Cathepsin D cytosolic assay and immunohistochemical quantification in human prostate tumors

We quantified cathepsin D by immunoradiometric assay (IRMA) and quantitative immunohistochemistry in fifteen human prostate cancers, seventeen BPH, and nine normal prostates. The cytosolic cathepsin D concentration was higher in prostatic carcinoma (mean: 31.5 pmol/mg cytosol proteins; range: 10.2-66.2) than in normal prostate (16.0 pmol/mg cytosol proteins; 7.2-25.5; P = 0.01). Prostatic hyperplasia showed intermediate values (20.2 pmol/mg cytosol proteins; 7.6-33.9). Immunostaining of cathepsin D and prostatic acid phosphatase on serial frozen sections of prostate tissues was only observed in glandular epithelial cells. Immunostaining was quantified by computer-assisted image analysis as an quantitative immuno-cytochemical score (QIC score) expressed in arbitrary units (A.U.). QIC scores for cathepsin D were dispersed and had a tendency to be higher in benign prostatic hyperplasia (mean: 178.3 A.U.; range: 95-297) compared to normal prostate (85.2 A.U.; 2-173 P < 0.01) and prostatic carcinoma (90.0 A.U.; 21-179 P = 0.0002). Prostatic cathepsin D levels in cytosols or immunostaining sections were independent of other clinicobiological parameters.