The effects of androgens and antiandrogens on hormone-responsive human breast cancer in long-term tissue culture.
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We have examined five human breast cancer cell lines in continuous tissue culture for androgen responsiveness. One of these cell lines shows a 2- to 4-fold stimulation of thymidine incorporation into DNA, apparent as early as 10 hr following androgen addition to cells incubated in serum-free medium. This stimulation is accompanied by an acceleration in cell replication. Antiandrogens [cyproterone acetate (6-chloro-17alpha-acetate-1,2alpha-methylene-4,6-pregnadiene-3,20-dione) and R2956 (17beta-hydroxy-2,2,17alpha-trimethoxyestra-4,9,11-triene-1-one)] inhibit both protein and DNA synthesis below control levels and block androgen-mediated stimulation. Prolonged incubation (greater than 72 hr) in antiandrogen is lethal. The MCF- cell line contains high-affinity receptors for androgenic steroids demonstrable by sucrose density gradients and competitive protein binding analysis. By cross-competition studies, androgen receptors are distinguishable from estrogen receptors also found in this cell line. Concentrations of steroid that saturate androgen receptor sites in vitro are about 1000 times lower than concentrations that maximally stimulate the cells. Changes in quantity and affinity of androgen binding to intact cells at 37 degrees as compared with usual binding techniques using cytosol preparation at 0 degrees do not explain this difference between dissociation of binding and effect. However, this difference can be explained by conversion of [3H]-5alpha-dihydrotestosterone to 5alpha-androstanediol and more polar metabolites at 37 degrees. An examination of incubation media, cytoplasmic extracts and crude nuclear pellets reveals probable conversion of [3H]testosterone to [3H]-5alpha-dihydrotestosterone. Our data provide compelling evidence that some human breast cancer, at least in vitro, may be androgen dependent. (+info)
Testosterone signaling through internalizable surface receptors in androgen receptor-free macrophages.
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Testosterone acts on cells through intracellular transcription-regulating androgen receptors (ARs). Here, we show that mouse IC-21 macrophages lack the classical AR yet exhibit specific nongenomic responses to testosterone. These manifest themselves as testosterone-induced rapid increase in intracellular free [Ca(2+)], which is due to release of Ca(2+) from intracellular Ca(2+) stores. This Ca(2+) mobilization is also inducible by plasma membrane-impermeable testosterone-BSA. It is not affected by the AR blockers cyproterone and flutamide, whereas it is completely inhibited by the phospholipase C inhibitor U-73122 and pertussis toxin. Binding sites for testosterone are detectable on the surface of intact IC-21 cells, which become selectively internalized independent on caveolae and clathrin-coated vesicles upon agonist stimulation. Internalization is dependent on temperature, ATP, cytoskeletal elements, phospholipase C, and G-proteins. Collectively, our data provide evidence for the existence of G-protein-coupled, agonist-sequestrable receptors for testosterone in plasma membranes, which initiate a transcription-independent signaling pathway of testosterone. (+info)
Prostate cancer treated by anti-androgens: is sexual function preserved? EORTC Genitourinary Group. European Organization for Research and Treatment of Cancer.
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This paper reports on results of the EORTC protocol 30892, an open, prospective, randomized study of 310 patients with previously untreated metastatic prostate cancer with favourable prognostic factors who were treated by either flutamide (FLU) or cyproterone acetate (CPA) monotherapy. The final analysis with regard to the main end points, time to progression and survival are still pending. Final results related to the evaluation of sexual functioning prior to and under treatment are reported here. Of 310 randomized patients 294 were eligible for evaluation within this side study. The median age was 71 years (range 48-85). Potential risk factors related to age, general health and prostate cancer were evaluated. For evaluation of sexual functions a five-item questionnaire was used which was administered by the investigator. The protocol allowed time dependent observations at 3-monthly follow-up visits. Sexual functioning was dependent on age but not on prostate cancer-related parameters. Sexual functions at entry were similar within the two treatment groups, spontaneous (nightly) erections and sexual activity were seen in 43-51% and 29-35% of cases. Under treatment, sexual functions under FLU and CPA declined slowly with median times of 12.9 and 5.8 months versus 13.7 and 8.9 months respectively for spontaneous erections and sexual activity. Eventually, with an average observation time in excess of 2 years, loss of spontaneous erections and of sexual activity occurred in 80% versus 92% and in 78% versus 88% of men under FLU versus CPA treatment respectively. None of these differences reached statistical significance. Maintenance of potency under treatment with FLU as reported in the literature is not confirmed in this study. However, loss of sexual functions under monotherapy with both antiandrogens is slow and 10-20% of men retain sexual activity after 2-6 years of treatment. This observation can be exploited in new treatment schemes and is likely to lead to improved quality of life. The advantage of FLU in time and total preservation of sexual functions is statistically not significant and must be balanced against the side effects of FLU and other pure antiandrogens, which may exceed those of CPA especially with respect to gynaecomastia. Hepatic toxicity may limit the long-term use of both drugs. (+info)
Acute impairment of relaxation by low levels of testosterone in porcine coronary arteries.
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OBJECTIVES: While there are many suggested reasons for the marked gender bias in cardiovascular events, much of the available data indicate that circulating estrogens are cardioprotective. The possibility that endogenous androgens may be detrimental to the cardiovascular system has received relatively less attention. We investigated the short-term modulatory effects of various concentrations of testosterone on vascular function in isolated porcine coronary artery rings. RESULTS: The higher concentrations (> 1 microM) of testosterone relaxed U46619-contracted coronary artery rings in an endothelium-independent manner. This direct effect was insensitive to the testosterone receptor antagonists, flutamide and cyproterone acetate. Short-term exposure (20 min) to low levels of testosterone (1-100 nM), which were ineffective on their own on vascular function, significantly diminished relaxation to bradykinin and calcium ionophore A23187 but not those produced by levcromakalim and sodium nitroprusside. The inhibitory effect observed with 1 nM testosterone was only partially reversed by flutamide and cyproterone acetate and unaltered in the presence of actinomycin D and cycloheximide. CONCLUSIONS: These results demonstrate that acute treatment with testosterone, at concentrations that have no effect on their own, reduces vasorelaxation. Furthermore, they suggest that this modulatory action may be in part independent of the classical testosterone receptor since it was not completely sensitive to the anti-androgens and was not inhibited by the transcriptional and translational inhibitors. These findings support the postulation that testosterone may have unfavorable influences on vascular function. (+info)
Differential effects of 17beta-estradiol and testosterone on the contractile responses of porcine coronary arteries.
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1. We investigated the effects of short-term exposure to physiological levels of 17beta-estradiol and testosterone on vasocontractile responses in porcine coronary artery rings. 2. Concentration-response curves to endothelin-1, 5-hydroxytryptamine, the thromboxane analogue U46619 and KCl were constructed in endothelium-intact and endothelium-disrupted artery rings. 3. Thirty minutes exposure to 17beta-estradiol (1 and 30 nM) significantly attenuated vasoconstriction to endothelin-1, 5-hydroxytryptamine and U46619. Conversely, the same concentrations of testosterone significantly potentiated responses elicited by these contractile agents. These inhibitory effects of 17beta-estradiol and enhancing actions of testosterone on contractions were endothelium-independent. KCl-mediated contractions were unaffected by the presence of either sex hormones. 4. The oestrogen receptor antagonists, tamoxifen (10 microM) and ICI 182,780 (10 microM), were unable to reverse the inhibitory influence 1 nM 17beta-estradiol had on the agonist-mediated contractile responses. Similarly, the androgen receptor antagonists, flutamide (10 microM) and cyproterone acetate (10 microM), failed to affect the potentiating activities of 1 nM testosterone. The alteration in vasoconstrictive responses observed following acute exposure to either 1 nM 17beta-estradiol and 1 nM testosterone were apparent even in the presence of the protein synthesis inhibitor cycloheximide (10 microM) and the transcription inhibitor actinomycin D (10 microM). 6. In conclusion, we report a unique type of sex hormone action on the coronary vasculature. These events occur at low nanomolar concentrations of 17beta-estradiol and testosterone, are insensitive to conventional sex hormone receptor antagonists, are not blocked by de novo protein synthesis inhibitors and have rapid time-courses that are uncharacteristic of classical genomic activities. (+info)
Cyproterone acetate diminishes sexual activity in male rabbits.
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Cyproterone acetate (CA) was injected daily in eleven rabbits for 3 weeks at a dose of 20 mg/day, and for a further week at a dose of 40 mg/day. After 3 weeks of treatment, the ejaculation frequency was reduced but other measures of sexual behaviour were not significantly changed. There was no reduction in the fructose concentration of the semen, but the volume of the ejaculates decreased. The vesicular glands from the experimental animals showed histological changes typical of those occurring after castration. It was concluded that CA reduced the activity of at least one of the accessory sex glands as well as sexual behaviour. This lends support to the current hypothesis that the endocrine regulation of rabbit sexual behaviour differs from that of the rat. (+info)
Effect of antihormones in amygdala-kindled seizures in rats.
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Tamoxifen (TXF; an antiestrogen), cyproterone acetate (CYP; an antiandrogen) and mifepristone (MIF; an antigestagen) did not affect kindling parameters (afterdischarge threshold, seizure severity, seizure duration and afterdischarge duration) in fully-kindled rats. TXF (50 mg/kg) and CYP (50 mg/kg), when combined with carbamazepine, or phenobarbital, both antiepileptics administered at their highest subprotective doses of 15 mg/kg, resulted in significant reduction of the seizure and afterdischarge durations, both in male and female rats. Additionally, the combination of carbamazepine and cyproterone markedly increased the afterdischarge threshold in fully-kindled rats of both genders. The interaction between antihormones and carbamazepine, or phenobarbital, was not reversed by the respective gonadal hormones (estradiol, progesterone, and testosterone), kainic acid, or strychnine. However, the TXF-, and CYP-induced effect on the action of carbamazepine was abolished by bicuculline, N-methyl-D-aspartic acid and aminophylline. The effect of TXF on the protective activity of phenobarbital was reversed by bicuculline and N-methyl-D-aspartic acid. Finally, the CYP-mediated effect on phenobarbital action was abolished by bicuculline and aminophylline. Neither TXF nor CYP altered free plasma levels and brain levels of carbamazepine or phenobarbital, so a pharmacokinetic interaction between antihormones and antiepileptic drugs is not probable. In view of the present data, it may be suggested that the protective activity of the antiestrogen and antiandrogen are mostly associated with the enhancement of GABA-ergic and purinergic transmission in the central nervous system. Also the augmentation of glutamatergic transmission, realized through NMDA receptors, may be involved in the mechanism of antiseizure action of TXF and CYP. (+info)
The androgenic regulation of the activities of enzymes engaged in the synthesis of deoxyribonucleic acid in rat ventral prostate gland.
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The restoration of mitosis and growth of the prostate gland of castrated animals by androgens provides a favourable experimental system for studying the hormonal regulation of enzymes engaged in DNA replication. 2. Many DNA polymerase activities were identified in the prostate gland, but only a 9S form with a particular preference for denatured DNA as template was conspicuously enhanced by androgenic stimulation. 3. Thymidine kinase also provided a sensitive indicator of the hormonal regulation of DNA replication, and on electrophoretic criteria, one discrete form of the enzyme appeared precisely with the onset of mitoris. 4. Evidence is presented to support the view that DNA ligase activity is intimately associated in the process of DNA replication in the prostate gland. 5. A spectrum of deoxyribonuclease activities is present in the prostate gland, but only one form (pI7.0) can safely be said to be implicated in the process of DNA replication. 6. Androgenic stimulation of the prostate gland leads to the appearance of a component capable of denaturing or unwinding prostate DNA. This component is seemingly distinct from RNA or DNA polymerase activities on the basis of several distince physicochemical characteristics. 7. The conspicuous feature of all the changes in enzyme activities evoked by androgens in the prostate gland is their acute tissue- and steroid-specificity. Such changes could not be mimicked in liver or spleen and the regulatory role of androgens could not be simulated by other classes of steroid hormones. Particularly on the basis of studies with the anti-androgen cyproterone acetate, it is concluded that the changes are initially mediated by the androgen-receptor system and the high-affinity binding of 5alpha-dihydrotestosterone in the prostate gland. 8. The results are discussed in the context of the mechanism of action of androgens. (+info)