Biomedical subjects

E Flynn

Publications and source records attributed to E Flynn.

At least 37 records · Page 2Linked to original sources

PubMed1998

Expression of angiostatin cDNA in a murine fibrosarcoma suppresses primary tumor growth and produces long-term dormancy of metastases.

Tumor growth and metastasis are angiogenesis dependent. Previously, we reported that angiostatin, a potent angiogenesis inhibitor, produced by a primary Lewis lung carcinoma suppressed its growth of lung metastases (O'Reilly, M.S., L. Holmgren, Y. Shing, C. Chen, R.A. Rosenthal, M. Moses, W.S. Lane, Y. Cao, E.H. Sage, and J. Folkman. 1994. Cell. 79:315-328). Now we show that a shift of balance of tumor angiogenesis by gene transfer of a cDNA coding for mouse angiostatin into murine T241 fibrosarcoma cells suppresses primary and metastatic tumor growth in vivo. Implantation of stable clones expressing mouse angiostatin in C57Bl6/J mice inhibits primary tumor growth by an average of 77%. After removal of primary tumors, the pulmonary micrometastases in approximately 70% of mice remain in a microscopic dormant and avascular state for the duration of the experiments, e.g., 2-5 mo. The tumor cells in the dormant micrometastases exhibit a high rate of apoptosis balanced by a high proliferation rate. Our study, to our knowledge, for the first time shows the diminished growth of lung metastases after removal of the primary tumor, suggesting that metastases are self-inhibitory by halting angiogenesis. Our data may also provide a novel approach for cancer therapy by antiangiogenic gene therapy with a specific angiogenesis inhibitor.

Angiostatins↗

PubMed1998

Tumor vascularity, proliferation, and apoptosis in human melanoma micrometastases and macrometastases.

BACKGROUND: Clinically undetectable or dormant metastases (micrometastases) probably account for disease recurrence, ie, clinically evident metastases, in patients after disease-free intervals of variable length. Recently developed animal models have shown that dormancy may potentially be explained by the fact that these micrometastases are not vascularized and have comparable rates of cellular proliferation and programmed cell death (apoptosis), enabling them to remain viable indefinitely but not to show progressive growth. OBSERVATION: We report for the first time that melanoma micrometastases from humans are similarly not vascularized (mean number of microvessels, 10.2), have significantly lower rates of tumor cell proliferation (mean, 2.4%), comparable rates of proliferation and apoptosis (means, 2.4.% and 0.2%, respectively), compared with melanoma macrometastases, which have significantly greater tumor vascularity (mean number of microvessels, 18.7), higher rates of proliferation (mean, 18%), and higher rates of proliferation relative to apoptosis (means, 18% vs 1.6%). Tumor vascularity was quantified using the lectin Ulex europaeus agglutinin I to identify the number of microvessels per unit area (microscope ocular grid with an area of 7.84 x 10(-2) mm2 at x400 magnification). Melanoma cell proliferation rate was assessed with the MIB-1 antibody (Ki-67) as the number of positive nuclei per total number of tumor nuclei counted at x400 magnification. Apoptosis was quantified using the method of terminal deoxynucleotidyl transferase-medicated deoxyuridine triphosphate-biotin nick end labeling. The number of positive nuclei were quantified per total number of tumor nuclei; usually 200 tumor nuclei were counted at x400 magnification. CONCLUSION: We report, for the first time, that human micrometastases demonstrate attributes, ie, the lack of significant tumor vascularity and low but comparable rates of proliferation and apoptosis, that may explain the dormant state.

Apoptosis↗

PubMed1998

Analysis of vascularity of human neurofibromas.

BACKGROUND: A common misperception is that the vascularity of a tumor can be determined by its gross appearance. Neurofibromas are grossly white in appearance. The degree of vascularity of neurofibromas has not been determined. OBJECTIVE: The purpose of this study was to determine the extent of neovascularization of neurofibromas. METHODS: Neurofibromas from patients with neurofibromatosis-1 or spontaneous neurofibromas were stained with antibodies against von Willebrand factor (factor VIII-related antigen) and vascular endothelial growth factor (VEGF). RESULTS: Neurofibromas, both spontaneous and congenital, exhibit a high degree of vascularity. In addition, perivascular cells in neurofibromas stain with antibodies to VEGF, an angiogenic factor. CONCLUSION: Neurofibromas, despite their gross appearance, are highly vascular. Their vascularity may be mediated, in part, through the angiogenic factor VEGF.

Endothelial Growth Factors↗

PubMed1998

Curcumin is an in vivo inhibitor of angiogenesis.

BACKGROUND: Curcumin is a small-molecular-weight compound that is isolated from the commonly used spice turmeric. In animal models, curcumin and its derivatives have been shown to inhibit the progression of chemically induced colon and skin cancers. The genetic changes in carcinogenesis in these organs involve different genes, but curcumin is effective in preventing carcinogenesis in both organs. A possible explanation for this finding is that curcumin may inhibit angiogenesis. MATERIALS AND METHODS: Curcumin was tested for its ability to inhibit the proliferation of primary endothelial cells in the presence and absence of basic fibroblast growth factor (bFGF), as well as its ability to inhibit proliferation of an immortalized endothelial cell line. Curcumin and its derivatives were subsequently tested for their ability to inhibit bFGF-induced corneal neovascularization in the mouse cornea. Finally, curcumin was tested for its ability to inhibit phorbol ester-stimulated vascular endothelial growth factor (VEGF) mRNA production. RESULTS: Curcumin effectively inhibited endothelial cell proliferation in a dose-dependent manner. Curcumin and its derivatives demonstrated significant inhibition of bFGF-mediated corneal neovascularization in the mouse. Curcumin had no effect on phorbol ester-stimulated VEGF production. CONCLUSIONS: These results indicate that curcumin has direct antiangiogenic activity in vitro and in vivo. The activity of curcumin in inhibiting carcinogenesis in diverse organs such as the skin and colon may be mediated in part through angiogenesis inhibition.

Angiogenesis Inhibitors↗

PubMed1997

Oncogenic H-ras stimulates tumor angiogenesis by two distinct pathways.

The switch from a quiescent tumor to an invasive tumor is accompanied by the acquisition of angiogenic properties. This phenotypic change likely requires a change in the balance of angiogenic stimulators and angiogenic inhibitors. The nature of the angiogenic switch is not known. Here, we show that introduction of activated H-ras into immortalized endothelial cells is capable of activating the angiogenic switch. Angiogenic switching is accompanied by up-regulation of vascular endothelial growth factor and matrix metalloproteinase (MMP) bioactivity and downregulation of tissue inhibitor of MMP. Furthermore, we show that inhibition of phosphatidylinositol-3-kinase leads to partial inhibition of tumor angiogenesis, thus demonstrating that activated H-ras activates tumor angiogenesis through two distinct pathways. Finally, we show evidence for two forms of tumor dormancy.

Androstadienes↗

PubMed1997

Endostatin: an endogenous inhibitor of angiogenesis and tumor growth.

We previously identified the angiogenesis inhibitor angiostatin. Using a similar strategy, we have identified endostatin, an angiogenesis inhibitor produced by hemangioendothelioma. Endostatin is a 20 kDa C-terminal fragment of collagen XVIII. Endostatin specifically inhibits endothelial proliferation and potently inhibits angiogenesis and tumor growth. By a novel method of sustained release, E. coli-derived endostatin was administered as a nonrefolded suspension. Primary tumors were regressed to dormant microscopic lesions. Immunohistochemistry revealed blocked angiogenesis accompanied by high proliferation balanced by apoptosis in tumor cells. There was no toxicity. Together with angiostatin data, these findings validate a strategy for identifying endogenous angiogenesis inhibitors, suggest a theme of fragments of proteins as angiogenesis inhibitors, and demonstrate dormancy therapy.

Amino Acid Sequence↗

PubMed1997

Inhibition of angiogenesis and breast cancer in mice by the microtubule inhibitors 2-methoxyestradiol and taxol.

2-Methoxyestradiol (2-ME), an endogenous estrogen metabolite which disrupts microtubule function, has been shown to inhibit proliferating cells in vitro and suppress certain murine tumors in vivo. In vitro screening has determined that breast cancer cell lines are most sensitive to inhibition by 2-ME. Additionally, 2-ME has been shown to inhibit angiogenesis in vitro. We tested whether 2-ME suppresses cytokine-induced angiogenesis in vivo and inhibits growth of a human breast carcinoma in severe combined immunodeficient mice. A model of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF)-induced corneal neovascularization in C57BL/6 mice was used to evaluate the antiangiogenic effects of 2-ME and other microtubule inhibitors such as Taxol, vincristine, and colchicine. 2-ME (150 mg/kg p.o., n = 20) inhibited bFGF and VEGF-induced neovascularization by 39% and 54%, respectively. Taxol (6 mg/kg i.p., n = 17) inhibited bFGF and VEGF-induced neovascularization by 45% and 37%, respectively. Vincristine (0.2 mg/kg i.p., n = 8) and colchicine (0.25 mg/kg i.p., n = 8) had no effect. Treatment with 2-ME (75 mg/kg p.o., n = 9) for 1 month suppressed the growth of a human breast carcinoma in mice by 60% without toxicity. Recognition of the antiangiogenic and antitumor properties of 2-ME and Taxol may be crucial in planning clinical applications to angiogenesis-dependent diseases.

2-Methoxyestradiol↗

PubMed1997

Effect of a bicycle safety program and free bicycle helmet distribution on the use of bicycle helmets by elementary school children.

OBJECTIVE: Each year in the United States, 300,000 children are treated in emergency departments for bicycle injuries; one third have head injuries. The purpose of this study was to determine the effectiveness of educational interventions and free helmet distribution in increasing the use of helmets by elementary school children. METHODS: Self-report questionnaires on the use of bicycle helmets were used for students at two elementary schools (n = 1610). Testing was done both before and after the administration of a bicycle safety program and the distribution of free helmets. Pretest and posttest answers were then compared for changes in helmet use. RESULTS: Helmet usage increased significantly after the bicycle safety program, from 38% to 46% overall (p < 0.005). Children who were given free helmets were significantly more likely to wear their helmets (61.4%) than children who already owned helmets (43.4%) (p > 0.016). Children who attended the school in which free helmets were distributed showed a significant increase in helmet use (p < 0.01), whereas those at the school that had a safety program alone did not show a significant increase (p > 0.17). DISCUSSION: The results of this study suggest that bicycle safety programs and free helmet distribution may increase the consistent use of helmets in elementary school children.

Bicycling↗

PubMed1997

Critical components of the female reproductive pathway are suppressed by the angiogenesis inhibitor AGM-1470.

Angiogenesis, the growth of new blood vessels, occurs normally in female reproductive organs. We tested the hypothesis that angiogenesis inhibition may affect fertility by studying the reproductive system in either pregnant or nonpregnant cycling mice after treatment with the angiogenesis inhibitor AGM-1470. Administration of AGM-1470 to pregnant mice resulted in complete failure of embryonic growth due to interference with decidualization, placental and yolk sac formation, and embryonic vascular development. When nonpregnant cycling female mice were chronically treated with AGM-1470, inhibition of endometrial maturation and corpora lutea was observed. These data suggest that processes in reproduction can be controlled through angiogenesis inhibition.

Animals↗

PubMed1997

Effects of thallium ion on cellular components of the skin.

Thallium salts have been employed by dermatologists to cause depilation, and dermatologic features are prominent in thallium overdose. These features include alopecia and follicular hyperkeratosis. Administration of thallium to pregnant animals results in limb deformities, similar to those seen after thalidomide embryopathy. These findings suggest that thallium may act on keratinocytes, melanocytes, and endothelial cells. We show that thallium exerts pleiotropic effects on proliferation, cell shape and motility of multiple cell types. These findings may help explain the clinical findings of thallotoxicosis.

Animals↗

PubMed1996

Interactions of 2-methoxyestradiol, an endogenous mammalian metabolite, with unpolymerized tubulin and with tubulin polymers.

2-Methoxyestradiol (2ME) is an endogenous mammalian catabolite of estradiol with antimitotic activity. Although it is a competitive inhibitor of the binding of colchicine to tubulin, it has unusual effects on glutamate-induced tubulin polymerization. Polymer that was little changed in morphology assembled at a reduced rate and was relatively cold stable. We have now examined interactions of [4-3H]-2ME with unpolymerized tubulin and polymer. The [3H]2ME binds avidly to tubulin even on ice, and it is readily displaced by other colchicine site drugs. An association rate constant on ice of 1.9 x 10(2) M-1s-1 was obtained. Scatchard analysis indicated a single class of binding site and an association equilibrium constant of 5.7 x 10(5) M-1. These values lead to a calculated dissociation rate constant of 3.3 x 10(-4) s-1. In glutamate-induced tubulin assembly, a reaction that requires GTP and leads to the formation of sheets of parallel protofilaments, increasing amounts of [3H]2ME were incorporated into polymer, reaching near-stoichiometry with tubulin at 100 microM 2ME. Equivalent binding of [3H]2ME occurred when the drug was added to preformed polymer, but binding of [3H]2ME to polymer was not readily inhibited by colchicine site drugs. Significant amounts of [3H]2ME were also incorporated into microtubule polymer formed with microtubule-associated proteins, glycerol, or 4-morpholineethanesulfonate buffer, but the stoichiometry was substantially lower than that in the sheet polymer induced by either glutamate or 1,4-piperazineethanesulfonate buffer. The structural differences between the microtubule and sheet polymers leading to these differences in apparent affinity for 2ME are unknown, but presumably interaction of the estrogen metabolite with cellular microtubules has functional significance related to the antimitotic properties of the compound.

2-Methoxyestradiol↗

PubMed1996

Intravitreous injections of vascular endothelial growth factor produce retinal ischemia and microangiopathy in an adult primate.

PURPOSE: The purpose of the study is to determine the effect of exogenous vascular endothelial growth factor (VEGF) on the primate retina and its vasculature. METHODS: Ten eyes of five animals were studied. Physiologically relevant amounts of the 165 amino acid isoform of human recombinant VEGF were injected into the vitreous of six healthy cynomolgus monkey eyes. Inactivated human recombinant VEGF or vehicle was injected into four contralateral control subject eyes. Eyes were assessed by slit-lamp biomicroscopy, tonometry, fundus color photography, fundus fluorescein angiography, light microscopy, and immunostaining with antibodies against proliferating cell nuclear antigen and factor VIII antigen. RESULTS: All six bioactive VEGF-injected eyes developed dilated, tortuous retinal vessels that leaked fluorescein. Eyes receiving multiple injections of VEGF developed progressively dilated and tortuous vessels, venous beading, edema, microaneurysms, intraretinal hemorrhages and capillary closure with ischemia. The severity of the retinopathy correlated with the number of VEGF injections. None of the four control eyes exhibited any abnormal retinal vascular changes. The endothelial cells of retinal blood vessels were proliferating cell nuclear antigen positive only in the bioactive VEGF-injected eyes. CONCLUSION: Vascular endothelial growth factor is sufficient to produce many of the vascular abnormalities common to diabetic retinopathy and other ischemic retinopathies, such as hemorrhage, edema, venous beading, capillary occlusion with ischemia, microaneurysm formation, and intraretinal vascular proliferation.

Animals↗

PubMed1996

Experimental corneal neovascularisation using sucralfate and basic fibroblast growth factor.

PURPOSE: To develop a non-inflammatory model of both acute and chronic angiogenesis in the rabbit cornea using a known directly angiogenic cytokine. METHODS: Pellets made of the slow-release polymer Hydron (polyhydroxyethylmethacrylate) and containing sucralfate and/or basic fibroblast growth factor (basic-FGF) were implanted into rabbit corneas. The neovascular response to the implantation of pellets containing basic-FGF alone, sucralfate alone or a titration of basic-FGF in the presence of a constant amount of sucralfate was measured. The role of inflammation in the neovascular response was also investigated. RESULTS: The addition of sucralfate to the pellets led to the sustained release of basic-FGF resulting in a predictable and aggressive neovascular response with a low dose of basic-FGF that by itself was unable to elicit neovascularisation. At a dose of 500 ng per pellet, approximately one-third of the surface area of the cornea was vascularised within eight days of implantation. Minimal or no vascularisation occurred with the same dose of basic-FGF without sucralfate. While this dose of basic-FGF induced corneal oedema, only minimal inflammation was observed and the response was unaffected by ionising radiation. A less aggressive though still robust neovascular response with no or only minimal oedema was observed when the dose was lowered to 50 ng of basic-FGF per pellet. Some induced vessels persisted for more than three months. CONCLUSION: This is an inexpensive in vivo model of angiogenesis with the advantages of the neovascularisation being aggressive, predictable, persistent, unassociated with an obvious inflammatory response and induced by the sustained release of an agent known to have a direct stimulatory action on endothelial cells.

Acute Disease↗

PubMed1996

A model of angiogenesis in the mouse cornea.

PURPOSE: The study of angiogenesis depends on reliable and reproducible models for the stimulation of a neovascular response. The purpose of this research was to develop such a model of angiogenesis in the mouse cornea. METHODS: Uniformly sized Hydron pellets containing either basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) and sucralfate were prepared and implanted into the stroma mouse cornea adjacent to the temporal limbus. RESULTS: Neovascularization of the corneal stroma began on day 3 and was sustained through day 8. The bFGF-induced neovascularization was consistent and dose dependent in C57B1/6, as well as in severe combined immune deficient, beige natural killer cell-deficient, and nude mouse strains. Biomicroscopic and histologic examination of bFGF- and VEGF-induced angiogenesis was notable for the absence of corneal edema or substantial inflammation. CONCLUSIONS: This noninflammatory model of corneal neovascularization is especially advantageous because it is reproducible, economical, and facilitates investigation of angiogenesis in various murine tumor models as well as in genetically defined murine strains.

Animals↗

PubMed1995

Determination of ventricular vulnerable period and ventricular fibrillation threshold by use of T-wave shocks in patients undergoing implantation of cardioverter/defibrillators.

BACKGROUND: This study was designed to characterize the ventricular vulnerable period (VVP) and ventricular fibrillation (VF) threshold by use of T-wave shocks in patients undergoing implantation of cardioverter/defibrillators. A premature condensed shock applied during the VVP can induce VF. Most studies on the VVP and VF threshold have been conducted in animals rather than in humans. METHODS AND RESULTS: Twenty-one patients undergoing implantation of Medtronic PCD Jewel 7219D cardioverter/defibrillators because of ventricular tachycardia and/or VF were enrolled. All had structural heart disease. Their ages ranged from 42 to 85 years (mean, 69 +/- 11.3 years). Seventeen (80.9%) had atherosclerotic coronary artery disease. The right ventricle (RV) was driven at a cycle length (S1) of 400 ms, and monophasic shocks (S2) of 0.6 J were delivered through an RV apex lead (cathode) and a superior vena cava lead (anode) during the T wave of each cardiac cycle. The longest and shortest S1-S2 intervals that were capable of inducing sustained VF were defined as the outer and inner limits of the VVP at an energy level of 0.6 J, respectively. To determine the VF threshold, a shock of 0.2 J was applied at the midpoint of the VVP at 0.2-J increments until sustained VF was induced. The lowest energy setting capable of inducing sustained VF was defined as the VF threshold. Of the 21 patients, the VVP at an energy level of 0.6 J averaged 53.8 +/- 26.0 ms. Characteristically, the VVP started from the ascending limb of the T wave and ended at or slightly beyond the peak of the T wave, occupying 12.2 +/- 5.8% of the QT interval. The midpoint of the VVP used for determination of the VF threshold measured 0 to 90 ms (mean, 32.9 +/- 26.0 ms) before the peak of the T wave. Of the 21 patients, 16 (76.2%) had a VF threshold at < or = 0.2 J (estimated 57 V), 3 at 0.4 J (estimated 81 V), and 2 at 0.6 J (estimated 99 V). CONCLUSIONS: The VF threshold is low (< or = 0.2 J) in the majority of patients requiring implantation of cardioverter/defibrillators. Further studies are needed to define clinical usefulness of the study technique relative to its potential role for risk stratification and for assessing antifibrillatory properties of antiarrhythmic drugs in this subset group of patients.

Adult↗

PubMed1994

2-Methoxyestradiol, an endogenous mammalian metabolite, inhibits tubulin polymerization by interacting at the colchicine site.

A metabolite of estradiol, 2-methoxyestradiol (2ME), inhibits angiogenesis in the chicken embryo chorioallantoic membrane assay. Since 2ME causes mitotic perturbations, we examined its interactions with tubulin. In our standard 1.0 M glutamate system (plus 1.0 mM MgCl2 at 37 degrees C), superstoichiometric concentrations (relative to tubulin) of 2ME inhibited the nucleation and propagation phases of tubulin assembly but did not affect the reaction extent. Although polymer formed in the presence of 2ME was more cold-stable than control polymer, morphology was little changed. Under suboptimal reaction conditions (0.8 M glutamate/no MgCl2 at 26 degrees C), substoichiometric 2ME totally inhibited polymerization. No other estrogenic compound was as effective as 2ME as an inhibitor of polymerization or of the binding of colchicine to tubulin. Inhibition of colchicine binding was competitive (Ki, 22 microM). Thus, a mammalian metabolite of estradiol binds to the colchicine site of tubulin and, depending on reaction conditions, either inhibits assembly or seems to be incorporated into a polymer with altered stability properties.

2-Methoxyestradiol↗

PubMed1994

Thalidomide is an inhibitor of angiogenesis.

Thalidomide is a potent teratogen causing dysmelia (stunted limb growth) in humans. We have demonstrated that orally administered thalidomide is an inhibitor of angiogenesis induced by basic fibroblast growth factor in a rabbit cornea micropocket assay. Experiments including the analysis of thalidomide analogs revealed that the antiangiogenic activity correlated with the teratogenicity but not with the sedative or the mild immunosuppressive properties of thalidomide. Electron microscopic examination of the corneal neovascularization of thalidomide-treated rabbits revealed specific ultrastructural changes similar to those seen in the deformed limb bud vasculature of thalidomide-treated embryos. These experiments shed light on the mechanism of thalidomide's teratogenicity and hold promise for the potential use of thalidomide as an orally administered drug for the treatment of many diverse diseases dependent on angiogenesis.

Animals↗

PubMed1994

Physical examination and arteriography in patients with penetrating zone II neck wounds.

OBJECTIVE: To review the management of patients with penetrating zone II neck wounds to discern the value of physical examination and proximity arteriography for predicting arterial injury. DESIGN: A retrospective chart review of 178 patients treated for penetrating wounds to the neck. SETTING: A level I trauma facility in Dallas, Tex. PATIENTS: All patients seen from 1987 to 1991 with platysma penetration in zone II of the neck. INTERVENTION: Physical examination, arteriography, and surgical exploration were used to identify patients with arterial injuries in the neck after penetrating trauma. MAIN OUTCOME MEASURES: To identify the presence or absence of an arterial injury. RESULTS: Negative findings on physical examination ruled out an arterial injury in 99% of all patients. Patients with any sign of arterial injury had a 26% incidence of arterial injury confirmed at operation. Of 71 arteriograms in patients without signs or symptoms of arterial injury, only one had an arterial injury requiring operative intervention. CONCLUSIONS: Findings on physical examination are good predictors of arterial injury in patients with penetrating neck wounds and can exclude injury in over 99% of patients. Arteriography is a sensitive test but has a very low yield (1.4%). These findings question whether the current practice of mandatory neck exploration or proximity arteriography is necessary for patients without signs or symptoms of injury who have penetrating wounds of the neck.

Adolescent↗