PARP6 suppression, either by the PARP inhibitor AZ0108 or small interfering RNA (siRNA)-mediated knockdown, promotes an anti-tumor response in a panel of breast cancer lines as well as in breast cancer xenografts, likely through the MARylation of CHK1 during mitosis (Wang et al., 2018). The gene discussed is PARP1; the disease is breast carcinoma.