Double-fluorescence image microscopy for quantitation of prostate-specific antigen in histologic sections of the prostate

BACKGROUND: Although the assessment of serum prostate-specific antigen (PSA) has become a powerful instrument in the diagnosis and for prognosis of prostate carcinoma, there are few quantitative studies of PSA in tissue sections. METHODS: We developed a technique using double-fluorescence image microscopy for quantifying immunohistochemical reactions in tissue sections. PSA was stained by Texas Red and the cellular DNA was counterstained with 4,6-diamidino-2-phenylindole, dihydrochloride (DAPI). The fluorescence of Texas Red and DAPI was quantified separately after subtraction of background and shading correction. The amount of PSA related to the amount of DNA in identical tissue parts was studied in archival specimens from patients with hyperplasia and prostate carcinoma. RESULTS: The amount of tissue PSA decreased with the increase in tumor grade, Gleason score, and the change from diploid to aneuploid. CONCLUSION: Double-fluorescence image microscopy is a valuable technique for obtaining quantitative information of cellular constituents. For standardization of immunochemical reactions in tissue sections, cellular DNA seems to be most appropriate.