SHLD2 and breast cancer: 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).