BRCA1 and neoplasm: Analysis of the 48 PARPi-resistant BRCA1-deficient (32 KB1P and 16 KB1PM tumors) tumors revealed that 60% (29/48) of the tumors had restored the capacity to form RAD51 foci, including one tumor with a mixed pattern (RAD51-IRIF-positive and -negative areas) (Figure 1E).