Beyond breast cancer, early phase clinical trials with Parp inhibitors in combination with standard chemotherapy have been met with either partial responses, or a lack of clinically relevant responses in multiple types of solid tumors (Plummer et al., 2008; Khan et al., 2011; Kummar et al., 2011, 2012; Rajan et al., 2012). Here, PARP1 is linked to breast cancer.