Clinical opinion: the biologic and pharmacologic principles for age-adjusted long-term estrogen therapy

The pathophysiologies of osteoporosis, cardiovascular disease, and breast cancer are briefly reviewed within the context of the relevance and safety of long-term estrogen therapy (ET). Extrapolation of data from the known underlying biology of these diseases and the results of randomized controlled clinical trials suggest that selective ET is appropriate and safe for the majority of postmenopausal women. A key element to this clinical practice is individualization of ET, which includes timing of the initiation of therapy, selection of the route and possibly the type of estrogen prescribed, adjustment of the dose of estrogen over time to compensate for local tissue estrogen synthesis, and annual monitoring and reassessment of the indication for continuing therapy. Established disease requires disease-specific therapy but does not exclude ET cotherapy provided there is an indication for its use. Estrogen-dependent cancer is an absolute contraindication to systemic ET.     

Menopausal hormone therapy and women’s health: An umbrella review

BackgroundThere remains uncertainty about the impact of menopausal hormone therapy (MHT) on women’s health. A systematic, comprehensive assessment of the effects on multiple outcomes is lacking. We conducted an umbrella review to comprehensively summarize evidence on the benefits and harms of MHT across diverse health outcomes.Methods and findingsWe searched MEDLINE, EMBASE, and 10 other databases from inception to November 26, 2017, updated on December 17, 2020, to identify systematic reviews or meta-analyses of randomized controlled trials (RCTs) and observational studies investigating effects of MHT, including estrogen-alone therapy (ET) and estrogen plus progestin therapy (EPT), in perimenopausal or postmenopausal women in all countries and settings. All health outcomes in previous systematic reviews were included, including menopausal symptoms, surrogate endpoints, biomarkers, various morbidity outcomes, and mortality. Two investigators independently extracted data and assessed methodological quality of systematic reviews using the updated 16-item AMSTAR 2 instrument. Random-effects robust variance estimation was used to combine effect estimates, and 95% prediction intervals (PIs) were calculated whenever possible. We used the term MHT to encompass ET and EPT, and results are presented for MHT for each outcome, unless otherwise indicated. Sixty systematic reviews were included, involving 102 meta-analyses of RCTs and 38 of observational studies, with 102 unique outcomes. The overall quality of included systematic reviews was moderate to poor. In meta-analyses of RCTs, MHT was beneficial for vasomotor symptoms (frequency: 9 trials, 1,104 women, risk ratio [RR] 0.43, 95% CI 0.33 to 0.57, p < 0.001; severity: 7 trials, 503 women, RR 0.29, 95% CI 0.17 to 0.50, p = 0.002) and all fracture (30 trials, 43,188 women, RR 0.72, 95% CI 0.62 to 0.84, p = 0.002, 95% PI 0.58 to 0.87), as well as vaginal atrophy (intravaginal ET), sexual function, vertebral and nonvertebral fracture, diabetes mellitus, cardiovascular mortality (ET), and colorectal cancer (EPT), but harmful for stroke (17 trials, 37,272 women, RR 1.17, 95% CI 1.05 to 1.29, p = 0.027) and venous thromboembolism (23 trials, 42,292 women, RR 1.60, 95% CI 0.99 to 2.58, p = 0.052, 95% PI 1.03 to 2.99), as well as cardiovascular disease incidence and recurrence, cerebrovascular disease, nonfatal stroke, deep vein thrombosis, gallbladder disease requiring surgery, and lung cancer mortality (EPT). In meta-analyses of observational studies, MHT was associated with decreased risks of cataract, glioma, and esophageal, gastric, and colorectal cancer, but increased risks of pulmonary embolism, cholelithiasis, asthma, meningioma, and thyroid, breast, and ovarian cancer. ET and EPT had opposite effects for endometrial cancer, endometrial hyperplasia, and Alzheimer disease. The major limitations include the inability to address the varying effects of MHT by type, dose, formulation, duration of use, route of administration, and age of initiation and to take into account the quality of individual studies included in the systematic reviews. The study protocol is publicly available on PROSPERO (CRD42017083412).ConclusionsMHT has a complex balance of benefits and harms on multiple health outcomes. Some effects differ qualitatively between ET and EPT. The quality of available evidence is only moderate to poor.

In an umbrella review, Guo-Qiang Zhang and colleagues comprehensively summarize evidence on the benefits and harms of menopausal hormone therapy across diverse health outcomes.     

A Nation-Wide Multicenter 10-Year (1999-2008) Retrospective Clinical Study of Endocrine Therapy for Chinese Females with Breast Cancer

Endocrine therapy (ET) is one of the main systemic treatments for patients with breast cancer. To our knowledge, few studies have addressed the performance of ET or relevant influencing factors in cancer treatment in China. By retrospectively analyzing the clinicopathological data on breast cancer collected from representative hospitals of 7 traditional areas in China in one random month from each year between year 1999 and 2008, we found that: 1) The rate of the use of hormone receptor (HR) testing was 83.8% (3529/4211), with the estrogen receptor-positive (ER+) rate and/or the progesterone receptor-positive (PR+) rate being 67.9% (2395/3529), and the ER-PR rate being 32.1% (1134/3529). 2) Of the 1599 patients who had received ET, 999 patients (58.3%) were premenopausal while 600 (41.7%) were postmenopausal; 1598 patients received adjuvant hormonal therapy (AHT), whereas only 1 patient received palliative therapy. The medications mainly administered to patients were anti-estrogen agents (80.3% [1283/1598]), followed by AIs (15.5% [248/1598]). Of the 1598 patients receiving AHT, 1416 patients (88.6%) were positive for ER and/or PR, while 75 (4.7%) were negative for both and 108 patients (6.7%) had unknown HR status. The ratio of the use of endocrine therapy for breast cancer patients with ER+ and/or PR+ status was 60.0% (1416/2395). 3) Results from the logistic regression analysis revealed that geography, occupations, and history of chemotherapy and surgery were dependent factors affecting the application of ET in breast cancer treatment in China (P<0.001). In conclusion, the use of ET on Chinese women with breast cancer is increasingly and gradually accounted into the standardized process. Economic status, occupations, and history of chemotherapy and surgery were key factors affecting the application of ET. People residing in developed areas, engaging in mental labour, having history of chemotherapy and surgery are susceptible to accept ET.     

Menopausal Hormone Therapy and Lung Cancer-Specific Mortality Following Diagnosis: The California Teachers Study

Previous results from research on menopausal hormone therapy (MHT) and lung cancer survival have been mixed and most have not studied women who used estrogen therapy (ET) exclusively. We examined the associations between MHT use reported at baseline and lung cancer-specific mortality in the prospective California Teachers Study cohort. Among 727 postmenopausal women diagnosed with lung cancer from 1995 through 2007, 441 women died before January 1, 2008. Hazard Ratios (HR) and 95% Confidence Intervals (CI) for lung-cancer-specific mortality were obtained by fitting multivariable Cox proportional hazards regression models using age in days as the timescale. Among women who used ET exclusively, decreases in lung cancer mortality were observed (HR, 0.69; 95% CI, 0.52–0.93). No association was observed for estrogen plus progestin therapy use. Among former users, shorter duration (<5 years) of exclusive ET use was associated with a decreased risk of lung cancer mortality (HR, 0.56; 95% CI, 0.35–0.89), whereas among recent users, longer duration (>15 years) was associated with a decreased risk (HR, 0.60; 95% CI, 0.38–0.95). Smoking status modified the associations with deceases in lung cancer mortality observed only among current smokers. Exclusive ET use was associated with decreased lung cancer mortality.     

Thalamo-Basal Ganglia Connectivity in Postmenopausal Women Receiving Estrogen Therapy

Cumulative data on the effects of estrogen therapy (ET) on brain function in postmenopausal women suggests that ET influences cerebral metabolism and may protect against age-related declines in various domains of cognitive function. The beneficial cognitive effects of ET may relate to its modulation of the thalamic-striatum cholinergic and dopaminergic systems, as the activity of both neurotransmitter systems in the thalamus appears to be positively influenced by estrogen. In the current study, we attempted to evaluated regional cerebral brain metabolism utilizing [18F]-fluorodeoxyglucose positron emission tomography in 11 healthy recently-postmenopausal women on ET (ET+) in comparison to 11 recently-postmenopausal and ET-naïve women (ET?) in order to assess the effects of ET on cholinergic and dopaminergic system regulation. Results showed thalamo-basal ganglia connectivity among ET+ women but not among ET? women. The presence of connectivity in the thalamo-striatal pathway in recently postmenopausal women suggests estrogen effects in preserving integrity of the cholinergic and dopaminergic systems. The results also suggest that ET initiated at or near the menopausal transition may modulate brain aging by mediating complex sensory-motor functions.     

Intra-articular electrotransfer of plasmid encoding soluble TNF receptor variants in normal and arthritic mice

BACKGROUND: Anti-inflammatory gene therapy is promising in inflammatory diseases such as rheumatoid arthritis (RA). We have previously demonstrated that intra-muscular (i.m.) electrotransfer (ET) of plasmids encoding three different human tumor necrosis factor-alpha-soluble receptor I variants (hTNFR-Is) exert protective effects in an experimental RA model. However, such a systemic approach could be responsible for side effects. The present study aimed at performing an intra-articular (i.a.) gene therapy by electrotransfer using the hTNFR-Is plasmids. METHODS AND RESULTS: We evaluated targeting of mice joints by CCD optical imaging after i.a. ET of a luciferase-encoding plasmid and we showed that ET led to strongly increased transgene expression in a plasmid dose-dependent manner. Moreover, articular and seric hTNFR-Is was detectable for 2 weeks. As expected, systemic hTNFR-Is rates were lower after i.a. ET than after i.m. ET. A longer protein secretion could be achieved with several i.a. ETs. Also, we observed that hTNFR-Is expression within arthritic joints was slightly higher than in normal joints. CONCLUSIONS: In collagen-induced arthritis (CIA), a mouse model for RA, we demonstrated that hTNFR-Is/mIgG1-encoding plasmid i.a. ET decreased joint destruction in the ankles. In conclusion, our results suggest that local TNFR-Is gene therapy may play a role in decreasing joint destruction in CIA.     

A dominant negative ERβ splice variant determines the effectiveness of early or late estrogen therapy after ovariectomy in rats

The molecular mechanisms for the discrepancy in outcome of initiating estrogen therapy (ET) around peri-menopause or several years after menopause in women are unknown. We hypothesize that the level of expression of a dominant negative estrogen receptor (ER) β variant, ERβ2, may be a key factor determining the effectiveness of ET in post-menopausal women. We tested this hypothesis in ovariectomized nine month-old (an age when irregular estrous cycles occur) female Sprague Dawley rats. Estradiol treatment was initiated either 6 days (Early ET, analogous to 4 months post-menopause in humans), or 180 days (Late ET, analogous to 11 years post-menopause in humans) after ovariectomy. Although ERβ2 expression increased in all OVX rats, neurogenic and neuroprotective responses to estradiol differed in Early and Late ET. Early ET reduced ERβ2 expression in both hippocampus and white blood cells, increased the hippocampal cell proliferation as assessed by Ki-67 expression, and improved mobility in the forced swim test. Late ET resulted in either no or modest effects on these parameters. There was a close correlation between the degree of ERβ2 expression and the preservation of neural effects by ET after OVX in rats, supporting the hypothesis that persistent elevated levels of ERβ2 are a molecular basis for the diminished effectiveness of ET in late post-menopausal women. The correlation between the expression of ERβ2 in circulating white blood cells and brain cells suggests that ERβ2 expression in peripheral blood cells may be an easily accessible marker to predict the effective window for ET in the brain.     

Impact of long-term hormone replacement therapy on in vivo and in vitro markers of lipid oxidation

Postmenopausal hormone replacement therapy (HRT) with estrogen has been suggested to inhibit oxidation of low-density lipoprotein (LDL) in vitro, but progestins may oppose this effect. We studied whether estrogen HRT and combined HRT with estrogen and progestin differ in their ability to resist in vivo and in vitro oxidation of lipids. Study group included 15 women on oestradiol valerate (mean age 56 years, treatment duration 10.5 years) and 15 women on combined HRT with oestradiol valerate and levonorgestrel (mean age 58 years, treatment duration 11.3 years). In addition to lipid and apolipoprotein concentrations, the lagtime of LDL to oxidation, the rate of the propagation phase and the maximum concentration of conjugated dienes were recorded as indices of LDL susceptibility to copper-induced oxidation in vitro. As an in vivo marker of oxidative stress we measured 24-h excretion of urinary 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha). All measurements were done after long-term HRT (baseline), after 4 weeks pause and again 3 weeks after reintroduction of HRT. High-density lipoprotein (HDL) cholesterol and apolipoprotein AI concentrations were significantly higher and LDL to HDL ratio significantly lower after long-term oestradiol valerate therapy than after combined therapy. Simultaneously, the triglyceride and lipoprotein (a) levels were higher in the estrogen group. Susceptibility of LDL to oxidation and the level of 8-iso-PGF2alpha were similar in both groups at all measurement points, and treatment group was not a statistically significant determinant of these markers at baseline. According to these results, estrogen and combined HRT do not differ in their abilities to oppose LDL oxidation in vitro or systemic oxidative stress in vivo, but have differential effects on blood lipids.     

Bridging advanced glycation end product, receptor for advanced glycation end product and nitric oxide with hormonal replacement/estrogen therapy in healthy versus diabetic postmenopausal women: a perspective

Cardiovascular diseases (CVD) are the most significant cause of death in postmenopausal women. The loss of estrogen biosynthesis with advanced age is suggested as one of the major causes of higher CVD in postmenopausal women. While some studies show beneficial effects of estrogen therapy (ET)/hormonal replacement therapy (HRT) in the cardiovascular system of healthy postmenopausal women, similar studies in diabetic counterparts contradict these findings. In particular, ET/HRT in diabetic postmenopausal women results in a seemingly detrimental effect on the cardiovascular system. In this review, the comparative role of estrogens is discussed in the context of CVD in both healthy and diabetic postmenopausal women in regard to the synthesis or expression of proinflammatory molecules like advanced glycation end products (AGEs), receptor for advanced glycation end products (RAGEs), inducible nitric oxide synthases (iNOS) and the anti-inflammatory endothelial nitric oxide synthases (eNOS). The interaction of AGE-RAGE signaling with molecular nitric oxide (NO) may determine the level of reactive oxygen species (ROS) and influence the overall redox status of the vascular microenvironment that may further determine the ultimate outcome of the effects of estrogens on the CVD in healthy versus diabetic women.     

Separate myocardial ethanolamine phosphotransferase activities responsible for plasmenylethanolamine and phosphatidylethanolamine synthesis

Ethanolamine phosphotransferase (EPT) is a key enzyme responsible for the synthesis of ethanolamine glycerophospholipids. Plasmenylethanolamine is a predominant molecular subclass of ethanolamine glycerophospholipids in the heart. The present study was designed to identify the selective use of 1-O-alk-1'-enyl-2-acyl-sn-glycerol as a substrate for EPT as a mechanism responsible for the predominance of plasmenylethanolamine in the rabbit heart. EPT activity in rabbit myocardial membranes using 1,2-diacyl-sn-glycerol as substrate is activated by Mn2+, inhibited by dithiobisnitrobenzoic acid (DTNB) and is unaffected by Ca2+. In contrast, ethanolamine phosphotransferase activity using 1-O-alk-1'-enyl-2-acyl-sn-glycerol as substrate is inhibited by Mn2+ and Ca2+, but is activated by DTNB. Additionally, ethanolamine phosphotransferase activity using 1-O-alk-1'-enyl-2-acyl-sn-glycerol substrate was more sensitive to thermal denaturation compared with that of 1,2-diacyl-sn-glycerol. Taken together, these results suggest that separate ethanolamine phosphotransferase activities are present in heart membranes that are responsible for the synthesis of phosphatidylethanolamine and plasmenylethanolamine.     

Circulating endothelin influences area postrema neurons

The recently described endothelium-derived constricting factor endothelin (ET) is a 21 amino acid peptide which is the most potent endogenous vasoconstrictor yet described. Binding sites for this peptide have been demonstrated within the circumventricular structures of the brain. One of these structures, the area postrema (AP), has been implicated in central cardiovascular control mechanisms. We have recently demonstrated that microinjection of ET into this structure results in dose-dependent changes in mean arterial blood pressure. The present studies were undertaken to test the hypothesis that ET elicits these effects as a result of influences on the activity of AP neurons. Using extracellular single unit recording techniques we have examined the effects of systemic administration of ET on the activity of AP neurons. A total of 60 AP neurons were tested for effects of ET (0.1-10.0 pmol) of which the spontaneous activity of 32 showed rapid (modified frequency of action potentials in the 60s following ET), reversible (return to baseline activity within 10 m) responses to this peptide. The initial response of the majority (84%) of AP neurons influenced by ET was excitatory, while a smaller proportion of AP neurons were inhibited (16%) by systemic administration of this peptide. We have also examined whether such excitatory effects were specific to AP neurons by comparing the above response characteristics to those observed in neurons in the adjacent commissural NTS. Such recordings demonstrated predominantly inhibitory (84% of influenced cells) responses of this group of NTS neurons to ET. While these findings demonstrate specific excitatory effects of systemic ET on the activity of AP neurons they also suggest a potential role for this peptide in controlling the activity of NTS neurons. These studies provide evidence that circulating ET influences AP neuronal function, although they offer no definitive information as to the specific site of action.     

The clinical relevance of the relationship between estrogen and cognition in women

Randomized controlled trials (RCTs) and observational and longitudinal studies provide positive, albeit, inconsistent evidence that estrogen might protect against cognitive decline in postmenopausal women. The fact that the Women's Health Initiative Memory Study (WHIMS), the largest RCT to date, failed to find that estrogen therapy (ET) had a protective effect against cognitive aging led to the formulation of the critical period hypothesis which holds that ET will effectively protect against memory decline when it is initiated around the time of menopause but not when considerable time has elapsed since the menopause. Evidence from basic neuroscience, and from rodent, nonhuman primate, and human studies that supports this theory is presented. Although much work remains to be done on the timing of initiation of treatment, on the most effective hormonal compounds and on their routes of administration, the hope is that, eventually, hormonal treatments may be able to attenuate or prevent the decline in aspects of cognition that occur with normal aging.     

Impact of Estrogen Therapy on Lymphocyte Homeostasis and the Response to Seasonal Influenza Vaccine in Post-Menopausal Women

It is widely recognized that changes in levels of ovarian steroids modulate severity of autoimmune disease and immune function in young adult women. These observations suggest that the loss of ovarian steroids associated with menopause could affect the age-related decline in immune function, known as immune senescence. Therefore, in this study, we determined the impact of menopause and estrogen therapy (ET) on lymphocyte subset frequency as well as the immune response to seasonal influenza vaccine in three different groups: 1) young adult women (regular menstrual cycles, not on hormonal contraception); 2) post-menopausal (at least 2 years) women who are not receiving any form of hormone therapy (HT) and 3) post-menopausal hysterectomized women receiving ET. Although the numbers of circulating CD4 and CD20 B cells were reduced in the post-menopausal group receiving ET, we also detected a better preservation of naïve B cells, decreased CD4 T cell inflammatory cytokine production, and slightly lower circulating levels of the pro-inflammatory cytokine IL-6. Following vaccination, young adult women generated more robust antibody and T cell responses than both post-menopausal groups. Despite similar vaccine responses between the two post-menopausal groups, we observed a direct correlation between plasma 17β estradiol (E2) levels and fold increase in IgG titers within the ET group. These findings suggest that ET affects immune homeostasis and that higher plasma E2 levels may enhance humoral responses in post-menopausal women.     

Vascular effects of aromatase inhibitors: data from clinical trials

Aromatase inhibitors (AIs) are becoming the endocrine treatment of first choice for postmenopausal women with hormone receptor-positive breast cancer and are under investigation for use in breast cancer prevention. AIs reduce circulating estrogen to barely detectable concentrations. It is possible that such a low concentration will be deleterious to the vascular system since estrogen receptors are known to be in the cell walls of blood vessels and estrogen is thought to be important in maintaining blood vessel integrity. Because most women who present with primary breast cancer are cured by surgery and systemic therapy and the major cause of female death is vascular disease, it is particularly important to investigate the vascular side effects of AIs in current breast cancer adjuvant and prevention trials. In order to set the vascular toxicities of AIs reported in the current adjuvant trials into context, here we compare them with the toxicities seen during treatment with hormone replacement therapy (HRT) and selective estrogen receptor modulators (SERMs). Clinical trial evidence indicates that HRT increases risk of coronary heart disease (CHD) whereas SERMs and AIs (to date) appear to be neutral. Cerebrovascular disease and venous thromboembotic events are increased by HRT and SERMs but appear to be unaffected by treatment with AIs. Cognitive function is also considered here since it may also have a vascular component and is potentially a serious potential side effect/benefit of AIs. Recent studies indicate that HRT has a small detrimental effect on cognitive function and is associated with a doubling of the incidence of dementia. A comprehensive study of the SERM, raloxifene, on cognitive function showed no significant effect. There are no definitive reported studies investigating tamoxifen and none for AIs on cognitive function, although there is one in progress in the context of the IBIS II prevention trial which compares anastrozole to placebo in women at high risk. At present concerns about deleterious vascular side effects are confined to HRT and SERMs. However, we have few long-term data using AIs for the treatment and prevention of breast cancer.     

Pulmonary vasodilation to endothelin isopeptides in vivo is mediated by potassium channel activation

The present study was undertaken to investigate the effects of endothelin (ET) isopeptides on the pulmonary vascular bed of the intact spontaneously breathing cat under conditions of constant pulmonary blood flow and left atrial pressure. When pulmonary vasomotor tone was actively increased by intralobar infusion of U-46619, intralobar bolus injections of ET-1 (1 microgram), ET-2 (1 microgram), and ET-3 (3 micrograms) produced marked reductions in pulmonary and systemic vascular resistances. The pulmonary vasodilator response to each ET isopeptide was not altered by atropine (1 mg/kg iv), indomethacin (2.5 mg/kg iv), and ICI 118551 (1 mg/kg iv) but was significantly diminished by glybenclamide (5 mg/kg iv). This dose of glybenclamide significantly diminished the decrease in lobar arterial and systemic arterial pressures in response to intralobar injection of pinacidil (30 and 100 micrograms) and cromakalim (10 and 30 micrograms), whereas pulmonary vasodilator responses to acetylcholine (0.03 and 0.1 microgram), prostaglandin I2 (0.1 and 0.3 microgram), and isoproterenol (0.03 and 0.1 microgram) were not altered. The systemic vasodilator response to each ET isopeptide was not changed by glybenclamide or by the other blocking agents studied. The present data comprise the first publication demonstrating that ET-1, ET-2, and ET-3 dilate the pulmonary vascular bed in vivo. The present data further suggest that the pulmonary vasodilator response to ET isopeptides depends, in part, on activation of potassium channels and is mediated differently from the systemic vasodilator response to these substances. Contrary to earlier work, the present data indicate the pulmonary vascular response to ET isopeptides does depend on the preexisting level of pulmonary vasomotor tone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reprogramming of cell junction modules during stepwise epithelial to mesenchymal transition and accumulation of malignant features in vitro in a prostate cell model

Epithelial to mesenchymal transition (EMT) is pivotal in tumor metastasis. Our previous work reported an EMT model based on primary prostate epithelial cells (EP156T) which gave rise to cells with mesenchymal phenotype (EPT1) without malignant transformation. To promote prostate cell transformation, cells were maintained in saturation density cultures to select for cells overriding quiescence. Foci formed repeatedly following around 8 weeks in confluent EPT1 monolayers. Only later passage EPT1, but not EP156T cells of any passage, could form foci. Cells isolated from the foci were named EPT2 and formed robust colonies in soft agar, a malignant feature present neither in EP156T nor in EPT1 cells. EPT2 cells showed additional malignant traits in vitro, including higher ability to proliferate following confluence, higher resistance to apoptosis and lower dependence on exogenous growth factors than EP156T and EPT1 cells. Microarray profiling identified gene sets, many of which belong to cell junction modules, that changed expression from EP156T to EPT1 cells and continued to change from EPT1 to EPT2 cells. Our findings provide a novel stepwise cell culture model in which EMT emerges independently of transformation and is associated with subsequent accumulation of malignant features in prostate cells. Reprogramming of cell junction modules is involved in both steps.     

Current medical treatment of estrogen receptor-positive breast cancer

Approximately 80% of breast cancers(BC) are estrogen receptor(ER)-positive and thus endocrine therapy(ET) should be considered complementary to surgery in the majority of patients. The advantages of oophorectomy, adrenalectomy and hypophysectomy in women with advanced BC have been demonstrated many years ago, and currently ET consist of(1) ovarian function suppression(OFS), usually obtained using gonadotropinreleasing hormone agonists(Gn RHa);(2) selective estrogen receptor modulators or down-regulators(SERMs or SERDs); and(3) aromatase inhibitors(AIs), or a combination of two or more drugs. For patients aged less than 50 years and ER+ BC, there is no conclusive evidence that the combination of OFS and SERMs(i.e., tamoxifen) or chemotherapy is superior to OFS alone. Tamoxifen users exhibit a reduced risk of BC, both invasive and in situ, especially during the first 5 years of therapy, and extending the treatment to 10 years further reduced the risk of recurrences. SERDs(i.e., fulvestrant) are especially useful in the neoadjuvant treatment of advanced BC, alone or in combination with either cytotoxic agents or AIs. There are two types of AIs: type Ⅰ are permanent steroidal inhibitors of aromatase, while type Ⅱ are reversible nonsteroidal inhibitors. Several studies demonstrated the superiority of the third-generation AIs(i.e., anastrozole and letrozole) compared with tamoxifen, and adjuvant therapy with AIs reduces the recurrence risk especially in patients with advanced BC. Unfortunately, some cancers are or became ET-resistant, and thus other drugs have been suggested in combination with SERMs or AIs, including cyclin-dependent kinase 4/6 inhibitors(palbociclib) and mammalian target of rapamycin(m TOR) inhibitors, such as everolimus. Further studies are required to confirm their real usefulness.     

Effects of endothelin and relaxin on rat uterine segment contractility.

In order to determine the effects of endothelin (ET) and relaxin on uterine contractility, immature female rats were treated with estrogen (E, 1 microgram s.c., Days 1-3) or estrogen and progesterone (2 mg s.c. [E + P], Days 2 and 3), and killed; the uterine horns were removed and suspended in muscle baths. Initially, we determined the contractile response to varying doses of ET and how this response was altered by pretreatment with progesterone. Uterine strips from animals treated with E + P (n = 10) were less sensitive to the stimulatory effects of ET than were strips from E-treated animals (n = 10). This difference was significant at ET doses above 2.5 nM. After completion of the dose-response studies, contractile patterns in response to ET and relaxin were then studied in animals treated with E (n = 10) or E + P (n = 9). ET (5 nM) significantly increased uterine contractility, mostly through an effect on the frequency of contractions (p less than 0.01). Relaxin (25 ng/ml) decreased contractility, affecting all contractile parameters measured (p less than 0.01). ET stimulated contractility in uterine horn segments previously inhibited by relaxin (p less than 0.01), and relaxin reduced the increased contractility produced by earlier exposure to ET (p less than 0.01). These data indicate that ET and relaxin can interact reversibly to control contractility in uterine horn segments in vitro, and that progesterone pretreatment can diminish the contractile response to the stimulatory effects of ET.