A comparative study of breast cell proliferation during hormone replacement therapy: effects of tibolon and continuous combined estrogen-progestogen treatment

OBJECTIVE

To use the fine-needle aspiration (FNA) biopsy technique to compare the effects of tibolone, conventional hormone replacement therapy (HRT) and placebo on breast cell proliferation in postmenopausal women.

METHODS

A total of 91 women were randomized to receive either estradiol 2 mg plus norethisterone acetate 1 mg (E2/NETA), tibolone 2.5 mg or placebo for 6 months in a prospective double-blind trial. Breast cell proliferation was assessed using the Ki-67/MIB-1 monoclonal antibody.

RESULTS

From the 83 women who completed the study, a total of 166 FNA biopsies were obtained, and 118 of these aspirates (71%) were evaluable for MIB-1 content. Women with assessable biopsies were younger, had a lower body mass index, and had higher levels of sex hormone binding globulin and insulin-like growth factor-I than women in whom the cell yield was insufficient. During treatment with E2/NETA, there was an increase in proliferation (percentage of MIB-1) from a mean value of 2.2 to 6.4% after 6 months (p < 0.01). No significant changes were recorded during treatment with tibolone or placebo. There was a negative association between proliferation and serum levels of total (r(s) = -0.29, p < 0.05) and free (rs = -0.31, p < 0.03) testosterone.

CONCLUSIONS

Tibolone seems to have little influence on breast cell proliferation.

Breast cell proliferation in postmenopausal women during HRT evaluated through fine needle aspiration cytology

The basis of breast cancer risk associated with hormonal therapies may lie in the regulation of cell proliferation. In a prospective, double-blind, randomized study postmenopausal women were given continuous combined hormone replacement therapy (HRT) either as estradiol valerate 2 mg/dienogest 2 mg, (E2V/DNG) or estradiol 2 mg/noretisterone acetate 1 mg (E2/NETA) for 6 months. Fine needle aspiration (FNA) biopsies were used for immunocytochemical analysis of breast cell proliferation before and during treatment. From 45 women completing the study 135 biopsies were obtained. In the total material there was a more than 4-fold increase in proliferation between baseline and 3 months (p < 0.001). The mean percentage of MIB-1 positive breast cells increased from 2.2 to 9.1%. In some individual women values were as high as 25%. No further increase was recorded at 6 months. While numerical values were somewhat lower in the E2V/DNG group, there were no significant differences between treatments. There was a positive correlation between breast cell proliferation (MIB-1%) and circulating levels of both estradiol (r(s) = 0.54, p < 0.01) and estrone (r(s) = 0.53, p < 0.01) after 3 and 6 months of treatment. No correlations with other endogenous hormones, proteins or with the two exogenous progestogens dienogest and norethisterone were observed. Increased breast cell proliferation should probably be regarded as an unwanted side-effect during HRT. Means to identify those women with the most pronounced proliferative response should be developed. The FNA biopsy technique may be a useful tool to monitor and evaluate the proliferative response to HRT in the normal breasts of postmenopausal women.

Mammographic breast density during hormone replacement therapy: effects of continuous combination, unopposed transdermal and low-potency estrogen regimens

OBJECTIVE

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

STUDY DESIGN

Mammographic density was recorded in women participating in a population-based screening program. At first mammogram, all women were non-users of HRT, and thereafter reported continuous use of the same HRT regimen. The study population comprised 158 women: a total of 52 women were using continuous combined HRT (conjugated equine estrogen 0.625 mg plus medroxyprogesterone acetate 5 mg); 51 women were using low-dose oral estrogen alone (estriol 2 mg daily); and 55 women were using unopposed transdermal estrogen given as a patch (estradiol 50 micrograms/24 h). Films were coded and analyzed for mammographic density by an independent radiologist blinded to treatments. Mammographic density was classified according to Wolfe.

RESULTS

An increase in mammographic density was much more common among women taking continuous combined HRT (40%) than for those using oral low-dose estrogen (6%) and transdermal (2%) treatment. The increase in density was already apparent at the first visit after starting HRT. During long-term follow-up, there was very little change in mammographic status.

CONCLUSION

HRT regimens were shown to have different effects on the normal breast. There is an urgent need to clarify the biological nature and significance of a change in mammographic density during treatment and, in particular, its relation to symptoms and breast cancer risk.

Breast epithelial proliferation in postmenopausal women evaluated through fine-needle-aspiration cytology

OBJECTIVE

The aim was to evaluate fine-needle-aspiration (FNA) cytology as a method of following breast epithelial proliferation in postmenopausal women during hormone replacement therapy (HRT).

METHODS

Twelve healthy postmenopausal women were recruited and randomized to two different types of sequential HRT during 4 months of treatment. The women were administered continuous estradiol 50 micrograms/24 h with the addition of progestogen sequentially in the form of either vaginal progesterone gel 8 mg every 2nd day or medroxyprogesterone acetate 5 mg/day orally during 12 days per month for the complete treatment period. Fine-needle-aspiration biopsies were performed twice during the estrogen phases and twice during the estrogen plus progestogen phases of treatment. Breast epithelial proliferation was analyzed in these samples by immunocytochemistry to measure the content of the nuclear antigen Ki-67/MIB-1, which is expressed in proliferating cells.

RESULTS

From the 12 women, a total number of 47 FNA biopsies were taken. Thirty-eight of these aspirates, 19 from each of the estrogen and the estrogen plus progestogen phases, were evaluable for MIB-1 content (81%). There was a non-significant increase in levels of proliferation during the combined estrogen-progestogen phase (2.1%) compared with the estrogen-only phase (1.4%). These values were similar to those previously observed during the menstrual cycle in young fertile women.

CONCLUSIONS

We conclude that the FNA biopsy technique is feasible for studying proliferation not only in young, normally cycling women but also in the postmenopausal breast.

Effects of oral contraceptives on breast epithelial proliferation

The association between oral contraceptive (OC) use and breast cancer is not fully understood. Estrogen is a known mitogen to breast epithelial cells, but there is still a controversy about the effect of added progestogens. Fine needle aspiration (FNA) biopsies were used to assess epithelial proliferation in normal breast tissue from 106 healthy premenopausal women with and without oral contraceptives. In 26 women biopsies were performed before and after 2 months of OC use. Proliferation, expressed as percentage of Ki-67/MIB-1 positive cells, was correlated to endogenous progesterone, androgenic/anabolic compounds and exogenous progestogen. We found a higher proliferation (p = 0.03) in OC users compared to non users, with mean values of 4.8% and 2.2%, respectively. There was a positive correlation between proliferation and progesterone levels in non-users and with serum levonorgestrel concentrations in women using OCs containing this progestogen (rs = 0.43, p = 0.02). Women using OCs had significantly lower serum androgen levels compared to naturally cycling women and free testosterone levels displayed an inverse relation to breast epithelial proliferation. There was a marked variation in the response to exogenous sex steroids. In certain women after 2 months of OC use, the percentage of MIB-1 positive cells was as high as 40-50%. The results add to the growing evidence that progestogens may be mitogenic in breast tissue. Increased proliferation during hormonal contraception should be regarded as an unwanted and potentially hazardous side effect. Efforts should be made to define hormonal contraceptive regimens which minimize breast epithelial proliferation and to identify those women with the most pronounced proliferative response.

Assessment of hormonally active agents in the reproductive tract of female nonhuman primates

Using the ovariectomized macaque model of postmenopausal women's health, we investigated the effects of long-term treatments (5 weeks-3 years) with estradiol, conjugated equine estrogens (CEE), esterified estrogens, progestins such as medroxyprogesterone acetate (MPA) and nomegestrol acetate, CEE + MPA, tamoxifen, soybean phytoestrogens (SPEs), a variety of putative selective estrogen receptor modulators (SERMs), and androgens. Agents tested were selected on the basis of beneficial effects on arteries and/or bone. Doses were scaled on a caloric or serum-concentration basis to approximate human clinical doses. We evaluated endometrial and mammary gland histopathology and morphometry and used immunohistochemistry to evaluate cell proliferation and expression of estrogen receptor alpha and progesterone receptor (PR). Both estradiol and CEE induced endometrial hyperplasia. MPA antagonized epithelial proliferation induced by CEE in endometrium and induced pseudodecidual stromal hyperplasia in some animals. Tamoxifen induced endometrial polyps, cystic hyperplasia, stromal fibrosis, and PR expression but not Ki-67 expression. SPEs were not estrogenic at dietary doses and antagonized estrogen-induced proliferation in the endometrium and breast. Nandrolone induced mucometra and an adenomyosis-like change. The potential SERM 17 alpha dihydroequilenin did not have uterotrophic or mammotrophic effects. In general, experimental findings in macaques have been predictive of outcomes in human clinical trials of the same agents.

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

The mechanisms behind increased breast tissue proliferation and a possibly increased breast cancer risk in women using hormonal contraception (HC) and hormonal replacement therapy (HRT) are incompletely understood. We analyzed breast tissue from 20 premenopausal and seven postmenopausal women undergoing reduction mammoplasties for estrogen receptor (ER) and progesterone receptor (PR) content as well as mRNA levels for ER, PR and insulin-like growth factor-1 (IGF-1). The receptor values were correlated to IGF-1 mRNA concentrations and levels of steroid and peptide hormones and SHBG. In women using HC, we found significantly lower ER values (p = 0.02) but non-significantly lower ER mRNA levels compared to those in naturally cycling women. PR and PR mRNA were no different. Women on HC displayed a higher breast tissue proliferation (p = 0.05) expressed as Ki-67, MIB-1 positivity, which was correlated with IGF-1 mRNA (r(s) = 0.82, p = 0.04). Since the concentration of sex steroid receptors in breast tissue is comparatively low and steroid receptors are down-regulated during hormonal treatment, mechanisms other than direct sex steroid receptor action are likely to be present. Our results suggest a role for IGF-1 in the proliferative response of breast tissue during exogenous hormonal treatment.

17Beta-hydroxysteroid dehydrogenases in normal human mammary epithelial cells and breast tissue

17Beta-hydroxysteroid dehydrogenase activity represents a group of several isoenzymes (17HSDs) that catalyze the interconversion between highly active 17beta-hydroxy- and low activity 17-ketosteroids and thereby regulate the biological activity of sex steroids. The present study was carried out to characterize the expression of 17HSD isoenzymes in human mammary epithelial cells and breast tissue. In normal breast tissues 17HSD types 1 and 2 mRNAs were both evenly expressed in glandular epithelium. In two human mammary epithelial cell lines, mRNAs for 17HSD types 1, 2 and 4 were detected. In enzyme activity measurements only oxidative 17HSD activity, corresponding to either type 2 or type 4 enzyme, was present. The role of 17HSD type 4 in estrogen metabolism was further investigated, using several cell lines originating from various tissues. No correlation between the presence of 17HSD type 4 mRNA and 17HSD activity in different cultured cell lines was detected. Instead, oxidative 17HSD activity appeared in cell lines where 17HSD type 2 was expressed and reductive 17HSD activity was present in cells expressing 17HSD type 1. These data strongly suggest that in mammary epithelial cell lines the oxidative activity is due to type 2 17HSD and that oxidation of 17beta-hydroxysteroids is not the primary activity of the 17HSD type 4 enzyme.

Mammographic breast density during hormone replacement therapy: differences according to treatment

OBJECTIVE

Our purpose was to investigate the effects of various hormone replacement regimens on mammographic breast density.

STUDY DESIGN

Mammographic density was recorded in women participating in a population-based screening program. All women were nonusers of hormone replacement therapy at first mammogram and thereafter reported continuous use of the same treatment: estrogen alone (n = 50) or estrogen in cyclic (n = 75) or continuous (n = 50) combination with progestogen. Mammographic density was quantified according to the Wolfe classification.

RESULTS

An increase in mammographic density was much more common among women receiving continuous combination hormone replacement therapy (52%) than among those receiving cyclic (13%) and estrogen-only (18%) treatment. The increase in density was apparent already at first visit after the start of hormone replacement therapy. There was little change in mammographic status during long-term follow-up.

CONCLUSION

Regimens of hormone replacement therapy were shown to have different effects on the normal breast. There is an urgent need to clarify the biologic nature and significance of a change in mammographic density during treatment and, in particular, its relation to symptoms and breast cancer risk.

p53 expression in breast and endometrium during estrogen and tamoxifen treatment of surgically postmenopausal cynomolgus macaques

Estrogens are important for both normal cell growth and malignant proliferation in the mammary gland as well as in the endometrium. Tamoxifen is a non-steroidal anti-estrogen widely used in breast cancer treatment. In recent years reports have been made of an increased risk of endometrial carcinoma during tamoxifen treatment. We used surgically menopausal cynomolgus macaques to study proliferation and p53 expression during hormonal replacement therapy (HRT) and tamoxifen treatment. Animals were treated continuously for 35 months with either conjugated equine estrogens (CEE; n = 20); medroxyprogesterone acetate (MPA; n = 17); the combination of CEE + MPA (n = 13); or tamoxifen (n = 17) for 35 months. We found an increased expression of p53 in normal breast and endometrial tissue linked to CEE but not tamoxifen treatment. In the breast alveoli there was an association between proliferation measured by morphometry and p53 expression in all groups. However, in the endometrium CEE induced significantly more p53 positivity than tamoxifen, 9/20 vs. 3/17 in glands and 9/19 vs. 0/17 in stroma, respectively. If indeed long-term treatment with tamoxifen as in the present study could inactivate the tumor-suppressive function of p53, endometrial cells might thereby become more susceptible to genetic lesions associated with carcinogenesis.

Effects of sex steroids on proliferation in normal mammary tissue

Numerous women are treated with a combination of oestrogen and progestogen for contraception and hormone replacement therapy worldwide. A possible increased risk of cancer in target organs has been discussed vividly for many years. While oestrogens are clearly mitogenic for breast epithelial cells, there has been considerable uncertainty about the effects of progestogens. This article reviews current knowledge on this field, including our own data. Oestrogen receptors are down-regulated during the luteal phase, while progesterone receptors remain at a high level throughout the menstrual cycle. According to most studies, in vivo proliferation of normal breast epithelial cells is higher during the luteal phase in the vast majority of women. Normal breast tissue can convert oestrone sulphate to oestradiol. A negative correlation between the levels of circulating oestradiol and the enzyme converting oestrone into oestradiol suggests a local regulatory mechanism of tissue oestradiol formation. Serum progesterone levels correlate positively with sulphatase activity while 19-norsteroid progestogens may be inhibitory. We found that long-term continuous combined hormonal treatment with conjugated equine oestrogens and medroxyprogesterone acetate induced a proliferative response in the breasts of surgically postmenopausal macaques. The effect of combined treatment was more pronounced than that of oestrogen treatment alone. Both endogenous progesterone and exogenous progestogens increase proliferation of breast epithelial cells. Exogenous progestogens down-regulate both oestrogen and progesterone receptors. Oestrogen and progestogens may have both direct and indirect stimulating effects on proliferation. The finding of a positive correlation between insulin-like growth factor I messenger RNA and proliferation found in hormonally treated women with low receptor levels suggests the possibility of nonreceptor-mediated effects of sex steroids on proliferation, which needs to be investigated further.

17Beta-hydroxysteroid dehydrogenase type 1 in normal breast tissue during the menstrual cycle and hormonal contraception

Our purpose was to assess 17beta-hydroxysteroid dehydrogenase (17HSD) type 1 protein expression in normal breast tissue during the menstrual cycle and hormonal contraception. We analyzed 17HSD type 1 protein expression by immunohistochemistry during the regular menstrual cycle (n = 12) and hormonal contraception (n = 7) in women undergoing reduction mammoplasty. 17HSD type 1 protein was detected in normal breast epithelial cells throughout the menstrual cycle and in all women using hormonal contraception. Mean 17HSD type 1 staining intensity was higher in alveolar epithelial cells in women using hormonal contraception (2.14) than in untreated women (1.25; P < 0.04). For ducts, this difference approached significance (2.29 vs. 1.41; P = 0.06). There was a negative correlation between serum estradiol (E2) levels and 17HSD type 1 protein expression for both alveolar (r(s) = -0.68; P = 0.004) and ductal (r(s) = -0.75; P = 0.002) breast epithelial cells. Enhanced 17HSD type 1 protein expression might increase the conversion to E2 in normal breast tissue during hormonal contraception. The negative correlation between serum E2 levels and 17HSD type 1 suggests this enzyme to be one of the regulatory mechanisms of intratissue E2 concentration in normal breast tissue.

Regional distribution of proliferating cells and hormone receptors in the mammary gland of surgically postmenopausal macaques

OBJECTIVE

To define the relative proliferative response and hormone receptors status in ten sites in the mammary gland of surgically postmenopausal cynomolgus macaques given hormone replacement therapy.

METHODS

Surgical postmenopausal cynomolgus macaques were given either no treatment (n = 4), conjugated equine estrogens (CEE, n = 4), or combined therapy with CEE and medroxyprogesterone acetate (n = 4). The drugs were administered in the diet, at doses equivalent on a caloric basis to 0.625 mg/woman/day for CEE and 2.5 mg/woman/day for medroxyprogesterone acetate. Immunostaining of mammary sections was done for estrogen receptor, progesterone receptor, and the proliferation marker Ki-67 MIB-1 (MIB). Comparisons were made between central and peripheral gland, by quadrant, left versus right, and with respect to distance from the nipple within each quadrant.

RESULT

There were no significant differences in hormone receptor or MIB expression within different sites within the gland.

CONCLUSIONS

In the surgically postmenopausal, hormone-treated macaque, regional differences in estrogen and progesterone receptors and MIB staining are not apparent. The assumption of homogeneity throughout the gland makes aspiration cytology and multiple biopsy studies feasible in this species.

Proliferation of breast epithelial cells in healthy women during the menstrual cycle

OBJECTIVE

Our objective was to assess proliferation in normal breast epithelial cells from healthy women during the follicular and luteal phases of the menstrual cycle.

STUDY DESIGN

We analyzed the proliferation marker Ki-67/MIB-1 by immunocytochemical methods in breast epithelial cells procured through fine needle aspiration biopsy from 47 healthy volunteers. Differences were assessed by Wilcoxon rank sum tests, and correlations were determined by Spearman's rank correlation coefficient.

RESULTS

The proportion of KI-67/MIB-1-positive cells was higher in the luteal phase (2.04%) than in the follicular phase (1.66%). The values in women aged < 35 years were 2.29% and 1.13%, respectively (p = 0.003). In ovulating women with two aspirates during the same menstrual cycle the percentage of proliferating cells increased from the follicular phase (1.3%) to the luteal phase (2.4%) (p < 0.04). Proliferation was positively correlated with serum progesterone levels the day of aspiration (r = 0.34, p < 0.05).

CONCLUSION

The fine needle aspiration biopsy technique is a valuable tool for in vivo studies of cell proliferation in the normal breast. Data clearly suggest a proliferative action of progesterone.

Hormonal regulation of the normal breast

The breast is a target organ for reproductive hormones but basic knowledge on hormonal effects is very poor. Available data indicate that the breast is regulated in a specific manner which is distinct from the endometrium and other target organs. It seems clear that the breast undergoes cyclic changes during the menstrual cycle and that in vivo there is a direct stimulatory action of progestogens on the breast. In surgically postmenopausal female macaques continuous combined estrogen/progestogen therapy was found to induce greater proliferation than estrogen alone.

Metabolism of estrone sulfate by normal breast tissue: influence of menopausal status and oral contraceptives

The metabolism of [3H]estrone sulfate ([3H]E1S) was studied in normal breast tissue from 10 premenopausal women without oral contraceptives (OC), in 12 OC users and in 9 untreated postmenopausal women. [3H]E1S was converted into estrone ([3H]E1) and estradiol-17 beta ([3H]E2) by tissue samples from all three groups of women, with only minor formation of other unconjugated compounds. The rate of [3H]E2 formation was significantly higher in premenopausal women without OC than in postmenopausal women. Among premenopausal women, OC users had a significantly lower rate of total hydrolysis and of [3H]E1 formation than non-users. The rate of total hydrolysis of [3H]E1S in normal breast tissue from all three groups of women was similar to that in muscle, but the rate of [3H]E2 formation was ten times higher. Both total hydrolysis rate and rate of [3H]E2 formation were significantly lower in normal breast tissue than in breast carcinoma and in normal and neoplastic endometrium. The specific ability of normal breast tissue to convert E1S into the terminal biologically active estrogen E2 may be important for estrogenic stimulation of the breast in subjects with low circulating E2 levels. The lower rate of E1 formation in OC users may reflect an inhibitory effect of the progestagen compound in such preparations.

Estrogen and progesterone receptor content in breast epithelial cells from healthy women during the menstrual cycle

OBJECTIVE

Our objective was to analyze the presence of estrogen and progesterone receptors in breast epithelial cells from healthy women during the follicular and luteal phase of the menstrual cycle.

STUDY DESIGN

We analyzed estrogen receptor and progesterone receptor variations in breast epithelial cells procured through fine-needle aspiration biopsy from 42 healthy volunteers during the menstrual cycle using immunocytochemical receptor analysis. Differences were assessed by chi 2 test and the Wilcoxon rank sum tests.

RESULTS

Estrogen receptor was detected more often in women aspirated in the follicular (68%) than in the luteal (32%) phase (p < 0.001); progesterone receptor was detected in around 80% in both phases. In ovulating women who were aspirated twice during the same menstrual cycle the proportion of estrogen receptor-positive cells was reduced from 20% to 4% (p < 0.02); the progesterone receptor values were 17% and 24%.

CONCLUSION

Our data indicate an important difference in progesterone receptor variation in the breast as compared with the endometrium.