LAUSR

There are ongoing efforts to develop nitric oxide (NO) or S-nitrosothiol (SNO) donors as anticancer agents. Yet, tumor cell defense mechanisms pose a significant problem. We found that treatment of HeLa cancer cells with l-buthionine-sulfoximine (BSO, a glutathione depleting agent) results in significant sensitization to cell death induced by NO or SNO donors. Mechanistically, combined BSO/SNO treatment leads to rapid and profound inhibition of both glutathione and thioredoxin systems, thereby amplifying cellular redox stress, committing the cells to death. Further findings suggest that cells die via a regulated, nonapoptotic mechanism. Using a redox proteomics approach, we identified hundreds of proteins that are oxidized in BSO/SNO-treated cells, including key regulators of cell redox, mitochondrial function and cytoskeletal dynamics. Consistently, the early steps in BSO/SNO-induced cell death involve rapid induction of thiol stress and collapse of the actin cytoskeleton. Similar to the effects seen in HeLa cells, BSO/SNO combination therapy was effective in killing multiple lung cancer cell lines. Our findings provide new insights into the mechanism of nitroso-redox stress-induced cancer cell death and suggest a possible avenue for improving NO/SNO-based anticancer therapies.