Intriguingly, we found that GSK3Bi-induced suppression of HR activity and sensitization to PARPi cytotoxicity occurred only in breast cancer MCF7 cells with intact 53BP1, but no longer affected HR efficiency and PARPi-induced cytotoxicity in 53BP1–/– MCF7 cells (Figure 11, A and B). The gene discussed is TP53BP1; the disease is breast carcinoma.