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Emile E Voest

Publications and source records attributed to Emile E Voest.

At least 37 records · Page 2Linked to original sources
PubMed2004

Do antiangiogenic protein fragments have amyloid properties?

Tumor growth requires proteolytic activity. As a consequence, protein breakdown products are present in the circulation of patients with cancer. Within the past decade a large number of proteolytic fragments have been identified that inhibit angiogenesis and tumor growth. The mechanism of action of these inhibitors is still poorly understood. We recently found that the effects of the angiogenesis inhibitor endostatin on endothelial cells is critically dependent on the presence of cross-beta structure, a structure also present in amyloidogenic polypeptides in plaques of patients with amyloidosis, such as Alzheimer disease. We also showed that cross-beta structure containing endostatin is a ligand for tissue-type plasminogen activator (tPA). We noted that many angiogenesis inhibitors stimulate tPA-mediated plasminogen activation. Because the presence of cross-beta structure is the common denominator in tPA-binding ligands, we hypothesize that these endogenous antiangiogenic proteolytic fragments share features with amyloidogenic polypeptides. We postulate that the cross-beta structural fold is present in these antiangiogenic polypeptide fragments and that this structure mediates the inhibitory effects. The hypothesis provides new insights in the potential mechanisms of these angiogenesis inhibitors and offers opportunities to improve their use.

Amyloid↗
PubMed2004

Fibrin-incorporated vitronectin is involved in platelet adhesion and thrombus formation through homotypic interactions with platelet-associated vitronectin.

When a blood clot is formed, vitronectin (VN) is incorporated. Here we studied the consequence of VN incorporation for platelet interactions under flow. Perfusion of whole blood over a fibrin network, formed from purified fibrinogen, resulted in approximately 20% surface coverage with blood platelets. Incorporation of purified multimeric VN into the fibrin network resulted in a 2-fold increase in surface coverage with platelets and in enhancement of platelet aggregate formation. A human monoclonal antibody (huMab VN18), directed against the multimeric form of VN, inhibited platelet adhesion to the combined fibrin/VN matrix to the level of adhesion on fibrin alone. This inhibition was also shown when whole blood was perfused over a plasma-derived clot. Surprisingly, the inhibitory action of the antibody was not directed toward VN incorporated into the fibrin network but toward VN released from the platelets. We conclude that VN-potentiated platelet-clot interaction requires VN in the clot and multimeric VN bound to the platelet surface. Our results provide evidence that homotypic VN interactions contribute to platelet adhesion and aggregation to a blood clot. This report demonstrates for the first time that self-assembly of VN may provide a physiologically relevant contribution to platelet aggregation on a blood clot.

Antibodies, Monoclonal↗
PubMed2004

Stimulation of angiogenesis by Ras proteins.

Cells that have acquired a proliferative advantage form islets of hyperplasia during the initial stages of tumor development. Like normal cells, they require oxygen and nutrients to survive and proliferate. The centre of the islets is characterized by low oxygen pressure and low pH, conditions that stimulate the sprouting of new capillaries from nearby vascular beds. It is now well established that neovascularisation (angiogenesis) of the hyperplasias is essential for further development of the tumor. The family of ras oncogenes promotes the initiation of tumor growth by stimulating tumor cell proliferation, but also ensures tumor progression by stimulating tumor-associated angiogenesis. Oncogenic Ras proteins stimulate a number of effector pathways that culminate in the transcriptional activation of genes that control angiogenesis. Moreover, Ras signaling leads to stabilization of the produced mRNAs and, possibly, to enhanced initiation of their translation. In this review we describe the mechanisms that underlie Ras regulation of vascular endothelial growth factor (VEGF), cyclooxygenases (COX-1/-2), thrombospondins (TSP-1/-2), urokinase plasminogen activator (uPA) and matrix metalloproteases-2 and -9 (MMP-2/-9). As a result of these Ras-regulated changes in gene expression, the tumor cells cause stimulation of endothelial cells in nearby vascular beds (directly via VEGF, and indirectly via COX-produced prostaglandins) and promote remodeling of the extracellular matrix (by lowering TSP and increasing uPA/MMPs). The latter effect makes growth factors available for endothelial cell activation and migration. In addition, tumor cell-activated stromal cells also contribute to the stimulation of angiogenesis by further enhancing the production and secretion of pro-angiogenic factors into the tumor stroma.

Animals↗
PubMed2004

Angiostatin inhibits experimental liver fibrosis in mice.

BACKGROUND AND AIMS: Liver fibrosis is a response to chronic hepatic damage, which ultimately leads to liver failure and necessitates liver transplantation. A characteristic of fibrosis is pathological vessel growth. This type of angiogenesis may contribute to the disturbance of hepatocyte perfusion dynamics and lead to aggravation of disease. We hypothesized that angiostatin can inhibit pathological vessel growth and, consequently, the development of hepatic fibrosis. METHODS: Hepatic fibrosis was induced by injection of carbon tetrachloride for 5 weeks. Angiostatin mice received carbon tetrachloride for 5 weeks and angiostatin during weeks 4 and 5. After 5 weeks, immunohistochemistry for endothelial cell marker von Willebrand factor and for cell proliferation was performed. Angiogenesis was quantified by counting the number of immunopositive microvessels. Also, the relative fibrotic surface was determined using Sirius Red histostaining and computer image analysis. RESULTS: Immunohistochemistry revealed increased expression for von Willebrand factor in fibrotic livers. Immunopositive microvessels were localized in fibrotic areas surrounding larger vessels and in emerging fibrotic septa. Angiostatin reduced the number of immunopositive microvessels by 69% (p<0.001). In addition, angiostatin reduced the relative fibrotic area in the liver by 63+/-0.1% (p<0.001). Finally, angiostatin treatment was not associated with differences in cell proliferation. CONCLUSIONS: Angiostatin inhibits the development of pathological angiogenesis and liver fibrosis in mice. These results warrant further evaluation of angiostatin as an antifibrotic agent, potentially contributing to the deferment of liver transplantation and reduced recurrence of fibrotic disease in the transplanted liver.

Angiogenesis Inhibitors↗
PubMed2004

Fibronectin is a hypoxia-independent target of the tumor suppressor VHL.

The von Hippel-Lindau (VHL) tumor suppressor gene regulates the extracellular matrix by controlling fibronectin deposition. To identify novel VHL target genes, we subjected mRNA from VHL-deficient RCC cells (786-0-pRC) and a transfectant re-expressing wildtype VHL (786-0-VHL) to differential expression profiling. Among the differentially expressed genes, we detected that fibronectin is upregulated in the presence of VHL, while it is not affected by hypoxia. Thus regulation of fibronectin deposition by VHL occurs at the transcriptional level, irrespective of oxygen levels.

Carcinoma, Renal Cell↗
PubMed2004

Response of rat prostate and lung tumors to ionizing radiation combined with the angiogenesis inhibitor AMCA.

AIM: To determine whether radiation combined with Trans-4-AminoMethyl Cyclohexane carboxylic Acid (AMCA, or tranexamic acid, Cyklokapron) results in a better tumor response than radiation alone. MATERIALS AND METHODS: We evaluated the responses of the L44 lung tumor in BN rats and R3327-MATLyLu (MLL) prostate tumor in Copenhagen rats, to single and fractionated X-ray doses with and without AMCA (1.5 g/kg). Tumors were grown subcutaneously in the flank of the animal. AMCA was administered subcutaneously twice daily for at least 2 weeks. Response to treatment was evaluated according to excess growth delay and specific growth delay. RESULTS: L44 and MLL tumors treated with AMCA only experienced a non-significant growth delay. L44 tumors treated with 4 daily dose fractions of 2.5 Gy had a significant excess and specific growth delay when treated with AMCA, the enhancement ratio was 1.6-1.7. The enhancement ratio based on the calculated excess biologically effective dose of the linear-quadratic concept was 1.4-1.5. MLL tumors treated with a single dose of 20 Gy and AMCA had no significant excess growth delay. CONCLUSION: The enhancement ratio of 1.4-1.7 for the L44 tumor, but not for the MLL tumor, due to AMCA treatment, indicates that AMCA may potentiate the anti-tumor effect of ionizing radiation in distinct tumor types.

Angiogenesis Inhibitors↗
PubMed2004

MR imaging of mouse leptomeningeal metastases.

To develop new treatment strategies for patients with leptomeningeal metastases (LM), potential therapeutic agents have to be tested in murine models first. In vivo magnetic resonance imaging has an additive value in non-invasive monitoring of the effects of therapeutic agents on LM. Previously, we described a reproducible mouse model for B16F-10 melanoma LM. In this paper, we visualize leptomeningeal melanoma metastases in mice on both T2 weighted MR images and gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) enhanced T1 weighted MR images, using a 4.7T MR spectrometer. We conclude that both MR sequences can be used to detect and monitor LM of melanoma cells in mice. Our data further suggest that LM are more clearly visualized using T1 weighted Gd-DTPA enhanced subtraction imaging than T2 weighted imaging.

Animals↗
PubMed2003

Recombinant human angiostatin by twice-daily subcutaneous injection in advanced cancer: a pharmacokinetic and long-term safety study.

PURPOSE: A clinical study was performed to evaluate the pharmacokinetics (PK) and toxicity of three dose levels of the angiogenesis inhibitor recombinant human (rh) angiostatin when administered twice daily by s.c. injection. EXPERIMENTAL DESIGN: Eligible patients had cancer not amenable to standard treatments. Three groups of 8 patients received 7.5, 15, or 30 mg/m(2)/day divided in two s.c. injections for 28 consecutive days followed by a 7-day washout period. PK assessment was done at days 1 and 28. Thereafter, in absence of toxicity or a 100% increase in tumor size, treatment was continued without interruption. RESULTS: Median age was 53 years (range, 43-75), male:female ratio 10:14, Eastern Cooperative Oncology Group performance 0-1. At the range of doses evaluated, serum PK of all 24 of the patients showed linear relation between dose and area under the curve (0- infinity) and C(max) (reached after 2 h). Thirteen of 24 patients developed erythema at injection sites (11 patients, CTC grade 1; 2 patients, CTC grade 2) without pain or itching, spontaneously resolving within 2-3 weeks of treatment. Two patients went off study after developing hemorrhage in brain metastases, and 2 patients developed deep venous thrombosis. No other relevant treatment-related toxicities were seen, even during prolonged treatment. A panel of coagulation parameters was not influenced by rhAngiostatin treatment. Long-term (>6 months) stable disease (<25% growth of measurable uni- or bidimensional tumor size) was observed in 6 of 24 patients. Five patients received rhAngiostatin treatment for >1 year (overall median time on treatment 99 days). CONCLUSIONS: Long-term twice-daily s.c. treatment with rhAngiostatin is well tolerated and feasible at the selected doses, and merits additional evaluation. Systemic exposure to rhAngiostatin is within the range of drug exposure that has biological activity in preclinical models.

Adult↗
PubMed2003

Glycation induces formation of amyloid cross-beta structure in albumin.

Amyloid fibrils are components of proteinaceous plaques that are associated with conformational diseases such as Alzheimer's disease, transmissible spongiform encephalopathies, and familial amyloidosis. Amyloid polypeptides share a specific quarternary structure element known as cross-beta structure. Commonly, fibrillar aggregates are modified by advanced glycation end products (AGE). In addition, AGE formation itself induces protein aggregation. Both amyloid proteins and protein-AGE adducts bind multiligand receptors, such as receptor for AGE, CD36, and scavenger receptors A and B type I, and the serine protease tissue-type plasminogen activator (tPA). Based on these observations, we hypothesized that glycation induces refolding of globular proteins, accompanied by formation of cross-beta structure. Using transmission electron microscopy, we demonstrate here that glycated albumin condensates into fibrous or amorphous aggregates. These aggregates bind to amyloid-specific dyes Congo red and thioflavin T and to tPA. In contrast to globular albumin, glycated albumin contains amino acid residues in beta-sheet conformation, as measured with circular dichroism spectropolarimetry. Moreover, it displays cross-beta structure, as determined with x-ray fiber diffraction. We conclude that glycation induces refolding of initially globular albumin into amyloid fibrils comprising cross-beta structure. This would explain how glycated ligands and amyloid ligands can bind to the same multiligand "cross-beta structure" receptors and to tPA.

Amyloid↗
PubMed2003

High-dose chemotherapy with hematopoietic stem-cell rescue for high-risk breast cancer.

BACKGROUND: The use of high-dose adjuvant chemotherapy for high-risk primary breast cancer is controversial. We studied its efficacy in patients with 4 to 9 or 10 or more tumor-positive axillary lymph nodes. METHODS: Patients younger than 56 years of age who had undergone surgery for breast cancer and who had no distant metastases were eligible if they had at least four tumor-positive axillary lymph nodes. Patients in the conventional-dose group received fluorouracil, epirubicin, and cyclophosphamide (FEC) every three weeks for five courses, followed by radiotherapy and tamoxifen. The high-dose treatment was identical, except that high-dose chemotherapy (6 g of cyclophosphamide per square meter of body-surface area, 480 mg of thiotepa per square meter, and 1600 mg of carboplatin per square meter) with autologous peripheral-blood hematopoietic progenitor-cell transplantation replaced the fifth course of FEC. RESULTS: Of the 885 patients, 442 were assigned to the high-dose group and 443 to the conventional-dose group. After a median follow-up of 57 months, the actuarial 5-year relapse-free survival rates were 59 percent in the conventional-dose group and 65 percent in the high-dose group (hazard ratio for relapse in the high-dose group, 0.83; 95 percent confidence interval, 0.66 to 1.03; P=0.09). In the group with 10 or more positive nodes, the relapse-free survival rates were 51 percent in the conventional-dose group and 61 percent in the high-dose group (P=0.05 by the log-rank test; hazard ratio for relapse, 0.71; 95 percent confidence interval, 0.50 to 1.00). CONCLUSIONS: High-dose alkylating therapy improves relapse-free survival among patients with stage II or III breast cancer and 10 or more positive axillary lymph nodes. This benefit may be confined to patients with HER-2/neu-negative tumors.

Adult↗
PubMed2003

Recombinant endostatin forms amyloid fibrils that bind and are cytotoxic to murine neuroblastoma cells in vitro.

Endostatin is a fragment of collagen XVIII that acts as an endogenous inhibitor of tumor angiogenesis and tumor growth. Anti-tumor effects have been described using both soluble and insoluble recombinant endostatin. However, differences in endostatin structure are likely to cause differences in bioactivity. In the present study we have investigated the structure and cellular effects of insoluble endostatin. We found that insoluble endostatin shows all the hallmarks of amyloid aggregates. Firstly, it binds Congo red and shows the characteristic apple-green birefringe when examined under polarized light. Secondly, electron microscopy shows that endostatin forms short unbranched fibrils. Thirdly, X-ray analysis shows the abundant presence of cross-beta sheets, the tertiary structure that underlies fibrillogenesis. None of these properties was observed when examining soluble endostatin. Soluble endostatin can be triggered to form cross-beta sheets following denaturation, indicating that endostatin is a protein fragment with an inherent propensity to form amyloid deposits. Like beta-amyloid, found in the brains of patients with Alzheimer's disease, amyloid endostatin binds to and is toxic to neuronal cells, whereas soluble endostatin has no effect on cell viability. Our results demonstrate a previously unrecognized functional difference between soluble and insoluble endostatin, only the latter acting as a cytotoxic amyloid substance.

Amino Acid Sequence↗
PubMed2003

Intravital analysis of microcirculation in the regenerating mouse liver.

BACKGROUND: Liver tissue remodeling after surgery includes development of new hepatic microvasculature. Although various endothelial growth factors have been shown to play a role in liver tissue repair, the functional consequences of rapid endothelial cell proliferation are unknown. To determine the influence of endothelial cell proliferation on vessel functionality, we have analyzed the in vivo morphology of microvasculature in the regenerating liver. MATERIALS AND METHODS: Mice were subjected to 70% partial hepatectomy (PH) and at 24, 48, 96 h, 7 and 14 days post PH underwent intravital microscopy of the exposed liver remnant. Intrahepatic microvessels were visualized with fluoresceine-labeled dextran. Recorded parameters were: functional vessel length (VL), functional vessel diameter (VD), hepatic cell plate width (PW), and functional vessel surface area (FVSA). RESULTS: VL showed a transient decrease (17-31%) after PH. PW was significantly increased in the regenerating liver. VD significantly increased on days 1 and 2 post PH. On days 4, 7, and 14, VD returned to normal. In contrast, FVSA remained within normal range until day 14 post PH. CONCLUSIONS: Despite changes in vessel length and hepatic cell plate width in the early regenerating liver, functional vessel surface area remains normal until day 14 post PH. These changes may indicate compensatory vascular growth mechanisms to ensure adequate hepatocyte perfusion during liver regeneration. Better understanding of functional variations during physiological liver regeneration may be of use in liver conditions characterized by defective regeneration, e.g., cirrhosis.

Animals↗
PubMed2003

The role of the fibrinolytic system in corneal angiogenesis.

The plasminogen activation system has been implicated in angiogenesis and angiogenesis-dependent diseases such as cancer, atherosclerosis and ocular diseases. The identification and development of inhibitors of angiogenesis offer new possibilities for the treatment of these diseases. To clarify the role of proteins involved in the regulation of fibrinolysis during corneal angiogenesis, we have studied corneal vessel formation in mice deficient for urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (tPA), plasminogen, plasminogen activator inhibitor-1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI). Our results corroborate earlier findings that angiogenesis in the mouse cornea is dependent on PAI-1 and plasminogen. The absence of tPA, uPA or TAFI did not affect the formation of new vessels in the cornea.

Animals↗
PubMed2003

Amyloid endostatin induces endothelial cell detachment by stimulation of the plasminogen activation system.

Endostatin is a fragment of collagen XVIII that acts as an inhibitor of tumor angiogenesis and tumor growth. Anti-tumor effects have been described using both soluble and insoluble recombinant endostatin. However, differences in endostatin structure are likely to cause differences in bioactivity. In the present study, we have investigated the cellular effects of insoluble endostatin. We previously found that insoluble endostatin shows all the hallmarks of amyloid aggregates and potently stimulates tissue plasminogen activator-mediated formation of the serine protease plasmin. We here show that amyloid endostatin induces plasminogen activation by endothelial cells, resulting in vitronectin degradation and plasmin-dependent endothelial cell detachment. Endostatin-mediated stimulation of plasminogen activation, vitronectin degradation, and endothelial cell detachment is inhibited by carboxypeptidase B, indicating an essential role for carboxyl-terminal lysines. Our results suggest that amyloid endostatin may inhibit angiogenesis and tumor growth by stimulating the fibrinolytic system.

Angiogenesis Inhibitors↗
PubMed2003

Receptor protein tyrosine phosphatase mu expression as a marker for endothelial cell heterogeneity; analysis of RPTPmu gene expression using LacZ knock-in mice.

The receptor-like protein tyrosine phosphatase mu (RPTPmu) belongs to the subfamily of meprin, A5, RPTPmu (MAM) domain-containing RPTPs, which are thought to play an important role in cell-cell adhesion mediated processes. The current study was designed to examine the expression pattern of RPTPmu in mice. We have generated RPTPmu-LacZ knock-in mice that express the beta-galactosidase (LacZ) reporter gene under the control of the RPTPmu promoter. LacZ expression patterns were analysed in embryos and adult mice by whole mount LacZ staining. Analysis of beta-galactosidase activity of heterozygous embryos and adult tissues revealed RPTPmu expression in endothelial cells of arteries and capillaries. In contrast, expression was virtually absent in endothelial cells of veins and in fenestrated endothelial cells in the adult liver and spleen. Moreover, RPTPmu expression was found in endothelial cells from the endocardium and the aorta in embryos, but not in adult mice. In addition to heterogeneous expression in endothelial cells, RPTPmu expression was found in cardiac muscle cells but not in skeletal muscle cells or smooth muscle cells. Expression was also found in Type II pneumonocytes in the lung alveoli and in Purkinje cells and other neurons in the brain. The specific expression of RPTPmu in arterial endothelial cells and in cardiac myocytes suggests that RPTPmu may play a role in the regulation of cardiovascular functions.

Alleles↗
PubMed2002

Tissue-type plasminogen activator is a multiligand cross-beta structure receptor.

Tissue-type plasminogen activator (tPA) regulates fibrin clot lysis by stimulating the conversion of plasminogen into the active protease plasmin. Fibrin is required for efficient tPA-mediated plasmin generation and thereby stimulates its own proteolysis. Several fibrin regions can bind to tPA, but the structural basis for this interaction is unknown. Amyloid beta (Abeta) is a peptide aggregate that is associated with neurotoxicity in brains afflicted with Alzheimer's disease. Like fibrin, it stimulates tPA-mediated plasmin formation. Intermolecular stacking of peptide backbones in beta sheet conformation underlies cross-beta structure in amyloid peptides. We show here that fibrin-derived peptides adopt cross-beta structure and form amyloid fibers. This correlates with tPA binding and stimulation of tPA-mediated plasminogen activation. Prototype amyloid peptides, including Abeta and islet amyloid polypeptide (IAPP) (associated with pancreatic beta cell toxicity in type II diabetes), have no sequence similarity to the fibrin peptides but also bind to tPA and can substitute for fibrin in plasminogen activation by tPA. Moreover, the induction of cross-beta structure in an otherwise globular protein (endostatin) endows it with tPA-activating potential. Our results classify tPA as a multiligand receptor and show that cross-beta structure is the common denominator in tPA binding ligands.

Protein Conformation↗
PubMed2002

Clinical pharmacokinetics, pharmacodynamics and metabolism of the novel matrix metalloproteinase inhibitor ABT-518.

PURPOSE: To investigate the pharmacokinetics, pharmacodynamics and metabolism of the novel matrix metalloproteinase (MMP) inhibitor ABT-518. METHODS: Plasma and urine samples were obtained from six patients included in a phase I trial in which ABT-518 was given once daily via the oral route. Samples were analyzed by LC-MS/MS, ELISA and immunocapture assay. The pharmacokinetics of the parent compound and of detectable metabolites were calculated. RESULTS: After a single dose of ABT-518 peak plasma levels were reached within 4-8 h. ABT-518 had an estimated clearance (Cl/F) of approximately 3 l/h, an estimated volume of distribution (V/F) of over 70 l and a terminal half-life (T(1/2)) of 20 h. At least six different metabolites were formed. Pharmacodynamic analysis for angiogenic growth factors (bFGF and VEGF) showed plasma and urine levels in the picogram range and for total MMP-9 and MMP-2 or MMP-9 activity showed plasma and urine levels in the nanogram range. CONCLUSIONS: The MMP inhibitor ABT-518 is extensively metabolized in humans. No significant correlations between pharmacokinetics and pharmacodynamics could be established.

Adult↗