Study of estramustine binding protein (EMBP): purification of rat EMBP and establishment of RIA

Clinical study on estramustine binding protein (EMBP) in human prostate

To elucidate the characteristics of estramustine binding protein (EMBP) in human prostate, tissue EMBP concentration was examined in 42 benign prostatic hypertrophy (BPH), 34 untreated prostatic carcinoma (PC), 8 hormone refractory PC (hr-PC), as well as 13 control prostate human tissue samples by RIA using rat-EMBP antibody, and the concentration thus obtained was compared with dihydrotestosterone (DHT), prostatic acid phosphatase (PAP), prostate-specific antigen (PSA), and zinc, indices exhibiting androgen dependency in the prostate. EMBP concentration correlated significantly with DHT and PSA levels in the control prostate and BPH, but not in untreated PC. In BPH, EMBP concentration increased significantly after administration of fluoxymesterone (4 mg/day for 2 weeks), whereas it decreased significantly after estramustine phosphate (280 mg/day for 2 weeks). The EMBP/DHT ratio in moderately and poorly differentiated, and the hr-PC was significantly higher than in controls, BPH, and well-differentiated PC. In addition, untreated PC with an EMBP/DHT ratio of more than 40 showed significantly lower progression-free probability as compared with PC with an EMBP/DHT of less than 40. These results suggest that (1) EMBP in BPH and well-differentiated PC preserves androgen dependency, but not in moderately and poorly differentiated, nor in hr-PCs, indicating that EMBP is a protein different from PAP and PSA, and (2) that the tissue EMBP/DHT ratio might be useful as a marker for predicting disease progression.

Purification of estramustine-binding protein and production of monoclonal antibodies to its different components

Estramustine-binding protein (EMBP) is a heterodimeric 46-kDa glycoprotein that is secreted from the prostate. Upon reductive cleavage it decomposes into two closely related components, C1 and C2, and the shared glycosylated peptide C3. EMBP binds estramustine and estromustine, the active metabolites of estramustine phosphate (Estracyt), which is a drug with antimitotic properties used in the treatment of prostatic carcinoma. In the present study, a two-step procedure (i.e., anion-exchange and Con A-Sepharose chromatography) is described for the isolation of EMBP in high yield from rat prostate tissue. Mouse monoclonal antibodies (mAbs) were produced using the major DEAE-Sepharose fraction of EMBP as an immunogen. Eleven mAbs were selected by screening in a solid-phase ELISA. One displayed high-affinity binding with soluble EMBP (Ka approximately 3 x 10(10) M-1) and crossreacted with a human prostate tumor extract in a radioimmunoassay. The epitopes defined by these mAbs were analyzed by Western immunoblotting. All constituents of EMBP, except component C1, were identified by at least one antibody. Nine visualized either one or both of the two EMBP subunits under denaturing conditions, two of which retained their reactivity after reduction of disulfide bridges. One epitope was exposed to its mAb only when the antigen was in its reduced state. The immunoreactivity was eliminated by protease treatment, whereas deglycosylation with glycopeptidase F had a minimal effect. EMBP has been detected in tissues other than the prostate as well as in prostate neoplastic specimens and in several other human malignancies. Hence, these mAbs will be a useful tool in the characterization of EMBP in different tissues and in evaluating existing and in defining new indications for Estracyt therapy.

Electrophoretic modification of sperm plasma membrane by ventral prostate secretion in golden hamsters

Plasma membrane proteins were extracted either from epididymal spermatozoa after incubation with ventral prostate gland secretion or from spermatozoa recovered from uteri of females mated with surgically treated males belonging to the following groups: TX (excision of all accessory sex glands, ASG), VPX (bilateral excision of ventral prostate), VP (bilateral excision of all ASG except the ventral prostate), and SH (sham-operated). Incubation of spermatozoa with ventral prostatic secretion resulted in an 11-fold increase in glycoprotein content of the plasma membrane, but total protein concentration remained unchanged. The in vivo study indicated that interactions of ASG secretions and spermatozoa were complicated by the presence of uterine secretions. Glycoprotein content was reduced in the presence of ventral prostatic secretions. SDS-PAGE profiles showed that both uterine and ASG secretions could modify proteins on the sperm surface. Enrichment of a 25-kD subunit was apparently effected by uterine secretions and further promoted by combined secretions of the ampullary gland, coagulating gland, dorsolateral prostate, and seminal vesicle, but was reduced by the ventral prostate. A number of other protein subunits appeared to be specifically modified by the ventral prostate, while other ASG secretions were also shown to alter the effects of the ventral prostate on the sperm surface.

Immunoreactive protein to rat estramustine binding protein in human seminal plasma: its relationship to prostatic acid phosphatase and zinc

Immunoreactive estramustine binding protein in human seminal plasma obtained from 34 infertile men was measured by means of radioimmunoassay (RIA) using the antibody raised against EMBP obtained from ventral prostate of rat. The mean concentration of IR-EMBP in human seminal plasma measured by this RIA was 1.092 ng/ml, ranging 258 to 1.859 ng/ml. Both concentrations of prostatic acid phosphatase and zinc in human seminal plasma concurrently measured were statistically significantly negatively correlated with that of IR-EMBP. These results here obtained might reveal that IR-EMBP in human seminal plasma signify androgen status in low possibility.

Relationship of thyroid to estramustine binding protein (EMBP) concentration in rat prostate

Alternations of estramustine binding protein (EMBP) concentration in rat prostate in relation to androgen status under hypo- and hyperthyroid conditions was estimated by means of radioimmunoassay (RIA). In hyperthyroid rats, EMBP concentration in dorsal as well as in lateral prostate was not significantly changed, but significantly reduced in ventral prostate (P less than 0.01). Ventral tissue concentration of testosterone(T) + dihydrotestosterone (DHT), DHT and T, and the ventral tissue ratio of DHT to T + DHT were not significantly changed in hypo- and hyper-thyroid conditions compared with that of the control. In hyperthyroid rats, serum T level and EMBP concentration in ventral prostate were significantly reduced in comparison to ones of the control (P less than 0.05 and P less than 0.01, respectively), however, the ratio of ventral tissue (T + DHT) to serum T was significantly increased (P less than 0.05). Moreover, in contrast to the control, EMBP concentration expressed as microgram/microgram ventral DNA was significantly reduced in hyperthyroid rats (P less than 0.05). On the other hand, in hypothyroid rats, change of EMBP concentration in ventral prostate in relation to androgen status was not significant in comparison to the control. The results here obtained revealed that EMBP concentration in ventral prostate under hyperthyroid condition would be affected by (a) a modulation of endogenous androgen-dependency in EMBP synthesis or by (b) a reduction of cell numbers responsible for EMBP synthesis.