Mast cells and tumour angiogenesis: the tumor-mediated release of an endothelial growth factor from mast cells.

Exposure to tumour cells has previously been shown to induce mast cells to degranulate and release heparin. Isolated mast-cell granules were found to be mitogenic for endothelial cells in vitro. This effect was a property of mast-cell heparin, whose potency as a mitogen exceeded that of commercial heparins. The basis of this difference lay in the proteoglycan structure of the molecule. The release of heparin in mast-cell-tumour co-cultures was examined by both endothelial cell proliferation and isotopic techniques. The kinetics and mode of release are described. The results are discussed in relation to the role of the mast cell in angiogenesis assays and tumour neovascularization.