The biology and mechanism of steroid hormone receptor interaction with the eukaryotic nucleus

The extra-nuclear interactome of the estrogen receptors: implications for physiological functions

Over the last decades, a great body of evidence has defined a novel view of the cellular mechanism of action of the steroid hormone 17β-estradiol (E2) through its estrogen receptors (i.e., ERα and ERβ). It is now clear that the E2-activated ERs work both as transcription factors and extra-nuclear plasma membrane-localized receptors. The activation of a plethora of signal transduction cascades follows the E2-dependent engagement of plasma membrane-localized ERs and is required for the coordination of gene expression, which ultimately controls the occurrence of the pleiotropic effects of E2. The definition of the molecular mechanisms by which the ERs locate at the cell surface (i.e., palmitoylation and protein association) determined the quest for understanding the specificity of the extra-nuclear E2 signaling. The use of mice models lacking the plasma membrane ERα localization unveiled that the extra-nuclear E2 signaling is operational in vivo but tissue-specific. However, the underlying molecular details for such ERs signaling diversity in the perspective of the E2 physiological functions in the different cellular contexts are still not understood. Therefore, to gain insights into the tissue specificity of the extra-nuclear E2 signaling to physiological functions, here we reviewed the known ERs extra-nuclear interactors and tried to extrapolate from available databases the ERα and ERβ extra-nuclear interactomes. Based on literature data, it is possible to conclude that by specifically binding to extra-nuclear localized proteins in different sub-cellular compartments, the ERs fine-tune their molecular activities. Moreover, we report that the context-dependent diversity of the ERs-mediated extra-nuclear E2 actions can be ascribed to the great flexibility of the physical structures of ERs and the spatial-temporal organization of the logistics of the cells (i.e., the endocytic compartments). Finally, we provide lists of proteins belonging to the potential ERα and ERβ extra-nuclear interactomes and propose that the systematic experimental definition of the ERs extra-nuclear interactomes in different tissues represents the next step for the research in the ERs field. Such characterization will be fundamental for the identification of novel druggable targets for the innovative treatment of ERs-related diseases.

Extranuclear signaling by sex steroid receptors and clinical implications in breast cancer

Estrogen and progesterone play essential roles in the development and progression of breast cancer. Over 70% of breast cancers express estrogen receptors (ER) and progesterone receptors (PR), emphasizing the need for better understanding of ER and PR signaling. ER and PR are traditionally viewed as transcription factors that directly bind DNA to regulate gene networks. In addition to nuclear signaling, ER and PR mediate hormone-induced, rapid extranuclear signaling at the cell membrane or in the cytoplasm which triggers downstream signaling to regulate rapid or extended cellular responses. Specialized membrane and cytoplasmic proteins may also initiate hormone-induced extranuclear signaling. Rapid extranuclear signaling converges with its nuclear counterpart to amplify ER/PR transcription and specify gene regulatory networks. This review summarizes current understanding and updates on ER and PR extranuclear signaling. Further investigation of ER/PR extranuclear signaling may lead to development of novel targeted therapeutics for breast cancer management.

Targeting oncogenic transcription factors by polyphenols: A novel approach for cancer therapy

Inflammation is one of the major causative factor of cancer and chronic inflammation is involved in all the major steps of cancer initiation, progression metastasis and drug resistance. The molecular mechanism of inflammation driven cancer is the complex interplay between oncogenic and tumor suppressive transcription factors which include FOXM1, NF-kB, STAT3, Wnt/β- Catenin, HIF-1α, NRF2, androgen and estrogen receptors. Several products derived from natural sources modulate the expression and activity of multiple transcription factors in various tumor models as evident from studies conducted in cell lines, pre-clinical models and clinical samples. Further combination of these natural products along with currently approved cancer therapies added an additional advantage and they considered as promising targets for prevention and treatment of inflammation and cancer. In this review we discuss the application of multi-targeting natural products by analyzing the literature and future directions for their plausible applications in drug discovery.

Xenoestrogen regulation of ERα/ERβ balance in hormone-associated cancers

The hormone 17β-estradiol (E2) contributes to body homeostasis maintenance by regulating many different physiological functions in both male and female organs. E2 actions in reproductive and non-reproductive tissues rely on a complex net of nuclear and extra-nuclear signal transduction pathways triggered by at least two estrogen receptor subtypes (ERα and ERβ). Consequently, the de-regulation of E2:ER signaling contributes to the pathogenesis of many diseases including cancer. Among other factors, the ERα/ERβ ratio is considered one of the pivotal mechanisms at the root of E2 action in cancer progression. Remarkably, several natural or synthetic exogenous chemicals, collectively called xenoestrogens, bind to ERs and interfere with their signals and intracellular functions. In this review, the molecular mechanism(s) through which xenoestrogens influence ERα and ERβ intracellular concentrations and the consequences of this influence on E2-related cancer will be discussed.

Characterization of estrogen response element binding proteins as biomarkers of breast cancer behavior

BACKGROUND

While investigating estrogen response element (ERE) binding properties of human estrogen receptor-α (hERα) in breast cancer cytosols, other ERE-binding proteins (ERE-BP) were observed.

DESIGN AND METHODS

Recognition properties of ERE-BP were evaluated by electrophoretic mobility shift assays (EMSA) with ERE sequences of the 5'-flanking region of the estrogen responsive gene vitellogenin A2 (VitA2). Cytosols were incubated 16 h, 4 °C with [32P]ERE sequences and separated by EMSA. A method of estimating ERE-BP levels was developed by measuring band intensity from EMSA profiles, expressed in digital light units (DLU)/μg protein and normalized to total DLU. ERE-BP were purified by affinity chromatography and EMSA, and then identified by mass spectrometry.

RESULTS

ERE-BP in cytosols did not supershift in the presence of anti-hERα or anti-hERβ antibodies recognizing different ER epitopes suggesting that they are not fragments of either receptor isoform. ERE-BP competed with hERα for binding to VitA2-ERE. Increased levels of ERE-BP DNA-binding activities measured in 310 cytosols prepared from breast cancer biopsies correlated with decreased patient survival. Strikingly, breast cancer patients with ER negative status and high ERE-BP expression exhibited the poorest disease-free and overall survival. After purification, ERE-BP were identified as Ku70 (XRCC6) and Ku80 (XRCC5) using mass spectrometry. ERE-BP were confirmed to be Ku70/80 by supershift assay.

CONCLUSION

Presence of these novel ERE-binding proteins in a breast carcinoma is a strong predictor of poor prognosis. Our results suggest that ERE-BP, identified as Ku70/Ku80, in cytosols prepared from breast carcinoma biopsies are useful biomarkers for assessing risk of breast cancer recurrence.

Regulatory decisions on endocrine disrupting chemicals should be based on the principles of endocrinology

For years, scientists from various disciplines have studied the effects of endocrine disrupting chemicals (EDCs) on the health and wellbeing of humans and wildlife. Some studies have specifically focused on the effects of low doses, i.e. those in the range that are thought to be safe for humans and/or animals. Others have focused on the existence of non-monotonic dose-response curves. These concepts challenge the way that chemical risk assessment is performed for EDCs. Continued discussions have clarified exactly what controversies and challenges remain. We address several of these issues, including why the study and regulation of EDCs should incorporate endocrine principles; what level of consensus there is for low dose effects; challenges to our understanding of non-monotonicity; and whether EDCs have been demonstrated to produce adverse effects. This discussion should result in a better understanding of these issues, and allow for additional dialog on their impact on risk assessment.

Regulation of pulmonary arachidonic acid metabolism by anti-inflammatory steroids

Enzymes in cells from many tissues including the lung metabolize arachidonic acid to a variety of highly active local hormones such as prostaglandins and 'slow-reacting substances'. Many of these play a part in the inflammatory response which follows injury or trauma or, in the case of slow-reacting substance, asthmatic bronchoconstriction. Both non-steroidal and steroidal anti-inflammatory drugs inhibit the formation of some or all of these products. The non-steroidal drugs block prostaglandin formation but not the formation of products such as slow-reacting substances. The steroids block the formation of all products. Their mechanism of action, investigated in the guinea-pig perfused lung, involved inhibition of arachidonic acid liberation, probably by suppression of phospholipase activity. To achieve this steroids must first bind to receptors in lung tissue and initiate de novo RNA and protein synthesis. This culminates in the synthesis or secretion by some cells in the lung of a polypeptide of mol.wt. 10 000-15 000 with potent anti-phospholipase properties. The generation of this factor could partly explain why steroids are so effective in the treatment of many types of inflammatory disease, and in particular why they are so efficacious against asthma.

Vitamin K2 binds 17β-hydroxysteroid dehydrogenase 4 and modulates estrogen metabolism

Vitamin K is a cofactor for gamma-glutamyl carboxylase, an enzyme that is important for blood coagulation. Recent studies have shown that vitamin K has other roles, in addition to post-transcriptional modification, such as bone metabolism and antitumoral actions; these findings have indicated that there might be unknown intracellular binding proteins that are specific for vitamin K. In this study, vitamin K-binding proteins were characterized by pull-down experiment using a chemically synthesized biotynylated vitamin K followed by mass spectrometric identification of the pull-downed components. The results indicated that 17beta hydroxy steroid dehydrogenase 4, apolipoportein E, and 40S ribosomal proteins S7 and S13 might be the candidates of the vitamin K-binding proteins. Subsequent experiments showed that vitamin K2 binds 17beta hydroxysteroid dehydrogenase 4 and decreases the intracellular estradiol:estrone ratio, which resulted in the inhibition of the amount of estrogen receptor alpha-binding to its target DNA. These results suggest a possible novel role for vitamin K in modulating estrogen function.

Structural regions of ERalpha critical for synergistic transcriptional responses contain co-factor interacting surfaces

Most highly estrogen responsive genes are synergistically activated by multiple copies of estrogen responsive elements (EREs) capable of binding to the estrogen receptor (ER). We examined here the structural features of the receptor necessary to interact with co-regulatory proteins and to produce a synergistic pattern of activation from multiple EREs. Using full length and truncated variants of ERalpha, we show in transfected mammalian cells that although the carboxyl (AF-2) and the amino (AF-1) terminal activation domains are functionally integrated to induce transcription, AF-1 is critical for mediating synergy. Partial characterization of AF-1 sub-domains revealed that both Box-1 and Box-2 regions (amino acids 41-64 and 87-108, respectively) are essential for a synergistic response to estrogen. We show that members of the p160 family of co-factors and TIF-1 interact with the AF-2 domain of ERalpha. We also found that TIF-2, a member of the p160 family, can interact with the Box-1 region of AF-1. Apparently, structural regions required for the ability of ERalpha to induce transcription synergistically from tandem ERE sequences are also critical for the interaction of the receptor with the co-regulatory proteins.

Effect of 17beta-estradiol on inhibition of platelet aggregation in vitro is mediated by an increase in NO synthesis

The low prevalence of coronary heart disease in premenopausal women and its increase after menopause are well established. Although estrogen is thought to play a role in protecting the vasculature, the mechanism has not been fully clarified. The contribution of platelets to atherosclerotic cardiovascular diseases is well recognized. The present study focused on the still-controversial effect of estrogen on platelet function. We investigated the in vitro effects of estrogen on human platelets, including their aggregation, Ca2+ metabolism, the synthesis of cyclic nucleotides, and NO (nitrite/nitrate) synthesis after stimulation with thrombin or ADP. Pretreatment of platelets with 17beta-estradiol reduced the platelet aggregation induced by thrombin or ADP, whereas 17alpha-estradiol had no effect. 17Beta-estradiol accelerated the recovery of [Ca2+]i after the agonist-induced peak and reduced the area under the curve of accumulated platelet [Ca2+]i but did not alter the baseline [Ca2+]i, Ca2+ influx induced by thrombin or ADP, the release of Ca2+ from internal stores, or the size of internal Ca2+ stores. Pretreatment of platelets with 17beta-estradiol had no effect on the intracellular concentration of cAMP but increased that of cGMP in agonist-stimulated platelets. Additionally, 17beta-estradiol increased the platelet concentration of nitrite/nitrate in a dose-dependent manner. These effects of 17beta-estradiol on platelet aggregation, Ca2+ metabolism, and NO synthesis were abolished by exposure to N(G)-monomethyl-L-arginine, an NO synthesis inhibitor. These results suggest that 17beta-estradiol plays an important role in inhibiting platelet aggregation by promoting Ca2+ extrusion or reuptake activity that is dependent on the production of cGMP by increasing NO synthesis.

The action of dexamethasone on electrically-induced contractions of guinea-pig isolated ileum

1. The effect of dexamethasone and its interaction with morphine has been studied on transmurally-stimulated guinea-pig ileum preparation. 2. Dexamethasone dose-dependently depressed the contractions of the ileum; this action has a rapid onset. 3. Naloxone did not reverse the inhibitory effect of dexamethasone. 4. When dexamethasone and morphine were given in combination the maximum reduction observed was equal to the sum of the single effect of two drugs given individually and naloxone antagonized only the inhibition induced by morphine. 5. Proteic synthesis inhibitors did not modify the inhibition induced by dexamethasone. 6. RU-38486, a glucocorticoid antagonist receptor, antagonized completely the inhibitory effect of DXM without affecting the inhibition induced by morphine showing that the effect of dexamethasone occurs by glucocorticoid receptor-mediated processes.

Eleventh Gaddum memorial lecture. Lipocortin and the mechanism of action of the glucocorticoids

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Estradiol-binding molecules in the hepatocytes of the female water frog, Rana esculenta, and plasma estradiol and vitellogenin levels during the reproductive cycle

Estradiol-binding molecules have been found both in cytosol and nuclear extract of hepatocytes of the female green frog Rana esculenta. These molecules show the properties of an estradiol receptor (Re): high and specific affinity for estrogens (2.10-7.10 x 10(-10) M), stability of binding at 0 and 20 degrees, localization in the nucleus, and cytosolic versus nuclear binding shift in estradiol-treated frogs. In hepatocytes, both filled and unfilled Re is detectable in all stages of the R. esculenta annual cycle. It increases during the recovery phase (September to January) when vitellogenetic processes are active in the ovary. These changes are positively correlated with vitellogenin. Only nuclear filled Re, moreover, is positively correlated to level of circulating estradiol. This suggests a direct connection: plasma estradiol level versus nuclear filled Re versus plasma vitellogenin level.

17 beta Estradiol-induced increase in brain dopamine D-2 receptor: antagonism by MIF-1

Animal behavioral and neurochemical studies implicate dopaminergic systems in the neurological sequelae induced by estrogen. In the present study, we demonstrated for the first time that MIF-1, a neuropeptide unrelated to classical dopamine agonists, when given prior to, concurrently with, and after 17 beta-estradiol, antagonized significantly the estrogen-induced increase in the density of dopamine D-2 receptor both in the striatum and the mesolimbic area of male rat brain. The current findings have implications for the prophylactic and therapeutic potential for MIF-1 in extrapyramidal motor disorders caused by estrogen imbalance in humans.

Hormone independent activation of rat uterine estrogen receptor by exposure of isolated uteri to anaerobic conditions

Incubation of isolated rat uteri under anaerobic conditions, which consisted of either an atmosphere of carbon monoxide or nitrogen, caused an increase in nuclear estrogen binding which was not dependent on added estrogen. The incubation of uteri in the absence of added estrogen under aerobic conditions (atmosphere of oxygen or oxygen-carbon dioxide [95-5%]) did not increase uterine nuclear estrogen binding levels. High salt (0.5-M KCl) extracts of the nuclear estrogen binding moiety induced by anaerobiosis were shown to possess a sedimentation coefficient on sucrose-glycerol gradients of 4.8S, a binding specificity restricted to estrogens and an apparent affinity constant of 1.35 nM. These data confirm that the nuclear binding moiety induced by anaerobiosis possesses the characteristics of an estrogen receptor. The enhanced nuclear estrogen receptor retention induced under anaerobic conditions could be accounted for by a significant increase in nuclear receptor extracted by high salt (0.5 M KCl) and by ethanol (salt resistant fraction). Furthermore, sequential extraction of nuclear estrogen receptor from uteri exposed to aerobic conditions in the presence of added estradiol paralleled the results obtained with anaerobiosis. Total receptor retained under anaerobiosis represented 25% of that observed under aerobic conditions in the presence of estrogen. These results indicate that anaerobic conditions can cause an activation of uterine estrogen receptor. This activation process represents a pathway for receptor activation which does not require steroid.

A morphological/biochemical study on the actions of corticosteroids on rat skeletal muscle

Four corticosteroid hormones were administered (5 mg/kg/day) to rats over 6 to 10 days. Both biochemical and microscopic techniques were employed to determine the influence of these corticosteroids on the fine structure and growth of five striated muscles. Throughout, dexamethasone and triamcinalone were more potent than prednisone or cortisone in influencing muscle growth. The corticosteroids' action on the heart was anabolic, increasing its RNA and protein content. In contrast, the same corticosteroids were catabolic against fast-twitch muscles (e.g., extensor digitorum longus), inducing appreciable atrophy. However, slow-twitch muscles (e.g., soleus) were more resistant to these hormones, exhibiting an intermediate response between that of the heart and fast-twitch muscles. Only minor morphological changes were found in both fast and slow muscles 10 days after the corticosteroid treatments. The hormones' atrophic effects on skeletal muscle primarily arose from the corticosteroid's ability to inhibit protein synthesis, via decreases in the muscles' ribosomal capacities. Whole-body protein synthesis was also suppressed by these corticosteroids, but to a lesser extent than in the whole skeletal musculature.

Influence of triamcinolone, estradiol-17 beta and testosterone on 1,25-dihydroxyvitamin D3 binding performances to its chick intestinal receptor

We have investigated the effects of large molar excesses (20,000) of triamcinolone, estradiol-17 beta and testosterone on the binding performances of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] to its receptor. The source of receptor was a duodenal chromatin fraction of vitamin D replete chickens which exhibited a high level of positive cooperativity (Hill coefficient = 1.50 +/- 0.12; n = 4) in the binding of 1,25(OH)2D3 to the two sites of its intestinal receptor. Triamcinolone did not modify the affinity, cooperativity level and maximum binding capacity of the 1,25(OH)2D3 receptor. Estradiol-17 beta induced a slight but significant increase of 13 +/- 1% (P less than 0.01) of the receptor capacity and testosterone a 29 +/- 6% (P less than 0.02) increase of the receptor affinity. A combination of estradiol-17 beta and testosterone did not modify the 1,25(OH)2D3 receptor's binding performances. In conclusion, the effects of corticoids, estradiol-17 beta and testosterone under in vitro conditions on the 1,25(OH)2D3 receptor's binding performances were found to be marginal in our system. Other studies under in vivo conditions, possibly at the pre-transcriptional level, of these steroids effects on the 1,25(OH)2D3 receptor gene regulation expression would be of great interest.

Effects of the contraceptive pill on sedative responses to clonidine and apomorphine in normal women

In normal women sedation following intravenous administration of the alpha 2-adrenoceptor agonist clonidine (1.3 micrograms/kg) was significantly greater following 3 weeks' continuous treatment with the combined contraceptive pill than at the end of the 7-day withdrawal period. In contrast, sedative responses to the dopamine agonist apomorphine (5 micrograms/kg subcutaneously) were decreased when subjects were taking the contraceptive pill. These findings are in agreement with animal experimental studies, indicating that oestrogen can alter alpha-adrenoceptor and dopamine autoreceptor sensitivity. Such interactions may be involved in the effects of female sex steroids on mood.

The anti-inflammatory effect of glucocorticoid-induced phospholipase inhibitory proteins

The anti-inflammatory effect of glucocorticoids has been investigated in two standard models of experimental inflammation, i.e. rat paw oedema induced by carrageenin or dextran. Both types of oedema are suppressed by dexamethasone while indomethacin and BW755C only suppress carrageenin oedema. Dexamethasone inhibits dextran oedema according to the accepted mode of action of steroid hormones since the inhibition occurs after a 2-3 h time lag and is abolished by pretreating animals with actinomycin D. Dextran oedema and carrageenin oedema are also controlled by endogenous corticoids since adrenalectomy potentiates the paw oedema formation induced by low concentrations of phlogogenic agents. It has been shown that glucocorticoids induce both in vitro and in vivo the formation and release of antiphospholipase proteins which are anti-inflammatory in that they greatly suppress carrageenin oedema. However, these proteins have no effect on dextran oedema. We conclude that the inhibition of dextran oedema by glucocorticoids depends on the formation of another type of anti-inflammatory protein.

Difference in extractability of estradiol- and tamoxifen-receptor complex in the nuclei from MCF-7 cells with Nonidet P-40

The extraction of [3H]estradiol- and [3H]tamoxifen-receptor complex in the nuclei from MCF-7 cells with the nonionic detergent Nonidet P-40 has been studied. We found that there is a striking difference in the extractability of estradiol- and tamoxifen-receptor complex from nuclei with 0.5% Nonidet P-40. The nuclear bound estradiol-receptor complex is scarcely extractable with Nonidet P-40. In contrast, almost all of the nuclear bound tamoxifen-receptor complex is extractable. The nuclear [3H]tamoxifen-receptor complex extracted in the presence of Nonidet P-40 sediments in two peaks at 7 S and 5 S. The latter sedimentation rate is the same with that of the nuclear [3H]tamoxifen-receptor complex extracted with 0.4 M KCl. The nuclear [3H]estradiol-receptor complex extracted with 0.4 M KCl sediments at 4 S. The results suggest that interaction of tamoxifen-receptor complex with chromatin is different from that of estradiol-receptor complex.

Induction of benign prostatic hypertrophy in baboons

Hormonal manipulation of intact male baboons has produced prostatic features resembling benign prostatic hypertrophy (BPH) in man. Long-acting androgen, testosterone enanthate (TE), given weekly (200 mg i.m.) for up to six months, caused significant gravimetric and volumetric increases in the prostate; a definite glandular and marked stromal hyperplasia with fibrosis developed in the caudal lobe (CD). After twenty weeks of TE treatment, there were dysplastic (atypical) changes in the glandular lining epithelium in the CD, causing pseudostratification of the lining cells with nuclear hyperchromatism. By the twenty-eighth week, there was an increase of stromal tissue with papillary ingrowth or invagination of glandular epithelium in the CD. Serum levels of testosterone and dihydrotestosterone were significantly elevated from 10 nm/ml and 2-3 ng/ml to 30-40 ng/ml and 5-6 ng/ml, respectively. There was a 3 to 4-fold increase in androstenedione levels and an increase in estradiol-17 beta from 20 pg/ml to 80-90 pg/ml. These steroidal levels may have played a direct role in the induction of early BPH in the baboons. Cytoplasmic and nuclear androgen receptor levels were higher in the CD compared to those of the cranial lobe (CR); AR concentration was increased in the cytosol and decreased in the nuclei of both lobes in TE treated animals. Scanning and transmission electron microscopy revealed heavy deposition of collagen fibers (fibrosis) in the central and periurethral regions of the CD after the administration of TE. Glandular as well as epithelial hyperplasia was most notable in the peripheral zone of the CD. These findings are similar to observations established in human BPH, indicating that the baboon prostate may be a useful model for studying various parameters of BPH.

Autoradiographic study of nuclear localization of aldosterone binding sites in intact renal cells: lack of temperature dependency

We examined by autoradiography on intact target cells the nucleocytoplasmic distribution of aldosterone-receptor complexes and the thermodependency of the nuclear translocation process. Autoradiographs (dry films) were performed on cortical collecting tubules isolated by microdissection, after incubation of rabbit kidney pyramids with [3H]aldosterone (2 X 10(-9)M) in the presence or absence of an excess unlabelled aldosterone (X100). Paired experiments were done at 30 degrees C (1 h) or 4 degrees C (2 h). In both cases, the specific labelling was exclusively nuclear. Values were higher at 30 degrees C (14.5 +/- 1.5 specific silver grains per 100 micron2) than at 4 degrees C (5.4 +/- 0.6), with no concommitant cytoplasmic labelling (4 degrees C:0.7 +/- 0.3; 30 degrees C: -0.04 +/- 0.6). At 30 degrees C, addition of unlabelled spirolactone (X200) prevented the observed autoradiographic nuclear accumulation of aldosterone-receptor complexes, suggesting that cytoplasmic binding preceded the nuclear entry. The results suggest that, in intact cells, almost all aldosterone receptor complexes accumulate in nuclei, and that this process does not depend on temperature. In parallel biochemical-binding series we found the classical distribution of aldosterone receptor complexes both in cytoplasm and nuclei, and the classical thermodependency of nuclear translocation. The present autoradiographic results, together with similar observations reported for sex steroids (Martin P.M. and Sheridan P. J., J. steroid Biochem. 16 (1982) 215-229), question the classical model of thermodependent nuclear translocation, based on biochemical experiments.

Steroid-hormone receptors in breast cancer

An obvious problem for the surgeon or oncologist treating breast cancer has been to identify the patients likely to respond to endocrine manipulation. Until recently, clinical factors such as previous response to hormone therapy, disease-free interval, age and menopausal status, and location of the dominant metastatic lesion were the principal criteria for selecting therapeutic regimens for these women. Recently, the measurement of steroid hormone receptors has become an important laboratory test. Progress during the last decade has shown that: the most reliable methods of determining estrogen receptors (ER) and progestin receptors (PR) are multipoint titration analysis using dextran-coated charcoal, and sucrose density gradient centrifugation; 55% to 65% of primary breast tumors contain more than 10 femtomole/mg cytosol protein of ER; 45% to 55% of metastatic breast tumors contain more than 10 fmol/mg cytosol protein of ER; ER are present more often in tumors of postmenopausal women compared with those of premenopausal women; benign breast lesions such as fibrocystic disease and fibroadenomas usually contain less than 10 fmol/mg cytosol protein of ER; 90% of male breast carcinomas contain ER; approximately 55% of women with breast tumors containing ER respond objectively to endocrine therapy, either additive or ablative; less than 3% of women with breast tumors lacking ER respond objectively to hormone therapy. In addition, it has been suggested that the absence of ER in a breast tumor correlates well with an increased response to cytotoxic chemotherapy; 45% to 60% of primary or metastatic breast tumors contain PR. Also, the presence of both ER and PR in a breast tumor indicates a 75% to 80% likelihood that the patient will respond to endocrine manipulation, either additive or ablative; it has been suggested that the presence of the 8 Svedberg form of ER in a breast tumor (as detected by sucrose gradient centrifugation) improves the accuracy of selecting the patient likely to respond to endocrine therapy; and there appears to be a relationship between the quantity of ER in a breast tumor and a patient's response to endocrine therapy. The incidence of response to hormone therapy increases with increasing ER levels.

Autoradiographic study of thermo-dependent nucleo-cytoplasmic distribution of aldosterone binding sites in intact target cells

Autoradiographic studies of [3H]aldosterone [( 3H-A] and [3H]dexamethasone binding sites in intact target cells (isolated collecting tubules of rabbit and rat kidney) revealed an almost exclusive nuclear localization of the hormone-receptor complexes. In the present work we compared the nucleo-cytoplasmic repartition of [3H]A-receptor complexes studied in parallel by biochemical and autoradiographic methods. In addition, the thermo-dependency of the nuclear translocation was examined. Kidney pyramids were incubated in vitro with [3H]A (2 X 10(-9) M) in the presence or absence of a 100-fold excess unlabelled A, at 30 degrees C for 1 h or 4 degrees C for 2 h. Then tissue was processed for isolation of nuclear and cytoplasmic fractions, on the one hand, or for obtention of microdissected tubular segments on which autoradiographs on dry films were performed. Autoradiographs showed that the specific labelling was almost exclusively nuclear without significant cytoplasmic labelling, at both 30 or 4 degrees C. This indicates that almost all binding sites migrated rapidly into nuclei, and that this translocation did not depend on temperature. In contrast, parallel biochemical experiments yielded classical results, that is, at 30 degrees C, the presence of specific binding sites in both cytoplasm and nuclei with a predominance in cytoplasm. At 4 degrees C, the cytoplasmic binding was unchanged, but nuclear binding was drastically reduced, indicating thermodependency of nuclear translocation, when studied by biochemical methods including cell disruption. Autoradiographic results thus questioned the classical notion of thermo-dependent nuclear translocation of aldosterone-receptor complexes, based on results obtained by biochemical methods.

Chromatin proteins of rat preputial-gland: acute changes in response to estrogen

The effects of estradiol-17 beta (E2 beta) at 2 or 15 min in vivo on chromatin proteins of rat preputial-gland were analyzed by a battery of electrophoretic methods. Among histones, E2 beta/control ratios for major bands of H1 decreased substantially between 2 and 15 min. In contrast, ratios of H4 increased (P less than 0.01), whereas, except for losses by 2 min in a H2B-like component and in H3.1, other core histones were unchanged. Among 0.35 M NaCl-soluble proteins, components at 34K-mol. wt and less than 21K -mol wt were increased after 2 min of E2 beta. The bulk of the hormone-responsive low-molecular weight proteins was basic in charge. Electrophoretic correlates of 6 basic lysosomal proteins corresponded to those of low-molecular weight salt-soluble chromatin proteins. Selective proteolysis initiated in vivo by E2 beta depleted some tightly-bound nonhistone proteins.

An assay for the detection of specific binding of 3-methylcholanthrene to rat liver cytosolic proteins using DEAE-cellulose

A method for the detection of the specific binding of 3-methylcholanthrene to rat liver cytosolic proteins is described. The separation of the protein-bound 3-methylcholanthrene from the free 3-methylcholanthrene was achieved using a batch DEAE-cellulose technique. Extraction of the DEAE-cellulose with 0.3 M KCl allowed the selective release and measurement of the amount of protein-bound 3-methylcholanthrene. The assay was optimized for the following parameters: time of incubation with DEAE-cellulose, time required for salt extraction, protein concentration, the concentration of KCl required to elute the specific binding proteins, the amount of DEAE-cellulose required to bind the specific binding proteins, and ligand specificity. The sedimentation properties of those 3-methylcholanthrene-binding proteins which were extracted with salt from DEAE-cellulose were examined on 5 to 20% sucrose gradients; the major binding species sedimented as a broad peak at 4.5 S.

Age-related growth of the spleen in normal and glucocorticoid treated rats

1. Age-related changes in the growth, nucleic acid content and protein turnover of the spleen have been studied in normal male rats. 2. A rapid and marked atrophy of the spleen, was found 24 hr after exposure to cortisone or dexamethasone; increased rates of protein breakdown being primarily responsible. 3. Nonetheless, the total amount of protein synthesized in the spleen (measured in vivo) was significantly decreased (30-50%) 24 hr after exposure to these steroids. 4. This compared with only a 15% decrease in whole body protein synthesis, indicating a more pronounced hormonal effect on the spleen than on most other body tissues.

Some theoretical questions of the peptide and steroid hormone regulation. Part I.: The receptor-steroid variable complex (RSVC) hypothesis of genetic regulation

Steroids exert their known biological and biochemical effects in connection with specific receptors. These effects are so various and complex that it is impossible to explain them on the basis of a concept supposing the presence of only one unique receptor molecule in the target organs. The heterogeneity in the function of steroids requires a heterogeneity in the molecular composition of the receptor-steroid complexes. Direct and indirect evidence is presented to support a multiplex, heterogene receptor theory. The possible origin of this complexity is analyzed and a new concept of specific gene regulation by heterogene receptor-steroid complexes is suggested. in this theory the distribution and sequence of one or more steroids on the receptor can carry and serve highly specific and unique information capable or recognizing and binding to the acceptor site of the chromatin and regulating gene expressions specific for steroids. The formation of such Receptor-Steroid Variable Complexes (RSVC) has been mathematically analyzed and the properties of a chromatin protein capable of detecting both the DNA and the steroid sequences on the receptor are discussed.

Progesterone therapy results in partial reversibility of uterine abnormalities of the adult anovulatory rat

The effects of progesterone therapy (5 mg, administered subcutaneously daily for 6 days) on the abnormal uterus of adult anovulatory Wistar rats have been studied. These rats, rendered anovulatory by neonatal treatment with testosterone propionate or clomiphene citrate, displayed severe hyperplasia and metaplasia of the uterine luminal epithelium and a disproportionately high content of nuclear oestrogen receptor, as a result of constant oestrogen stimulation unrelieved by progesterone [White, Moore, Elder & Lim (1981) Biochem. J. 196, 557-565]. Progesterone therapy resulted in the virtual elimination of the hyperplasia and metaplasia and a corresponding decrease in the content of nuclear oestrogen receptor with the proportion of the unoccupied nuclear receptor being increased to values exhibited by normal cyclic females. There was also a decrease in the content of progestin receptors, a putative index of oestrogenic stimulation. Further, in the testosterone-treated group, progesterone therapy resulted in the restoration of oestrogen receptor translocational responses to oestradiol stimulation. Progesterone treatment of these anovulatory rats thus provides a model system for investigating the biochemical mechanisms underlying progestin antagonism and regulation of oestrogen-stimulated cell proliferation.

The steroid ligands of estrogen binding proteins in Xenopus laevis liver cytosol are primarily metabolites 17beta-estradiol

The interactions in vitro between [3H]estradiol and liver proteins from Xenopus laevis have been examined to determine if the binding reaction meets criteria of steroid-receptors which may function in the induction of vitellogenesis. Estrogenic hormones associated with proteins is serum and liver cytosol from Xenopus laevis. However, the interactions between soluble liver proteins and estrogens apparently do not result from serum contamination of liver as specific binding was distinguishable by ligand affinity and by differential mobility on polyacrylamide gels. Steroid ligands bound by liver proteins during incubation in vitro were examined by solubility and by thin-layer chromatography. Only a small percentage (13%) of the bound radioactive ligand was recovered as the original tritium-labeled steroid, 17beta-estradiol. The major ligand was recovered as a water-soluble metabolite of estradiol which was identified tentatively as an estradiol-glucoside. To investigate whether the protein-bound estradiol metabolite(s) merely masks a small amount of authentic estradiol-receptor complexes or if the metabolite could be an intermediate in estrogen function, isolated liver nuclei were incubated with liver cytosol containing 3H-labeled steroid-protein complexes or with serum protein-steroid complexes relative to [3H]estradiol. Nuclei preferentially accumulated 3H-labeled steroids from liver cytosol protein-steroid complexes relative to [3H[estradiol from serum proteins. However, analysis of the steroids recovered in the nuclei after incubation with liver cytosol revealed that both 17beta-[3H]estradiol and the 3H-labeled water-soluble metabolite were retained in vitro by nuclei.U

Changes in cadaverine and putrescine metabolism in the mouse kidney induced to growth by an anabolic steroid

The formation of cadaverine and putrescine was studied in the kidneys of gonadectomized male mice stimulated to growth by nandrolone, an anabolic steroid with low androgenic activity. Administration of nandrolone resulted in an increased kidney weight and elevated activities of lysine and ornithine decarboxylase (assayed by measurement of the formation of 14CO2 from the 1-14C-labelled amino acids). The responses were dose and time dependent. The elevated enzyme activities were reflected by an increased endogenous kidney content of cadaverine and putrescine as well as in an increased urinary excretion of the diamines. Further, the kidney content and the urinary excretion of the polyamines spermidine and spermine were elevated on nandrolone treatment. Fractionation of kidney extracts on pore gradient electrophoresis revealed an apparent molecular weight of about 95 000 Daltons of the lysine decarboxylase as well as of the ornithine decarboxylase. On electrofocusing it was evident that both enzymes were present as more than one isoelectric form. However, the main form in both cases focused at a pH of about 5.0.

Progesterone regulation of the occupied form of nuclear estrogen receptor

Total concentrations of estrogen receptor in the uterine nuclear fraction are reduced rapidly after progesterone treatment of the proestrous hamster. Progesterone acts selectively on the occupied form of the nuclear estrogen receptor, with no effect on the concentration of an unoccupied form. This observation indicates that progesterone modulates the action of estrogen by controlling nuclear retention of the estrogen-receptor complex.

The nuclear oestrogen receptor in the female rat. Effects of oestradiol administration during the oestrous cycle on the uterus and contrasting effects of progesterone on the uterus and hypothalamus

Oestradiol administration to immature or ovariectomized rats has been reported to increase the uterine content of long-term nuclear oestrogen receptors. However, in the intact adult female rat, oestradiol administration did not increase the concentration of long-term nuclear oestrogen receptors at all phases of the oestrous cycle. Progesterone administration to rats in late dioestrus did not affect the concentration of uterine nuclear oestrogen receptors 24 h later, although it did prevent the normal cyclic increase at pro-oestrus in the concentration of hypothalamic nuclear oestrogen receptors. Our results therefore show that in the intact adult rat, factors other than the concentration of progesterone or oestradiol determine the nuclear concentration of oestrogen receptors in the uterus. They also demonstrate differences between neural and non-neural tissues in the regulation of oestrogen-receptor interactions.

Uterine progesterone receptor: stabilization and physicochemical alterations produced by sodium molybdate

Incubation of hamster uterine cytosol with millimolar concentrations of sodium molybdate prior to addition of labeled steroid increased recovery of progesterone receptor 2-fold. This stabilizing effect of molybdate was also manifest on gel electrophoresis of the receptor. In the absence of molybdate, no specific [3H]progesterone binding was detectable on polyacrylamide gel electrophoresis. But, in the presence of 5 mM sodium molybdate, a [3H]progesterone-binding species was clearly evident on the gels. The radioactivity associated with this binding was displaceable by unlabeled progesterone but not by cortisol and depended on the concentration of [3H]progesterone employed, suggesting that this binding species is a progesterone receptor. Molybdate treatment produced a small increase in receptor size on low-salt sucrose gradients (from 6-7 to S to 7.5 S). There was no effect of molybdate of receptor sedimentation in the presence of high salt (0.3 M KCl). Further analysis of this phenomenon by gel filtration suggested that this molybdate-mediated increase in receptor size was due to receptor aggregation. In low-salt buffers, molybdate treatment markedly increased the proportion of receptors contained in large aggregates (Stokes radius greater than 8.0 nm). Again, this effect was abolished in the presence of high salt. In conjunction with receptor stabilization, molybdate prevented binding of uterine progesterone receptor to DNA--cellulose. These findings suggest that sodium molybdate stabilizes the unliganded, unactivated form of the receptor. Moreover, these effects seem to be mediated through a direct interaction of molybdate with the receptor, one which results in receptor aggregation.

The relationship of the oestrogen and progestin receptors in the abnormal uterus of the adult anovulatory rat. Effects of neonatal treatment with testosterone propionate or clomiphene citrate

The neonatal administration of testosterone propionate to Wistar rats resulted in anovulatory adults in persistent vaginal oestrus. Clomiphene citrate had a similar effect. In both groups of adults, hyperplasia of the uterine epithelium and occasional metaplasia was observed. The uterine nuclear and cytosol oestrogen and progestin receptors of these anovulatory rats were found to have affinities for their respective ligands similar to those of normal females. The nuclear oestrogen receptor comprised occupied and unoccupied components, as in normal females. The content of the nuclear oestrogen receptor was comparable with that of females in the late dioestrous or pro-oestrous phase. This content was higher in the clomiphene-treated group. Despite the relatively high nuclear oestrogen receptor content the content of progestin receptors, a putative index of the oestrogenic response, was lower in the treated rats than in normal adult females throughout the cycle. Administration of oestradiol to both treatment groups resulted in depletion of cytosol oestrogen receptor content 1 h later, which, however, was not reflected by an increase in the content of nuclear oestrogen receptors. There was no measurable increase in progesterone receptor content in treated rats after daily administration of oestrogen (5 microgram/rat) for 3 days. These changes in sex-hormone-receptor interactions involving an impairment of the normal oestrogenic response may be associated with the abnormal differentiation of the uterus in these sterile, anovulatory animals.

Progesterone regulation of estrogen receptor in the rat uterus: a primary inhibitory influence on the nuclear fraction

The purpose of this study was to determine the short-term effects of progesterone action on estrogen receptor (Re) levels in the rat uterus. Ovariectomized, adrenalectomized rats were maintained on subcutaneous Silastic implants containing crystalline estradiol. Progesterone treatment with serum estradiol maintenance caused a rapid decrease (within 4 h) of total Re, attributable to loss of nuclear Re without a significant change in cytosol Re levels. Removal of estradiol implants resulted in an increase in total Re and cytosol Re at all time periods studied without a significant decrease in nuclear Re until 8 h. Combined estradiol withdrawal and progesterone treatment resulted in lower total Re levels and a more rapid decrease in nuclear Re than with estradiol withdrawal alone. These results demonstrate that progesterone rapidly and selectively decreases nuclear Re levels in rat uterus and suggest that this process is not dependent on cytosol Re or serum estradiol levels.

The unoccupied nuclear oestradiol receptor in the rat uterus and hypothalamus during the oestrous cycle

The nuclear oestrogen receptor population in the rat uterus contained an unoccupied receptor component that bound oestradiol with the high affinity (Kd congruent to 0.5 nM) characteristic of oestrogen receptors. This unoccupied receptor was present at all phases of the oestrous cycle. Its content changed in parallel with that of the total nuclear receptor during the cycle. Oestradiol administration to the immature rat resulted in increases in the uterine content of long-term nuclear receptors (i.e., those still present 8 h after administration); these increases were due to occupied oestrogen receptors, since the content of unoccupied receptor was unchanged. Our previous experiments [White & Lim (1980) Biochem. J. 190, 833-837] have shown in contrast, that oestradiol administration results in an increase in the content of unoccupied nuclear receptor in the hypothalamus. However, as in the uterus, similar cyclic changes in the content of unoccupied nuclear receptor occurred in parallel with those of the total nuclear receptor population in the hypothalamus. Differences and similarities between the unoccupied nuclear receptor of the uterus and hypothalamus are briefly discussed.