Nuclear-specific AR-V7 protein localization is necessary to guide treatment selection in metastatic castration-resistant prostate cancer Journal Article

Authors: Scher, H. I.; Graf, R. P.; Schreiber, N. A.; McLaughlin, B.; Lu, D.; Louw, J.; Danila, D. C.; Dugan, L.; Johnson, A.; Heller, G.; Fleisher, M.; Dittamore, R.
Article Title: Nuclear-specific AR-V7 protein localization is necessary to guide treatment selection in metastatic castration-resistant prostate cancer
Abstract: Background Circulating tumor cells (CTCs) expressing AR-V7 protein localized to the nucleus (nuclear-specific) identify metastatic castration-resistant prostate cancer (mCRPC) patients with improved overall survival (OS) on taxane therapy relative to the androgen receptor signaling inhibitors (ARSi) abiraterone acetate, enzalutamide, and apalutamide. Objective To evaluate if expanding the positivity criteria to include both nuclear and cytoplasmic AR-V7 localization (“nuclear-agnostic”) identifies more patients who would benefit from a taxane over an ARSi. Design, setting, and participants The study used a cross-sectional cohort. Between December 2012 and March 2015, 193 pretherapy blood samples, 191 of which were evaluable, were collected and processed from 161 unique mCRPC patients before starting a new line of systemic therapy for disease progression at the Memorial Sloan Kettering Cancer Center. The association between two AR-V7 scoring criteria, post-therapy prostate-specific antigen (PSA) change (PTPC) and OS following ARSi or taxane treatment, was explored. One criterion required nuclear-specific AR-V7 localization, and the other required an AR-V7 signal but was agnostic to protein localization in CTCs. Outcome measurements and statistical analyses Correlation of AR-V7 status to PTPC and OS was investigated. Relationships with survival were analyzed using multivariable Cox regression and log-rank analyses. Results and limitations A total of 34 (18%) samples were AR-V7-positive using nuclear-specific criteria, and 56 (29%) were AR-V7-positive using nuclear-agnostic criteria. Following ARSi treatment, none of the 16 nuclear-specific AR-V7-positive samples and six of the 32 (19%) nuclear-agnostic AR-V7-positive samples had ≥50% PTPC at 12 weeks. The strongest baseline factor influencing OS was the interaction between the presence of nuclear-specific AR-V7-positive CTCs and treatment with a taxane (hazard ratio 0.24, 95% confidence interval 0.078–0.79; p = 0.019). This interaction was not significant when nuclear-agnostic criteria were used. Conclusions To reliably inform treatment selection using an AR-V7 protein biomarker in CTCs, nuclear-specific localization is required. Patient summary We analyzed outcomes for patients with metastatic castration-resistant prostate cancer on androgen receptor signaling inhibitors and standard chemotherapy. Patients with circulating tumor cells that had AR-V7 protein in the cellular nuclei were very likely to survive longer on taxane-based chemotherapy, and tests unable to distinguish where the protein is located in the cell are not as predictive of benefit. © 2016 European Association of Urology
Keywords: prostate cancer; circulating tumor cells; liquid biopsy; ar-v7
Journal Title: European Urology
Volume: 71
Issue: 6
ISSN: 0302-2838
Publisher: Elsevier Science, Inc.  
Date Published: 2017-06-01
Start Page: 874
End Page: 882
Language: English
DOI: 10.1016/j.eururo.2016.11.024
PROVIDER: scopus
PUBMED: 27979426
PMCID: PMC5401782
Notes: Article -- Export Date: 1 June 2017 -- Source: Scopus
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MSK Authors
  1. Glenn Heller
    295 Heller
  2. Martin Fleisher
    237 Fleisher
  3. Howard Scher
    817 Scher
  4. Daniel C Danila
    82 Danila
  5. Diane D Lu
    2 Lu