The selectivity of ascorbate-induced cytotoxicity between normal cells and malignant cells may be due to lower levels of peroxide-reducing enzymes such as catalase, glutathione peroxidase, and peroxiredoxins, as well as higher endogenous levels of reactive oxygen species in cancer cells, leading to the less efficient degradation of H2O2 and increased susceptibility to P-AscH− [31,32,43,46,47]. The gene discussed is CAT; the disease is cancer.