The bifunctional role of steroid hormones: implications for therapy in prostate cancer

Ablation of the androgen-signaling axis is currently a dominant theme in developmental therapeutics in prostate cancer. Highly potent inhibitors of androgen biosynthesis and androgen receptor (AR) function have formally improved survival in castration-resistant metastatic disease. Resistance to androgen-ablative strategies arises through diverse mechanisms. Strategies to preserve and extend the success of hormonal therapy while mitigating the emergence of resistance have long been of interest. In preclinical models, intermittent hormonal ablative strategies delay the emergence of resistant stem-cell-driven phenotypes, but clinical studies in hormone-naive disease have not observed more than noninferiority over continual androgen ablation. In castration-resistant disease, response and improvement in subjective quality of life with therapeutic testosterone has been observed, but so too has symptomatic and life-threatening disease acceleration. The multifunctional and paradoxical role of steroid hormones in regulating proliferation and differentiation, as well as cell death, requires deeper understanding. The lack of molecular biomarkers that predict the outcome of hormone supplementation in a particular clinical context remains an obstacle to individualized therapy. Biphasic patterns of response to hormones are identifiable in vitro, and endocrine-regulated neoplasms that proliferate after prolonged periods of hormone deprivation appear preferentially sex steroid-suppressible. This review examines the relevance of a translational framework for studying therapeutic androgens in prostate cancer.