title: Prostate cancer biomarker profiles in urinary sediments and exosomes.
abstract: OBJECTIVE
  Urinary biomarker tests for diagnosing prostate cancer have gained considerable interest. Urine is a complex mixture that can be subfractionated. We evaluated 2 urinary fractions that contain nucleic acids, ie cell pellets and exosomes. The influence of digital rectal examination before urine collection was also studied and the prostate cancer specific biomarkers PCA3 and TMPRSS2-ERG were assayed.
  
  
  METHODS
  Urine samples were prospectively obtained before and after digital rectal examination from 30 men scheduled for prostate biopsy. Cell pellet and exosomes were isolated and used for biomarker analysis. Analytical and diagnostic performance was tested using the Student t-test and ROC curves.
  
  
  RESULTS
  Unlike the exosome fraction, urinary sediment gene expression analysis was compromised by amorphous precipitation in 10% of all specimens. Digital rectal examination resulted in increased mRNA levels in each fraction. This was particularly relevant for the exosomal fraction since after digital rectal examination the number of samples decreased in which cancer specific markers were below the analytical detection limit. Biomarker diagnostic performance was comparable to that in large clinical studies. In exosomes the biomarkers had to be normalized for prostate specific antigen mRNA while cell pellet absolute PCA3 levels had diagnostic value.
  
  
  CONCLUSIONS
  Exosomes have characteristics that enable them to serve as a stable substrate for biomarker analysis. Thus, digital rectal examination enhances the analytical performance of biomarker analysis in exosomes and cell pellets. The diagnostic performance of biomarkers in exosomes differs from that of cell pellets. Clinical usefulness must be prospectively assessed in larger clinical cohorts.
authors.affiliation: Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Siebren
authors.initials: S
authors.lastname: Dijkstra
authors.affiliation: Department of Urology, Academic Medical Center University Hospital, Amsterdam, The Netherlands.
authors.forename: Ingrid L
authors.initials: IL
authors.lastname: Birker
authors.affiliation: Department of Research and Development, NovioGendix, Nijmegen, The Netherlands.
authors.forename: Frank P
authors.initials: FP
authors.lastname: Smit
authors.affiliation: Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Gisele H J M
authors.initials: GH
authors.lastname: Leyten
authors.affiliation: Department of Urology, Academic Medical Center University Hospital, Amsterdam, The Netherlands.
authors.forename: Theo M
authors.initials: TM
authors.lastname: de Reijke
authors.affiliation: Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Inge M
authors.initials: IM
authors.lastname: van Oort
authors.affiliation: Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Peter F A
authors.initials: PF
authors.lastname: Mulders
authors.affiliation: Department of Research and Development, NovioGendix, Nijmegen, The Netherlands.
authors.forename: Sander A
authors.initials: SA
authors.lastname: Jannink
authors.affiliation: Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Research and Development, NovioGendix, Nijmegen, The Netherlands. Electronic address: jack.schalken@radboudumc.nl.
authors.forename: Jack A
authors.initials: JA
authors.lastname: Schalken
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000652:urine*; D055354:Exosomes; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000652:urine*; D016482:Urinalysis / Q000379:methods
chemical_list: D014408:Biomarkers, Tumor
keywords: biological markers; exosomes; gene expression; prostate; prostatic neoplasms