BRCA1 and breast cancer: Similar rescue experiments performed on primary human BRCA1-mutant LP- and BC-derived cells also showed elevated pPLK1 (T210) intensity at the spindle poles (Fig. 5h, Figure S10a) and treatment of these cells with 0.1 nM BI2536 likewise reduced their hyperactive PLK1 (Figure S10b) and normalized their cell division orientation (Fig. 5i).