title: Identification of differentially expressed proteins in direct expressed prostatic secretions of men with organ-confined versus extracapsular prostate cancer.
abstract: Current protocols for the screening of prostate cancer cannot accurately discriminate clinically indolent tumors from more aggressive ones. One reliable indicator of outcome has been the determination of organ-confined versus nonorgan-confined disease but even this determination is often only made following prostatectomy. This underscores the need to explore alternate avenues to enhance outcome prediction of prostate cancer patients. Fluids that are proximal to the prostate, such as expressed prostatic secretions (EPS), are attractive sources of potential prostate cancer biomarkers as these fluids likely bathe the tumor. Direct-EPS samples from 16 individuals with extracapsular (n = 8) or organ-confined (n = 8) prostate cancer were used as a discovery cohort, and were analyzed in duplicate by a nine-step MudPIT on a LTQ-Orbitrap XL mass spectrometer. A total of 624 unique proteins were identified by at least two unique peptides with a 0.2% false discovery rate. A semiquantitative spectral counting algorithm identified 133 significantly differentially expressed proteins in the discovery cohort. Integrative data mining prioritized 14 candidates, including two known prostate cancer biomarkers: prostate-specific antigen and prostatic acid phosphatase, which were significantly elevated in the direct-EPS from the organ-confined cancer group. These and five other candidates (SFN, MME, PARK7, TIMP1, and TGM4) were verified by Western blotting in an independent set of direct-EPS from patients with biochemically recurrent disease (n = 5) versus patients with no evidence of recurrence upon follow-up (n = 10). Lastly, we performed proof-of-concept SRM-MS-based relative quantification of the five candidates using unpurified heavy isotope-labeled synthetic peptides spiked into pools of EPS-urines from men with extracapsular and organ-confined prostate tumors. This study represents the first efforts to define the direct-EPS proteome from two major subclasses of prostate cancer using shotgun proteomics and verification in EPS-urine by SRM-MS.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Canada.
authors.forename: Yunee
authors.initials: Y
authors.lastname: Kim
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ignatchenko
authors.forename: Cindy Q
authors.initials: CQ
authors.lastname: Yao
authors.forename: Irina
authors.initials: I
authors.lastname: Kalatskaya
authors.forename: Julius O
authors.initials: JO
authors.lastname: Nyalwidhe
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Lance
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Gramolini
authors.forename: Dean A
authors.initials: DA
authors.lastname: Troyer
authors.forename: Lincoln D
authors.initials: LD
authors.lastname: Stein
authors.forename: Paul C
authors.initials: PC
authors.lastname: Boutros
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Medin
authors.forename: O John
authors.initials: OJ
authors.lastname: Semmes
authors.forename: Richard R
authors.initials: RR
authors.lastname: Drake
authors.forename: Thomas
authors.initials: T
authors.lastname: Kislinger
mesh_terms: D048948:14-3-3 Proteins / Q000032:analysis; D014408:Biomarkers, Tumor / Q000032:analysis / Q000378:metabolism; D005092:Exonucleases / Q000032:analysis; D005095:Exoribonucleases; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis; D007553:Isotope Labeling; D008297:Male; D015513:Oncogene Proteins / Q000032:analysis; D011467:Prostate / Q000378:metabolism*; D017430:Prostate-Specific Antigen / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism*; D029584:Prostatic Secretory Proteins / Q000032:analysis* / Q000652:urine*; D040081:Protein Array Analysis; D000071617:Protein Deglycase DJ-1; D020543:Proteome / Q000032:analysis; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000032:analysis; D011503:Transglutaminases / Q000032:analysis
chemical_list: D048948:14-3-3 Proteins; D014408:Biomarkers, Tumor; D047908:Intracellular Signaling Peptides and Proteins; D015513:Oncogene Proteins; D029584:Prostatic Secretory Proteins; D020543:Proteome; C560822:TIMP1 protein, human; D019715:Tissue Inhibitor of Metalloproteinase-1; C418702:transglutaminase 4; D011503:Transglutaminases; D005092:Exonucleases; D005095:Exoribonucleases; C413442:SFN protein, human; C105131:PARK7 protein, human; D000071617:Protein Deglycase DJ-1; D017430:Prostate-Specific Antigen