BACKGROUND: Amifostine (WR-2721, delivered as Ethyol) is a phosphorylated 
aminothiol compound clinically used in addition to cis-platinum to reduce the 
toxic side effects of therapeutic treatment on normal cells without reducing 
their efficacy on tumour cells. Its mechanism of action is attributed to the 
free radical scavenging properties of its active dephosphorylated metabolite 
WR-1065. However, amifostine has also been described as a potent hypoxia-mimetic 
compound and as a strong p53 inducer; both effects are known to potently 
modulate vascular endothelial growth factor (VEGF-A) expression. The angiogenic 
properties of this drug have not been clearly defined.
METHODS: Cancer cell lines and endothelial cells were used in culture and 
treated with Amifostine in order to study (i) the expression of angiogenesis 
related genes and proteins and (ii) the effects of the drug on VEGF-A induced in 
vitro angiogenesis.
RESULTS: We demonstrated that the treatment of several human cancer cell lines 
with therapeutical doses of WR-1065 led to a strong induction of different 
VEGF-A mRNA isoforms independently of HIF-1alpha. VEGF-A induction by WR-1065 
depends on the activation of the eIF2alpha/ATF4 pathway. This up-regulation of 
VEGF-A mRNA was accompanied by an increased secretion of VEGF-A proteins fully 
active in stimulating vascular endothelial cells (EC). Nevertheless, direct 
treatment of EC with amifostine impaired their ability to respond to exogenous 
VEGF-A, an effect that correlated to the down-regulation of VEGFR-2 expression, 
to the reduction in cell surface binding of VEGF-A and to the decreased 
phosphorylation of the downstream p42/44 kinases.
CONCLUSIONS: Taken together, our results indicate that amifostine treatment 
modulates tumour angiogenesis by two apparently opposite mechanisms - the 
increased VEGF-A expression by tumour cells and the inhibition of EC capacity to 
respond to VEGF-A stimulation.