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N Bouck

Publications and source records attributed to N Bouck.

At least 19 recordsLinked to original sources
PubMed2003

Low content of the natural ocular anti-angiogenic agent pigment epithelium-derived factor (PEDF) in aqueous humor predicts progression of diabetic retinopathy.

AIMS/HYPOTHESIS: Retinopathy is the most common microvascular complication of diabetes. Our aim was to address the predictive value of pro-angiogenic and anti-angiogenic markers for progression of retinopathy. METHODS: Aqueous humor was collected at cataract surgery from 32 diabetic patients who had no or very mild retinopathy (ETDRS stage </=20) and 33 normoglycaemic control subjects. Content of pro-angiogenic vascular endothelial growth factor and angiogenic inhibitor pigment epithelium-derived factor were determined. ANGIOGENIC activity was quantified by measuring its effect on the migration of capillary endothelial cells. The predictive value of the initial level of these markers for progression of retinopathy was studied by following the probands for a maximum of 75 months. RESULTS: In the aqueous fluid content of vascular endothelial growth factor was increased in diabetic patients (mean values 492 versus 292 pg/ml; p=0.0052), and pigment epithelium-derived factor values were decreased (mean values 1740 versus 3680 ng/ml; p=0.0058) compared to control subjects. Of the diabetic patients ten progressed during follow-up (ETDRS stage >47B). This subgroup showed lower pigment epithelium-derived factor content when compared to non-progressors and control subjects. Migratory activity in samples of patients from the control group and in diabetic patients without progression was generally inhibitory due to pigment epithelium-derived factor. Inhibition was blocked by neutralizing antibodies to pigment epithelium-derived factor. In diabetic patients initial angiogenic activity was higher in those who later developed retinopathy (vs. controls p=0.00005; vs. no progressors p=0.0003). Both pigment epithelium-derived factor and migratory response predicted progression. CONCLUSION/INTERPRETATION: Pigment epithelium-derived factor is an important negative regulator of angiogenic activity of aqueous humor. Its content in the aqueous humor of diabetic patients strongly predicts who among them will develop progression of retinopathy.

Aged↗
PubMed2003

Proliferative diabetic retinopathy is associated with a low level of the natural ocular anti-angiogenic agent pigment epithelium-derived factor (PEDF) in aqueous humor. a pilot study.

Retinopathy is the most common microvascular diabetes complication and represents a major threat to the eyesight. The aim of this study was to address the role of pro- and anti-angiogenic molecules in diabetic retinopathy in the aqueous humor of the eye. Aqueous humor was collected at cataract surgery from 19 diabetic patients and from 13 age- and sex-matched normoglycemic controls. Levels of pro-angiogenic vascular endothelial growth factor (VEGF) and angiogenic inhibitor pigment epithelium-derived factor (PEDF) were determined. Angiogenic activity of the aqueous humor was quantified by measuring its effect on the migration of capillary endothelial cells. In the aqueous fluid, VEGF levels were increased in diabetics (mean values: 501 vs. 367 pg/ml; p = 0.05), compared to controls. PEDF was found to be decreased in diabetics (mean values: 2080 vs. 5780 ng/ml; p = 0.04) compared to controls. In seven diabetic patients with proliferative retinopathy, the most profound finding was a significant decrease of the PEDF level (mean value: 237 ng/ml), whereas VEGF levels were comparable to diabetic patients without proliferation (mean value: 3153; p = 0.003). Angiogenic activity in samples of patients from the control group was generally inhibitory due to PEDF, and inhibition was blocked by neutralizing antibodies to PEDF. Likewise, in diabetics without proliferation, angiogenic activity was also blocked by antibodies to PEDF. We will demonstrate here that the level of the natural ocular anti-angiogenic agent PEDF is inversely associated with proliferative retinopathy. PEDF is an important negative regulator of angiogenic activity of aqueous humor. Our data may have implications for the development of novel regimens for diabetic retinopathy.

Aged↗
PubMed2001

c-Jun N-terminal kinase activation is required for the inhibition of neovascularization by thrombospondin-1.

Thrombospondin-1 (TSP-1) is a potent inhibitor of angiogenesis that acts directly on endothelial cells via the CD36 surface receptor molecule to halt their migration, proliferation, and morphogenesis in vitro and to block neovascularization in vivo. Here we show that inhibitory signals elicited by TSP-1 did not alter the ability of inducers of angiogenesis to activate p42 and p44 mitogen-activated protein kinase (MAPK). Rather, TSP-1 induced a rapid and transient activation of c-Jun N-terminal kinases (JNK). JNK activation by TSP-1 required engagement of CD36, as it was blocked by antagonistic CD36 antibodies and stimulated by short anti-angiogenic peptides derived from TSP-1 that act exclusively via CD36. TSP-1 inhibition of corneal neovascularization induced by bFGF was severely impaired in mice null for JNK-1, pointing to a critical role for this stress-activated kinase in the inhibition of neovascularization by TSP-1.

Angiogenesis Inhibitors↗
PubMed2001

In vivo mechanisms by which tumors producing thrombospondin 1 bypass its inhibitory effects.

Thrombospondin 1 (TSP1) is a multifunctional protein able to activate TGFbeta and to inhibit angiogenesis in vivo. Although usually thought of as an inhibitor of tumor growth, TSP1 may sometimes be present at high levels during tumor progression, suggesting that tumors can eventually overcome their anti-tumor effects. Using a tet-repressible expression system, we demonstrate that murine TSP1 delayed the onset of tumor growth when produced in the tumor bed by rat fibrosarcoma tumor cells or by stromal fibroblasts coinjected with unmodified C6 glioma tumor cells. Yet upon prolonged exposure to TSP1, tumors came to grow at the same rate in the presence as in the absence of TSP1 and transplantation experiments showed that they had become insensitive to inhibition by TSP1 in both syngeneic and immune compromised hosts. Tumor resistance to TSP1 developed as a result of the in vivo outgrowth of pre-existing tumor cell variants that (1) secreted increased amounts of angiogenic factors that counterbalanced the inhibitory effect of TSP1 on neovascularization and (2) grew more efficiently in the presence of TSP1-activated TGFbeta. These results indicate that prolonged and continuous local delivery of a single multifunctional angiogenesis inhibitor like TSP1 to fast-growing tumors can lead to tumor resistance in vivo by fostering the outgrowth of subpopulations that are a by-product of the genetic instability of the tumor cells themselves.

Angiogenesis Inhibitors↗
PubMed2001

Prevention of ischemia-induced retinopathy by the natural ocular antiangiogenic agent pigment epithelium-derived factor.

Aberrant blood vessel growth in the retina that underlies the pathology of proliferative diabetic retinopathy and retinopathy of prematurity is the result of the ischemia-driven disruption of the normally antiangiogenic environment of the retina. In this study, we show that a potent inhibitor of angiogenesis found naturally in the normal eye, pigment epithelium-derived growth factor (PEDF), inhibits such aberrant blood vessel growth in a murine model of ischemia-induced retinopathy. Inhibition was proportional to dose and systemic delivery of recombinant protein at daily doses as low as 2.2 mg/kg could prevent aberrant endothelial cells from crossing the inner limiting membrane. PEDF appeared to inhibit angiogenesis by causing apoptosis of activated endothelial cells, because it induced apoptosis in cultured endothelial cells and an 8-fold increase in apoptotic endothelial cells could be detected in situ when the ischemic retinas of PEDF-treated animals were compared with vehicle-treated controls. The ability of low doses of PEDF to curtail aberrant growth of ocular endothelial cells without overt harm to retinal morphology suggests that this natural protein may be beneficial in the treatment of a variety of retinal vasculopathies.

Angiogenesis Inhibitors↗
PubMed2001

Thrombospondin-1 gene expression affects survival and tumor spectrum of p53-deficient mice.

In vitro and in vivo data indicate that thrombospondin-1 (TSP1) inhibits tumor progression in several ways including direct effects on cellular growth and apoptosis in the stromal compartment. To evaluate the importance of TSP1 for the progression of naturally arising tumors in vivo, we have crossed TSP1-deficient mice with p53-deficient mice. In p53-null mice, the absence of TSP1 decreases survival from 160 +/- 52 days to 149 +/- 42 days. A log-rank test comparing survival curves for these two populations yields a two-sided P value of 0.0272. For mice that are heterozygous for the p53-null allele, survival is 500 +/- 103 days in the presence of TSP1 expression, and 426 +/- 125 days in its absence (P = 0.0058). Whereas TSP1 expression did not cause a measurable change in the incidence of the majority of tumor types, a statistically significant (P < or = 0.05) decrease in the incidence of osteosarcomas is observed in the absence of TSP1. To determine more directly if host TSP1 inhibits tumor growth, B16F10 melanoma and F9 testicular teratocarcinoma cells have been implanted in C57BL/6J and 129Sv TSP1-null mice, respectively. The B16F10 tumors grow approximately twice as fast in the TSP1-null background and exhibit an increase in vascular density, a decrease in the rate of tumor cell apoptosis, and an increase in the rate of tumor cell proliferation. Increased tumor growth is also observed in the absence of TSP1 on the 129Sv genetic background. These data indicate that endogenous host TSP1 functions as a modifier or landscaper gene to suppress tumor growth.

Animals↗
PubMed2001

Pigment epithelium-derived factor (PEDF) in neuroblastoma: a multifunctional mediator of Schwann cell antitumor activity.

Neuroblastoma is notable for its cellular heterogeneity and unpredictable outcome. Tumors are a variable mixture of primitive malignant neuroblasts, more differentiated ganglionic cells, Schwann and endothelial cells. Although often fatal, neuroblastomas can spontaneously regress, possibly due to favorable autocrine and paracrine interactions among these cells. Here, pigment epithelium-derived factor (PEDF), a potent inhibitor of angiogenesis and inducer of neural differentiation, is shown to be produced by ganglionic cells and Schwann cells, but not by more primitive tumor cells. Although undifferentiated neuroblastoma tumor cell secretions were angiogenic primarily due to vascular endothelial growth factor, secretions of Schwann cells were anti-angiogenic due to PEDF. In addition, PEDF was the major factor responsible for Schwann cell's ability to induce tumor cell differentiation in vitro and recombinant PEDF had the same effect in vitro and in vivo. Both the growth and the survival of Schwann cells were enhanced by PEDF. Thus PEDF may serve as a multifunctional antitumor agent in neuroblastomas, inhibiting angiogenesis while promoting the numbers of Schwann cells and differentiated tumor cells that in turn produce PEDF, suggesting that its clinical administration could stimulate a multifaceted antitumor feedback loop with the potential to limit and possibly regress tumor growth.

Angiogenesis Inhibitors↗
PubMed2000

Signals leading to apoptosis-dependent inhibition of neovascularization by thrombospondin-1.

Thrombospondin-1 (TSP-1) is a naturally occurring inhibitor of angiogenesis that limits vessel density in normal tissues and curtails tumor growth. Here, we show that the inhibition of angiogenesis in vitro and in vivo and the induction of apoptosis by thrombospondin-1 all required the sequential activation of CD36, p59fyn, caspase-3 like proteases and p38 mitogen-activated protein kinases. We also detected increased endothelial cell apoptosis in situ at the margins of tumors in mice treated with thrombospondin-1. These results indicate that thrombospondin-1, and possibly other broad-spectrum natural inhibitors of angiogenesis, act in vivo by inducing receptor-mediated apoptosis in activated microvascular endothelial cells.

Angiostatins↗
PubMed2000

Maspin is an angiogenesis inhibitor.

Maspin, a unique member of the serpin family, is a secreted protein encoded by a class II tumor suppressor gene whose downregulation is associated with the development of breast and prostate cancers. Overexpression of maspin in breast tumor cells limits their growth and metastases in vivo. In this report we demonstrate that maspin is an effective inhibitor of angiogenesis. In vitro, it acted directly on cultured endothelial cells to stop their migration towards basic fibroblast growth factor and vascular endothelial growth factor and to limit mitogenesis and tube formation. In vivo, it blocked neovascularization in the rat cornea pocket model. Maspin derivatives mutated in the serpin reactive site lost their ability to inhibit the migration of fibroblasts, keratinocytes, and breast cancer cells but were still able to block angiogenesis in vitro and in vivo. When maspin was delivered locally to human prostate tumor cells in a xenograft mouse model, it blocked tumor growth and dramatically reduced the density of tumor-associated microvessels. These data suggest that the tumor suppressor activity of maspin may depend in large part on its ability to inhibit angiogenesis and raise the possibility that maspin and similar serpins may be excellent leads for the development of drugs that modulate angiogenesis.

Angiogenesis Inhibitors↗
PubMed2000

A pilot trial of suramin in metastatic breast cancer to assess antiangiogenic activity in individual patients.

Suramin is a polysulfonated naphthylurea with multiple potential mechanisms of action against tumors, including the ability to bind growth factors known to promote tumor angiogenesis. Using an established fixed dosing scheme for the administration of suramin in patients, a pilot study was conducted in patients with progressive, metastatic breast cancer. The primary objective of this trial is to define the effect of suramin on the angiogenic activity in individual patients using in vitro laboratory assays. The secondary objective was to assess the antitumor effect of suramin in a population of metastatic breast cancer patients. No objective tumor responses were observed in any of the 9 patients who received treatment with suramin, however 1 patient did maintain stable disease status. The strength of angiogenic activity present in patient samples was assessed by testing patient plasma in the capillary endothelial cell migration assay. Angiogenic activity followed over time was lowest in patients with the highest suramin concentrations and highest in patients with the lowest suramin concentrations. We conclude that it is feasible to continually monitor the activity of antiangiogenic agents in individual patients without relying on clinical tumor response.

Adenocarcinoma↗
PubMed1998

Multiple forms of angiostatin induce apoptosis in endothelial cells.

Angiostatin is a circulating inhibitor of angiogenesis generated by proteolytic cleavage of plasminogen. In this study we have used recombinant human and murine angiostatins (kringles 1-4) as well as native human angiostatin (prepared by elastase digestion of plasminogen [kringles 1-3] or by plasmin autocatalysis in the presence of a free sulfhydryl donor [kringles 1-4]). We report that angiostatin reduces endothelial cell number in a 4-day proliferation assay without affecting cell cycle progression into S-phase (as determined by bromodeoxyuridine labeling). This suggested that the reduction in cell number in the proliferation assay might in part be due to cytotoxicity. This was confirmed by the observation that ethidium homodimer incorporation (a measure of plasma membrane integrity) into endothelial cells was increased by angiostatin in a manner similar to that seen with tumor necrosis factor- (TNF-) and transforming growth factor-beta1 (TGF-beta1), both of which induce apoptosis in endothelial cells. In contrast to TNF- and TGF-beta1, angiostatin did not induce cytotoxicity in human MRC-5 fibroblast, rat smooth muscle, canine MDCK epithelial, or murine B16-F10 melanoma cell lines. Angiostatin-induced apoptosis was confirmed by endothelial cell nuclear acridine orange incorporation as well as by annexin V and TUNEL staining. These in vitro findings point to endothelial cell apoptosis as a mechanism for the antiangiogenic effect of angiostatin in vivo.

Angiostatins↗
PubMed1998

Thrombospondin-1 is a major activator of TGF-beta1 in vivo.

The activity of TGF-beta1 is regulated primarily extracellularly where the secreted latent form must be modified to expose the active molecule. Here we show that thrombospondin-1 is responsible for a significant proportion of the activation of TGF-beta1 in vivo. Histological abnormalities in young TGF-beta1 null and thrombospondin-1 null mice were strikingly similar in nine organ systems. Lung and pancreas pathologies similar to those observed in TGF-beta1 null animals could be induced in wild-type pups by systemic treatment with a peptide that blocked the activation of TGF-beta1 by thrombospondin-1. Although these organs produced little active TGF-beta1 in thrombospondin null mice, when pups were treated with a peptide derived from thrombospondin-1 that could activate TGF-beta1, active cytokine was detected in situ, and the lung and pancreatic abnormalities reverted toward wild type.

Animals↗
PubMed1998

The anticancer drug edelfosine is a potent inhibitor of neovascularization in vivo.

Edelfosine is an alkyl-lysophospholipid that acts as an anticancer agent in vivo. To test the hypothesis that part of its antineoplastic activity may be due to its ability to inhibit the neovascularization on which the progressive growth of all tumors depends, we evaluated edelfosine in vitro and in vivo for antiangiogenic activity. Edelfosine acted directly on cultured capillary endothelial cells, inhibiting their migration toward the angiogenic factor, basic fibroblastic growth factor (bFGF), at doses of 8-200 nM. When given systemically to rats (20 mg/kg i.p. twice daily), edelfosine was well tolerated and antiangiogenic. The majority of treated animals became unable to mount a corneal neovascular response to a pellet releasing bFGF, whereas vigorous vessel ingrowth was seen in untreated controls.

Animals↗
PubMed1997

The mechanism of cancer-mediated conversion of plasminogen to the angiogenesis inhibitor angiostatin.

Angiostatin, a potent naturally occurring inhibitor of angiogenesis and growth of tumor metastases, is generated by cancer-mediated proteolysis of plasminogen. Human prostate carcinoma cells (PC-3) release enzymatic activity that converts plasminogen to angiostatin. We have now identified two components released by PC-3 cells, urokinase (uPA) and free sulfhydryl donors (FSDs), that are sufficient for angiostatin generation. Furthermore, in a defined cell-free system, plasminogen activators [uPA, tissue-type plasminogen activator (tPA), or streptokinase], in combination with one of a series of FSDs (N-acetyl-L-cysteine, D-penicillamine, captopril, L-cysteine, or reduced glutathione] generate angiostatin from plasminogen. An essential role of plasmin catalytic activity for angiostatin generation was identified by using recombinant mutant plasminogens as substrates. The wild-type recombinant plasminogen was converted to angiostatin in the setting of uPA/FSD; however, a plasminogen activation site mutant and a catalytically inactive mutant failed to generate angiostatin. Cell-free derived angiostatin inhibited angiogenesis in vitro and in vivo and suppressed the growth of Lewis lung carcinoma metastases. These findings define a direct mechanism for cancer-cell-mediated angiostatin generation and permit large-scale production of bioactive angiostatin for investigation and potential therapeutic application.

Angiostatins↗
PubMed1997

Sequential development of an angiogenic phenotype by human fibroblasts progressing to tumorigenicity.

As normal cells progress to malignancy they must acquire an angiogenic phenotype that will enable them to attract the blood vessels necessary to support their progressive growth. Here we define the mechanism by which human fibroblasts cultured from Li Fraumeni patients and progressing to tumorigenicity in vitro become angiogenic. Initially cells were anti-angiogenic due to the secretion of high levels of inhibitory thrombospondin that overrode the modest amounts of the major inducer, vascular endothelial cell growth factor (VEGF), that were also produced. Cells became fully angiogenic in two steps, the first dependent on the loss of both alleles of wild-type p53 which caused a drop of at least 20-fold in secreted thrombospondin and a fourfold increase in secreted VEGF. Angiogenic activity increased again upon transformation by activated ras due to a further twofold increase in VEGF. Changes in relative levels of VEGF mRNA were sufficient to account for changes in secreted protein levels and in overall angiogenic activity. These studies demonstrate that an angiogenic phenotype able to support tumorigenicity can arise in a step-wise fashion in response to both oncogene activation and tumor suppressor gene loss and involve both a decrease in the secretion of inhibitors and the sequential ratcheting up of the secretion of inducers of angiogenesis.

Adult↗
PubMed1997

Lumen formation and other angiogenic activities of cultured capillary endothelial cells are inhibited by thrombospondin-1.

The large secreted glycoprotein thrombospondin-1 is a potent inhibitor of neovascularization in vivo. In order to better understand its mechanism of action, we have determined the full range of deficits thrombospondin can impose on cultured capillary endothelial cells. Exogenously added thrombospondin-1 blocked the ability of these cells to organize into cords. It blocked the migration of endothelial cells and vascular smooth muscle cells, but not that of fibroblasts, neutrophils, or keratinocytes, demonstrating specificity. Conversely, when the endogenous thrombospondin-1 produced by the endothelial cells was inactivated using antibodies that can neutralize its inhibition of neovascularization in vivo, migration toward basic fibroblast growth factor and cord formation were stimulated, and sparsely plated cells developed cylindrical cavities. These cavities formed by vesicle fusion, extended the depth of the cell, and appeared to be incipient lumens, staining positively for the luminal marker angiotensin converting enzyme. Antiangiogenic levels of thrombospondin-1 had no measurable effect on the overall level of activity of soluble gelatinases or on urokinase plasminogen activator produced by activated endothelial cells. Coupled with previously published data, these results demonstrate thrombospondin-1 is a multifaceted inhibitor able to block the entire program of dedifferentiation and redifferentiation essential to the formation of new vessels. They also support the contention that the endogenously produced protein contributes to the quiescence of the normal vasculature.

Animals↗
PubMed1996

Human prostate carcinoma cells express enzymatic activity that converts human plasminogen to the angiogenesis inhibitor, angiostatin.

Angiostatin is an inhibitor of angiogenesis and metastatic growth that is found in tumor-bearing animals and can be generated in vitro by the proteolytic cleavage of plasminogen. The mechanism by which angiostatin is produced in vivo has not been defined. We now demonstrate that human prostate carcinoma cell lines (PC-3, DU-145, and LN-CaP) express enzymatic activity that can generate bioactive angiostatin from purified human plasminogen or plasmin. Affinity purified PC-3-derived angiostatin inhibited human endothelial cell proliferation, basic fibroblast growth factor-induced migration, endothelial cell tube formation, and basic fibroblast growth factor-induced corneal angiogenesis. Studies with proteinase inhibitors demonstrated that a serine proteinase is necessary for angiostatin generation. These data indicate that bioactive angiostatin can be generated directly by human prostate cancer cells and that serine proteinase activity is necessary for angiostatin generation.

Angiostatins↗