In basal-like breast cancer, a significant increase in bromodomain-containing protein 4 (BRD4), lysine-specific demethylase 5B (KDM5B), and enhancer of zeste homolog 2 (EZH2) activities was detected in tumor cell populations after treatment with MEK and PI3K/mTOR inhibitors. Here, KDM5B is linked to breast carcinoma.