A report that superoxide dismutase inhibitors selectively kill leukemia cells provides evidence that SOD could be a target to treat cancer, as well as an alternative explanation of how EntreMed Inc.'s 2-methoxyestradiol compound works. M.D. Anderson researchers last week reported in Nature that SOD inhibition caused free-radical damage to mitochondrial membranes, and subsequent apoptosis of leukemia cells.

SOD protects cells from damage by free radicals that are generated as a result of normal oxidative metabolism when electrons leak out of mitochondria. The toxic free radicals are