BRCA1 and breast cancer: Most importantly, we were also able to experimentally show that RANKL blockade could be used as a preventive strategy in BRCA1-mutation carriers: RANKL blockade in mice carrying a Bcra1 mutation markedly abrogated the occurrence of pre-neoplastic lesions, and after 1 year of treatment only 1 out 13 Brca1-mutant mice showed mammary epithelial neoplasia whereas nearly all untreated control mice developed mammary tumours.