Mutual exclusivity of mutations in cancer can be used to identify vulnerabilities that can be exploited therapeutically, such as the observation that cyclin E1 amplification is mutually exclusive with BRCA1 mutation in high-grade serous ovarian cancers and that BRCA1 is selectively required for survival of cyclin E1 amplified cells (88). This evidence concerns the gene BRCA1 and ovarian serous adenocarcinoma.