Estramustine-binding protein to dihydrotestosterone ratio in human prostatic carcinoma: a new marker for predicting disease progression.

Abstract

To elucidate the clinical significance of estramustine-binding protein (EMBP) in human prostatic carcinoma (PC) as an indicator for predicting disease progression. EMBP concentrations in prostate tissue samples taken from 35 patients with benign prostatic hyperplasia (BPH), 33 patients with prostatic carcinoma (PC) taken before treatment, and from nine patients with hormone-refractory PC (hr-PC) were measured by radioimmunoassay using an antibody raised against rat EMBP. The dihydrotestosterone (DHT), prostatic acid phosphatase (PAP), prostate-specific antigen (PSA) and zinc levels in the tissue were also measured. The EMBP concentration in well differentiated PC (W-PC) samples was no higher than in samples of BPH tissue, whereas concentrations in moderately differentiated PC (M-PC) and poorly differentiated PC (P-PC) were significantly higher (P < 0.01 and P < 0.005, respectively); the highest levels were those in tissue from hr-PC (P < 0.001). Levels of PAP, PSA and zinc were significantly lower in tissue from PC than from BPH, while the differences in levels between W-PC, M-PC and P-PC were not significant. The EMBP to DHT ratio in the tissue increased significantly from W-PC through M-PC to P-PC and was greatest in hr-PC tissue. Conversely, the PAP:DHT, PSA:DHT and zinc:DHT ratios did not correlate with the progress of histological grade. In addition, the pre-treatment EMBP:DHT and zinc:DHT ratios in 14 patients who developed hr-PC within 3 years after the administration of estramustine phosphate were significantly higher when compared with the remaining 19 patients (P < 0.001 and P = 0.0184, respectively), whereas the PAP:DHT and PSA:DHT ratios showed no significant difference between the groups. Moreover, patients with a high EMBP:DHT ratio (> or = 82) had a low progression-free probability compared to those with a lower ratio. The androgen-dependent property of EMBP tends to decline with the transformation of prostatic tissue into biologically more malignant disease. The tissue EMBP:DHT ratio before treatment may be a good indicator of the individual malignant potential of PCs.