Abstract
Endothelial cell stimulating angiogenesis factor (ESAF) is a potent, low molecular mass mitogen, specific for endothelial cells. In common with various protein growth factors, it displays angiogenic activity in a variety of biological test systems. However, it differs from these other factors by virtue of its low molecular mass and its ability to activate latent matrix metalloproteinases in a dose dependent manner. This activity has been used to quantify the factor in both normal and diseased brain tissue. The concentration of ESAF determined in biopsies from different types of intracranial tumours varied: in some tumour types the level was close to that of control samples whereas in others it rose to levels comparable to those encountered in the pineal gland, the richest source of ESAF in mature mammals. Tumours considered to be benign contained significantly less ESAF than those neoplasms classified as being malignant (P = 0.025). There was also a correlation between the mitotic activity of tumour samples, as determined by conventional H & E histochemical staining and the ESAF concentration present. These findings agree with previous studies in which elevated ESAF levels have been found in tissue where proliferation of vascular elements has been observed.
Highlights
It has been shown that Endothelial cell stimulating angiogenesis factor (ESAF) activates latent collagenase (Weiss et al, 1983) by reversing the inhibition of this enzyme by tissue inhibitor of metalloproteinases (McLaughlin et al, 1991). These findings suggest that ESAF has an important role in the connective tissue destruction associated with blood vessel penetration
When semi-purified fractions of the biopsy samples were tested on the chick yolk sac membrane, positive results were obtained. This indicates the presence of an angiogenic factor (Figure 1) and suggests the presence of ESAF in these samples
The concentration of ESAF in control brain samples were of the same order as those present in bovine brain and retina and rat brain, but were considerably less than those found in human or bovine pineal glands
Summary
As large a biopsy as possible was taken from each tumour and stored at -20°C until processing for the extraction of ESAF. Tumour classification was based upon histological examination of biopsy specimens taken adjacent to the area where the samples for ESAF determination had been obtained. After centrifugation at 20000 g (1 h, 4'C) the supernatant was assayed for protein (Lowry et al, 1951) prior to ultrafiltration on a YM5 filter membrane (5000 Mr exclusion limit) (Amicon, Stonehouse, Glou., UK) with five volumes of bicarbonate buffer. Assay of angiogenic material for its ability to activate latent collagenase was performed according to the method of Weiss et al (1983). The active material eluting from the octodecyl silica column passed readily through a membrane with an exclusion limit of 3000 Mr The apparent molecular mass was established by gel filtration on a Bio-Gel P-2 (Weiss et al, 1979). After concentration x 100 the fluid was applied to an ACA col-
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