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. © 1994 Wiley‐Liss, Inc.