LEVELS OF SELECTED GROWTH-FACTORS IN VIABLE AND NECROTIC REGIONS OF XENOGRAFTED HCT-8 HUMAN COLON TUMORS

Xenografted tumours were produced in nude mice by injection of HCT-8 h uman colon tumour cells. At average volumes of about 750 mm(3), animal s were injected with fast green vital dye, and 20 min later, tumours w ere excised and dissected into viable (stained) and necrotic portions (unstained). Viable and necrotic regions were then examined for cell y ields, colony forming efficiencies, and levels of basic fibroblast gro wth factor (FGF-2), transforming growth factors-beta(1) and -alpha (TG F-beta(1), TGF-alpha), platelet derived growth factor (PDGF), and vasc ular endothelial growth factor (VEGF) using enzyme-linked immunoassay (ELISA) procedures. Levels in the viable and necrotic regions were com pared to levels in unseparated tumours. The average extent of necrosis in HCT-8 tumours of this size was 64%. The data for cell yields, colo ny forming efficiencies FGF-2, VEGF, TGF-beta(1) and TGF-alpha indicat ed that values determined in the unseparated tumours could be understo od on the basis of the weighted average between viable and necrotic ti ssue, with the higher values occurring in the viable tissue. Low level s of FGF-2 and VEGF were found in the necrotic portions of the tumour while no measurable levels of TGF-beta(1) and TGF-alpha could be deter mined. PDGF levels were, however, equivalent in both the viable and ne crotic regions indicating that necrotic tissue could be an important r eservoir for this growth factor.