Biomedical subjects

Andreas Bikfalvi

Publications and source records attributed to Andreas Bikfalvi.

At least 19 recordsLinked to original sources

PubMed2007

PF-4/CXCL4 and CXCL4L1 exhibit distinct subcellular localization and a differentially regulated mechanism of secretion.

PF-4/CXCL4 is a member of the CXC chemokine family, which is mainly produced by platelets and known for its pleiotropic biological functions. Recently, the proteic product of a nonallelic variant gene of CXCL4 was isolated from human platelets and named as CXCL4L1. CXCL4L1 shows only 4.3% amino acid divergence in the mature protein, but exhibits a 38% amino acid divergence in the signal peptide region. We hypothesized that this may imply a difference in the cell type in which CXCL4L1 is expressed or a difference in its mode of secretion. In different types of transfected cells, CXCL4 and CXCL4L1 exhibited a distinct subcellular localization and a differential regulation of secretion, CXCL4 being stored in secretory granules and released in response to protein kinase C activation, whereas CXCL4L1 was continuously synthesized and secreted through a constitutive pathway. A protein kinase C-regulated CXCL4 secretion was observed also in lymphocytes, a cell type expressing mainly CXCL4 mRNA, whereas smooth muscle cells, which preferentially expressed CXCL4L1, exhibited a constitutive pathway of secretion. These results demonstrate that CXCL4 and CXCL4L1 exhibit a distinct subcellular localization and are secreted in a differentially regulated manner, suggesting distinct roles in inflammatory or homeostatic processes.

Cells, Cultured↗

PubMed2006

Dominant-negative fibroblast growth factor receptor expression enhances antitumoral potency of oncolytic herpes simplex virus in neural tumors.

PURPOSE: Oncolytic herpes simplex viruses (HSV) appear to be a promising platform for cancer therapy. However, efficacy as single agents has thus far been unsatisfactory. Fibroblast growth factor (FGF) signaling is important for the growth and migration of endothelial and tumor cells. Here, we examine the strategy of arming oncolytic HSV with a dominant-negative FGF receptor (dnFGFR) that targets the FGF signaling pathway. EXPERIMENTAL DESIGN: A mouse Nf1:p53 malignant peripheral nerve sheath tumor (MPNST) cell line expressing dnFGFR was generated by transfection. The effects of dnFGFR expression on cell growth and migration in vitro and tumor formation in vivo were determined. The dnFGFR transgene was then inserted into oncolytic HSV G47Delta using a bacterial artificial chromosome construction system. Antitumoral and antiangiogenic activities of bG47Delta-dnFGFR were examined. RESULTS: MPNST 61E4 cells expressing dnFGFR grew less well than parental control cells. bG47Delta-dnFGFR showed enhanced killing of both tumor (human U87 glioma and F5 malignant meningioma cells and murine MPNST 61E4 and 37-3-18-4 cells) and proliferating endothelial cells (human umbilical vascular endothelial cell and Py-4-1) in vitro compared with the control vector bG47Delta-empty without inhibiting viral replication. In vivo, bG47Delta-dnFGFR was more efficacious than its nonexpressing parent bG47Delta-empty at inhibiting tumor growth and angiogenesis in both human U87 glioma and mouse 37-3-18-4 MPNST tumors in nude mice. CONCLUSIONS: By using multiple therapeutic mechanisms, including destruction of both tumor cells and tumor endothelial cells, an oncolytic HSV encoding dnFGFR enhances antitumor efficacy. This strategy can be applied to other oncolytic viruses and for clinical translation.

Angiogenesis Inhibitors↗

PubMed2006

Effect of PEX, a noncatalytic metalloproteinase fragment with integrin-binding activity, on experimental Chlamydophila pneumoniae infection.

Chlamydophila pneumoniae is a pathogen that is involved in acute and chronic respiratory infections and that is associated with asthma and coronary artery diseases. In this study, we evaluated the effects of PEX, a noncatalytic metalloproteinase fragment with integrin-binding activity, against experimental infections caused by C. pneumoniae. Moreover, we investigated the relationships between C. pneumoniae and alpha(v)beta(3) integrin functions in order to explain the possible mechanism of action of PEX both in vitro and in vivo. For the in vitro experiments, HeLa cells were infected with C. pneumoniae and treated with either PEX or azithromycin. The results obtained with PEX were not significantly different (P > 0.05) from those achieved with azithromycin. Similar results were also obtained in a lung infection model. Male C57BL/J6 mice inoculated intranasally with 10(6) inclusion-forming units of C. pneumoniae were treated with either PEX or azithromycin plus rifampin. Infected mice treated with PEX showed a marked decrease in C. pneumoniae counts versus those for the controls; this finding did not differ significantly (P > 0.05) from the results observed for the antibiotic-treated group. Integrin alpha(v)beta(3) plays an important role in C. pneumoniae infection. Blockage of integrin activation led to a significant inhibition of C. pneumoniae infection in HeLa cells. Moreover, CHO(DHFR) alpha(v)beta(3)-expressing cells were significantly (P < 0.001) more susceptible to C. pneumoniae infection than CHO(DHFR) cells. These results offer new perspectives on the treatment of C. pneumoniae infection and indicate that alpha(v)beta(3) could be a promising target for new agents developed for activity against this pathogen.

Animals↗

PubMed2005

Prox1 promotes lineage-specific expression of fibroblast growth factor (FGF) receptor-3 in lymphatic endothelium: a role for FGF signaling in lymphangiogenesis.

Fibroblast growth factors play important roles in angiogenesis, but their functions in lymphangiogenesis remain poorly understood. The homeodomain transcription factor Prox1 is essential for development of the lymphatic system by specifying lymphatic endothelial cell (LEC) fate. Here, we identify fibroblast growth factor (FGF) receptor (FGFR)-3 as a novel Prox1 target gene. Ectopic overexpression of Prox1 in blood vascular endothelial cells up-regulates FGFR-3. Prox1 induces the expression of the IIIc isoform, which we also found to be the major isoform of FGFR-3 expressed in LECs. This transcriptional activation is mediated by a direct binding of Prox1 to newly identified Prox1-response elements in the FGFR-3 promoter. Consistently, FGFR-3 is up-regulated in Prox1-positive newly formed lymphatic vessels during embryogenesis and its lymphatic-specific expression is maintained throughout development. We also found that FGF-1 and FGF-2 promote proliferation, migration, and survival of cultured LECs without involvement of vascular endothelial cell growth factor receptor-3. We show that FGF-2 binds to low- and high-affinity receptors on LECs and is efficiently internalized and processed. Moreover, functional inhibition of FGFR-3 using small interfering RNA represses LEC proliferation. Together, these results indicate that FGFR-3 is an initial target of Prox1 during the lymphatic cell fate specification and that FGF signaling may play an important role in lymphatic vessel development.

Animals↗

PubMed2005

Design, synthesis, and evaluation of original carriers for targeting vascular endothelial growth factor receptor interactions.

PURPOSE: Angiogenesis is a key event in tumor growth and metastasis, chronic inflammatory disease, and cardiovascular disease. It is controlled by positive and negative regulators, which include vascular endothelial growth factor (VEGF) as the most active of these. VEGF/VEGF receptors are important targets not only for therapy but also for imaging. Based on the structural study of VEGF, we developed a novel cyclopeptide (cyclo-VEGI) that exhibits powerful antitumor properties. We herein report the design of novel molecules derived from cyclo-VEGI as potential targeting agents in cancer and other angiogenesis-related diseases. METHODS: We performed selective chemical modification of the most active VEGF-derived cyclopeptide (cyclo-VEGI). Original hydrophilic linkers were synthesized and coupled to cyclo-VEGI. These reactions provide nanocarriers for delivery. The inhibitory effect of the different compounds on VEGF binding was evaluated in competition assays with 125I-VEGF. A fluorescent cyclo-VEGI peptide was synthezised to assess direct binding and internalization of cyclo-VEGI. RESULTS: Chemical modifications of cyclo-VEGI do not diminish the biological activity of cyclo-VEGI as measured in competition assays; in fact, it is even increased. Moreover there is a strong cellular accumulation of the fluorescent-labeled cyclo-VEGI. Conjugates synthesized in this study may be useful leads to design delivery systems for targeting approaches in cancer and other angiogenesis-related diseases. CONCLUSION: The modified cyclo-VEGIs may have a wide range of applications and represent a useful tool to develop delivery/carrier systems for therapeutic targeting or imaging.

Amino Acid Sequence↗

PubMed2005

Recent developments in the regulation of the angiogenic switch by cellular stress factors in tumors.

Angiogenesis in tumors is controlled by the so-called 'angiogenic switch' which allows the passage from low invasive and poorly vascularized tumors to highly invasive and angiogenic tumors. A number of cellular stress factors such as hypoxia, nutrient deprivation or inducers of reactive oxygen species (ROS) are important stimuli of angiogenic signalling. The HIF system plays a significant role in several of these effects and the molecular mechanisms of its regulation have recently been characterized. In addition, HIF-independent mechanisms have been described which involved number of other molecules and transcription factors such as nuclear factor-(kappa)B (NF-(kappa)B) and p53. p53 is an important intracellular mediator of the stress response and is now also recognized as a modifier of the angiogenic response. p53 may interact with the HIF system but may also have direct effects on angiogenesis regulators or interfere with translation mechanisms of angiogenesis factors.

Cell Hypoxia↗

PubMed2005

Accessing key steps of human tumor progression in vivo by using an avian embryo model.

Experimental in vivo tumor models are essential for comprehending the dynamic process of human cancer progression, identifying therapeutic targets, and evaluating antitumor drugs. However, current rodent models are limited by high costs, long experimental duration, variability, restricted accessibility to the tumor, and major ethical concerns. To avoid these shortcomings, we investigated whether tumor growth on the chick chorio-allantoic membrane after human glioblastoma cell grafting would replicate characteristics of the human disease. Avascular tumors consistently formed within 2 days, then progressed through vascular endothelial growth factor receptor 2-dependent angiogenesis, associated with hemorrhage, necrosis, and peritumoral edema. Blocking of vascular endothelial growth factor receptor 2 and platelet-derived growth factor receptor signaling pathways by using small-molecule receptor tyrosine kinase inhibitors abrogated tumor development. Gene regulation during the angiogenic switch was analyzed by oligonucleotide microarrays. Defined sample selection for gene profiling permitted identification of regulated genes whose functions are associated mainly with tumor vascularization and growth. Furthermore, expression of known tumor progression genes identified in the screen (IL-6 and cysteine-rich angiogenic inducer 61) as well as potential regulators (lumican and F-box-only 6) follow similar patterns in patient glioma. The model reliably simulates key features of human glioma growth in a few days and thus could considerably increase the speed and efficacy of research on human tumor progression and preclinical drug screening.

Animals↗

PubMed2005

Continuous delivery of endogenous inhibitors from poly(lactic-co-glycolic acid) polymeric microspheres inhibits glioma tumor growth.

PURPOSE: There is an urgent need for modalities that can localize and prolong the administration of the antitumor agents, particularly antiangiogenic, to achieve long-term tumor inhibition. However, one of the major obstacles is designing a device in which the biological activity of sensitive endogenous inhibitors is retained. We have designed a biodegradable polymeric device, which provides a unique and practical means of localizing and continuously delivering hemopexin (PEX) or platelet factor 4 fragment (PF-4/CTF) at the tumor site while maintaining their biological activity. The potential and efficacy of this system is shown in vitro and in vivo in a human glioma mouse model. EXPERIMENTAL DESIGN: Polymeric microspheres made of poly(lactic-co-glycolic acid) (PLGA) were loaded with very low amounts of PEX and PF-4/CTF. The release profiles of these factors from PLGA and their biological activity were confirmed in vitro using proliferation assays done on endothelial and tumor cells. Tumor inhibition using this system was studied in nude mice bearing a human s.c. glioma. RESULTS: PEX and PF-4/CTF released in vitro from PLGA microspheres were biologically active and significantly inhibited the proliferation of human umbilical vein endothelial cells, bovine capillary endothelial cells, and U87-MG cells. A single local s.c. injection of PLGA microspheres loaded with low amounts of PEX or PF-4/CTF resulted in an 88% and 95% reduction in glioma tumor volume 30 days post-treatment. Immunohistochemical analysis of the treated tumors showed a marked decrease in tumor vessel density compared with untreated tumors. CONCLUSION: Our findings show that polymeric microspheres are a very promising approach to locally and efficiently deliver endogenous inhibitors to the tumor site leading to a significant inhibition of the tumor.

Animals↗

PubMed2005

Molecular mechanisms of tumor vascularization.

Tumor angiogenesis is a fast growing sub-domain of angiogenesis research and tumor biology. Basic mechanisms have been unraveled and many key players identified. For many years, tumor vascularization was explained solely by the ingrowth of new vessels into the tumor from preexisting one's. However, in recent years, additional mechanisms have been recognized. These include angioblasts recruitment, cooption, vasculogenic mimicry and mosaic vessels. These different mechanisms may exist concomitantly in the same tumor or may be selectively involved in a specific tumor type or host environment. In this article, we will review, in depth, these different mechanisms and also discuss some aspects of anti-angiogenic tumor therapy.

Angiogenesis Inhibitors↗

PubMed2004

Recent developments in the inhibition of angiogenesis: examples from studies on platelet factor-4 and the VEGF/VEGFR system.

Inhibition of angiogenesis is an important strategy to block tumor growth and invasion. We discuss herein results from our ongoing investigations on platelet factor-4 (PF-4) and the VEGF/VEGFR system. Platelet factor-4 (PF-4) is an anti-angiogenic ELR-negative chemokine. PF-4 inhibits endothelial cell proliferation and migration, and angiogenesis in vitro and in vivo. We have studied the structure and anti-angiogenic activities of a C-terminal fragment of PF-4 named PF-4 CTF. This molecule retains anti-angiogenic activity, blocks the interaction of angiogenesis factors with their receptors and may also be improved by mutation or domain-swapping. It seems, therefore, to be a good candidate for further development. Furthermore, we have developed a cyclic vascular endothelial growth inhibitor (Cyclo VEGI) from the structure of VEGF-A. In aqueous solution, cyclo-VEGI adopts an alpha helix conformation. Cyclo-VEGI inhibits binding of iodinated VEGF(165) to endothelial cells and angiogenesis. Furthermore, cyclo-VEGI significantly blocks the growth of established intracranial glioma in nude and syngeneic mice and improves survival.

Angiogenesis Inhibitors↗

PubMed2004

Combinatorial administration of molecules that simultaneously inhibit angiogenesis and invasion leads to increased therapeutic efficacy in mouse models of malignant glioma.

PURPOSE: We investigated the ability of the combinatorial administration of different inhibitors with activities on glioma angiogenesis, migration, and proliferation to produce a prolonged inhibition of glioma growth. EXPERIMENTAL DESIGN: We combined inhibitors affecting solely tumor angiogenesis (PF-4/CTF, cyclo-VEGI) or inhibitors affecting both angiogenesis and invasion together (PEX, PF-4/DLR). RESULTS: When administered in combination, these drugs produced a prolonged and increased inhibition of glioma growth independently from the type of inhibitor used. The combinatory administration was more effective than the administration of a single inhibitor alone, and a strong therapeutic response was reached with a significantly lower amount of protein. The strongest inhibition was observed when human PEX and PF-4/DLR, which affect both glioma angiogenesis and invasion by separate mechanisms, were combined. CONCLUSIONS: This supports the concept that prolonged glioma growth inhibition can be achieved by simultaneous delivery of molecules that target both tumor and endothelial cells and acting by separate mechanisms.

Animals↗

PubMed2004

The tyrp1-Tag/tyrp1-FGFR1-DN bigenic mouse: a model for selective inhibition of tumor development, angiogenesis, and invasion into the neural tissue by blockade of fibroblast growth factor receptor activity.

We describe herein a new transgenic mouse tumor model in which fibroblast growth factor (FGF) receptor activity is selectively inhibited. Tyrp1-Tag mice that develop early vascularized tumors of the retinal pigment epithelium were crossed with tyrp1-FGFR1-DN mice that express dominant-negative FGF receptors in the retinal pigment epithelium to generate bigenic mice. Initial angiogenesis-independent tumor growth progressed equally in tyrp1-Tag and bigenic mice with no significant differences in the number of dividing and apoptotic cells within the tumor. By contrast, at a later stage when tyrp1-Tag tumors rapidly expanded to fill the entire eye posterior chamber and migrate along the optic nerve toward the chiasma, bigenic tumors remained small and were poorly vascularized. Secondary tumors of small size developed in only 20% of bigenic mice by 1 month. Immunohistochemical analysis of secondary tumors from bigenic mice showed a reduction of angiogenesis and an increase in apoptosis in tumor cells. Tumor cells from bigenic mice expressed high levels of truncated FGF receptors and did not induce endothelial tube formation in vitro. All in all, this indicates that the tyrp1-Tag mouse may be a useful model to study selective tumor inhibition and the effect of antitumor therapy that targets a specific growth factor pathway. FGF receptors are required at the onset of tumor invasion and angiogenesis in ocular tumors and are good therapeutic targets in this model. The bigenic mouse may also constitute a useful model to answer more fundamental questions of cancer biology such as the mechanism of tumor escape.

Animals↗

PubMed2004

VEGF coordinates interaction of pericytes and endothelial cells during vasculogenesis and experimental angiogenesis.

Biological activities of vascular endothelial growth factor (VEGF) have been studied extensively in endothelial cells (ECs), but few data are available regarding its effects on pericytes. In murine embryoid body cultures, VEGF-induced expression of desmin and alpha-smooth muscle actin (alpha-SMA) in CD-31+ cells. The number of CD-31+/desmin+ vascular chords increased with VEGF treatment time and peaked during a differentiation window between 6 and 9 days after plating. In vivo, VEGF-induced elongation and migration of desmin-positive pericytes and coverage of angiogenic capillaries, as revealed by analysis of Sambucus nigra lectin-stained vascular beds of the chick chorioallantoic membrane. VEGF also caused significant decrease of intercapillary spaces, an indicator for intussusceptive vascular growth. These VEGF-mediated effects point at a more intricate interaction between ECs and pericytes cells than previously demonstrated and suggest that pericytes may be derived from EC progenitors in vitro and not only stabilize capillaries but also participate in vascular remodeling in vivo.

Animals↗

PubMed2004

Angiogenesis and invasion in gliomas.

Angiogenesis and tumor cell invasion are pathophysiological processes playing a pivotal role in glioma development and growth since the earliest phase. Angiogenesis and tumor invasion both can be considered as an invasive process in which cells are activated, and move away from their initial location, by modyfing the adhesiveness with the extracellular matrix, expressing new adhesion molecules, and degrading the extracellular matrix components by the active secretion of proteases. This process requires a complex cross-talking between endothelial and tumor cells, extracellular matrix components, and cellular elements of the host microenviroment. Both processes are under the tight regulation of a balance between stimulating and inhibiting factors. The existence of common mechanisms of regulation and the presence of naturally occurring factors that inihibit angiogenesis and invasion, makes the inhibition of both processes possible. Tumor cells may develop adapting mechanims that can allow the tumor to partially escape to the treatment, particularly when only one mechanism or one process is inhibited. The ideal treatment should simultaneously affect both angiogenesis and invasion, by the isolation or development of novel therapeutics capable of influencing both processes. As their efficacy seems also be dependent on the mode of delivery, additional studies are also needed to improve these modalities, in order to ultimately improve the extent and the duration of the therapeutic response. The most widely used in vitro and in vivo models to study angiogenesis and invasion are also discussed.

Animals↗

PubMed2004

Inhibition of FGF receptor activity in glioma implanted into the mouse brain using the tetracyclin-regulated expression system.

We have investigated growth and vascularization of malignant glioma in mice upon conditional inhibition of fibroblast growth factor (FGF) receptor activity. C6 rat glioma cells were transfected with a dominant-negative fibroblast growth factor receptor-2 (FGFR2-DN) cDNA under the control of a tetracycline-regulated expression promoter (tet off) and implanted in the brain of immunodeficient mice. Magnetic resonance imaging analysis showed a significant decrease in tumor growth 14 days after implantation when FGFR2-DN was expressed compared to control. This size difference disappeared after 20 days. However, after 20 days, tumor and endothelial cells apoptosis were higher in the FGFR2-DN group and consequently angiogenesis was decreased whereas tumor cells were similarly associated with blood vessels at the tumor periphery. Pericyte coverage was not different between the two groups but a higher amount of pericytes not associated with vessels was found in the FGFR2-DN expressing group. This demonstrates, that conditional expression of inhibitor of FGF receptor activity in gliomas implanted in the brain of immunodeficient mice can be achieved efficiently, and that FGFs are major players in glioma development and in glioma angiogenesis.

Animals↗

PubMed2004

The control of angiogenesis and tumor invasion by platelet factor-4 and platelet factor-4-derived molecules.

Platelet factor-4 (PF-4) is an ELR-negative chemokine that exhibits antiangiogenesis properties. PF-4 inhibits endothelial cell proliferation and migration, angiogenesis in vitro and in vivo, and tumor growth. However, tumor cells are not directly inhibited by PF-4. To date, a cell surface receptor that would explain the biological effects mediated by PF-4 has not been identified. PF-4 is able to interact directly with angiogenesis growth factors such as fibroblast growth factors (FGFs) and vascular endothelial growth factors and inhibits their interaction with cell surface receptors. Furthermore, dimerization of fibroblast growth factors is abrogated by PF-4. Whether PF-4 plays a role as an endogenous angiogenesis regulator is at present not clear. Several PF-4 fragments and modified molecules have been made that exhibit antiangiogenesis properties. Among these is a C-terminal fragment that has a defined structure, retains all the antiangiogenesis properties of the parent molecule, inhibits growth factor receptor binding, associates with FGFs, and destabilizes their three-dimensional structure. The relevance of these observations for the treatment of malignant disease is discussed.

Humans↗

PubMed2004

Platelet factor 4: an inhibitor of angiogenesis.

Platelet factor 4 (PF4) is an antiangiogenic ELR-negative chemokine. PF4 inhibits endothelial cell proliferation and migration and angiogenesis in vitro and in vivo. Three different mechanisms have been proposed to explain PF4's antiangiogenic effects. First, PF4 may bind proteoglycans and interfere with the proteoglycan-bystander effect on growth factor activity. Second, PF4 is able to interact directly with angiogenesis growth factors such as fibroblast growth factors or vascular endothelial growth factors and inhibits their interaction with cell surface receptors. Third, PF4 may activate cell surface receptors on endothelial cells and induce inhibitory signals. Recently, one such receptor, CXCR3-B, was identified. In cardiovascular disease, PF4 may possibly intervene in collateral vessel formation, plaque neovascularization, heparin-induced thrombocytopenia and stent endothelialization. Several PF4 fragments such as PF4-CTF and modified molecules have been made that exhibit antiangiogenesis properties and may serve as leads for further therapeutic development.

Angiogenesis Inhibitors↗

PubMed2003

Human endothelial cells derived from circulating progenitors display specific functional properties compared with mature vessel wall endothelial cells.

Endothelial progenitor cells (EPCs) were shown to be present in systemic circulation and cord blood. We investigated whether EPCs display specific properties compared with mature endothelial cells. Human cord blood CD34+ cells were isolated and adherent cells were amplified under endothelial conditions. Expression of specific markers identified them as endothelial cells, also called endothelial progenitor-derived cells (EPDCs). When compared to mature endothelial cells, human umbilical vein endothelial cells (HUVECs) and human bone marrow endothelial cells (HBMECs), endothelial markers, were expressed to the same extent except for KDR, which is expressed more in EPDCs. They display a higher proliferation potential. Functional studies demonstrated that EPDCs were more sensitive to angiogenic factors, which afford these cells greater protection against cell death compared with HUVECs. Moreover, EPDCs exhibit more hematopoietic supportive activity than HUVECs. Finally, studies in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice demonstrated that human circulating EPCs are able to colonize a Matrigel plug. EPDCs display the morphology and phenotype of endothelial cells. Their functional features indicate, however, that although these cells have undergone some differentiation steps, they still have the properties of immature cells, suggesting greater tissue repair capabilities. Future use of in vitro amplified peripheral blood EPDCs may constitute a challenging strategy for cell therapy.

Animals↗