Glycoprotein A-80 in the human prostate: immunolocalization in prostatic intraepithelial neoplasia, carcinoma, radiation failure, and after neoadjuvant hormonal therapy.

Objectives: To review the expression of A-80 in prostate cancer and prostatic intraepithelial neoplasia and compare it with that of normal and hyperplastic prostatic tissue. The ability to recognize cancer after androgen deprivation therapy and residual and/or recurrent cancer after radiotherapy using A-80 staining was also examined. A-80 is a glycoprotein linked to exocrine differentiation that shows little or no expression in normal exocrine cells, but is selectively overexpressed in dysplasias and adenocarcinomas.

Methods: We studied 277 prostate samples with a monoclonal antibody (MAb) to A-80. We applied this MAb to paraffin sections of specimens of fetal (n = 12), benign prostatic hyperplasia (n = 26, from transurethral prostate resection specimens), atypical adenomatous hyperplasia (n = 11), prostate cancer (n = 103, from radical prostatectomy specimens), and autopsy (n = 7) tissue. In addition, 54 prostatectomy specimens after androgen-deprivation therapy and 64 specimens after radiotherapy were similarly studied.

Results: MAb A-80 stained the epithelial component of all 12 prostate specimens from fetal tissue; no staining was seen in normal adult prostatic tissue (0 of 7). In benign prostatic hyperplasia, sporadic cells reacted in 13% of cases (4 of 30); the atypical adenomatous hyperplasia samples were all negative (0 of 11). In patients with prostate cancer, more than 99% (102 of 103) stained positive, regardless of the grade or stage of cancer. Low and high-grade prostatic intraepithelial neoplasia reacted in 73% (38 of 52) and 92% (77 of 84) of cases, respectively. All 64 (100%) salvage prostatectomy samples after external beam radiotherapy stained positive for A-80. Carcinoma subsequent to neoadjuvant hormonal therapy stained positive in 98% (53 of 54) of cases.

Conclusions: A-80 is useful in differentiating benign prostatic hyperplasia and atypical adenomatous hyperplasia from prostate cancer. Also, the strong A-80 reactions in most high-grade prostatic intraepithelial neoplasia provide strong molecular support to the precancerous nature of the lesion. In particular, A-80 staining of biopsies may be useful in detecting residual and/or recurrent prostate carcinoma after radiation or hormonal therapy.