Molecular microheterogeneity of prostate specific antigen in seminal fluid by mass spectrometry

ObjectivesProstate specific antigen (PSA) is a widely used and clinically valuable marker for prostate disease. In order to enable the development of new PSA assays and progress the understanding of the biology of PSA we have analyzed PSA in seminal plasma.Design and methodsPSA in seminal plasma from men attending a fertility clinic and healthy controls was analyzed using SDS-PAGE, Western blotting and mass spectrometry.ResultsUsing mass spectrometry, different forms of PSA could be identified in 1–9 bands seen on SDS-PAGE analysis of the respective sample. However, a majority of these molecular forms of PSA were not observed on Western blots. Enzymatic activity of PSA isoforms was demonstrated by sequencing data in zymogram gels. Multivariate analysis of clinical data revealed well-separated patient groups.ConclusionsWe demonstrated that PSA in seminal plasma occurs in several isoforms, yet not all were detectable using an antibody based clinical routine method. The heterogeneity of PSA expression might be of clinical significance, by an improved patient phenotyping.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We employed multiple proteomic platforms to characterize molecular forms of PSA in seminal plasma. ► Several molecular forms of PSA were identified by sequencing, some of which were hidden for 2E9 mAb. ► We demonstrated that high resolution FT-ICR MS is useful to identify enzymatically active PSA forms. ► Multivariate analysis of clinical data revealed patient groups well separated. ► Samples with male factor infertility were annotated with high peptide numbers of the major PSA form.