A hypoxic response induced in MatLyLu cells by cobalt chloride results in an enhanced angiogenic response by the chick chorioallantoic membrane.

Hypoxia is an important regulator of hypoxia inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) expression. Using Dunning rat prostate tumour cells (MatLyLu) we examined the induction of HIF-1alpha and VEGF by hypoxia and if the induction of these proteins would lead to angiogenesis in the chick chorioallantoic membrane (CAM). MatLyLu cells were exposed to 1% O2, in 5.25% CO2 and 94.75% N2, or treated with 100 mM CoCl2 to simulate hypoxia. Conditioned medium was analyzed using Western blots for HIF-1alpha or VEGF. VEGF levels were quantified using ELISA. Hypoxia significantly increased both HIF-1alpha and VEGF protein production. MatLyLu cells (1x10(6) viable cells in 50 microl of medium) grown under normoxic conditions induced in angiogenesis in the CAM, evaluated by the formation of a spoke wheel, and in cross sections by the number of blood vessels, following 5-day culture. This response was significantly increased using CoCl2-treated cells. Culture medium alone with or without CoCl2 was not angiogenic. These results provide direct evidence for the role of hypoxia in the induction of HIF-1alpha and VEGF which act as key angiogenic signals.