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. Here, HIF1A is linked to cancer.