CHEK1 and breast cancer: ATM phosphorylates and stabilizes zinc (Zn) finger E-box binding homeobox 1(ZEB1) in response to DNA damage, subsequently, ZEB1 interacts with USP7 and enhances its ability to deubiquitylate and stabilize CHK1, thereby promoting CHK1-mediated homologous recombination-dependent DNA repair and resistance to IR in breast cancer cells (4).