Effects of tibolone and hormone replacement therapy on the breast of cynomolgus monkeys

Tibolone and Breast Tissue: a Review

The safety profile of hormone replacement therapy (HRT) on breast is still controversial. Tibolone is an option of treatment for climacteric syndrome of postmenopausal women. Its risk profile on breast is debated. This is an updated narrative review focusing on the impact of tibolone on breast. Particularly, we will report data from major preclinical and clinical studies regarding the effects of the use of this compound on breast tissue and breast density. Moreover, we will analyze and discuss the most relevant findings of the principal studies evaluating the relationship between tibolone and breast cancer risk. Our purpose is making all clinicians who are particularly involved in women's health more aware of the effects of this compound on breast and, thus, more experienced in the management of menopausal symptoms with this drug. According to the available literature, tibolone seems to be characterized by an interesting safety profile on breast tissue.

Hyperplastic and Neoplastic Lesions of the Mammary Gland in Macaques

Macaques provide an important animal model for the study of hormonal agents and their effects on risk biomarkers for breast cancer. A common criticism of this model is that spontaneous breast cancer has rarely been described in these animals. In this report, we characterize 35 mammary gland lesions ranging from ductal hyperplasia to carcinoma in situ and invasive ductal carcinoma in cynomolgus and rhesus macaques. Based on a retrospective analysis, we estimated the lifetime incidence of mammary gland neoplasia in aged female macaques to be about 6%. Hyperplastic lesions (n = 19) occurred segmentally along ducts and included such features as columnar alteration, micropapillary atypia, and fibroadenomatous change. in situ carcinomas (n = 8) included solid, comedo, cribriform, and micropapillary elements, encompassing 4 of the major architectural patterns seen in human lesions. invasive ductal carcinomas (n = 8) were generally solid, with prominent central necrosis and mineralization, often on a background of micropapillary ductal hyperplasia and in situ carcinoma. Cytologic changes of invasive lesions included increased mitoses, nuclear pleomorphism, extensive microinvasion, and stromal desmoplasia. Axillary lymph-node metastases were confirmed in 5 of the 8 invasive carcinomas. on immunohistochemistry, intraductal and invasive carcinomas had increased Ki67/MIB1 and HER2 expression and selective loss of estrogen and progesterone receptors. These findings suggest that breast cancer is an underreported lesion in macaques and highlight unique morphologic and molecular similarities in breast cancer between human and macaque species.

Use of ultrasound imaging for the diagnosis of abnormal uterine bleeding in the bonnet macaque ( Macaca radiata)

Ultrasound is a powerful, low-cost, non-invasive medical tool used by laboratory animal veterinarians for diagnostic imaging. Sonohysterography and transvaginal ultrasound are frequently used to assess uterine anomalies in women presenting with abnormal uterine bleeding (AUB). In the present study, we have evaluated the abdominal ultrasound of bonnet monkeys ( n = 8) showing spontaneous ovulatory ( n = 5) and anovulatory ( n = 3) AUB. The ovulatory ( n = 5) macaques showed cyclic AUB for 7-8 days. The anovulatory ( n = 3) macaques had irregular AUB with menstrual cycles of 40-45 days. The B-mode abdominal, colour Doppler and 3D ultrasound scans were performed during the proliferative phase of the menstrual cycle. Ultrasound examination revealed endometrial polyps in five macaques and endometrial hyperplasia in three animals. The width and length of endometrial polyps was around 0.5-1 cm (average 0.51 ± 0.23 cm × 0.96 ± 0.16 cm) with significant increase in endometrial thickness ( P < 0.0002). 3D ultrasound also showed a homogeneous mass in the uterine cavity and colour Doppler ultrasound showed increased vascularity in the endometrial polyps. Endometrial hyperplasia characteristically appeared as a thickened echogenic endometrium ( P < 0.0002). This study demonstrates the use of non-invasive ultrasound techniques in the diagnosis of AUB in macaques.

Osteoprotegerin (OPG), The Endogenous Inhibitor of Receptor Activator of NF-κB Ligand (RANKL), is Dysregulated in BRCA Mutation Carriers

Breast cancer development in BRCA1/2 mutation carriers is a net consequence of cell-autonomous and cell nonautonomous factors which may serve as excellent targets for cancer prevention. In light of our previous data we sought to investigate the consequences of the BRCA-mutation carrier state on RANKL/osteoprotegerin (OPG) signalling.

We analysed serum levels of RANKL, OPG, RANKL/OPG complex, oestradiol (E2), and progesterone (P) during menstrual cycle progression in 391 BRCA1/2-mutation carriers and 782 noncarriers. These studies were complemented by analyses of RANKL and OPG in the serum and mammary tissues of female cynomolgus macaques (n = 88) and serum RANKL and OPG in postmenopausal women (n = 150).

BRCA-mutation carriers had lower mean values of free serum OPG in particular in BRCA1-mutation carriers (p = 0.018) compared with controls. Among BRCA1/2 mutation carriers, lower OPG levels were associated with germline mutation locations known to confer an increased breast cancer risk (p = 0.003). P is associated with low OPG levels in serum and tissue, particularly in BRCA-mutation carriers (rho = − 0.216; p = 0.002). Serum OPG levels were inversely correlated (rho = − 0.545, p < 0.001) with mammary epithelial proliferation measured by Ki67 expression and increased (p = 0.01) in postmenopause.

The P–RANKL/OPG system is dysregulated in BRCA-mutation carriers. These and previously published data provide a strong rationale for further investigation of antiprogestogens or an anti-RANKL antibody such as denosumab for breast cancer prevention.

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Osteoprotegerin (OPG) is the endogenous inhibitor of Receptor Activator of NF-κB Ligand (RANKL)

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RANKL has been shown to be crucially important in progesterone-mediated breast carcinogenesis

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Serum OPG is regulated by progesterone and low in BRCA1/2 mutation carriers

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Low serum OPG is associated with increased proliferation in the mammary gland

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Antiprogestogens or anti-RANKL antibody (denosumab) may be new strategies for breast cancer prevention in BRCA1/2 carriers.

Preventing deadly cancers is a high priority of 21st century medicine. To find the most promising cancer causing targets which can be modulated using chemo-preventive drugs remains the biggest challenge. In this paper we show that OPG, which is the physiological antagonist of RANKL (a factor known to be crucially involved in breast carcinogenesis), is low in women who have inherited a gene mutation (i.e. in BRCA1 or 2) which puts them at extremely high risk of developing breast cancer. An antibody which mimics OPG might be a very attractive option in preventing breast cancer.

Is expression of rat breast matrix components influenced by estrogen, progestins and tibolone?

AIM

To study the effects of estrogen therapy, alone or combined with progestogens, and of tibolone on the expression of heparanase (HSPE), extracellular matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9), perlecan and proliferating cell nuclear antigen (PCNA) in normal breast tissue.

METHODS

Thirty 250-day-old Wistar rats were castrated and 3 weeks later received one of the following treatments by gavage for 5 weeks: (1) estradiol benzoate; (2) estradiol benzoate + medroxyprogesterone acetate; (3) estradiol benzoate + norethisterone acetate; (4) estradiol benzoate + dydrogesterone; (5) tibolone; (6) placebo. Following treatment, the expressions of mRNA for HSPE, MMP-2 and MMP-9 were analyzed by real-time PCR and the protein expressions of HSPE, MMP-2, MMP-9, perlecan and PCNA were quantified by immunohistochemistry.

RESULTS

There was a statistically significant difference among the groups for the expression of HSPE mRNA due to high levels in the tibolone group. The groups differed in terms of PCNA, with lower levels found in the tibolone group followed by the estradiol benzoate + dydrogesterone group. A statistically significant positive correlation was observed for PCNA versus perlecan and MMP-9.

CONCLUSIONS

There was no difference in the effects of combinations of estradiol and different progestogens on extracellular matrix components, and breast cell proliferation was associated with increases in perlecan and MMP-9.

Progestin effects on cell proliferation pathways in the postmenopausal mammary gland

Introduction

Menopausal hormone therapies vary widely in their effects on breast cancer risk, and the mechanisms underlying these differences are unclear. The primary goals of this study were to characterize the mammary gland transcriptional profile of estrogen + progestin therapy in comparison with estrogen-alone or tibolone and investigate pathways of cell proliferation in a postmenopausal primate model.

Methods

Ovariectomized female cynomolgus macaque monkeys were randomized into the following groups: placebo (Con), oral conjugated equine estrogens (CEE), CEE with medroxyprogesterone acetate (MPA) (CEE + MPA), and tibolone given at a low or high dose (Lo or Hi Tib). All study treatment doses represented human clinical dose equivalents and were administered in the diet over a period of 2 years.

Results

Treatment with CEE + MPA had the greatest effect on global mRNA profiles and markers of mammary gland proliferation compared to CEE or tibolone treatment. Changes in the transcriptional patterns resulting from the addition of MPA to CEE were related to increased growth factors and decreased estrogen receptor (ER) signaling. Specific genes induced by CEE + MPA treatment included key members of prolactin receptor (PRLR)/signal transducer and activator of transcription 5 (STAT5), epidermal growth factor receptor (EGFR), and receptor activator of nuclear factor kappa B (RANK)/receptor activator of nuclear factor kappa B ligand (RANKL) pathways that were highly associated with breast tissue proliferation. In contrast, tibolone did not affect breast tissue proliferation but did elicit a mixed pattern of ER agonist activity.

Conclusion

Our findings indicate that estrogen + progestin therapy results in a distinct molecular profile compared to estrogen-alone or tibolone therapy, including upregulation of key growth factor targets associated with mammary carcinogenesis in mouse models. These changes may contribute to the promotional effects of estrogen + progestin therapy on breast cancer risk.

Menopausal hormone therapy use in 17 European countries during the last decade

INTRODUCTION

The first 'Women's Health Initiative' (WHI) randomised controlled trial assessed use of continuous combined menopausal hormone therapy (cc-MHT). It was prematurely stopped because of an increased invasive breast cancer (BC), coronary heart disease (CHD), stroke and pulmonary embolism risk. Consequently, scientific societies recommended use of MHT at the lowest effective dose for the shortest duration. As a result, a sharp decline in MHT use occurred worldwide.

AIM

To report in a uniform way the change in MHT use in European countries. To evaluate whether the variability of the MHT changes were related to some medical indicators.

MATERIALS AND METHODS

IMS Health provided MHT sales data for the years 2002 till 2010 for 17 countries. We tested several hypotheses to explain the heterogeneity of MHT use changes.

RESULTS AND DISCUSSION

In 2002, the estimated MHT rate in women 45-69 years old varied considerably between countries ranging from less than 5% to more than 25%. In all countries a profound decrease occurred between 2002 and 2010, ranging from 50% to 77%. By the end of 2010, the MHT uptake was lower than 10% in all countries except in Finland. MHT use change was not correlated to MHT use and prevailing BC incidence at baseline, nor to the number of gynaecologists per 100,000 women or to the level of information about MHT.

CONCLUSION

The global MHT use experienced a sharp decrease in all the analysed countries, although some variability exists. The decrease was unrelated to the assessed parameters.

Distribution of cyclooxygenases 1 and 2 in the uterus and breast of cynomolgus monkeys-effects of hormone treatment

OBJECTIVE

The aim of this study was to compare the distribution and immunoreactivity of cyclooxygenase (COX) 1 and COX-2 in normal uterus and breast after long-term hormone therapy in postmenopausal monkeys.

METHODS

Female adult cynomolgus macaques were bilaterally ovariectomized 3 months before the initiation of hormone treatment. The animals were either treated (experiment 1) with conjugated equine estrogens (CEE), medroxyprogesterone acetate (MPA), CEE + MPA, or tamoxifen or designated as controls (C). In experiment 2, the animals were either treated with CEE, CEE + MPA, or tibolone or designated as C. Breast tissue and uteri were collected, fixed, and paraffin embedded. Immunohistochemistry assays for COX-1 and COX-2 were performed.

RESULTS

COX-1 immunostaining was decreased by tamoxifen and CEE treatment in the endometrial stroma and by CEE + MPA in the myometrium. COX-1 immunostaining of the breast epithelia was down-regulated by CEE + MPA, whereas other cell types in the breast seem to be less affected by hormone treatment.COX-2 immunoreactivity in the endometrial stroma was increased by CEE + MPA. In the glandular epithelium, CEE + MPA and tibolone treatment increased COX-2 immunostaining compared with CEE treatment only and no treatment at all (C). No effect from hormone treatment on COX-2 immunostaining was found in the myometrium. COX-2 immunostaining in the glandular epithelium of the breast was, in experiment 2, increased after CEE treatment compared with no treatment (C). No other effects by hormone therapy on COX-2 expression were found in the breast.

CONCLUSIONS

Our results show that COX-1 and COX-2 are differently distributed and regulated by hormones in the normal uterus and breast of ovariectomized macaques. COX-1 is prevailing in the uterus, whereas COX-2 is dominant in the mammary gland.

Coronary heart disease of females: lessons learned from nonhuman primates

The cynomolgus monkey model has contributed to significant advances regarding the understanding of coronary artery atherosclerosis of females. There are currently 8 million women in the United States living with heart disease, necessitating further study and understanding of this leading cause of morbidity and mortality for postmenopausal women. Specifically, studies involving the monkey model have allowed greater understanding of the effect of the stage of reproductive life, time since menopause, and the extent of subclinical atherosclerosis as determinates of estrogen-mediated effects on arteries. Utilizing the commonalities among monkeys and human beings, these studies have shown that postmenopausal atherosclerosis is associated with the premenopausal reproductive timeframe. In addition, monkey studies have shown that estrogen deficiency during the premenopausal stage is extremely relevant regarding the progression of atherosclerosis. After several postmenopausal years, however, studies have shown that estrogen has no beneficial effects on atherosclerosis progression and may, in fact, be deleterious. Studies using the monkey model are currently underway to investigate further uses and possibilities of postmenopausal hormone therapy for treating menopausal symptoms while protecting the breast and uterus and inhibiting the progression of coronary artery atherosclerosis. These studies will hopefully clarify the role of estrogen and eliminate the need for the possibly harmful progestin effects through the use of a highly selective estrogen receptor modulator.

Mammary gland and endometrial effects of testosterone in combination with oral estradiol and progesterone

OBJECTIVE

The goal of this pilot study was to evaluate the effects of testosterone (T) cotherapy on mammary gland and endometrial measures in a postmenopausal primate model.

METHODS

Twenty-five surgically postmenopausal cynomolgus monkeys were randomized by social group to receive daily treatment with (1) placebo, (2) oral micronized 17beta-estradiol (1 mg/d equivalent in women) + progesterone (200 mg/d equivalent in women) (E + P), or (3) E + P with T administered via subcutaneous pellets for 8 weeks at a high dose (15 mg) followed by 8 weeks at a low dose (1.5 mg) (E + P + T). The main outcome measures were breast and endometrial epithelial proliferation, as measured by Ki67/MIB1 immunolabeling.

RESULTS

Intralobular breast proliferation did not differ significantly among groups after 8 weeks of treatment but was marginally higher (P = 0.03) in the E + P + T group after 16 weeks of treatment. No significant increase in proliferation was seen for E + P alone. Comparable changes in mammary gland markers of estrogen-receptor activity were seen for the E + P and E + P + T groups. In the endometrium, the addition of T did not increase endometrial glandular proliferation or estrogen-receptor activity or result in any distinct histologic changes.

CONCLUSIONS

The findings of this study do not support the idea that T antagonizes the effects of combined hormone therapy on breast proliferation or markers of estrogen-receptor activity. Overall, the short-term effects of T cotherapy on the mammary gland and endometrium were minimal.

Safety and efficacy of tibolone in breast-cancer patients with vasomotor symptoms: a double-blind, randomised, non-inferiority trial

BACKGROUND

Vasomotor symptoms and bone loss are complications frequently induced by adjuvant treatment for breast cancer. Tibolone prevents both side-effects, but its effect on cancer recurrence is unknown. The aim of this study was to show non-inferiority of tibolone to placebo regarding risk of recurrence in breast-cancer patients with climacteric complaints.

METHODS

Between July 11, 2002, and Dec 20, 2004, women surgically treated for a histologically confirmed breast cancer (T(1-3)N(0-2)M(0)) with vasomotor symptoms were randomly assigned to either tibolone 2.5 mg daily or placebo at 245 centres in 31 countries. Randomisation was done by use of a centralised interactive voice response system, stratified by centre, with a block size of four. The primary endpoint was breast-cancer recurrence, including contralateral breast cancer, and was analysed in the intention-to-treat (ITT) and per-protocol populations; the margin for non-inferiority was set as a hazard ratio of 1.278. This study is registered with ClinicalTrials.gov, number NCT00408863.

FINDINGS

Of the 3148 women randomised, 3098 were included in the ITT analysis (1556 in the tibolone group and 1542 in the placebo group). Mean age at randomisation was 52.7 years (SD 7.3) and mean time since surgery was 2.1 years (SD 1.3). 1792 of 3098 (58%) women were node positive and 2185 of 3098 (71%) were oestrogen-receptor positive. At study entry, 2068 of 3098 (67%) women used tamoxifen and 202 of 3098 (6.5%) women used aromatase inhibitors. The mean daily number of hot flushes was 6.4 (SD 5.1). After a median follow-up of 3.1 years (range 0.01-4.99), 237 of 1556 (15.2%) women on tibolone had a cancer recurrence, compared with 165 of 1542 (10.7%) on placebo (HR 1.40 [95% CI 1.14-1.70]; p=0.001). Results in the per-protocol population were similar (209 of 1254 [16.7%] women in the tibolone group had a recurrence vs 138 of 1213 [11.4%] women in the placebo group; HR 1.44 [95% CI 1.16-1.79]; p=0.0009). Tibolone was not different from placebo with regard to other safety outcomes, such as mortality (72 patients vs 63 patients, respectively), cardiovascular events (14 vs 10, respectively), or gynaecological cancers (10 vs 10, respectively). Vasomotor symptoms and bone-mineral density improved significantly with tibolone, compared with placebo.

INTERPRETATION

Tibolone increases the risk of recurrence in breast cancer patients, while relieving vasomotor symptoms and preventing bone loss.

FUNDING

Schering-Plough (formerly NV Organon, Oss, Netherlands).

Selected Background Findings and Interpretation of Common Lesions in the Female Reproductive System in Macaques

The authors describe a selection of normal findings and common naturally occurring lesions in the reproductive system of female macaques, including changes in the ovaries, uterus, cervix, vagina, and mammary glands. Normal features of immature ovaries, uteri, and mammary glands are described. Common non-neoplastic lesions in the ovaries include cortical mineralization, polyovular follicles, cysts, ovarian surface epithelial hyperplasia, and ectopic ovarian tissue. Ovarian neoplasms include granulosa cell tumors, teratomas, and ovarian surface epithelial tumors. Common non-neoplastic uterine findings include loss of features of normal cyclicity, abnormal bleeding, adenomyosis, endometriosis, epithelial plaques, and pregnancy-associated vascular remodeling. Hyperplastic and neoplastic lesions of the uterus include endometrial polyps, leiomyomas, and rarely endometrial hyperplasia and endometrial adenocarcinoma. Vaginitis is common. Cervical lesions include endocervical squamous metaplasia, polyps, and papillomavirus-associated lesions. Lesions in the mammary gland are most often proliferative and range from ductal hyperplasia to invasive carcinoma. Challenges to interpretation include the normal or pathologic absence of menstrual cyclicity and the potential misinterpretation of sporadic lesions, such as epithelial plaques or papillomavirus-associated lesions. Interpretation of normal and pathologic findings is best accomplished with knowledge of the life stage, reproductive history, and hormonal status of the animal.

The Mammary Glands of Macaques

This review describes the normal biology and physiology of the mammary gland in macaques, including the typical histologic appearance across the life span (development, reproductive maturity, lactation, and senescence). The molecular events regulating breast morphogenesis are described, as well as systemic and local hormonal regulators of mammary gland proliferation, differentiation, and function. Similarities and differences to the human breast are described. Regulatory events are illuminated by discussion of genetically modified mouse models. Tissue response markers, including immunohistochemical markers of proliferation and other hormonally induced changes and studies to date, regarding the effects of exogenous hormones, are briefly summarized. In general, estrogens stimulate progesterone receptor expression and proliferation in the mammary gland, and combinations of estrogens and progestogens cause greater proliferation than estrogens alone. Evaluation of novel chemical agents in macaques requires careful evaluation of age and hormonal context to avoid the confounding effects of mammary gland development, past reproductive history, and other influences on mammary gland morphology. The expression of proliferation markers and progesterone receptors may be used as biomarkers to measure chemically induced hormonal effects.

Effects of tibolone and conventional HRT on the expression of estrogen and progesterone receptors in the breast

OBJECTIVE

There is evidence that long-term hormone replacement therapy (HRT) is associated with an increased breast cancer risk. The aim of this study was to assess the effects of tibolone on estrogen and progesterone receptors in comparison to the effects of conventional HRT in the breast of surgically postmenopausal macaques.

METHOD

Sixty macaques were bilaterally ovariectomized 3 months before hormonal treatment was initiated. The animals were randomized into four treatment groups, including tibolone (TIB), conjugated equine estrogens (CEE), conjugated equine estrogens+medroxyprogesterone acetate (CEE+MPA) and control animals (C). After 2 years treatment, breast tissues were collected, fixed and paraffin embedded. Immunohistochemistry assays with monoclonal antibodies for estrogen receptors (ERalpha and ERbeta) and progesterone receptors (PRA and PRB) were performed.

RESULTS

The expression of ERalpha was markedly decreased in the CEE+MPA group as compared to C and TIB groups. The TIB group was not different from the C and CEE groups. No significant differences were found for ERbeta immunostaining. The expression of PRA was strongly increased in the TIB group as compared to the C and CEE+MPA groups. Immunostaining of PRB was increased in the CEE and TIB treated animals as compared to both C and CEE+MPA groups.

CONCLUSIONS

Tibolone increased the expression of both PRA and PRB, without affecting ERalpha and ERbeta expression in the macaque breast. These findings indicate that the effects of tibolone in breast tissue could be mediated via differential regulation of PRA and PRB isoforms and therefore distinct from those observed with conventional HRT.

Effects of lasofoxifene on the uterus, vagina, and breast in ovariectomized cynomolgus monkeys (Macaca fascicularis)

OBJECTIVE

The purpose of this study was to assess the effects of lasofoxifene on the reproductive system in ovariectomized nonhuman primates.

STUDY DESIGN

This was a 2-year, randomized study. Adult female macaques (Macaca fascicularis) were assigned randomly into 5 groups: ovariectomized, placebo-treated controls (n = 22); sham-ovariectomized, placebo-treated controls (n = 24); ovariectomized animals given 0.021 mg Premarin kg/d (conjugated equine estrogen; n = 25); lasofoxifene at 1.0 mg/kg/d (n = 23); or lasofoxifene at 5.0 mg/kg/d (n = 25). Outcomes included organ weights and histopathologic findings.

RESULTS

Lasofoxifene did not increase uterine weight or endometrial thickness and did not change mammary, vaginal, or cervical histologic condition. Mild endometrial fibrosis and cystic change were seen in lasofoxifene-treated animals, in contrast to significant uterine weight increases and endometrial hyperplasia induced by conjugated equine estrogen.

CONCLUSION

Lasofoxifene did not increase uterine weight and produced minor histologic uterine changes at the doses that were given and had no effect on the breast, vagina, or cervix.

Effects of tibolone on estrogen biosynthesis in the mammary tissue of postmenopausal monkeys

OBJECTIVE

To evaluate the long-term effects of tibolone on estrone sulfate (E1S)-sulfatase activity in breast tissue in a primate model (Macaca fascicularis) in comparison with conventional hormone therapies.

DESIGN

Ovariectomized female animals (n = 112) were randomized into five groups and treated for 2 years. Treatment included tibolone at 0.05 mg/kg (LoTib, n = 23) or 0.2 mg/kg (HiTib, n = 23), conjugated equine estrogens at 0.042 mg/kg (CEE, n = 24), CEE + medroxyprogesterone acetate at 0.167 mg/kg (CEE+MPA, n = 21), or placebo (controls, n = 21). E1S-sulfatase activity was evaluated by incubating homogenized breast tissue with [H]-E1S. Thin-layer chromatography was performed to separate the products estrone (E1) and estradiol (E2). Histomorphometry was performed to measure the amount of epithelial and fat tissue in the mammary gland.

RESULTS

Significantly more E2 than E1 was produced in all groups. E1S-sulfatase activity did not differ among the groups. E1S-sulfatase activity was highest in HiTib animals with less fatty breasts (5.9 fmol total estrogen/mg of protein/min; P < or =0.05) and lowest in HiTib animals with more fatty breasts (2.8 fmol total estrogen/mg of protein/min; P = 0.004 relative to less fatty breasts).

CONCLUSIONS

We conclude that tibolone had a differential effect on local estrogen biosynthesis in animals with high and low breast fat content. Therefore, breast tissue composition affects the steroidogenic response to hormonal treatment.

Effects of estradiol with oral or intravaginal progesterone on risk markers for breast cancer in a postmenopausal monkey model

OBJECTIVE

To evaluate the effects of oral estradiol given with either oral or intravaginal micronized progesterone (P4) on risk biomarkers for breast cancer in a postmenopausal monkey model.

DESIGN

This experiment was a two-way crossover study in which 20 ovariectomized adult female cynomolgus macaques were treated (in equivalent doses for women) with oral estradiol (1 mg/d) + oral micronized P4 (200 mg/d) or intravaginal P4 delivered by Silastic rings (6- to 10-mg/d release rate). Hormone treatments lasted 2 months and were separated by a 1-month washout period. The primary outcome measure was breast epithelial proliferation.

RESULTS

Serum P4 concentrations were significantly greater in subjects receiving oral P4 (10.9 ng/mL) compared with intravaginal P4 (3.8 ng/mL) at 2 to 3 hours after oral dosing (P<0.0001) but not at 24 to 28 hours after oral dosing (2.9 ng/mL for oral P4 vs 3.2 ng/mL for intravaginal P4 at 2 months, P=0.19). Serum estradiol concentrations were significantly lower after oral P4 than after intravaginal P4 (P<0.05 for all time points). Oral P4 resulted in significantly decreased body weight (-2.5%) compared with intravaginal P4 (+3.6%) (P=0.0001). Markers of breast proliferation, sex steroid receptor expression, and endometrial area did not differ significantly between oral P4 and intravaginal P4 treatments (P>0.1 for all).

CONCLUSIONS

Despite different pharmacodynamic profiles, oral and intravaginal P4 had similar effects on biomarkers in the postmenopausal breast.

Assessing the mammary gland of nonhuman primates: effects of endogenous hormones and exogenous hormonal agents and growth factors

This review provides a summary of the normal biology, development, and morphology of the breast in nonhuman primates (macaques), and of the major published work addressing hormonally-induced changes in the breast of these animals. The mammary glands of macaques are anatomically, developmentally, and physiologically similar to the human breast, with similar expression of sex steroid receptors (estrogen receptors alpha and beta, progesterone receptor A and B, androgen receptors), estrogen dependent markers, and steroid metabolizing enzymes. Genetic similarity between human beings and macaques is high, varying from 95-99% depending on the sequence evaluated. Macaques develop hyperplastic and cancerous lesions of the breast spontaneously, which are similar in type and prevalence to those of human beings. They have a reproductive physiology typical of anthropoid primates, including a distinct menarche and menopause, and a 28-day menstrual cycle. These similarities give unique value to the macaque model for evaluation of the effectiveness and safety of hormonal agents. Such agents considered in this review include estrogens and progestogens, combined therapies such as oral contraceptives and post-menopausal hormone therapies, androgens, selective estrogen receptor modulators, phytoestrogens, prolactin, somatotropin, epidermal growth factor, and other novel agents with hormonal or growth factor-like activity. This review also includes a consideration of selected background changes and typical strategies and markers used for evaluation of experimentally-induced changes, including biopsy-based strategies designed to control for inter-individual variability and minimize numbers of animals used.

Effects of estradiol with micronized progesterone or medroxyprogesterone acetate on risk markers for breast cancer in postmenopausal monkeys

The addition of the synthetic progestin medroxyprogesterone acetate (MPA) to postmenopausal estrogen therapy significantly increases breast cancer risk. Whether this adverse effect is specific to MPA or characteristic of all progestogens is not known. The goal of this study was to compare the effects of oral estradiol (E2) given with either MPA or micronized progesterone (P4) on risk biomarkers for breast cancer in a postmenopausal primate model. For this randomized crossover trial, twenty-six ovariectomized adult female cynomolgus macaques were divided into social groups and rotated randomly through the following treatments (expressed as equivalent doses for women): (1) placebo; (2) E2 (1 mg/day); (3) E2 + P4 (200 mg/day); and (4) E2 + MPA (2.5 mg/day). Hormones were administered orally, and all animals were individually dosed. Treatments lasted two months and were separated by a one-month washout period. The main outcome measure was breast epithelial proliferation, as measured by Ki67 expression. Compared to placebo, E2 + MPA resulted in significantly greater breast proliferation in lobular (P < 0.01) and ductal (P < 0.01) epithelium, while E2 + P4 did not. Intramammary gene expression of the proliferation markers Ki67 and cyclin B1 was also higher after treatment with E2 + MPA (P < 0.01) but not E2 + P4. Both progestogens significantly attenuated E2 effects on body weight, endometrium, and the TFF1 marker of estrogen receptor activity in the breast. These findings suggest that oral micronized progesterone has a more favorable effect on risk biomarkers for postmenopausal breast cancer than medroxyprogesterone acetate.

Effects of two novel selective estrogen receptor modulators, raloxifene, tamoxifen, and ethinyl estradiol on the uterus, vagina and breast in ovariectomized cynomolgus monkeys (Macaca fascicularis)

OBJECTIVE

Assess effects of 2 novel selective estrogen receptor modulators on the reproductive system.

STUDY DESIGN

Adult, ovariectomized, female Macaca fascicularis, n = 3 per group, orally dosed for 12 weeks with vehicle; selective estrogen receptor modulator 393 (2, 4, or 8 mg/kg/day); selective estrogen receptor modulator 379 (4 mg/kg per day); raloxifene (3 mg/kg per day); tamoxifen (1 mg/kg per day); or ethinyl estradiol (3 microg/kg per day). Outcomes included organ weights, histopathology, plasma lipids, and bone biomarkers.

RESULTS

Novel selective estrogen receptor modulators tested did not alter uterine weight or endometrial histology. Tamoxifen and ethinyl estradiol increased uterine weight 2- to 3-fold (P <.05) and endometrial glandular proliferation 5- to 6-fold (P < .05). Adrenal weight was 50% higher in the tamoxifen group. Ethinyl estradiol increased breast lobular epithelial proliferation 6-fold (P < .05). Selective estrogen receptor modulators 393 and ethinyl estradiol decreased bone biomarkers.

CONCLUSION

The results for raloxifene, tamoxifen, and ethinyl estradiol are consistent with previous findings, and results for selective estrogen receptor modulator 393 and selective estrogen receptor modulator 379 indicate potential for tissue selectivity.

Breast response to menopausal hormone therapy--aspects on proliferation, apoptosis and mammographic density

Breast cancer is the major malignancy among women in the Western world. The breast is clearly a target organ for sex steroid hormones and hormonal treatments have been associated with an increased risk of breast cancer. The balance between proliferation and apoptosis is important for breast cell homeostasis. Mammographic breast density has been identified as a strong and independent risk factor for breast cancer. It seems clear that there is a difference between various hormonal treatments with regard to their effects on breast density and cell proliferation. Also, not all women respond similarly to the same treatment. Combined estrogen and progestogen therapy generally will enhance density and proliferation more than treatment with estrogen alone. Certain constitutional and hormonal factors appear to be predictive of breast reactivity. Older women with a low body mass index respond more strongly to treatment. Estrogen levels have a positive and androgens a negative association to increase in density and proliferation. A combination of increased proliferation and decreased apoptosis could be one mechanism to explain the excess risk of breast cancer during combined estrogen/progestogen treatment. Tibolone seems to have less impact on breast response than conventional hormone therapy. Efforts should be made to identify those women with an adverse response to treatment as well as therapeutic principles with the least possible influence on the breast.

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.

The effect of medroxyprogesterone acetate on estrogen-dependent risks and benefits--an attempt to interpret the Women's Health Initiative results

The results of the two arms of the Women's Health Initiative (WHI) study allow a comparative assessment of the contribution of the progestogen component to the changes in risk of cardiovascular disease and cancer during treatment of postmenopausal women with conjugated equine estrogens and medroxyprogesterone acetate (CEE/MPA). However, the high proportion of older and overweight or obese women compromises any conclusions, since we estimate that 50% of the women would have the metabolic syndrome. In overweight postmenopausal women with hyperinsulinemia, the risk of breast cancer is elevated and cannot be increased further by hormone replacement therapy (HRT). Therefore, the non-significant, but consistent reduction in breast cancer risk during treatment with CEE alone might be based on an improvement of hyperinsulinemia. The 24% increase in breast cancer risk in the CEE/MPA group can be regarded as an artifact due to very low numbers of breast cancer diagnoses in the placebo group of women who had received HRT prior to the WHI study. The elevated risk of venous thromboembolism and the transient increase in the risk of coronary heart disease (CHD) during treatment with CEE/MPA but not CEE alone suggests a direct effect of MPA on the vessel wall. MPA has been demonstrated to upregulate the thrombin receptor, the thrombin-induced production of tissue factor and procoagulatory activity in the vessel wall owing to its glucocorticoid activity. In contrast, CEE alone reduced non-significantly the risk of CHD in women aged 50-59 years, suggesting that primary prevention is possible if estrogen replacement therapy is initiated early. As clinical studies on the effect of different progestogens combined with estrogens are scarce, a possible superiority of progestogens other than MPA remains to be proven.

Effects of soy on the mammary glands of premenopausal female monkeys

OBJECTIVE

To evaluate the interactive effects of dietary soy and menstrual cycle phase on breast proliferation, apoptosis, and sex steroid receptor expression in premenopausal female cynomolgus monkeys.

DESIGN

Animals were randomized to receive diets with either casein lactalbumin or soy as the protein source for 12 months. Paired follicular and luteal mammary gland biopsies were taken before and after treatment and evaluated for epithelial proliferation and area, apoptosis, and sex steroid receptor expression.

SETTING

Academic research environment.

ANIMAL(S)

Fifty-two adult female cynomolgus monkeys (Macaca fascicularis).

INTERVENTION(S)

Soy protein with the human equivalent of 129 mg/d of isoflavones.

MAIN OUTCOME MEASURE(S)

Breast proliferation and epithelial area.

RESULT(S)

Follicular and luteal assessments were taken on cycle day (+/- SE) 5.3 +/- 0.1 and 22.0 +/- 0.1, respectively. Serum E2, serum P, breast proliferation, and vaginal maturation were significantly higher in the luteal vs. follicular phase. Soy treatment resulted in significantly higher serum isoflavone concentrations compared with the casein lactalbumin group but did not significantly affect breast proliferation, epithelial area, apoptosis, or progesterone receptor expression; uterine size; or vaginal maturation in either the follicular or luteal phase.

CONCLUSION(S)

Results indicate that dietary levels of soy intake have no detectable hormonal effects on the premenopausal breast.

Effect of 17 beta-estradiol, progesterone, synthetic progestins, tibolone, and tibolone metabolites on vascular endothelial growth factor mRNA in breast cancer cells

OBJECTIVE

To determine the effect of 17beta-estradiol, progesterone, medroxyprogesterone acetate, levonorgestrel, norethindrone, tibolone, and tibolone metabolites on vascular endothelial growth factor (VEGF) isoforms 121 and 165 mRNA in two breast cancer cell lines, MCF-7 (estrogen receptor rich) and T47-D (progesterone receptor rich), in vitro.

DESIGN

Prospective basic research study.

SETTING

Basic research laboratory.

PATIENT(S)

None.

INTERVENTION(S)

MCF-7 and T47-D cells were cultured to 80% confluence in vitro. After 24 hours' incubation in serum-free media, 1.0, 0.1, and 0.01 microM of 17beta-estradiol, tibolone, 3alpha-hydroxytibolone and 3beta-hydroxytibolone were added to MCF-7 cells. Progesterone, medroxyprogesterone acetate, levonorgestrel, norethindrone, and Delta4 tibolone at 1.0, 0.1, and 0.01 microM were added to T47-D cells. The cells plus steroids were incubated for a further 24 hours.

MAIN OUTCOME MEASURE(S)

Isolation and identification of VEGF isoforms 121 and 165 using semiquantitative polymerase chain reaction, gel electrophoresis, with cyclophilin as an internal control.

RESULT(S)

17beta-estradiol, tibolone, 3alpha-hydroxytibolone, and 3beta-hydroxytibolone had no effect on VEGF mRNA in MCF-7 cells. Progesterone, medroxyprogesterone acetate, levonorgestrel, and norethindrone increased VEGF mRNA in T47-D cells. Delta4-Tibolone also increased VEGF mRNA but to a lesser extent than the progestogens.

CONCLUSION(S)

17beta-estradiol, tibolone, and tibolone hydroxy-metabolites had no effect on VEGF mRNA in MCF-7 cells. Progesterone and progestins increased VEGF mRNA in T47-D breast cancer cells, but Delta4-tibolone was less effective than progestogens on this angiogenic gene in the T-47 D cells. This differential effect may be related to breast cancer growth.

Controversies about HRT--lessons from monkey models

Lessons from monkey models contribute significantly to a better understanding of the controversies in reconciling the differences in postmenopausal hormone treatment outcomes between observational and randomized trial data. Monkey studies brought attention to premenopausal estrogen deficiency with resulting premature coronary artery atherosclerosis. Recently, those monkey studies were confirmed for premenopausal women in the NHLBI-sponsored Women's Ischemia Syndrome Evaluation (WISE) Study. Monkey studies have provided convincing evidence for the primary prevention of coronary artery atherosclerosis when estrogens are administered soon after the development of estrogen deficiency. Equally convincing are the data from monkey studies indicating the total loss of these estrogens beneficial effects if treatment is delayed for a period equal to six postmenopausal years for women. An attempt has been made using the monkey model to identify the hormone treatment regimen most effective in preventing the progression of coronary artery atherosclerosis. By a substantial margin, the most effective approach is that of using estrogen containing oral contraceptive during the perimenopausal transition, followed directly by hormone replacement therapy postmenopausally. Because of similarities between human and nonhuman breast, monkeys have had a major role in clarifying controversies surrounding the breast cancer risk of estrogen only versus estrogen plus progestin therapies. The results of monkey studies suggest little or no effects of estrogen only treatment; whereas, estrogen+progestin clearly increases breast cancer risk.

Hormonal environment in the induction of breast cancer in castrated rats using dimethylbenzanthracene: influence of the presence or absence of ovarian activity and of treatment with estradiol, tibolone, and raloxifene

OBJECTIVE

The influence of hormone therapy on the induction or the promotion of breast cancer has yet to be determined. Recent studies establish a cause-effect relation between hormones and cancer, although epidemiological data and studies of tumor behavior give rise to doubts. The aim of the study was to observe and evaluate the influence of different hormonal environments on the induction of breast cancer in a well-established experimental model.

DESIGN

In this experimental animal study, breast cancer was induced by using a single intragastric dose of 20 mg of dimethylbenzanthracene in prepubertal Sprague-Dawley rats randomized into five groups: group 1 (control); group 2 (castrated prepubertal animals); and groups 3, 4, and 5 (castration of prepubertal animals followed by hormonal treatment starting at puberty [11 weeks] with tibolone, raloxifene, and estradiol, respectively). Follicle-stimulating hormone and estradiol levels were measured at 6, 11, 16, and 31 weeks.

RESULTS

Absence of ovarian activity was observed in groups 2, 3, 4, and 5, as well as the expected variations in hormone levels in all groups. Breast cancers were obtained in 100% of the animals in the control group, with an average of four (two to seven) tumors per animal in this group. Only one cancer appeared in groups 2, 3, and 4, and none appeared in group 5.

CONCLUSIONS

In this experimental model and using the hormone treatments chosen, neither the treatments nor the absence of ovarian activity induced breast cancer.

Expression of p53 and markers for apoptosis in breast tissue during long-term hormone therapy in cynomolgus monkeys

OBJECTIVE

The purpose of this study was to analyze the expression of p53 and markers for apoptosis in breast tissue during long-term hormone therapy in cynomolgus monkeys.

STUDY DESIGN

Sixty oophorectomized macaques were randomized to receive tibolone, conjugated equine estrogens (CEE), CEE+medroxyprogesterone acetate (MPA), or no hormonal treatment. Breast tissue was collected at necropsy after 2 years, and stained for p53, p21, and cleaved caspase-3.

RESULTS

Differences were seen between treatment groups. The expression of p53 and caspase-3 was significantly lower in tibolone-treated animals (P<.01). Levels of p53 and caspase-3 were lower in the combined treatment group (CEE+MPA) when compared to both estrogen only and control groups.

CONCLUSION

Alternative regimens for hormonal therapy seem to have different effects on p53 expression and apoptotic activity within the breast. A combined effect of increased proliferation and decreased apoptosis could be one possible mechanism to explain an increased risk for breast cancer.

Breast cancer risk in the WHI study: The problem of obesity

In the climacteric, about 40% of the women have occult breast tumors the growth of which may be stimulated by hormones. Many genetic, reproductive and lifestyle factors may influence the incidence of breast cancer. Epidemiological data suggest that the increase in the relative risk (RR) of breast cancer induced by hormone replacement therapy (HRT) is comparable with that associated with early menarche, late menopause, late first birth, alcohol consumption, etc. One of the most important risk factors is obesity which exceeds the effect of HRT by far, and in overweight postmenopausal women the elevated risk of breast cancer is not further increased by HRT. As in the WHI study the majority of women was overweight or obese, this trial was unsuitable for the investigation of breast cancer risk. In the women treated with an estrogen/progestin combination, the RR of breast cancer rose only in those women who have been treated with hormones prior to the study, suggesting a selection bias. In the women not pretreated with hormones, it was not elevated. In the estrogen-only arm of the WHI study, there was no increase but a steady decrease in the RR of breast cancer during 6.8 years of estrogen therapy. This result was unexpected, as estrogens are known to facilitate the development and growth of breast tumors, and the effect is enhanced by the addition of progestins. Obese women are at high risk to develop a metabolic syndrome including insulin resistance and hyperinsulinemia. In postmenopausal women, elevated insulin levels are not only associated with an increased risk for cardiovascular disease, but also for breast cancer. This might explain the effects observed in both arms of the WHI study: HRT with relative low doses of estrogens may improve insulin resistance and, hence, reduce the elevated breast cancer risk in obese patients, whereas this beneficial estrogen effect may be antagonized by progestins. The principal options for the reduction of breast cancer risk in postmenopausal women are the prevention of overweight and obesity to avoid the development of hyperinsulinemia, the medical treatment of insulin resistance, the use of low doses of estrogens and the reduction of exposure to progestins. The latter might include long-cycles with the sequential use of appropriate progestins every 3 months for 14 days. There are large inter-individual variations in the proliferative response to estrogens of the endometrium. Control by vaginalsonography and progestin challenge tests may help to identify those women who may be candidates for low-dose estrogen-only therapy.

Lessons to be learned from animal studies on hormones and the breast

The relation of hormone use by postmenopausal women to breast cancer risk has been controversial and unclear. A recent large randomized trial, the Women's Health Initiative (WHI) and a large observational study (Million Women Study) provided somewhat conflicting answers. The WHI found an increased incidence of breast cancer among women given hormone therapy (conjugated equine estrogen plus medroxyprogesterone acetate) but no increase in those given estrogen only therapy (conjugated equine estrogen alone). Whereas, the Million Women Study found an increased breast cancer risk among the estrogen plus progestin and the estrogen only users. This review brings comparative perspective to the issue of the effects of estrogen plus progestin versus estrogen only effects on breast cancer and is focused particularly on nonhuman primates. Although data from rodents is mixed, studies of monkeys suggest that estrogen only treatment has little or no effect on breast cell proliferation, and by inference, on breast cancer risk. On the other hand, data from both mouse and monkey studies strongly support the conclusion that the co-administration of a progestogen with an estrogen markedly increases breast cell proliferation and the potential for breast cancer promotion.

Effects of social status and moderate alcohol consumption on mammary gland and endometrium of surgically postmenopausal monkeys

OBJECTIVE

To evaluate the effects of social subordination stress and chronic moderate alcohol consumption on indices of breast and endometrial cancer risk.

DESIGN

Forty-six adult, ovariectomized, cynomolgus monkeys (Macaca fascicularis) were trained to voluntarily drink a placebo or a two-drink/day equivalent of ethanol (0.5 g/kg), 5 days a week for 26 months, the latter resulting in average blood alcohol levels of 42 mg/100 mL. Indices of cell proliferation and sex steroid receptor abundance were measured.

RESULTS

Compared with dominants, socially subordinate females had increased cell proliferation and proportions of glandular (P < 0.02) and epithelial tissue (P = 0.009) and less stroma (P < 0.02) in endometrium, and increased tissue thickness in breast (P < 0.05). There was no evidence of increased risk of breast or endometrial cancer with chronic moderate alcohol consumption, as indicated by markers of cell proliferation and sex steroid receptor abundance. Chronic moderate alcohol consumption did not effect circulating sex steroid concentrations (all P > 0.10). The adipocyte hormones leptin and adiponectin were correlated with indices of cell proliferation and sex steroid receptor abundance.

CONCLUSIONS

These observations suggest that social status was more important than chronic moderate alcohol consumption in endometrial and breast biology of surgically postmenopausal females. Endogenous sex steroid metabolism was not significantly affected by chronic moderate alcohol exposure consistent with the lack of estrogen-like effects on breast and endometrium. Social subordination stress was associated with initial cellular changes that may increase endometrial cancer risk. Ovariectomized cynomolgus monkeys may be a useful model for the study of effects of social factors and obesity on breast and endometrial cancer risk.

Tissue-selective effects of tibolone on the breast

Hormone treatment with an estrogen plus a progestagen (EPT) increases the risk of breast cancer. Both hormone activities are also induced by tibolone. In order to assess the breast safety of tibolone, it was evaluated in several pre-clinical models. The effects were inconclusive in breast cancer cell lines but, in various in vivo models, it did not stimulate the breast. In the 17,12-dimethylbenz(a)anthracene (DMBA) model, tibolone clearly inhibited the growth of breast tumors and, when given prophylactally, far less tumors developed. Ovariectomized monkeys showed no increase in the expression of the proliferation marker Ki67. The effects of tibolone and its metabolites on the steroid metabolizing enzymes in breast tissues were investigated in order to unravel its mode of action in the breast. Tibolone and its metabolites did not inhibit aromatase, but sulfatase was profoundly inhibited. The sulfated 3alpha-OH tibolone metabolite even showed irreversible inhibition of sulfatase. In addition, 17ss-hydroxysteroid dehydrogenase activities were slightly inhibited and sulfotransferase activity was stimulated at low concentrations. The consequence of these effects is that, for both endogenous estrogens and estrogenic-metabolites of tibolone, the equilibrium is preferential for the sulfated forms. The intracellular hormonal milieu tibolone and its metabolites also influence cellular homeostasis. It inhibits cell proliferation of normal breast epithelial cells and stimulates apoptosis. In this respect, tibolone behaves differently from estrogens. Clinical studies have shown that tibolone users experience less breast tenderness and do not show an increase in mammographic density as found with continuous combined EPT. The data concerning tibolone and breast cancer risk are inconclusive and require further investigation.

Multisystem evaluations of the long-term effects of tibolone on postmenopausal monkeys

This long-term study (2 years) was designed to compare the effects of tibolone (LoTib at 0.05 mg/kg and HiTib at 0.2 mg/kg) with those of conjugated equine oestrogens (CEE) alone (0.042 mg/kg) and CEE continuously combined with medroxyprogesterone acetate (MPA) (0.167 mg/kg) on coronary artery atherosclerosis, bone, mammary gland and uterus in ovariectomised cynomolgus monkeys fed a moderately atherogenic diet. Despite reductions in plasma concentrations of high density lipoprotein cholesterol in tibolone-treated monkeys, there was no exacerbation of coronary artery atherosclerosis. Tibolone was equivalent to, or slightly better than, CEE and CEE + MPA in protecting against postmenopausal bone loss and loss of bone strength. Tibolone also resulted in less stimulation of breast and endometrial tissue compared with CEE and CEE + MPA. In conclusion, the results suggest that tibolone is a cardiovascular-safe treatment that is effective for the prevention of osteoporosis and that may have advantages over CEE or CEE + MPA with regard to endometrial and breast safety.

Effect of tibolone on markers of cardiovascular disease risk in postmenopausal women undergoing hemodialysis: a pilot study

OBJECTIVE

To assess the effect of tibolone on markers of vascular risk in postmenopausal women who were receiving hemodialysis.

DESIGN

One-year open-label study.

SETTING

"Zvezdara" University Medical Center, Belgrade, Serbia.

PATIENT(S)

Twenty-eight postmenopausal women undergoing chronic hemodialysis.

INTERVENTION(S)

Fifteen women received tibolone 2.5 mg three times per week; 13 other women served as controls.

MAIN OUTCOME MEASURE(S)

Mean arterial pressure and weight were measured at baseline and at 6 and 12 months, and blood was collected for insulin, total cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, lipoprotein(a), high-sensitivity C-reactive protein (hs-CRP), endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and markers of renal function.

RESULT(S)

Mean arterial pressure fell in the tibolone but not in the control group at 6 and 12 months versus baseline (mean [SD]: 93 [15] vs. 105 [11] mmHg and 94 [10] vs. 105 [11] mmHg, respectively). Weight, insulin, lipids, lipoprotein(a), hs-CRP, ET-1, VEGF, and renal function remained unchanged within each group, but high-density lipoprotein concentrations fell in the tibolone group after 12 months (1.2 [0.3] vs. 1.6 [0.6] mmol/L).

CONCLUSION(S)

The effects of tibolone on markers of vascular risk in postmenopausal women who are receiving hemodialysis and healthy women appear to differ. This should be taken into account when tailoring menopausal therapies to the specific requirements of each individual.

Cervical and vaginal epithelial neoplasms in cynomolgus monkeys

Papillomavirus-associated cervical cancer is the second most common neoplasm in women but has rarely been reported in animals. This report describes cervical and vaginal intraepithelial neoplasms identified in routine histologic specimens obtained from 20 (5.2%) of 385 female cynomolgus macaques (Macaca fascicularis) being used in long-term studies. Lesion incidence was similar in both control and hormonally treated animals (4.7% and 5.5%, respectively). Neoplasms included benign vaginal papillomas, mild to severe intraepithelial dysplasias, and two invasive cervical carcinomas. Common morphologic features included koilocytosis, nuclear atypia, and expansion of the basal epithelium. Selective staining of lesions with at least one of three papillomavirus antibodies was observed in all cases (20 of 20). In contrast, immunostaining of lesions was negative for Epstein-Barr-related virus proteins (0 of 20). The unique similarities between the observed lesions and those seen in women suggest that macaques may provide a suitable animal model for study of papillomavirus oncogenesis.

MPA and postmenopausal coronary artery atherosclerosis revisited

Whether progestins, particularly medroxyprogesterone acetate (MPA), attenuate the cardiovascular benefits of postmenopausal estrogen replacement therapy (ERT) has been controversial for over a decade. Concerns related first to findings that MPA attenuated increases of high density lipoprotein cholesterol (HDLC) concentrations of postmenopausal women compared to conjugated equine estrogen (CEE) alone. That observation was followed by early cynomolgus monkey studies that suggested MPA decreased estrogen's cardiovascular benefits (vascular reactivity and coronary artery atherosclerosis inhibition). In a more recent and larger trial with cynomolgus monkeys, no differences were seen in the coronary artery atherosclerosis protective effect of CEE when MPA was co-administered (HRT). The lack of attenuation of ERTs benefits by progestins has also been seen in at least three studies of carotid artery intima-media thickness (IMT) of postmenopausal women. Additionally, the majority of studies of vascular reactivity of postmenopausal women have not found differences when CEE is given alone or with MPA. Seven observational studies of cardiovascular outcomes of postmenopausal women permit separate consideration of ERT versus HRT use; there is no evidence of attenuation of ERTs benefits by progestin use. In conclusion, it is evident that the current experimental, clinical, and observational data do not provide evidence that progestins attenuate estrogen's cardiovascular benefits.