Proteomic analysis of voided urine after prostatic massage from patients with prostate cancer: a pilot study

OBJECTIVES: Serum prostate-specific antigen measurements are widely used for the early detection of prostate cancer but lack specificity, thus warranting the search for additional biomarkers. METHODS: Two-dimensional gel electrophoresis followed by matrix-assisted laser desorption ionization-time of flight-mass spectroscopy (MALDI-TOF-MS) analysis was used to investigate the protein profiles of voided urine after prostatic massage from 6 patients with histologically confirmed prostate cancer and 6 age-matched patients with benign prostatic hyperplasia. RESULTS: The median number of protein spots per gel was lower in the urine from the patients with cancer (median 143 spots, range 118 to 163) than in the urine from those with benign prostatic hyperplasia (median 154 spots, range 142 to 209), although the difference was not statistically significant. MALDI-TOF-MS analysis identified six commonly expressed proteins: alpha-enolase, isocitrate dehydrogenase, beta-2-microglobulin, alpha-1-microglobulin, complex-forming glycoprotein HC, and PRO2044. Of the five protein spots seen in a subset of patients with cancer, one was identified as calgranulin B/MRP-14. Immunohistochemical staining of prostatic tissue showed greater expression of calgranulin B/MRP-14 in 2 of 7 well-differentiated, 1 of 12 moderately differentiated, and 0 of 8 poorly differentiated tumors relative to adjacent benign tissue; expression of calgranulin A/MRP-8, a heterodermic binding partner of calgranulin B/MRP-14, was absent. CONCLUSIONS: The role of urinary calgranulin B/MRP-14 as a potential novel marker for prostate cancer needs additional investigation.