Amifostine induces anaerobic metabolism and hypoxia-inducible factor 1 alpha.
OBJECTIVE
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.


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.
Departments of Radiotherapy/Oncology, Democritus University of Thrace, 68100, Alexandroupolis, Greece. targ@her.forthnet.gr
Michael I
MI
Koukourakis
Alexandra
A
Giatromanolaki
Wen
W
Chong
Costantinos
C
Simopoulos
Alexandros
A
Polychronidis
Efthimios
E
Sivridis
Adrian L
AL
Harris
D004999:Amifostine / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D015687:Cell Hypoxia / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D019610:Cytoprotection / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007150:Immunohistochemistry; D007262:Infusions, Intravenous; D007668:Kidney / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D008168:Lung / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D008297:Male; D011829:Radiation Dosage; D011837:Radiation-Protective Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D017208:Rats, Wistar; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism*; D015854:Up-Regulation
D001786:Blood Glucose; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011837:Radiation-Protective Agents; D014157:Transcription Factors; D004999:Amifostine