THIOL-BASED ANTIOXIDANTS AND THE EPITHELIAL-MESENCHYMAL TRANSITION IN CANCER.

Abstract

SIGNIFICANCE\nThe epithelial-mesenchymal transition (EMT) is commonly associated with tumor metastasis. Oxidative and nitrosative stress are maintained in cancer cells and are involved in the EMT. Cancer cells are endowed with high levels of enzymatic and non-enzymatic antioxidants which counteract the effects of oxidative and nitrosative stress. Thiol-based antioxidant systems such as the Thioredoxin/Thioredoxin reductase (Trx/TrxR) and Glutathione/Glutaredoxin (GSH/Grx) are continually active in cancer cells, while the Thioredoxin-interacting protein (Txnip), the negative regulator of the Trx/TrxR system, is down regulated. Recent Advances: Trx/TrxR and GSH/Grx systems play a major role in maintaining EMT signaling and cancer cell progression.\n\n\nCRITICAL ISSUES\nEnhanced stress conditions stimulated in cancer cells inhibit EMT signal-ing. The elevated expression levels of the Trx/TrxR and GSH/Grx systems in these cells provide the antioxidant protection necessary to guarantee the occurrence of the EMT.\n\n\nFUTURE DIRECTIONS\nElevation of the intracellular ROS and NO concentrations in cancer cells has been viewed as a promising strategy for elimination of these cells. The devel-opment of inhibitors of GSH synthesis and of the Trx/TrxR system together with genet-ic-based strategies to enhance Txnip levels may provide the necessary means to achieve this goal.