PARP1 and breast cancer: The poly(ADP-ribose) polymerase 1 (PARP1) is activated by DNA damage and is able to recruit other proteins to repair DNA single-strand breaks, and PARP inhibitors (PARPi) are an important class of anticancer therapies that target tumors with BRCA1/2 mutations, such as ovarian, BC, lung and pancreatic cancer [246].