The concept that hormones influence tumor growth originated in 1889 with the proposal of Albert Schinzinger who suggested that breast cancer is related to the ovaries. Several years later, Sir George Beatson observed that remission of disseminated breast cancer could be achieved in premenopausal patients by performing bilateral oophorectomy. As a result of the contri- butions of Hedley Atkins, Charles Huggins and others, additive and ablative hormonal therapies have been widely used for the treatment of advanced breast cancers for several decades. Model systems to study the effects of...