Analysis of subforms of free prostate-specific antigen in serum by two-dimensional gel electrophoresis: potential to improve diagnosis of prostate cancer.
BACKGROUND
The aim of this study was to develop a method to separate and quantify subforms of free prostate-specific antigen (fPSA) in serum by two-dimensional electrophoresis and to assess the diagnostic accuracy of these subforms for prostate cancer (PCa) diagnosis in comparison with total PSA (tPSA) and the ratio of fPSA to tPSA (%fPSA).


METHODS
Sera from 50 patients with and without PCa, respectively, were studied. PSA was isolated by immunoadsorption on streptavidin-coated magnetic beads with biotinylated anti-PSA antibodies and separated by two-dimensional electrophoresis. After semidry blotting, the intensities of the fPSA spots were quantified by chemiluminescence using an imager analyzer.


RESULTS
The method detected subforms to a concentration of 0.1 mug/L fPSA with an imprecision (CV) <16%. We detected 15 immunoreactive fPSA spots of different intensities. Spots F2 and F3 were present in all samples. F2 was lower in samples from non-PCa patients (median, 23%) than in samples from PCa patients (49%), whereas F3 behaved inversely (non-PCa, 73%; PCa, 45%). Ratios of F2 to F3 and F2/F3 to %fPSA, respectively, showed improved diagnostic accuracy compared with tPSA and %fPSA. Better differentiation by F2/F3 or by F2/F3 to %fPSA was particularly evident in patients with %fPSA values >15%. There were no associations between the PCa grading scale and fPSA subforms.


CONCLUSIONS
fPSA subforms separated by two-dimensional electrophoresis may improve both sensitivity and specificity in prostate cancer diagnostics compared with tPSA and %fPSA. The development of a practicable assay based on the immunologic properties of these different fPSA subforms seems to be promising.
Department of Urology, University Hospital Charité, Humboldt University, Berlin, Germany. klaus.jung@charite.de
Klaus
K
Jung
Janett
J
Reiche
Axel
A
Boehme
Carsten
C
Stephan
Stephan A
SA
Loening
Dietmar
D
Schnorr
Wolfgang
W
Hoesel
Pranav
P
Sinha
D000368:Aged; D001798:Blood Proteins / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000175:diagnosis; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D011485:Protein Binding; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D001798:Blood Proteins; D017430:Prostate-Specific Antigen