Cucurbitacin B and erastin co-treatment synergistically induced ferroptosis in breast cancer cells via altered iron-regulating proteins and lipid peroxidation

Ferroptosis is a unique type of cell death which co-exists with elevated iron, suppressed antioxidative function and increased lipid peroxidation. Recent studies have shown that cancer cells are particularly susceptible to the compounds with ferroptotic activities. Cucurbitacin B (CuB) is a triterpenoid with potent biological properties. It has been demonstrated to induce apoptosis and inhibit metastasis in cancer cells. However, the underlying mechanism of the compound is still not fully understood. In the present study, we investigated the ferroptotic effect of CuB in breast cancer cells and evaluated the impact of its combination with erastin, a ferroptosis inducer. In this regard, MTT assay was performed to analyze cell viability. Lipid peroxidation, oxidative stress and the cellular antioxidant capacity were determined with relevant kits. The expression of ferroptotic proteins were analyzed by western blotting. The results indicated that the combined treatment of CuB and erastin activated the ferroptotic pathways significantly in MCF-7 and MDA-MB-231 breast cancer cells. More importantly, the combination treatment altered the expression of iron-related proteins IREB2 and FPN1. In conclusion, this study demonstrated the ferroptotic potential of CuB in breast cancer cells for the first time, and revealed its impact on the expression of iron-regulating proteins.