PURPOSE: The cytoprotective mechanism of amifostine (WR-2721) implies free 
radical scavenging and DNA repair activities. We investigated additional 
cytoprotective pathways involving intracellular hypoxia and the activation of 
the hypoxia-inducible factor (HIF) pathway, a key transcription factor 
regulating glycolysis, angiogenesis and apoptosis, which is also linked with 
radioresistance.
MATERIALS AND METHODS: The glucose and oxygen levels in the peripheral blood of 
patients receiving 1000 mg amifostine were determined at various time-points in 
order to investigate the metabolic changes induced by amifostine. MDA468 breast 
tumor cell lines were incubated with a high amifostine concentration (10 m M) to 
overcome the natural resistance of cancer cells to influx of the non-hydrolyzed 
WR-2721, and the HIF1 alpha protein levels were determined by Western blot 
analysis. In vivo experiments with Wistar rats were performed in order to assess 
immunohistochemically changes in the intracellular accumulation of HIF1 alpha 
induced by amifostine (200 mg/kg).
RESULTS: By 30 min following amifostine administration, the hemoglobin oxygen 
saturation and pO(2) levels had increased in the peripheral blood while glucose 
levels had reduced, providing evidence that normal tissue metabolism switches to 
glycolytic pathways. Incubation of cell lines with amifostine resulted in HIF1 
alpha induction. In Wistar rats administration of amifostine resulted in 
increased HIF1 alpha accumulation in normal tissues.
CONCLUSIONS: Since it is doubtful whether dephosphorylation of amifostine to the 
active metabolite WR-1065 occurs within tumoral tissues (an acidic environment 
that lacks vascular alkaline phosphatase activity), intracellular hypoxia and 
upregulation of HIF1 alpha represents an additional, normal tissue-specific, 
amifostine cytoprotective pathway.