A recombinant MnSOD is radioprotective for normal cells and radiosensitizing for tumor cells.

Organisms exposed to ionizing radiation are mainly damaged by free radicals, which are generated by the radiolysis of water contained in the cells. Recently a significant reduction of tissue injury from irradiation damage was demonstrated by using MnSOD-plasmid/liposome treatments in the protection of murine lung. In this study we show that a new active recombinant human MnSOD (rMnSOD), easily administered in vivo, not only exerts the same radioprotective effect on normal cells and organisms as any MnSOD, but it is also radiosensitizing for tumor cells. In addition, we show how healthy animals, exposed to lethal doses of ionizing radiation and daily injections with rMnSOD, were protected from radiodamage and were still alive 30 days after the irradiation, while animals treated with only PBS solution, in the absence of rMnSOD, died after 7-8 days from the radiotreatments. The molecular analysis of all irradiated tissues revealed that the antiapoptotic AVEN gene appeared activated only in the animals treated in the presence of rMnSOD. The data suggest that rMnSOD deserves to be considered as a pharmaceutical tool for making radiotherapy more selective on cancer cells and to prevent and/or cure the accidental damage derived from exposure to ionizing radiation.