Thus, we decided to assess the impact of ARH3 knockout (KO) in ovarian cancer cell lines with different genetic features, including homozygous BRCA1 mutant COV362 [45], BRCA2 mutant PEO1 [46], which are deficient for homologous recombination repair (HRR), and BRCA1/BRCA2 wild-type OVCAR8 that are HRR-competent despite the hypermethylation of two alleles of the three harbored by these cells [45,47,48] (Fig. 1A and 1B). The gene discussed is BRCA1; the disease is ovarian cancer.