Estramustine-binding protein in carcinoma and benign hyperplasia of the human prostate

For the purpose of elucidating whether the biological characteristics of estramustine-binding protein (EMBP) are different in benign prostatic hypertrophy (BPH) and prostatic carcinoma (PC) and also to determine the clinical value of EMBP in the tissue, the EMBP concentration in 19 patients with BPH and 26 with untreated PC was measured by means of radioimmunoassay (RIA) using an antibody raised against EMBP obtained from the rat ventral prostate and compared simultaneously with the dihydrotestosterone (DHT) level in the same tissue. The level of serum prostate-specific antigen (PSA) was also measured in these patients. The EMBP concentration was significantly correlated with the tissue DHT level in BPH and well-differentiated PC (r = 0.745, p < 0.0001), whereas it did not correlate in moderately and poorly differentiated PC (r = -0.159, p = 0.542). By comparing well-differentiated PC with moderately and poorly differentiated PC, the EMBP concentration was significantly lower in the former than in the latter two conditions (p < 0.005) in spite of the highest tissue DHT level in well-differentiated PC. The ratio of the EMBP concentration to the DHT level in moderately and poorly differentiated PC was significantly higher when compared with that observed in either BPH or well-differentiated PC (p < 0.005, respectively). However, the level of serum PSA did not reflect the histological differentiation of PC. These results suggest that: (i) the correlation of the EMBP concentration to the DHT level changed with the progression of the histological grade, and (ii) the ratio of the EMBP concentration to the DHT level in the tissue is clinically valuable in elucidating the biological potential of individual tumors.