Preparation and Characterization of a Glutathione-Responsive Doxorubicin Prodrug Modified by 2-Nitrobenzenesulfonamide Group—Its Selective Cytotoxicity Toward Cells with Enhanced Glutathione Production

GSH biosynthesis is enhanced in cancer cells that express the variant isoform of the surface antigen CD44 (CD44v), which is overexpressed in certain types of cancer. The GSH-responsive prodrug Ns-Dox was prepared by modifying the GSH-responsive group 2-nitrobenzene sulfonyl (Ns) with the model drug doxorubicin (Dox). Its function was evaluated based on its molecular interaction with model DNA in terms of its binding constant (<i>K_a</i>). The association constant of Ns-Dox was lower, and its interaction with model DNA was weaker compared to that of Dox, suggesting that Ns-Dox may act as a less toxic prodrug. HCT116 cells with high CD44v expression and GSH levels and BT474 cells with low CD44v expression and GSH levels were used. The addition of Ns-Dox to HCT116 cells produced cytotoxic effects similar to those of Dox. In contrast, a significant difference in viability was observed between Ns-Dox- and Dox-treated BT474 cells at low concentrations. These findings suggest that Ns-Dox functions as a prodrug with low environmental toxicity and a lower GSH concentration in cancer cells. It is efficiently activated to Dox in cells with high GSH production, demonstrating its cell-killing effects.