Immunocytochemical detection of prostate specific antigen expression in human breast carcinoma cells.

To date, no true tissue specific antigen has been discovered. Prostate-specific antigen (PSA) was initially reported to be a tissue specific protein, detected in the seminal fluid and produced by normal and abnormal epithelial cells of the prostate gland. PSA is a 33 kD glycoprotein, with serine protease activity, and it is produced by several different tissues in the human body. Its expression levels may be elevated during benign and neoplastic cell growth in the prostate, and in a number of other human malignancies. The detection of PSA is also useful in monitoring the efficacy of anticancer treatment in malignant prostatic adenocarcinoma. In the present immunocytochemical study, PSA expression was examined employing a biotin-streptavidin based, alkaline phosphatase conjugated antigen detection technique in 16 routine, neutral formalin fixed, paraffin-wax embedded, primary BC tissue sections. Human postnatal thymic tissue, among others, was used as a negative tissue control, while normal prostate and prostate carcinomas (PCs) were included in the collection of antigen positive tissues. We observed the presence of PSA in all 16 BC cases, and this expression was independent of estrogen receptor status. The intensity of the staining was moderate to high (B to A) and localized to 20% to 40% of the total BC cell population, with cells of similar immunoreactivity being clustered in groups within the tumor microenvironment. This result directly contradicts the previous opinion concerning the prostate epithelium specificity of PSA expression and production. The immunophenotype (IP) heterogeneity of BC cells is further substantiated by their PSA positivity and its association with the presence of steroid hormone receptors. The establishment of the clinical significance of these findings necessitates further in vivo and in vitro research in BCs. The prognostic significance of PSA in BCs may lie in the identification of a subset of estrogen receptor negative BC patients who have malignancies associated with a good prognosis. PSA related, novel antineoplastic immunotherapy may also be recommended.