Quantitation of extracts containing tumour angiogenesis factor (TAF) by radioimmunometric and radioimmunoassays

A study of angiogenesis factors from five different sources using a radioimmunoassay

The use of a radioimmunoassay (RIA) demonstrated that angiogenic factors from human and animal tumours, normal bovine retinas, myocardial infarcts, synovial fluid from patients with joint diseases and wound fluid shared common antigenic determinants. Values for angiogenesis factors expressed as microgram Walker tumour TAF/mg protein varied from 0.8 (wound fluid) to 207 (myocardial infarct). Activated macrophages produced an angiogenic factor which did not cross-react. Normal tissue extracts which were non-angiogenic by the chicken chorioallantoic membrane assay also failed to cross-react in the RIA. The antigenic similarity of angiogenic factors from such a wide variety of sources suggests that, in order to minimize therapeutic side effects, it would be best to use angiogenic agonists and antagonists locally.

Tumour angiogenesis

A variety of different factors has been implicated in inducing angiogenesis. Their identity and precise mechanisms of action remain elusive. The present treatise summarises the state of our knowledge not only in relation to tumour-induced capillary growth but also for non-neoplastic situations and mechanisms.

Angiogenesis factor from human myocardial infarcts

5 of 8 infarcted human myocardial tissues were shown to contain an angiogenesis factor which resembles that obtained from solid tumours. The concentration of angiogenesis factor, measured by radioimmunoassay, was similar to that in tumours. It is suggested that the myocardial-infarct angiogenesis factor modulates collateral enlargement or ingrowth of new blood vessels in the infarcted tissues.

Quantitation of angiogenesis factor in bovine retina and tumour extracts by means of radioimmunoassay

Using an antiserum raised against tumour angiogenesis factor (TAF) we have developed a radioimmunoassay for retina and tumour angiogenesis factor(s). This antiserum was previously shown to bind to both human and animal tumour extracts and to inhibit the angiogenesis induced by TAF in vivo. TAF from rat Walker tumour was used for iodination by the chloramine-T method. An excess of 125I-labelled TAF was incubated with TAF antibody in the absence (maximum binding) and presence (inhibition of maximum binding) of unlabelled tissue extract. A double antibody technique was used to separate free and bound TAF. Unlabelled human Wilms tumour TAF was used as a standard. The extent of inhibition of 125I-TAF-anti-TAF binding provided a measure of TAF in tissue extracts examined. Extracts of normal bovine retina, cornea, lung, aorta, lymph nodes, iris, vitreous humour, and human tumours and normal human pituitary and liver were assayed. Only bovine retina and human tumours were found to contain angiogenesis factor. These findings, together with our earlier results, suggest that angiogenesis factor from both bovine retina and human tumours induce angiogenesis in vivo and possess common antigenic determinants. The presence of angiogenesis factor in healthy retina and its relationship to neovascularisation in clinical conditions is discussed.

An assay measuring the stimulation of several types of bovine endothelial cells by growth factor(s) derived from cultured human tumor cells

Endothelial cell growth factor(s) from several previously untested human tumor cell lines (i.e., SK-HEP-1, MG63, A375, TE671-C1, RD) were detected using a low cell inoculum growth assay. The final cell density in the 2-cm2 wells was determined by a highly sensitive DNA content measurement performed directly in the tissue culture plates. The sensitivity of the assay to human tumor cell growth factors depended critically on the low cell inocula, 2,000 to 5,000 cells/well. Most of the bovine endothelial cells used were cloned from primary cultures; all the cell lines obtained from various fetal and nonfetal sources responded to the growth factor(s) (up to a 16x stimulation) as well as to endothelial cell growth supplement. Dose response curves showing the cell specific response of bovine endothelial cells were obtained. The growth stimulatory activity and the in vivo chick embryo chorioallantoic membrane assay responses correlated sufficiently to imply that the assay is detecting tumor angiogenesis factor or some closely related activity. This in vitro assay should prove useful in the identification and purification of tumor-derived factors and in the elucidation of the role of these factors in the events comprising angiogenesis.