Diminished amounts of manganese-containing superoxide dismutase have been found in all the tumors examined to date. Lowered amounts of the copper-zinc-containing superoxide dismutase have been found in many, but not all, tumors. At the same time, tumors have been shown to produce superoxide radicals. It is shown how diminished enzyme activities along with radical production may lead to many of the observed properties of cancer cells. The apparent exploitation of the differences between normal and cancer cell superoxide dismutase activity in the treatment of cancer is discussed.
Studies from our laboratory described in this review were supported by grants from the Alexander Medical Foundation and the NIH (T32 CA 09125).