Expression of sex steroid receptors and IGF-1 mRNA in breast tissue--effects of hormonal treatment

Effects of Estradiol/Micronized Progesterone vs. Conjugated Equine Estrogens/Medroxyprogesterone Acetate on Breast Cancer Gene Expression in Healthy Postmenopausal Women

Recent studies suggest estradiol (E₂)/natural progesterone (P) confers less breast cancer risk compared with conjugated equine estrogens (CEE)/synthetic progestogens. We investigate if differences in the regulation of breast cancer-related gene expression could provide some explanation. This study is a subset of a monocentric, 2-way, open observer-blinded, phase 4 randomized controlled trial on healthy postmenopausal women with climacteric symptoms (ClinicalTrials.gov; EUCTR-2005/001016-51). Study medication was two 28-day cycles of sequential hormone treatment with oral 0.625 mg CEE and 5 mg of oral medroxyprogesterone acetate (MPA) or 1.5 mg E₂ as percutaneous gel/day with the addition of 200 mg oral micronized P. MPA and P were added days 15-28/cycle. Material from two core-needle breast biopsies in 15 women in each group was subject to quantitative PCR (Q-PCR). The primary endpoint was a change in breast carcinoma development gene expression. In the first eight consecutive women, RNA was extracted at baseline and after two months of treatment and subjected to microarray for 28856 genes and Ingenuity Pathways Analysis (IPA) to identify risk factor genes. Microarray analysis showed 3272 genes regulated with a fold-change of >±1.4. IPA showed 225 genes belonging to mammary-tumor development function: 198 for CEE/MPA vs. 34 for E₂/P. Sixteen genes involved in mammary tumor inclination were subject to Q-PCR, inclining the CEE/MPA group towards an increased risk for breast carcinoma compared to the E₂/P group at a very high significance level (p = 3.1 × 10^-8, z-score 1.94). The combination of E₂/P affected breast cancer-related genes much less than CEE/MPA.

Estrone - a partial estradiol antagonist in the normal breast

Oral hormone replacement therapy (HRT) based on estradiol-17β (E2) greatly increases circulating estrone (E1) levels. E1 is an estrogen receptor agonist but may also be a partial E2 antagonist. We investigated the effects of circulating E1 on the association between circulating E2 and the increase in mammographic density (∂MD) in 46 healthy post-menopausal women treated with E2 2 mg and norethisterone acetate 1 mg daily. MD and serum E1 and E2 were measured before and after 6 months of treatment. At high E1 levels, ∂MD showed significant positive correlations leading to increase (∂-values) in both E1 and E2. Lowering the upper serum E1 limit strengthened the correlations to ∂E2 while the significant correlations to ∂E1 disappeared. E1 at high concentrations may act as a partial E2 antagonist also in the normal breast in vivo and disturb relationships between circulating E2 and biological estrogen effects. When investigating the relations between circulating steroids and their effects, structurally related compounds, which may act as partial antagonists, have to be considered, at least when they are present in higher concentrations.

Percutaneous estradiol/oral micronized progesterone has less-adverse effects and different gene regulations than oral conjugated equine estrogens/medroxyprogesterone acetate in the breasts of healthy women in vivo

Gene expression analysis of healthy postmenopausal women in a prospective clinical study indicated that genes encoding for epithelial proliferation markers Ki-67 and progesterone receptor B mRNA are differentially expressed in women using hormone therapy (HT) with natural versus synthetic estrogens. Two 28-day cycles of daily estradiol (E2) gel 1.5 mg and oral micronized progesterone (P) 200 mg/day for the last 14 days of each cycle did not significantly increase breast epithelial proliferation (Ki-67 MIB-1 positive cells) at the cell level nor at the mRNA level (MKI-67 gene). A borderline significant beneficial reduction in anti-apoptotic protein bcl-2, favouring apoptosis, was also seen followed by a slight numeric decrease of its mRNA. By contrast, two 28-day cycles of daily oral conjugated equine estrogens (CEE) 0.625 mg and oral medroxyprogesterone acetate (MPA) 5 mg for the last 14 days of each cycle significantly increased proliferation at both the cell level and at the mRNA level, and significantly enhanced mammographic breast density, an important risk factor for breast cancer. In addition, CEE/MPA affected around 2,500 genes compared with just 600 affected by E2/P. These results suggest that HT with natural estrogens affects a much smaller number of genes and has less-adverse effects on the normal breast in vivo than conventional, synthetic therapy.

Lowering oral contraceptive norethindrone dose increases estrogen and progesterone receptor levels with no reduction in proliferation of breast epithelium: a randomized trial

BACKGROUND

This study was conducted to compare breast epithelial-cell proliferation and estrogen and progesterone receptor levels in women taking one of two oral contraceptives (OCs) containing the same dose of estrogen but different doses of the progestin norethindrone (NET).

STUDY DESIGN

Thirty-three women were randomly assigned 1:1 to one of two OCs with 35-mcg ethinylestradiol (EE2) but different doses of NET - 1 or 0.4 mg. At the end of the active pill phase of the third OC cycle, a breast biopsy was performed and the percentages of epithelial cells of the terminal duct lobular units were measured for Ki67 (MIB1), progesterone receptors A and B (PRA and PRB, respectively), and estrogen receptor α (ERα).

RESULTS

The biopsies from 27 women had sufficient epithelium for analysis. The percentages of cells positive for PRA, PRB and ERα were approximately double with the lower progestin dose (PRA: p=.041; PRB: p=.030; ERα: p=.056). The Ki67 percentage was not reduced with the lower progestin dose (12.5% for 0.4-mg NET vs. 7.8% for 1.0-mg NET).

CONCLUSIONS

The increase in PRA-, PRB- and ERα-positive cells with the 60% lower progestin dose OC appears likely to account for its failure to decrease breast-cell proliferation. This breast-cell proliferation result is contrary to that predicted from the results of lowering the medroxyprogesterone acetate dose in menopausal hormone therapy.

Mechanisms for differential effects between natural progesterone and synthetic progestogens on normal breast tissue

Both epidemiological studies and experimental data on normal breast tissue suggest increased cancer risk, proliferation and mammographic breast density (MD) during hormone therapy (HT) containing synthetic progestogens in traditional doses, and the relative risk or RR is approximately 1.5–3 (for women treated vs. untreated with the above therapies), proliferation levels of normal breast epithelial cells of around 10% and increase in MD in up to around 50% of women during treatment. Dose-response relationships have been inferred by correlations between progestogens as levonorgestrel, norethisterone acetate and medroxyprogesterone acetate on the one hand and proliferation and/or MD on the other hand, and of indications of lower relative risk of breast cancer with modern low or ultra-low dose HT. In contrast, natural progesterone endogenously during the menstrual cycle has a weak effect and exogenous estrogen in combination with oral micronized progesterone in HT has shown to yield an indifferent effect on proliferation. Furthermore, in epidemiological studies such as the French E3N cohort, these combinations have not shown any risk increase for breast cancer for at least 5 years of treatment. Experimental data supporting or not supporting the view that the main proliferative mechanism for natural progesterone is through binding to its nascent progesterone receptors is discussed as well as the pros and cons that the non-physiological higher proliferation levels induced by synthetic progestogens is mainly mediated through interaction with potent growth factors and their paracrine and/or cell signaling pathways.

Effects of pre- and postmenopausal use of exogenous hormones on receptor content in normal human breast tissue: a randomized study

OBJECTIVE

To examine the effects of exposure to endogenous and exogenous hormones on estrogen receptor-alpha (ERalpha) and progesterone receptor (PR) levels in normal human breast tissue.

METHODS

In a randomized study of women scheduled for mammary reduction plasty (n = 81), ERalpha and PR content in breast parenchyma was analyzed in premenopausal (n = 49) and postmenopausal (n = 16) women. Premenopausal women were randomized to surgery in the follicular or luteal phase of the menstrual cycle or after oral contraceptive treatment for 2 months. Postmenopausal women were randomized to sequential or estrogen-only therapy for 2 months prior to surgery.

RESULTS

ERalpha content was higher in parous than in nulliparous (p = 0.009) premenopausal women and displayed a positive association with age (r(s) = 0.51, p = 0.0002). Compared with premenopausal women in the follicular phase, postmenopausal women had higher ERalpha content (p = 0.040) whereas premenopausal women on oral contraception had lower ERalpha (p = 0.048) and PR (p = 0.007) content. Smokers had lower PR content than non-smokers (p = 0.02).

CONCLUSION

In the present study ERalpha content was higher in parous than in non-parous women and associated with premenopausal age. Short-term oral contraceptives yielded lower ERalpha and PR contents. Postmenopausal estrogen/progestogen combined therapy yielded lower PR content than estrogen-only therapy.

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.

Role of progestins with partial antiandrogenic effects

An experts' meeting on the 'Role of progestins with partial antiandrogenic effects' was held in Berlin from January 19 to 22, 2001. The meeting was chaired by Dr R. Sitruk-Ware (New York, USA) and participants included Ms F. Fruzzetti (Pisa, Italy), J. Hanker (Trier, Germany), J. Huber (Vienna, Austria), F. Husmann (Bad Sassendorf, Germany), S. O. Skouby (Copenhagen, Denmark), J. H. H. Thijssen (Utrecht, The Netherlands), and R. Druckmann (Nice, France). The present paper reports the conclusions of the meeting. However, the publication of the Women's Health Initiative study, which appeared after the meeting, led to additional comments and revisions.

Expression of estrogen receptors (alpha, beta) and insulin-like growth factor-I in breast tissue from surgically postmenopausal cynomolgus macaques after long-term treatment with HRT and tamoxifen

The novel estrogen receptor ERbeta could be a key factor for proliferation and breast cancer risk. In a primate model for long-term HRT, surgically postmenopausal cynomolgus macaques were treated for 35 months with conjugated equine estrogens (CEE), medroxyprogesterone acetate (MPA), CEE+MPA and tamoxifen (n=5 in all groups). The immunohistochemical expression of ERalpha, ERbeta and IGF-I in breast tissue was quantified by image analysis. Overall the levels of ERbeta were higher than for ERalpha. In untreated animals, the median area of positive cells was 58% and 21%. The lowest levels for ERbeta were seen during treatment with CEE/MPA (3%) and in this group the expression of ERbeta was lower than for ERalpha. Tamoxifen had effects similar to estrogen. ERbeta may have a role to modulate the proliferative response following activation of ERalpha. The results suggest that hormonal treatments have a different influence on the balance ERbeta/ERalpha in breast tissue.

Hot flashes in breast cancer survivors

Hot flashes can be a major problem for patients with a history of breast cancer. The precipitation of menopause in premenopausal women who undergo chemotherapy for breast cancer can lead to the rapid onset of hot flash symptoms that are more frequent and more severe than those associated with natural menopause. In addition, tamoxifen, historically the most commonly prescribed pharmacologic agent for the treatment of breast cancer, is associated with hot flashes in more than 50% of its users. Although estrogen relieves hot flashes in 80-90% of women who initiate treatment, its use in women with a history of breast cancer is controversial, and most physicians in the community will not use this treatment modality. In addition, the results of the long-awaited Women's Health Initiative study and other recent studies suggest that long-term estrogen therapy should not be recommended for most women for a variety of reasons. However, hot flashes in breast cancer survivors should no longer be considered untreatable, as there are many pharmacologic and nonpharmacologic treatments that can help alleviate this problem. This article reviews the current strategies for the management of hot flashes in breast cancer survivors and the evidence supporting their use.

Effects of long-term HRT and tamoxifen on the expression of progesterone receptors A and B in breast tissue from surgically postmenopausal cynomolgus macaques

Estrogen is a well-known mitogen in breast epithelium but the role of progesterone is complex and incompletely understood. In contrast to what is seen in the endometrium, combined estrogen/progestogen treatment for postmenopausal replacement (HRT) may carry a risk for breast cancer beyond that of estrogen alone. The ratio of the two progesterone receptor (PR) isoforms, PRA/PRB may define the response to progesterone in reproductive tissues. In a primate model for long-term HRT, surgically, postmenopausal cynomolgus macaques were treated for 35 months with conjugated equine estrogens (CEE), medroxyprogesterone acetate (MPA), CEE + MPA and tamoxifen (n = 5 in all groups). The immunohistochemical expression of PRA, PRB and the androgen receptor (AR) in breast tissue was quantified by image analysis. Over all, the total PR immunostaining in glandular epithelium was more abundant during CEE (mean 12%) and tamoxifen ( 1%) treatment as compared to CEE/MPA (5%), MPA (4%) and untreated controls (6%). Differences in PRB expression were observed between treatment groups (p < 0.05). In the CEE group levels of PRA were unchanged while there was a decline in the CEE/MPA group. The mean PRA/PRB ratio in the CEE group was 2.7 and in the CEE/MPA group 0.2. Treatment with tamoxifen had effects similar to those of estrogen. There was in all groups a weak positive nuclear AR immunostaining. This is the first in vivo study on the effects on long-term hormonal treatment on the expression of PR isoforms in normal primate breast tissue. The results suggest that hormonal treatments have a different influence on the PRA/PRB balance in the breast.

Effects of synthetic progestagens on the mRNA expression of androgen receptor, progesterone receptor, oestrogen receptor alpha and beta, insulin-like growth factor-1 (IGF-1) and IGF-1 receptor in heifer tissues

Synthetic progestagens like melengestrol acetate (MGA) are widely used for oestrus synchronization and for growth promotion in cattle production. The metabolic effects exceed its primary potency as a progestagen. It is speculated that MGA stimulates follicle development and thereby endogenous oestrogen production, but inhibits ovulation. To investigate the dose-dependent effects on mRNA expression levels, six heifers were fed for 8 weeks with different levels of MGA (0.5, 1.5, 5 mg) daily and two heifers served as controls. The expression of steroid receptor mRNA [androgen receptor (AR), progesterone receptor (PR), oestrogen receptor (ER) ERalpha and ERbeta], insulin-like growth factor-1 (IGF-1) and its receptor were quantified in liver, neck (m. splenius) and shoulder muscularity (m. deltoideus). Plasma concentrations of IGF-1 were quantified by radioimmunoassay. In treated animals the MGA plasma levels were elevated over the complete treatment period, corresponding to the MGA treatment concentrations. IGF-1 concentrations of control animals were at constant levels. Plasma levels for oestradiol (E2) and IGF-1 were increased in the low MGA treatment group. Overdosed MGA decreased progesterone (P4) and E2 levels. To quantify the IGF-1 and all receptor mRNA transcripts, sensitive and reliable real-time reverse transcription-polymerase chain reaction (RT-PCR) quantification methods were developed and validated in the LightCycler. A dose-dependent relationship between increasing MGA concentration and mRNA expression was observed in liver for AR and IGF-1 receptor, and in neck muscularity for IGF-1. ERalpha in liver and neck muscle showed a trend of increasing expression.

Management of hot flashes in breast-cancer survivors

Hot flashes can be a major problem for patients with a history of breast cancer. Although oestrogen can alleviate hot flashes to a large extent in most patients, there has been debate about the safety of oestrogen use in survivors of breast cancer. The decrease in hot flashes achieved with progestational agents is similar to that seen with oestrogen therapy but, again, there is some debate about the safety of progestational agents in patients with a history of breast cancer. Several alternative substances have therefore been investigated. These include a belladonna alkaloid preparation, clonidine, soy phyto-oestrogens, vitamin E, gabapentin, and several of the newer antidepressants, with venlafaxine being the best studied to date. Several studies in progress may provide better non-hormonal means of treating hot flashes in the future.

Genetic factors related to racial variation in plasma levels of insulin-like growth factor-1: implications for premenopausal breast cancer risk

The oral contraceptive pill is associated with a modest increase in the risk of early-onset breast cancer in the general population, but it is possible that the risk is higher in certain subgroups of women. The relative risk of breast cancer associated with oral contraceptive use has been reported to be higher for African-American women than for white women. African-American women also have a higher incidence of premenopausal breast cancer than white women. Circulating levels of insulin-like growth factor-1 (IGF-I) vary between ethnic groups and are positively associated with the risk of premenopausal breast cancer. In general, the plasma level of IGF-I is lower in women who take oral contraceptives than in women who do not. In an attempt to explain the observed ethnic difference in IGF-I levels with oral contraceptive use, we sought to identify polymorphic variants of genes that are associated with IGF-I levels and estrogen metabolism. We measured IGF-I and IGFBP-3 plasma levels in 503 nulligravid women between the ages of 17 and 35. All women filled out a questionnaire that included information about ethnic background and oral contraceptive use. Samples of DNA were used to genotype the women for known polymorphic variants in the IGF1, AIB1, and CYP3A4 genes. Black women had significantly higher mean IGF-I levels than white women (330 ng/ml versus 284 ng/ml; P = 0.001, adjusted for age and oral contraceptive use). IGF-I levels were significantly suppressed by oral contraceptives in white women (301 ng/ml versus 267 ng/ml; P = 0.0003), but not in black women. Among oral contraceptive users, the IGF-I level was positively associated with the absence of the IGF1 19-repeat allele (338 ng/ml versus 265 ng/ml; P = 0.00007), with the presence of the CYP3A4 variant allele (320 ng/ml versus 269 ng/ml; P = 0.01), and with the presence of the AIB1 26-repeat allele (291 ng/ml versus 271; P = 0.08). After adjusting for genotypes, ethnic group was no longer a significant predictor of the IGF-I level. IGF-I levels are higher among black than white women. Polymorphic variants in the CYP3A4, IGF1, and AIB1 genes are associated with increases in the plasma levels of IGF-I among oral contraceptive users and the variant alleles are much more common in black women than in white women. The high incidence of premenopausal breast cancer among black women may be mediated through genetic modifiers of circulating levels of IGF-I.

Primate mammary gland insulin-like growth factor system: cellular localization and regulation by sex steroids

BACKGROUND

Insulin-like growth factor 1 (IGF1) plays a critical role in estrogen-induced uterine proliferation, but it is unclear whether this estromedin function occurs in other estrogen-sensitive tissues such as the mammary gland. To elucidate this possibility, we investigated the cellular localization and hormonal regulation of mRNAs for IGF1 and 2, their cognate receptors (IGF1R, IGF2R), and IGF binding proteins 2-5 (BPs 2-5) in the rhesus monkey mammary gland.

METHODS

Ovariectomized monkeys were treated with placebo, estradiol (E2), and E2 plus progesterone (E2/P4) for 3 days, after which mammary tissue was harvested for in situ hybridization and immunohistochemical analyses.

RESULTS

IGF1 and IGF2 mRNA levels were significantly increased and BP2 mRNA decreased by E2 and by E2/P4 treatment. IGF1R mRNA was increased by combined E2/P treatment but not by E2 alone. BP5 mRNA was decreased by E2/P4. No differences in IGF2R, BP3, and BP4 mRNA levels were detected in any treatment group. Mammary IGF1 and IGF2 mRNA levels were both positively correlated with local epithelial proliferation, assessed by immunodetection of the proliferation-specific antigen, Ki67.IGF1 and IGF1R expression were negatively correlated with local programmed cell death, as assessed by the in situ TUNEL method. In contrast, BP2 expression was negatively correlated with epithelial proliferation and positively correlated with programmed cell death. IGF2R, BP3, BP4, and BP5 levels were not significantly correlated with either proliferation or death.

CONCLUSIONS

Thus, E2-induced proliferation is associated with upregulation of both IGF1 and IGF2 expression and downregulation of BP2 expression. These data suggest that the local mammary IGF system is involved in sex steroid-induced mammary epithelial cell hyperplasia.