Design of a Mestranol 2-N-Piperazino-Substituted Derivative Showing Potent and Selective in†vitro and in†vivo Activities in MCF-7 Breast Cancer Models.

Anticancer structure-activity relationship studies on aminosteroid (5α-androstane) derivatives have emerged with a promising lead candidate: RM-133 (2ß-[1-(quinoline-2-carbonyl)pyrrolidine-2-carbonyl]-N-piperazine-5α-androstane-3α,17ß-diol), which possesses high in vitro and in vivo activities against several cancer cells, and selectivity over normal cells. However, the relatively weak metabolic stability of RM-133 has been a drawback to its progression toward clinical trials. We investigated the replacement of the androstane backbone by a more stable mestranol moiety. The resulting compound, called RM-581 ({4-[17α-ethynyl-17ß-hydroxy-3-methoxyestra-1,3,5(10)-trien-2-yl]piperazin-1-yl}[(2S)-1-(quinolin-2-ylcarbonyl)pyrrolidin-2-yl]methanone), was synthesized efficiently in only five steps from commercially available estrone. In comparison with RM-133, RM-581 was found to be twice as metabolically stable, retains potent cytotoxic activity in breast cancer MCF-7 cell culture, and fully blocks tumor growth in a mouse xenograft model of breast cancer. Advantageously, the selectivity over normal cells has been increased with this estrane version of RM-133. In fact, RM-581 showed a better selectivity index (15.3 vs. 3.0) for breast cancer MCF-7 cells over normal breast MCF-10A cells, and was found to be nontoxic toward primary human kidney proximal tubule cells at doses reaching 50 µm.

Immunomodulation of Mytilus hemocytes by individual estrogenic chemicals and environmentally relevant mixtures of estrogens: in vitro and in vivo studies.

Endocrine disrupting compounds (EDCs) are almost ubiquitous in the aquatic environment. In the marine bivalve Mytilus the natural estrogen 17beta-estradiol (E2) and different EDCs have been recently demonstrated to affect the function of the immune cells, the hemocytes. The effects were Tamoxifen-sensitive and were mediated by rapid modulation of kinase-mediated transduction pathways. In this work we compared the in vitro effects of individual estrogenic chemicals (E2, EE: 17alpha-ethynyl estradiol; MES: mestranol; NP: nonylphenol; NP1EC: nonylphenol monoethoxylate carboxylate; BPA: bisphenol A; BP: benzophenone) on hemocyte parameters: lysosomal membrane stability (LMS), phagocytosis, lysozyme release. LMS was the most sensitive effect parameter, showing a decreasing trend at increasing concentrations of estrogens. EC50 values obtained from LMS data were utilized to calculate the estradiol equivalency factor (EEF) for each compound; these EEFs allowed for an estimation of the estrogenic potential of a synthetic mixture with a composition very similar to that previously found in waters of the Venice lagoon. Concentrated mixtures significantly affected hemocyte parameters in vitro and the effects were prevented by Tamoxifen. Significant effects of the mixture were also observed in vivo, at longer exposure times and at concentrations comparable with environmental exposure levels. The results indicate that Mytilus immune parameters can be suitably utilized to evaluate the estrogenic potential of environmental samples.

Effect of chronic administration of mestranol, tamoxifen, and toremifene on hepatic ploidy in rats.

The nonsteroidal antiestrogen tamoxifen increases the incidence of rat liver cancer through a variety of mechanisms. To compare the effects of tamoxifen (TAM) and a structurally similar analog toremifene (TOR) on rat liver, we determined the ploidy distribution for hepatocytes isolated from rats treated for 18 months with these antiestrogens or the estrogenic compound mestranol (MS). Female Sprague-Dawley rats were subjected to a 70% partial hepatectomy and administered the solvent, trioctanoin, or diethylnitrosamine (10 mg DEN/kg). After a 2-week recovery from the surgery, the rats were administered a basal diet or one containing TAM (250 or 500 ppm), TOR (250, 500, or 750 ppm), or MS (0.2 ppm) for 18 months. Pathologic changes in the liver were examined in the 15-22 rats per treatment group at the 18-month time point. An increased incidence of hepatocellular carcinomas (HCC) was detected in the 500 ppm TAM group, but not with the other treatments that did not include DEN. Both TOR and TAM promoted formation of DEN-initiated HCCs. At sacrifice, four to five rats per group were perfused and the hepatocytes isolated and cultured. Karyotypic analysis was performed on colcemid-blocked cells after 2 days in culture. The hepatic ploidy distribution was characterized in Giemsa-stained metaphase spreads. These studies indicated that chronic treatment with TAM alone resulted in a shift from tetraploid to diploid, as was also observed for rats treated once with DEN. TOR and MS alone did not cause this change in hepatic ploidy at the doses examined. A shift toward an increased content of diploid hepatocytes occurred in all rats treated once with DEN followed by TAM, TOR, or MS. These results indicate that tamoxifen administration results in a shift toward growth of diploid hepatocytes, thus contributing to its carcinogenic action in the rat liver.

In vitro and in vivo genotoxicity evaluation of hormonal drugs v. mestranol.

Genotoxicity of a widely used estrogen, Mestranol, was undertaken using in vitro, in vivo and host-mediated assay with bacteria as indicator organism. Analyses of chromosome aberrations and sister chromatid exchanges (SCEs) in human lymphocytes and chromosome aberrations, micronuclei and sister chromatid exchanges (SCEs) in bone-marrow cells of mice showed the drug to be capable of attacking the genetic material. However, both Ames Salmonella/S9 assay with and without S9 mix and host-mediated assay using same tester strains of Salmonella, did not show any significant increase/decrease in the His+ revertants.

Role of oral contraceptive in atherosclerosis.

The possibility that risk of a atherosclerosis complication increases with oral contraceptive use was examined by studying the effect of oral pill containing 0.067 mg menstranol and 0.667 mg ehtynodiol diacetate/kg body weight on the metabolism of lipids in female rats fed a hypercholesterolemic diet for three months. Experimental group clearly exhibited higher levels of triglycerides and cholesterol in plasma and tissues, increase in aorta observed to be two folds. Increased hepatic cholesterogenesis was noted with treatment of oral contraceptive as indicated by higher activity of HMG-CoA reductase. Activity of lipoprotein lipase of extrahepatic tissue was depressed in experimental group. Activity of plasma LCAT, an enzyme involved in the transport of cholesterol from tissues, was also lower with treatment of oral contraceptive. However, activity of malic enzyme and glucose-6-phosphate dehydrogenase enhanced considerably with administration of oral pill. The increase in plasma and aortic cholesterol levels, increase in LDL+VLDL cholesterol and considerable decrease in HDL cholesterol in animals treated with oral contraceptives and fed with atherogenic diet, indicates that prolonged administration of oral pill may predispose towards atherosclerosis.

Arterial sodium concentration in rats with hypertension induced by mestranol.

Rats were made hypertensive by the oral ingestion of mestranol for 6 months. Carotid arteries from these hypertensive rats and from control rats were incubated in an extract of plasma from these rats, which contained 24Na and 14C-sucrose (an extracellular fluid marker). After sufficient time for equilibration, the vessels were removed and counted for 24Na; an aliquot of the incubation fluid was also counted for 24Na. At least 7 days later, after the 24Na had decayed away, the samples were counted for 14C-sucrose. By knowing the specific activity of the 24Na and the ratio of 24Na/14C in the bathing fluid, the amount of intracellular Na could be calculated for each carotid artery. The total protein content of each vessel was determined, and the results were expressed as nEq of Na per mg of vessel. The Na content of carotids from mestranol treated rats averaged 135 +/- 11 (SEM) while the carotids from the control rats averaged 125 +/- 8 nEq/mg protein. Because these values were not significantly different, this study provided no evidence that increases in arterial Na content contributed to the hypertension associated with the ingestion of mestranol in this rat model.

Estrogen protection against atherosclerosis and synthetic estrogen production of cirrhosis in the rabbit.

Two artificial estrogens, ethinyl estradiol and mestranol, were found to cause cirrhosis in the rabbit liver during a study of atherosclerosis. These drugs showed protective effects against atherosclerosis in cholesterol-fed rabbits when administered orally (1 ppm in diet). These drugs and two naturally occurring estrogens, estrone and estradiol, were similarly effective when administered intramuscularly (1.5 mg per rabbit per week) to rabbits fed a diet lower in cholesterol. Reduction by estrogens of plasma cholesterol did not fully account for the reduction of extent of aortic atherosclerosis. Also, no differences in aortic or platelet eicosanoid production from exogenous arachidonic acid were found to explain the effect on atherogenesis. The 2 artificially modified estrogens, ethinyl estradiol and mestranol, caused portal fibrosis with biliary proliferation (even in rabbits not fed cholesterol). Estrone, estradiol, and testosterone were not injurious in this regard at the dosages used. Only the unmodified estrogens reduced atherosclerosis without damaging the rabbit liver.

Total exchangeable sodium in rats with mestranol-induced hypertension.

Rats were fed a diet containing mestranol, an orally active estrogen, while control rats were fed the same diet without mestranol. After 6 months of these diets, the rats were weighed, blood pressures were measured, and total exchangeable sodium was determined by injecting 24Na and determining the amount of 24Na in the plasma, the plasma Na concentration, and the residual 24Na in each rat. The 16 mestranol-treated rats were hypertensive (mean arterial pressure 135 +/- 3 mm Hg) when compared with the 17 controls (116 +/- 3 mm Hg). Total exchangeable sodium in the mestranol-treated rats averaged 39.94 +/- 0.49 (SEM) mEq/kg body wt, which was very similar to the value of 39.87 +/- 0.63 mEq/kg found in the control rats. Thus, no changes in total exchangeable sodium in mestranol-hypertensive rats were found in these studies.

Chlamydial salpingitis in female guinea pigs receiving oral contraceptives.

Female guinea pigs were given daily doses of a combination of oral contraceptive (OC) agents, consisting of mestranol and norethynodrel suspended in sesame oil or distilled H2O, and were infected in the genital tract with the chlamydial agent of guinea pig inclusion conjunctivitis (GPIC). Counts of chlamydial inclusions in cells of vaginal smears collected during infection, showed prolongation and enhancement of infection in OC-treated animals as compared with controls. Appearance of IgG and IgA antibodies to GPIC in genital secretions, as determined by enzyme-linked immunosorbent assay (ELISA), was also delayed in OC-treated animals as compared with controls. OC-treated infected animals were killed on days 15 and 43, and gross pathological evidence for ascending infection culminating in salpingitis was found in all of five and four of five animals, respectively. On the other hand, among untreated infected controls on each sacrifice day, only one of five animals had any evidence for ascending infection. Chlamydiae were detected by light and electron microscopy in fallopian tube tissue collected on day 15 following OC-treatment but not in tissue from control animals.

The morphologic effects of synthetic reproductive steroids on the mammary gland of rhesus monkeys. Mestranol, ethynerone, mestranol-ethynerone, chloroethynyl norgestrel-mestranol, and anagestone acetate-mestranol combinations.

A total of 213 treated and 16 control monkeys comprising 12 experimental groups was evaluated for determination of the long-term (10 years) effects of various dosages of a variety of synthetic oral contraceptive steroids on the mammary glands of rhesus monkeys. The steroid hormones included mestranol, ethynerone, a combination of mestranol and ethynerone, chlorethynyl norgestrel plus mestranol, and anagestone acetate plus mestranol. Various degrees of physiologic lobular hyperplasia and lactational changes were observed in association with all of these steroid hormones; these changes appeared dose-dependent. Mestranol caused a proliferative atypia ranging from a minimal to a moderate degree in 8 of 34 (23%) animals, but it was not dose-related. Eleven of 15 monkeys (73%) administered ethynerone developed proliferative atypia, ranging in degree from minimal to severe, including one invasive carcinoma and 2 lesions resembling intraductal carcinoma in the human. The mestranol and ethynerone combination produced a proliferative atypia in 22 of 52 animals (42%), including five identical to intraductal carcinoma in the human and one identical to lobular neoplasia. Of the 40 monkeys administered anagestone acetate and mestranol, 20 (50%) developed proliferative atypias; the atypias ranged from mild to severe and included five resembling intraductal carcinoma in human breast. The chloroethynyl norgestrel and mestranol combination induced proliferative atypia in 25 of 52 monkeys (49%); six of these atypias were severe and indistinguishable from intraductal carcinoma of the human breast; and one, if in the human breast, would reflect a solid variant of an invasive carcinoma. Only 2 of the 16 control monkeys (12%) developed proliferative atypias, and these were of minimal to mild degree. The occurrence of severe degrees of atypia identical to intraductal carcinoma in the human breast and invasive carcinoma associated with hormone administration suggests a carcinogenic effect.

Effects of captopril and bradykinin on arterial pressure in rats with mestranol-induced hypertension.

Hypertension was produced in 20 female rats by the oral administration of mestranol for 6 months; 20 control rats were not given mestranol during this time. The i.v. infusion of the angiotensin converting enzyme inhibitor, captopril, into 10 conscious mestranol-treated rats reduced mean arterial pressure from 139 +/- 2 (SEM) to 130 +/- 2 mm Hg (P less than 0.01); mean arterial pressure in 10 conscious control rats averaged 123 +/- 3 mm Hg, and was not significantly changed during captopril infusion. Injections of bradykinin at 0.1, 0.3, and 1.0 microgram/100 gm body weight decreased mean arterial pressure significantly more in 10 mestranol-treated rats than in 10 control rats. These results suggest that the ability of captopril to lower arterial pressure in rats with mestranol-induced hypertension may be due, at least in part, to the action of captopril to enhance bradykinin.

Mestranol: the assignment of its 1H and 13C NMR spectra by means of two-dimensional NMR spectroscopy, and its photochemical decomposition.

The 1H- and 13C-nmr spectra of mestranol were assigned with the help of a 2 D-J-resolved, a 2D spin echo J-correlated (SECSY) and a 2D 1H-13C hetero-shift correlation experiment. The analysis of the spectra facilitated the identification of some of the photodecomposition products of mestranol. It was shown that, upon irradiation with UV-B light in water-ethanol (1:1, v/v), products are formed by oxidation of rings B and C of the steroid.

Enhancement of hepatocarcinogenesis in female rats by ethinyl estradiol and mestranol but not estradiol.

The effect of dietary exposure to synthetic estrogens on hepatocarcinogenesis was evaluated. Diethylnitrosamine-initiated and 0.85% NaCl solution-treated noninitiated female Sprague-Dawley rats were transferred to semisynthetic diets containing mestranol (0, 0.1, or 0.5 ppm), ethinyl estradiol (0.5 ppm), estradiol (0.6 ppm), or mestranol plus beta-methasone (0.5 and 0.2 ppm, respectively). gamma-Glutamyl transferase (GGT)-positive transections and hematoxylin and eosin-detectable nodules and carcinomas were scored at 9 and 12 months. Quantitative stereological calculations were performed to determine GGT lesion number and size. At 9 months, in diethylnitrosamine-initiated rats, ethinyl estradiol and mestranol caused 3.5- and 4.4-fold increases, respectively, in the number of GGT lesions per liver and an increased incidence of hepatocellular carcinomas while estradiol had no enhancing effect. Addition of beta-methasone to the mestranol-containing diet caused a significant decrease in GGT lesion number but not carcinoma incidence compared to mestranol alone. At 12 months, in diethylnitrosamine-initiated rats, mestranol caused a dose-dependent increase in GGT lesion number. The hepatocellular carcinoma incidence was significantly increased at the high mestranol dose. Small increases in the numbers of larger GGT lesions were also observed in noninitiated animals treated with mestranol and ethinyl estradiol and are most probably due to promotion of spontaneously initiated hepatocytes. These results indicated that the synthetic estrogens cause dramatic increases in the number of presumptive preneoplastic GGT lesions. Carcinoma incidence is also enhanced. Thus, these results confirm and extend our previous studies which together with the results of others have shown that synthetic estrogens can act as promoters of hepatocarcinogenesis.

Further investigations on the cytological effects of some contraceptives.

Anovlar induces a mitodepressive effect, producing abnormal prophases and a considerable number of micronuclei, i.e. Anovlar can produce major cytological abnormalities. On the other hand, Lyndiol induces minor abnormalities leaving the process of mitosis to proceed almost normally. Microgynon 30 did not show any effect on any of the mitotic stages. Our conclusion may offer an explanation for the contradictory results found in the literature upon the cytological effect of oral contraceptives, although the major chemical constitution of all contraceptives used is the same, still there are minor differences in their chemical structure. These minor differences in chemical structure may be the deciding cause whether or not a contraceptive is harmful.

PIP: Anovlar induces a mitodepressive effect, producing abnormal prophases and a considerable number of micronuclei, i.e., Anovlar can produce major cytological abnormalities. Conversely, Lyndiol induces minor abnormalities leaving the process of mitosis to proceed almost normally. Microgynon 30 did not show any effect on any of the mitotic stages. The conclusion may offer an explanation for the contradictory results found in the literature of the cytological effect of oral contraceptives, although the major chemical constitution of all contraceptives used is the same, still there are minor differences in their chemical structure. These minor differences may be the deciding factor as to whether or not a contraceptive is harmful.

Alteration of convulsive threshold and conditioned avoidance response in mice fed diets containing contraceptive steroids.

Female CD1 mice given the contraceptive steroids mestranol and norethynodrel (1:10) in the diet (0.0033%) for 4 months had a growth reduction of 20% when compared with mice fed a normal diet, and had lower convulsive thresholds when tested with the vitamin B6 antagonists 2,4-dimethyl-5-methyl-hydroxypyrimidine and thiosemicarbazide. In conditioned avoidance response (CAR) tests, mice fed the steroid-containing diets showed a decreased acquisition performance during all six sessions; however, mice fed the same diet supplemented with vitamin B6 (0.04%) performed as well during the last three sessions of the CAR tests as mice fed the normal diet.

Enhancement of mutagenic activity in Salmonella by contraceptive steroids.

Two oral contraceptive steroids, mestranol and norethynodrel, were evaluated for mutagenicity in the Salmonella histidine reversion assay. The pure forms of the hormones were not mutagenic when tested with either missense (TA1535, TA100) or frameshift (TA98, TA1538, TA1537) strains. In vitro activation of the hormones with liver homogenates from rats induced either with phenobarbital or Aroclor did not influence these results. However, mestranol was capable of enhancing the mutation yield obtained by an ineffective subthreshold dose of 2-acetylaminofluorene. Dimethyl sulfoxide extracts of two contraceptive pills, Ovulen-21 (containing mestranol) or Enovid-E (containing mestranol or norethynodrel), also were nonmutagenic. But again, both these extracts were capable of enhancing the mutation yield induced with an ineffective dosage of 2-acetylaminofluorene and N-nitrosopiperidine. These studies point to the possible promotional effect and subsequent potential hazard to the female consumers who use these hormones as a means of pregnancy control.

Lack of hepatogenotoxicity of oral contraceptive steroids.

The objective of the present study was to determine whether mestranol could initiate hepatocarcinogenesis and whether various gonadal steroids have detectable hepatogenotoxic potential. To test for initiation potential, female, Sprague-Dawley rats were partially hepatectomized and intubated with mestranol (100 or 500 mg/kg) 24 h later. Twenty-four hours after treatment all rats were transferred to diet containing 0.05% phenobarbital to promote hepatocytes initiated by mestranol treatment. Four months later an analysis of putative preneoplastic gamma glutamyl transpeptidase positive foci indicated that mestranol did not cause a significant increase in the number of such foci. Hepatogenotoxicity was assessed in two ways, first using alkaline elution to detect liver DNA damage after in vivo treatment with mestranol, and second by detection of DNA repair synthesis in primary cultures of hepatocytes treated with various oral contraceptive steroids. The results of both studies were negative. In conclusion, the oral contraceptive steroids do not exhibit strong initiating or genotoxic potential.