Progestogens and risk of breast cancer: a link between bone and breast?

This article reviews the data supporting the role of receptor activator of the nuclear factor kappa (RANK) and its ligand, RANKL, in progestogen-induced breast cancer. Both experimental and clinical studies have been included. The expression of both RANK and RANKL has been described in epithelial cells of both mice and humans. Experiments of gain and loss of function in mice have shown that RANK/RANKL mediate alveologenesis during pregnancy or the estrous cycle. Moreover, the participation of the RANK/RANKL has been detected in models of breast carcinogenesis associated with progestogens-like medroxyprogesterone acetate. Recent clinical studies have found that the expression of RANK is associated with parameters of aggressiveness of the tumor.