TXN and prostate carcinoma: For instance, the antioxidant protein thioredoxin 1 (TRX1) is enzymatically active if harboring two -SH groups at cysteine (Cys)32 and Cys35, but becomes inactivated if -SH groups at these two positions were oxidized to disulfides 4, and increased TRX1 protein oxidation was observed in more invasive human prostate cancer cells 5.