The role of oleuropein in oxidative stress in breast cancer

Breast cancer is the most diagnosed cancer among women compared to other cancer types. Paclitaxel (PTX) is an effective chemotherapeutic agent that belongs to taxane class and is widely used in the treatment of many cancers such as breast cancer, ovarian cancer, lung cancer. Oleuropein (OLE) is a natural polyphenol with anticancer, antioxidant, antidiabetic, cardioprotective and neuroprotective effects. Within the scope of this thesis study, the effects of OLE and PTX combinations on oxidative stress of MCF-7 cell line were investigated. The xCELLigence RTCA method was used to determine the cytotoxic effects of OLE and PTX in the MCF-7 cell line. The IC50 values of OLE and PTX in the MCF-7 cell line were calculated as 230 µM and 7.5 µM, respectively. In order to determine oxidative stress, Oxidative Stress Index (OSI) was calculated by measuring Total Oxidant (TOS) and Total Antioxidant (TAS) states. It was determined that the combinations of OLE and PTX synergistically inhibited the proliferation of the MCF-7 cell line and increased the TAS level treating with lower concentrations. The levels of superoxide dismutase (SOD), reduced glutathione (GSH) and malondialdehyde (MDA), which are oxidative stress markers, were also measured after treatment of cells with PTX, OLE and combination. It was observed that the SOD and MDA levels increased in the combination groups compared to the OLE and PTX application alone, on the other had the level of GSH decreased.