Heterogeneity of steroid binding sites in prostatic carcinoma: morphological demonstration and clinical implications

Prostatic neoplasms were studied for estrogen binding using four methods. Two employed fluorescent estrogen histochemical ligands, one was a new immunocytochemical technique using specific monoclonal antibodies to human estrophilin, and the last procedure was conventional biochemical dextran-coated charcoal assay. Results indicated that the fluorescent ligands recognized closely associated but separate estrogen-binding sites (putative type II sites) which in turn differed from the binding site measured biochemically. Studies with the monoclonal antibodies were nearly always negative, suggesting that prostatic estrogen receptor might vary antigenically from that present in breast and endometrium. Histochemical and biochemical androgen-binding studies were also compared and showed a close association. In the prediction of hormonal response in advanced prostate cancer both showed high sensitivity and low specificity. The addition of estrogen-binding data did not improve the predictive value of the androgen-binding histochemical assay. However, combining results of the biochemical and histochemical androgen-binding assays resulted in significant improvement of the specificity without loss of sensitivity, suggesting that there is a degree of positive interaction between the binding sites assayed by the two methods.