Quantitation of serum prostate-specific membrane antigen by a novel protein biochip immunoassay discriminates benign from malignant prostate disease

The lack of a sensitive immunoassay for quantitating serum prostate-specifi c membrane antigen (PSMA) hinders its clinical utility as a diagnostic/prog nostic biomarker. An innovative protein biochip immunoassay was used to qua ntitate and compare serum PSMA levels in healthy men and patients with eith er benign or malignant prostate disease. PSMA was captured from serum by an ti-PSMA antibody bound to ProteinChip arrays, the captured PSMA detected by surface-enhanced laser desorption/ionization mass spectrometry, and quanti tated by comparing the mass signal integrals to a standard curve establishe d using purified recombinant PSMA. The average serum PSMA value for prostat e cancer (623.1 ng/ml) was significantly different (P < 0.001) front that f or benign prostate hyperplasia (117.1 ng/ml) and the normal groups (age < 5 0, 272.9 ng/ml; age > 50, 359.4 ng/ml). These initial results suggest that serum PSMA may be a more effective biomarker than prostate-specific antigen for differentiating benign from malignant prostate disease and warrants ad ditional evaluation of the surface-enhanced laser desorption/ionization PSM A immunoassay to determine its diagnostic utility.