Currently, the role of PARP1 in the base excision repair of DNA SSBs and abasic sites has been the basis for the use of PARPi as synthetic lethal monotherapy for BRCA1/2 mutant cancers that are defective in HRR pathway, or in combination with chemicals or external radiation for cancers with apparently normal DNA repair capacity [19–21]. Here, PARP1 is linked to cancer.