Abstract A037: Coordinated activity between AR-V7 and glucocorticoid receptor drives resistance to androgen receptor signaling inhibition

Abstract Introduction Prostate cancer (PC) remains a leading cause of cancer death among men, with androgen receptor signaling inhibition (ARSI) forming a cornerstone of treatment. However, tumors often develop therapeutic resistance through mechanisms that partially restore canonical androgen receptor (AR) signaling. These include the expression of ligand-independent AR splice variants (e.g. AR-V7) or the upregulation and activation of the glucocorticoid receptor (GR), an alternative hormone receptor that can bypass AR to reactivate oncogenic signaling. Despite their well-defined individual roles in driving PC progression, a cooperative function of GR and AR-V7 in therapeutic resistance had not been previously explored. We hypothesize that AR-V7 and GR interact to drive a coordinated transcriptional program leading to accelerated tumor progression. Methods We used NanoBRET assays to examine heterodimerization between exogenously expressed AR-V7 and NR3C-family receptors. Endogenous interactions between AR-V7 and GR were demonstrated using co-immunoprecipitation (Co-IP), and proximity ligation assays (PLA) in 22Rv1 and VCaP PC cell lines. Chromatin interactions were evaluated via ChIP-seq, ChIP-PCR, and sequential ChIP. Gene expression was assessed using RNA-seq and Ingenuity Pathway Analysis (IPA), and tumor proliferation was measured using incuCyte and counting assays. We also evaluated the ability of selective GR antagonist (SGRA) to disrupt the interaction between AR-V7 and GR. Results We found interactions between AR-V7 and both AR-full length (AR-FL) and GR, which was abrogated by mutation within the AR-V7 D-box domain, suggesting these interactions occur through heterodimerization. Co-IP and PLA experiments in 22Rv1 and VCaP cells demonstrated that following ARSI, where AR-FL activity is abrogated and when GR is active, the interaction between AR-V7 and GR increases. To further assess their interaction with chromatin, we showed that AR-V7 and GR occupy several shared genomic regions, and co-occupancy at the FKBP5 promoter was confirmed by ChIP-re-ChIP. RNA-seq revealed a distinct transcriptional program driven by coordinated activity between AR-V7 and GR that is enriched in genes that promote proliferation and survival. Following ARSI, we observe accelerated proliferation when both AR-V7 and GR are activated. Finally, we demonstrate GR antagonism with SGRA disrupts the interaction between AR-V7 and GR and decreases proliferation in AR-V7, GR-active PC models. Discussion Our findings reveal a novel mechanism of ARSI resistance in which AR-V7 associates with GR to drive a coordinated oncogenic program. Importantly, SGRA can disrupt this interaction and blunt its functional consequences, offering a potential therapeutic approach for AR-V7+/GR+ prostate cancer patients. Citation Format: Yuhan Zhang, Eric Bueter, Phillip Selman, David Hosfield, Anthony Williams, Patricia Madel, Arunangsu Dey, Christopher Henning, Megan Mendez, Erin McAuley, Donald Vander Griend Vander Griend, Geoffrey Greene, Suzanne Conzen, Russell Szmulewitz. Coordinated activity between AR-V7 and glucocorticoid receptor drives resistance to androgen receptor signaling inhibition [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr A037.