title: The Detection of Androgen Receptor Splice Variant 7 in Plasma-derived Exosomal RNA Strongly Predicts Resistance to Hormonal Therapy in Metastatic Prostate Cancer Patients.
abstract: The androgen receptor splice variant 7 (AR-V7) is associated with resistance to hormonal therapy in castration-resistant prostate cancer (CRPC). Due to limitations of the methods available for AR-V7 analysis, the identification of a reliable detection method may facilitate the use of this biomarker in clinical practice.
  
  
  
  To confirm AR-V7 as a predictor of resistance to hormonal therapy and develop a new approach to assess AR-V7 by highly sensitive digital droplet polymerase chain reaction (ddPCR) in plasma-derived exosomal RNA.
  
  
  
  Plasma samples were collected from 36 CRPC patients before they began second-line hormonal treatment. Exosomes were isolated and RNA extracted for analysis of AR-V7 by ddPCR.
  
  
  
  The absolute target gene concentration as copies per milliliter (copies/ml) was determined by ddPCR. Statistical analyses were performed with SPSS software (IBM Corp., Armonk, NY, USA).
  
  
  
  A total of 26 patients received abiraterone and 10 enzalutamide; 39% of patients were found to be AR-V7 positive (AR-V7+). Median progression-free survival was significantly longer in AR-V7 negative (AR-V7-) versus AR-V7+patients (20 vs 3 mo; p<0.001). Overall survival was significantly shorter in AR-V7+participants at baseline compared with AR-V7-participants (8 mo vs not reached; p<0.001).
  
  
  
  This study demonstrates that plasma-derived exosomal RNA is a reliable source of AR-V7 that can be detected sensitively by ddPCR assay. We also showed that resistance to hormonal therapy may be predicted by AR-V7, making it a clinically relevant biomarker.
  
  
  
  We report a first study on a method for androgen receptor splice variant 7 (AR-V7) detection in RNA extracted from cancer cell vesicles released in blood. Results confirmed the role of AR-V7 as a predictive biomarker of resistance to hormonal therapy. Our assay showed that vesicles are a reliable source of AR-V7 RNA and that the method is fast, highly sensitive, and affordable.
authors.affiliation: Clinical Pharmacology and Pharmacogenetics Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy. Electronic address: marzia.delre@gmail.com.
authors.forename: Marzia
authors.initials: M
authors.lastname: Del Re
authors.affiliation: Medical Oncology Unit, Department of Translational Research and New Technologies in Medicine, University of Pisa, Pisa, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Biasco
authors.affiliation: Clinical Pharmacology and Pharmacogenetics Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Crucitta
authors.affiliation: Medical Oncology Unit, Department of Translational Research and New Technologies in Medicine, University of Pisa, Pisa, Italy.
authors.forename: Lisa
authors.initials: L
authors.lastname: Derosa
authors.affiliation: Clinical Pharmacology and Pharmacogenetics Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Rofi
authors.affiliation: Medical Oncology Unit, Department of Translational Research and New Technologies in Medicine, University of Pisa, Pisa, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Orlandini
authors.affiliation: Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Miccoli
authors.affiliation: Medical Oncology Unit, Department of Translational Research and New Technologies in Medicine, University of Pisa, Pisa, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Galli
authors.affiliation: Medical Oncology Unit, Department of Translational Research and New Technologies in Medicine, University of Pisa, Pisa, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Falcone
authors.affiliation: Department of Urology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Guido W
authors.initials: GW
authors.lastname: Jenster
authors.affiliation: Department of Clinical Chemistry, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Ron H
authors.initials: RH
authors.lastname: van Schaik
authors.affiliation: Clinical Pharmacology and Pharmacogenetics Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Romano
authors.initials: R
authors.lastname: Danesi
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000556:secondary; D000368:Aged; D000369:Aged, 80 and over; D000736:Androstenes / Q000627:therapeutic use; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D001549:Benzamides; D018572:Disease-Free Survival; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009570:Nitriles; D010669:Phenylthiohydantoin / Q000031:analogs & derivatives / Q000627:therapeutic use; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020033:Protein Isoforms / Q000235:genetics; D012313:RNA / Q000097:blood; D011944:Receptors, Androgen / Q000235:genetics* / Q000378:metabolism
chemical_list: D000736:Androstenes; D018931:Antineoplastic Agents, Hormonal; D001549:Benzamides; D009570:Nitriles; D020033:Protein Isoforms; D011944:Receptors, Androgen; D010669:Phenylthiohydantoin; D012313:RNA; C540278:enzalutamide; C089740:abiraterone
keywords: AR-V7; Digital droplet PCR; Exosomes; Hormonal therapy; Pharmacogenetics; Prostate cancer; Resistance