The aim of this study is to characterize whether a superoxide dismutase (SOD) mimic, Mn3, will act as a radio-sensitizer in tumor cells and radio-protector in normal brain cells. Immunohistochemistry assesses efficacy of treatment mice. A preliminary experiment compares different levels of protein expression at varied timepoints following radiation to provide a baseline for further experimental findings. The first experiment examines the effects of Mn3 and ionizing radiation in U87 tumor cells injected into the flank of nude mice. The second examines the drug's ability to protect normal brain tissue from ionizing radiation in the normal brain containing no tumor. The third study examines the drug’s efficacy in radio-sensitization and radio-protection on mice with the U87 tumor cell line injected intracranially. Results show that in regular brain tissue, non-tumor cells exhibit less oxidative damage and a lower microglia response when treated with the SOD mimic compared to control. In flank tumor tissue, mice treated with the SOD mimic show increased oxidative damage and DNA breakage in the tumor regions. Mice with intracranial tumors show increased DNA oxidation in the tumor of the Mn3 treatment group when compared to the irradiation group.