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PDF file, 2456K, Proliferation curves of HUVEC as generated by xCELLigence RTCA seeding 2x103 cells/well during a period of 72 hours, in the presence of 8% FBS, or 40ng/ml VEGF plus or minus 10 muM ERFR, 10nM RERF or 10 muM RERF. Data are the mean+SD of one experiment, performed in quadruplicate.

The receptor for the urokinase-type plasminogen activator (uPAR) is a widely recognized master regulator of cell migration, and uPAR88–92 is the minimal sequence required to induce cell motility. We previously showed that soluble forms of uPAR elicit angiogenic responses through their uPAR88–92 chemotactic sequence and that the synthetic peptide SRSRY exerts similar effects. By a drug design approach, based on the conformational analysis of the uPAR88–92 sequence, we developed peptides (pERERY, RERY, and RERF) that potently inhibit signaling triggered by uPAR88–92. In this study, we present evidence that these peptides are endowed also with a clear-cut antiangiogenic activity, although to different extents. The most active, RERF, prevents tube formation by human endothelial cells exposed to SRSRY. RERF also inhibits VEGF-triggered endothelial cell migration and cord-like formation in a dose-dependent manner, starting in the femtomolar range. RERF prevents F-actin polymerization, recruitment of αvβ3 integrin at focal adhesions, and αvβ3/VEGFR2 complex formation in endothelial cells exposed to VEGF. At molecular level, the inhibitory effect of RERF on VEGF signaling is shown by the decreased amount of phospho-FAK and phospho-Akt in VEGF-treated cells. In vivo, RERF prevents VEGF-dependent capillary sprouts originating from the host vessels that invaded angioreactors implanted in mice and neovascularization induced by subcorneal implantation of pellets containing VEGF in rabbits. Consistently, RERF reduced the growth and vascularization rate of tumors formed by HT1080 cells injected subcutaneously in the flanks of nude mice, indicating that RERF is a promising therapeutic agent for the control of diseases fuelled by excessive angiogenesis such as cancer. Mol Cancer Ther; 12(10); 1981–93. ©2013 AACR.

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High levels of urokinase receptor (uPAR) in tissue and serum of patients with chondrosarcoma correlate with poor prognosis. First, we analyzed the uPAR levels in tissues and plasma of five patients affected by chondrosarcoma. Interestingly, very high levels of uPAR and its soluble forms (SuPAR) were found on tumor cell surfaces and plasma, respectively, of two patients with lung metastases. Therefore, to investigate the role of SuPAR in chondrosaromas, we generated a primary cell culture from a chondrosarcoma tissue overexpressing uPAR on cell surfaces. We found that chondrosarcoma-like primary culture cells release a large amount of SuPAR in the medium.In vitro, SuPAR elicits chondrosarcoma cell migration likely through its uPAR88-92sequence, since the DII88-183or DIIDIIR88-284uPAR domains retain motogen effect whereas DI1-87or DIII184-284domains, both lacking the uPAR88-92sequence, are ineffective. Chondrosarcoma cells cross matrigel in response to SuPAR, and their invasion capability is abrogated by RERF peptide which inhibits uPAR88-92signalling. These findings assign a role to uPAR in mobilizing chondrosarcoma cells and suggest that RERF peptide may be regarded as a prototype to generate new therapeutics for the chondrosarcoma treatment.

The receptor for the urokinase-type plasminogen activator (uPAR) is a widely recognized master regulator of cell migration, and uPAR88–92 is the minimal sequence required to induce cell motility. We previously showed that soluble forms of uPAR elicit angiogenic responses through their uPAR88–92 chemotactic sequence and that the synthetic peptide SRSRY exerts similar effects. By a drug design approach, based on the conformational analysis of the uPAR88–92 sequence, we developed peptides (pERERY, RERY, and RERF) that potently inhibit signaling triggered by uPAR88–92. In this study, we present evidence that these peptides are endowed also with a clear-cut antiangiogenic activity, although to different extents. The most active, RERF, prevents tube formation by human endothelial cells exposed to SRSRY. RERF also inhibits VEGF-triggered endothelial cell migration and cord-like formation in a dose-dependent manner, starting in the femtomolar range. RERF prevents F-actin polymerization, recruitment of αvβ3 integrin at focal adhesions, and αvβ3/VEGFR2 complex formation in endothelial cells exposed to VEGF. At molecular level, the inhibitory effect of RERF on VEGF signaling is shown by the decreased amount of phospho-FAK and phospho-Akt in VEGF-treated cells. In vivo, RERF prevents VEGF-dependent capillary sprouts originating from the host vessels that invaded angioreactors implanted in mice and neovascularization induced by subcorneal implantation of pellets containing VEGF in rabbits. Consistently, RERF reduced the growth and vascularization rate of tumors formed by HT1080 cells injected subcutaneously in the flanks of nude mice, indicating that RERF is a promising therapeutic agent for the control of diseases fuelled by excessive angiogenesis such as cancer. Mol Cancer Ther; 12(10); 1981–93. ©2013 AACR.

The receptor for urokinase-type plasminogen activator (uPAR) plays an important role in controlling cell migration. uPAR binds urokinase and vitronectin extracellular ligands, and signals in complex with transmembrane receptors such as Formyl-peptide Receptors (FPR)s and integrins. Previous work from this laboratory has shown that synthetic peptides, corresponding to the uPAR(88-92) chemotactic sequence, when carrying the S90P or S90E substitutions, up- or down-regulate cell migration, respectively. To gain mechanistic insights into these opposite cell responses, the functional consequences of S90P and S90E mutations in full-length uPAR were evaluated. First, (HEK)-293 embryonic kidney cells expressing uPAR(S90P) exhibit enhanced FPR activation, increased random and directional cell migration, long-lasting Akt phosphorylation, and increased adhesion to vitronectin, as well as uPAR/vitronectin receptor association. In contrast, the S90E substitution prevents agonist-triggered FPR activation and internalization, decreases binding and adhesion to vitronectin, and inhibits uPAR/vitronectin receptor association. Also, 293/uPAR(S90P) cells appear quite elongated and their cytoskeleton well organized, whereas 293/uPAR(S90E) cells assume a large flattened morphology, with random orientation of actin filaments. Interestingly, when HT1080 cells co-express wild type uPAR with uPAR S90E, the latter behaves as a dominant-negative, impairing uPAR-mediated signaling and reducing cell wound repair as well as lung metastasis in nude mice. In contrast, signaling, wound repair and in vivo lung metastasis of HT1080 cells bearing wild type uPAR are enhanced when they co-express uPAR(S90P). In conclusion, our findings indicate that Ser(90) is a critical residue for uPAR signaling and that the S90P and S90E exert opposite effects on uPAR activities. These findings may be accommodated in a molecular model, in which uPAR(S90E) and uPAR(S90P) are forced into inactive and active forms, respectively, suggesting important implications for the development of novel drugs targeting uPAR function.

Summary. Background: The urokinase plasminogen activator receptor (u-PAR) focuses the proteolytic activity of the urokinase plasminogen activator (u-PA) on the endothelial cell surface, thus promoting angiogenesis in a protease-dependent manner. The u-PAR may exist in a glycophosphatidylinositol-anchored and in a soluble form (soluble u-PAR [Su-PAR]), both including the chemotactic Ser88-Arg-Ser-Arg-Tyr92 internal sequence. Objective: To investigate whether Su-PAR may trigger endothelial cell signaling leading to new vessel formation through its chemotactic Ser88-Arg-Ser-Arg-Tyr92 sequence. Methods and Results: In this study, the formation of vascular-like structures by human umbilical vein endothelial cells was assessed by using a matrigel basement membrane preparation. First, we found that Su-PAR protein promotes the formation of cord-like structures, and that this ability is retained by the isolated Ser88-Arg-Ser-Arg-Tyr92 chemotactic sequence, the maximal effect being reached at 10 nmol L−1 SRSRY peptide (SRSRY). This effect is mediated by the αvβ3 vitronectin receptor, is independent of u-PA proteolytic activity, and involves the internalization of the G-protein-coupled formyl-peptide receptor in endothelial cells. Furthermore, exposure of human saphenous vein rings to Su-PAR or SRSRY leads to a remarkable degree of sprouting. Finally, we show that Su-PAR and SRSRY promote a marked response in angioreactors implanted into the dorsal flank of nude mice, retaining 91% and 66%, respectively, of the angiogenic response generated by a mixture of vascular endothelial growth factor and fibroblast growth factor type 2. Conclusions: Our results show a new protease-independent activity of Su-PAR that stimulates in vivo angiogenesis through its Ser88-Arg-Ser-Arg-Tyr92 chemotactic sequence.

The urokinase-type plasminogen activator receptor (uPAR) plays a central role in sustaining the malignant phenotype and promoting tumor metastasis. The Ser88-Arg-Ser-Arg-Tyr92 is the minimum chemotactic sequence of uPAR required to induce the same intracellular signaling as its ligand uPA. Here, we describe the generation of new peptide inhibitors of cell migration and invasion derived from SRSRY by a drug design approach. Ac-Arg-Glu-Arg-Phe-NH2 (i.e., RERF), which adopts a turned structure in solution, was selected for its ability to potently prevent SRSRY-directed cell migration. Fluorescein-RERF associates with very high affinity to RBL-2H3 rat basophilic leukemia cells expressing the human formyl peptide receptor (FPR). Accordingly, femtomolar concentrations of RERF prevent agonist-dependent internalization of FPR and inhibit N-formyl-Met-Leu-Phe–dependent migration in a dose-dependent manner. In the absence of FPR, fluorescein-RERF binds to cell surface at picomolar concentrations in an αv integrin–dependent manner. The involvement of vitronectin receptor is further supported by the findings that 100 pmol/L RERF selectively inhibits vitronectin-dependent RBL-2H3 cell migration and prevents SRSRY-triggered uPAR/αv association. Furthermore, RERF reduces the speed of wound closure and the extent of Matrigel invasion by human fibrosarcoma HT1080 cells without affecting cell proliferation. Finally, a 3- to 5-fold reduction of lung metastasis number and size in nude mice following i.v. injection of green fluorescent protein–expressing HT1080 cells in the presence of 3.32 mg/kg RERF is observed. Our findings indicate that RERF effectively prevents malignant cell invasion in vivo with no signs of toxicity and may represent a promising prototype drug for anticancer therapy. [Mol Cancer Ther 2009;8(9):2708–17]

Human beta-defensin-2 (hBD-2) is an antimicrobial peptide which is released upon microbial invasion and contributes to mucosal and epithelial defense modulating both innate and adaptive immunity. We found that hBD-2 stimulates chemotaxis of human endothelial cells with an extent similar to that exerted by the vascular endothelial growth factor (VEGF). The hBD-2-dependent chemotaxis is dose-dependent, maximal effect being reached at 500 ng/ml concentration. In the absence of any growth factor, hBD-2 favors wound healing of endothelial cells, causing an about 2-fold increase in the speed of wound closure with respect to the control. Furthermore, hBD-2 promotes endothelial cell proliferation, although at a minor extent as compared to VEGF. When plated on matrigel enriched with angiogenic factors, endothelial cells form a three-dimensional network of tubes that gives rise to capillary-like structures. Similarly to VEGF, hBD-2 promotes capillary-like tube formation of human endothelial cells. Pro-angiogenic effect promoted by hBD-2 is dose-dependent, peaks at a 500 ng/ml hBD-2 concentration and is prevented by blocking anti-alphavbeta3 monoclonal antibody. However, hBD-2-induced pro-angiogenic activity is not due to endogenously produced VEGF because it is not prevented by neutralizing anti-VEGF antibodies. Overall, our findings suggest that hBD-2 could link inflammation and the host defense through its pro-angiogenic activity.

Aims and Background The prognosis of each individual patient affected by sarcoma, including those with low histopathologic grading, cannot be reliably predicted at the time of surgery. We have developed an in vitro cell invasion assay on early primary cell cultures derived from surgically removed sarcomas. Methods Primary cell cultures were subjected to in vitro cell invasion assays by using Boyden chambers, filters coated with matrigel and fetal bovine serum as a source of chemoattractant. For each primary cell culture, the sarcoma cell invasion index was determined in comparison with the percentage of human fibrosarcoma HT1080 cell invasion extent. The cell invasion index of 7 different sarcomas was evaluated in respect to the outcome of the disease, after a follow-up ranging from 14 to 48 months. Results Data evidenced that a low cell invasion index (39.7% ± 8.9) was retained by tumor cells derived from patients with no progression of the disease and with a longer interval of disease-free survival (21 ± 0.8 months). However, an increase in cell invasion index (61% ± 5) was retained by tumor cells derived from patients with progression of the disease and with a shorter disease-free survival (9 ± 3 months). Overall, although only 7 cases were analyzed, a statistically significant correlation was found between disease-free survival and cell invasion index (P = 0.003). Conclusions Our data support the possibility that cell invasion assays performed in vitro on cells derived from human sarcomas may be predictive of a more aggressive form of the disease.

Urokinase receptor (uPAR) plays a key role in physiological and pathological processes sustained by an altered cell migration. We have developed peptides carrying amino acid substitutions along the Ser 88 -Arg-Ser-Arg-Tyr 92 (SRSRY) uPAR chemotactic sequence. The peptide pyro glutamic acid (pGlu)-Arg-Glu-Arg-Tyr-NH2 (pERERY-NH 2 ) shares the same binding site with SRSRY and competes with N -formyl-Met-Leu-Phe (fMLF) for binding to the G-protein-coupled N -formyl-peptide receptor (FPR). pERERY-NH 2 is a dose-dependent inhibitor of both SRSRY- and fMLF-directed cell migration, and prevents agonist-induced FPR internalization and fMLF-dependent ERK1/2 phosphorylation. pERERY-NH 2 is a new and potent uPAR inhibitor which may suggest the generation of new pharmacological treatments for pathological conditions involving increased cell migration.

The serine protease urokinase (uPA) binds to the urokinase receptor (uPAR) through its growth-factor domain (GFD, residues 1-49), affecting cell migration, adhesion and growth. Here, we show that uPA can promote cytoskeletal rearrangements and directional cell migration in a GFD-independent manner, through a new and specific interaction between an internal uPA domain coined ;connecting peptide' (residues 132-158) and cell-surface integrin alpha v beta 5. Remarkably, a peptide corresponding to this region (CPp, residues 135-158) retains the ability to bind to alpha v beta 5, eliciting cytoskeletal rearrangements and directing cell migration at a concentration as low as 1-10 pM. These effects are lost in cells not expressing uPAR, indicating that the uPAR is required for CPp-dependent signaling. Furthermore, the CPp-alpha v beta 5-integrin interaction enhances F-actin-enriched protrusions and cell migration induced by the well-established interaction between the uPAR-binding peptide (GFDp, residues 12-32) of uPA and uPAR. These results provide new insight into the function of uPA, which--through individual domains--can engage two different surface receptors (uPAR and alpha v beta 5 integrin), thus initiating and potentiating intracellular signaling and migration.

The urokinase-type plasminogen activator receptor (uPAR) sustains cell migration through its capacity to promote pericellular proteolysis, regulate integrin function, and mediate chemotactic signaling in response to urokinase. We have characterized the early signaling events triggered by the Ser-Arg-Ser-Arg-Tyr (SRSRY) chemotactic uPAR sequence. Cell exposure to SRSRY peptide promotes directional migration on vitronectin-coated filters, regardless of uPAR expression, in a specific and dose-dependent manner, with maximal effect at a concentration level as low as 10 nm. A similar concentration profile is observed in a quantitative analysis of SRSRY-dependent cytoskeletal rearrangements, mostly consisting of filamentous structures localized in a single cell region. SRSRY analogues with alanine substitutions fail to drive F-actin formation and cell migration, indicating a critical role for each amino acid residue. As with ligand-dependent uPAR signaling, SRSRY stimulates protein kinase C activity and results in ERK1/2 phosphorylation. The involvement of the high affinity N-formyl-Met-Leu-Phe receptor (FPR) in this process is indicated by the finding that 100 nm N-formyl-Met-Leu-Phe inhibits binding of D2D3 to the cell surface, as well as SRSRY-stimulated cell migration and F-actin polarization. Moreover, cell exposure to SRSRY promotes FPR-dependent vitronectin release and increased uPAR.alphavbeta5 vitronectin receptor physical association, indicating that alphavbeta5 activity is regulated by the SRSRY uPAR sequence via FPR. Finally, we provide evidence that alphavbeta5 is required for SRSRY-dependent ERK1/2 phosphorylation, whereas it is not required for protein kinase C activation. The data indicate that the ability of uPAR to stimulate cell migration and cytoskeletal rearrangements is retained by the SRSRY peptide alone and that it is supported by cross-talk between FPR and alphavbeta5.

We have previously shown that urokinase receptor physically and functionally interacts with alpha(v)beta5 vitronectin receptor, leading to tumor breast cell migration and invasion. Here, the link between these 2 receptors was further investigated by analyzing the expression levels of urokinase receptor and alpha(v)beta5 integrin in 35 human breast carcinomas and 5 benign breast lesions. The occurrence of a positive correlation between urokinase receptor and alpha(v)beta5 protein levels in benign and malignant tumor specimens prompted us to investigate whether engaged urokinase receptors might modulate alpha(v)beta5 expression. Here, we report the receptor-dependent ability of catalytically inactive urokinase to upregulate the alpha(v) and beta5 chains in MDA-MB-231 and MCF-7 breast carcinoma cell lines in a time- and concentration-dependent manner. This effect is dependent on protein kinase C activity and requires new protein synthesis. Accordingly, the availability of assembled alpha(v)beta5 receptors on the cell surface increases upon urokinase treatment, as shown by immunoprecipitation and immunocytochemical analyses. Exposure to urokinase leads to enhanced tumor cell migration and invasion, which is prevented by the "phosphorylation-like" urokinase receptor antagonist His-uPA(138E/303E), the DNA-binding drug mithramycin, the protein kinase C inhibitor calphostin C and anti-alpha(v)beta5 antibodies. Finally, urokinase enables benign breast MCF-10A cells to cross Matrigel in a alpha(v)beta5- and urokinase receptor-dependent manner, indicating that urokinase controls a regulatory circuitry crucial to breast tumor progression.

Urokinase (uPA) is a 411 residues serine protease originally identified for its ability to activate plasminogen and generate plasmin, a broad-spectrum matrix- and fibrin-degrading enzyme. Later, this protease has been shown to possess also a clear-cut ability to stimulate cell migration and survival in a catalytic-independent manner. This activity turned out to be exerted through the growth factor-like domain (GFD-like, residues 1-49) of the protease binding to a GPI-anchored membrane receptor (uPAR), in complex with transmembrane receptors such as integrins, the epidermal growth factor and the formyl-peptide receptors. Direct binding of uPA to integrins through its kringle (residues 50-131) and connecting peptide (residues 132-158) regions results in enhanced migration. The dual function of uPA in promoting migration while reducing the physical resistance of extracellular matrix underlies its crucial role in the invasion of malignant tumours. Consolidated evidence emerging from animal models and clinical studies shows that the overexpression of uPA is a causal determinant to tumour metastasis and is associated to a poor prognosis. Therefore, pinpointing the molecular interactions and identifying novel agents to interfere with the diverse activities of uPA is a goal of basic and applied research. In this review, we discuss the general theme of cell migration and invasion. A description of the uPA structure-function relationship and the functional effects of isolated domains is presented. Current information on molecular agonistic as well as antagonistic compounds, including the compounds which have reached clinical trials, is provided. © 2011 Bentham Science Publishers.