic activity of this domain. Therefore, in the present study, we searched for novel binding receptors for the soluble alpha3NC1 domain in cells lacking alphavbeta3 integrin. In these cells, soluble alpha3NC1 bound integrin alpha3beta1; however, unlike alphavbeta3, alpha3beta1 integrin did not mediate cell adhesion to immobilized alpha3NC1 domain. Interestingly, in cells lacking integrin alpha3beta1, adhesion to the alpha3NC1 domain was enhanced due to activation of integrin alphavbeta3. These findings indicate that integrin alpha3beta1 is a receptor for the alpha3NC1 domain and transdominantly inhibits integrin alphavbeta3 activation. Thus integrin alpha3beta1, in conjunction with integrin alphavbeta3, modulates cellular responses to the alpha3NC1 domain, which may be pivotal in the mechanism underpinning its anti-angiogenic and anti-tumorigenic activities.

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.

A tripeptide mimetic of von Willebrand factor residues 981-983 enhances platelet adhesion to fibrinogen by signaling through integrin alpha(IIb)beta3

BACKGROUND

RGD is a major recognition sequence for ligands of platelet alpha(IIb)beta3.

OBJECTIVE AND METHODS

To identify potential binding sites for alpha(IIb)beta3 apart from RGD, we screened phage display libraries by blocking the enrichment of RGD-containing phages with a GRGDS peptide and identified a novel integrin recognition tripeptide sequence, VPW.

RESULTS

Platelets adhered to an immobilized cyclic VPW containing peptide in a alpha(IIb)beta3-dependent manner; platelets and alpha(IIb)beta3-expressing CHO cells adhered faster to immobilized alpha(IIb)beta3-ligands in the presence of soluble VPW. In platelets adhering to fibrinogen, VPW accelerated the activation of the tyrosine kinase Syk which controls cytoskeletal rearrangements. In alpha(IIb)beta3-expressing CHO cells, VPW induced a faster formation of stress fibers. Sequence alignment positioned VPW to V980-P981-W982 in the von Willebrand factor (vWf) A-3 domain. In blood from a vWf-deficient individual, VPW increased platelet adhesion to fibrinogen but not to collagen under flow and rescued the impaired adhesion to vWf deficient in A-3.

CONCLUSION

These data reveal a VPW sequence that contributes to alpha(IIb)beta3 activation in in vitro experiments. Whether the V980-P981-W982 sequence in vWf shows similar properties under in vivo conditions remains to be established.

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.

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.

Control of melanoma progression by various matrikines from basement membrane macromolecules

Many biological processes such as cell differentiation, cell migration or gene expression are tightly controlled by cell-cell interactions or by various cytokines. During tumor progression, cancer cells are in contact with extracellular matrix (ECM) macromolecules involving specific receptors such as integrins. The different stages of tumor progression, and mainly the proteolytic cascades implicated in extracellular matrix degradation and cell migration, may be controlled by the extracellular matrix macromolecules or by domains released by directed and limited proteolysis of these molecules. In this review, we summarise the biological effects of various peptides, named matrikines, derived from basement membranes (BM) components, such as laminins (LN), proteoglycans or collagens. These peptides may control tumor progression by regulating the proteolytic cascades leading to cancer cell dissemination and metastasis.

Matrix metalloproteinases and matrikines in angiogenesis

Neoangiogenesis, the formation of new blood capillaries from pre-existing vessels, plays an important role in a number of physiological and pathological processes, particularly in tumor growth and metastasis. Extracellular proteolysis by matrix metalloproteinases or other neutral proteinases is an absolute requirement for initiating tumor invasion and angiogenesis. Cryptic segments or pre-existing domains within larger proteins, most of them belonging to the extracellular matrix, can be exposed by conformational changes and/or generated by partial enzymatic hydrolysis. They can positively or negatively regulate important functions of endothelial cells including adhesion, migration, proliferation, cell survival and cell-cell interactions. Such regulations by cryptic segments and proteolytic fragments led to the concept of matricryptins and matrikines, respectively. Matrix metalloproteinases and matrikines in conjunction with other pro- or anti-angiogenic factors might act in concert at any step of the angiogenesis process. A number of matrikines have been identified as potent anti-angiogenic factors, which could provide a new alternative to anti-proteolytic strategies for the development of anti-angiogenic therapeutic molecules aimed at inhibiting tumor growth and metastasis. Some of them are currently being investigated in clinical trials.

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

Tumor progression may be controlled by various fragments derived from noncollagenous 1 (NC1) C-terminal domains of type IV collagen. We demonstrated previously that a peptide sequence from the NC1 domain of the alpha3(IV) collagen chain inhibits the in vitro expression of matrix metalloproteinases in human melanoma cells through RGD-independent binding to alpha(v)beta(3) integrin. In the present paper, we demonstrate that in a mouse melanoma model, the NC1 alpha3(IV)-(185-203) peptide inhibits in vivo tumor growth in a conformation-dependent manner. The decrease of tumor growth is the result of an inhibition of cell proliferation and a decrease of cell invasive properties by down-regulation of proteolytic cascades, mainly matrix metalloproteinases and the plasminogen activation system. A shorter peptide comprising the seven N-terminal residues 185-191 (CNYYSNS) shares the same inhibitory profile. The three-dimensional structures of the CNYYSNS and NC1 alpha3(IV)-(185-203) peptides show a beta-turn at the YSNS (188-191) sequence level, which is crucial for biological activity. As well, the homologous MNYYSNS heptapeptide keeps the beta-turn and the inhibitory activity. In contrast, the DNYYSNS heptapeptide, which does not form the beta-turn at the YSNS level, is devoid of inhibitory activity. Structural studies indicate a strong structure-function relationship of the peptides and point to the YSNS turn as necessary for biological activity. These peptides could act as potent and specific antitumor antagonists of alpha(v)beta(3) integrin in melanoma progression.

Transforming growth factor-beta1 inhibits tumor growth in a mouse melanoma model by down-regulating the plasminogen activation system

The degradation of basement membranes by tumor cells involves secretion and activation of proteinases, such as matrix metalloproteinases (MMPs) and the plasminogen activation system (uPA, tPA, PAI-1), and results from an imbalance between their inhibitors and activators, controlled by various growth factors or cytokines. Among them, the TGF-beta family is one of the most intriguing because it has been reported either to decrease or promote cancer progression. In the present paper, we studied the effect of TGF-beta1 in a mouse melanoma model. In vivo, TGF-beta1 inhibited tumor growth after subcutaneous injection of B16F1 cells in syngenic mice. In vitro, TGF-beta1 did not alter B16F1 cell proliferation, but strongly decreased their migration through Matrigel-coated membranes. The protease production was analyzed by zymography, Western blot, or RT-PCR. MMP-2 and TIMP-2 expression were not altered by TGF-beta1. In contrast, TGF-beta1 triggered a large decrease of uPA and tPA, as well as a decrease of uPA and uPAR mRNAs. By Western blot and RT-PCR analyses, TGF-beta1 was shown to induce a strong increase of PAI-1 synthesis. Collectively, these results suggest that TGF-beta1 may inhibit melanoma tumor growth by specifically decreasing plasmin activity of tumor cells and play a protective role during the earliest stages of tumor progression.

Proteolyzed matrix as a template for the regulation of tumor progression

Pericellular proteolysis plays a pivotal function in cell invasion, a hallmark of tumor growth and metastasis. The minidegradome constituted of two matrix metalloproteinases (MMP), i.e. MMP-2 and MT1-MMP, associated with tissue inhibitor of metalloprotease-2 (TIMP-2) and integrin (alpha(v)beta(3)) or CD(44), is mainly involved in such invasive program. It catalyzes matrix degradation but, alternatively, proteolytic exposure of matricryptic sites or matrikines liberation by those enzymes regulates either positively or negatively tumor cell migration. That applies to types I and IV collagens, elastin, laminin 5, as described here, but such phenomenon might be extended to other matrix macromolecules. The development of tumors from epithelium origin is related to aging. Senescent fibroblasts are characterized by increased expression of MMPs, (particularly collagenase-1 (MMP-1) and stromelysin-1 (MMP-3)) and deposited matrix by those aged cells was shown to favor cancer cell growth. Thus, compositional variation of matrix-surrounding tumor cells, with formation of matricryptic sites and matrikines, can be considered as one main epigenetic factor contributing to tumor progression. A matrix-directed pharmacological approach in cancer is now emerging.

Effects of HAb18G/CD147 antagonistic peptides on invasion and metastasis of HCC

AIM: To obtain the antagonistic peptides that have effect to prevent metastasis of Hepatocellular Carcinoma(HCC).

METHODS: Nine pieces of high affinity peptides (AP-1-AP-9) were obtained by pure HAb18G/CD147 antigen to panning phage displayed random peptide library. MTT assay was used to test toxicity of AP-1-AP-9 on human hepatocellular carcinoma cell (HHCC); Gelatin zymogram was used to analyze the effects of AP-1-AP-9 on activation and production of matrix metalloproteinase (MMPs); Matrigel-boyden chamber method was used to evaluate inhibitory abilities of AP-1-AP-9 on tumor cell invasion and metastasis; Inhibitory effect of AP-1-AP-9 on HHCC adhesion to extracellular matrix protein and fb cells were investigated. The influences of AP-1-AP-9 on HHCC chemotaxis migration were also tested.

RESULTS: AP-1-AP-9 has no toxicity on HHCC; AP-1, AP-6 and AP-9 could inhibit production and activation of MMP-2; the amounts of infiltrative cells in AP-1, 3, 6, 7, 8, 9 experimental groups are significantly less than that in control group (P < 0.05), and inhibition rate was 78.22%, 90.1%, 62.83%, 56.44%, 68.32%, 81.19%, respectively; AP-1-AP-9 had no effects on HHCC adhesion to matrigel and fibronectin (FN), whereas AP-3 and AP-9 could inhibit HHCC adhesion to collagen Ⅳand laminin(LN), AP-1, AP-6 and AP-9 could inhibit HHCC adhesion to fb. AP-6 could inhibit chemotaxis migration of HHCC with the inhibitory rate of 54% without statistical significance (P > 0.05).

CONCLUSION: HAb18G/CD147 antagonistic peptides (AP-1-AP-9) have inhibitory effects on many aspects or steps associated with metastasis of HCC, which provides avenue to explore medication for preventing metastasis of HCC.

New functional roles for non-collagenous domains of basement membrane collagens

Collagens IV, XV and XVIII are major components of various basement membranes. In addition to the collagen-specific triple helix, these collagens are characterized by the presence of several non-collagenous domains. It is clear now that these ubiquitous collagen molecules are involved in more subtle and sophisticated functions than just the molecular architecture of basement membranes, particularly in the context of extracellular matrix degradation. Degradation of the basement membrane collagens occurs during numerous physiological and pathological processes such as embryonic development or tumorigenesis and generates collagen fragments. These fragments are involved in the regulation of functions differing from those of their original intact molecules. The non-collagenous C-terminal fragment NC1 of collagen IV, XV and XVIII have been recently highlighted in the literature because of their potential in reducing angiogenesis and tumorigenesis, but it is clear that their biological functions are not limited to these processes. Proteolytic release of soluble NC1 fragments stimulates migration, proliferation, apoptosis or survival of different cell types and suppresses various morphogenetic events.

Negative regulation of bone morphogenetic protein/Smad signaling by Cas-interacting zinc finger protein in osteoblasts

Bone morphogenetic protein (BMP) signaling regulates body axis determination, apoptosis, and differentiation of various types of cells including neuron, gut, and bone cells. However, the molecules involved in such BMP regulation of biological events have not been fully understood. Here, we examined the involvement of Cas-interacting zinc finger protein (CIZ) in the modulation of BMP2-induced osteoblastic cell differentiation. CIZ overexpression in osteoblastic MC3T3E1 cells suppressed BMP2-enhanced expression of alkaline phosphatase, osteocalcin, and type I collagen genes. Upstream analyses revealed that CIZ overexpression also suppressed BMP2-induced enhancement of the mRNA expression of Cbfa1, which is a critical transcription factor for osteoblastic differentiation. BMP-induced Smad1 and Smad5 activation of GCCG-mediated transcription was blocked in the presence of CIZ overexpression. CIZ overexpression alone in the absence of BMP2 moderately enhanced basal levels of Cbfa1 mRNA expression. CIZ overexpression also enhanced 1.8-kb Cbfa1 promoter activity in the absence of BMP2, whereas it suppressed the promoter activity in the presence of BMP2. Finally, CIZ overexpression suppressed the formation of mineralized nodules in osteoblastic cell cultures. These data indicate that CIZ is a novel type inhibitor of BMP/Smad signaling.

Matrix-directed regulation of pericellular proteolysis and tumor progression

The microenvironment of cancer cells, composed of extracellular matrix (ECM) macromolecules, plays a pivotal function in tumor progression. ECM preexisting modules or cryptic sites revealed by partial enzymatic hydrolysis positively or negatively regulate matrix metalloproteinase (MMP) expression and activation, further influencing matrix invasion by cancer cells. Pericellular activation of gelatinase A (MMP-2) proceeds via the formation of a complex involving its inhibitor, TIMP-2, its activator(s), MT-MMPs and alphavbeta3 integrin forming a docking system. This proteinase has been invariably linked to cancer cell invasive potential and is often predictive of a poor survival. MMP-2 degrades most ECM macromolecules and appears to act as a main 'decryptase'. ECM modulation of MMP-2 activation pathway thus influences angiogenesis and tumor growth. For instance the noncollagenous domain of alpha3 chain of type IV collagen, through alphavbeta3 integrin binding, inhibits both MT1-MMP and alphavbeta3 integrin expression from melanoma cells and empedes cell migration and proliferation. At the opposite, a particular module in elastin (VGVAPG) with type VIII beta turn conformation stimulates MT1-MMP and proMMP-2 activation through binding to S-gal elastin receptor, and increases the matrix invasive capacity of several cancer cell lines and endothelial cells. Endocytosis emerges as a main mechanism controlling MMP-2, and also other MMPs; it proceeds via the formation of a MMP-thrombospondin(s) complex further recognized by the LRP scavenger receptor. ECM undergoes conspicuous variations with aging linked to alterations of tissue organization and post-translational modifications of matrix constituents that modify cell-matrix interactions and MMP-2 activation pathway.

Extracellular matrix-derived peptide binds to alpha(v)beta(3) integrin and inhibits angiogenesis

Angiogenesis is associated with several pathological disorders as well as with normal physiological maintenance. Components of vascular basement membrane are speculated to regulate angiogenesis in both positive and negative manner. Recently, we reported that tumstatin (the NC1 domain of alpha 3 chain of type IV collagen) and its deletion mutant tum-5 possess anti-angiogenic activity. In the present study, we confirm that the anti-angiogenic activity of tumstatin and tum-5 is independent of disulfide bond requirement. This property of tum-5 allowed us to use overlapping synthetic peptide strategy to identify peptide sequence(s) which possess anti-angiogenic activity. Among these peptides, only the T3 peptide (69-88 amino acids) and T7 peptide (74-98 amino acids) inhibited proliferation and induced apoptosis specifically in endothelial cells. The peptides, similar to tumstatin and the tum-5 domain, bind and function via alpha(v)beta(3) in an RGD-independent manner. Restoration of a disulfide bond between two cysteines within the peptide did not alter the anti-angiogenic activity. Additionally, these studies show that tumstatin peptides can inhibit proliferation of endothelial cells in the presence of vitronectin, fibronectin, and collagen I. Anti-angiogenic effect of the peptides was further confirmed in vivo using a Matrigel plug assay in C57BL/6 mice. Collectively, these experiments suggest that the anti-angiogenic activity of tumstatin is localized to a 25-amino acid region of tumstatin and it is independent of disulfide bond linkage. Structural features and potency of the tumstatin peptide make it highly feasible as a potential anti-cancer drug.