Parathyroid hormone-related peptide is a naturally occurring,protein kinase A-dependent angiogenesis inhibitor

Angiogenesis is a highly regulated process that results from the sequential actions of naturally occurring stimulators and inhibitors. Here, we show that parathyroid hormone-related peptide, a peptide hormone derived from normal and tumor cells that regulates bone metabolism and vascular tone, is a naturally occurring angiogenesis inhibitor. Parathyroid hormone-related peptide or a ten-amino-acid peptide from its N terminus inhibits endothelial cell migration in vitro and angiogenesis in vivo by activating endothelial cell protein kinase A. Activation of protein kinase A inhibits cell migration and angiogenesis by inhibiting the small GTPase Rac. In contrast, inhibition of protein kinase A reverses the anti-migratory and anti-angiogenic properties of parathyroid hormone-related peptide. These studies show that parathyroid hormone-related peptide is a naturally occurring angiogenesis inhibitor that functions by activation of protein kinase A.     

Identification of a novel domain of fibroblast growth factor 2 controlling its angiogenic properties

Fibroblast growth factor 2 (FGF-2) is a potent factor modulating the activity of many cell types. Its dimerization and binding to high affinity receptors are considered to be necessary steps to induce FGF receptor phosphorylation and signaling activation. A structural analysis was carried out and a region encompassing residues 48-58 of human FGF-2 was identified, as potentially involved in FGF-2 dimerization. A peptide (FREG-48-58) derived from this region strongly and specifically inhibited FGF-2 induced proliferation and migration of primary bovine aorta endothelial cells (BAEC) in vitro, and markedly reduced FGF-2-dependent angiogenesis in two distinct in vivo assays. To further investigate the role of region 48-58, a polyclonal antibody raised against FREG-(48-58) was tested and was found to block FGF-2 action in vitro. Human FGF-2 has three histidine residues, one falling within the region 48-58. Chemical modification of histidine residues blocked FGF-2 activity and FREG-(48-58) inhibitory effect in vitro, indicating that histidine residues, in particular the one within FREG-(48-58) region, play a crucial role in the observed activity. Additional experiments showed that FREG-(48-58) specifically interacted with FGF-2, impaired FGF-2-interaction with itself, with heparin and with FGF receptor 1, and inhibited FGF-2-induced receptor phosphorylation and FGF-2 internalization. These data indicate for the first time that region 48-58 of FGF-2 is a functional domain controlling FGF-2 activity.     

New insights into the molecular interaction of the C-terminal sequence of CXCL4 with fibroblast growth factor-2

Full-length CXCL4 chemokine and a peptide derived from its carboxyl-terminal domain exhibits significant antiangiogenic and anti-tumor activity in vivo and in vitro by interacting with fibroblast growth factor (FGF). In this study we used NMR spectroscopy to characterize at a molecular level the interactions between CXCL4 (47-70) and FGF-2 identifying the peptide residues mainly involved in the contact area with the growth factor. Altogether NMR data point to a major role of the hydrophobic contributions of the C-terminal region of CXCL4 (47-70) peptide in addition to specific contacts established by the N-terminal region through cysteine side chain. The proposed recognition mode constitutes a rationale for the observed effects of CXCL4 (47-70) on FGF-2 biological activity and lays the basis for developing novel inhibitors of angiogenesis.     

Nucleosomes bind fibroblast growth factor-2 for increased angiogenesis in vitro and in vivo

Solid tumors often display sites of necrosis near regions of angiogenesis in vivo. As tumor cell necrosis would result in the release of nucleosomes into the extracellular environment, we explored the potential role of nucleosomes in the promotion of angiogenesis. Data indicate that nucleosomes acted similar to heparin and bound to several heparin-binding, proangiogenic factors [i.e., fibroblast growth factor (FGF)-1, FGF-2, vascular endothelial growth factor, and transforming growth factor-beta1]. Nucleosomes modestly enhanced FGF-2 growth of human umbilical vein endothelial cells when grown in restricted media as well as increased human umbilical vein endothelial cell migration and primitive blood vessel tube formation in vitro. On s.c. injection in mice, nucleosomes aided FGF-2 in promoting angiogenesis. These results suggest that nucleosomes released from dying tumor cells aid in the formation of blood vessels and may provide a novel means by which tumor cells increase angiogenesis.     

Structure and inhibitory effects on angiogenesis and tumor development of a new vascular endothelial growth inhibitor

Blocking angiogenesis is an attractive strategy to inhibit tumor growth, invasion, and metastasis. We describe here the structure and the biological action of a new cyclic peptide derived from vascular endothelial growth factor (VEGF). This 17-amino acid molecule designated cyclopeptidic vascular endothelial growth inhibitor (cyclo-VEGI, CBO-P11) encompasses residues 79-93 of VEGF which are involved in the interaction with VEGF receptor-2. In aqueous solution, cyclo-VEGI presents a propensity to adopt a helix conformation that was largely unexpected because only beta-sheet structures or random coil conformations have been observed for macrocyclic peptides. Cyclo-VEGI inhibits binding of iodinated VEGF165 to endothelial cells, endothelial cells proliferation, migration, and signaling induced by VEGF165. This peptide also exhibits anti-angiogenic activity in vivo on the differentiated chicken chorioallantoic membrane. Furthermore, cyclo-VEGI significantly blocks the growth of established intracranial glioma in nude and syngeneic mice and improves survival without side effects. Taken together, these results suggest that cyclo-VEGI is an attractive candidate for the development of novel angiogenesis inhibitor molecules useful for the treatment of cancer and other angiogenesis-related diseases.     

Induction of stromelysin-1 (MMP-3) by fibroblast growth factor-2 (FGF-2) in FGF-2-/- microvascular endothelial cells requires prolonged activation of extracellular signal-regulated kinases-1 and -2 (ERK-1/2)

Basic fibroblast growth factor (FGF-2) and matrix metalloproteinases (MMPs) play key roles in vascular remodeling. Because FGF-2 controls a number of proteolytic activities in various cell types, we tested its effect on vascular endothelial cell expression of MMP-3 (stromelysin-1), a broad-spectrum proteinase implicated in coronary atherosclerosis. Endothelial cells (EC) from FGF-2-/- mice are highly responsive to exogenous FGF-2 and were therefore used for this study. The results showed that treatment of microvascular EC with human recombinant FGF-2 results in strong induction of MMP-3 mRNA and protein expression. Upregulation of MMP-3 mRNA by FGF-2 requires de novo protein synthesis and activation of the ERK-1/2 pathway. FGF-2 concentrations (5-10 ng/ml) that induce rapid and prolonged (24 h) activation of ERK-1/2 upregulate MMP-3 expression. In contrast, lower concentrations (1-2 ng/ml) that induce robust but transient (<8 h) ERK-1/2 activation are ineffective. Inhibition of ERK-1/2 activation at different times (-0.5 h to +8 h) of EC treatment with effective FGF-2 concentrations blocks MMP-3 upregulation. Thus, FGF-2 induces EC expression of MMP-3 with a threshold dose effect that requires sustained activation of the ERK-1/2 pathway. Because FGF-2 controls other EC functions with a linear dose effect, these features indicate a unique role of MMP-3 in vascular remodeling.     

Role of Thrombospondin-1-Derived Peptide, 4N1K, in FGF-2-Induced Angiogenesis

Angiogenesis involves proliferation of capillary endothelial cells and formation of lumen-containing tube-like structures. A recently established murine brain capillary endothelial cell line, IBE, can either proliferate or form tube-like structures (i.e., differentiate) in response to fibroblast growth factor-2 (FGF-2), dependent on the culture conditions. The 4N1K peptide (KRFYVVMWKK), which is derived from the C-terminal cell-binding domain of thrombospondin-1 (TSP-1), inhibited tube formation, but not proliferation of IBE cells. Polyclonal antibodies against 4N1K blocked TSP-1-induced inhibition of tube formation by IBE cells. 4N1K inhibited tyrosine phosphorylation of focal adhesion kinase and FGF-2-stimulated tyrosine phosphorylation of phospholipase C-gamma in tube-forming, but not proliferating, IBE cells. The peptide also inhibited FGF-2-induced neovascularization in mouse cornea. Our results indicate that TSP-1 may exert its inhibitory effects on angiogenesis via the C-terminal cell-binding domain containing the 4N1K sequence by inhibiting tube formation by endothelial cells.     

Inhibition of FGF-2-mediated chemotaxis of murine brain capillary endothelial cells by cyclic RGDfV peptide through blocking the redistribution of c-Src into focal adhesions

The alpha(v)beta(3) integrin is essential for fibroblast growth factor (FGF)-induced angiogenesis in vivo. However, the role of this integrin in FGF-2-mediated cellular responses by cultured endothelial cells is largely unknown. Cyclic RGDfV (cRGDfV) peptide is widely used to inhibit the binding of alpha(v)beta(3) integrin to vitronectin. To investigate the role of this integrin in FGF-2-mediated cellular responses, we used immortalized murine brain capillary endothelial cells, denoted IBE cells. Because IBE cells proliferate and migrate in response to FGF-2-treatment, when cultured on fibronectin-coated surface, we first examined the inhibitory activity of this peptide on the binding of alpha(v)beta(3) integrin to fibronectin as well as vitronectin. Solid phase binding assay revealed that cRGDfV peptide strongly inhibited the binding of purified alpha(v)beta(3) integrin to vitonectin- and fibronectin-coated plastic surfaces at a concentration of 50 microM. cRGDfV peptide at 50 microM inhibited spreading as well as adhesion of IBE cells on vitronectin-coated plastic surface but not on fibronectin. On fibronectin-coated substrata, cRGDfV at 50 microM attenuated FGF-2-mediated chemotaxis, but not FGF-2-induced proliferation, of IBE cells. We have previously demonstrated that mitogen-activated protein kinase (MAPK) activation within focal adhesions through c-Src activity was involved in FGF-2-induced chemotaxis of IBE cells. Treatment of cells with cRGDfV peptide was associated with reduced c-Src activity without tyrosine dephosphorylation. Immunofluorescent staining showed that cRGDfV inhibited redistribution of c-Src into focal adhesions. MAPK activation by FGF-2 within focal adhesions was also attenuated in the presence of cRGDfV peptide. Our results indicated that cRGDfV peptide inhibited redistribution of c-Src into focal adhesions, leading to impaired MAPK activation within focal adhesions and motility in FGF-2-treated endothelial cells.     

Paneling human thyroid cancer cell lines for candidate proteins for targeted anti-angiogenic therapy

Tumor angiogenesis is believed to result from an imbalance of pro- and anti-angiogenic factors, some of which are candidates for targeted therapy. Such therapy has raised hopes for patients with undifferentiated thyroid carcinomas, who are facing a grave prognosis with a survival of only months. In this study, in vivo growth of xenografted human thyroid carcinomas unexpectedly responded quite differently to neutralizing anti-vascular endothelial growth factor (VEGF) antibody. In particular, lasting inhibition as well as accelerated growth occurred after treatment. Consequently, a panel of anti-angiogenic factors was addressed in a representative sample of thyroid carcinoma lines. VEGF, fibroblast growth factor (FGF-2), and endostatin were demonstrated by Western blotting and EIA, whereas PDGF-A, PDGF-B, and IL-6 were negative. Quantification of VEGF, FGF-2, and endostatin revealed a wide range of concentrations from 500 to 4,200 pg/ml VEGF, 5 to 60 pg/ml FGF-2, and 50 to 300 pg/ml endostatin, not related to a particular histologic thyroid carcinoma background. Angiostatin (kringles 1-3) was detected in all, but one of the cell lines. Finally, aaATIII was confirmed in FTC133 cells. These data highlight the complex regulation of angiogenesis in thyroid carcinoma cell lines and suggest that the array of angiogenic factors differs markedly between individual cell lines. For the first time, angiostatin, endostatin, and possibly also aaATIII are identified as novel candidate regulators of angiogenesis in thyroid carcinoma cells.     

Green tea catechin inhibits ephrin-A1-mediated cell migration and angiogenesis of human umbilical vein endothelial cells

Angiogenesis, the formation of new blood vessels from preexisting capillaries, is essential for tumor progression and metastasis. During tumor neovascularization, vascular endothelial growth factor and ephrin (Eph) families emerge as critical mediators of angiogenesis. The green tea catechin epigallocatechin gallate (EGCG), a tyrosine kinase inhibitor, has been demonstrated in previous studies to be an effective antiangiogenesis agent. However, the inhibitory effect of green tea catechins on ephrin-A1-mediated tumor angiogenesis has not been demonstrated yet. Thus, in this study, we investigated the molecular mechanism of ephrin-A1-mediated cell migration and angiogenesis, as well as the inhibitory effects of EGCG. Here we show that ephrin-A1 mediates endothelial cell migration and regulates vascular remodeling in tumor neovascularization in vitro. We also demonstrated that ephrin-A1-mediated cell migration required the activation of extracellular-regulated kinase (ERK-1/2) but not of phosphatidylinositol-3-kinase. The green tea catechin EGCG inhibited ephrin-A1-mediated endothelial cell migration, as well as tumor angiogenesis, in a dose-dependent manner. Furthermore, EGCG inhibited the ephrin-A1-mediated phosphorylation of EphA2 and ERK-1/2. Taken together, these data indicated that activation of ERK-1/2 plays an essential role in ephrin-A1-mediated cell migration. EGCG inhibited ephrin-A1-mediated endothelial migration and angiogenesis. It suggests a novel antiangiogenesis application of EGCG in cancer chemoprevention.     

Impairment of VEGF-A-stimulated lamellipodial extensions and motility of vascular endothelial cells by chondromodulin-I, a cartilage-derived angiogenesis inhibitor

Chondromodulin-I (ChM-I) is a cartilage-derived angiogenesis inhibitor that has been identified as inhibitory to the growth activity of vascular endothelial cells. In our present study, we demonstrate the anti-angiogenic activity of recombinant human ChM-I (rhChM-I) in mouse corneal angiogenesis and examine its action. We focus on the VEGF-A-induced migration of vascular endothelial cells, a critical regulatory step in angiogenesis. In a modified Boyden chamber assay, nanomolar concentrations of rhChM-I inhibited the chemotactic migration of human umbilical vein endothelial cells (HUVECs) induced by VEGF-A as well as by FGF-2 and IGF-I. The ChM-I action was found to be endothelial cell-specific and independent of cell adhesions. Time-lapse analysis further revealed that rhChM-I markedly reduces VEGF-A-stimulated motility of HUVECs and causes frequent alterations of the moving front due to the appearance of multiple transient protrusions. This action involved the inhibition of cell spreading and the disrupted reorganization of the actin cytoskeleton upon VEGF-A stimulation. Consistent with these observations, rhChM-I was found to significantly reduce the activity of Rac1/Cdc42 during cell spreading, and the VEGF-A-induced Rac1 activity but not its basal activity in quiescent cells. Taken together, our present data suggest that ChM-I impairs the VEGF-A-stimulated motility of endothelial cells by destabilizing lamellipodial extensions.     

The nonreceptor protein-tyrosine kinase c-Fes is involved in fibroblast growth factor-2-induced chemotaxis of murine brain capillary endothelial cells

Fibroblast growth factor-2 (FGF-2)-induced migration of endothelial cells is involved in angiogenesis in vivo. However, signal transduction pathways leading to FGF-2-induced chemotaxis of endothelial cells are largely unknown. Previous studies have shown that the cytoplasmic protein-tyrosine kinase c-Fes is expressed in vascular endothelial cells and may influence angiogenesis in vivo. To investigate the contribution of c-Fes to FGF-2 signaling, we expressed wild-type or kinase-inactive human c-Fes in the murine brain capillary endothelial cell line, IBE (Immortomouse brain endothelial cells). Wild-type c-Fes was tyrosine-phosphorylated upon FGF-2-stimulation in transfected cells, whereas kinase-inactive c-Fes was not. Overexpression of wild-type c-Fes promoted FGF-2-independent tube formation of IBE cells. Tube formation was not observed with endothelial cells expressing kinase-inactive c-Fes, indicating a requirement for c-Fes kinase activity in this biological response. Expression of kinase-defective c-Fes suppressed endothelial cell migration following FGF-2 treatment, suggesting that activation of endogenous c-Fes may be required for the chemotactic response. Expression of either wild-type c-Fes or the kinase-inactive mutant did not affect the tyrosine phosphorylation FRS2, Shc, or phospholipase C-gamma, nor did it influence the kinetics of mitogen-activated protein kinase activation. These results implicate c-Fes in FGF-2-induced chemotaxis of endothelial cells through signaling pathways not linked to mitogenesis.     

Stilbene glycosides are natural product inhibitors of FGF-2-induced angiogenesis

Background  

Angiogenesis, the growth of new blood vessels from the pre-existing vasculature is associated with pathological processes, in particular tumour development, and is a target for the development of new therapies. We have investigated the anti-angiogenic potential of two naturally occurring stilbene glycosides (compounds 1 and 2) isolated from the medicinal plant Boswellia papyriferai using large and smallvessel-derived endothelial cells. Compound 1 (trans-4',5'-dihydroxy-3-methoxystilbene-5-O-{α-L-rhamnopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→6)}-β-D-glucopyranoside was the more hydrophilic and inhibited FGF-2-induced proliferation, wound healing, invasion in Matrigel, tube formation and angiogenesis in large and small vessel-derived endothelial cells and also in the chick chorioallantoic membrane assay. Using a binding assay we were able to show compound 1 reduced binding of FGF-2 to fibroblast growth factor receptors-1 and -2. In all cases the concentration of compound 1 which caused 50% inhibition (IC₅₀) was determined. The effect of compound 1 on EGF and VEGF-induced proliferation was also investigated.     

Targeting vascular NADPH oxidase 1 blocks tumor angiogenesis through a PPARα mediated mechanism

Reactive oxygen species, ROS, are regulators of endothelial cell migration, proliferation and survival, events critically involved in angiogenesis. Different isoforms of ROS-generating NOX enzymes are expressed in the vasculature and provide distinct signaling cues through differential localization and activation. We show that mice deficient in NOX1, but not NOX2 or NOX4, have impaired angiogenesis. NOX1 expression and activity is increased in primary mouse and human endothelial cells upon angiogenic stimulation. NOX1 silencing decreases endothelial cell migration and tube-like structure formation, through the inhibition of PPARα, a regulator of NF-κB. Administration of a novel NOX-specific inhibitor reduced angiogenesis and tumor growth in vivo in a PPARα dependent manner. In conclusion, vascular NOX1 is a critical mediator of angiogenesis and an attractive target for anti-angiogenic therapies.     

Genetic alteration of endothelial heparan sulfate selectively inhibits tumor angiogenesis

To examine the role of endothelial heparan sulfate during angiogenesis, we generated mice bearing an endothelial-targeted deletion in the biosynthetic enzyme N-acetylglucosamine N-deacetylase/N-sulfotransferase 1 (Ndst1). Physiological angiogenesis during cutaneous wound repair was unaffected, as was growth and reproductive capacity of the mice. In contrast, pathological angiogenesis in experimental tumors was altered, resulting in smaller tumors and reduced microvascular density and branching. To simulate the angiogenic environment of the tumor, endothelial cells were isolated and propagated in vitro with proangiogenic growth factors. Binding of FGF-2 and VEGF(164) to cells and to purified heparan sulfate was dramatically reduced. Mutant endothelial cells also exhibited altered sprouting responses to FGF-2 and VEGF(164), reduced Erk phosphorylation, and an increase in apoptosis in branching assays. Corresponding changes in growth factor binding to tumor endothelium and apoptosis were also observed in vivo. These findings demonstrate a cell-autonomous effect of heparan sulfate on endothelial cell growth in the context of tumor angiogenesis.     

The Polyclonal Antibodies Induced by VBP3 Complex Peptide Targeting Angiogenesis and Tumor Suppression

Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) play a critical role in tumor-associated angiogenesis and have become the targets of anti-tumor therapy. The BALB/c mice were immunized with VEGF/bFGF complex peptide (VBP3) constructed with different epitope peptides of human VEGF and bFGF. The results of the immunogenicity showed that the VBP3 could effectively stimulate immune response in mice and elicit the mice to produce high titer specific anti-VEGF and anti-bFGF antibodies (anti-VBP3 antibodies). The polyclonal anti-VBP3 antibodies separated from the mouse immune serum could effectively inhibit the proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVECs) and block the proliferation and migration of lung cancer A549 cells. Besides, the anti-VBP3 antibodies could effectively inhibit tumor growth and tumor angiogenesis in BABL/c nude mice. The results demonstrated that the VBP3 complex peptide could elicit the body to produce the high titer anti-VEGF and anti-bFGF antibodies, which showed anti-tumor and anti-angiogenic effects in vitro and in vivo. The results revealed that the VBP3 complex peptide could be used as a potential peptide vaccine in tumor therapy.     

Inhibition of endothelial cell proliferation by platelet factor-4 involves a unique action on S phase progression

Modulation of endothelial cell proliferation and cell cycle progression by the "chemokine" platelet factor-4 (PF-4) was investigated. PF-4 inhibited DNA synthesis, as well as proliferation of endothelial cells derived from large and small blood vessels. Inhibition by PF-4 was independent of the type and the concentration of stimuli used for the induction of endothelial cell proliferation. Inhibition of cell growth by PF-4 was reversible. The effects of PF-4 were antagonized by heparin. Cell cycle analysis using [3H]thymidine pulse labeling during traverse of synchronous cells from G0/G1 to S phase revealed that addition of PF-4 during G1 phase completely abolished the entry of cells into S phase. In addition, PF-4 also inhibited DNA synthesis in cells that were already in S phase. In exponentially growing cells, addition of PF-4 resulted in an accumulation of > 70% of the cells in early S phase, as determined by FACS (Becton-Dickinson Immunocytometry Systems, Mountain View, CA). In cells synchronized in S phase by hydroxyurea and then released, addition of PF-4 promptly blocked further progression of DNA synthesis. These results demonstrate that in G0/G1-arrested cells, PF-4 inhibited entry of endothelial cells into S phase. More strikingly, our studies have revealed a unique mode of endothelial cell growth inhibition whereby PF-4 effectively blocked cell cycle progression during S phase.     

Insulin-like growth factor binding protein-4 differentially inhibits growth factor-induced angiogenesis

An in-depth understanding of the molecular and cellular complexity of angiogenesis continues to advance as new stimulators and inhibitors of blood vessel formation are uncovered. Gaining a more complete understanding of the response of blood vessels to both stimulatory and inhibitory molecules will likely contribute to more effective strategies to control pathological angiogenesis. Here, we provide evidence that endothelial cell interactions with structurally altered collagen type IV may suppress the expression of insulin-like growth factor binding protein-4 (IGFBP-4), a well documented inhibitor of the IGF-1/IGF-1R signaling axis. We report for the first time that IGFBP-4 differentially inhibits angiogenesis induced by distinct growth factor signaling pathways as IGFBP-4 inhibited FGF-2- and IGF-1-stimulated angiogenesis but failed to inhibit VEGF-induced angiogenesis. The resistance of VEGF-stimulated angiogenesis to IGFBP-4 inhibition appears to depend on sustained activation of p38 MAPK as blocking its activity restored the anti-angiogenic effects of IGFBP-4 on VEGF-induced blood vessel growth in vivo. These novel findings provide new insight into how blood vessels respond to endogenous inhibitors during angiogenesis stimulated by distinct growth factor signaling pathways.     

Endostatin inhibits adhesion of endothelial cells to collagen I via alpha(2)beta(1) integrin, a possible cause of prevention of chondrosarcoma growth

Endostatin derived from collagen XVIII is a potent endogenous anti-angiogenic factor that induces regression of various tumors of epithelial origin. Endostatin has been shown to inhibit endothelial cell functions, however, its effect remains controversial. We first attempted here to apply the inhibitory effect of recombinant human endostatin on chondrosarcomas, which originate from the mesenchyme, in nude mice. Endostatin induced reduction of chondrosarcoma growth and tumor angiogenesis in vivo. However, endostatin showed no effect on the proliferation and migration of chondrosarcoma cells in vitro. Next, we investigated the interactions between endostatin and endothelial cells in detail. Endostatin inhibited the migration on and attachment to collagen I but did not affect the proliferation of endothelial cells. Although the migration of endothelial cells was stimulated by angiogenic factors such as basic fibroblast growth factor and vascular endothelial growth factor, endostatin showed similar inhibitory effects on it in the presence and absence of the stimulants. Moreover, the inhibitory effect against endothelial cell attachment to collagen I was attenuated or modulated in the presence of neutralizing antibodies of alpha(2), alpha(5)beta(1), and alpha(V)beta(3) integrins but not that of alpha(1) integrin. Our results suggest that endostatin might suppress the alpha(2)beta(1) integrin function of endothelial cells via alpha(5)beta(1) or alpha(V)beta(3) integrin. We propose here that endostatin might be effective for anti-angiogenic therapy for human chondrosarcomas through the suppression of alpha(2)beta(1) integrin functions in endothelial cells.     

Upregulation of fibroblast growth factor-2 by visfatin that promotes endothelial angiogenesis

Adipokines have been known to act as angiogenic regulators in the process of angiogenesis. Recently, we have demonstrated that visfatin, a novel adipokine, has angiogenic activity. However, little has been reported on the underlying mechanism of visfatin-induced angiogenesis. In this study, we report that visfatin-induced angiogenesis is mediated by endothelial fibroblast growth factor-2 (FGF-2). Visfatin increased the levels of FGF-2 mRNA and protein in human endothelial cells. The enhancement in FGF-2 expression was prevented by an inhibitor of the extracellular signal-regulated kinase 1/2 (Erk1/2) pathway. Furthermore, visfatin-induced angiogenesis was reduced by inhibition of FGF-2 receptor kinase or by neutralization of FGF-2 function. Taken together, our results indicate that visfatin-induced endothelial angiogenesis is composed largely of two sequential steps: the induction of Erk1/2-dependent FGF-2 gene expression by visfatin and the subsequent FGF-2-induced angiogenesis. These data further suggest an integral role for visfatin-FGF-2 signaling axis in modulating endothelial angiogenesis.