ABSTRACT
The development of drugs that target the tumor neovasculature may hold promise in inhibiting tumor growth. Experiments in vivo with castanospermine, an inhibitor of the glucosidases that convert protein N-linked high mannose carbohydrates to complex oligosaccharides, resulted in significant inhibition of tumor growth in nude mice. Angiogenesis to basic fibroblast growth factor in castanospermine-treated C57/BL mice was similarly reduced. Endothelial cell proliferation, invasion of basement membrane, and differentiation are crucial steps during neovascularization. In vitro differentiation models using Matrigel and postconfluent cultures of endothelial cells were used to study the effects of glycosidase inhibitors on endothelial cell behavior. FACS analysis of cell surface oligosaccharides using either Concanavalin A or L-phytohemagglutinin lectins confirmed an increase in high mannose groups and a decrease in tri- and tetra antennary beta-linked galactose-N-acetylglucosamine on mannose residues of Asn-linked oligosaccharides upon drug treatment. Castanospermine and the glucosidase inhibitor N-methyldeoxynojirimycin prevented the morphological differentiation of endothelial cells in vitro. These compounds did not alter the proliferation of cultured endothelial cells or their ability to attach to various extracellular matrix molecules. However, the cells showed a reduced ability to migrate and to invade basement membrane gels in vitro and an increased tendency to form aggregates that was inhibitable by D-mannose. These studies suggest that certain cell surface oligosaccharides are required for angiogenesis and that glucosidase inhibitors that alter these structures on endothelial cells are able to inhibit tumor growth.
Subject(s)
Endothelium/metabolism , Glycoconjugates/metabolism , Glycoside Hydrolase Inhibitors , Glycosylation/drug effects , Indolizines/pharmacology , Neoplasms, Experimental/pathology , Neovascularization, Pathologic , 1-Deoxynojirimycin/analogs & derivatives , Animals , Cell Adhesion/drug effects , Cell Aggregation/drug effects , Cell Differentiation/drug effects , Cell Division/drug effects , Cells, Cultured , Chemotaxis/drug effects , Glucosamine/analogs & derivatives , Glucosamine/pharmacology , Growth Inhibitors , In Vitro Techniques , Mice , Mice, Inbred C57BL , Mice, Nude , Protein Processing, Post-Translational/drug effectsABSTRACT
SC-45662 and SC-41661A, selective arachidonate 5-lipoxygenase (5-LO) inhibitors, had markedly different effects on formyl-methionyl-leucyl-phenylalanine (fMLP) and complement fragment 5a (C5a) induced superoxide release from human neutrophils (PMNs). SC-45662 inhibited superoxide generation induced by fMLP and C5a with IC50 values of 12 and 5 microM, respectively. Furthermore, SC-45662 was capable of inhibiting fMLP and C5a induced superoxide release in PMNs primed with bacterial lipopolysaccharide, tumor necrosis factor-alpha and other priming agents. SC-41661A, a compound from the same chemical series as SC-45662, did not inhibit or induce superoxide generation, but instead primed PMNs for fMLP and C5a induced superoxide generation. The induced superoxide release was concentration dependently enhanced 2 to 4-fold at 5-50 microM. Superoxide release induced by phorbol myristate acetate or serum-activated zymosan was unaffected by either SC-45662 or SC-41661A. The regulation of superoxide generation by these compounds, both of which have the identical oxidation-reduction pharmacophore, was clearly independent of their effects on 5-LO activity. Furthermore, the mechanism by which SC-45662 and SC-41661A alter superoxide generation did not appear to depend on inhibition of xanthine oxidase, catalase or superoxide dismutase. These new compounds provide effective tools for further investigation of the relationship of these two biochemical oxidative systems.
Subject(s)
Complement C5a/pharmacology , Lipoxygenase Inhibitors , N-Formylmethionine Leucyl-Phenylalanine/pharmacology , Neutrophils/drug effects , Superoxides/blood , Acetates/pharmacology , Amides/pharmacology , Animals , Humans , Lipoxygenase Inhibitors/pharmacology , Neutrophils/metabolism , Phenols/pharmacology , Pyridines/pharmacology , Rats , Tumor Cells, CulturedABSTRACT
SC-39026, (+/-) 2-chloro-4-(1-hydroxyoctadecyl)benzoic acid, inhibits human neutrophil elastase with an IC50 of 0.5 microM (KI of 1.5 microM). Its inhibition of elastase is reversible and noncompetitive at low concentrations (0.5-1.25 microM). Inhibition is "mixed" at higher inhibitor concentrations. SC-39026 is inactive against hog pancreatic elastase, bovine alpha-chymotrypsin and Pseudomonas aeruginosa elastase, but does inhibit human neutrophil cathepsin G with an IC50 of approximately 2.5 microM. Neutrophil elastases isolated from rat, hamster, rabbit and hog are also inhibited by SC-39026.
