SURAMIN INHIBITS C6 GLIOMA-INDUCED ANGIOGENESIS IN-VITRO

Aspects of tumor-induced angiogenesis in vitro were examined using an assay involving collagen gel invasion by a surface monolayer of bovine endothelial cells under the influence of serum free conditioned mediu m produced by C6 cells, an experimentally derived rat glial tumor cell line. The effects of the polyanionic compound suramin, known to inter fere with growth factor/cell signaling on this process were evaluated. Collagen gel invasion was quantified by adding C6 conditioned medium with or without various doses of suramin to monolayers of bovine aorti c endothelial cells grown on type I collagen gels in transwell inserts . Cultures were monitored with phase-contrast microscopy. After variou s periods of incubation collagen gels were fixed, embedded in epoxy re sin, and 1-mu m thick sections were stained with toluidine blue. Addit ional cultures were used to evaluate the effects of C6 conditioned med ium and suramin on endothelial cell proliferation, and on chemotaxis t hrough 8-mu m pores. C6 glioma cell conditioned medium induced large v essel endothelial cells to sprout into the underlying collagen matrix and subsequently form networks of capillary like tubes. Conditioned me dium was also chemotactic and mitogenic for these cells. The addition of suramin to C6 glioma conditioned medium prevents tube formation in collagen gels, and inhibits both endothelial cell proliferation and ch emotaxis in a dose dependent manner. These results suggest that glial tumor cell conditioned medium induces angiogenesis in large vessel end othelial cells in vitro via mechanisms which are disrupted by suramin, most likely involving tumor-derived growth factor release and/or endo thelium-mediated matrix proteolysis. (C) 1995 Wiley-Liss, Inc.