In this study, we investigated the antiproliferative effects and mechanism of PARP inhibitors ABT-888 (Veliparib), BSI-201 (Iniparib) and AZD228 (Olaparib) in breast cancer cell lines with BRCA1 or BRCA2 mutations and 9 different BRCA wild-type cell lines with BRCA1 allelic loss. The gene discussed is PARP1; the disease is breast cancer.