"Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer mortality in women worldwide. The recently identified Receptor Activator of Nuclear Factor (NF)-κB (RANK)-axis has stimulated novel research in the field of breast cancer etiology, treatment, and prevention. Experimental data implicate RANK signalling in mammary tumor development. Preliminary human data show increased RANK expression correlated with poor outcome, and circulating concentrations of osteoprotegerin, the decoy RANK receptor inhibiting RANK-axis signalling, are increased in several conditions associated with decreased risk of breast cancer (e.g. pregnancy).The proposed research will provide the first evidence on the role of pre-diagnosis RANK-axis members in the etiology of breast cancer in the EPIC cohort, the largest prospective breast cancer case-control study worldwide, and in a complementary study in the unique Finnish Maternity Cohort. A RANK-inhibitor is clinically available and these studies have the potential to inform primary prevention trials. The research will be completed at the internationally recognized German Cancer Research Center (DKFZ).The fellow`s knowledge transfer objectives capitalize on almost a decade of research experience and established networks in U.S. pregnancy cohorts and Harvard University`s Nurses` Health Study. The fellow will: (1) Promote scientific exchange with U.S.-based cohorts and provide subject area expertise; (2) Broaden data analysis expertise at DKFZ to foster long-term collaborations among colleagues; and, (3) Lead and initiate cancer research projects and form strategic professional networks with European colleagues to develop ongoing collaborations.The novel research will strengthen DKFZ`s position as a center for innovative research in cancer epidemiology and the fellowship provides a unique opportunity to reinforce and expand collaborations between scientists at DKFZ and U.S. institutions."