A number of drugs used in cancer chemotherapy induce oxidative stress by generation of oxygen free radicals (ROS) which might be an alternative mechanism for their cytotoxic effect via indu-cing apoptosis. In order to clarify the roles of antioxidants in chemotherapy, we investigated Quercetin (3,3’,4’,5,7-pentahyd-roxyflavone) and N-acetylcysteine (NAC) in different cell types treated with anticancer drugs. We studied cytotoxic activity of Topotecan alone and/or in combination with Quercetin in two human breast cancer cell lines, MCF-7 and MDA-MB-231. .
