Identification of a Novel Proteoform of Prostate Specific Antigen (SNP-L132I) in Clinical Samples by Multiple Reaction Monitoring.
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Prostate specific antigen (PSA) is a well-established tumor marker, which is frequently employed as model biomarker to develop and evaluate emerging quantitative proteomics techniques, partially due to wide access to commercialized immunoassays serving as "gold standard". We designed a multiple reaction monitoring (MRM) assay to detect PSA proteoforms in clinical samples (n=72), utilizing specificity and sensitivity of the method. We report for the first time, a PSA proteoform, coded by SNP-L132I (rs2003783), observed in 9 samples in both heterozygous (n=7) and homozygous (n=2) expression profiles. Other isoforms of PSA, derived from protein databases, were not identified by four unique proteotypic tryptic peptides. We have also utilized our MRM assay for precise quantitative analysis of PSA concentrations in both seminal and blood plasma samples. The analytical performance was evaluated, providing close agreement between each quantitation based on three selected peptides (LSEPAELTDAVK, IVGGWECEK and SVILLGR) and a routinely used commercialized immunoassay. Additionally, we have disclosed that the peptide IVGGWECEK is shared with kallikrein-related peptidase 2 and therefore not unique for PSA. Hence, we propose to use another tryptic sequence (SVILLGR) for accurate MRM-quantification of PSA in clinical samples.
|Enheter & grupper|
Ämnesklassifikation (UKÄ) – OBLIGATORISK
|Tidskrift||Molecular & Cellular Proteomics|
|Status||Published - 2013|
|Peer review utförd||Ja|
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