title: Proteomic profiling of exosomes leads to the identification of novel biomarkers for prostate cancer.
abstract: BACKGROUND
  Current markers for prostate cancer, such as PSA lack specificity. Therefore, novel biomarkers are needed. Unfortunately, the complexity of body fluids often hampers biomarker discovery. An attractive alternative approach is the isolation of small vesicles, i.e. exosomes, ∼100 nm, which contain proteins that are specific to the tissue from which they are derived and therefore can be considered as treasure chests for disease-specific biomarker discovery.
  
  
  METHODS
  Exosomes were isolated from 2 immortalized primary prostate epithelial cells (PNT2C2 and RWPE-1) and 2 PCa cell lines (PC346C and VCaP) by ultracentrifugation. After tryptic digestion, proteomic analyses utilized a nanoLC coupled with an LTQ-Orbitrap operated in tandem MS (MS/MS) mode. Accurate Mass and Time (AMT) tag approach was employed for peptide identification and quantitation. Candidate biomarkers were validated by Western blotting and Immunohistochemistry.
  
  
  RESULTS
  Proteomic characterization resulted in the identification of 248, 233, 169, and 216 proteins by at least 2 peptides in exosomes from PNT2C2, RWPE-1, PC346C, and VCaP, respectively. Statistical analyses revealed 52 proteins differently abundant between PCa and control cells, 9 of which were more abundant in PCa. Validation by Western blotting confirmed a higher abundance of FASN, XPO1 and PDCD6IP (ALIX) in PCa exosomes.
  
  
  CONCLUSIONS
  Identification of exosomal proteins using high performance LC-FTMS resulted in the discovery of PDCD6IP, FASN, XPO1 and ENO1 as new candidate biomarkers for prostate cancer.
authors.affiliation: Department of Urology, Erasmus Medical Center, Rotterdam, Netherlands.
authors.forename: Diederick
authors.initials: D
authors.lastname: Duijvesz
authors.affiliation: Fundamental and Computational Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Burnum-Johnson
authors.affiliation: Fundamental and Computational Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
authors.forename: Marina A
authors.initials: MA
authors.lastname: Gritsenko
authors.affiliation: Department of Pathology, Erasmus Medical Center, Rotterdam, Netherlands.
authors.forename: A Marije
authors.initials: AM
authors.lastname: Hoogland
authors.affiliation: Department of Urology, Erasmus Medical Center, Rotterdam, Netherlands.
authors.forename: Mirella S
authors.initials: MS
authors.lastname: Vredenbregt-van den Berg
authors.affiliation: Department of Genetics, Erasmus Medical Center, Rotterdam, Netherlands.
authors.forename: Rob
authors.initials: R
authors.lastname: Willemsen
authors.affiliation: Department of Neurology, Erasmus Medical Center, Rotterdam, Netherlands.
authors.forename: Theo
authors.initials: T
authors.lastname: Luider
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Paša-Tolić
authors.affiliation: Department of Urology, Erasmus Medical Center, Rotterdam, Netherlands.
authors.forename: Guido
authors.initials: G
authors.lastname: Jenster
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism / Q000648:ultrastructure; D054890:Fatty Acid Synthase, Type I / Q000378:metabolism; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D008297:Male; D046529:Microscopy, Electron, Transmission; D009363:Neoplasm Proteins / Q000378:metabolism*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000648:ultrastructure; D040901:Proteomics / Q000379:methods; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D053719:Tandem Mass Spectrometry; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D000097606:Exportin 1 Protein
chemical_list: D014408:Biomarkers, Tumor; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D054890:Fatty Acid Synthase, Type I; D028884:Karyopherins; D009363:Neoplasm Proteins; D010751:Phosphopyruvate Hydratase; D018160:Receptors, Cytoplasmic and Nuclear; D025521:Tumor Suppressor Proteins; D000097606:Exportin 1 Protein; C117020:PDCD6IP protein, human; C518729:FASN protein, human; C095157:ENO1 protein, human