Ovarian cancer is one of the most deadly cancers among women in the United States (1) and around the world (2). Approximately 90% of ovarian neoplasms are epithelial ovarian cancer (EOC) (1), a heterogeneous disease that can be categorized into five major histotypes (1). Genetic factors have an important impact on EOC etiology and large-scale genome-wide association studies (GWAS) have identified 34 common risk loci for EOC to date (3). Of these, 27 are specific to the most common histotype, serous EOC (3). Yet known loci are estimated to account for only a small proportion (~6.4%) of EOC risk (3). Further, causal genes at most loci and the underlying pathogenic mechanisms remain to be identified.