Abstract 3859: Alterations in hormone receptors regulome following response to kinase inhibitors in lethal prostate cancer

Abstract The androgen receptor (AR) signaling axis is critical for prostate cancer (PCa) pathogenesis and all subsequent phases of disease progression. Although initial success with androgen deprivation therapy and AR-targeted agents such as enzalutamide or abiraterone, most patients inevitably relapse due to therapeutic resistance. Previous studies have shown that genomic AR is unchanged despite resistance to AR antagonists, and its gene expression is unaltered. Therapeutic resistance is broadly classified into two categories; restoration of AR activity and tumor progression despite AR blockade. Indeed, others have noted an extensive reprogramming of the AR cistrome in clinical and preclinical specimens, where a shift in canonical to non-canonical AR cistrome is associated with an increase in Gleason grade. In previous studies, we observed increases in known AR target genes following exposure to kinase inhibitors which was marked by a decrease in tumor growth. We hypothesized that restoration of canonical AR cistrome can be mediated through kinase inhibition and is associated with re-sensitization to AR-targeted therapy. In addition, we treated cell lines and patient-derived xenograft models of advanced prostate cancer with kinase signaling pathway inhibitors, AR signaling inhibitors, or a combination of both for 24 hours (in vitro) or five days (in vivo). In addition, samples were collected and processed for RNA-seq and ChIP-seq. Our transcriptomic analysis showed enrichment of previously published non-canonical AR target genes in cells resistant to AR-targeted agents. When resistant cells were exposed to kinase inhibitors, we observed an enrichment of canonical AR target genes. In addition, we identified unique AR-enriched peaks at active sites associated with resistance. Through GSEA of gene annotated peaks, we found unique regulatory transcription factor targets, some of which are associated with cell proliferation and differentiation and may play a functional role in AR cistrome adaptation to resistance and survival. Overall, our data suggest that AR transcription adapts to the therapeutic resistance of AR antagonists via the enrichment of non-canonical AR cistrome. Furthermore, restoration of canonical AR cistrome is achieved following kinase signaling pathway inhibition and is associated with re-sensitization to AR-targeted therapy. Citation Format: Remi M. Adelaiye-Ogala, Surendra Gulla, Jonathan E. Bard, David J. VanderWeele, Kathleen Kelly. Alterations in hormone receptors regulome following response to kinase inhibitors in lethal prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3859.