Levels of selected growth factors in viable and necrotic regions of xenografted HCT-8 human colon tumours

Xenografted tumours were produced in nude mice by injection of HCT‐8 human colon tumour cells. At average volumes of about 750 mm3, animals were injected with fast green vital dye, and 20 min later, tumours were excised and dissected into viable (stained) and necrotic portions (unstained). Viable and necrotic regions were then examined for cell yields, colony forming efficiencies, and levels of basic fibroblast growth factor (FGF‐2), transforming growth factors‐β1 and ‐α (TGF‐β1, TGF‐α), platelet derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) using enzyme‐linked immunoassay (ELISA) procedures. Levels in the viable and necrotic regions were compared to levels in unseparated tumours. The average extent of necrosis in HCT‐8 tumours of this size was 64%. The data for cell yields, colony forming efficiencies FGF‐2, VEGF, TGF‐β1 and TGF‐α indicated that values determined in the unseparated tumours could be understood on the basis of the weighted average between viable and necrotic tissue, with the higher values occurring in the viable tissue. Low levels of FGF‐2 and VEGF were found in the necrotic portions of the tumour while no measurable levels of TGF‐β1 and TGF‐α could be determined. PDGF levels were, however, equivalent in both the viable and necrotic regions indicating that necrotic tissue could be an important reservoir for this growth factor.