Tumour angiogenesis factor (TAF) in human and animal tumours.

Extracts were made from Walker 256 carcinoma, spontaneous rat mammary adenocarcinoma, Wilms' tumour, human neuroblastoma and human haemangioma. Chromatography of the extracts on Sephadex G-100 yielded four fractions, A, B, C and D. Injection of fractions B and C resulted in the growth of new capillaries in the subcutaneous fascia or rats. Controls, e.g. similar extracts of rat liver or human kidney, did not induce neovascularisation. The endothelium of newly-formed blood vessels contained many mitotic figures. A limitation of this method is that it is qualitative only. In order to develop a quantitative in vitro assay for a tumour angiogenesis factor (TAF), short-term primary cultures were initiated from adult rat brain white matter, as cells from such cultures were shown to be vascular in origin. Addition of fractions containing TAF (B and C) which were active in vivo failed to stimulate thymidine uptake by the cells. The possible reasons for this failure and the therapeutic potential of TAF in cancer control are discussed.