Mechanisms of Redox Regulation of Chemoresistance in Tumor Cells by Phenolic Antioxidants

Effects of water-soluble sulfur-containing phenolic antioxidants sodium 3-(3′-tert-butyl-4′- hydroxyphenyl)propyl thiosulfonate and potassium 3,5-dimethyl-4-hydroxybenzyl thioethanoate on chemoresistance in tumor cells have been studied. The studied phenolic antioxidants cause oppositely directed changes in the redox properties and chemoresistance in tumor cells. Potassium 3,5-dimethyl-4-hydroxybenzyl thioethanoate increases redox buffering capacity and doxorubicin resistance in tumor cells. Sodium 3-(3′- tert-butyl-4′-hydroxyphenyl)propyl thiosulfonate reduces the redox buffering capacity, which leads to a decrease in the chemoresistance of tumor cells. These observations suggest that one of the key mechanisms responsible for the formation of tumor cell resistance to antitumor compounds is the attenuation of apoptosis through increase of redox buffering capacity. The dependence of protein sensor redox state on oxidant concentrations and on redox buffering capacity in cells has been determined based on the proposed biophysical model of redox-dependent mechanism of apoptosis activation.