title: Relative quantitation of proteins in expressed prostatic secretion with a stable isotope labeled secretome standard.
abstract: Expressed prostatic secretion (EPS) is a proximal fluid directly derived from the prostate and, in the case of prostate cancer (PCa), is hypothesized to contain a repertoire of cancer-relevant proteins. Quantitative analysis of the EPS proteome may enable identification of proteins with utility for PCa diagnosis and prognosis. The present investigation demonstrates selective quantitation of proteins in EPS samples from PCa patients using a stable isotope labeled proteome standard (SILAP) generated through the selective harvest of the "secretome" from the PC3 prostate cancer cell line grown in stable isotope labeled cell culture medium. This stable isotope labeled secretome was digested with trypsin and equivalently added to each EPS digest, after which the resultant mixtures were analyzed by liquid chromatography-tandem mass spectrometry for peptide identification and quantification. Relative quantification of endogenous EPS peptides was accomplished by comparison of reconstructed mass chromatograms to those of the chemically identical SILAP peptides. A total of 86 proteins were quantified from 263 peptides in all of the EPS samples, 38 of which were found to be relevant to PCa. This work demonstrates the feasibility of using a SILAP secretome standard to simultaneously quantify many PCa-relevant proteins in EPS samples.
authors.affiliation: Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhao
authors.forename: Xuemei
authors.initials: X
authors.lastname: Zeng
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Bateman
authors.forename: Mai
authors.initials: M
authors.lastname: Sun
authors.forename: Pang-Ning
authors.initials: PN
authors.lastname: Teng
authors.forename: William L
authors.initials: WL
authors.lastname: Bigbee
authors.forename: Rajiv
authors.initials: R
authors.lastname: Dhir
authors.forename: Joel B
authors.initials: JB
authors.lastname: Nelson
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Conrads
authors.forename: Brian L
authors.initials: BL
authors.lastname: Hood
mesh_terms: D000595:Amino Acid Sequence; D012634:Bodily Secretions / Q000737:chemistry; D045744:Cell Line, Tumor; D006801:Humans; D007553:Isotope Labeling / Q000379:methods*; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism; D011467:Prostate / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism*; D060066:Protein Interaction Maps; D011506:Proteins / Q000032:analysis* / Q000145:classification; D020543:Proteome / Q000032:analysis / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D012015:Reference Standards
chemical_list: D010446:Peptide Fragments; D011506:Proteins; D020543:Proteome