PARP1 and breast cancer: While ablation of PARP1 linking to mammary tumor formation (de Murcia et al, 1997; Tong et al, 2007) suggests its tumor suppressing effect, the oncogenic role of PARP1 was implied due to the correlation between its abnormal accumulation and poor prognoses in various types of cancers, including breast, uterine, lung, ovarian, colorectal, and skin cancers (Ossovskaya et al, 2010).