PTEN and cancer: The TXNRD/TXN system also catalyzes the reversible reduction of disulfides [49–51] or S-nitrosation [52, 53] of many cancer-associated transcriptional factors (p53, NF-kB, HIF1a), phosphatases (PTEN), kinases, apoptosis regulators (caspase-3, ASK1), and immune system modulators [54], thereby modulating the functions of the target proteins and regulating cellular redox homeostasis, DNA synthesis and repair, cell growth and survival, inflammatory response, and malignant progressions.