Recently, Bauer et al. have demonstrated that singlet delta oxygen, 1O2, which is generated through the interaction between CAP-derived H2O2 and NO2−, is at the origin of a cascade reaction in tumor cells, but not in normal cells, leading to inactivation of membrane-associated catalase, which in turns favors H2O2 uptake and triggers cell death [37,82]. This evidence concerns the gene CAT and neoplasm.