Estramustine-binding protein--a marker for effect of therapy in prostatic carcinoma?

Estramustine-binding protein (EMBP) in human prostatic cancer before and after androgen-deprivation therapy was determined with an immunohistochemical technique. Although a rabbit polyclonal antiserum raised against rat EMBP was used, all the prostatic tumours displayed positive staining for EMBP. Staining was found exclusively in the cytoplasm of the epithelium, whereas nuclei, fibromuscular stroma and, in general, also lumina were negative. The staining intensity was higher in moderately and poorly differentiated, than in well differentiated tumours. EMBP immunostaining intensity decreased markedly from pretreatment levels in patients with remission, but returned to these levels when relapse occurred despite androgen withdrawal. Altered EMBP staining intensity was evident as early as 10 days after start of therapy in responding patients. EMBP may therefore be a marker of therapeutic response in human prostatic cancer. Provided that immunohistochemical measurements can be performed on fine-needle aspirates, EMBP analysis may be a direct and early means for predictive distinction between responding and non-responding patients.