We used the BRCA1 null human ovarian cancer cell line UWB1.289 (named UW here) and its complemented derivative UW+BRCA1 (DelloRusso et al., 2007), plus the human osteoscarcoma U2OS cells, which were siRNA depleted for BRCA1. We first confirmed that UW cells were more sensitive to cisplatin than wild-type cells (Figure 1A) (Lohse et al., 2015) and that treatment with a single cisplatin dose leads to fork degradation in a BRCA-deficient background (Lemaçon et al., 2017). This evidence concerns the gene BRCA1 and ovarian cancer.