Although various stimuli can induce ROS in cancer cells; excessive levels are, similar to normal cell, kept in check by antioxidant proteins such as peroxiredoxins (Prdx), superoxide dismutase (SOD), catalase, thioredoxin reductase (TrxR), and nuclear factor erythroid 2-related factor 2 (Nrf2). This evidence concerns the gene NFE2L2 and cancer.