7542 Androgen Receptor Oligomerization State Allows Cells to Exhibit Non-Linear Dose Responses to Androgens Resulting in Distinct Biological Outputs

Abstract Disclosure: R. Safi: None. S.E. Wardell: None. P. Watkinson: None. X. Qin: None. M. Lee: None. S. Park: None. T. Krebs: None. E. Dolan: None. T. Tsuji: None. S. Nayak: None. M. Khater: None. M. Newlin: None. M. Kirkland: None. Y. Xie: None. H. Long: None. E. Fink: None. S.W. Fanning: None. S. Runyon: None. M. Brown: None. S. Xu: None. K. Owzar: None. J.D. Norris: None. D.P. McDonnell: None. An unanswered fundamental question in androgen action is how cells recognize and respond in a non-linear fashion to different levels of androgens to elicit distinct biological outputs such as occurs in prostate cancer (PCa) cells. Indeed, most PCa express the androgen receptor (AR), and tumor growth and progression are facilitated by exceedingly low levels of systemic or intratumorally produced androgens. Paradoxically, high dose androgens have been used to treat patients with late-stage metastatic PCa. We have determined that androgen dose regulates the relative cellular abundance of AR monomers and dimers in cells and that the biological output of each oligomeric form of the receptor is different. Using in vitro systems that model exposure from castrate (low dose; LD) to eugonadal levels and above (high dose; HD) of androgens, we have determined that the global changes in gene expression are substantially different, with the changes induced by LD androgens (monomeric AR) being associated with cell proliferation, and HD androgens (dimeric AR) inducing a differentiated phenotype. A similar distinction in response to androgen levels was observed in vivo. Using a chemical biology strategy, we identified ligands which freeze AR in a monomeric form and demonstrate that these compounds faithfully recapitulate the LD biology exhibited by physiological AR agonists. Mechanistically, we determined that monomeric AR facilitates a non-genomic activation of the mTOR signaling pathway to drive proliferation, while the dimer suppresses c-MYC expression, inhibit proliferation, and drive a transcriptional program associated with a differentiated phenotype. These findings highlight the inherent liabilities in current approaches used to inhibit AR-action in prostate cancer and are instructive as to strategies that can be used to develop new therapeutics for this disease and other androgenopathies. Presentation: 6/3/2024