Comprehensive Profiling of the Androgen Receptor in Liquid Biopsies from Castration-resistant Prostate Cancer Reveals Novel Intra-AR Structural Variation and Splice Variant Expression Patterns

• Published in: European urology 2017-08, Vol.72 (2), p.192-200
• Main Authors: De Laere, Bram, van Dam, Pieter-Jan, Whitington, Tom, Mayrhofer, Markus, Diaz, Emanuela Henao, Van den Eynden, Gert, Vandebroek, Jean, Del-Favero, Jurgen, Van Laere, Steven, Dirix, Luc, Grönberg, Henrik, Lindberg, Johan
• Format: Article
• Language: English
• Subjects: Androgen receptor; Antineoplastic Agents, Hormonal - therapeutic use; AR splice variants; AR-V7; Castration-resistant prostate cancer; Circulating tumour DNA; Disease-Free Survival; DNA Copy Number Variations; Drug Resistance, Neoplasm - genetics; Endocrine treatment; Feasibility Studies; Gene Dosage; Gene Expression Profiling - methods; Gene Expression Regulation; Genetic Predisposition to Disease; Genetic Variation; Humans; Kaplan-Meier Estimate; Liquid Biopsy; Male; Medicin och hälsovetenskap; Phenotype; Pilot Projects; Point Mutation; Predictive Value of Tests; Prostatic Neoplasms, Castration-Resistant - drug therapy; Prostatic Neoplasms, Castration-Resistant - genetics; Prostatic Neoplasms, Castration-Resistant - mortality; Prostatic Neoplasms, Castration-Resistant - pathology; Protein Conformation; Protein Isoforms; Receptors, Androgen - chemistry; Receptors, Androgen - genetics; Structural variation; Time Factors; Transcriptome; Treatment Outcome; Urology
• ISSN: 0302-2838; 1873-7560; 1873-7560
• DOI: 10.1016/j.eururo.2017.01.011

Abstract Background Expression of the androgen receptor splice variant 7 (AR-V7) is associated with poor response to second-line endocrine therapy in castration-resistant prostate cancer (CRPC). However, a large fraction of nonresponding patients are AR-V7–negative. Objective To investigate if a comprehensive liquid biopsy–based AR profile may improve patient stratification in the context of second-line endocrine therapy. Design, setting, and participants Peripheral blood was collected from patients with CRPC ( n = 30) before initiation of a new line of systemic therapy. We performed profiling of circulating tumour DNA via low-pass whole-genome sequencing and targeted sequencing of the entire AR gene, including introns. Targeted RNA sequencing was performed on enriched circulating tumour cell fractions to assess the expression levels of seven AR splice variants (ARVs). Outcome measurements and statistical analysis Somatic AR variations, including copy-number alterations, structural variations, and point mutations, were combined with ARV expression patterns and correlated to clinicopathologic parameters. Results and limitations Collectively, any AR perturbation, including ARV, was detected in 25/30 patients. Surprisingly, intra-AR structural variation was present in 15/30 patients, of whom 14 expressed ARVs. The majority of ARV-positive patients expressed multiple ARVs, with AR-V3 the most abundantly expressed. The presence of any ARV was associated with progression-free survival after second-line endocrine treatment (hazard ratio 4.53, 95% confidence interval 1.424–14.41; p = 0.0105). Six out of 17 poor responders were AR-V7–negative, but four carried other AR perturbations. Conclusions Comprehensive AR profiling, which is feasible using liquid biopsies, is necessary to increase our understanding of the mechanisms underpinning resistance to endocrine treatment. Patient summary Alterations in the androgen receptor are associated with endocrine treatment outcomes. This study demonstrates that it is possible to identify different types of alterations via simple blood draws. Follow-up studies are needed to determine the effect of such alterations on hormonal therapy.