Furthermore, consistent differences in RAD51 recruitment were observed in irradiated KB1P-G3-derived Brca1−/−trp53−/− murine mammary tumor cell lines polyclonally deleted for either 53bp1 (ref. 46) or shieldin genes Shld2 (ref. 22) or Shld3 (ref. 11) (Extended Data Fig. 5h,i). Here, BRCA1 is linked to breast cancer.