Abstract LB048: AR-targeted linked-read sequencing reveals complex AR structural variants in CRPC tumors

Abstract Inhibition of the androgen receptor (AR) transcription factor is the mainstay therapeutic strategy for systemic prostate cancer. However, development of a resistance phenotype termed castration resistant prostate cancer (CRPC) enables disease progression that underlies virtually all prostate cancer mortality. In the majority of CRPC, AR is transcriptionally re-activated in part due to accumulation of numerous alterations in the AR gene. These genomic alterations include missense mutations in exons that encode the ligand binding domain of AR, amplification of the AR gene body and/or an upstream transcriptional enhancer, and AR structural variants (SVs) resulting from inaccurate repair of DNA double strand breaks. In CRPC patient samples, these AR genomic alterations co-occur within tumors, which makes elucidating the fitness contribution of each alteration difficult. While short-read DNA sequencing has allowed for characterization of these events, they are underpowered to preserve linkage information. To address this challenge, we performed AR-targeted linked-read DNA-sequencing of CRPC cell line and patient derived xenograft (PDX) models with the goal of resolving sub-clonal and complex AR SVs. This approach confirmed the heterogeneity of AR SVs in these PDXs, including phased AR SVs that can be traced back to a single high molecular weight DNA molecule. These phased AR SVs were consistently found to co-occur in CRPC specimens with amplification of AR. Our results define a new class of AR SVs where multiple rearrangements co-occur on amplified DNA molecules to yield a complex array of AR gene structures in CRPC. Citation Format: Andrej Zivanovic, Sarah A. Munro, Jeffrey T. Miller, Yingming Li, Courtney N. Passow, Scott M. Dehm. AR-targeted linked-read sequencing reveals complex AR structural variants in CRPC tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB048.