Effect of tamoxifen on serum cholesterol and lipoproteins during chemohormonal therapy

Confounding Effects of Tamoxifen: Cautionary and Practical Considerations for the Use of Tamoxifen-Inducible Mouse Models in Atherosclerosis Research-Brief Report

BACKGROUND

In recent years, fate-mapping lineage studies in mouse models have led to major advances in vascular biology by allowing investigators to track specific cell populations in vivo. One of the most frequently used lineage tracing approaches involves tamoxifen-inducible CreERT-LoxP systems. However, tamoxifen treatment can also promote effects independent of Cre recombinase activation, many of which have not been fully explored.

METHODS

To elucidate off-target effects of tamoxifen, male and female mice were either unmanipulated or injected with tamoxifen or corn oil. All mice received PCSK9 (proprotein convertase subtilisin/kexin type 9)-AAV (adeno-associated virus) injections and a modified Western diet to induce hypercholesterolemia. After 2 weeks, serum cholesterol and liver morphology were assessed. To determine the duration of any tamoxifen effects in long-term atherosclerosis experiments, mice received either 12 days of tamoxifen at baseline or 12 days plus 2 sets of 5-day tamoxifen boosters; all mice received PCSK9-AAV injections and a modified Western diet to induce hypercholesterolemia. After 24 weeks, serum cholesterol and aortic sinus plaque burden were measured.

RESULTS

After 2 weeks of atherogenic treatment, mice injected with tamoxifen demonstrated significantly reduced serum cholesterol levels compared with uninjected- or corn oil-treated mice. However, there were no differences in PCSK9-mediated knockdown of LDL (low-density lipoprotein) receptors between the groups. Additionally, tamoxifen-treated mice exhibited significantly increased hepatic lipid accumulation compared with the other groups. Finally, the effects of tamoxifen remained for at least 8 weeks after completion of injections, with mice demonstrating persistent decreased serum cholesterol and impaired atherosclerotic plaque formation.

CONCLUSIONS

In this study, we establish that tamoxifen administration results in decreased serum cholesterol, decreased plaque formation, and increased hepatic lipid accumulation. These alterations represent significant confounding variables in atherosclerosis research, and we urge future investigators to take these findings into consideration when planning and executing their own atherosclerosis experiments.

Anti-hyperplastic effects of the Dacryodes edulis (Burseraceae) leaves aqueous extract on tamoxifen-induced endometrium hyperplasia on Wistar rat

OBJECTIVES

Combining tamoxifen, the most common breast cancer hormonal therapy, with natural antitumor substances may prevent its hyperplastic effects on the uterine endometrium. Dacryodes edulis (DE) is traditionally recommended for the treatment of cancerous diseases. To investigate its antiproliferative properties, the present study was designed to assess the ability of the combined administration of tamoxifen with the aqueous extract of DE leaves to inhibit the trophic effect of this hormone therapy on rat uterine endometrium without compromising its non-proliferative effect on breast tissue.

METHODS

Ovariectomized (OVX) female Wistar rats were simultaneously treated with tamoxifen (10 mg/kg) intraperitoneally and DE leaves (at doses of 25, 50 and 100 mg/kgBW) by gavage. Control groups received either distilled water or tamoxifen alone. Treatments lasted 37 days. The 38th day, animals were sacrificed under anesthesia (diazepam: 10 mg/kgBW and ketamine: 50 mg/kgBW). The relative uterine weight was determined and the histological analysis of the uterus and mammary gland was performed. The oxidative status of the uterus was assessed and the levels of cholesterol and estradiol were evaluated in serum and uterus.

RESULTS

Tamoxifen increased uterine weight and induced endometrial hyperplasia. This effect was associated with increased uterine levels of cholesterol (164.22%; p < 0.001), estradiol (927.5%; p < 0.001) and malondiadehyde (86%; p < 0.05), but unchanged antioxidant enzymes activities. The administration of DE leaves unchanged tamoxifen-increased uterine weight but reduced uterine epithelium hypertrophy (56.4%; p < 0.01). DE also increased uterine levels of malondiadehyde and antioxidant enzymes. The levels of estradiol and cholesterol in the uterus decreased while no changes were observed in the mammary gland of animals treated with tamoxifen alone or in co-administration with DE.

CONCLUSIONS

D. edulis has antiproliferative properties and could complement endocrine therapy of estrogen-dependent breast cancer.

Comparison of changes in lipid profiles of premenopausal women with early-stage breast cancer treated with different endocrine therapies

Adjuvant endocrine therapy improves the prognosis of early breast cancer with hormone receptor positivity. However, there is no systematic report on the effect of endocrine therapy (particularly ovarian function suppression, OFS) on serum lipids in premenopausal women. This retrospective cohort study aimed to determine whether various endocrine treatments had different effects on blood lipids. This study enrolled 160 premenopausal patients with stage I-III breast cancer in eastern China. The initial diagnostic information was retrieved from patient's medical records, including age at the time of diagnosis, tumor characteristics, anticancer treatment and past medical history. The changes in blood lipids in patients receiving different types of endocrine therapy were compared at the 3rd, 6th, 12th, and 24th months after initiating endocrine therapy. Generalized linear mixed model was used in our analyses. Our data revealed that low-density lipoprotein cholesterol (LDL-C) levels in patients with tamoxifen (TAM) were significantly lower in the 6th, 12th, and 24th months than that in the 3rd month, while high-density lipoprotein cholesterol (HDL-C) levels in the 6th, 12th, and 24th months were significantly higher than that in the 3rd month, indicating that blood lipid levels generally improved with time. While in TAM plus OFS group, HDL-C levels were significantly higher in the 24th month than in the 3rd month, total cholesterol (TC) levels were significantly higher in the 24th month than in the 6th month. The lipid profiles of OFS plus aromatase inhibitor (AI) group did not show significant differences at any time point but were significantly higher than those of the other two groups especially in LDL and TC. TAM group tended to have lower serum lipid levels. With longer follow-up, no statistically significant difference in values was observed between TAM and TAM plus OFS groups at various time points. Compared with the other two groups, OFS plus AI group presented an increasing trend toward LDL-C and TC. The risk of dyslipidemia requires further investigation using a large sample size.

Integrating gene expression and clinical data to identify drug repurposing candidates for hyperlipidemia and hypertension

Discovering novel uses for existing drugs, through drug repurposing, can reduce the time, costs, and risk of failure associated with new drug development. However, prioritizing drug repurposing candidates for downstream studies remains challenging. Here, we present a high-throughput approach to identify and validate drug repurposing candidates. This approach integrates human gene expression, drug perturbation, and clinical data from publicly available resources. We apply this approach to find drug repurposing candidates for two diseases, hyperlipidemia and hypertension. We screen >21,000 compounds and replicate ten approved drugs. We also identify 25 (seven for hyperlipidemia, eighteen for hypertension) drugs approved for other indications with therapeutic effects on clinically relevant biomarkers. For five of these drugs, the therapeutic effects are replicated in the All of Us Research Program database. We anticipate our approach will enable researchers to integrate multiple publicly available datasets to identify high priority drug repurposing opportunities for human diseases.

Selective estrogen receptor modulators (SERMs) affect cholesterol homeostasis through the master regulators SREBP and LXR

Selective estrogen receptor modulators (SERMs) are nonsteroidal drugs that display an estrogen-agonist or estrogen-antagonist effect depending on the tissue targeted. SERMs have attracted great clinical interest for the treatment of several pathologies, most notably breast cancer and osteoporosis. There is strong evidence that SERMs secondarily affect cholesterol metabolism, although the mechanism has not been fully elucidated. In this study, we analysed the effect of the SERMs tamoxifen, raloxifene, and toremifene on the expression of lipid metabolism genes by microarrays and quantitative PCR in different cell types, and ascertained the main mechanisms involved. The three SERMs increased the expression of sterol regulatory element-binding protein (SREBP) target genes, especially those targeted by SREBP-2. In consonance, SERMs increased SREBP-2 processing. These effects were associated to the interference with intracellular LDL-derived cholesterol trafficking. When the cells were exposed to LDL, but not to cholesterol/methyl-cyclodextrin complexes, the SERM-induced increases in gene expression were synergistic with those induced by lovastatin. Furthermore, the SERMs reduced the stimulation of the transcriptional activity of the liver X receptor (LXR) by exogenous cholesterol. However, their impact on the expression of the LXR canonical target ABCA1 in the presence of LDL was cell-type dependent. These actions of SERMs were independent of estrogen receptors. We conclude that, by inhibiting the intracellular trafficking of LDL-derived cholesterol, SERMs promote the activation of SREBP-2 and prevent the activation of LXR, two master regulators of cellular cholesterol metabolism. This study highlights the impact of SERMs on lipid homeostasis regulation beyond their actions as estrogen receptor modulators.

Multi-organ system for the evaluation of efficacy and off-target toxicity of anticancer therapeutics

A pumpless, reconfigurable, multi-organ-on-a-chip system containing recirculating serum-free medium can be used to predict preclinical on-target efficacy, metabolic conversion, and measurement of off-target toxicity of drugs using functional biological microelectromechanical systems. In the first configuration of the system, primary human hepatocytes were cultured with two cancer-derived human bone marrow cell lines for antileukemia drug analysis in which diclofenac and imatinib demonstrated a cytostatic effect on bone marrow cancer proliferation. Liver viability was not affected by imatinib; however, diclofenac reduced liver viability by 30%. The second configuration housed a multidrug-resistant vulva cancer line, a non-multidrug-resistant breast cancer line, primary hepatocytes, and induced pluripotent stem cell-derived cardiomyocytes. Tamoxifen reduced viability of the breast cancer cells only after metabolite generation but did not affect the vulva cancer cells except when coadministered with verapamil, a permeability glycoprotein inhibitor. Both tamoxifen alone and coadministration with verapamil produced off-target cardiac effects as indicated by a reduction of contractile force, beat frequency, and conduction velocity but did not affect viability. These systems demonstrate the utility of a human cell-based in vitro culture system to evaluate both on-target efficacy and off-target toxicity for parent drugs and their metabolites; these systems can augment and reduce the use of animals and increase the efficiency of drug evaluations in preclinical studies.

Tamoxifen affects glucose and lipid metabolism parameters, causes browning of subcutaneous adipose tissue and transient body composition changes in C57BL/6NTac mice

Tamoxifen is a selective estrogen receptor (ER) modulator which is widely used to generate inducible conditional transgenic mouse models. Activation of ER signaling plays an important role in the regulation of adipose tissue (AT) metabolism. We therefore tested the hypothesis that tamoxifen administration causes changes in AT biology in vivo. 12 weeks old male C57BL/6NTac mice were treated with either tamoxifen (n = 18) or vehicle (n = 18) for 5 consecutive days. Tamoxifen treatment effects on body composition, energy homeostasis, parameters of AT biology, glucose and lipid metabolism were investigated up to an age of 18 weeks. We found that tamoxifen treatment causes: I) significantly increased HbA1c, triglyceride and free fatty acid serum concentrations (p < 0.01), II) browning of subcutaneous AT and increased UCP-1 expression, III) increased AT proliferation marker Ki67 mRNA expression, IV) changes in adipocyte size distribution, and V) transient body composition changes. Tamoxifen may induce changes in body composition, whole body glucose and lipid metabolism and has significant effects on AT biology, which need to be considered when using Tamoxifen as a tool to induce conditional transgenic mouse models. Our data further suggest that tamoxifen-treated wildtype mice should be characterized in parallel to experimental transgenic models to control for tamoxifen administration effects.

Selective estrogen receptor modulators: tissue specificity and clinical utility

Selective estrogen receptor modulators (SERMs) are a diverse group of nonsteroidal compounds that function as agonists or antagonists for estrogen receptors (ERs) in a target gene-specific and tissue-specific fashion. SERM specificity involves tissue-specific expression of ER subtypes, differential expression of co-regulatory proteins in various tissues, and varying ER conformational changes induced by ligand binding. To date, the major clinical applications of SERMs are their use in the prevention and treatment of breast cancer, the prevention of osteoporosis, and the maintenance of beneficial serum lipid profiles in postmenopausal women. However, SERMs have also been found to promote adverse effects, including thromboembolic events and, in some cases, carcinogenesis, that have proven to be obstacles in their clinical utility. In this review, we discuss the mechanisms of SERM tissue specificity and highlight the therapeutic application of well-known and emergent SERMs.

Influence of gender on tamoxifen-induced biochemical changes in serum of rats

Tamoxifen, the widely prescribed drug in the prevention and therapy of breast cancer, may cause side effects which may be influenced by gender. The present study was undertaken to investigate the impact of gender on tamoxifen-induced toxic and biochemical changes following oral administration of tamoxifen at high dose level of 20 mg/kg once daily for a 2-week period in both male and female rats. The results showed marked increases in serum activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in female rats. In contrast, treatment with tamoxifen in male animals significantly decreased the activity of ALT, with a tendency for a decrease in serum AST levels. In female rats, a significant reduction in the serum activity of acid phosphatase (ACP) was noted, compared with a non-significant decrease in males. Non-significant changes in serum levels of alkaline phosphatase (ALP) were seen in both sexes. Tamoxifen lowered serum contents of total lipid and total cholesterol in both male and female rats. Serum levels of triglycerides were reduced in female rats as compared to a non-significant decrease in male animals. The serum albumin concentration was decreased in both male and female rats, while total protein was decreased only in female animals. Tamoxifen markedly increased serum levels of creatinine in female rats, compared with a non-significant rise in males. Total serum contents of calcium were similarly reduced in both males and females. This is the first study which points to gender-related differences in tamoxifen-induced toxic and metabolic changes in rats. The results indicated that females are more susceptible than males to tamoxifen toxicity, probably due to the ability of tamoxifen to antagonize the action of estrogen in females.

Oxydation radiolytique du tamoxifène par les radicaux libres ·OH et (ou) HO·2

Tamoxifen is the most widely used antiestrogen in the treatment of breast cancer. In this work, we have studied its antioxidant properties. We have investigated the ability of tamoxifen to scavenge, in vitro, ·OH and (or) HO·2 free radicals that are produced by water radiolysis. Aqueous solutions of tamoxifen of concentrations ranging between 10-5 and 2.5 × 10-5 M have been irradiated (γ 137Cs) in aerated acidic medium (H3PO4 10-3 M or HCOOH 10-1 M). The results show that tamoxifen reacts quantitatively with ·OH free radicals but does not react with HO·2 free radicals under our experimental conditions.Key words: tamoxifen, antioxidant, oxygenated free radicals, radiolysis.

Prognostic effect of amenorrhoea and elevated serum gonadotropin levels induced by adjuvant chemotherapy in premenopausal node-positive breast cancer patients

The purpose of the study was to determine the correlation between prognosis and chemotherapy induced amenorrhoea or elevated gonadotropin levels in node-positive breast cancer patients. Since we have previously found a better prognosis in patients with more profound leucopenia induced by adjuvant chemotherapy, we examined whether this effect was mediated through more efficient induction of amenorrhoea. The study population consisted of 126 premenopausal, primarily operable, node-positive breast cancer patients treated with cyclophosphamide, methotrexate and 5-fluorouracil (CMF) adjuvant chemotherapy at the Department of Oncology, Helsinki University Central Hospital between 1990 and 1993. 12 months after the beginning of adjuvant chemotherapy, the patients were divided into groups with respect to their menstrual function (regular menstruation, irregular menstruation or amenorrhoea). Information about menstruation status and serum concentration of follicle stimulating hormone (FSH) and oestradiol were recorded at 12 and 24 months from the beginning of adjuvant chemotherapy. Median follow-up time was 72 months. Women who experienced amenorrhoea or had irregular menstruation after chemotherapy had a significantly better 5-year disease-free survival (DFS) in univariate analysis than women who continued to menstruate (P = 0.02). Amenorrhoea and irregular menstruation were associated with a better DFS among patients with oestrogen receptor (ER) positive primary tumours (P = 0.007), whereas no such association was found in ER negative cases (P = 0.86). 5-year overall survival (OS) in univariate analysis was also better in patients who experienced amenorrhoea (81%) or who had irregular menstruation (90%) after chemotherapy as compared with patients with regular menstruation (68%; 81 versus 68%, P = 0.05). The serum FSH level did not correlate significantly with outcome irrespective of the cut-off point chosen. Nodal status, tumour size and menstruation status after chemotherapy were also significantly associated with DFS in a multivariate analysis. The menstruation status after chemotherapy lost its significance for OS in a multivariate analysis whilst the number of affected lymph nodes, tumour size and oestrogen/progesterone receptor status retained their impact. There was no association between the degree of leucopenia and induction of amenorrhoea by CMF. Chemotherapy-induced ovarian function suppression (amenorrhoea/irregular menstruation) after chemotherapy had a favourable effect on DFS in premenopausal breast cancer patients. The post-chemotherapy menstruation status is a clinically usable marker for sufficient endocrine effect of chemotherapy in ER/PR-positive patients in all premenopausal age groups. FSH level seemed to be a less reliable indicator of the castration effect of adjuvant chemotherapy in this study.

Lipid and lipoprotein ratios as risk factors of atherosclerosis in patients with chronic renal insufficiency (CRI)

The serum levels of lipids, apolipoproteins and lipoprotein ratios in 19 healthy persons and 20 patients with uraemia not dialyzed were determined. Based on creatinine level the patients were divided into two groups: L (serum creatinine 2-5 mg/dl) and H (serum creatinine 5-10 mg/dl). Dyslipoproteinaemia in uraemic patients is already manifested in the early stages of the disease through its abnormal apolipoproteins rather than lipid profile and it suggests a high risk of atherosclerosis.

Pharmacotherapy of dyslipidemia in postmenopausal women: weighing the evidence

In the United States, coronary heart disease (CHD) is the leading cause of death in women. The incidence of CHD rises dramatically in women following menopause, which can be partially attributed to a more atherogenic lipoprotein profile. For years, observational and epidemiological data have suggested that estrogen and progesterone therapy reduced CHD end points. However, the first prospective trial that evaluated hormone replacement therapy (HRT) for secondary CHD prevention demonstrated no positive cardiovascular benefit of HRT compared with placebo. In interventional studies, the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA)reductase inhibitors significantly reduced CHD outcomes in postmenopausal women, and these agents have emerged as the drugs of choice for primary and secondary CHD prevention. The selective estrogen receptor modulators (SERMs) may have a role in CHD prevention, but long-term clinical trials evaluating end points are needed. An evidence-based approach is necessary when deciding the appropriate pharmacotherapy of dyslipidemia in postmenopausal women.

Raloxifene, a new selective estrogen receptor modulator

There is evidence from observational studies that estrogen replacement therapy in postmenopausal women can reduce the rates of morbidity and mortality of atherosclerotic heart disease. The mechanism of this cardiovascular protective effect is not yet established, but favorable actions of hormone therapy on plasma lipids and vascular endothelial function have been proposed. Estrogens can also increase the risk of breast and uterine carcinoma. The new selective estrogen receptor modulator (SERM) raloxifene appears to have benefits similar to estrogen on plasma lipids and osteoporosis, but it does not affect the rate of uterine carcinoma as does tamoxifen and estrogen. Animal studies suggest an anti-atherosclerotic action of raloxifene, but this needs to be confirmed in long-term human studies.

Rehabilitation of breast cancer

Breast cancer is a complicated disease treated with multimodality therapy. Adult women of any age can develop breast cancer, and most will be cured. Treatment of primary disease is associated with more side effects than the cancer. The process of metastatic cancer to death can be long. The entire family is affected by breast cancer whether early or late. A rehabilitation program must address the physical and psychosocial aspects of breast cancer, both at presentation and at recurrence. For a patient with early breast cancer, lifestyle changes may be important. A primary goal of a rehabilitation program is that each breast cancer patient should become well informed regarding treatment and its consequences (Table 9) in order to continue with her life. Treatment to recover the patient to her former physical and psychosocial state, and therapy for chronic problems from breast cancer or its treatment, requires an approach distinct from that given to other malignancies. Issues regarding survival prevail in any rehabilitation program for both early and late breast cancer.

Effect of tamoxifen on cholesterol synthesis in HepG2 cells and cultured rat hepatocytes

The objective of this study was to investigate the mechanisms by which tamoxifen modifies cholesterol metabolism in cellular models of liver metabolism, HepG2 cells and rat hepatocytes. The effect of tamoxifen on cholesterol and triglyceride-palmitate synthesis was measured using isotopomer spectral analysis (ISA) and gas chromatography-mass spectrometry (GC-MS) and compared with the effects of progesterone, estradiol, the antiestrogen ICI 182,780, and an oxysterol, 25-hydroxycholesterol (25OHC). Cholesterol synthesis in cells incubated in the presence of either [1-(13)C]acetate, [U-13C]glucose, or [4,5-(13)C]mevalonate for 48 hours was reduced in the presence of 10 micromol/L tamoxifen and 12.4 micromol/L 25OHC in both HepG2 cells and rat hepatocytes. The ISA methodology allowed a clear distinction between effects on synthesis and effects on precursor enrichment, and indicated that these compounds did not affect enrichment of the precursors of squalene. Progesterone was effective in both cell types at 30 micromol/L and only in HepG2 cells at 10 micromol/L. Estradiol and ICI 182,780 at 10 micromol/L did not inhibit cholesterol synthesis. None of the compounds altered the synthesis of triglyceride-palmitate in either cell type. Treatment of cells with tamoxifen produced accumulation of three sterol precursors of cholesterol, zymosterol, desmosterol, and delta8 cholesterol. This pattern of precursors indicates inhibition of delta24,25 reduction in addition to the previously described inhibition of delta8 isomerase. We conclude that tamoxifen is an effective inhibitor of the conversion of lanosterol to cholesterol in cellular models at concentrations comparable to those present in the plasma of tamoxifen-treated individuals. Our findings indicate that this mechanism may contribute to the effect of tamoxifen in reducing plasma cholesterol in humans.

Women, dyslipoproteinemia, and estrogens

The most common cause of death in both men and women is coronary atherosclerosis, although atherosclerotic death in women occurs 5 to 10 years later than it does in men. Major risk factors predict coronary risk in both. Available evidence suggests that women benefit from cholesterol lowering just as men do. The role of exogenous estrogenic compounds in favorably affecting lipoprotein levels and promoting antiatherogenesis in both men and women is a promising area for future research.

The salubrious effect of tamoxifen [correction of Tamaxifen] on serum marker enzymes, glycoproteins, and lysosomal enzymes level in breast cancer woman

Tumour markers correlate strongly with prognosis based on tumour burden and surgical resectability. If chemotherapy is extremely effective in certain stage of the disease, the sensitive marker may be of great use in monitoring disease response and drug treatment. Hence, this study was launched to evaluate the changes in tumour marker enzymes like lactate dehydrogenase (LDH), glutamate oxaloacetate transaminase (SGOT), glutamate pyruvate transaminase (SGPT), alkaline phosphatase, and acid phosphatase in before and after 3 and 6 months tamoxifen treated breast cancer patients. In addition, the changes in serum glycoproteins viz., hexose, hexosamine, and sialic acid and lysosomal enzymes such as N-acetyl-beta-D-glucosaminidase, beta-D-galactosidase, and beta-D-glucuronidase were analysed in these patients. These values were compared with their age matched healthy control subjects. At 6 months evaluation, the tamoxifen treated postmenopausal breast cancer women showed a statistically significant decreased (p < 0.001, 0.05 respectively) levels of LDH, SGOT, SGPT, alkaline and acid phosphatases than their baseline values. Similarly, the levels of hexose, hexosamine, and sialic acid and N-acetyl-beta-D-glucosaminidase, beta-D-galactosidase, and beta-D-glucuronidase were decreased significantly (p < 0.001) in tamoxifen received postmenopausal women. The result of this study suggested that tamoxifen potentially retard the metastasis of breast cancer as well as the bone demineralisation in postmenopausal breast cancer women. Thus, tamoxifen may also have its antitumour activity through its beneficial effects on tumour marker enzymes and serum proteins in breast cancer women.

Blood chemistry profiles in menopausal women administered tamoxifen for breast cancer

1. Menopausal controls not administered estrogen replacement therapy (ERT), or menopausal women taking 10 mg of tamoxifen bid had serum samples collected. 2. When controls were compared to treatment, significant elevations in the TRI (triglycerides), SGOT (serum glutamic oxalacetic transaminase), SGPT (serum glutamic pyruvic transaminase) and the GGT (gamma gluteryl transferase) were found in the tamoxifen group. Liver enzymes were elevated but still within the normal range for the tamoxifen-treated group. 3. The results from this study suggest that the use of tamoxifen citrate for adjuvant therapy in women with breast cancer causes no major alterations in the blood chemistry of menopausal women. The elevations observed were still within the normal ranges of menopausal women with the exception of the triglycerides.

Plasma lipoproteins in patients with chronic renal failure (CRF)

The clinical picture in chronic renal failure (CRF) shows great variability depending on age, sex, aetiology of disease, grades of renal injury and type of treatment. Significant increases of triglycerides (TG), low-density lipoprotein cholesterol (LDL-chol) and and apo B concentrations, significant decreases of high-density lipoprotein cholesterol (HDL-chol) levels and apo A and apo AI concentrations, and no significant changes in total cholesterol (TC) have been shown in CRF patients. Significant increases of TC/HDL-chol, LDL-chol/HDL-chol, apo B/apo AI and apo B/LDL-chol ratios were also demonstrated. That indicates a high risk of atherosclerosis even when total cholesterol levels are in the normal range. There were highly significant and positive correlations between TC/HDL-chol and LDL-chol/HDL-chol ratios, apo B and LDL-chol concentrations as well as between the apo B/apo AI and LDL-chol/HDL-chol ratios.

Androgen receptor-mediated antagonism of estrogen-dependent low density lipoprotein receptor transcription in cultured hepatocytes

Postmenopausal women receiving hormone replacement therapy have a lower risk of coronary heart disease than women who do not receive hormone treatment. Multiple mechanisms are likely to underlie estrogen's cardioprotective action, including lowering of plasma low density lipoprotein (LDL) cholesterol. Using an in vitro system exhibiting normal regulation of LDL receptor (LDLR) gene transcription, we show that 17beta-estradiol activates the LDLR promoter in transiently transfected HepG2 cells. LDLR activation by estrogen in HepG2 cells is dependent on the presence of exogenous estrogen receptor, and the estrogen-responsive region of the LDLR promoter colocalizes with the sterol response element previously identified. The estrogen response is concentration dependent, saturable, and sensitive to antagonism by estrogen receptor antagonists. Further, we show that compounds with androgen receptor agonist activity attenuate the estrogen-induced up-regulation of LDLR in our model system. Progestins with androgen receptor agonist activity, such as medroxyprogesterone acetate, also suppress estrogen's effects on LDLR expression through their androgenic properties. Characterization of the interplay between these hormone receptors on the LDLR in vitro system may allow a better understanding of the actions of sex steroids on LDLR gene expression and their roles in cardiovascular disease.

A study of the effects of tamoxifen in the frail elderly: difficulties encountered in nursing home research

OBJECTIVE

This study was conducted in order to determine whether the effects of tamoxifen in elderly, frail nursing home residents are similar to those that have been previously reported for younger postmenopausal women.

DESIGN

A chart review study.

SETTING

The Jewish Home and Hospital for Aged (JHHA), a subacute long-term care facility.

PARTICIPANTS

One hundred fifty-eight women who had been at the JHHA at any time since 1986. One hundred ten had a history of breast cancer; 43 of these had been treated with tamoxifen while at the JHHA (Group I), and 66 had not (Group II). The remaining 49 women had no history of breast cancer (Group III).

MEASUREMENTS

Data were collected from the time of admission to the JHHA through August, 1994 on: chemistry profiles, bone fractures apparently not a consequence of metastasis, gynecological parameters, and thromboemboli.

RESULTS

The lack of pre-admission clinical information presented problems regarding research design and the interpretation of our findings. Nevertheless, compared to women who had not been treated with tamoxifen, treated women had a significantly elevated incidence of vaginal discharge (P = 0.01) and a lower prevalence of elevated total cholesterol (P = 0.04). Although not statistically significant, they also had decreased levels of low density lipoprotein cholesterol and an increased incidence of thromboemboli and bone fractures.

CONCLUSIONS

While some of the effects of tamoxifen in elderly, frail women are similar to those observed in younger, postmenopausal women, others may be different. Our results suggest a need for further innovative studies that focus on the consequences of tamoxifen treatment in the elderly, frail population.

Is it time to develop an optimal endocrine therapy for premenopausal patients with axillary node positive and negative breast cancer?

One hundred years ago ovarian ablation was shown to be an effective treatment for advanced breast cancer in premenopausal women. Since that time many different treatment modalities have been advocated to improve patient survival. The value of adjuvant ovarian ablation, however, has recently been established in the overview of breast cancer clinical trials. In fact, comparison of the efficacy of combination chemotherapy with earlier trials of oophorectomy demonstrate the superiority of oophorectomy. The effectiveness of chemotherapy may largely be the result of partial ovarian ablation produced in premenopausal patients. Based on this position, we propose a clinical trial that would establish the optimal therapy for premenopausal breast cancer. In addition, the beneficial effects of long-term tamoxifen as it pertains to serum lipids and bone density are highlighted. The use of tamoxifen maintenance in oophorectomized women might provide an optimal therapy for the control of breast cancer recurrence.

Third annual William L. McGuire Memorial Lecture. "Studies on the estrogen receptor in breast cancer"--20 years as a target for the treatment and prevention of cancer

In 1973, McGuire and Chamness (In: O'Malley BW and Means AR (ed) Receptors for Reproductive Hormones, Plenum Press) summarized their work on the estrogen receptor in animal and human breast tumors, and in so doing described a target for therapeutic intervention. At that time there were no clinically useful antiestrogens, but the subsequent development of tamoxifen for breast cancer therapy has revolutionized the approach to treatment. Long-term adjuvant tamoxifen adjuvant therapy (i.e., greater than one year) has proven efficacy to enhance the survival of breast cancer patients. In addition, because there is an associated 40% decrease in contralateral breast cancer during adjuvant tamoxifen therapy and tamoxifen maintains bone density and reduces fatal myocardial infarction, clinical trials to test the worth of tamoxifen as a preventive for breast cancer in high risk women have started in the United States, United Kingdom, and Italy. Initial concerns that long-term tamoxifen causes endometrial cancer have been placed in perspective and analyzed by a review of the literature. Tamoxifen only doubles the normal risk of detecting endometrial cancer (i.e., to 2 per 1,000 tamoxifen-treated women per year), and 80% of these cases are early stage, good prognosis disease. Annual gynecological examinations and education are essential to provide reassurance for patients. The success of tamoxifen has encouraged the development of new antiestrogens to exploit the estrogen receptor as a therapeutic target. Droloxifene and TAT-59 mimic the metabolite 4-hydroxytamoxifen in having a high affinity for the estrogen receptor (Jordan et al, J Endocrinol 75:305, 1977). These drugs appear to have a pharmacological profile similar to tamoxifen. In contrast, the new pure antiestrogens have a distinct mechanism of action and will be valuable either as a first line therapy for advanced breast cancer or as a second line endocrine therapy after the failure of long-term adjuvant tamoxifen therapy. Finally, a new strategy is being developed to exploit the target site specific action of antiestrogens. Raloxifene, an antiestrogen with high affinity for the estrogen receptor but only weak estrogenicity for the uterus, prevents rat mammary tumorigenesis and maintains bone density. The drug is to be evaluated as a treatment for osteoporosis, but may also prevent the development of breast and endometrial cancer in a broad group of treated subjects. The identification of the estrogen receptor as a target for therapeutic opportunities has proved to be extremely beneficial for the control of breast cancer and has the added potential to control osteoporosis and coronary heart disease in women.

Tamoxifen's role in chemoprevention of breast cancer: an update

Tamoxifen is an oral antiestrogen first used in metastatic breast cancer in the early 1970s. Large clinical trials were initiated in the late 1970s and early 1980s to test the drug's role as adjuvant therapy in early stage breast cancer. Observations of marked decreases in the development of contralateral breast cancer among tamoxifen recipients suggested potential for the drug in chemoprevention of breast cancer, and a large clinical trial to test the efficacy of tamoxifen in prevention of invasive breast cancer among women at increased risk was implemented in the United States in 1992. This paper reviews the rational for the clinical studies of tamoxifen as a chemopreventive agent for breast cancer and summarizes new information that has contributed to our understanding of tamoxifen's actions at the molecular and clinical levels. Current knowledge about the drug's mechanism of estrogenic and antiestrogenic action and its beneficial effects on blood lipids and bone metabolism will be presented. Recent research findings about DNA adduct formation and hepatic lesions, tamoxifen-associated gynecologic conditions, and the occurrence of second primary cancers in other organ systems will also be discussed.