The knowledge that sex hormones and their receptors drive breast and prostate cancers was a major breakthrough, and the hormone deprivation therapy treatments resulting from this knowledge have saved innumerable lives. Indeed, the hormone deprivation therapy strategy has been the mainstay of treatment for breast and prostate cancers that have spread to other vital organs (i.e. bone, liver, brain) for more than 100 years (breast) or 70 years (prostate). Although initially effective, hormone deprivation therapy is not curative, especially once disease becomes metastatic. After a variable period of response, patients eventually relapse with more lethal forms of disease. Despite new drugs that more effectively inhibit ER or AR, patients still mainly die of ER-driven (breast) or AR-driven (prostate) cancer that becomes resistant to any form of hormone deprivation therapy. Thus, new treatment strategies are required to improve survival rates from these advanced, therapy-resistant stages of disease.