Immunolocalization of glycoprotein A-80 in prostatic carcinoma and prostatic intraepithelial neoplasia

A-80 is a mucin-like glycoprotein associated with exocrine differentiation that shows little or no expression in normal exocrine cells and typical adenomas, but is upregulated in dysplasia and adenocarcinoma of certain organs. Its expression has not been systematically examined in prostatic adenocarcinoma and its putative precursor, prostatic intraepithelial neoplasia (PIN). The authors applied a mouse monoclonal antibody against A-80 in paraffin-embedded sections from 103 cases of prostatic carcinoma, 26 cases of nodular hyperplasia, 7 autopsy samples from normal young adult prostates, and 12 fetal prostates. All but one cancer reacted, although expression was heterogeneous; 75 of 103 stained extensively (> 3+ on a 0 to 5+ scale) and strongly. Staining extent and intensity were independent of tumor grade, and tended to be strong even when focal. Seventy-seven of 84 foci (92%) of high-grade PIN and 38 of 52 foci (73%) of low-grade PIN stained for A-80; reactions were most extensive and intense in high grade PIN. Only 5 of 26 cases (19%) of hyperplasia reacted, and this consisted of weak to moderate staining in sporadic cells; the remainder were negative. Normal adult prostatic epithelium did not express A-80 except for weak and inconsistent staining in foci of inflammation and infarction; atrophic glands were negative. Fetal prostate showed focally strong reactivity. These results indicate that A-80 is selectively expressed in most cases of intraepithelial neoplasia and prostate cancer, but is usually absent in benign and hyperplastic epithelium. The upregulation of glycoprotein A-80 in PIN and adenocarcinoma parallels observations in other organs, such as the breast and colon, suggesting that this is a significant oncodevelopmental molecule with potential clinical applications.