Differential in vivo regulation of steroid hormone receptor activation by Cdc37p

The CDC37 gene is essential for the activity of p60(v-src) when expressed in yeast cells. Since the activation pathway for p60(v-src) and steroid hormone receptors is similar, the present study analyzed the hormone-dependent transactivation by androgen receptors and glucocorticoid receptors in yeast cells expressing a mutant version of the CDC37 gene. In this mutant, hormone-dependent transactivation by androgen receptors was defective at both permissive and restrictive temperatures, although transactivation by glucocorticoid receptors was mildly defective only at the restrictive temperature. Cdc37p appears to function via the androgen receptor ligand-binding domain, although it does not influence receptor hormone-binding affinity. Models for Cdc37p regulation of steroid hormone receptors are discussed.

Development and characterization of a conditionally immortalized human osteoblastic cell line stably transfected with the human androgen receptor gene

Androgens have significant beneficial effects on the skeleton. However, studies on the effects of androgens on osteoblasts are limited due to the absence of appropriate model systems that combine completeness of the osteoblastic phenotype, rapid proliferation rate, and stable expression of the androgen receptor (AR). Thus, we stably transfected the conditionally immortalized human fetal osteoblastic cell line (hFOB) with the human wild-type AR (hAR) cDNA. Compared to nontransfected hFOB cells, constitutive hAR mRNA expression in three independent hAR-transfected hFOB clones (hFOB/AR) was 15-fold higher in hFOB/AR-16, 62-fold higher in hFOB/AR-2, and 72-fold higher in hFOB/AR-6 cells, respectively, as assessed by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Detectable constitutive levels of hAR mRNA by Northern blot analysis were present in hFOB/AR-2 and hFOB/AR-6 cells, but not in hFOB/AR-16 or hFOB cells, respectively. Treatment with 5 alpha-dihydrotestosterone (5 alpha-DHT) (10(-8) M) for 24 h did not alter hAR mRNA steady state levels in the hFOB/AR cell lines. Nuclear binding studies demonstrated 152 +/- 73 (mean +/- SEM) functional hARs/nucleus in non-transfected hFOB cells, 3,940 +/- 395 functional hARs/nucleus in hFOB/AR-2 cells, and 3,987 +/- 823 hARs/nucleus in hFOB/AR-6 cells, respectively. Treatment with 5 alpha-DHT increased the expression of a transiently transfected androgen response element-chloramphenicol acetyltransferase (ARE-CAT) reporter construct in hFOB/AR-6 cells in a dose- and time-dependent manner; no such effect was observed in transiently transfected hFOB cells lacking exogenously transfected hARs. Moreover, 5 alpha-DHT-induced ARE-CAT expression was inhibited by the selective androgen receptor antagonist, hydroxyflutamide. In summary, we have developed and characterized androgen-responsive osteoblastic cell lines derived from normal human fetal bone that express physiological levels of functional hARs. These cell lines should provide a suitable model for further studies on the effects of androgens on osteoblast function, including the identification of potential androgen-regulated growth factors and cytokines.

Interaction of mouse placental lactogens and androgens in regulating progesterone release in cultured mouse luteal cells

Pituitary hormones are essential for the maintenance of the corpus luteum in the pregnant mouse during the first half of gestation. Thereafter, hormones from the placenta take over the luteotropic role of the pituitary hormones. Mouse placental lactogen-I (mPL-I) and mPL-II, two PRL-like hormones produced in the placenta, are probably necessary for the maintenance of the corpus luteum in the latter half of pregnancy. A culture system of luteal cells from pregnant mice was developed to investigate the role of hormones from the placenta that may be important for the function of the corpus luteum. Mice were killed on days 10, 14, and 18 of pregnancy, and the corpora lutea were excised from the ovaries and digested in 0.1% collagenase, 0.002% DNase for 1 h. The resulting luteal cell suspension was plated onto 96-well plates coated with fibronectin (1 x 10(5) cells/well) and cultured for 1-3 days. Medium was changed daily. The cells were treated with various concentrations and combinations of mPL-I, mPL-II, mouse PRL, androstenedione, dihydrotestosterone, 17beta-estradiol (E2), testosterone, hydroxyflutamide, cycloheximide, actinomycin D, and fadrozole to study the effects of these different treatments on progesterone (P4) production. The three lactogens (mPL-I, mPL-II, and mouse PRL) all stimulated the release of P4 from the luteal cells. The potency of the lactogens was similar and did not depend on the stage of pregnancy at which the luteal tissue was obtained. However, the responsiveness of the cells to all hormone-stimulated P4 release was gradually reduced the later in pregnancy the tissue was collected. Androgens also stimulated the release of P4 from the luteal cells, and when administered together, the lactogens and the androgens acted synergistically to stimulate P4 release. The androgens acted directly but not through conversion to E2, as determined by the findings that 1) the effects of the androgens could not be reproduced by E2 administration, 2) nonaromatizable androgen dihydrotestosterone was as effective as aromatizable androgens, and 3) aromatase inhibitor did not prevent the action of the androgens to stimulate the P4 release. The effect of the androgens on the P4 release was rapid, occurring within 15 min of hormone administration. It was not prevented by inhibitors of protein and RNA synthesis, and the intracellular androgen receptor antagonist hydroxyflutamide did not affect the androgen action. Therefore, the androgen effects were not mediated through the intracellular androgen receptor and de novo protein synthesis was not needed for androgen-stimulated P4 release.

Functional characterization of mutant androgen receptors from androgen-independent prostate cancer

Mutations in the androgen receptor (AR), that alter steroid hormone specificity have been identified in a series of androgen-independent prostate cancers. To address the functional properties of these mutant ARs that may have contributed to their selection in vivo, responses to a series of steroid hormones and antiandrogens were assessed. CV-1 cells were cotransfected with wild-type or mutant ARs and a luciferase reporter plasmid regulated by an androgen-responsive element. Dose-response curves were analyzed for 5alpha-dihydrotestosterone, the most active androgen in normal prostate, and androstenedione, a major androgen derived from the adrenals. Although the mutant ARs responded to both of these steroids, the responses were equivalent to or less than the wild-type AR. In contrast, responses to flutamide, a competitive antagonist of the wild-type AR, were markedly increased by three of the mutations. Similar responses were observed with a second antiandrogen, nilutamide. Bicalutamide, another antiandrogen related to flutamide, remained an antagonist for these mutant ARs. Finally, flutamide was observed to be a weak partial agonist of the wild-type AR in this system. These results indicate that flutamide used in conjunction with androgen ablation therapy for prostate cancer may select for tumor cells with flutamide-inducible ARs.

Synergistic activation of androgen receptor by androgen and luteinizing hormone-releasing hormone in prostatic carcinoma cells

BACKGROUND

We investigated modulation of androgen receptor (AR) activity in prostatic tumor cells by luteinizing hormone-releasing hormone (LHRH)-induced increase of the intracellular cyclic adenosine monophosphate (cAMP) level.

METHODS

AR transactivation activity was assessed in transiently transfected DU-145 and in LNCaP cells.

RESULTS

LHRH and cAMP derivative, respectively, induced reporter gene activity to about 15% of the maximal level in DU-145 cells transfected with an AR expression vector and an androgen-inducible reporter gene. LHRH or the cAMP analogue acted synergistically in combination with low concentrations of androgen thus lowering the androgen concentration required for maximal AR activation by a factor of 100. A similar activation of the AR by cAMP analogue was observed in LNCaP cells when enhancement of androgen-induced secretion of prostate-specific antigen was determined. The two nonsteroidal antiandrogens hydroxyflutamide and Casodex(R) inhibited reporter gene activity.

CONCLUSIONS

The AR is synergistically activated by low doses of androgen and LHRH or the second messenger cAMP. This may have implications for the treatment of advanced prostate cancer.

Concerted stimulation of rat granulosa cell deoxyribonucleic acid synthesis by sex steroids and follicle-stimulating hormone

Although follicle-stimulating hormone (FSH) and estrogens are known to be the main physiological stimuli for the development of the ovarian follicle in mammals, their growth-promoting activity has not been clearly established "in vitro". Furthermore, experimental evidence indicates that FSH and estradiol can independently inhibit granulosa cell proliferation. The present study was aimed at examining the effect of sex steroids in combination with FSH, on DNA synthesis in rat granulosa cells cultured in completely defined medium. Estradiol and FSH, when added separately, produced a significant inhibition of [3H] thymidine incorporation. In contrast, a combination of a low dose of FSH (20 ng/ml) with estradiol (100 ng/ml) produced a shift in the period of maximal DNA synthesis from 96 to 48 h after plating. Dose response studies showed that estradiol effects were produced at physiological intraovarian concentrations (1-100 ng/ml), whereas the effects of FSH were biphasic, with high doses (200 ng/ml) being inhibitory. A similar biphasic dose response curve was observed with increasing concentrations of a cAMP derivative in the presence of maximally effective doses of either an aromatizable steroid (androstenedione), insulin or insulin-like growth factor I. Non-aromatizable androgens (5alpha-dihydrotestosterone, 5alpha-androstane 3alpha-17beta diol and androsterone) showed a potency comparable to that of estradiol. The effect of 5alpha-dihydrotestosterone was completely blocked by a specific antiandrogen (hydroxy-flutamide), indicating that it was mediated by the androgen receptor. The effects of estradiol and androgens were not additive. The interaction between estradiol and FSH was further amplified in the presence of a maximally effective dose of insulin. Data presented herein indicate that both estrogens and androgens are able to elicit a mitogenic response in purified granulosa cells, cultured in a completely defined medium, provided the cells are stimulated by a physiological dose of FSH. These results suggest that, during follicular development, the stimulus for granulosa cell proliferation is given by the concerted action of steroid and peptide hormones acting through different signalling pathways.

Estrogenic and progestagenic activities of physiologic and synthetic androgens, as measured by in vitro bioassays

Estrogenic activities of testosterone (T) and 5a-dihydrotestosterone (DHT) were detected and measured by using their specific stimulatory effects on alkaline phosphatase (AP) activity in human endometrial adenocarcinoma cells of the Ishikawa Var-1 line. These two physiologic androgens were able to induce, at microM concentrations, estrogenic effect believed to be mediated by the estrogen receptor (ER) since the antiestrogens ICI-164384 and 4-hydroxytamoxifen (OHTam), but not the antiandrogens hydroxyflutamide (OHFl) or cyproterone acetate (CPA), reversed that effect. By using another in vitro bioassay, based on the progestin-specific stimulation of AP activity in cells of the T47D human breast cancer line, progestagenic activity was detected and measured in T, DHT and three synthetic androgens: nandrolone (19-nortestosterone). 7 alpha-methyl 19-nortestosterone (MENT) and mibolerone (7 alpha, 17 alpha-dimethyl 19-nortestosterone) (DMNT). While progestagenic effects of T and DHT required relatively high concentrations (microM levels), the synthetic androgens stimulated AP activity at nM or pM levels. These effects seem to be mediated by the progesterone receptor (PR), since they are completely abolished by the antiprogestins RU-486, ZK-98299 and ZK-112993, but not by the antiandrogen OHFl. These simple in vitro bioassays, expressing biological effects of the test compounds in human cells in culture, revealed dual or multiple hormonal activities coexisting in a single compound and provide quantitative information of considerable pharmacological importance concerning the complex actions of drugs.

Dehydroepiandrosterone activates mutant androgen receptors expressed in the androgen-dependent human prostate cancer xenograft CWR22 and LNCaP cells

An androgen receptor (AR) gene mutation identified in the androgen-dependent human prostate cancer xenograft, CWR22, changed codon 874 in the ligand-binding domain (exon H) from CAT for histidine to TAT for tyrosine and abolished a restriction site for the endonuclease SfaNI. SfaNI digestion of AR exon H DNA from normal but not from prostate cancer tissue indicated H874Y is a somatic mutation that occurred before the initial tumor transplant. CWR22, an epithelial cell tumor, expresses a 9.6-kb AR mRNA similar in size to the AR mRNA in human benign prostatic hyperplasia. AR protein is present in cell nuclei by immunostaining as in other androgen-responsive tissues. Transcriptional activity of recombinant H874Y transiently expressed in CV1 cells in the presence of testosterone or dihydrotestosterone was similar to that of wild type AR. With dihydrotestosterone at a near physiological concentration (0.01 nM), H874Y and wild type AR induced 2-fold greater luciferase activity than did the LNCaP mutant AR T877A. The adrenal androgen, dehydroepiandrosterone (10 and 100 nM) with H874Y stimulated a 3- to 8-fold greater response than with wild type AR and at 100 nM the response was similar with the LNCaP mutant. H874Y, like the LNCaP cell mutant, was more responsive to estradiol and progesterone than was wild type AR. The antiandrogen hydroxyflutamide (10 nM) had greater agonist activity (4- to 7-fold) with both mutant ARs than with wild type AR. AR mutations that alter ligand specificity may influence tumor progression subsequent to androgen withdrawal by making the AR more responsive to adrenal androgens or antiandrogens.

Comparison of in vitro effects of the pure antiandrogens OH-flutamide, Casodex, and nilutamide on androgen-sensitive parameters

OBJECTIVES

A combination of flutamide (Eulexin) or nilutamide (Anandron) with a luteinizing hormone-releasing hormone (LHRH) agonist or orchiectomy is the only therapy demonstrated to prolong life in prostate cancer. Recently, the low 50-mg daily dose of Casodex, an analogue of the pure antiandrogen flutamide, was chosen for clinical studies on the basis that the compound was 5 to 10 times more potent than flutamide, as suggested by data obtained in the inappropriate intact rat model. The present study was designed to compare the in vitro antiandrogenic activity of OH-flutamide (OH-FLU), the active metabolite of flutamide, Casodex, and nilutamide.

METHODS

The effect of the antiandrogens was tested on two androgen-sensitive parameters, namely proliferation of the SEM-107 clone of Shionogi mouse mammary tumor cells and secretion of the GCDFP-15 (gross cystic disease fluid protein 15 kDa) in T-47D and ZR-75-1 human breast cancer cells.

RESULTS

The twofold stimulation of Shionogi cell proliferation caused by a 10-day exposure to 1 nM testosterone was competitively reversed by incubation with OH-FLU, Casodex, or nilutamide, at the respective IC50 values of 72, 243, and 412 nM. Moreover, the marked increase in GCDFP-15 release induced by 1 nM testosterone was blocked by OH-FLU. Casodex, or nilutamide at respective IC50 values of 29, 180, and 87 nM in T-47D cells and at 35, 142, and 75 nM in ZR-75-1 cells. Similar data were detected in 4-androstenedione-induced Shionogi cell proliferation and in dihydrotestosterone-induced GCDFP-15 secretion in T-47D cells.

CONCLUSIONS

OH-FLU is 3.1- to 7.8-fold more potent than Casodex, as measured on two in vitro androgen-sensitive parameters, in agreement with our recent in vivo data obtained in the model of castrated rats supplemented with 4-androstenedione implants, in which threefold greater potency of flutamide was observed. The present data, as well as other data from the literature, strongly indicate the need to choose a more appropriate dose of Casodex for the treatment of prostate cancer.

Androgen-induced inhibition of proliferation in human breast cancer MCF7 cells transfected with androgen receptor

Sex steroids control the proliferation of their target cells through two different pathways: 1) proliferative response (Step-1); and 2) inhibition of cell proliferation (Step-2). Mechanisms of cell proliferation regulation are incompletely understood; however, there is general agreement with the notion that sex steroid receptors play an important role in the control of the proliferation of sex steroid target cells. To test this hypothesis, a full human androgen receptor (AR) vector was transfected into human breast cancer MCF7 cells. The cloned cells that stably express the AR, called MCF7-AR1 cells, contained approximately five times more AR than the wild-type MCF7 cells from which they were derived. These AR-transfected cells retained their capacity to proliferate when estrogens were added to 10% charcoal-dextran stripped human serum but did not acquire the ability to proliferate when androgens were added to this medium. In serumless medium (ITDME), these cells proliferated maximally, as MCF7 cells did; however, natural and synthetic androgens prevented the AR-transfected cells from proliferating. Inhibition of cell proliferation occurred when physiological androgen concentrations (1 nM) were added to ITDME; this effect was almost completely reversed by Casodex, a synthetic androgen antagonist. Under the effect of androgens added to ITDME, MCF7-AR1 cells were arrested in the G0/G1 phase within 24 h. These data suggest that: 1) the androgen-induced inhibition of cell proliferation (Step-2) is AR-mediated; and 2) the AR may be necessary, but not sufficient, to mediate the androgen-induced proliferative response (Step-1).

Evaluation of chemicals with endocrine modulating activity in a yeast-based steroid hormone receptor gene transcription assay

There is a concern that chemicals in our environment are affecting human health by disrupting normal endocrine function. Much of the concern has focused on chemicals that can interact directly with steroid hormone receptors. We have used a yeast-based assay to assess chemical interactions with the estrogen, androgen, and progesterone receptors. The yeast transformants used in this study contained the human estrogen, androgen, or progesterone receptor along with the appropriate steroid responsive elements upstream of the beta-galactosidase reporter gene. Chemicals were added to yeast cultures in doses ranging from 10(-12) to 10(-4) M and following incubation, the yeasts were then lysed and assayed for beta-galactosidase activity. Diethylstilbesterol and 17-beta estradiol were most active in the estrogen receptor assay, followed by the phytoestrogen, coumestrol. p-Nonylphenol and bisphenol A were approximately 5000- and 15,000-fold less active, respectively, than estradiol. Methoxychlor, DDT and its metabolites, o,p'-DDD, and o,p'-DDE ranged in potency from 5 to 24 X 10(6) less potent than estradiol. Testosterone and dihydrotestosterone were most potent in the androgen receptor assay, followed by estradiol and progesterone. p,p'-DDE was approximately 10(6)-fold less potent than testosterone. None of the industrial chemicals tested interacted with the progesterone receptor. These data demonstrate the utility of using yeast-based receptor assays for detecting chemical interaction with steroid receptors and these assays should serve as a useful component of an in vitro-in vivo strategy to assess the effects of chemicals on endocrine function.

Non-steroidal L-245,976 acts as a classical antiandrogen in vitro

Non-steroidal antiandrogens have been employed in the management of prostate cancer, but the mechanism of action is unclear due to a lack of good tissue culture models. The growth of a hamster ductus deferens cell line (DDT1) is highly dependent upon the addition of 10 nM testosterone to synthetic serum-free media. We describe a non-steroidal compound N-(4-chlorophenyl)-(Z,Z)-2,3-bis(-cyclopropylmethylene) cyclopentanecarboxamide (L-245976) which antagonizes the action of testosterone on DDT1 cells at 10 microM but exhibits little or no effect on cell growth by itself. This compound also blocks the binding of 3H-dihydrotestosterone (DHT) to the human androgen receptor (AR) with an IC50 of approximately 28 microM. In addition, L-245976 was found to antagonize DHT-dependent transactivation of the AR via the probasin gene promoter at comparable doses with no agonist activity.

Androgen independence of primary epithelial cultures of the prostate is associated with a down-regulation of androgen receptor gene expression

BACKGROUND

Epithelial cells cultured from prostatic acini do not demonstrate significant (P > 0.05) growth response to the testosterone metabolite dihydrotestosterone (DHT) at concentrations of 0.001-10.0 nM. In addition, the nonsteroidal antiandrogen hydroxyflutamide (HO-F) does not influence primary epithelial cell proliferation in this concentration range.

METHODS

Northern blotting carried out with an androgen reception (AR)-specific cDNA probe indicated that the extent of AR gene expression in six unpassaged primary prostatic epithelial cell cultures was insufficient to elicit a detectable signal upon autoradiography. However, RT/PCR analysis of total RNA using two sets of intron-spanning androgen receptor (AR) primers demonstrates the presence of full-length receptor transcripts in two BPH-derived epithelial cell cultures (BPH1 and BPH2) as well as a carcinoma-derived culture (CaP1).

RESULTS

AR-positive LNCaP cells transfected with the AR reporter plasmid pMMTV/SPAP exhibit significant increases (P < 0.05) in SPAP production upon treatment with DHT. pMMTV/SPAP-transfected primary epithelial cells exhibit no such response when pulsed with either androgen or anti-androgen.

CONCLUSIONS

These results indicate that the lack of significant AR gene expression underlies the androgen independence of primary prostatic epithelial cell cultures.

Hsp90 regulates androgen receptor hormone binding affinity in vivo

The regulation of human androgen receptor (AR) by the molecular chaperone Hsp90 was investigated using the yeast Saccharomyces cerevisiae as a model system. These studies were performed in strains expressing a conditional temperature-sensitive mutant allele of the hsp82 gene, which encodes Hsp90 protein. At the restrictive temperature in the mutant, there is a decrease in hormone-dependent transactivation by the AR, although steady state levels of AR protein are unchanged. Quantitative hormone binding studies at the permissive temperature revealed the presence of both high affinity and low affinity hormone binding states. At the restrictive temperature in the hsp82 mutant, the high affinity state was abolished, and only the low affinity state was observed. The change in hormone binding affinity was further investigated by a competition assay with the anti-androgen hydroxyflutamide. Under permissive conditions, hydroxyflutamide competes poorly for the synthetic androgen R1881, but under restrictive conditions in the hsp82 mutant strain, hydroxyflutamide was shown to be a potent competitive inhibitor. Our findings indicate that Hsp90 participates in the activation process by maintaining apoAR in a high affinity ligand binding conformation which is important for efficient response to hormone.

Antiandrogen microimplants into the rostral medial preoptic area decrease gamma-aminobutyric acidergic neuronal activity and increase luteinizing hormone secretion in the intact male rat

gamma-Aminobutyric acid (GABA)ergic neurons terminating in the rostral hypothalamus are stimulated by testosterone. To investigate whether this action is mediated locally through androgen receptors in the rostral hypothalamus, bilateral microcannulas (28 gauge) containing the androgen receptor antagonist, hydroxyflutamide (HF), were stereotaxically implanted into the rostral medial preoptic area (rMPA) just dorsal to the major population of GnRH cell bodies. Two days later, blood samples were collected for assay of LH, and animals were killed for determination of GABAergic neuronal activity in tissue dissected from the site of the implanted cannulas. Animals were decapitated either without treatment or 60 min after inhibition of GABA degradation by aminooxyacetic acid (100 mg/kg, ip). The rate of GABA accumulation in the tissue after aminooxyacetic acid treatment was used as a measure of GABA turnover. Levels of messenger RNA for both forms of glutamic acid decarboxylase (GAD65 and GAD67), the rate-limiting enzyme responsible for GABA synthesis also were measured by a microlysate ribonuclease protection assay. LH levels were significantly increased (1.8-fold) in HF-treated animals compared with controls. In the MPA, beneath the implant cannulas, GABA turnover was significantly reduced in HF-treated rats. There was no effect of treatment in the frontal cortex, which was used as a control region. Surprisingly, levels of messenger RNA for both GAD65 and GAD67 were significantly increased in HF-treated rats. The results indicate that GABAergic neurons terminating in the rostral hypothalamus are tonically stimulated by testosterone acting by means of androgen receptors localized in this region. These findings support the working hypothesis that androgen-sensitive GABAergic neurons in the rMPA mediate the negative feedback action of testosterone on GnRH secretion in the male rat.

Inhibition of male sex behavior by androgen receptor blockade in preoptic area or hypothalamus, but not amygdala or septum

Inhibition of masculine copulatory behavior was previously demonstrated following systemic injections of hydroxyflutamide (OHF). In the present study, we examined the localization of the effects of this androgen receptor blocker by direct intracranial implantation of OHF into the medial preoptic area (MPOA), ventromedial nucleus of hypothalamus (VMN), medial amygdala (AME), and lateral septum (SEPT). Animals were implanted intracranially with crystalline OHF or cholesterol, and at the same time received two 10-mm testosterone-filled Silastic capsules SC. Tests for restoration of copulatory behavior were initiated 3 days later, and conducted twice weekly for 2 weeks. Implants of OHF into the MPOA were effective in preventing restoration of male sexual behavior. However, the most effective site was the VMN. Implants of OHF into the AME were only partially effective in stimulating male sexual behavior, whereas implants into the SEPT had no effect. The OHF was discontinued and 1 week later males were retested for sexual behavior. The majority of these animals ejaculated, indicating, that the effects of OHF are reversible. The result of this study demonstrate that the functional integrity of androgen receptors in some, but not all, androgen-concentrating brain loci is necessary for the expression of the complete pattern of male sexual behavior. These data lend support to the view that androgen receptor populations in specific brain loci differentially express proteins involved in mediating the masculine copulatory response.

Regulation by gonadotropins of the messenger ribonucleic acid for P450 side-chain cleavage, P450(17) alpha-hydroxylase/C17,20-lyase, and 3 beta-hydroxysteroid dehydrogenase in cultured pig Leydig cells

The Leydig cell from the immature pig provides a good model for studying testicular steroidogenesis. Regulation of the enzymes involved, which has been well studied in rodents, has not been characterized in the pig. The objectives of this study were to examine the regulation of three steroidogenic enzymes in pig Leydig cells by LH/hCG and testosterone. The mRNA for P450 side-chain cleavage and P450(17) alpha-hydroxylase/C17-20-lyase, although constitutively expressed, decreased over time in culture, while that for 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) remained relatively constant. The mRNA for all three enzymes was increased in a dose- and time-dependent manner by treatment with hCG. Run-on experiments demonstrated that the main effect of the hormone was at the level of transcription. Treatment with hydroxyflutamide, either alone or in combination with hCG, had no effect on the mRNA for these enzymes. Treatment with hCG plus aminoglutethimide, an inhibitor of steroidogenesis, had no effect on the mRNA for the two P450 enzymes, but resulted in an increase in mRNA for 3 beta HSD when compared to treatment with hCG alone. However, exogenous testosterone could not block the effect of aminoglutethimide. Therefore, the steroidal regulation of 3 beta HSD in pig Leydig cells may act through a mechanism separate from the androgen receptor. While aspects of the regulation of these enzymes are similar to those seen in rodents, some significant differences exist. Our results support the concept that regulation of steroidogenic enzymes in Leydig cells is species-specific.

Cloning and characterization of a specific coactivator, ARA70, for the androgen receptor in human prostate cells

The androgen receptor (AR) is a member of the steroid receptor superfamily that plays an important role in male sexual differentiation and prostate cell proliferation. Mutations or abnormal expression of AR in prostate cancer can play a key role in the process that changes prostate cancer from androgen-dependent to an androgen-independent stage. Using a yeast two-hybrid system, we were able to isolate a ligand-dependent AR-associated protein (ARA70), which functions as an activator to enhance AR transcriptional activity 10-fold in the presence of 10(-10) M dihydrotestosterone or 10(-9) M testosterone, but not 10(-6) M hydroxyflutamide in human prostate cancer DU145 cells. Our data further indicated that ARA70 Will only slightly induce the transcriptional activity of other steroid receptors such as estrogen receptor, glucocorticoid receptor, and progesterone receptor in DU145 cells. Together, these data suggest that AR may need a specific coactivator(s) such as ARA70 for optimal androgen activity.

Androgen-like and anti-androgen-like effects of antiprogestins in human mammary cancer cells

In addition to their antiprogestational activity, the antiprogestins RU486, ZK98.299 and ZK98.734 possess varying antiglucocorticoid as well as androgen-like or antiandrogen-like properties in human mammary cancer cells. The human mammary cancer cell line MFM-223, which contains only androgen receptors, was used as a model to investigate androgen receptor mediated effects of these antiprogestins. Proliferation of MFM-223 cells is inhibited by androgens and does not respond to oestrogens, progestins and glucocorticoids. As shown in proliferation assays, ZK98.734 was a strong inhibitor of cell proliferation. This effect was antagonised by the antiandrogen hydroxyflutamide. ZK98.734 was found to displace [3H]R1881 from the androgen receptor in MFM-223 cells, substantiating the involvement of the androgen receptor. The antiprogestin ZK98.299 failed to influence the proliferation of MFM-223 cells. ZK98.299 did not bind to the androgen receptor and was devoid of androgenic or antiandrogenic activity. RU486 bound to the androgen receptor. It was a weak inhibitor of MFM-223 cell proliferation, but the inhibition of proliferation by RU486 was not antagonised by hydroxyflutamide. This effect was probably not mediated by the androgen receptor. RU486 had antiandrogenic activity in this cell line, as it antagonised the inhibitory effect of dihydrotestosterone at a 100-molar excess. These results were confirmed by transfection experiments with an MMTV-CAT construct in the same cell line, demonstrating the biological function of the ZK98.734-androgen receptor complex. ZK98.299 and RU486 were not able to induce CAT activity. The different androgenic or antiandrogenic properties of the antiprogestins investigated should be considered when selecting antiprogestational properties of the antiprogestins investigated should be considered when selecting antiprogestational compounds for clinical applications, as a partial androgenic activity may be of benefit in breast cancer but can have undesired side-effects in other diseases.

[Does interferon-alpha enhance the effect of tamoxifen-medroxyprogesterone acetate and hydroxyflutamide on in vitro tumor cells?]

In our laboratory the influence of tamoxifen, medroxyprogesterone acetate (MPA) and hydroxyflutamid with and without interferon alpha (IFN) was tested on the proliferative capacity of two breast and one ovarian cancer cell line and three ovarian cancer tissues in the colony assay described by Hamburger and Salmon. The following results were seen: 1. Testing the four drugs alone in 6 different cell cultures, in vitro growth inhibition of more than 30% was seen 3 respectively 4 times. Growth inhibition of more than 50% could be shown only in particular cases. The higher dose of an active substance led up to three times more in comparison to the set growth restraint than the smaller dose. A reaction depending on the concentration was seen. 2. The combination of IFN and tamoxifen could not really increase the antiproliferative capacity of each substance alone. Nevertheless we were able to show a significant augmentation of the cell-growth inhibiting effect of MPA or hydroxyflutamid when it was given together with IFN: the increased antitumor activity was evident if cells were tested which showed progesterone-(PR) or androgenereceptors (AR). The results indicate that positive interactions of IFN and MPA or IFN and hydroxyflutamid are possible. Although an augmentation of the activity of tamoxyfen by IFN was not found it should be stressed that the schedule of treatment seems to be clearly critical.

Androstenedione increases thromboxane A2 receptors in human erythroleukemia cells

Previous studies have demonstrated an increased thromboxane A2 (TXA2) receptor expression in human erythroleukemia (HEL) cells and rat aortic smooth muscle (RASM) cells in response to testosterone treatment. HEL cells have served as a model for megakaryocytes, the progenitor cell for platelets. Platelets have previously been shown to convert androstenedione to testosterone. This study investigated the effects of androstenedione on the TXA2 receptor density in HEL and cultured RASM cells. Both cell lines were incubated with vehicle, 150 nM testosterone or 250, 500 or 750nM androstenedione for 48 hours. Co-incubation with testosterone or androstenedione significantly (p<0.05) increased the maximum number of TXA2 binding sites (Bmax) in HEL cells compared to controls. There was no significant change in Kd values. In a separate series of experiments, HEL cells were incubated with the androgen receptor antagonist hydroxyflutamide (2.5mM). Treatment with androstenedione (500nM) significantly (p<0.05) increased the Bmax value by 35% compared to control and hydroxyflutamide completely antagonized this effect of androstenedione. Incubation with hydroxyflutamide alone had no effect on the Bmax values compared to control. RASM cells also showed an increase in Bmax values by 25% and 23% over control (95+/-6.6, 118+/-7.2 and 117+/-5.1 fmoles/mg protein, control, testosterone and androstenedione, n=3). Both cell lines converted androstenedione to testosterone. The results raise the possibility that the adrenal androgen, androstenedione can regulate the expression of TXA2 receptors either on its own or via conversion to testosterone and through an androgen receptor.

Androgen and glucocorticoid regulation of androgen receptor cDNA expression

Androgen receptor (AR) levels are regulated by androgens, other steroids and non-steroidal hormones via complex, tissue-specific processes. Since alterations in receptor levels may influence cellular sensitivity to androgens, understanding AR regulation is of fundamental and potentially therapeutic significance. In most target tissues and AR-containing cell lines, AR mRNA is down-regulated in response to androgens. We have reconstituted this androgen-mediated down-regulation of AR mRNA in COS 1 cells transfected with a human AR cDNA under the control of the cytomegalovirus (CMV) promoter. The sequences mediating receptor mRNA down-regulation are represented within the AR cDNA and not within the CMV promoter. Androgenic down-regulation of AR cDNA expression was time- and dose-dependent, resembling native AR mRNA down-regulation. In addition, androgenic regulation of the receptor cDNA was not dependent on protein synthesis suggesting that AR and/or another pre-existing protein(s) is involved in this process. In COS 1 cells co-transfected with androgen and glucocorticoid receptor cDNAs, dexamethasone mimicked the action of androgen in down-regulating AR mRNA. This response depended on glucocorticoid receptors. Androgen had little effect on steady-state levels of AR protein consistent with reports that androgen down-regulates AR mRNA but increases AR protein half-life (Kemppainen et al. (1992) J. Biol. Chem. 267, 968-974; Zhou et al. (1995) Mol. Endocrinol. 9, 208-218). However, glucocorticoids decreased AR protein levels in cells that co-expressed androgen and glucocorticoid receptors. These results indicate that sequences represented in the AR cDNA mediate AR mRNA down-regulation by both androgens and glucocorticoids. Inhibition of AR mRNA and protein by glucocorticoids suggests that these steroids may modulate androgen action in tissues, such as mammary gland and prostate, which express both androgen and glucocorticoid receptors.

Inhibitory effect of hydroxyflutamide plus tamoxifen on oestradiol-induced growth of MCF-7 breast cancer cells

The antiandrogen flutamide has been reported to exert antiproliferative actions on breast cancer both in vitro and in vivo. Here we study the action of its active metabolite hydroxyflutamide on the oestradiol-induced growth of MCF-7 breast cancer cells. The results show that the antiandrogen inhibits the cell growth. Moreover hydroxyflutamide adds its antiproliferative effect to the action of the antioestrogen tamoxifen. The inhibitory effect is dose-dependent and it is unaffected by tamoxifen concentrations up to levels able to block oestrogen receptors completely. Dihydrotestosterone experiments parallel those on hydroxyflutamide. When the two substances are administered together, neither antagonistic nor additive effects are appreciable. Data are consistent with an androgen-like action of hydroxyflutamide on breast cancer cells. The antiproliferative effect of hydroxyflutamide, without virilizing side-effects, suggests that it is worth exploring its possible employment together with antioestrogens in the treatment of breast cancer patients.

Mutant androgen receptors in prostatic tumors distinguish between amino-acid-sequence requirements for transactivation and ligand binding

Mutant androgen receptors are thought to contribute to hormone resistance in prostate carcinoma. The part they play in this process, however, is ill-defined. Here we report on transactivation by 2 mutant androgen receptors from prostatic tumors with single amino-acid exchanges in their hormone-binding domains. These exchanges enhance the transactivation property of the receptors, particularly to androsterone and androstanediol, 2 metabolized derivatives of testosterone present in the prostate. Additionally, they enhance the transactivation potential of the mutant receptors to hydroxyflutamide, an anti-androgen frequently used in hormone ablation therapy. The increased transactivation by the mutant receptors did not result from altered affinity of the receptors to the inducing ligands nor from measurable changes in conformation of the liganded receptors. Thus the single amino-acid exchanges identify differences in amino-acid-sequence requirements for transactivation and ligand binding in the hormone-binding domain of the androgen receptor. These results provide new insights into ligand-dependent transactivation, and form a framework for the search for effective antagonists to be used in prostate-cancer therapy.

Dihydrotestosterone affects the growth of hormone-unresponsive breast cancer cells: an indirect action

Cell to cell interaction, which plays a crucial role in breast cancer growth, may be regulated by steroid hormones. This study examined dihydrotestosterone (DHT) effects on the interaction between the steroid receptor positive MCF-7 and the steroid receptor negative MDA-MB-231 breast cancer cell lines. The growth of MDA-MB-231 cells was inhibited by medium conditioned by MCF-7 cells grown in presence of DHT but not by medium conditioned by MCF-7 cells grown in presence of both DHT and the antiandrogen hydroxyflutamide. Trypsin pretreatment of conditioned medium abolished its growth-inhibitory effect on hormone-unresponsive cells. DHT itself did not affect the growth of MDA-MB-231 cells when directly added to their culture medium. Data suggest that DHT stimulates, via the androgen receptor, the androgen-responsive breast cancer cells to produce a peptide factor(s) capable of inhibiting the growth of hormone-unresponsive cells.

Effects of short-term exposure to hydroxyflutamide in utero on the development of the reproductive tract in male mice

To determine if and when short-term ablation of androgen action compromises the development of the male reproductive tract in mice, the androgen receptor antagonist hydroxyflutamide was administered orally to pregnant FVB/N mice and the reproductive tracts of the male offspring were examined when adult. Hydroxyflutamide (30 mg per day) for 5 days from day 11 to day 15 of gestation caused hypospadias in all male progeny. However, testis weights, seminal vesicle weights, and serum testosterone levels were not affected (p > 0.05) but caput-corpus epididymal weights were 15% lower than controls (p < 0.02). Shorter periods of treatment that included day 14 or 15 caused hypospadias, but treatments that did not include days 14 and 15 did not (p < 0.002). Hydroxyflutamide (30 mg, once or twice daily for 2 consecutive days) between days 15 and 20 of gestation demonstrated that androgen ablation on days 15 & 16 caused hypospadias, absence of prostate, and scrotal location of the seminal vesicles with abdominal testes (p < 0.05). Males exposed later in pregnancy had prostates, but the weights were reduced (p < 0.001); testes were scrotal and seminal vesicles were abdominal; caput-corpus epididymal weights were 15-30% lower than controls (p < 0.05), but the tubule contained large numbers of spermatozoa. Furthermore, testis weights, serum testosterone, and the response of the testis to a human chorionic gonadotropin (hCG) challenge in vitro were not compromised by hydroxyflutamide, and seminiferous tubules exhibited normal spermatogenesis. When males that had been exposed to hydroxyflutamide on days 13 & 14, 15 & 16, 17 & 18 and 19 & 20 were housed with sexually mature females, pregnancies resulted only from the day 19 & 20 treatment group. Thus, there are long-term effects caused by short-term blockade of androgen action at critical times during pregnancy and such effects could result in the inability to impregnate, irrespective of any externally visible indications of developmental anomalies.

Androgen receptor antagonist versus agonist activities of the fungicide vinclozolin relative to hydroxyflutamide

The mechanism of antiandrogenic activity of vinclozolin (3-(3,5-dichlorophenyl)-5-methyl-5-vinyloxazolidine-2,4-dione), a dicarboximide fungicide under investigation for its potential adverse effects on human male reproduction, was investigated using recombinant human androgen receptor (AR). The two primary metabolites of vinclozolin in plants and mammals are M1 (2-[[3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid) and M2 (3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide). Both metabolites, in a dose-dependent manner, target AR to the nucleus and inhibit androgen-induced transactivation mediated by the mouse mammary tumor virus promoter. M2 is a 50-fold more potent inhibitor than M1 and only 2-fold less than hydroxyflutamide. In the presence of dihydrotestosterone (50 nM), M2 (0.2-10 microM) inhibits androgen-induced AR binding to androgen response element DNA. In the absence of dihydrotestosterone, concentrations of 10 microM M2 or hydroxyflutamide promote AR binding to androgen response element DNA and activation of transcription. Agonist activities of M2 and hydroxyflutamide occur at 10-fold lower concentrations with the mutant AR (Thr877 to Ala) endogenous to LNCaP human prostate cancer cells. The results indicate that androgen antagonists can act as agonists, depending on ligand binding affinity, concentration, and the presence of competing natural ligands.

Effect of medroxyprogesterone acetate (MPA) and serum factors on cell proliferation in primary cultures of an MPA-induced mammary adenocarcinoma

The effect of progesterone (Pg), medroxyprogesterone acetate (MPA), estradiol (E2), dihydrotestosterone (DHT) and dexamethasone (DEXA) was studied on the in vitro growth rate of a progestin-dependent (PD), estrogen-sensitive mammary tumor line originated in an MPA-treated BALB/c mouse (C4-HD), and on its estrogen-resistant variant (C4-HDR). The specificity of hormone action was further investigated using the anti-hormones RU-486 and hydroxyflutamide (FLU). Cell growth was evaluated in epithelial and fibroblast-enriched cultures using 3H-thymidine and/or autoradiography and immunocytochemistry. The results indicate that cell growth is directly stimulated by MPA and Pg at concentrations ranging from 10(-11) to 10(-7) M. RU486 prevented MPA-induced stimulation in concentrations 10 to 100 fold lower than those of MPA. When used alone, it inhibited cell proliferation only in concentrations higher than 10(-11) M. At nM concentrations, neither DEXA nor DHT stimulated 3H-thymidine uptake except DEXA at 100 nM. MPA-induced stimulation was not reverted by micromolar concentrations of FLU. As for E2 (10(-7)-10(-9) M) it prevented MPA stimulation only in cultures of estrogen-sensitive tumors. Progesterone receptors (PR) (475 +/- 115 fmoles/10(5) cells, n = 5) and estrogen receptors (ER) (ND-115 fmoles/10(5) cells, n = 5) were detected only in epithelial-enriched cultures. Serum from 7 day-MPA-treated mice induced a significant increase of 3H-thymidine uptake; an increase was also obtained with serum from untreated ovariectomized animals to which 1 nM-100 nM concentrations of MPA had been added. The stimulatory effect of the exogenous MPA was much lower than that of the serum obtained from MPA-treated animals. It is concluded that MPA stimulates cell growth of primary cultures of MPA-induced PD tumors via PR. The results provide support for a direct effect of MPA which may be mediated or potentiated by serum factors.

Sex steroids up-regulate E-cadherin expression in hormone-responsive LNCaP human prostate cancer cells

There is convincing evidence that a reduced expression of the E-cadherin cell-cell adhesion molecule associates with low tumor grade and poor prognosis in prostate cancer patients. However, little is known on how E-cadherin levels are regulated in human prostate cancer cells. We have inspected the effect of both androgens and estrogen on the expression of E-cadherin in the hormone-responsive LNCaP prostate tumor cell line, which is endowed with both androgen and estrogen receptors. Using both Dot Blot analysis and immunocytochemistry we have observed that either steroid significantly increased E-cadherin levels in these cells; this effect was not reversed by the simultaneous addition of the relevant antagonist, hydroxyflutamide or ICI-182,780.

Androgen alters the dendritic arbors of SNB motoneurons by acting upon their target muscles

In adult male rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) have been shown to retract and reextend their dendritic branches in response to systemic androgen deprivation and readministration. Furthermore, other studies have suggested that the dendritic complexity of neurons can be regulated by their targets. To assess whether androgens might act upon the target muscles to mediate changes in SNB dendrites, adult male rats were castrated and implanted with a small capsule filled with testosterone (T) next to the bulbocavernosus and levator ani muscle complex (BC/LA) on one side, while the muscles on the contralateral side were implanted with another capsule containing hydroxyflutamide (hFl), an anti-androgen. We have previously shown that after 30 d of this focused, lateralized androgen treatment the BC/LA complex is significantly larger on the T-treated side. We now report that the total dendritic lengths of SNB motoneurons innervating muscles given androgen blockade are reduced by 44% compared to SNB motoneurons innervating muscles given androgen stimulation. Dendrite lengths within three regions of the spinal cord were altered in a nonuniform manner: large changes occurred in the dorsal and contralateral dendritic fields while there was no difference in the ipsilateral dendritic field. These results suggest that BC/LA muscles, in response to androgen stimulation, produce a trophic substance which regulates the dendritic organization of SNB motoneurons in adulthood.

Atypical androgen receptor in the human melanoma cell line IIB-MEL-J

To evaluate the presence of androgen receptors in the human melanoma cell line IIB-MEL-J, a Scatchard plot analysis was performed. Cells in culture revealed a single binding component with an apparent dissociation constant (KD) at 37 degrees C of 11 nM and a binding capacity of 326 fmol/mg protein when measured with [3H]-R1881. Competition analysis revealed an atypical relaxation of specificity, since not only androgen (testosterone, dihydrotestosterone [DHT], R1881) and antiandrogen (hydroxy-flutamide [OH-FLU]) competed for [3H]-R1881 binding, but also estradiol, progesterone, and cortisol at 500-fold excess concentration. Binding of [3H]-estradiol and [3H]-R5020 in the absence of unlabeled DHT were completely suppressed in its presence. Immunohistochemistry of androgen receptor with a monoclonal antibody showed that nuclei were vigorously stained. Different doses of flutamide (FLU) and OH-FLU tested on cultured IIB-MEL-J cells in the presence of serum inhibited significantly cell proliferation in a dose-dependent manner. When cells were incubated with 10 nM DHT and 1% charcoal-adsorbed serum, a significant stimulation of growth that was observed was inhibited by 4 microM OH-FLU. DHT stimulation was completely reversed by the antiestrogen tamoxifen. In addition, male nude mice transplanted with IIB-MEL-J tumor were treated with FLU when tumors were palpable. FLU was effective in diminishing tumor growth and increasing survival rate of the animals. As a conclusion, the presence of functional androgen receptors in these cells has been demonstrated by growth inhibition in vitro and in vivo with antiandrogens, and their atypical nature is suggested by binding cross-reactivity and competition studies.

Androgenic and antiandrogenic control on epidermal growth factor, epidermal growth factor receptor, and androgen receptor expression in human prostate cancer cell line LNCaP

Both androgen and antiandrogen treatments enhance the proliferation rate of the hormone-dependent prostate cancer cell line LNCaP, expressing a mutated androgen receptor (AR). We studied the modification of the expression of epidermal growth factor (EGF), of its receptor (EGF-R), and of androgen receptor (AR) in the LNCaP cell line, under basal conditions and during androgen (R1881) and antiandrogen hydroxy-flutamide (OH-FLU) treatment. After prolonged R1881 administration, a marked increase of EGF release was observed, completely blocked by the addition of OH-FLU. The Scatchard plot analysis of EGF-R binding revealed two classes of binding sites with high and low affinity. The administration of OH-FLU alone or combined with R1881 did not modify the affinity constants, while the low-affinity component disappeared after androgen administration. Both androgen and antiandrogen administration led to a significant increase of the EGF-R high-affinity component. AR mRNA and protein levels were downregulated by R1881 treatment. Following OH-FLU administration, AR mRNA was slightly downregulated, and there was not a strict parallelism between AR mRNA levels and AR binding capacity. When combined with R1881, OH-FLU partially counteracted the androgen-induced AR downregulation. Our data show that EGF-R binding capacity is the only parameter constantly raised in cell proliferation with respect to quiescent cells, and highlights the nonunivocal action of OH-FLU on androgen-induced effects.

Androgens rapidly increase the cytosolic calcium concentration in Sertoli cells

We demonstrate that androgens rapidly and specifically increase intracellular calcium in Sertoli cells, investigate the mechanism, and suggest the unifying hypothesis that calcium might be a common intracellular molecular effector to explain the known synergism between FSH and testosterone (T) action on Sertoli cells in support of spermatogenesis. In freshly isolated Sertoli cells, T and its 5 alpha-reduced metabolite dihydrotestosterone increased intracellular calcium from 83 +/- 4 to 147 +/- 8 and 167 +/- 29 nM, respectively, whereas estradiol had minor (117 +/- 9 nM) and progesterone no (80 +/- 6 nM) effect. The effect of T was rapid (20-40 sec) and inhibited by 1) preincubation with either a pure nonsteroidal antiandrogen (hydroxyflutamide) or a 5 alpha-reductase inhibitor (finasteride) or 2) removal of extracellular calcium (47 +/- 4 nM) or pharmacological blockade of voltage-activated (62 +/- 5 nM) or voltage-independent (55 +/- 14 nM) membrane calcium channels. These findings suggest that the T-induced rise in Sertoli cell cytosolic calcium involves sequential 5 alpha-reduction, binding to a classical androgen receptor, and activation of transmembrane influx of extracellular calcium. Immobilization of T by conjugation to a large carrier molecule (BSA) to prevent steroid entry into Sertoli cells also resulted in a rapid increase in cytosolic calcium to a similar magnitude as unconjugated T, consistent with a plasma membrane site of action. This finding together with the rapid cytosolic calcium rise caused by T argues for the possible existence of a short term, nongenomic effects in hormonal regulation of Sertoli cell function in addition to the well known, slower genomic response.

Androgens induce divergent proliferative responses in human breast cancer cell lines

Although the majority of primary human breast cancers express the androgen receptor (AR), the role of androgens in breast cancer growth and progression is poorly understood. We have investigated the effects of the naturally occurring androgen, dihydrotestosterone (DHT), and a synthetic non-metabolizable androgen, mibolerone, on the proliferation of six human breast cancer cell lines. The anti-proliferative and proliferative effects of androgens were only observed in cell lines that expressed the AR. Two of the AR-positive cell lines, T47-D and ZR-75-1 were growth inhibited in the presence of either DHT or mibolerone, while the proliferation of MCF-7 and MDA-MB-453 cells was increased by both androgens. Co-incubation of cultures with 1 nM DHT and a 100-fold excess of the androgen receptor antagonist, hydroxyflutamide, resulted in reversal of both inhibitory and stimulatory effects of DHT on T47-D, MCF-7 and MDA-MB-453 cell proliferation, indicating that DHT action is mediated by the AR in these lines. Hydroxyflutamide only partially reversed the DHT-induced growth inhibition of ZR-75-1 cultures, which suggests that growth inhibition of these cells may be mediated by non-AR pathways of DHT (or DHT metabolite) action. Mibolerone action on breast cancer cell growth was similar to that of DHT, with the exception that growth stimulation of MCF-7 and MDA-MB-453 cells was only partially reversed in the presence of a 100-fold excess of hydroxyflutamide. Anandron, another androgen receptor antagonist, was able to reverse all inhibitory and stimulatory actions of the androgens. AR antisense oligonucleotides reduced the level of immunoreactive AR expression in MDA-MB-453 and ZR-75-1 cells by more than 60%, but only reversed the growth inhibitory action of mibolerone in ZR-75-1 cultures. The results suggest that androgen action in breast cancer cell lines may not be solely mediated by binding of androgen to the AR. For example, metabolites of DHT with oestrogenic activity, or androgen binding to receptors other than the AR, may explain the divergent responses to androgens observed in different breast cancer cell lines.

Growth of LNCaP human prostate cancer cells is stimulated by estradiol via its own receptor

We report that growth of LNCaP human prostate cancer cells is significantly stimulated (up to 120% above control) by physiological estradiol (E2) concentrations. This growth increase appears to be comparable to that induced by either testosterone or dihydrotestosterone, as also reported by others. This paper presents novel illustrative evidence for estrogen-binding proteins and messenger RNA transcripts in LNCaP cells. In fact, 1) the reverse transcriptase-polymerase chain reaction system documented normal messenger RNA for estrogen receptors (ER); 2) the radioligand binding assay allowed the detection of high affinity, reduced capacity binding sites in both soluble and nuclear cell fractions; and 3) the immunocytochemical analysis showed a consistently intensive staining for both ER and progesterone receptors. Compared to other human estrogen-responsive mammary cancer cells, MCF7 and ZR75-1, ER expression in LNCaP cells was not significantly lower, as shown by levels of the ER transcripts, number of sites per cell, or femtomoles per mg DNA as well as the percentage and intensity of immunocytochemical staining. A relative estimate of ER expression obtained by matching LNCaP with another human prostate cancer cell line, PC3, always displayed significantly and consistently higher levels in LNCaP cells. The detection of relatively high type I ER content in either cell compartment of LNCaP cells was paralleled by a highly intensive staining for progesterone receptors. In addition, evidence that the synthetic androgen R1881 did not compete for type I binding of E2 and that any E2-induced growth was completely reversed by the pure antiestrogen ICI-182,780, but unaffected by the antiandrogen Casodex, clearly suggests that the biological response of LNCaP cells to E2 is mediated via its own receptor.

Finasteride dose-dependently reduces the proliferation rate of the LnCap human prostatic cancer cell line in vitro

OBJECTIVES

To assess the effects of finasteride, a 5-alpha-reductase inhibitor, and of classic antiandrogens on the growth rate of the LnCap human prostate carcinoma cell line, derived from a primary and well-differentiated neoplasm.

METHODS

Cell proliferation experiments in vitro with and without the antiandrogens cyproterone acetate, hydroxyflutamide, and finasteride in the 0.0001 to 10.0 microM range.

RESULTS

The growth rate of the LnCap cell line can be dose-dependently inhibited by 5-alpha-reductase inhibition (finasteride) and by antiandrogens (cyproterone acetate and hydroxyflutamide) in vitro, in defined conditions.

CONCLUSIONS

Besides other human prostate cell lines derived from metastatic sites (PC3, DU145), also in the LnCap cell line an autonomous androgen-dependent mechanism of growth stimulation can be hypothesized, since testosterone and dihydrotestosterone are unable to stimulate the cell proliferation rate at the same molar concentrations. The clinical implications of these results in prostate cancer therapy and the possible future use of these molecules in the prevention of cancer incidence are discussed.

5-En-androstene-3 beta,17 beta-diol inhibits the growth of MCF-7 breast cancer cells when oestrogen receptors are blocked by oestradiol

Adrenal androgens show a dual and apparently opposite effect on the growth of oestrogen-responsive breast cancer: they stimulate growth on their own, but counteract the growth-stimulatory effect of oestrogens. Focusing on the inhibitory action we have studied the effects of 5-en-androstene-3 beta,17 beta-diol (ADIOL) on the growth of oestrogen-responsive MCF-7 breast cancer cells in the presence of oestrogens (oestradiol and diethylstilboestrol), antiestrogens (tamoxifen) and antiandrogens (hydroxyflutamide). The inhibition of oestrogen-stimulated growth, attained with nanomolar concentrations of ADIOL, was not modified by increasing concentrations of diethylstilboestrol up to 100 nM. This inhibition was counteracted by antiandrogens, which were unable to block the ADIOL stimulatory effect in steroid-free medium. On the other hand, in the presence of tamoxifen ADIOL showed an additive antiproliferative activity also in steroid-free medium, rather than the usual stimulatory effect. These results suggest that ADIOL stimulates breast cancer cell growth via oestrogen receptors, but inhibits oestrogen-stimulated growth via androgen receptors.

Androgen directs sexual differentiation of laryngeal innervation in developing Xenopus laevis

In adult Xenopus laevis, innervation of the vocal organ is more robust in males than in females. This sex difference originates during tadpole development; at stage 56, when the gonads first differentiate, the number of axons entering the larynx is the same in the sexes, but by stage 62, innervation is greater in males. To determine if androgen secretion establishes sex differences in axon number, we treated tadpoles with antiandrogen or androgen beginning at stage 48 or 54 and counted laryngeal nerve axons at stage 62 using electron microscopy. When male tadpoles were treated with the antiandrogen hydroxyflutamide, axon numbers were reduced to female-typical values; axon numbers in females were unaffected by antiandrogen treatment. When female tadpoles were treated with the androgen DHT (dihydrotestosterone), axon numbers were increased to male-like values. These findings suggest that endogenous androgen secretion during late tadpole stages in males is required for the sexual differentiation of laryngeal innervation observed from stage 62 on. Because androgen treatment and laryngeal innervation affect myogenesis in postmetamorphic frogs, numbers of laryngeal dilator muscle fibers were determined for hormonally manipulated tadpoles. At stage 62, vehicle-treated males had more laryngeal axons than females; laryngeal muscle fiber numbers did not, however, differ in the sexes. Both male and female tadpoles, treated from stage 54 with DHT, had more muscle fibers at stage 62 than vehicle-treated controls. Thus, while endogenous androgen secretion during late tadpole stages is subthreshold for the establishment of masculinized muscle fiber numbers, laryngeal myogenesis is androgen sensitive at this time and can be increased by suprathreshold provision of exogenous DHT. A subgroup of tadpoles, DHT treated from stage 54 to 62, was allowed to survive, untreated, until postmetamorphic stage 2 (PM2: 5 months after metamorphosis is complete). Androgen treatment between tadpole stages 54 and 62 does not prevent the ontogenetic decrease in axon numbers characteristic of laryngeal development. In addition, the elevation in stage 62 axon numbers produced by DHT-treatment at late tadpole stages was not associated with elevated numbers of laryngeal muscle fibers at PM2. Juvenile males normally maintain elevated axon numbers (relative to final adult values) through PM2 and the presence of these additional axons may result from--rather than contribute directly to--laryngeal muscle fiber addition.

In vivo and in vitro effects of androgen on fibroblast growth factor-2 concentrations in the human prostate

Prostatic growth is primarily regulated by dihydrotestosterone (DHT). Recent studies have demonstrated that a large number of growth factors are present in the human benign prostatic hyperplasia (BPH) prostate, including epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), transforming growth factor beta (TGF-beta), insulin-like growth factor (IGF), and basic fibroblast growth factor (bFGF) (FGF-2). DHT may mediate its mitogenic effects in the prostate by regulating growth factors. To test this hypothesis, we have utilized a histoculture androgen sensitivity assay (HASA) in which 3H-thymidine incorporation is measured in aliquots of BPH tissue in histoculture with either added DHT or hydroxyflutamide (HF). The resulting DHT/HF ratio is an expression of the androgen sensitivity of the tissue. In this study, we have compared the DHT/HF ratio for 3H-thymidine incorporation to the DHT/HF ratio for FGF-2 measured in the histocultured prostates. The DHT/HF ratio for the HASA studies of 3H-thymidine incorporation averaged 2.68 compared to the DHT/HF ratio for FGF-2 in the same specimens of 1.01. These values were significantly different, therefore indicating no relationship between DHT stimulation and FGF-2 levels. In addition, FGF-2 levels were measured in human BPH prostates from patients medically castrated with megesterol acetate and estradiol 17-beta prior to surgery. These values were not significantly different, and therefore do not suggest any effect of DHT on the concentration of prostatic FGF-2. Although these studies did not show any effect of DHT on the regulation of prostatic FGF-2, they do indicate that the HASA assay is feasible and appropriate to use in the study of relationships between DHT and various growth factors.

Androgen receptor function during undernutrition

Hypothalamo-pituitary inhibition of reproductive function during undernutrition is well known, however, the physiological mechanisms leading to suppression of gonadotrophin secretion are not clear. A variety of studies have indicated that testicular negative feedback on LH secretion is enhanced during food restriction. To evaluate directly the suppression by endogenous androgens on hypothalamic GnRH pulse generator activity during food restriction and examine the mechanism underlying the increased testicular steroidal feedback, we examined (1) circulating bioactive LH (bLH) levels in response to selective cerebral androgen blockade by intraventricular administration of an androgen receptor antagonist (hydroxyflutamide, SCH 16423) and (2) the binding capacity and affinity of androgen receptors in medio-basal hypothalamus, pituitary and prostate during undernutrition of intact mature male rats. Hydroxyflutamide (20 micrograms in 10 microliters vehicle), but not vehicle alone, markedly increased bLH levels in both food restricted and ad-lib fed rats. However, the faster (geometric mean 11.4 vs 27.7 min) and greater (47.2 vs 21.9 ng/ml) increase in bLH level in food restricted compared with ad-lib fed controls demonstrates an enhanced sensitivity to blockade of androgenic negative feedback during undernutrition. Food restriction increased androgen receptor binding capacity in pituitary (3.36 vs 0.77 fmol/mg protein) but not in medio-basal hypothalamus or prostate while binding affinity was unchanged by undernutrition in all 3 tissues. These studies reveal that undernutrition both enhances tonic, androgen receptor-mediated feedback suppression of GnRH secretion and increases in pituitary (but not hypothalamic) androgen receptor numbers to cause inhibition of LH secretion.

Behavioral effects of an antiandrogen in adult male rhesus macaques (Macaca mulatta)

This study was designed to determine how to suppress behavioral effects of androgens with a pure non-steroidal antiandrogen, Hydroxyflutamide (OHF). The major dependent variable was yawning behavior of castrated adult male rhesus macaques. Injections of testosterone propionate (TP) increased yawning frequency and cessation of TP injections produced a decrease in yawning frequency. A similar decrease was observed with simultaneous injections of TP and OHF. It has been found that the dose of OHF injected subcutaneously should be 80 times that of TP to block the effects of either physiological or supraphysiological doses of TP.

Antiandrogens inhibit human androgen receptor-dependent gene transcription activation in the human prostate cancer cells LNCaP

Human androgen receptor (hAR) is a ligand-dependent transcription factor that mediates androgen-induced actions on target tissues. Transfection studies in the human prostate cancer cell line LNCaP examine the ability of dihydrotestosterone (DHT), hydroxyflutamide (HO-FLU), cyproterone acetate (Cypro.A), and RU 23908-10 to stimulate or to inhibit the transcription activation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase (MMTV-CAT). DHT stimulated transcription activation of MMTV-CAT gene in LNCaP cells in a dose-dependent manner. HO-FLU, Cypro.A, and RU 23908-10, though only partially, also stimulated the transcription activation of MMTV-CAT. Despite this, 100- to 1,000-fold molar excess of all antiandrogens inhibited the agonistic activity of 10 nM DHT in this system. Receptor binding assays confirmed that HO-FLU, Cypro.A, and RU 23908-10 competed with DHT for AR binding in LNCaP cells. Western blot analysis using AR antipeptide antibodies raised in rabbits revealed the presence of two AR protein bands in LNCaP cells, following treatment with antiandrogens. Increasing doses of HO-FLU stimulated the expression of the 114-kDa AR by 2.5-fold, but did not affect the 108-kDa AR. Increasing doses of Cypro.A and RU 23908-10 decreased the levels of both the 114-kDa and the 108-kDa AR. Although the exact nature of 108-kDa and 114-kDa AR in LNCaP cells is still unknown, these data suggest that the regulatory actions of each individual antiandrogen on AR expression in LNCaP cells may be different.

Androgen receptors and hormone sensitivity of a human prostatic cancer cell line (PC-3) are modulated by natural beta-interferon

Androgen receptors are expressed at a low level in the cell line PC-3, which does not respond to either androgens or antiandrogens. If these cells are exposed to natural beta-interferon (beta-IFN) a reduction in cell growth and an increase in androgen receptors, evaluated by both biochemical and immunocytochemical techniques, occur. This increase seems not to be related to a selective block of PC-3 in any phase of the cell cycle. Pretreatment with beta-IFN determines in PC-3 cells a partial responsiveness to the androgen dihydrotestosterone as reflected by the increase in cell number. Moreover, the antiandrogen hydroxyflutamide shows agonistic properties by increasing the cell number of PC-3 cells pre-exposed to beta-IFN. When the antiandrogen is tested in combination with interferon, it produces a reduction in the beta-IFN-induced inhibition of cell growth. It is not known whether these unexpected effects are due to the increase in androgen receptors or to other mechanisms.

Androgen regulation of cell adhesion molecule gene expression in rat prostate during organ degeneration. C-CAM belongs to a class of androgen-repressed genes associated with enriched stem/amplifying cell population after prolonged castration

Androgen is required for maintaining the differentiated state of prostatic epithelium, and that cell adhesion molecules play active roles in controlling the development of epithelial cells. However, little is known about the regulation of cell adhesion molecules during prostate development. In this study, we demonstrated that the expression of an epithelial cell adhesion molecule, C-CAM, in rat ventral prostatic epithelium are repressed by androgen. A similar regulatory pattern was also observed in the seminal vesicle but not in other androgen-dependent organs (the coagulating gland and the dorsolateral prostate), or other organs (the liver and kidney). These observations suggest that regulation of C-CAM expression by androgen is tissue-specific. Unlike the other androgen-repressed genes associated with apoptosis, which have transient expression patterns, the elevated level of C-CAM in the ventral prostate persisted for more than 30 days postcastration, suggesting that C-CAM belongs to a class of androgen-repressed genes which are not associated with apoptosis. Immunohistochemical study detected C-CAM on the apical surface of secretory epithelium in control rats; castration resulted in an altered localization of C-CAM expression from columnar epithelium to cuboidal basal epithelium. Taken together, the up-regulation and altered expression pattern of C-CAM in ventral prostatic epithelium by androgen deprivation may be associated with the enriched epithelial stem/amplifying cell population in degenerated ventral prostate. These observations suggest that C-CAM may play an active role in the process of prostatic epithelial differentiation.

Suppression of sodium channel function in differentiating C2 muscle cells stably overexpressing rat androgen receptors

Differentiation of skeletal muscle and the formation of the neuromuscular junction are regulated by steroid hormones. The effects of androgens on ion channel proteins central to neuromuscular signalling have been investigated in differentiating mouse muscle C2 cells and in C2 cells that stably overexpress the rat androgen receptor (AR) cDNA. Neither the expression nor function of ACh receptors was regulated by androgenic actions in these cells. However, voltage-dependent sodium (Na) current density was decreased by androgen treatment of C2 cells and was abolished, even in the absence of androgens, in C2 cells that overexpress the AR. The decrease in functional Na current was not accompanied by concomitant decreases in Na channel mRNA, suggesting that AR influence posttranscriptional processing of Na channels in differentiating C2 cells.

Interaction of antiandrogen-androgen receptor complexes with DNA and transcription activation

Human androgen receptor (hAR) is a ligand-dependent transcription factor that mediates androgen-induced actions on target tissues. Transfection studies in receptor deficient monkey kidney cells CV-1 in culture examine the ability of dihydrotestosterone (DHT) and of the antiandrogens hydroxylflutamide (HO-FLU), cyproterone acetate (Cypro.A) and RU 23908-10 to stimulate or to inhibit the transcription activation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase (MMTV-CAT). CV-1 cells cotransfected with wild type hAR (hAR1-910) and MMTV-CAT, were treated with varying concentrations of DHT. DHT stimulated transcription activation of MMTV-CAT gene in a dose-dependent fashion. Cypro.A though only partially, also stimulated the transcription activation of MMTV-CAT. In the absence of steroids, HO-FLU induced the MMTV-CAT transcription in transfectants only 4% above the basal level. RU 23908-10 revealed the least agonistic activity at concentrations between 10 nM and 1 microM. Despite this, 100- to 1000-fold molar excess of all antiandrogens inhibited the agonistic activity of 10 nM DHT in this system. Receptor binding assays confirmed that HO-FLU, Cypro.A and RU 23908-10 competed with [3H]DHT for AR binding with hAR expressed in CV-1 cells. Western blot analysis using AR antipeptide antibodies raised in rabbits revealed the presence of two AR protein bands in extracts prepared from hAR1-910 transfected CV-1 cells. Incubation of labeled synthetic palindromic androgen responsive element (ARE) with the hAR containing CV-1 cell extracts followed by u.v. cross-linking demonstrated the specificity of AR-DNA interaction. Analysis by gel mobility shift assays showed that the interaction of AR-antiandrogen complexes with labeled ARE was specific.