Anti-angiogenic activity of the recombinant kringle domain of urokinase and its specific entry into endothelial cells

Tale of two systems: the intertwining duality of fibrinolysis and lipoprotein metabolism

Fibrinolysis is an enzymatic process that breaks down fibrin clots, while dyslipidemia refers to abnormal levels of lipids and lipoproteins in the blood. Both fibrinolysis and lipoprotein metabolism are critical mechanisms that regulate a myriad of functions in the body, and the imbalance of these mechanisms is linked to the development of pathologic conditions, such as thrombotic complications in atherosclerotic cardiovascular diseases. Accumulated evidence indicates the close relationship between the 2 seemingly distinct and complicated systems-fibrinolysis and lipoprotein metabolism. Observational studies in humans found that dyslipidemia, characterized by increased blood apoB-lipoprotein and decreased high-density lipoprotein, is associated with lower fibrinolytic potential. Genetic variants of some fibrinolytic regulators are associated with blood lipid levels, supporting a causal relationship between these regulators and lipoprotein metabolism. Mechanistic studies have elucidated many pathways that link the fibrinolytic system and lipoprotein metabolism. Moreover, profibrinolytic therapies improve lipid panels toward an overall cardiometabolic healthier phenotype, while some lipid-lowering treatments increase fibrinolytic potential. The complex relationship between lipoprotein and fibrinolysis warrants further research to improve our understanding of the bidirectional regulation between the mediators of fibrinolysis and lipoprotein metabolism.

Therapeutic Strategies Targeting Urokinase and Its Receptor in Cancer

Several studies have ascertained that uPA and uPAR do participate in tumor progression and metastasis and are involved in cell adhesion, migration, invasion and survival, as well as angiogenesis. Increased levels of uPA and uPAR in tumor tissues, stroma and biological fluids correlate with adverse clinic-pathologic features and poor patient outcomes. After binding to uPAR, uPA activates plasminogen to plasmin, a broad-spectrum matrix- and fibrin-degrading enzyme able to facilitate tumor cell invasion and dissemination to distant sites. Moreover, uPAR activated by uPA regulates most cancer cell activities by interacting with a broad range of cell membrane receptors. These findings make uPA and uPAR not only promising diagnostic and prognostic markers but also attractive targets for developing anticancer therapies. In this review, we debate the uPA/uPAR structure-function relationship as well as give an update on the molecules that interfere with or inhibit uPA/uPAR functions. Additionally, the possible clinical development of these compounds is discussed.

Natural dietary compound naringin inhibits glioblastoma cancer neoangiogenesis

Background

Flavonoids, which existed nearly in all fruits and vegetables, are considered as a class of plant-secondary metabolites with a polyphenolic structure and have properties with health-improving potential. Yet, not so many experimental focus on the benefits of flavonoid in vivo after external application. Here we assessed the impacts of naringin in vitro and in vivo in the human glioma U-87 cells implanted into athymic mice.

Methods

Tumor size and animal survival time were followed in naringin-treated mice bearing subcutaneous gliomas. To define the effects of naringin on angiogenesis, in vitro, tube formation and migration were assayed using endothelial HUVEC cell line.

Results

Low concentration of naringin remarkably inhibited tubulogenesis and reduced cell invasion. Moreover, naringin has been shown to have a toxicity effect on U-87 cells in a dose-dependent way. Furthermore, naringin administration (120 mg/kg/day) applies serious anti-cancer belongings on glioblastoma, as demonstrated by a slow cancer progression.

Conclusions

Our study has provided the first evidence on the antitumor effect of naringin, which is somehow due to the inhibition of invasion and angiogenesis.

Urokinase-derived peptide UP-7 suppresses tumor angiogenesis and metastasis through inhibition of FAK activation

The recombinant kringle domain of urokinase (UK1) has been shown to inhibit angiogenesis and brain tumor growth in vivo. To avoid limitations in application due to mass production of recombinant protein, we attempted to develop a novel peptide inhibitor from UK1 sequence consisting of 83 amino acids that contains α-helices, loops and β-sheets. We dissected UK1 sequence to seven peptides based on structure and amino acid characteristics, and examined the anti-angiogenic activities for the constructed peptides. Among the tested peptides, UP-7 most potently inhibited the proliferation and migration of endothelial cells (ECs) in vitro, and also potently inhibited in vivo angiogenesis in the mouse matrigel plug assay. Such anti-angiogenic activities were not exerted by the scrambled peptide. At molecular level, UP-7 inhibited growth factor-induced phosphorylation of FAK and ERK1/2. It also suppressed formation of stress fibers and focal adhesions and also inhibited the attachment and spreading of ECs onto immobilized fibronectin. In a lung cancer animal model xenografted with non-UP-7-sensitive NCI-H460 cells, systemic treatment of UP-7 effectively suppressed tumor growth through inhibition of angiogenesis. Interestingly, breast cancer cells such as LM-MDA-MB-231 cells were moderately sensitive to UP-7 in proliferation differently from other cancer cells. UP-7 also inhibited migration, invasion and FAK phosphorylation of LM-MDA-MB-231 cells. Accordingly, UP-7 potently inhibited lung metastatic growth of LM-MDA-MB-231 cells in an experimental metastasis model. Taken together, these results suggest that novel peptide UP-7 can be effectively used for treatment of breast cancer metastatic growth through inhibition of angiogenesis and invasion.

Inhibition of Pathologic Corneal Neovascularization by Topical Application of a Novel Peptide In Vivo

PURPOSE

To investigate the antiangiogenic effect of topical application of H-KI20, a novel 20-amino acid peptide from the hepatocyte growth factor, on 2 animal models of corneal neovascularization (NV), and its possible toxic effects on the cornea and conjunctiva.

METHODS

The antiangiogenic effect of topical H-KI20 in vivo was studied on corneal NV induced by a mouse corneal micropocket assay and rat intrastromal suture model. In each model, H-KI20, scrambled control peptide H-KI20S, bevacizumab, and phosphate buffer solution (PBS) were applied topically 4 times a day. Corneal NV was examined, photographed, and analyzed. Histological analysis of the corneas was performed. Tear film breakup time and gross and histological examinations were used to study the possible toxicity of topical H-KI20.

RESULTS

Topical application of H-KI20 significantly inhibited corneal NV induced by vascular endothelial growth factor (VEGF), and intrastromal suture (P < 0.01 vs. the PBS group), and the area of corneal NV was suppressed by 80.3% and 83.6%, respectively (PBS group as 100%). No significant difference was found between 1.0 mg/mL H-KI20 and 10 mg/mL bevacizumab (P > 0.05). Both hematoxylin and eosin and CD34 staining revealed fewer new blood vessels in the H-KI20 and bevacizumab groups. Tear film breakup time and histological examinations showed that H-KI20 had no obvious toxic effects on the cornea and conjunctiva in vivo.

CONCLUSIONS

The novel peptide H-KI20 is an effective and safe inhibitor of corneal NV. It may provide a promising alternative for ocular topical antiangiogenic therapy.

Cecal succinate elevated by some dietary polyphenols may inhibit colon cancer cell proliferation and angiogenesis

This study demonstrated that 0.5% dietary rutin, ellagic acid, or curcumin markedly increased cecal succinate levels in rats fed a high-fat diet, whereas catechin, caffeic acid, and quercetin did not. Other organic acids were modestly or hardly affected by polyphenols. To clarify the effects of succinate levels increased by polyphenols, this study examined the effects of succinate on the growth and proliferation of colon cancer cells and angiogenesis. The growth and proliferation of HT29 human colon cancer cells and angiogenesis in an ex vivo model were significantly inhibited by succinate at a dose close to that in the cecum of rats fed polyphenols. Furthermore, succinate inhibited the migration of human umbilical vein endothelial cells. These findings suggest that the consumption of some polyphenols affects the health and diseases of the large intestine by elevating succinate.

Chemotherapy of Prostate Cancer by Targeted Nanoparticles Trackable by Magnetic Resonance Imaging

Prostate cancer (CaP) is the commonest diagnosed malignancy and the second main cause of cancer mortality in males in the United States. Thus, there is an urgent need to develop novel drug delivery systems to improve the chemotherapy option for CaP patients. The goal of this paper is to describe novel moleculary guided nanoscale drug delivery system with dual functionality for treatment and MR imaging of CaP. We describe the synthesis of iron oxide nanoparticles (IONPs) which are then coated with carboxyl-ended amphiphilic polymer. We present the protocol for tethering of the CaP targeting protein, human amino terminal fragment (hATF) to the terminal carboxyls of the IONPs. We describe the drug loading and release and the methods for measuring of the internalization of the hATF-guided IONPs into CaP cells. We also describe the methods for usages of IONPs are MR imaging contrast agent and successful targeted drug carriers.

Antiangiogenic effect of chamigrane endoperoxides from a Thai mangrove-derived fungus

As part of our ongoing efforts to investigate natural products with potential for use as cancer treatments, we have recently disclosed the cytotoxicity of unique nor-chamigrane (1) and chamigrane (2, 3) endoperoxides from a Thai mangrove-derived fungus. Reinvestigation of this fungus in a large-scale fermentation led to the isolation of an additional new chamigrane endoperoxide (4) and one known analogue (5). Among these isolated metabolites, compound 3 (merulin C) exhibited potent antiangiogenic activity mainly by suppression of endothelial cell proliferation and migration in a dose-dependent manner, and its effect is mediated by reduction in the phosphorylation of Erk1/2. Merulin C also displayed promising activity in a rat aortic ring sprouting (ex vivo) and a mouse Matrigel (in vivo) assay.

High efficacy and minimal peptide required for the anti-angiogenic and anti-hepatocarcinoma activities of plasminogen K5

Kringle 5(K5) is the fifth kringle domain of human plasminogen and its anti-angiogenic activity is more potent than angiostatin that includes the first four kringle fragment of plasminogen. Our recent study demonstrated that K5 suppressed hepatocarcinoma growth by anti-angiogenesis. To find high efficacy and minimal peptide sequence required for the anti-angiogenic and anti-tumour activities of K5, two deletion mutants of K5 were generated. The amino acid residues outside kringle domain of intact K5 (Pro452-Ala542) were deleted to form K5mut1(Cys462-Cys541). The residue Cys462 was deleted again to form K5mut2(Met463-Cys541). K5mut1 specifically inhibited proliferation, migration and induced apoptosis of endothelial cells, with an apparent two-fold enhanced activity than K5. Intraperitoneal injection of K5mut1 resulted in more potent tumour growth inhibition and microvessel density reduction than K5 both in HepA-grafted and Bel7402-xenografted hepatocarcinoma mouse models. These results suggested that K5mut1 has more potent anti-angiogenic activity than intact K5. K5mut2, which lacks only the amino terminal cysteine of K5mut1, completely lost the activity, suggesting that the kringle domain is essential for the activity of K5. The activity was enhanced to K5mut1 level when five acidic amino acids of K5 in NH₂ terminal outside kringle domain were replaced by five serine residues (K5mut3). The shielding effect of acidic amino acids may explain why K5mut1 has higher activity. K5, K5mut1 and K5mut3 held characteristic β-sheet spectrum while K5mut2 adopted random coil structure. These results suggest that K5mut1 with high efficacy is the minimal active peptide sequence of K5 and may have therapeutic potential in liver cancer.

Anti-angiogenic effect of siphonaxanthin from green alga, Codium fragile

Since anti-angiogenic therapy has becoming a promising approach in the prevention of cancer and related diseases, the present study was aimed to examine the anti-angiogenic effect of siphonaxanthin from green alga (Codium fragile) in cell culture model systems and ex vivo approaches using human umbilical vein endothelial cells (HUVECs) and rat aortic ring, respectively. Siphonaxanthin significantly suppressed HUVEC proliferation (p<0.05) at the concentration of 2.5 μM (50% as compared with control) and above, while the effect on chemotaxis was not significant. Siphonaxanthin exhibited strong inhibitory effect on HUVEC tube formation. It suppressed the formation of tube length by 44% at the concentration of 10 μM, while no tube formation was observed at 25 μM, suggesting that it could be due to the suppression of angiogenic mediators. The ex vivo angiogenesis assay exhibited reduced microvessel outgrowth in a dose dependent manner and the reduction was significant at more than 2.5 μM. Our results imply a new insight on the novel function of siphonaxanthin in preventing angiogenesis related diseases.

Synthesis and biological evaluation of vitamin K derivatives as angiogenesis inhibitor

Ten vitamin K(3) derivatives were synthesized and screened for anti-angiogenic activity. Results indicated that amine derivatives (1a-d) exerted a stronger inhibition effect on angiogenesis compared to alkyl derivatives (2a-d). In addition to being the most potent inhibitor, 1b also suppressed human umbilical vein endothelial cell tube formation and proliferation. These results suggest that vitamin K(3) amine derivatives with shorter alkyl chains, such as 1b, could be useful for developing anti-angiogenic agents.

In vitro and in vivo antiangiogenic activity of a novel deca-peptide derived from human tissue-type plasminogen activator kringle 2

A synthetic deca-peptide corresponding to the amino acid sequence Arg(54)-Trp(63) of human tissue-type plasminogen activator (t-PA) kringle 2 domain, named TKII-10, is produced and tested for its ability to inhibit endothelial cell proliferation, migration, tube formation in vitro, and angiogenesis in vivo. At the same time, another peptide TKII-10S composed of the same 10 amino acids as TKII-10, but in a different sequence, is also produced and tested. The results show that TKII-10 potently inhibits VEGF-stimulated endothelial cell migration and tube formation in a dose-dependent, as well as sequence-dependent, manner in vitro while it is inactive in inhibiting endothelial cell proliferation. Furthermore, TKII-10 potently inhibits angiogenesis in chick chorioallantoic membrane and mouse cornea. The middle four amino acids DGDA in their sequence play an important role in TKII-10 angiogenesis inhibition(.) These results suggest that TKII-10 is a novel angiogenesis inhibitor that may serve as a prototype for antiangiogenic drug development.

The Chick Embryo Chorioallantoic Membrane as an In Vivo Assay to Study Antiangiogenesis

Antiangiogenesis, e.g., inhibition of blood vessel growth, is being investigated as a way to prevent the growth of tumors and other angiogenesis-dependent diseases. Pharmacological inhibition interferes with the angiogenic cascade or the immature neovasculature with synthetic or semi-synthetic substances, endogenous inhibitors or biological antagonists.The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane, which serves as a gas exchange surface and its function is supported by a dense capillary network. Because its extensive vascularization and easy accessibility, CAM has been used to study morphofunctional aspects of the angiogenesis process in vivo and to study the efficacy and mechanism of action of pro- and anti-angiogenic molecules. The fields of application of CAM in the study of antiangiogenesis, including our personal experience, are illustrated in this review article.

Inhibition of migration and invasion of carcinoma cells by urokinase-derived antagonists of alphavbeta5 integrin activation

We previously showed that, while binding to urokinase receptor (uPAR) through its growth factor domain (GFD, residues 1-49), urokinase (uPA) can engage alphavbeta5 integrin through an internal domain (CP, residues 132-158). This novel uPA/alphavbeta5 interaction promotes cytoskeletal rearrangements and directional cell migration (Franco et al., J Cell Sci 2006;119:3424-34). We now show that treatment of cells with phosphomimic uPA (uPA138E/303E, serine 138 and 303 substituted with glutamic acid) strongly inhibits matrix-induced cell migration. Unlike uPA, binding of uPA138E/303E to cell surface did not induce F-actin enriched protruding structures and caused a 5-fold reduction in cell translocation speed, as determined by video tracking of living cells. Inhibition of migration was found to be independent of uPAR, since uPA variants lacking the GFD domain, but carrying the relevant Ser to Glu substitutions were as effective inhibitor as uPA138E/303E. Through several independent approaches, we established that the phosphomimics specifically bind to alphavbeta5 integrin through the CP region carrying the S138E mutation. This interaction blocks integrin activation, as determined by a decreased affinity of alphavbeta5 to vitronectin and a reduced association of the beta5 cytoplasmic tail with talin. Finally, stable expression of uPA138E/303E in human squamous carcinoma cells prevented tumor cell invasion in vivo. Thus, when expressed in cancer cells, the inhibitory phosphomimic effect was dominant over the effect of endogenously produced uPA. These results shed light on the regulation of cell migration by uPA phosphorylation and provide a realistic opportunity for a novel antiinvasive/metastatic therapeutic intervention.

Antimigratory effect of TK1-2 is mediated in part by interfering with integrin alpha2beta1

The recombinant two kringle domain of human tissue-type plasminogen activator (TK1-2) has been shown to inhibit endothelial cell proliferation, angiogenesis, and tumor cell growth despite of sharing a low amino acid sequence homology with angiostatin. Here, we explored a possible inhibitory mechanism of action of TK1-2 by focusing on antimigratory effect. TK1-2 effectively inhibited endothelial cell migration induced by basic fibroblast growth factor or vascular endothelial growth factor in a dose-dependent manner and tube formation on Matrigel. It blocked basic fibroblast growth factor-induced or vascular endothelial growth factor-induced phosphorylation of extracellular signal-regulated kinase 1/2 and formation of actin stress fibers and focal adhesions. Interestingly, TK1-2 alone induced the weak phosphorylation of focal adhesion kinase, whereas it inhibited focal adhesion kinase phosphorylation induced by growth factors. When immobilized, TK1-2 promoted adhesion and spreading of endothelial cells compared with bovine serum albumin. However, treatment with anti-alpha(2)beta(1) blocking antibody markedly diminished endothelial cell adhesion to immobilized TK1-2 compared with anti-alpha(v)beta(3) or anti-alpha(5)beta(1) antibody. Pretreatment of soluble TK1-2 also altered the binding level of anti-alpha(2)beta(1) antibody to endothelial cells in fluorescence-activated cell sorting analysis. Indeed, a blocking antibody against integrin alpha(2)beta(1) or knocking down of integrin alpha(2) expression prevented the inhibitory effect of TK1-2 in cell migration. Therefore, these results suggest that TK1-2 inhibits endothelial cell migration through inhibition of signaling and cytoskeleton rearrangement in part by interfering with integrin alpha(2)beta(1).

Nuclear translocation of urokinase-type plasminogen activator

Urokinase-type plasminogen activator (uPA) participates in diverse (patho)physiological processes through intracellular signaling events that affect cell adhesion, migration, and proliferation, although the mechanisms by which these occur are only partially understood. Here we report that upon cell binding and internalization, single-chain uPA (scuPA) translocates to the nucleus within minutes. Nuclear translocation does not involve proteolytic activation or degradation of scuPA. Neither the urokinase receptor (uPAR) nor the low-density lipoprotein-related receptor (LRP) is required for nuclear targeting. Rather, translocation involves the binding of scuPA to the nucleocytoplasmic shuttle protein nucleolin through a region containing the kringle domain. RNA interference and mutational analysis demonstrate that nucleolin is required for the nuclear transport of scuPA. Furthermore, nucleolin is required for the induction smooth muscle alpha-actin (alpha-SMA) by scuPA. These data reveal a novel pathway by which uPA is rapidly translocated to the nucleus where it might participate in regulating gene expression.

Vaccinium myrtillus (Bilberry) Extracts Reduce Angiogenesis In Vitro and In Vivo

Vaccinium myrtillus (Bilberry) extracts (VME) were tested for effects on angiogenesis in vitro and in vivo. VME (0.3–30 µg ml⁻¹) and GM6001 (0.1–100 µM; a matrix metalloproteinase inhibitor) concentration-dependently inhibited both tube formation and migration of human umbilical vein endothelial cells (HUVECs) induced by vascular endothelial growth factor-A (VEGF-A). In addition, VME inhibited VEGF-A-induced proliferation of HUVECs. VME inhibited VEGF-A-induced phosphorylations of extracellular signal-regulated kinase 1/2 (ERK 1/2) and serine/threonine protein kinase family protein kinase B (Akt), but not that of phospholipase Cγ (PLCγ). In an in vivo assay, intravitreal administration of VME inhibited the formation of neovascular tufts during oxygen-induced retinopathy in mice. Thus, VME inhibited angiogenesis both in vitro and in vivo, presumably by inhibiting the phosphorylations of ERK 1/2 and Akt. These findings indicate that VME may be effective against retinal diseases involving angiogenesis, providing it can reach the retina after its administration. Further investigations will be needed to clarify the major angiogenesis-modulating constituent(s) of VME.

Outgrowing endothelial progenitor-derived cells display high sensitivity to angiogenesis modulators and delayed senescence

Outgrowing endothelial progenitor-derived cells (EPDCs) originate from a novel hierarchy of endothelial progenitor cells. In this study, EPDCs isolated from human cord blood were examined for phenotype and functional features upon aging. Young or aged EPDCs were similar to human umbilical vein endothelial cells (HUVECs), in exhibiting typical endothelial phenotypes. However, EPDCs were more sensitive to angiogenesis inducers or inhibitors in proliferation and migration. In addition, EPDCs underwent senescence markedly slowly with sustained endothelial NO synthase expression and activation, and their ability to undergo capillary morphogenesis was retained throughout longterm culture. Thus, these results suggest that a homogenous population of EPDCs derived from clonogenic expansion may provide an effective vasculogenesis tool.

T-cadherin suppresses angiogenesis in vivo by inhibiting migration of endothelial cells

Our previous studies have revealed the abundant expression of T-cadherin--a glycosylphosphatidylinositol (GPI)-anchored member of cadherin superfamily--in endothelial and mural cells in the heart and vasculature. The upregulation of T-cadherin in vascular proliferative disorders such as atherosclerosis and restenosis suggests the involvement of T-cadherin in vascular growth and remodeling. However, the functional significance of this molecule in the vasculature remains unknown. The effect of T-cadherin on angiogenesis in vivo was evaluated using Matrigel implant model. We demonstrate that T-cadherin overexpression in L929 cells injected in Matrigel inhibits neovascularization of the plug. In vitro T-cadherin inhibits the directional migration of endothelial cells, capillary growth, and tube formation but has no effect on endothelial cell proliferation, adhesion, or apoptosis in vitro. These data suggest that T-cadherin expressed in the stroma could act as a negative guidance cue for the ingrowing blood vessels and thus could have an important potential therapeutic application.

Potential therapeutic implications of intracrine angiogenesis

Angiogenesis, in most cases, is a requirement for tumor growth beyond a diameter of a few millimeters and is, therefore, a major target for cancer therapy. The intracellular actions of certain extracellular signaling proteins (intracrines) have been reported, and it is clear that intracrines such as vascular endothelial growth factor, basic fibroblast growth factor, angiogenin, angiotensin, and endothelin, among others, are involved in angiogenesis. We have proposed that intracrine networks play an important role in angiogenesis, and have suggested that very similar intracrine networks exist in some tumor cells. These notions have implications for the development of anti-angiogenesis therapies because they suggest that the inhibition of intracellular intracrine trafficking pathways may be an effective therapeutic target. Here the participation and regulation of intracrines in angiogenesis is explored, as are the actions of various anti-angiogenic factors.

An intracrine view of angiogenesis

Angiogenesis, the generation of new blood vessels from pre-existing vessels, is an integral component of wound healing, responses to inflammation and other physiologic processes. It is also an essential part of tumor growth; in the absence of new vessel formation, tumors cannot expand beyond a small volume. Although much is known about angiogenesis and its regulation, there is no overall theory that describes or explains this process. It is here suggested that the intracrine hypothesis, which ascribes to certain extracellular signaling peptides (whether hormones, growth factors, DNA-binding proteins or enzymes) a role in both intracellular biology and extracellular signaling, can contribute to a more general understanding of angiogenesis. Intracrine factors participate in angiogenesis in the following ways: (1) they can act within the cells that synthesized them (type I intracrine action), (2) they can be secreted and then taken up by their cell of synthesis to act intracellularly (type II intracrine action ), or (3) they can be secreted and internalized by a distant target cell (type III intracrine action). The parallels between the intracrine growth factor mechanisms cancer cells employ in stimulating their own growth and the mechanisms operative in endothelial cell proliferation during angiogenesis ("intracrine reciprocity") are discussed. Collectively, these explorations lead to testable hypotheses regarding the regulation of normal and pathological angiogenesis, and point to similarities between tumor-induced angiogenesis and tissue differentiation.

Catechin conjugated with fatty acid inhibits DNA polymerase and angiogenesis

Catechins in green tea have anticancer and antiangiogenesis activities, with epigallocatechin-3-gallate (EGCG) being the most potent antiangiogenic tea catechin. This study examined whether chemical modification of catechin enhanced anticancer and antiangiogenic effects. Catechin, conjugated with fatty acid (acyl-catechin), strongly inhibited DNA polymerase, HL-60 cancer cell growth, and angiogenesis. Catechin conjugated with stearic acid [(2R,3S)-3',4',5,7-tetrahydroxyflavan-3-yl octadecanoate; catechin-C18] was the strongest inhibitor in DNA polymerase alpha and beta and angiogenesis assays. Catechin-C18 also suppressed human endothelial cell (HUVEC) tube formation on the reconstituted basement membrane, suggesting that it affected not only DNA polymerases but also signal transduction pathways in HUVECs. These data indicate that acyl-catechins target both DNA polymerases and angiogenesis as anticancer agents. These results suggest that acylation of catechin is an effective chemical modification to improve the anticancer activity of catechin.

Antiangiogenic activity of deoxoartemisinin derivatives on chorioallantoic membrane

Non acetal-type derivatives at C-12 of artemisinin and their novel dimers including a fullerene conjugate were synthesized and some of them showed potent in vivo antiangiogenic activity on chorioallantoic membrane higher than or comparable to those of fumagillin and thalidomide.

Amino-terminal fragment of urokinase inhibits tumor cell invasion in vitro and in vivo: respective contribution of the urokinase plasminogen activator receptor-dependent or -independent pathway

The urokinase plasminogen activator (uPA) is implicated in both cancer cell invasion and angiogenesis. It can interact with a specific receptor (uPAR) via the epidermal growth factor (EGF)-like domain in the urokinase amino-terminal fragment (ATF) in a species-specific manner. Our previous studies showed that adenovirusmediated delivery of murine ATF (AdmATF) suppressed human tumor growth in mouse models, by inhibiting murine angiogenesis. However, we cannot exclude its putative inhibitory action on human cancer cell invasion through a uPAR-independent pathway. To further investigate the mechanisms of ATF, we constructed another adenovirus, AdhmATF, expressing humanized murine ATF (hmATF). hmATF binds to human uPAR but not to murine uPAR. We compared the antagonist effect of both AdmATF and AdhmATF on human and murine cancer cells. In vitro, the supernatant from AdhmATF-infected cells repressed 79% of membrane-associated uPA activity on human MDA-MB-231 cells, whereas that from AdmATF-infected cells repressed 35% of membrane-associated uPA activity. On murine LLC cells, the supernatant from AdhmATF-infected cells inhibited 29% of cell surface uPA activity, whereas that from AdmATF-infected cells inhibited 74% of cell surface uPA activity. Similar results were obtained in a cell invasion assay. In vivo, intratumoral injection of the adenoviruses into LLC tumors on day 24 postinjection induced lower but significant tumor growth suppression by AdhmATF (tumor volume was 1185 +/- 128 mm3), whereas suppression by AdmATF was greater (407 +/- 147 mm3). In the MDA-MB-231 tumor model, on day 52 postinjection, tumor size was 187 +/- 47 mm3 in the AdhmATF-treated group and 468 +/- 65 mm3 in the AdmATF-treated group. The LLC and MDA-MB- 231 cell lines transfected by mATF or hmATF genes showed growth inhibition In vivo equivalent to the results obtained by adenovirus treatment. These results demonstrate the strong anticancer activity of ATF even when its uPAR-binding affinity has been suppressed, and indicate that ATF exerts an antitumor effect via dual mechanisms: essentially through targeting the uPA-uPAR system via the EGF-like domain and partially through targeting a uPAR-independent interaction via the kringle domain.

The human prothrombin kringle-2 derived peptide, NSA9, is internalized into bovine capillary endothelial cells through endocytosis and energy-dependent pathways

Human prothrombin kringle-2 and its partial peptide, NSA9 (NSAVQLVEN), have been reported to have potent anti-angiogenic activities. Here, the internalization mechanism of NSA9 into bovine capillary endothelial (BCE) cells was examined using lactate dehydrogenase (LDH) release assay, fluorescence microscopy, and flow cytometry. LDH release assay results suggested that the integrity of the BCE cell membrane was unaffected by NSA9. Fluorescence microscopy indicated that internalized NSA9 was localized in the cytoplasm around the nucleus, and showed a punctuated fluorescence pattern, which is indicative of endocytic vesicles. Also, the cellular internalization of NSA9 is significantly inhibited by depletion of the cellular ATP pool, endocytosis inhibitors such as chloroquine and nocodazole, and incubation at low temperature (4 degrees C). In addition, the anti-proliferative activity of NSA9 against BCE cells was diminished in the presence of endocytosis or metabolic inhibitors. In conclusion, these results strongly suggest that NSA9 might exert its anti-proliferative activity through internalization into BCE cells by endocytosis and energy-dependent pathways.

Mechanisms and significance of bifunctional NK4 in cancer treatment

Based on the background that hepatocyte growth factor (HGF) and c-Met/HGF receptor tyrosine kinase play a definite role in tumor invasion and metastasis, NK4, four-kringles containing intramolecular fragment of HGF, was isolated as a competitive antagonist for the HGF-c-Met system. Independent of its HGF-antagonist action, NK4 inhibited angiogenesis induced by vascular endothelial cell growth factor and basic fibroblast growth factor, as well as HGF, indicating that NK4 is a bifunctional molecule that acts as an HGF-antagonist and angiogenesis inhibitor. Interestingly, kringle domains in distinct types of proteins, e.g., plasminogen, prothrombin, plasminogen activators, apolipoprotein(a), and HGF, share angioinhibitory actions. In experimental models of distinct types of cancers, NK4 protein administration or NK4 gene therapy inhibited tumor invasion, metastasis, and angiogenesis-dependent tumor growth. Cancer treatment with NK4 may prove to suppress malignant tumors to be 'static' in both tumor growth and spreading, as based on biological characteristics of malignant tumors.

The kringle domain of urokinase-type plasminogen activator potentiates LPS-induced neutrophil activation through interaction with {alpha}V{beta}3 integrins

Urokinase plasminogen activator (uPA) is a serine protease that catalyzes the conversion of plasminogen to plasmin. In addition, uPA has been shown to have proinflammatory properties, particularly in potentiating lipopolysaccharide (LPS)-induced neutrophil responses. To explore the mechanisms by which uPA exerts these effects, we examined the ability of specific uPA domains to increase cytokine expression in murine and human neutrophils stimulated with LPS. Whereas the addition of intact uPA to neutrophils cultured with LPS increased mRNA and protein levels of interleukin-1beta, macrophage-inflammatory protein-2, and tumor necrosis factor alpha, deletion of the kringle domain (KD) from uPA resulted in loss of these potentiating effects. Addition of purified uPA KD to LPS-stimulated neutrophils increased cytokine expression to a degree comparable with that produced by single-chain uPA. Inclusion of the arginine-glycine-aspartic but not the arginine-glycine-glutamic peptide to neutrophil cultures blocked uPA kringle-induced potentiation of proinflammatory responses, demonstrating that interactions between the KD and integrins were involved. Antibodies to alpha(V) or beta(3) integrins or to the combination of alpha(V)beta(3) prevented uPA kringle-induced enhancement of expression of proinflammatory cytokines and also of adhesion of neutrophils to the uPA KD. These results demonstrate that the KD of uPA, through interaction with alpha(V)beta(3) integrins, potentiates neutrophil activation.

Anti-angiogenic activity of the mutant Dutch A(beta) peptide on human brain microvascular endothelial cells

Cerebral amyloid angiopathy is a common pathological feature of patients with Alzheimer's disease (AD) and it is also the hallmark of individuals with a rare autosomal dominant disorder known as hereditary cerebral hemorrhage with amyloidosis-Dutch type. We have shown previously that wild type A(beta) peptides are anti-angiogenic both in vitro and in vivo and could contribute to the compromised cerebrovascular architecture observed in AD. In the present study, we investigated the potential anti-angiogenic activity of the Dutch A(beta)(1-40) (E22Q) peptide. We show that compared to wild type A(beta), freshly solubilized Dutch A(beta) peptide more potently inhibits the formation of capillary structures induced by plating human brain microvascular endothelial cells onto a reconstituted basement membrane. Aggregated/fibrillar preparations of wild type A(beta) and Dutch A(beta) do not appear to be anti-angiogenic in this assay. The stronger anti-angiogenic activity of the Dutch A(beta) compared to wild type A(beta) appears to be related to the increased formation of low molecular weight A(beta) oligomers in the culture medium surrounding human brain microvascular endothelial cells. Using oligonucleotide microarray analysis of human brain microvascular endothelial cells, followed by a genome-scale computational analysis with the Ingenuity Pathways Knowledge Base, networks of genes affected by an anti-angiogenic dose of Dutch A(beta) were identified. This analysis highlights that several biological networks involved in angiogenesis, tumorigenesis, atherosclerosis, cellular migration and proliferation are disrupted in human brain microvascular endothelial cells exposed to Dutch A(beta). Altogether, these data provide new molecular clues regarding the pathological activity of Dutch A(beta) peptide in the cerebrovasculature.

The kringle domain of tissue-type plasminogen activator inhibits in vivo tumor growth

The two-kringle domain of tissue-type plasminogen activator (t-PA) has previously been shown to contain anti-angiogenesis activity. In this study, we explored the potential in vivo anti-tumor effects of the recombinant kringle domain (TK1-2) of human t-PA. Anti-tumor effects of purified Pichia-driven TK1-2 were examined in nude mice models by subcutaneous implantation of human lung (A-549) and colon (DLD-1, HCT-116) cancer cell lines. Mice bearing the tumors were injected with PBS or purified TK1-2 (30 mg/kg) i.p. every day for 22 days. TK1-2 treatment suppressed the A-549, DLD-1, and HCT-116 tumor growth by 85.3%, 52.4%, and 62.5%, respectively. Immunohistological examination of the tumor tissues showed that TK1-2 treatment decreased the vessel density and also the expression of angiogenesis-related factors including angiogenin, VEGF, alpha-SMA, vWF, and TNF-alpha, and increased the apoptotic fraction of cells. TK1-2 neither inhibited in vitro growth of these cancer cells nor affected t-PA-mediated fibrin clot lysis. These results suggest that TK1-2 inhibits the tumor growth by suppression of angiogenesis without interfering with fibrinolysis.

Characterization and biological activities of recombinant human plasminogen kringle 1-3 produced in Escherichia coli

Angiogenesis, the formation of new capillaries from preexisting blood vessels, is involved in many pathological conditions, for example, tumorigenesis, diabetic retinopathy, and rheumatoid arthritis. Angiostatin, which contains the kringle 1-4 domains of plasminogen, is known to be a potent inhibitor of angiogenesis and a strong suppressor of various solid tumors. In this study, we expressed recombinant protein containing the kringle 1-3 domains of human plasminogen in Escherichia coli and investigated its biological activities. The protein was successfully refolded from inclusion bodies and purified at a 30% overall yield, as a single peak by HPLC. The purified recombinant protein had biochemical properties that were similar to those of the native form, which included molecular size, lysine-binding capacity, and immunoreactivity with a specific antibody. The recombinant protein was also found to strongly inhibit the proliferation of bovine capillary endothelial cells in vitro, and the formation of new capillaries on chick embryos. In addition, it suppressed the growth of primary Lewis lung carcinoma and B16 melanoma in an in vivo mouse model. Our findings suggest that the recombinant kringle 1-3 domains in a prokaryote expression system have anti-angiogenic activities, which may be useful in clinical and basic research in the field of angiogenesis.

Antiangiogenic activity of a domain deletion mutant of tissue plasminogen activator containing kringle 2

OBJECTIVE

The thrombolytic therapy drug, Reteplase, is a domain deletion mutant of tissue plasminogen activator (tPA), comprising the kringle 2 and protease (K2P) domains. Some kringle domains of hemostatic proteins are antiangiogenic and promote apoptosis. The objective of this study was to investigate whether K2P is an angiogenesis inhibitor because of the presence of kringle 2.

METHODS AND RESULTS

K2P inhibited basic fibroblast growth factor-induced human endothelial cell proliferation and migration. Inhibition was not dependent on the protease activity of K2P because similar results were obtained with catalytically inactivated K2P. Purification of the kringle 2 domain derived from elastase cleavage of K2P at the Arg275-Ile276 bond revealed that inhibition was mediated by this domain. In addition, K2P inhibited angiogenesis in vivo and increased endothelial cell apoptosis.

CONCLUSIONS

Wound healing and angiogenesis are severely compromised by K2P. These data provide new mechanistic insights into the bleeding complications observed in some patients while undergoing thrombolytic therapy with this drug. In addition, we identify the kringle 2 domain of tPA as a novel target for antiangiogenic therapy.

Survey of the year 2003 commercial optical biosensor literature

In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.