Role of mast cells in experimental tumour angiogenesis

Although the morphological features of angiogenesis are well documented and many promoting factors are known, the pharmacological mechanisms for the development of new vessels are not understood. Compounds found in platelets and/or mast cells--adenosine diphosphate, 5-hydroxytryptamine, histamine and heparin--caused endothelial cell growth stimulation in vitro: tumour angiogenesis factor did not. These same vasoactive compounds, as well as tumour angiogenesis factor, induced neovascularization on the chick chorioallantoic membrane. The increased vascularity produced by tumour angiogenesis factor was associated with considerable numbers of mast cells. These findings, together with an appreciation of the biochemical armoury of the mast cell and how its products could relate to the morphological steps of angiogenesis, and a realization that known anti-angiogenesis factors could all act through inhibition of mast cell products, strongly implicate the mast cell in the inductive mechanisms of neovascularization.