Although little is known about the function of antioxidant enzymes in cancer cells, recent reports have suggested that enzymes such as glutathione S-transferase, glutathione peroxidase, NADH quinine oxidoreductase-1, peroxiredoxins, thioredoxin, and PPIA (cyclophilin A), protect cancer cells against oxidative stress-induced apoptosis, hypoxia, and chemotherapy [14]. This evidence concerns the gene TXN and cancer.