BRCA2 and breast cancer: Furthermore, persistent SSBs have been shown to stall and collapse the replication fork, leading to DSB [35,36].HR-competent cells can repair DSBs for cell survival, whereas in cells with defects caused by mutations in breast cancer-associated antigens (BRCA1 or BRCA2) or other HR-associated proteins, the damage remains unrepaired, leading to cell death (Figure 1) [13].