Novel Junction-specific and Quantifiable In Situ Detection of AR-V7 and its Clinical Correlates in Metastatic Castration-resistant Prostate Cancer

Yezi Zhu; Adam Sharp; Courtney M Anderson; John L Silberstein; Maritza Taylor; Changxue Lu; Pei Zhao; Angelo M De Marzo; Emmanuel S Antonarakis; Mindy Wang; Xingyong Wu; Yuling Luo; Nan Su; Daniel Nava Rodrigues; Ines Figueiredo; Jonathan Welti; Emily Park; Xiao-Jun Ma; Ilsa Coleman; Colm Morrissey; Stephen R Plymate; Peter S Nelson; Johann S de Bono; Jun Luo

doi:10.1016/j.eururo.2017.08.009

Novel Junction-specific and Quantifiable In Situ Detection of AR-V7 and its Clinical Correlates in Metastatic Castration-resistant Prostate Cancer

Eur Urol. 2018 May;73(5):727-735. doi: 10.1016/j.eururo.2017.08.009. Epub 2017 Sep 1.

Authors

Yezi Zhu¹, Adam Sharp², Courtney M Anderson³, John L Silberstein¹, Maritza Taylor¹, Changxue Lu¹, Pei Zhao¹, Angelo M De Marzo⁴, Emmanuel S Antonarakis⁵, Mindy Wang³, Xingyong Wu³, Yuling Luo³, Nan Su³, Daniel Nava Rodrigues⁶, Ines Figueiredo⁶, Jonathan Welti⁶, Emily Park³, Xiao-Jun Ma³, Ilsa Coleman⁷, Colm Morrissey⁸, Stephen R Plymate⁸, Peter S Nelson⁹, Johann S de Bono¹⁰, Jun Luo¹¹

Affiliations

¹ Department of Urology, The James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
² The Institute for Cancer Research, London, UK; The Royal Marsden NHS Foundation Trust, London, UK.
³ Advanced Cell Diagnostics, Newark, CA, USA.
⁴ Department of Urology, The James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
⁵ Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
⁶ The Institute for Cancer Research, London, UK.
⁷ Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
⁸ University of Washington, Seattle, WA, USA.
⁹ Fred Hutchinson Cancer Research Center, Seattle, WA, USA; University of Washington, Seattle, WA, USA.
¹⁰ The Institute for Cancer Research, London, UK; The Royal Marsden NHS Foundation Trust, London, UK. Electronic address: johann.de-bono@icr.ac.uk.
¹¹ Department of Urology, The James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. Electronic address: jluo1@jhmi.edu.

Abstract

Background: Androgen receptor splice variant 7 (AR-V7) has been implicated in resistance to abiraterone and enzalutamide treatment in men with metastatic castration-resistant prostate cancer (mCRPC). Tissue- or cell-based in situ detection of AR-V7, however, has been limited by lack of specificity.

Objective: To address current limitations in precision measurement of AR-V7 by developing a novel junction-specific AR-V7 RNA in situ hybridization (RISH) assay compatible with automated quantification.

Design, setting, and participants: We designed a RISH method to visualize single splice junctions in cells and tissue. Using the validated assay for junction-specific detection of the full-length AR (AR-FL) and AR-V7, we generated quantitative data, blinded to clinical data, for 63 prostate tumor biopsies.

Outcome measurements and statistical analysis: We evaluated clinical correlates of AR-FL/AR-V7 measurements, including association with prostate-specific antigen progression-free survival (PSA-PFS) and clinical and radiographic progression-free survival (PFS), in a subset of patients starting treatment with abiraterone or enzalutamide following biopsy.

Results and limitations: Quantitative AR-FL/AR-V7 data were generated from 56 of the 63 (88.9%) biopsy specimens examined, of which 44 were mCRPC biopsies. Positive AR-V7 signals were detected in 34.1% (15/44) mCRPC specimens, all of which also co-expressed AR-FL. The median AR-V7/AR-FL ratio was 11.9% (range 2.7-30.3%). Positive detection of AR-V7 was correlated with indicators of high disease burden at baseline. Among the 25 CRPC biopsies collected before treatment with abiraterone or enzalutamide, positive AR-V7 detection, but not higher AR-FL, was significantly associated with shorter PSA-PFS (hazard ratio 2.789, 95% confidence interval 1.12-6.95; p=0.0081).

Conclusions: We report for the first time a RISH method for highly specific and quantifiable detection of splice junctions, allowing further characterization of AR-V7 and its clinical significance.

Patient summary: Higher AR-V7 levels detected and quantified using a novel method were associated with poorer response to abiraterone or enzalutamide in prostate cancer.

Keywords: AR-V7; Androgen receptor; RNA in situ hybridization; Splice variant.

Publication types

Comparative Study
Multicenter Study
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Aged
Androgen Antagonists / therapeutic use*
Biopsy, Needle
Disease-Free Survival
Humans
Immunohistochemistry
In Situ Hybridization / methods
Logistic Models
Male
Middle Aged
Multivariate Analysis
Neoplasm Invasiveness / pathology
Neoplasm Metastasis
Neoplasm Staging
Prognosis
Prostatic Neoplasms, Castration-Resistant / drug therapy*
Prostatic Neoplasms, Castration-Resistant / genetics*
Prostatic Neoplasms, Castration-Resistant / mortality
Prostatic Neoplasms, Castration-Resistant / pathology
Protein Isoforms / genetics*
Receptors, Androgen / genetics*
Survival Analysis

Substances

Androgen Antagonists
Protein Isoforms
Receptors, Androgen

Abstract

Publication types

MeSH terms

Substances

Grants and funding