6-Methylenandrosta-1,4-diene-3,17-dione (FCE 24304): a new irreversible aromatase inhibitor

FCE 24304 (6-methylenandrosta-1,4-diene-3,17-dione), a new irreversible aromatase inhibitor, has been identified and characterized in vitro and in vivo. The compound caused time-dependent inactivation of human placental aromatase with a t1/2 of 13.9 min and ki of 26 nM. When tested in PMSG-treated rats, ovarian aromatase activity was reduced 24 h after dosing by both the s.c. (ED50 1.8 mg/kg) and the oral (ED50 3.7 mg/kg) routes. No interference with 5 alpha-reductase activity nor any significant binding affinity for estrogen receptor was found. Slight binding affinity for the androgen receptor (RBA 0.2% of DHT) was observed.     

Inhibitory effect of combined treatment with the aromatase inhibitor exemestane and tamoxifen on DMBA-induced mammary tumors in rats

The antitumor effect of exemestane (FCE 24304), an irreversible aromatase inhibitor, given alone or in combination with tamoxifen, was investigated in rats with 7, 12-dimethylbenzanthracene (DMBA)-induced mammary tumors. The compounds were given once daily, 6 days a week for 4 weeks. Exemestane, given at the dose of 20 mg/kg/day s.c., induced 26% complete (CR) and 18% partial (PR) tumor regressions, compared to 0% CR and 6% PR observed in controls. Tamoxifen, given at 1 mg/kg/day p.o., induced 16% CR and 13% PR. The combined treatment caused 41% CR and 16% PR, thus resulting in a higher antitumor effect than either single treatment. The apperance of new tumors was reduced by each single treatment and almost totally prevented by the combined treatment. Serum prolactin (PRL) levels, assayed 4 h after the last dose, were unchanged in the group treated with the combination, whereas tamoxifen alone caused a slight increase of serum PRL. These results indicate that estrogen deprivation through aromatase inhibition and estrogen receptor antagonism causes a better inhibition of DMBA-induced mammary tumors than either treatment modality alone.     

The effect of the aromatase inhibitor, 4-(phenylthio)-4-androstene-3,17-dione, on dimethylbenz(A)anthracene-induced rat mammary tumors

4-(Phenylthio)-4-androstene-3,17-dione (4-PTAD), a known inhibitor of human placental aromatase, was examined as a growth inhibitor of DMBA-induced rat mammary tumors. Subcutaneous administration of 4-PTAD at dose levels of 25 or 50 mg/kg/day caused a significant decrease in hormone-dependent tumor growth. Resumption of tumor growth occurred when either the administration of inhibitor was stopped or when inhibitor was coadministered with estradiol indicating that suppression of tumor growth was due to inhibition of estrogen biosynthesis. Additionally, plasma levels of estradiol were found to be lower in the animals treated with 4-PTAD. The major metabolite of 4-PTAD in vitro was identified as 4-(phenylthio)-4-androstene-17 beta-ol-3-one and was found to have 60% of the aromatase inhibitory activity of 4-PTAD.     

Probing the binding pocket of the active site of aromatase with 2-phenylaliphatic androsta-1,4-diene-3,17-dione steroids

A series of 2-phenylaliphatic-substituted androsta-1,4-diene-3,17-diones (6) as well as their androstenedione derivatives (5) were synthesized as aromatase inhibitors to gain insights of structure–activity relationships of varying the alkyl moiety (C₁ to C₄) of the 2-phenylaliphatic substituents as well as introducing a methyl- or trifluoromethyl function to p-position of a phenethyl moiety to the inhibitory activity. The inhibitors examined showed a competitive type inhibition. The 2-phenpropylandrosta-1,4-diene 6c was the most powerful inhibitor (K_i: 16.1 nM) among them. Compounds 6c along with the phenethyl derivative 6b caused a time-dependent inactivation of aromatase (k_inact: 0.0293 and 0.0454 min^?1 for 6b and 6c, respectively). The inactivation was prevented by the substrate androstenedione, and no significant effect of l-cysteine on the inactivation was observed in each case. Molecular docking of the phenpropyl compound 6c to aromatase was conducted to demonstrate that the phenpropyl group orients to a hydrophobic binding pocket in the active site to result in the formation of thermodynamically stable enzyme–inhibitor complex.     

Behavioral action of estrogen in male hamsters: effect of the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD)

This study examines three independent behavioral variables known to be activated by testosterone in the male hamster; namely, the tendency to approach the female, the tendency to leave the female, and the amount of sniffing directed to her. Both intact and testosterone-maintained castrated male hamsters were given the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD) in subcutaneous, Silastic capsules. In intact males, there was an ATD dose-dependent increase in the tendency to leave the female and a decrease in the amount of olfactory investigation. The tendency of the male to approach the female was unaffected. The higher doses of ATD also abolished the ability of males to discriminate between females using vaginal odor cues. These results were confirmed in castrated males whose behavior was maintained at the intact level by testosterone implants. In addition, in both intact and castrated males, estradiol or diethylstilbestrol was able to reverse the behavioral changes induced by ATD. Our results indicate that estrogen produced by aromatization of testosterone activates behavior. We conclude that estrogen, by influencing some, but not all, components of masculine behavior, has a specific role in modulating male-female interactions.     

Effects of GSM-900 microwaves on DMBA-induced mammary gland tumors in female Sprague-Dawley rats

The aim of this investigation was to test the hypothesis that sub-chronic whole-body exposure to GSM-900 microwaves had an effect on tumor promotion and progression. Mammary tumors were induced by ingestion of a single 10-mg dose of 7,12-dimethylbenz(a)anthracene (DMBA) in female Sprague-Dawley rats (Ico:OFA-SD; IOPS Caw). In two independent experiments, DMBA-treated animals were divided into four groups: sham-exposed (16) and exposed (three groups of 16 animals). The specific absorption rates (SARs), averaged over the whole body, were 3.5, 2.2 and 1.4 W/kg in the first experiment (May-July) and 1.4, 0.7 and 0.1 W/kg in the second experiment (September-November). Exposure started 10 days after DMBA treatment and lasted 2 h/day, 5 days/week for 9 weeks. Animals were exposed to plane waves with the electric field parallel to the long axis of the animals. Body weight and the number, location and size of the tumors were recorded at regular intervals. Rats were killed humanely 3 weeks after the end of exposure. The results are negative in terms of latency, multiplicity and tumor volume. With regard to tumor incidence, in the first experiment there was an increase in the rate of incidence at 1.4 W/kg but less at 2.2 W/kg and none at 3.5 W/kg. Overall, these results, which are rather inconsistent, do not bring new evidence of a co-promoting effect of exposure to GSM-900 signals using the DMBA rat model.     

Quantitative determination of 4-hydroxy-4-androstene-3,17-dione (4-OHA), a potent aromatase inhibitor, in human plasma, using isotope dilution mass spectrometry

An original method is described for the determination in human plasma of 4-hydroxy-4-androstene-3,17-dione (4-OHA), a potent aromatase inhibitor, by isotope dilution mass-spectrometry using 7,7-[2H2]-4-OHA as internal standard. This compound was synthesized starting from 7,7-[2H2]-4-androstene-3,17-dione. The procedure includes an extraction step using an Extrelut 1 column and a derivatization with N,o-bis(trimethylsilyl)trifluoroacetamide (BSTFA). The minimum detection level of the method is 0.650 pg and the coefficients of variation for the 0.5 ng/ml (plasma) and 5 ng/ml (plasma) concentrations are 3.2% (within assay) and 6.7% (between assay) and 1.86% (within assay) and 2.3% (between assay) respectively.     

1,4-Androstadiene-3,17-dione found in the urine of a boy

A steroid, that has not been detected so far in human urine or blood, was found in the urine of a boy with signs of epileptic convulsions. Only less than 0,5 mg of the substance could be isolated by extraction methods and purified by paper and thin layer chromatography. The unknown compound was investigated by circular dichroism, ultra-violet absorption, combined gas chromatographymass spectrometry, proton nuclear magnetic resonance and infra-red spectroscopy. The structure of the unknown was determined unequivocally as 1,4-androstadiene-3,17-dione.     

Spectrophotometric estimation of 4-androstene-3,17-dione and 1,4-androstadiene-3,17-dione during C-1(2)-dehydrogenation by Mycobacterium fortuitum NRRL B-8153

A spectrophotometric method for simultaneously estimating 4-androstene-3,17-dione (AD) and 1,4-androstadiene-3,17-dione (ADD) in a binary mixture has been developed using sulphuric acid chromogens. The method has been used to estimate both AD and ADD during C-1(2)-dehydrogenation by Mycobacterium fortuitum NRRL B-8153.The authors are with the School of Life Sciences, Devi Ahilya Vishwavidyalaya. Vigyan Bhawan, Khandwa Road, Indore-452 001, India.     

Selection of 19-(ethyldithio)-androst-4-ene-3,17-dione (ORG 30958): a potent aromatase inhibitor in vivo.

19-Mercaptoandrost-4-ene-3,17-dione (ORG 30365) has been reported to be both a competitive and irreversible inhibitor of aromatase. In comparison to the known aromatase inhibitors 4-hydroxy-androst-4-ene-3,17-dione (4OH-AD) and 1-methyl-1,4-androstadiene-3,17-dione (SH 489), ORG 30365 was found to be, respectively, about 16 and 8 times more active in vitro using human placental microsomes. Although the activity profile of ORG 30365 is very attractive, this compound was not selected for further development because it has limited pharmaceutical stability, which is probably due to its free--SH group and therefore a number of more stable dithio-derivatives of ORG 30365 have been synthesized. These derivatives are considered to be converted to ORG 30365 before they become active. The in vivo aromatase inhibiting activity of these derivatives was determined in hypophysectomized rats treated with the estrogen precursor dehydroepiandrosterone sulphate (DHEAS) using inhibition of cornification of vaginal epithelium as parameter. The 19-(ethyldithio)-derivative (ORG 30958) appeared to be the most active inhibitor in this series being twice as active as ORG 30365 and about 8 times as active as inhibitors like 4OH-AD and SH 489. Besides inhibition of cornification of vaginal epithelium ORG 30958 decreased ovarian aromatase and plasma E2 levels in DHEAS-treated hypophysectomized rats. Plasma estradiol levels were also lowered by ORG 30958 in dogs which were treated with pregnant mare serum gonadotrophin in order to induce pro-estrus. ORG 30958 displayed much less than 1/400th of the androgenic activity of testosterone propionate in immature castrated rats and appeared to be devoid of estrogenic and anti-estrogenic activity in ovariectomized mature rats. A twice daily dose of 1.5 mg ORG 30958/kg postponed ovulation in mature female rats. In conclusion: ORG 30958 is a potent aromatase inhibitor in vivo. It probably becomes active after cleavage of the -S-S- bond yielding ORG 30365 a potent irreversible aromatase inhibitor. ORG 30958 does not display other hormonal activities making it an attractive candidate for the treatment of estrogen-dependent diseases.     

Microbial conversion of solasodine to 1-androstene-3,17-dione (AD), a key intermediate for androgen synthesis

The spirosolane side chain of solasodine has been cleaved by cholesterol preinduced Mycobacterium sp. NRRL B-3805 to yield 1-androstene-3,17-dione (AD), a key intermediate for the synthesis of androgenic drugs. Conversion up to 34% has been recorded in shake flask culture after 192 h incubation period using dimethyl-formamide as carrier for solasodine addition.     

Comparison of the effect of 4-hydroxy-4-androstene-3,17-dione on aromatase activity in granulosa cells from preovulatory follicles of rats, rabbits, and humans

The effect of the aromatase inhibitor 4-hydroxy-4-androstene-3,17-dione (4-OH-A) on the synthesis of estradiol (1,3,5 (10)-estratriene-3,17 beta-diol) by granulosa cells from preovulatory follicles of rats, rabbits and humans was examined. Granulosa cells from all three species were incubated for 4 h without treatment (control) or in the presence of androstenedione (4-androstene-3,17-dione, 0.5 microM), 4-OH-A (5 microM), or both compounds together. Estradiol levels were determined in the medium and cells by radioimmunoassay. In all three species, estradiol synthesis was markedly increased by androstenedione and this increase was blocked by 4-OH-A. In the rabbit, however, 4-OH-A alone caused a small but significant increase in radioimmunoassayable estradiol. The apparent increase seen with 4-OH-A alone may be due to a metabolite of 4-OH-A that cross-reacts in the estradiol radioimmunoassay. With granulosa cells from humans, in which 4-OH-A is of potential therapeutic importance, no similar effect of 4-OH-A alone was observed.     

Effects of 900 MHz GSM wireless communication signals on DMBA-induced mammary tumors in rats

The purpose of the study was to investigate whether exposure to 900 MHz GSM wireless communication signals enhances mammary tumor development and growth induced by low-dose DMBA. Five hundred female Sprague-Dawley rats were treated with a single dose of 35 mg/kg DMBA and then divided into five groups in a blinded fashion: one cage control group and four exposure groups, including three microwave exposure groups and one sham exposure with specific absorption rates (SARs) of 4.0, 1.33, 0.44 and 0 W/kg, respectively. Exposure started on the day after DMBA administration and lasted 4 h/day, 5 days/week for 26 weeks. Rats were weighed and palpated weekly for the presence of tumors and were killed humanely at the end of the 26-week exposure period. All mammary glands were examined histologically. There were no statistically significant differences in body weight between sham- and GSM microwave-exposed groups. No significant differences in overall mammary tumor incidence, latency to tumor onset, tumor multiplicity, or tumor size were observed between microwave- and sham-exposed groups. There was a tendency for reduction of mammary adenocarcinoma incidence in the lowest microwave exposure group (0.44 W/ kg) compared with the sham-exposed group (P = 0.058). Additionally, a higher incidence of adenocarcinoma was noticed in the 4.0 W/kg group from the 15th to 26th weeks, especially in the 19th week (P = 0.358 compared to sham). However, neither tendency was statistically significant; thus this study does not provide evidence that GSM microwave exposure promotes mammary tumor development in rats. In the present study there were significant differences between the cage controls and the experimental groups (sham and exposure). Body weight and mammary tumor (malignant plus benign) incidence in the cage control group were significantly higher than in the sham- and GSM microwave-exposed groups. The latency to the mammary tumor onset was significantly shorter in the cage control group than in the other groups.     

Immunological interference of the synthetic aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD) and its metabolite(s) in the radioimmunoassay for testosterone

Radioimmunoassay (RIA) for testosterone (T) in unchromatographed plasma extracts from ATD-treated rats gave spuriously high values for T. Cross-reaction and Chromatographic studies subsequently showed that ATD and, to a much greater extent, its metabolite(s) were responsible for this overestimation. Celite column chromatography proved to be an effective way of separating T from ATD and its product(s)of metabolism.     

Effect of 1,4,6-androstatriene-3,17-dione (ATD), 4-hydroxy-4-androstene-3,17-dione (4-OH-A) and 4-acetoxy-4-androstene-3,17-dione (4-Ac-A) on the 5 alpha-reduction of androgens in the rat prostate

The present study reports the effects exerted by 1,4,6-androstatriene-3,17-dione (ATD), 4-hydroxy-4-androstene-3,17-dione (4-OH-A) and 4-acetoxy-4-androstene-3,17-dione (4-Ac-A), three steroids known to inhibit the aromatization of androgens to estrogens, on the in vitro metabolism of labelled testosterone (T), dihydrotestosterone (DHT) and androstenedione (delta-4-A) in the ventral prostate of adult male rats. It has been found that ATD, in the concentration tested, does not influence the conversion of labelled T into DHT, but decreases the formation of 5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol (diols). On the contrary, 4-OH-A and 4-Ac-A simultaneously decrease the formation of DHT and the diols. When T is used as the substrate, the presence in the medium of these three steroids enhances the formation of delta-4-A and of 5 alpha-androstanedione (5 alpha-A). ATD, but not 4-OH-A and 4-Ac-A inhibits the conversion of labelled DHT into the diols. The transformation of labelled delta-4-A into 5 alpha-A is not modified by either ATD or 4-OH-A, while 4-Ac-A exerts only a small inhibition. These results suggest that the three aromatase inhibitors tested are able to profoundly modify the metabolism of T in the ventral prostate of the rat. In particular: 4-OH-A and 4-Ac-A are able to inhibit the conversion of T into DHT; ATD is able to inhibit the conversion of DHT into the diols; ATD and 4-OH-A do not inhibit the process of 5 alpha-reduction of delta-4-A into 5 alpha-A, while 4-Ac-A exerts only a minor effect. It is suggested that in the ventral prostate of the rat there are two different 5 alpha-reductase isoenzymes, one sensitive to the inhibitory effect of the steroid tested and which is responsible for the conversion of T into the 5 alpha-reduced metabolites of the 17-OH series (DHT and the diols), and a second one, insensitive to the effects of the three steroids, which affects the conversion of delta-4-A into 5 alpha-A.     

Disparate impact of butyroyloxymethyl diethylphosphate (AN-7), a histone deacetylase inhibitor, and doxorubicin in mice bearing a mammary tumor

The histone deacetylase inhibitor (HDACI) butyroyloxymethyl diethylphosphate (AN-7) synergizes the cytotoxic effect of doxorubicin (Dox) and anti-HER2 on mammary carcinoma cells while protecting normal cells against their insults. This study investigated the concomitant changes occurring in heart tissue and tumors of mice bearing a subcutaneous 4T1 mammary tumor following treatment with AN-7, Dox, or their combination. Dox or AN-7 alone led to inhibition of both tumor growth and lung metastases, whereas their combination significantly increased their anticancer efficacy and attenuated Dox- toxicity. Molecular analysis revealed that treatment with Dox, AN-7, and to a greater degree, AN-7 together with Dox increased tumor levels of γH2AX, the marker for DNA double-strand breaks and decreased the expression of Rad51, a protein needed for DNA repair. These events culminated in increased apoptosis, manifested by the appearance of cytochrome-c in the cytosol. In the myocardium, Dox-induced cardiomyopathy was associated with an increase in γH2AX expression and a reduction in Rad51 and MRE11 expression and increased apoptosis. The addition of AN-7 to the Dox treatment protected the heart from Dox insults as was manifested by a decrease in γH2AX levels, an increase in Rad51 and MRE11 expression, and a diminution of cytochrome-c release. Tumor fibrosis was high in untreated mice but diminished in Dox- and AN-7-treated mice and was almost abrogated in AN-7+Dox-treated mice. By contrast, in the myocardium, Dox alone induced a dramatic increase in fibrosis, and AN7+Dox attenuated it. The high expression levels of c-Kit, Ki-67, c-Myc, lo-FGF, and VEGF in 4T1 tumors were significantly reduced by Dox or AN-7 and further attenuated by AN-7+Dox. In the myocardium, Dox suppressed these markers, whereas AN-7+Dox restored their expression. In conclusion, the combination of AN-7 and Dox results in two beneficial effects, improved anticancer efficacy and cardioprotection.     

Confirmatory analysis of 17beta-boldenone, 17alpha-boldenone and androsta-1,4-diene-3,17-dione in bovine urine, faeces, feed and skin swab samples by liquid chromatography-electrospray ionisation tandem mass spectrometry

The origin, i.e. natural occurrence or illegal treatment, of findings of 17alpha-boldenone (alpha-Bol) and 17beta-boldenone (beta-Bol) in urine and faeces of cattle is under debate within the European Union. A liquid chromatographic positive ion electrospray tandem mass spectrometric method is presented for the confirmatory analysis of 17beta-boldenone, 17alpha-boldenone and an important metabolite/precursor androsta-1,4-diene-3,17-dione (ADD), using deuterium-labelled 17beta-boldenone (beta-Bol-d3) as internal standard. Detailed sample preparation procedures were developed for a variety of sample matrices such as bovine urine, faeces, feed and skin swab samples. The method was validated as a quantitative confirmatory method according to the latest EU guidelines and shows good precision, linearity and accuracy data, and CCalpha and CCbeta values of 0.1-0.3 and 0.4-1.0 ng/ml, respectively. Currently, the method has been successfully applied to suspect urine samples for more than a year, and occasionally to faeces, feed and swab samples as well. Results obtained from untreated and treated animals are given and their impact on the debate about the origin of residues of 17beta-boldenone is critically discussed. Finally, preliminary data about the degree of conjugation of boldenone residues are presented and a simple procedure for discrimination between residues from abuse versus natural origin is proposed.     

Studies directed towards a mechanistic evaluation of inactivation of aromatase by the suicide substrates androsta-1,4-diene-3,17-diones and its 6-ene derivatives aromatase inactivation by the 19-substituted derivatives and their enzymic aromatization

To gain insight into the mechanistic features for aromatase inactivation by the typical suicide substrates, androsta-1,4-diene-3,17-dione (ADD, 1) and its 6-ene derivative 2, we synthesized 19-substituted (methyl and halogeno) ADD and 1,4,6-triene derivatives 8 and 10 along with 4,6-diene derivatives 9 and tested for their ability to inhibit aromatase in human placental microsomes as well as their ability to serve as a substrate for the enzyme. 19-Methyl-substituted steroids were the most powerful competitive inhibitors of aromatase (K_i: 8.2–40 nM) in each series. Among the 19-substituted inhibitors examined, 19-chloro-ADD and its 6-ene derivatives (7b and 9b) inactivated aromatase in a time-dependent manner in the presence of NADPH in air while the other ones did not. The time-dependent inactivation was blocked by the substrate AD and required NADPH. Only the time-dependent inactivators 7b and 9b in series of 1,4-diene and 1,4,6-triene steroids as well as all of 4,6-diene steroids 9, except for the methyl compound 9a, served as a substrate for aromatase to yield estradiol and/or its 6-ene estradiol with lower conversion rates compared to the corresponding parent steroids 1,4-diene, 1,4,6-triene and 4,6-diene derivatives. The present findings strongly suggest that the aromatase reaction, 19-oxygenation, at least in part, would be involved in the time-dependent inactivation of aromatase by the suicide substrates 1 and 2, where the 19-substitutent would play a critical role in the aromatase reaction probably though steric and electronic reasons.