PARP1 and breast cancer: Among them, a dozen PARP1/2 inhibitors are in clinical trials and four inhibitors (olaparib, rucaparib, niraparib, and talazoparib) have been approved by the US food and drug administration (FDA) for the treatment of breast cancer and ovarian cancer with breast cancer susceptibility gene 1/2 (BRCA1/2) genetic deficiency, fallopian tube carcinoma and peritoneal carcinoma (Gunderson and Moore, 2015; Dockery et al., 2017; Scott, 2017; Hoy, 2018).