Characterization and stabilization of progesterone receptors in human benign prostatic hypertrophy

Androgen, estrogen, and progesterone receptors in normal and aging prostates

Testicular hormones regulate the growth and development of the prostate. The presence of androgen receptors in prostatic tissue and their importance in the normal development of the prostate has been established. Age-related changes in the hormonal milieu, and perhaps steroid hormone receptor profile, could set in motion pathological changes leading to the onset of benign prostatic hyperplasia (BPH) or prostate cancer which primarily affect older men. The accumulation of dihydrotestosterone with age, the reawakening of the inductive potential of the prostatic stroma, the altered rate of apoptosis with age, and the age-related changes in the ratio of testosterone:estrogen have all been implicated in the etiology of BPH. In addition to androgen receptors, several studies have documented the presence of estrogen and progesterone receptors in BPH and prostate cancer. So far, most studies have focussed on the correlation between the presence/absence of steroid hormone receptors and response to hormonal therapy. The molecular mechanisms by which these steroid hormone receptors regulate the onset or progression of BPH and prostate cancer are not yet clear. The chronological changes in the levels and distribution of steroid hormone receptors in normal prostatic tissue and the effect of such changes on the synthesis of growth factors, growth factor receptors, and oncogenes should be investigated.

Quantitation of cytosolic and nuclear estrogen and progesterone receptor in benign, untreated, and treated malignant human prostatic tissue by radioligand binding and enzyme-immunoassays

Estrogen receptor (ER) and progesterone receptor (PgR) were quantitated in benign and malignant human prostatic tissue by using radioligand binding assays (RBA) and enzyme-immunoassays (EIA). Using a hydroxylapatite exchange method for ER, little or no nuclear ER (ERN) could be detected, but with the EIA both cytosolic (ERC) and ERN were detected in almost all specimens, although in meager concentrations. Tissue from patients with carcinoma had significantly higher ERC concentrations than tissue from patients with benign disease. Specimens from estrogen-treated patients had significantly lower ERC:ERN ratios than those from untreated patients. Progesterone receptor was detected in virtually all specimens by both methods, at concentrations higher than those of ER. Carcinoma tissue with a high malignant involvement contained significantly less PgR than benign tissue. Using either method, the highest concentrations of PgR were observed in tissue from carcinoma patients treated with estrogen. Overall, the data suggest that although human prostatic tissue contains only modest amounts of ER, this is active in that treatment with estrogen promotes association of this receptor with the nuclear fraction and increases PgR content.

Immunohistochemical localization of progesterone receptor in benign and malignant human prostate

A monoclonal antibody to progesterone receptor, KD68, was used to localize this receptor protein in 31 surgical specimens of benign and malignant human prostate. Progesterone receptor was detected almost exclusively in stromal cells. The most striking finding was the periacinar arrangement of stained cells in some specimens of glandular BPH, sometimes associated with close apposition of stained cells to the basement membrane of the acinar epithelium. In both benign and malignant specimens scattered stained cells were observed in some areas of fibromuscular stroma. Except for occasional stained epithelial cells in one benign and one estrogen-treated malignant specimen, both benign and malignant epithelium were negative.

Analysis of the androgen binding in human benign prostatic hypertrophy

In order to delineate optimal conditions for the determination of androgen specific binding in human benign prostatic hypertrophy tissues (BPH), extracts of these tissues were prepared using buffers of different compositions. The binding of 5 alpha-dihydrotestosterone (DHT) and of methyltrienolone (R 1881) was analyzed using agar gel electrophoresis. This method allowed the detection of 3 different high affinity tissular binding peaks with similar specificity. Moreover, the inhibition by each of the competitors was also the same for both ligands. It could be demonstrated that none of the observed peaks resulted from the binding of 1 of the ligands to sex hormone binding globulin (SHBG) or to a progesterone receptor. Hypotheses about the possible origin of these peaks are discussed.

Effect of 16 beta-ethyl-17 beta-hydroxy-4-estren-3-one (TSAA-291) on the binding of promegestone (R5020) and methyltrienolone (R1881) to hyperplastic and neoplastic human prostate

The effect of a synthetic steroidal compound TSAA-291 (16 beta-ethyl-17 beta-hydroxy-4-estren-3-one) on the binding of methyltrienolone (R1881) and promegestone (R5020) to hyperplastic and neoplastic human prostate was investigated. TSAA-291 inhibits both androgen and progestogen binding to hyperplastic and neoplastic human prostate. Glycerol density gradient analysis revealed that the inhibition of promegestone (R5020) binding by TSAA-291 was significantly greater than that of methyltrienolone (R1881) in both hyperplastic and neoplastic human prostate. The nature of the inhibition was competitive as determined by Scatchard analysis and double reciprocal plots. Comparison of the Ki values for the inhibition by TSAA-291 of R1881 binding (3.2 X 10(-7) M) and of R5020 binding (2.0 X 10(-8) M) suggests that TSAA-291 binds to progesterone receptor with a greater affinity than to androgen receptor. Our results suggest that the effectiveness of the drug in the treatment of benign hyperplasia might be due not only to its anti-androgenic properties but also due to its ability to inhibit progesterone receptor.

A mini-column method for routine measurement of human prostatic androgen receptors

The complex heterogeneous nature of the human prostate gland is such that it is advisable to know the histological characteristics of each sample used for androgen receptor (AR) measurement. Adequate size of sample for AR determination is thus a problem if specimens provided during routine transurethral prostatectomy are to be used for both estimation of AR and histological examination. We present a simple method suitable for these small specimens in which [3H]R 1881 bound to AR is separated from free steroid on mini-columns of controlled-pore glass beads. Data obtained indicate a single class of binding sites of high affinity and low capacity with steroid specificity typical of an androgen receptor. The assay is suitable for samples as small as 20 mg wet weight and is linear using 25-125 microliter cytosol (correlation coefficient 0.995). Intra-assay variation is 6.8% and interassay variation 25.8% (n = 22) over 4 months. A single saturating concentration of steroid measures 97% of AR calculated by Scatchard analysis. Inclusion of high salt (0.4 M KNO3) and 10 mM dithiothreitol in incubation buffer at pH 8.4 are essential; inclusion of 10 mM sodium molybdate in the homogenisation buffer improves measurement. A comparison of AR measured in histologically similar samples obtained by a transurethral resectoscope (TUR) and a cold punch resectoscope (CPR) taken in juxtaposition demonstrated no difference in receptor content. Although carcinomatous samples contained significantly higher receptors levels than benign samples, no differences were observed between TUR and CPR specimens.

Tamoxifen decreases progesterone and nuclear androgen receptors in the human prostate

Androgen (AR) and progesterone (PR) receptors were measured in resected prostate tissues of patients with benign prostatic hypertrophy. One group of patients received an anti-estrogen, tamoxifen (Tm 20 mg b.i.d.) for 10 days prior to prostate resection; a second group served as controls and were untreated. Plasma levels of Tm were 200-500 pmol/ml at the time of surgery. Statistically significant decreases (P less than 0.05) were found in cytosol PR (154 fmol/mg DNA +/- 33 SE in 14 Tm-patients vs 266 +/- 40 SE in 13 untreated patients) and in nuclear AR (103 fmol/mg DNA +/- 70 SE in 18 Tm-patients vs 257 +/- 62 SE in 17 controls). Cytosol AR was not significantly different in Tm-treated patients (257 fmol/mg DNA +/- 79 SE in 15 Tm-patients vs 346 +/- 130 SE in 17 controls, P greater than 0.6). Although receptor recycling is one of several possible explanations, these decreases in progesterone and nuclear androgen receptors in Tm-treated patients suggest that estrogen has a role in the biological regulation of steroid receptors in the human prostate.

Physicochemical characterization of the androgen receptor from hyperplastic human prostate

In this manuscript we have characterized the androgen receptor from human benign prostatic hypertrophied (BPH) tissue. BPH tissue was obtained fresh from surgery, ground, and frozen in liquid nitrogen. Tissue was homogenized in 10 mM Tes buffer (pH 7.4 at 25 degrees C) containing 0.25 M sucrose, 20 mM Na2MoO4, 12 mM monothioglycerol, and 1.5 mM EDTA. Cytosol was labeled with (3H)-R1881 (0.5-10 nM) +/- a 100-fold excess of R1881 and a 500-fold excess of triamcinolone acetonide to identify specific androgen receptor sites. An exchange assay was developed, whereby maximum binding was achieved by raising the temperature to 30 degrees C for 15 min. A high-affinity binding protein was detected (Kd = 1.3 +/- 0.8 nM) which had a binding capacity of 15 +/- 7 fmol/mg protein. Binding was specific for androgens with the following Ki (nM) values: R1881 (0.09), dihydrotestosterone (6), testosterone (50), progesterone (92), estradiol (100), epitestosterone (860), and cortisol (greater than 1,000). Under high ionic conditions the sedimentation coefficient of the receptor was 4.1 S. Higher S values were not observed in the presence of the following protein inhibitors: leupeptin (20 or 150 microM), iodoacetamide (10 mM), DFP (5 mM), PMSF (1 mM), bacitracin (0.1 mM), antipain (0.1 mM), aprotinin (1 TIU/ml). Gel filtration analysis revealed a Stokes radius of 6.5 nm. These data indicate a Mr of 120,000 and a f/fo of 2.01. The receptor eluted from a chromatofocusing column at a pH of 6.8. The receptor bound to phosphocellulose and DNA cellulose after being heat-treated for 15 min at 30 degrees C. These results suggest that BPH tissue contains an androgen receptor which is similar to receptors in other androgen-responsive tissues.

Distribution of specific binding of [3H]promegestone in benign prostatic hypertrophy in regard to age, race and histological differences

Progesterone receptors were measured in BPH tissues obtained via open prostatectomy on over thirty [30] patients. Specific receptor concentration was determined by computation of the suppressible binding from the 8S region of the glycerol density gradient (centrifuged in a vertical rotor) as described by McGuire and his colleagues. Measurable progesterone receptor concentrations were obtained from all thirty specimens. These patients were subsequently categorized on the basis of several parameters including age, race, and histology of the hyperplasia. Age and race groupings demonstrated no specific distribution pattern, however, there was a marked difference in mean receptor concentration between the histological classifications.