Increase in oxidative stress via glutathione reductase inhibition as a novel approach to enhance cancer sensitivity to doxorubicin

2357 Cancer drug resistance is a major cause of cancer treatment failure, and developing novel approaches to increase cancer sensitivity to chemotherapy is an ongoing research effort. Several anticancer agents, including doxorubicin, induce the production of damaging reactive oxygen species as part of their mechanism of action. Drug resistance to these medications can develop through increased levels of the intracellular antioxidant glutathione. Mechanisms of increasing the state of oxidative stress could enhance the sensitivity of cancer cells toward these chemotherapeutic agents. Modulation of intracellular oxidative stress via glutathione reductase inhibition is a novel approach to improve the activity of cancer chemotherapy. The objective of this project was to evaluate the effect of glutathione reductase inhibition on doxorubicin activity in a human ovarian cancer cell line. A novel irreversible glutathione reductase inhibitor, 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethyl-sulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (G0026), was used in this study. OVCAR-3 cells were treated with G0026 for 2 hours or 24 hours followed by treatment with doxorubicin. In order to determine the effect of the combination of G0026 and doxorubicin on glutathione and oxidative stress, the cellular content of glutathione, glutathione disulfide, total thiols, and total disulfides was determined. G0026 significantly increased the sensitivity of OVCAR-3 cells to doxorubicin; the best synergistic response was observed with a two hour pretreatment with G0026 25 μM. In addition, the combination of the glutathione reductase inhibitor and doxorubicin showed higher intracellular oxidative stress than doxorubicin alone. These findings indicate that an increase in oxidative stress produced via glutathione reductase inhibition can increase cancer response to chemotherapy.