Estradiol regulation of the human retinoic acid receptor alpha gene in human breast carcinoma cells is mediated via an imperfect half-palindromic estrogen response element and Sp1 motifs.

Estrogen receptor (ER)-positive human breast carcinoma (HBC) cell lines express significantly higher levels of retinoic acid receptor alpha (RAR alpha) (isoform 1) mRNA than ER-negative HBCs. Estradiol enhances RAR alpha mRNA expression in different ER-positive HBCs by 2-3-fold, which in turn results in increased sensitivity of ER-positive HBCs to the growth inhibitory effects of retinoic acid. To investigate the regulatory mechanisms of estradiol-mediated enhancement of RAR alpha mRNA expression, the functional promoter for the human RAR alpha isoform 1 was cloned and used to assess estradiol-mediated promoter-dependent enhancement of firefly luciferase reporter gene activity in transiently transfected ER-positive (MCF-7 and T47D) and ER-negative (MDA-MB-231) HBCs. Deletional promoter constructs were obtained to further delineate the promoter region responsible for estradiol-mediated enhancement of promoter activity. Here, we present evidence that approximately 130 bp of the promoter fragment preceding the transcriptional start site are responsible for estradiol-mediated enhancement of hRAR alpha gene expression. The estradiol-mediated enhancement is dependent on ER binding. Further deletional analysis showed that a promoter sequence of 42 base pairs, located approximately 100 bases upstream of the transcriptional start site, contains elements for estradiol-mediated enhancement. Specific deletion of either the Sp1 motif or mutations in the imperfect half-palindromic estrogen response element motif of this fragment abolish its estradiol responsiveness in transient transfections.

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.

A low-affinity estrogen-binding site in pregnant rat uteri: analysis and partial purification.

We have identified a low-affinity (type II) estrogen-binding site (EBS) that is expressed at high levels during pregnancy in rat uteri. Although this activity was detectable in nonpregnant rat uteri, it was present in amounts (0.094 pmol/g of uteri) that were severalfold lower than the high-affinity type I estrogen receptor (0.57 pmol/g of uteri). During pregnancy, at 19-20 days of gestation, the low-affinity type II EBS became the major (> or = 88%) estrogen-binding site in rat uteri. The increase in the level of low-affinity EBS (7.9 pmol/g) in uteri was approximately 85-fold with an approximately 20-fold increase in the specific activity (0.39 pmol/mg) of this form, whereas the high-affinity form remained relatively unchanged. We report here a method of purification of type II EBS from pregnant rat uteri and present an analysis of its DNA and steroid-binding properties. Estradiol-binding studies and Scatchard analysis showed that the type II EBS had an apparent estradiol-binding affinity of > or = 24 nM. Gel filtration and SDS/PAGE analysis indicated that the type II EBS was a monomeric 73-kDa protein. The estradiol binding remained apparently uninhibited in the presence of a large excess of tamoxifen, nafoxidine, or dihydrotestosterone. Estradiol, diethylstilbestrol, and quercitin (a type II EBS-specific inhibitor) competed efficiently. The purified low-affinity EBS did not have sequence-specific DNA-binding activity with the estrogen-responsive element, which indicated that it differs in function from the type I estrogen receptor.

Hormonal modulation of herpes simplex virus replication in a mouse neuroblastoma cell line.

In this study, the effect of the synthetic glucocorticoid hormone dexamethasone (DXM) on HSV replication was studied in a DXM receptor-positive mouse neuroblastoma (NB) cell line. In cells treated with 10(-7) M DXM and then infected with HSV, there was a statistically significant 9-18-fold increase in the amount of virus produced in these cells compared to untreated controls. Adsorption kinetic studies with HSV were performed in DXM-treated NB cells and untreated controls. It was found that there was a significant increase in the adsorption rate of HSV in the DXM-treated cells as compared with the controls. During the course of these studies, a strain of NB cells was noted to have lost its ability to stimulate HSV replication following DXM treatment. Receptor binding assays were performed on cytosols prepared from NB cells that responded with an increase in HSV titers to DXM treatment and the new strain of NB cells that was DXM refractile. These latter cells were found to have lost their DXM receptors. These results indicate that the modulation of HSV replication of DXM treated cells was regulated by the presence of DXM receptors in these cells. Once lost, the cells do not respond to DXM treatment with increased HSV replication. These observations may lead to a clinical assay to determine patients with high glucocorticoid levels who may be at risk of recurrent herpes infections.

Identification of an estrogen-binding protein in Pseudomonas aeruginosa.

A constitutive estrogen-binding protein (EBP) has been identified in the cytosol of Pseudomonas aeruginosa, a Gram-negative bacterium. All 14 strains tested contained the EBP. Estradiol binding was rapid and maximal binding occurred by 90 min at 0 degrees C. Dissociation of estradiol from the binding protein occurred at a rate of 4.6 fmol/min with a t1/2 of 42 min. EBP binding was destroyed by protease treatment and at high temperature. Sodium molybdate had no effect on binding. The Kd determined by Scatchard analysis was 3.9 nM and the Bmax was 323 fmol/mg protein. The EBP sedimented at 8.9 S on sucrose density gradients. The presence of 0.4 M KCl increased estradiol binding 6-fold but did not cause a shift in the sedimentation value. Gel filtration of the native protein gave an estimated molecular weight of 215,000 and a Stokes radius of 50.2 A. Steroid binding specificity, in order of decreasing affinity, was estradiol, estrone, dihydrotestosterone, estriol, testosterone, progesterone and promegestone. Other steroid hormones tested did not compete for estradiol binding. Identification of an EBP in a bacterium allows a comparative analysis of other steroid-binding proteins in unicellular microorganisms.

The effects of various serine protease inhibitors on estrogen receptor steroid binding.

Two serine protease inhibitors, phenylmethanesulfonyl fluoride (PMSF) and diisopropylfluorophosphate (DFP), were utilized to investigate the possible involvement of serine hydroxyl groups on 17 beta-estradiol binding to the rat estrogen receptor (ER). Single point saturation analysis and Scatchard analysis demonstrated that both 5 mM PMSF and 5 mM DFP were able to inhibit steroid binding to the ER after incubation at 37 degrees C, but neither were able to inhibit steroid binding of the nonactivated ER (0-4 degrees C). The reducing agent dithiothreitol (DTT) was used to differentiate between the interaction of PMSF with serine groups or with sulfhydryl groups of the receptor. When incubated in the presence of 5 mM PMSF, various concentrations of DTT up to 25 mM were not able to overcome the inhibition of this agent, indicating that there was no interaction of PMSF with sulfhydryl groups. Thus, these findings indicate that serine hydroxyl groups are involved in steroid binding of the rat ER.

Evidence for involvement of tyrosine in estradiol binding by rat uterus estrogen receptor.

The possibility of tyrosine involvement in steroid binding by rat uterus estrogen receptor (rER) was investigated. Chemical modification of rER with reagents such as tetranitromethane (TNM) and N-acetylimidazole (NAcI) inhibited estradiol binding. Steroid binding was inhibited to a greater extent at pH 8 than at pH 6, indicating the participation of tyrosine (TNM has increasing affinity for cysteine ove tyrosine at pH 6). Inhibition patterns remained similar for incubations at 0-4 degrees C or 37 degrees C. NAcI inhibited rER steroid binding at 37 degrees C, but not at 0-4 degrees C. Hydroxylamine incubated in the presence of rER and NAcI appeared to reverse this inhibition. Thus, these findings indicate that the phenyl ring and possibly the phenolic hydroxyl of tyrosine are involved in steroid binding of the receptor.

Identification of gonadal steroid receptors in meningiomas from dogs and cats.

Cytosolic assay was used to detect gonadal steroid receptors in brain tumor tissue from 6 dogs and 2 cats. For 4 samples, the maximal number of binding sites and the equilibrium dissociation constant were calculated, using Scatchard analysis. The concentration of receptor protein that was discovered was similar to that detected in hormone-sensitive tumors.

Effect of dexamethasone on herpes simplex virus replication in mouse neuroblastoma cells (NB41A3): receptor characteristics.

Monolayers of NB41A3 (MNB) cells were exposed to pharmacologic doses of dexamethasone (DXM). After 24-h, the cells were infected with herpes simplex virus type 1 (HSV-1) at a multiplicity of infection (m.o.i.) = 0.1. After every 24-h period, extracellular and intracellular virus aliquots were collected and frozen. The aliquots were titered in a standard plaque-forming assay. It was shown that the hormone led to a statistically significant increase of extra- and intracellular virus titers above the titers exhibited by these cells without added hormone. The same experiment was repeated in Vero cells, but the hormone did not elevate the resultant HSV-1 titers. A binding assay was performed on these two cell lines by use of 3H-DXM to determine if a DXM receptor was present. Specific binding was seen, but only in the MNB cell line. The Bmax of this receptor was 480 fmol/mg protein and it had a Kd of 2.3 nM. The S value of the receptor ligand complex equalled 8.0. These results indicate that cells possessing hormone receptors allow for a more efficient replication of the virus and suggest that these hormones may play an important role in the exacerbation of herpes simplex virus infection in vivo.

Phenylmethylsulfonyl fluoride (PMSF) inhibits 17 beta-estradiol binding to estrogen receptor from human prostate.

Estrogen receptor binding studies were performed on cytosol obtained from human benign prostatic hyperplasia (BPH) tissue. Binding assays were done in the absence or presence of various concentrations of phenylmethylsulfonyl fluoride (PMSF). Saturation analysis and Scatchard plots showed that the binding of 17 beta -estradiol to the estrogen receptor (ER) was inhibited by PMSF. The nature of the inhibition appears to be uncompetitive, as determined from double-reciprocal plots. Glycerol density gradient centrifugation analysis also confirmed the results obtained with Scatchard plots. The inhibition observed in the presence of dithiothreitol (DTT) was greater than the inhibition observed in the absence of DTT. The maximum number of binding sites (Bmax) observed in our present study was 59.1 +/- 34.1 fmol/mg protein with an equilibrium dissociation constant (KD) of 2.2 +/- 2.2 nM. Our study indicates that PMSF significantly affects 17 beta -estradiol binding to ER and consequently alters the estimation of ER in Human BPH.

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.

Effect of dextran-coated charcoal treatment on 17 beta-estradiol receptor in human benign prostatic hyperplasia.

Using glycerol density gradient centrifugation technique, single saturation dose assay, and Scatchard plot, the effect of dextran-coated charcoal (DCC) treatment of homogenate or crude cytosol on estradiol binding protein in human benign prostatic hyperplasia was investigated. Receptor binding is increased after thirty minutes DCC treatment of homogenate or cytosol. Increase in estradiol binding is accompanied by loss in cytosolic protein. A 75 per cent increase in binding of estradiol to its receptor was observed after two hours incubation of DCC with homogenate. The concomitant increase in estradiol binding and decrease in protein concentration in both homogenate or cytosol after DCC treatment indicate the possible removal of some protein(s) which inactivate(s) the estradiol receptor. Removal of cofactors required for activation of proteases and removal of endogenous steroids which could be occupying the estradiol sites also are possible. This simple experimental procedure has improved significantly the methodology for the measurement and characterization of estrogen receptor in human BPH.

A multifactorial analysis of steroid hormone receptors in stages I and II breast cancer.

It has been shown that the level of estrogen receptors (ER), and to some extent progesterone receptors (PR), correlate to a high degree to the response to endocrine therapy in advanced breast cancer patients. To evaluate the prognostic value of ER/PR in early breast cancer, 80 patients with stages I and II were studied. They all underwent modified radical mastectomy. Patients with stage I disease (negative LN) received no further treatment, while those with stage II received standard adjuvant chemotherapy. All the patients were followed for 4 years. The ER and PR were measured in each primary tumor by the glycerol density gradient method. Values of 10 fmole/mgm protein or greater were considered positive (+) and less than 10 fmole/mgm were considered negative (-). The results revealed: (1) Fifty-two patients (65%) had ER+, of which 44 (85%) were also PR+; 28 patients had ER-, of which 24 were also PR- (p less than 0.0001). (2) ER/PR correlated with age as 71% of the patients over age 50 had ER+/PR+, compared to 33% of those under age 50 (p less than 0.05). (3) Postmenopausal patients had a higher incidence of ER+/PR+. (4) Primary tumors less than 2 cm in size had higher ER+; 71% in those with stage I and 80% in stage II. (5) Fifty-eight per cent (38) of patients with ductal carcinoma had ER+/PR+, compared to 67% (4) with lobular carcinoma. (6) The disease-free survival of patients with ER+ tumors was significantly longer than those with ER- tumors (p less than 0.005) both in positive and negative LN patients. The same was true for PR+ compared to PR- (p less than 0.005), but only in those with stage II disease. The overall survival rates were similarly significant in favor of ER+ and PR+ patients (p less than 0.025), but only in stage II disease. It seems that the status of steroid hormone receptors has a major prognostic factor second only to the LN status.

Estrogen and progesterone receptors in meningiomas.

Two-thirds of all meningiomas and four-fifths of intraspinal and sphenoidal meningiomas occur in women. Meningiomas frequently enlarge or become symptomatic during pregnancy or during the luteal phase of the menstrual cycle. There is an increased incidence of meningiomas in women with breast carcinoma. In a series of 23 patients with meningiomas, the authors assayed biopsy specimens of the tumor for the presence of estrogen (ER) and progesterone (PR) receptors, using glycerol density gradient centrifugation and dextran-coated charcoal techniques. Significant levels of ER were found in only 17% of the patients, while significant PR levels were detected in 39%. Only one of the 16 tumors from female patients had significant ER levels, whereas three of the seven tumors from men had significant ER levels. Eight of the 16 tumors in women had significant PR levels, whereas only one of the seven tumors in men had a significant PR level. Thus, three out of four tumors with definite ER were from men, whereas eight of nine tumors with definite PR were from women. Of the eight women whose tumors contained PR, three were premenopausal and five postmenopausal. The single tumor with high levels of PR in the male patient was histologically atypical. The results of this series were compared with six published series of sex steroid assays in meningiomas. These seven series were divided into two groups: one group included two reports from the same laboratories in France, and the other the remaining five reports. Much higher percentages of both ER- and PR-positive tumors were reported from the French group. The authors suggest that this discrepancy may be due to the use of preoperative glucocorticoid therapy in the series from the United States. Since meningiomas are known to enlarge during periods when levels of circulating progestins are high, the presence of significant quantities of PR in a high percentage of tumors may have therapeutic implications for recurrent, malignant, or incompletely excised tumors, or for medically fragile patients. Conversely, since meningiomas are not known to enlarge during the proliferative phase of the menstrual cycle or with exogenous estrogen therapy, the small number of tumors positive for ER may indicate that ER lacks clinical significance. High levels of PR found in a small group of histologically aggressive tumors in several series may indicate that hormonal therapy may be especially useful in this difficult subset of patients.

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.

Characterization and stabilization of progesterone receptors in human benign prostatic hypertrophy.

Experimental conditions for the optimum detection and measurement of the cytosolic progestogen receptor in human prostatic hyperplasia and neoplasia are described. In presence of 20 mM molybdate ion and a reaction time of 0.5-2 h at 0-2 degrees C, we are able to detect the appearance of a [6.7-3H]-17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione ([3H]-R5020) and [3H]-progesterone binding moiety in human prostatic cytosol. The [3H]-R5020 binding protein sediments at approximately 8-11S in a glycerol density gradient centrifuged in a Sorvall TV865 rotor (vertical rotor). Maximal binding of [3H]-R5020 occurs at 30 min at 25 degrees C and 1 h at 0 degree C. Considerable overall improvement in receptor detection and measurement was made when gradient centrifugation was carried out in a vertical rotor instead of swing bucket rotor. The specifically bound [3H]-R5020 is displaced by progesterone, triamcinolone acetonide and R5020, but not by cortisol, dihydrotestosterone, 17 beta-estradiol, or diethylstilbestrol. High affinity was demonstrated by Scatchard analysis on binding of [3H]-5020 to receptors from cytosol of benign prostatic hypertrophy (BPH) giving a KD of 2.4 X 10(-10)M and a binding site concentration of 50 fmol/mg protein. Molybdate ion maintains the hormone receptor complex in 8-11S form which is totally converted to the 4-5S form in the presence of 0.6 M K Cl. The optimum concentration of fluoride ion for enhancing the specific binding of [3H]-R5020 was determined to be between 20 and 50 mM. Cytosol from human BPH in the presence of 25 mM sodium fluoride contains [3H]-R5020 receptors which sedimented mostly in the 4-5S region of glycerol density gradient. Sodium-molybdate and sodium fluoride stabilize and stimulate the specific [3H]-R5020 receptor complex at 25 and 0 degree C. The loss of specific receptor hormone binding capacity can be reversed by fluoride and, to a lesser extent, by molybdate.

Androgen, estrogen, and progesterone receptors in peripheral and central zones of human prostate with adenocarcinoma.

For this study a prostate gland was obtained by retropubic total prostatectomy performed on a seventy-six-year-old patient at Gunma University Hospital. A surgical pathologist separated the gland into peripheral and central portions which were clearly divided by a fibrous stroma. Histopathologic examination of each layer revealed different patterns of adenocarcinoma. The cytosol was incubated with [3H]R1881, [3H]estradiol, or [3H]R5020 in the presence or absence of 100-fold excess unlabeled competing, R1881, diethylstilbestrol, or R5020, respectively. In addition, to measure only androgen receptor all androgen tubes contained 1 X 10(-5) M triamcinolone acetonide. Using glycerol density gradient technique, concentrations of androgen, estrogen, and progestogen receptor were measured on both tissues. Specific receptor concentrations were determined by computation of the suppressible binding from the 8S region of the gradients. The ratio of the androgen receptor to progestogen receptor in the central zone was 1.5 to 2.0 while the same ratio in the peripheral zone was 0.3 to 0.5. Estrogen receptor could not be detected in either portion of this gland, possibly because the patient had received large amounts of diethylstilbestrol diphosphate prior to operation. This is the first report of varying hormone receptor profiles in different anatomic zones of the human prostate.

Analysis of Estramustine binding protein (EBP) in rat dorsal prostate by means of high pressure liquid chromatography.

High pressure liquid chromatography (HPLC, Toyo Soda TSK-GEL G3000 SW column) was used to analyse the properties of Estramustine binding protein (EBP) in the cytosol of rat dorsal prostate. There exist in the cytosol of rat dorsal prostate two binding components having a high affinity for Estramastine. When estimated by HPLC, the molecular weights of these Estramustine binding components are 45,000-50,000 and 25,000-30,000 daltons, respectively. The binding of 3H-Estramustine to a macromolecule with a molecular weight of 25,000-30,000 is more heat labile than binding of 3H-Estramustine to a macromolecule with a molecular weight of 45,000-50,000. The present study also demonstrates that the HPLC method offers higher resolution, smaller sample size and faster analysis than other methods used in binding studies.

Stabilization of 8S progesterone receptor from human prostate in the presence of molybdate ion.

In the presence of 10 mM molybdate ion, we are able to detect the appearance of a [6,7-3H]-17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione-([3H]R5020) binding moiety in human prostatic cytosol which sedimented at approximately 8S in a glycerol density gradient. The specifically bound [3H]-R5020 was displaced by progesterone, tiramcinolone acetonide, and R5020 but not by cortisol, dihydrotestosterone, 17 beta-estradiol, or diethylstilbestrol. Specific binding of [3H]R5020 in the presence of molybdate ion was shown to saturate at 7 x 10(-10) M (n = 64 fmol/mg of protein). The optimum concentration of molybdate ion for enhancing specific binding of [3H]-R5020 was determined to be between 7 and 20 mM. Molybdate ion was also effective in stabilizing the 8S R5020-binding moiety in a preincubation for 16 hr at 0 degrees in the absence of added steroid.