The overexpression of catalase in breast cancer cells MCF-7, a human-derived breast cancer cell line, not only impaired the proliferation and migration of the cancer cells but also improved sensitivity to anticancer treatments like doxorubicin, cisplatin, and paclitaxel when compared to parent cells and raised the resistance to the prooxidant combination ascorbate and menadione (Asc/Men) [177]. The gene discussed is CAT; the disease is cancer.