Immunocytochemical assay for estrogen receptors applied to human prostatic tumors

An immunocytochemical assay using a monoclonal antibody to estrogen receptor was applied to frozen sections of 43 prostatic tumors. In addition, in 16 tumors the results of the immunocytochemical assay were compared with those obtained using an enzyme immunoassay for estrogen receptor, a tritiated ligand binding assay, and a histochemical procedure using fluorescein-labeled estradiol conjugates. Specimens from 14 patients with benign prostatic hyperplasia and 29 patients with prostatic carcinoma were analyzed in assays in which human breast carcinoma specimens of high, medium, low, or negative estrogen receptor content acted as controls. The intensity of nuclear staining and the percentage of stained cells in the breast sample controls correlated well with estrogen receptor content as determined by both the enzyme immunoassay and the tritiated ligand binding assay. None of the fixed, frozen sections from the 43 prostatic tumors exhibited nuclear staining of either the benign or the malignant epithelial cells or of the stromal components. Negative results were also obtained with the tritiated ligand binding assay. The majority of prostatic samples were negative when using the enzyme immunoassay but four specimens had a mean value of 6.2 fmol/mg protein which is just above the sensitivity of the assay. Using fluorescein-labeled estradiol conjugates both cytoplasmic and nuclear binding was observed in the prostatic samples which did not correlate with the results obtained by the other three procedures.