Tibolone: what does tissue specific activity mean?

The epidemiologic factors associated with breast density: A review

In recent years, some studies have evaluated the epidemiologic factors associated with breast density. However, the variant and inconsistent results exist. In addition, breast density has been proved to be a significant risk factor associated with breast cancer. Our review summarized the published studies and emphasized the crucial factors including epidemiological factors associated with breast density. In addition, we also discussed the potential reasons for the discrepant results with risk factors. To decrease the incidence and mortality rates for breast cancer, in clinical practice, breast density should be included for clinical risk models in addition to epidemiological factors, and physicians should get more concentrate on those women with risk factors and provide risk-based breast cancer screening regimens.

An update on drugs for the treatment of menopausal symptoms

INTRODUCTION

Vasomotor symptoms (VMS) and the genitourinary syndrome of menopause (GSM) are recognized as the most frequent and bothersome symptoms associated with menopause. There are different treatments for both groups of symptoms, being necessary to individualize them.

AREAS COVERED

There are different therapies for VMS including hormonal treatments with estrogen, with and without progestins; the new alternative, tissue-selective estrogen complex (TSEC), tibolone, phytoestrogens and only progestins. Evidence also shows efficacy with selective serotonin reuptake inhibitors. Other nonhormonal alternatives exist as second-line treatments, all with not conclusive results. The GSM can be treated with nonhormonal treatments such as vaginal lubricants and moisturizers, other alternatives as vaginal laser needs to have more evidence. On the other hand, there is the possibility to use the hormonal treatments with systemic or local estrogen, which are the most effective treatment, the TSEC and the newest selective estrogen receptor modulator (SERM), ospemifene. Therapies with testosterone and dehydroepiandrosterone (DHEA) are still under study. The GSM can be treated with nonhormonal treatments such as vaginal lubricants and moisturizers, and other alternatives as vaginal laser need to have more evidence. On the other hand, there is the possibility to use the hormonal treatments with systemic or local estrogen, which are the most effective treatment, the TSEC and the newest SERM, ospemifene. Therapies with testosterone and DHEA are still under study.

EXPERT OPINION

The increasing numbers of therapies for menopausal symptoms open up new options, but we must individualize treatments. New possibilities arise in patients who did not have them and which can improve compliance and is also important to design strategies using combined or sequential treatments.

Risk factors, pathophysiology, and treatment of hot flashes in cancer

Hot flashes are prevalent and severe symptoms that can interfere with mood, sleep, and quality of life for women and men with cancer. The purpose of this article is to review existing literature on the risk factors, pathophysiology, and treatment of hot flashes in individuals with cancer. Electronic searches were conducted to identify relevant English-language literature published through June 15, 2012. Results indicated that risk factors for hot flashes in cancer include patient-related factors (eg, age, race/ethnicity, educational level, smoking history, cardiovascular risk including body mass index, and genetics) and disease-related factors (eg, cancer diagnosis and dose/type of treatment). In addition, although the pathophysiology of hot flashes has remained elusive, these symptoms are likely attributable to disruptions in thermoregulation and neurochemicals. Therapies that have been offered or tested fall into 4 broad categories: pharmacological, nutraceutical, surgical, and complementary/behavioral strategies. The evidence base for this broad range of therapies varies, with some treatments not yet having been fully tested or showing equivocal results. The evidence base surrounding all therapies is evaluated to enhance hot flash treatment decision-making by clinicians and patients.

Influence of estrogen deficiency and tibolone therapy on trabecular and cortical bone evaluated by computed radiography system in rats

PURPOSE: To verify the effects of tibolone administration on trabecular and cortical bone of ovariectomized female rats by computed radiography system (CRS). METHODS: The experiment was performed on two groups of rats previously ovariectomized, one received tibolone (OVX+T) while the other did not (OVX), those groups were compared to a control group (C) not ovariectomized. Tibolone administration (1mg/day) began thirty days after the ovariectomy and the treatment remained for five months. At last, the animals were euthanized and femurs and tibias collected. Computed radiographies of the bones were obtained and the digital images were used to determine the bone optical density and cortical thickness on every group. All results were statistically evaluated with significance set at P<0.05%. RESULTS: Tibolone administration was shown to be beneficial only in the densitometric analysis of the femoral head, performing higher optical density compared to OVX. No difference was found in cortical bone thickness. CONCLUSION: Ovariectomy caused bone loss in the analyzed regions and tibolone administered in high doses over a long period showed not to be fully beneficial, but preserved bone mass in the femoral head.

Effect of tibolone and its principal metabolites (3α- and 3β-hydroxy, 3α-sulfate, and 4-ene derivatives) on estrone sulfatase activity in normal and cancerous human breast tissue

BACKGROUND

Tibolone (Org-OD14) is the active substance of Livial®, a synthetic steroid with the structure 7α,17α-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-yn-3-one, possessing weak tissue-specific estrogenic, progestogenic, and androgenic properties, used to treat menopausal complaints. After oral administration, tibolone is extensively metabolized into the 3α-(Org-4904) and 3β-(Org-30126) hydroxy derivatives with estrogenic properties, its 4-ene (Org-OM38) isomer with progestogenic/androgenic activities, and the 3α-sulfate (Org-34322) derivative, a major biologically inactive circulating form. We compared the dose response of tibolone and its metabolites on estrone sulfatase activity [conversion of estrone sulfate (E1S) to estrone (E1)] in normal and cancerous human breast tissues.

MATERIALS AND METHODS

Tissue minces were incubated with physiological concentrations of [3H]-E1S (5×10-9M) alone or in the presence of tibolone and its metabolites (concentration range: 5×10-7to 5×10-5M) for 4 h. Tritiated E1, estradiol (E2), and E1S were separated and evaluated quantitatively by thin-layer chromatography.

RESULTS

The sulfatase activity was significantly higher in cancerous breast but strongly inhibited by tibolone and the different metabolites, whereas 3α- and 3β-hydroxy derivatives were the most potent inhibitors.

CONCLUSION

This very significant inhibitory effect of tibolone and its principal metabolites on the enzyme involved in E2biosynthesis in the human breast provides interesting perspectives to study the biological responses of these compounds in trials with breast cancer patients.

Management of menopause-associated vasomotor symptoms: Current treatment options, challenges and future directions

Hot flashes are one of the most common and distressing symptoms associated with menopause, occurring in more than 75% of postmenopausal women. They are especially problematic in breast cancer patients since some breast cancer therapies can induce hot flashes. For mild hot flashes, it is proposed that behavioral modifications are the first step in management. Hormonal therapies, including estrogens and progestogens, are the most well known effective agents in relieving hot flashes; however, the safety of these agents is controversial. There is an increasing amount of literature on nonhormonal agents for the treatment of hot flashes. The most promising data regard newer antidepressant agents such as venlafaxine, which reduces hot flashes by about 60%. Gabapentin is another nonhormonal agent that is effective in reducing hot flashes. While many complimentary therapies, including phytoestrogens, black cohosh, and dehydroepiandrosterone, have been explored for the treatment of hot flashes; none can be recommended at this time. Furthermore, there is a lack of strong evidence to support exercise, yoga, or relaxation for the treatment of hot flashes. Paced respirations and hypnosis appear to be promising enough to warrant further investigation. Another promising nonpharmacological therapy, currently under investigation, involves a stellate ganglion block.

The effect of different preparations of hormone therapy on tumor necrosis factor-alpha levels in women with surgical menopause

The aim of the present prospective controlled study was to examine the influence of 17beta-estradiol and tibolone on tumor necrosis factor-alpha (TNF-alpha) levels in healthy women with surgical menopause. Forty-five surgically menopausal women were included in the study. Thirty women were randomized to receive tibolone 2.5 mg or 17beta-estradiol 2 mg daily for 16 weeks. Fifteen surgically menopausal women who refused hormone therapy served as controls. Serum was collected from the subjects at baseline and at the end of the study for TNF-alpha assay. Neither tibolone nor 17beta-estradiol showed a significant influence on TNF-alpha level at the end of 16 weeks in comparison with baseline. Although tibolone induced a trend toward decreased level of TNF-alpha (3.30 +/- 0.42 vs. 2.56 +/- 1.94 microg/dl), this was non-significant. The slight increase observed in TNF-alpha level in the control group was also insignificant (3.60 +/- 1.20 vs. 4.10 +/- 0.70 microg/dl). Overall, these results demonstrate no significant effects of either tibolone or 17beta-estradiol on circulating TNF-alpha level in surgically menopausal women. However, the significant difference achieved between the tibolone and control group after treatment is promising and needs to be investigated in trials with longer treatment periods.

The effect of tibolone versus 17β-estradiol on climacteric symptoms in women with surgical menopause: A randomized, cross-over study

OBJECTIVE

To compare the effectiveness of tibolone and 17beta-estradiol on climacteric symptoms, in a randomized, single-blind, cross-over study in surgically menopausal women.

MATERIAL AND METHODS

Forty surgically menopausal women were divided randomly into two groups. Group A received treatment with tibolone for 6 months, while group B received 17beta-estradiol. After 3 weeks washout period, treatment protocols were exchanged for another 6 months. The climacteric symptoms were assessed with Greene Climacteric Scale at baseline, during washout and after the treatments. Statistical analysis was done with the Wilcoxon's Sign Rank test.

RESULTS

Both treatments significantly improved the scores of all subscales with respect to baseline. However, the improvement in psychological, somatic and sexual subscales were significantly superior in the tibolone group compared with 17beta-estradiol group. Both treatments showed comparable improvements in the relief of vasomotor symptoms.

CONCLUSION

Our findings suggest that tibolone may improve mood, libido and somatic symptoms in surgically menopausal women to a greater extent than estrogen therapy alone.

Tibolone and breast cancer

Tibolone is a relatively new drug for postmenopausal women, which is structurally related to 19-nortestosterone derivatives and exhibits weak oestrogenic, progestogenic and androgenic activities. The effect of tibolone on breast tissue is still obscure. In vitro studies have shown conflicting results regarding the effects of tibolone on breast cells. On the other hand, although epidemiological studies show an increase in the risk of breast cancer among women treated with tibolone, accumulation of data obtained from radiological studies presents promising results. However, the safety of tibolone with regard to breast tissue needs to be investigated further, especially through well-designed, large-scale, randomised-controlled trials.

Hormone replacement therapy and risk of acute myocardial infarction : a review of the literature

Many animal studies and studies on intermediate clinical endpoints have shown hormone replacement therapy (HRT) to be associated with both favourable and unfavourable cardiovascular effects. We reviewed the literature regarding HRT and the distinct endpoint of acute myocardial infarction (AMI) in peri- and postmenopausal women. Searches of the MEDLINE and EMBASE databases were conducted. Fifty papers were identified as eligible for inclusion: eight randomised controlled trials, 18 cohort studies, 23 case-control studies and one case-control and cohort study. The single large primary prevention randomised controlled trial on HRT and the risk of AMI in generally healthy women (Women's Health Initiative trial) reported a small yet significantly increased risk of AMI in postmenopausal women receiving combined HRT. This contrasts with a large number of observational studies that suggested a protective effect, although in many of these studies the results were not statistically significant. Inconclusive evidence on the effect of duration of use does not support the notion that a possible protective association is causal. Detection bias and residual confounding are alternative explanations for the associations observed in the randomised controlled trial and observational studies. No studies on groups of women with existing cardiovascular disease or with diabetes mellitus, including the only large secondary prevention trial (Heart and Estrogen/Progestin Replacement Study), reported a significant change in AMI risk between HRT users and non-users. There is insufficient evidence to suggest that HRT is associated with a change in the risk of AMI in the majority of women. However, certain subgroups of women with specific genetic polymorphisms may be more susceptible to a change in the risk of AMI with HRT use.

Postmenopausal hormone therapy and mammographic breast density

OBJECTIVE

The aim of this study was to evaluate the effects of different types of hormone replacement therapy (HRT) on mammographic density.

MATERIALS AND METHODS

In a prospective 1-year study, 103 postmenopausal women were randomized to receive tibolone 2.5 mg/die, continuous conjugated equine estrogens 0.625 mg/die plus medroxyprogesterone acetate (MPA) 5mg/die or placebo. Mammograms were performed at baseline and after 12 months of treatment. Mammographic density was quantified according to the Wolfe classification.

RESULTS

After 12 months of HRT 16 of the 35 patients (45.1%) receiving continuous combined hormonal therapy showed an increase of breast density change in the Wolfe classification. After treatment with tibolone, an up grading in breast density, according to Wolfe's classification, was found in 2 of the 43 patients (2.3%). No changes were recorded in the 25 patients of the control group. The difference between the group treated with continuous combined hormonal therapy and the control group was highly significant (p<0.001). The difference in breast density between patients in treatment with tibolone and the control group was not statistically significant (p=0.34).

DISCUSSION

Continuous combination HRT may be more commonly associated with an increase of mammography density than tibolone treatment.

Stereoselectivity in metabolic 3-reduction of tibolone in healthy Chinese female volunteers

AIM

To investigate the stereoselectivity in human metabolic 3-reduction of tibolone.

METHODS

Twenty healthy Chinese female volunteers were given a single oral dose of tibolone (2.5 mg), and serial blood samples were collected after treatment. The plasma concentrations of the two pharmacologically active 3-hydroxyl metabolites of tibolone, 3alpha-hydroxyl-7-methyl- norethynodrel (3alpha-HMN) and 3beta-hydroxyl-7-methyl- norethynodrel (3beta-HMN) in plasma were determined by using a validated liquid chromatography-mass spectrometry (LC-MS) method.

RESULTS

The apparent elimination half-life (T(1/2) of 3alpha-HMN was 1.43+/-0.52 h, and that of 3beta-HMN was 1.53+/-0.60 h. Maximum plasma concentrations (C(max)) were found to be 8.75+/-4.36 microg/L for 3alpha-HMN and 3.59+/-1.81 microg/L for 3beta-HMN. Areas under the plasma concentration versus time curve (AUC(0-t)) were 26.30+/-12.14 microg.h(-1).L(-1) for 3alpha-HMN and 9.89+/-4.93 microg.h(-1).L(-1) for 3beta-HMN.

CONCLUSION

Stereo-selective differences exist in the pharmacokinetics of tibolone metabolism in humans.

The effects of tibolone and oestrogen-based HT on breast cell proliferation and mammographic density

Tibolone is a tissue-selective compound used for the treatment of climacteric symptoms and the prevention of osteoporosis in post-menopausal women. In this review some in vitro data and clinical studies indicating that the effects of tibolone on breast tissue are different from those seen with oestrogen-based hormone therapy (HT) are briefly discussed. From a clinical perspective, an increase in mammographic density and breast cell proliferation should be regarded as an unwanted side-effect of HT. Efforts should therefore be made to define treatment regimens for post-menopausal women that have minimal effects on the breast but still maintain the many advantages of HT. Data suggest that tibolone may be such an alternative.

Postmenopausal hormone therapy before and after breast cancer: clinical experiences

Conventional oestrogen-based hormone therapy (HT) increases the incidence of breast pain and tenderness, mammographic density and the risk of breast cancer. Combined oestrogen plus progestogen therapy (EPT) increases the risk of breast cancer to a greater degree than oestrogen alone (ET). Attention must therefore be focused on identifying women at risk of breast cancer or on producing a HT that has fewer breast side effects. Randomised controlled trials have shown that while EPT induces breast tenderness or pain in up to 50% of women and increases mammographic density in up to 70% during the first year of treatment, only about as many as one-tenth women report breast tenderness or pain with tibolone and increases in mammographic density are rare, occurring with a similar incidence as seen in untreated controls. Many women with breast cancer suffer vasomotor symptoms rather than risk recurrence with conventional HT. However, in a small randomised controlled trial in women with early breast cancer undergoing adjuvant tamoxifen treatment, tibolone reduced hot flushes, night sweats and improved quality of life compared with placebo.

Sulfation of tibolone and tibolone metabolites by expressed human cytosolic sulfotransferases

Tibolone is an important therapeutic agent used in the treatment of menopausal symptoms in many countries and has beneficial effects on menopausal and postmenopausal vasomotor, bone, vaginal and mood symptoms without affecting the endometrial, breast or cardiovascular systems. The rapid metabolism of tibolone to active metabolites including 3alpha-OH-tibolone, 3beta-OH-tibolone and Delta(4)-tibolone may be important in its tissue-specific effects. Sulfation also has a major role in the metabolism and regulation of the tissue-specific activity of tibolone and its metabolites. The ability of seven major expressed human sulfotransferase (SULT) isoforms to sulfate tibolone and its three metabolites was examined. Expressed human SULT2A1 was capable of sulfating tibolone and all three metabolites with the highest affinity for 3alpha-OH-tibolone. SULT1E1 conjugated both 3-OH-tibolone metabolites and tibolone itself slightly. SULT2B1b sulfated both 3-OH metabolites but not tibolone or Delta(4)-tibolone. SULT isoforms 1A1, 1A3, 1B1 and 1C1 did not demonstrate detectable activity. Sulfation of tibolone and its metabolites by human tissue cytosols was analyzed to determine whether the pattern of tibolone sulfation corresponded to the known expression of SULT isoforms in each tissue. The tissue-specific effects of tibolone may be regulated in part by the inactivation of tibolone and its metabolites by specific human SULT isoforms.

The influence of 5-year therapy with tibolone on the lipid profile in postmenopausal women with mild hypercholesterolemia

Our objective was to investigate the effects of 5-year therapy with tibolone on the lipid profile in postmenopausal women with mild hypercholesterolemia (total cholesterol, 241 +/- 7 mg/dl; LDL cholesterol, 153 +/- 9 mg/dl). Eighty-two patients were divided into two groups. Group A (53 women) received 2.5 mg of tibolone per day. Group B (29 women) received no tibolone. Total, low- and high-density lipoprotein cholesterol and lipoprotein(a) were found to be decreased in the tibolone group, by 17.7%, 32%, 15.5% and 12%, respectively (p < 0.01) throughout the 5-year treatment, while triglycerides showed no significant change. The lipid profile in the control group remained at its initial values. Menopausal symptoms disappeared in the treatment group within the first 5 months, whereas they deteriorated in the control group during the first 2 years. Although a few unwanted side-effects on hormone-dependent tissues were observed (including vaginal spotting in 11.3% and febrile hemorrhagic cystic mastopathy in 3.8%) long-term therapy with tibolone seemed to be well tolerated, and appeared to have a beneficial effect on the levels of serum lipids.

Effect of tibolone on breast symptoms resulting from postmenopausal hormone replacement therapy

OBJECTIVE

To evaluate the incidence of breast symptoms in a population treated with various hormone replacement therapy (HRT) regimens and to detect the variations in breast symptomatology after HRT changing to tibolone administration.

METHODS

This prospective placebo-controlled clinical trial was conducted on healthy women on HRT reporting breast symptoms. A questionnaire was given to each woman to detect breast symptomatology. Breast tenderness and mastalgia were evaluated using a visual analogue scale (VAS). According to the choice of the each woman with breast symptoms, the HRT was changed to tibolone (2.5 mg/day per os) or to calcium carbonate (1 tab/day, placebo group). The duration of treatment was of 12 months. After 6 and 12 months breast symptomatology was re-evaluated.

RESULTS

Among the 600 screened women, 64 (10.7%) were suffering from breast symptomatology. After 6 and 12 months of treatment with tibolone or placebo, mean VAS score for breast tenderness and for mastalgia resulted significantly (P<0.05) decreased, without differences between groups, in comparison with basal value. Only one woman had no improvement from the breast symptoms with tibolone administration.

CONCLUSIONS

Shifting from classical HRT to tibolone is followed by a significant reduction of breast symptomatology in postmenopausal women with breast complaints similar to that obtained with treatment withdrawal.

Medical choices available for management of menopause

The indications for hormone therapy (HT) have changed markedly since the 1980s; they now include the treatment of menopausal symptoms and the prevention and treatment of osteoporosis in the short term. Long-term therapy is discouraged because of the small increase in risk of breast cancer after 5 years of therapy. Careful assessment of the midlife woman allows for individualized risk-benefit analysis with the formulation of a specific health management plan. Lifestyle advice and modification form the cornerstone of management-followed by therapeutic options if appropriate indications exist. In some industrialized countries alternative therapies are preferred despite little scientific evidence of their efficacy. The choices of hormonal products have increased, with the introduction of new formulations and routes of administration allowing for more optimal treatment of the menopause, especially in the presence of concurrent medical conditions, for example, diabetes, breast cancer or fibroids.

Tibolone is not converted by human aromatase to 7alpha-methyl-17alpha-ethynylestradiol (7alpha-MEE): analyses with sensitive bioassays for estrogens and androgens and with LC-MSMS

To exclude that aromatization plays a role in the estrogenic activity of tibolone, we studied the effect tibolone and metabolites on the aromatization of androstenedione and the aromatization of tibolone and its metabolites to 7alpha-methyl-17alpha-ethynylestradiol (7alpha-MEE) by human recombinant aromatase. Testosterone (T), 17alpha-methyltestosterone (MT), 19-nortestosterone (Nan), 7alpha-methyl-19-nortestosterone (MENT) and norethisterone (NET) were used as reference compounds. Sensitive in vitro bioassays with steroid receptors were used to monitor the generation of product and the reduction of substrate. LC-MSMS without derivatization was used for structural confirmation. A 10 times excess of tibolone and its metabolites did not inhibit the conversion of androstenedione to estrone by human recombinant aromatase as determined by estradiol receptor assay whereas T, MT, Nan, and MENT inhibited the conversion for 75, 53, 85 and 67%, respectively. Tibolone, 3alpha- and 3beta-hydroxytibolone were not converted by human aromatase whereas the estrogenic activity formed with the Delta4-isomer suggests a conversion rate of 0.2% after 120 min incubation. In contrast T, MT, Nan, and MENT were completely converted to their A-ring aromates within 15 min while NET could not be aromatized. Aromatization of T, MT, Nan and MENT was confirmed with LC-MSMS. Structure/function analysis indicated that the 17alpha-ethynyl-group prevents aromatization of (19-nor)steroids while 7alpha-methyl substitution had no effect. Our results with the sensitive estradiol receptor assays show that in contrast to reference compounds tibolone and its metabolites are not aromatized.

Receptor profiling and endocrine interactions of tibolone

The receptor profiles and in vivo activity of tibolone, and its primary metabolites, Delta(4)-isomer, and 3alpha- and 3beta-hydroxytibolone, were studied and compared to those of structurally related compounds. The Delta(4)-isomer was the strongest binder and activator of the progesterone receptor (PR); tibolone was 10 times weaker in binding and half as potent in transactivation of PR; 3alpha- and 3beta-hydroxytibolone did not bind or activate PR. In rabbits oral tibolone produced a minor progestagenic effect in the endometrium, whereas co-administration of tibolone and the anti-estrogen ICI 164,384 unmasked tibolone's progestagenic effect. 3-Hydroxytibolones were the strongest binders and activators of the estrogen receptors (ERs), with greater affinity for ERalpha than for ERbeta. Tibolone showed weaker binding and activation of both ERs and the Delta(4)-isomer has a binding and activation activity of less than 0.1% of E2 for ERalpha or ERbeta. Tamoxifen and 4-hydroxytamoxifen showed partial ERalpha agonistic effects with a maximal response of 12% and raloxifene of 3-5%. Oral administration of 1mg tibolone to ovariectomized rats induced an estrogenic effect on vaginal epithelium. The Delta(4)-isomer was a stronger binder and activator of the androgen receptor (AR) than tibolone; both 3-hydroxytibolones did not bind or activate AR. Introducing a 7alpha-methyl group decreased progestagenic and increased androgenic activity. We conclude that the progestagenic and androgenic activities of tibolone are mediated by the Delta(4)-isomer, and the estrogenic activity, by the 3-hydroxytibolones. The estrogenic activity of the 3-hydroxytibolones masked the progestagenic activity of tibolone in rabbit endometrium. Full estrogenic response was observed in rat vaginal tissue after oral administration of tibolone.

Effects of long-term hormone replacement and of tibolone on choline acetyltransferase and acetylcholinesterase activities in the brains of ovariectomized, cynomologus monkeys

We examined long-term effects of low and high doses of tibolone, conjugated equine estrogens, and conjugated equine estrogens plus medroxyprogesterone acetate on choline acetyltransferase and acetylcholinesterase activities within different regions of the brain in cynomologus monkeys. All treatments were administered for 2 years. None of the treatments produced significant increases in either choline acetyltransferase or acetylcholinesterase in any of eight brain regions analyzed. In contrast, treatment with conjugated equine estrogens plus medroxyprogesterone acetate, but not conjugated equine estrogens alone, produced significant reductions in both choline acetyltransferase and acetylcholinesterase in the medial septum/diagonal band of Broca compared with untreated controls. Treatment with tibolone also resulted in significant reductions in both choline acetyltransferase and acetylcholinesterase in the medial septum/diagonal band of Broca, and this effect was dose-related. These findings are the first to report the effects of long-term therapies used by postmenopausal women on cholinergic measures in the primate brain. The findings are consistent with recent reports in rats, and suggest that any positive effects of long-term estrogen or hormone replacement therapy on cognitive processes are probably not due to significant effects on choline acetyltransferase or acetylcholinesterase activities.

Estrogenic effects of 7alpha-methyl-17alpha-ethynylestradiol: a newly discovered tibolone metabolite

Tibolone is a synthetic steroid that is prescribed to postmenopausal women for relief of climacteric symptoms and prevention of osteoporosis. It has been reported to be metabolized in a tissue-selective manner to three steroids that collectively have weak estrogenic, progestogenic, and androgenic activities. Recently, a new tibolone metabolite, 7alpha-methyl-17alpha-ethynyl-17beta-estradiol (7alpha-Me-EE2), was identified in women. In this report, we describe the pre-clinical estrogenic activities of this metabolite and compare these effects to those obtained with 17alpha-ethynyl-17beta-estradiol (EE2) and 17beta-estradiol (E2). In an in vitro ligand-binding assay, 7alpha-Me-EE2 bound to both human estrogen receptor (ER)-alpha and -beta with IC(50)'s of 1.2 and 3.0 nM, respectively. Using MCF-7 human breast cancer cells that express high levels of ER-alpha, 7alpha-Me-EE2 transactivated an estrogen response element (ERE)-tk-luciferase reporter gene construct with an EC(50) of 0.021 nM. Likewise, 7alpha-Me-EE2 stimulated MCF-7 breast cancer cell proliferation with an EC(50) of 0.002 nM. In immature female rats, subcutaneous (s.c.) administration of 7alpha-Me-EE2 stimulated uterine wet weight gain with an ED(50) of 0.2 microg/kg. Moreover, 7alpha-Me-EE2 induced uterine complement component C3 gene expression, an estrogenic marker of epithelial cell stimulation, with an ED(50) of 0.5 microg/kg. When compared to EE2 and E2, 7alpha-Me-EE2 exhibited equivalent or greater potencies and efficacies in these assays. In summary, these results indicate that 7alpha-Me-EE2 is a very potent estrogen. This steroid appears to be the most potent estrogenic metabolite of tibolone identified to date, and additional studies are, therefore, warranted regarding the role of this metabolite in the biological actions of the drug.

Effect of tibolone (Org OD14) and its metabolites on aromatase and estrone sulfatase activity in human breast adipose stromal cells and in MCF-7 and T47D breast cancer cells

Tibolone (Org OD14) is a synthetic steroid used for post-menopausal hormone replacement therapy (HRT). Since HRT might increase breast cancer risk, it is important to determine the possible effects of tibolone on breast tissues. Tibolone and its metabolites Org 4094, Org 30126 and Org OM38 have been reported to inhibit estrone sulfatase activity in MCF-7 and T47D breast cancer cell lines, which suggest beneficial effects on hormone dependent breast cancer by reducing local production of free estrogens. Breast adipose stromal cells (ASCs) contain aromatase activity-an obligatory step in the biosynthesis of estrogens-and possibly contain sulfatase activity. We investigated the effects of tibolone, its metabolites and the pure progestin Org 2058 on PGE(2)-stimulated aromatase activity and on sulfatase activity in human ASC primary cultures and on sulfatase activity in MCF-7 and T47D cell lines. In MCF-7, tibolone and metabolites, but not Org 2058, were found to inhibit sulfatase activity. In T47D, tibolone inhibited sulfatase only at 10(-6)M, although weakly. ASC had high sulfatase activity, which was inhibited by 10(-6)M of tibolone, Org 4094 and Org 30126, but not by Org OM38 or Org 2058. Surprisingly, aromatase activity in ASC was increased by both tibolone and Org 2058 at 10(-6)M. As ligand binding assay results and immunohistochemistry indicated the absence of progesterone and estrogen receptors in ASC, these effects on aromatase and sulfatase activity in ASC likely take place by other routes. Because tibolone and its metabolites inhibit sulfatase activity, and because tibolone only increases aromatase activity at a high concentration, we conclude that effects of tibolone on the breast are probably safe.