In addition to the now experimentally well validated role of RANKL/RANK/OPG in the sex hormone and BRCA1 mutation-driven mammary cancer tumorigenesis, it has also been reported that this pathway can induce epithelial-mesenchymal transition (EMT) in breast cancer cells, as well as in prostate and endometrial cancers (95–98), suggesting that RANKL/RANK supports tumorigenesis in various epithelial cancers. Here, BRCA1 is linked to breast cancer.