Grdina DJ, Murley JS, Kataoka Y, Baker KL, Kunnavakkam R, Coleman MC, Spitz DR. Amifostine induces antioxidant enzymatic activities in normal tissues and a transplantable tumor that can affect radiation response.
Int J Radiat Oncol Biol Phys 2009;
73:886-96. [PMID:
19215822 DOI:
10.1016/j.ijrobp.2008.10.061]
[Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 10/03/2008] [Accepted: 10/08/2008] [Indexed: 01/24/2023]
Abstract
PURPOSE
To determine whether amifostine can induce elevated manganese superoxide dismutase (SOD2) in murine tissues and a transplantable SA-NH tumor, resulting in a delayed tumor cell radioprotective effect.
METHODS AND MATERIALS
SA-NH tumor-bearing C3H mice were treated with a single 400 mg/kg or three daily 50 mg/kg doses of amifostine administered intraperitoneally. At selected time intervals after the last injection, the heart, liver, lung, pancreas, small intestine, spleen, and SA-NH tumor were removed and analyzed for SOD2, catalase, and glutathione peroxidase (GPx) enzymatic activity. The effect of elevated SOD2 enzymatic activity on the radiation response of SA-NH cells was determined.
RESULTS
SOD2 activity was significantly elevated in selected tissues and a tumor 24 h after amifostine treatment. Catalase and GPx activities remained unchanged except for significant elevations in the spleen. GPx was also elevated in the pancreas. SA-NH tumor cells exhibited a twofold elevation in SOD2 activity and a 27% elevation in radiation resistance. Amifostine administered in three daily fractions of 50 mg/kg each also resulted in significant elevations of these antioxidant enzymes.
CONCLUSIONS
Amifostine can induce a delayed radioprotective effect that correlates with elevated levels of SOD2 activity in SA-NH tumor. If limited to normal tissues, this delayed radioprotective effect offers an additional potential for overall radiation protection. However, amifostine-induced elevation of SOD2 activity in tumors could have an unanticipated deleterious effect on tumor responses to fractionated radiation therapy, given that the radioprotector is administered daily just before each 2-Gy fractionated dose.
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