XRCC1 and cancer: Apart from classical BER and SSBR, PARP1, and XRCC1 play a crucial role in the genotoxic response to camptothecin (CPT)-mediated topoisomerase I (Top1) poisoning, and, consequently, combinations of PARP and topoisomerase 1 inhibitors have been tested in clinical cancer therapy (Chowdhuri and Das 2021; Mei et al. 2020; Thomas and Pommier 2019).