Immunohistochemical estrogen receptor demonstration in the prostate and prostate cancer

Immunohistochemical investigations of human prostate and human prostate cancer were performed using two different monoclonal antibodies for the demonstration of estrogen receptors (ER). One marked the nuclear estrogen receptor protein (ERICAR, Abbott Laboratories), whereas the other one marked an estrogen receptor-associated cytoplasmic protein (ER-D5 kit, Amersham Buchler). 12 transurethral resection specimens with benign prostatic hyperplasia and 10 prostatic carcinomas were investigated by ERICA. Only in 1 specimen was a focally ERICA-positive basal cell hyperplasia found. The ER-D5 kit yielded a constantly positive reaction of stromal cells, especially smooth muscle cells. Basal cell hyperplasia and squamous metaplasia, alterations which can occur during estrogen application, were always strongly ER-D5-positive. Eleven (13.4%) out of 82 prostate carcinomas were focally positive. The staining results with ER-D5 are in good accordance with biochemical estrogen receptor investigations which demonstrated the estrogen receptors especially in the fibromuscular stroma. Furthermore, the results show that therapeutically applied estrogens do not directly inhibit the growth of prostatic carcinoma, however, the effect is an indirect one by suppressing androgen synthesis of the testis. The different staining results with ER-D5 and ERICA can be explained by the low ER concentration of prostate, the concentration is evidently below the limits of detectability with ERICA.