On the basis of these results, we evaluated PARP inhibitors as single-agent therapy in 14 breast cancer cell lines: 4 BRCA mutant lines with BRCA1 allelic loss, 9 BRCA wild-type lines with BRCA1 allelic loss, and 1 BRCA wild-type line without BRCA1 allelic loss. Here, PARP1 is linked to breast cancer.