BRCA1 and ovarian serous adenocarcinoma: In a study of 12 high‐grade serous ovarian cancer (HGSOC) patient‐derived xenografts and 21 patient samples (ARIEL2 trial), response and resistance to rucaparib were correlated with methylation status of BRCA1. Methylation‐mediated silencing of all BRCA1 copies predicted response to rucaparib, while heterozygous methylation was associated with resistance to therapy (Kondrashova et al., 2018).