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

Nonhuman primate model in mammary gland biology and neoplasia research

Research on breast cancer pathogenesis, prevention and drug development remains an important field as this disease is still one of the leading causes of cancer death worldwide. Nonhuman primates, particularly macaque species, may serve as a highly translational animal model in breast cancer studies due to their similarity with humans in genetics, anatomy, reproductive and endocrine physiology including mammary gland development profile. The use of nonhuman primates in biomedical research, however, requires high ethical standards and an increasing expectation to improve strategies to replace, reduce and refine their use. Here, we discuss some key features of nonhuman primate mammary gland biology relevant to their strengths and limitations as models in studies of breast development and cancer risk.

Sex steroid hormone receptor expression in the vaginal wall in cervical cancer survivors after radiotherapy

Background: Sex steroid hormones and their receptors are important in female sexual function. The aim of this study was to investigate the expression and distribution of estrogen receptor (ER)α, ERβ, G-protein-coupled ER-1 (GPER), androgen receptor (AR), progesterone receptor (PR)A, PRB and connective tissue growth factor (CTGF) in the vaginal wall among women who had been treated for cervical cancer with radiotherapy. Material and methods: We included cervical cancer survivors treated with radiotherapy and premenopausal control women of the same age scheduled for benign gynecological surgery. We analyzed the expression and distribution of sex steroid hormone receptors and CTGF in biopsies from the vaginal wall, by real-time PCR and immunohistochemistry (IHC). Serum samples were analyzed for hormone levels and radiation dose at biopsy site were calculated and correlated to levels of the sex steroid hormone receptors. Results: In the cervical cancer survivors (n = 34), we found a lower expression of ERα at both mRNA and protein levels, compared to the control women (n = 37). In the survivors with high radiation dose at biopsy site, the immunostaining of ERα and AR was lower in the epithelium and the stroma, compared to survivors with minimal radiation dose. The later group showed expression of ERα comparable to the control women. The cancer survivors were sufficiently substituted with systemic estradiol with no difference in the serum estradiol levels compared to control women. Conclusions: We found that external radiation reduces the ERα and AR protein expression in the vaginal mucosa, indicating that the vaginal changes in irradiated cervical cancer survivors and the lack of response to hormonal treatment could be due to the decreases in sex steroid hormone receptor expression.

SUMOylation Regulates Transcription by the Progesterone Receptor A Isoform in a Target Gene Selective Manner

Luminal breast cancers express estrogen (ER) and progesterone (PR) receptors, and respond to endocrine therapies. However, some ER+PR+ tumors display intrinsic or acquired resistance, possibly related to PR. Two PR isoforms, PR-A and PR-B, regulate distinct gene subsets that may differentially influence tumor fate. A high PR-A:PR-B ratio is associated with poor prognosis and tamoxifen resistance. We speculate that excessive PR-A marks tumors that will relapse early. Here we address mechanisms by which PR-A regulate transcription, focusing on SUMOylation. We use receptor mutants and synthetic promoter/reporters to show that SUMOylation deficiency or the deSUMOylase SENP1 enhance transcription by PR-A, independent of the receptors’ dimerization interface or DNA binding domain. De-SUMOylation exposes the agonist properties of the antiprogestin RU486. Thus, on synthetic promoters, SUMOylation functions as an independent brake on transcription by PR-A. What about PR-A SUMOylation of endogenous human breast cancer genes? To study these, we used gene expression profiling. Surprisingly, PR-A SUMOylation influences progestin target genes differentially, with some upregulated, others down-regulated, and others unaffected. Hormone-independent gene regulation is also PR-A SUMOylation dependent. Several SUMOylated genes were analyzed in clinical breast cancer database. In sum, we show that SUMOylation does not simply repress PR-A. Rather it regulates PR-A activity in a target selective manner including genes associated with poor prognosis, shortened survival, and metastasis.

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.

Comparison of the Effects of the Selective Estrogen Receptor Modulators Ospemifene, Raloxifene, and Tamoxifen on Breast Tissue in Ex Vivo Culture

Explant tissue culture provides a model for studying the direct effects of steroid hormones, their analogs, and novel hormonally active compounds on normal freshly isolated human breast tissues (HBTs). For this purpose, pre- and postmenopausal HBTs can be maintained in this culture system. The results demonstrate that the morphological integrity of HBT explants can be maintained in tissue culture up to 2 weeks and expression of differentiation markers, steroid hormone receptors, proliferation and apoptosis ratios can be evaluated as a response to hormonal stimulation. This chapter describes an ex vivo culture model that we have applied to study the effects of various hormonally active substances, including 17β-estradiol and selective estrogen receptor modulators (SERMs), on normal human breast tissues.

Progesterone receptor A predominance is a discriminator of benefit from endocrine therapy in the ATAC trial

Progesterone receptor (PR) function, while essential in normal human breast, is also implicated in breast cancer risk. The two progesterone receptors, PRA and PRB, are co-expressed at equivalent levels in normal breast, but early in carcinogenesis normal levels of PRA:PRB are frequently disrupted, and predominance of one isoform, usually PRA, results. In model systems, PRA and PRB have different activities, and altering the PRA:PRB ratio in cell lines alters PR signaling. The purpose of this study was to determine whether hormonal or reproductive factors contribute to imbalanced PRA:PRB expression in breast tumors and the impact of PRA:PRB imbalance on disease outcome. The relative expression of PRA and PRB proteins was determined by dual immunofluorescence histochemistry in archival breast tumors and associations with clinical and reproductive history assessed. PRA:PRB expression was not influenced by reproductive factors, whereas exogenous hormone use (menopausal hormone treatment, MHT) favored PRB expression (p < 0.035). The PRA:PRB ratio may be a discriminator of response to endocrine therapy in the TransATAC sample collection, with high PRA:PRB ratio predicting earlier relapse for women on tamoxifen, but not anastrozole (mean lnPRA:PRB ratio; HR (95 % CI) tamoxifen 2.45 (1.20-4.99); p value 0.02; anastrozole 0.80 (0.36-1.78); p value 0.60). The results of this study show that PRA:PRB imbalance in breast cancers is not associated with lifetime endogenous endocrine and reproductive factors, but is associated with MHT use, and that PRA predominance can discriminate those women who will relapse earlier on tamoxifen treatment. These data support a role for imbalanced PRA:PRB expression in breast cancer progression and relative benefit from endocrine treatment.

Effects of hormonally active agents on steroid hormone receptor expression and cell proliferation in the myometrium of ovariectomized macaques

Hormone replacement therapy and selective estrogen receptor modulators have been controversial treatment options for postmenopausal women because of their potential health benefits and/or risks. In this study, we determine the effects of the hormonally active compounds, conjugated equine estrogens (CEE), medroxyprogesterone acetate (MPA), CEE + MPA, and tamoxifen (TAM) on the myometrium of ovariectomized macaques. Immunoexpression of estrogen receptor-α (ERα), progesterone receptor (PR), and Ki-67 in the myometrium is assessed. We found no significant difference in ERα myometrial expression in the CEE, MPA, and CEE + MPA treatment groups, but there was a significant decrease in expression in animals administered TAM versus controls. Conjugated equine estrogen-, TAM-, and CEE + MPA-treated animals had significantly increased expression of PR in myometrial cells and there was no difference in PR expression in cells from MPA-treated animals versus control animals. Myometrial cell proliferation did not significantly differ between the controls and any of the treatment groups, although normalized Ki-67 values were somewhat higher in the CEE and TAM groups. These data suggest that ERα and PR expression in the myometrium is influenced by treatment with hormonally active agents.

Effects of mating on progesterone receptor isoforms in rat hypothalamus

In rodents, the display of sexual behavior during proestrus-estrus transition depends on the effect of estradiol and progesterone. Progesterone exerts its effects through intracellular receptor (PR) of which two isoforms (PR-A and PR-B) are found, with different regulation and function. In this study the effects of mating on the expression pattern of PR isoforms in the hypothalamus were investigated during proestrus-estrus transition by using western blot. PR-B isoform content significantly diminished during proestrus-estrus transition both in mated and nonmated female rats. In contrast, PR-A isoform content significantly increases during this period in nonmated rats, whereas it does not change in mated animals. These data show that PR isoforms are differentially expressed throughout proestrus-estrus transition and that mating modifies PR isoforms expression in the hypothalamus of the rat.

Endometrial profile of tamoxifen and low-dose estradiol combination therapy

PURPOSE

Combination estrogen + progestin therapy has been associated with increased breast cancer risk in postmenopausal women. Selective estrogen receptor modulators (SERM) are potential alternatives to progestins, although the endometrial safety of estrogen + SERM co-therapies is not known. The goal of this study was to evaluate the endometrial profile of low-dose estradiol and the SERM tamoxifen alone and in combination.

EXPERIMENTAL DESIGN

Twenty-four postmenopausal female cynomolgus macaques were randomized by social group to receive placebo, low-dose micronized estradiol (E(2); 0.25 mg/1,800 kcal), the SERM tamoxifen (Tam; 20 mg/1,800 kcal), or E(2) + Tam for 4 months in a parallel-arm design.

RESULTS

Tamoxifen alone resulted in overlapping but distinct effects compared with E(2). Both E(2) and Tam increased uterine weight and endometrial thickness, whereas only E(2) increased endometrial proliferation. Morphologic effects were similar for Tam and E(2) + Tam, which both induced stromal fibrosis and cystic change. Tamoxifen inhibited E(2)-induced proliferation and expression of genes related to cell cycle progression while exhibiting mixed agonist and antagonist effects on gene markers of estrogen receptor activity. The gene expression profile for E(2) + Tam was distinct from either E(2) or Tam alone but dominated by the Tam effect for estrogen-regulated genes. Tam also attenuated E(2) effects on both vaginal maturation and cervical epithelial height.

CONCLUSIONS

These findings characterize a novel phenotype resulting from estrogen + SERM co-therapy. The predominance of Tam effects on endometrial proliferation, morphology, and transcriptional profiles suggests that endometrial risks for E(2) + Tam may be similar to Tam alone.

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.

Effect of tamoxifen on endometrial histology, hormone receptors, and cervical cytology: a prospective study with follow-up

OBJECTIVES

Our major hypothesis for these studies was that tamoxifen's varied effects on the endometrium might be due in part to differences in effect on estrogen and progesterone receptors [ER, progesterone receptor isoform A (PRA), and progesterone receptor isoform B (PRB)]. We aimed to evaluate the changes in histology in serial endometrial biopsies (Em bx), Papanicolaou smears (Pap smears), and endometrial ultrasounds as well as changes in the expression of ER, PRA, and PRB in response to tamoxifen. We propose that understanding and correlating the dynamics of receptor expression with histologic and cytologic changes will help us better understand the effect of tamoxifen on the endometrium and its role in the development of endometrial carcinoma in some patients.

METHODS

Forty-two patients to be started on tamoxifen underwent a pretreatment Em bx and Pap smear. Follow-up serial Em bxs and Pap smears were obtained at sixth month and then at yearly intervals for up to 6 biopsies per case. Maturation indices (MIs) were determined on the Pap smears, and ER, PRA, and PRB immunostains were performed on the biopsies. Follow-up data is for a maximum of 10 years. Trends in changes in endometrial histology were analyzed and when atrophic or inactive endometrium changed to proliferative endometrium on treatment it was considered to be an increase in estrogen effect and the vice versa changes as a decrease in estrogen effect.

RESULTS

None of the subjects developed hyperplasia or malignancy. Two patients' Em bx demonstrated atypical cells associated with eosinophilic metaplasia, but subsequent biopsies had no atypia. Of the 42 patients, 37 had serial Em bxs in which evaluation for trends could be performed. Twelve of 37 (32.4%) had an overall decrease in estrogen effect on endometrial histology with another 12/37 (32.4%) showing no estrogenic effect on endometrial histology. Six of 37 patients (16.2%) showed an increased estrogen effect on endometrial histology. Seven of 37 (18.9%) had variable endometrial histology with no definable pattern. There was a statistically significant increase in PRA expression compared with baseline as time progressed (P<0.05). The PRB showed a contrasting significant decrease in expression at 2.5 and 3.5 years (P<0.05). There was no significant change in ER expression over the course of the study (P>0.05). Seven of 12 (58.3%) with a decreased estrogenic effect on endometrial histology had a concordant decrease in PRB expression. Seven of 12 (58.3%) with no change in endometrial histology also had a concordant decrease in PRB expression. Comparing the MI of Pap smears with histologic activity of the endometrium revealed minimal correlation between the two. However, in the patients with an increased estrogen effect on endometrial histologic activity, there was no correlation with the MI. Additionally, 57% of patients showed no correlation between endometrial histologic activity and ultrasound findings.

CONCLUSIONS

Tamoxifen had an antiestrogenic or neutral effect on endometrial histology and Pap smears of most subjects, but estrogenic, or variable effects were also observed in a minority of patients. Tamoxifen treatment was accompanied by an uncoupling of the regulation of PRA and PRB expression without effect on ER expression. Overall, expression of PRB decreased whereas that of PRA increased.

Hormone replacement therapy and cancers: the biological roles of estrogen and progestin in tumorigenesis are different between the endometrium and breast

Hormone replacement therapy (HRT) has become available over the past few decades, but the risk of breast cancer with HRT remains controversial. The Women's Health Initiative Study has recently demonstrated that women receiving estrogen plus progestin (HRT) have an increased risk of invasive breast carcinoma, although women receiving estrogen alone (estrogen replacement therapy) exhibit no increased risk of breast carcinoma. By contrast, the risk of endometrial carcinoma increases with estrogen replacement therapy, while HRT reduces the risk of endometrial carcinoma. These clinical findings suggest that the biological roles of estrogen and progestin in tumorigenesis are certainly different between the endometrium and breast, although both are considered "estrogen-dependent tissues". In this review, I summarize the recent studies and indicate that the enzymes responsible for intratumoral estrogen metabolism and biosynthesis are markedly different between human breast and endometrial carcinomas. 17beta-hydroxysteroid dehydrogenases (17-HSDs) are enzymes estrogen replacement therapyinvolved in the formation of active sex steroids. Estrogens are interconverted by two enzymes, 17-HSD types 1 and 2. Type 1 converts estrone to estradiol, and type 2 catalyzes the reverse reaction. 17-HSD type 5 reduces androstenedione to testosterone. 17-HSD type 1 plays an important role in the regulation of high estradiol levels in breast carcinoma tissues, whereas 17-HSD types 2 and 5 appear to be essential for the maintenance of estradiol concentrations in endometrial carcinoma tissues. In addition, the biological significance of progesterone receptor isoforms differs between endometrial and breast carcinomas. These findings may provide new insights into the biology of "estrogen-dependent tissues".

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.

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.

Effects of estradiol and medroxyprogesterone acetate on morphology, proliferation and apoptosis of human breast tissue in organ cultures

Background

Human breast tissue undergoes phases of proliferation, differentiation and regression regulated by changes of the levels of circulating sex hormones during the menstrual cycle or aging. Ovarian hormones also likely play a key role in the etiology and biology of breast cancer. Reports concerning the proliferative effects of steroid hormones on the normal epithelium of human breast have been conflicting. Some studies have shown that steroid hormones may predispose breast epithelial cells to malignant changes by stimulating their proliferation, which is known to be regulated tightly by stromal cells.

The aim of this study was to investigate the effects of 17β-estradiol and medroxyprogesterone acetate on proliferation, apoptosis, expression of differentiation markers and steroid hormone receptors in breast epithelium using an in vitro model of freshly isolated human breast tissue, in which a proper interaction of breast epithelium and stroma has been maintained.

Methods

Human breast tissues were obtained from women undergoing surgery for breast tumours. Peritumoral tissues were excised and explants were cultured for 3 weeks in medium supplemented with E₂ or MPA or with E₂+MPA. Endpoints included histopathological, histomorphometric and immunohistochemical assessment of the breast explants.

Results

Culture of breast explants for 14 or 21 days with steroid hormones increased proliferative activity and the thickness of acinar and ductal epithelium. E₂-treatment led to hyperplastic epithelial morphology, MPA to hypersecretory single-layered epithelium and E₂+MPA to multilayered but organised epithelium.

The proliferative response to E₂ in comparison to control (p < 0.001) was more pronounced than to MPA (p < 0.05) or E₂+MPA (p < 0.05) at 7 and 14 days for Ki-67 and PCNA. E₂ treatment also decreased the proportion of apoptotic cells after 7 (p < 0.01) and 14 (p < 0.01) days. In addition, the relative number of ERα, ERβ and PR positive epithelial cells was decreased by all hormonal treatments.

Conclusion

Organ culture system provides a model for studying the direct effects of steroid hormones and their analogues on postmenopausal human breast tissue.

Addition of E₂ or MPA or E₂+MPA to breast explants caused characteristic changes in morphology, stimulated epithelial proliferation, lowered apoptosis ratio and decreased the relative number of epithelial cells expressing ERα, ERβ and PR.

Expression of sex steroid receptor subtypes in normal and malignant breast tissue - a pilot study in postmenopausal women

Female sex steroids are implied in breast cancer development. The estrogen (ER) and progesterone (PR) receptor subtypes may have different roles to modulate the cellular response. Paired samples of cancer and adjacent normal tissue were collected from postmenopausal women at surgery for ductal breast cancer. The expression of ERa, ERss, PRA and PRB was quantified by immunostaining and digitized image analysis. We found ERss to be significantly reduced in breast cancer tissue (35% vs 50%; p?=?0.001) and there was also a decrease of the ERss/ERa ratio. Among women using hormones at the time of diagnosis tumor tissue showed higher values for both PRB and PRA, as compared to women without such treatment. The results extend previous animal data to be valid also in women. There is evidence that loss of ERss expression may relate to estrogen dependent tumor progression. Increased PR expression could possibly relate to breast cancer risk during combined estrogen/progestogen treatment.

Proteome analysis of combined effects of androgen and estrogen on the mouse mammary gland

We and other investigators have previously shown that estrogen and androgen have synergistic effects on the growth of mammary epithelial ducts and alveoli in the Noble mouse. However, the molecular mechanisms behind the synergy are unknown. In the present study, we treated female FVB mice with 17-estrodial (E2) and 5-dihydrotestosterone-bezonate (DHT-B) using slow-releasing hormone pellets for 7 months. Dissection showed that hormone treatment caused atypical hyperplasia of mammary ducts and alveoli. A functional proteomic approach was used to study the holistic protein changes in mammary glands. 2-DE was used to separate proteins. Twenty-five protein spots that were differentially expressed in hormone-treated tissues compared to the control were identified by MALDI-TOF-MS, and ESI-quadrupole-TOF-MS, which include some proteins that are correlative with response to estrogen and androgen stimulation, cells differentiation and growth, signal transduction, metabolism, etc. Real-time RT-PCR was carried out to verify the different expression. These results offered some clues to understand the function of E2 and DHT-B.

Can molecular markers predict when to implement treatment with aromatase inhibitors in invasive breast cancer?

PURPOSE

Resistance to tamoxifen is linked to overexpression of HER2, and aromatase inhibitors show particular benefit in progesterone receptor (PR)-negative patients. We previously reported reduced survival in patients overexpressing HER1, HER2, and HER3. We now show that both HER1-3 and PR status predicts for early relapse in estrogen receptor (ER)-positive tamoxifen-treated breast cancer patients.

EXPERIMENTAL DESIGN

Tissue microarray technology was used to analyze 402 ER-positive tamoxifen-treated patients. Immunohistochemistry using epidermal growth factor receptor, HER2, HER3, HER4, and PR antibodies was done. Kaplan-Meier life table and Cox Regression analysis (log-rank testing of differences in breast cancer-related relapse on tamoxifen) was done.

RESULTS

HER1-3 (but not HER4) overexpression predicted for early relapse on tamoxifen (P = 0.0060). PR-negative cases were also significantly more likely to relapse while on tamoxifen (P= 0.017). HER1-3-positive and/or PR-negative patients combined as a "high-risk" group were significantly more likely to relapse on tamoxifen in univariate (P < 0.0001) and Cox's multivariate analysis (P = 0.0069). However, this applied to early relapse on tamoxifen only, as any disease relapse after 3 years of tamoxifen was unrelated to PR/HER status.

CONCLUSIONS

We show that HER1-3 and PR status can identify time-dependent de novo tamoxifen resistance with risk declining markedly after 3 years of tamoxifen treatment. These results parallel data from the ATAC and Intergroup Exemastane Study trials which suggest that whereas PR-negative patients derive greater benefit from initial aromatase inhibitor treatment, PR status has no effect on response when given as delayed treatment to those disease free on tamoxifen after 3 years.

Progesterone-independent effects of human progesterone receptors (PRs) in estrogen receptor-positive breast cancer: PR isoform-specific gene regulation and tumor biology

Progesterone receptors (PRs) are prognostic markers in breast cancers irrespective of the patient's progestational status. However, there are two PR isoforms, PR-A and PR-B, that are equimolar in the normal breast but dysregulated in advanced disease. Postmenopausal, tamoxifen-treated patients with estrogen receptor (ER)-positive, PR-A-rich tumors have much faster disease recurrence than patients with PR-B-rich tumors. To study the mechanisms we engineered ER+ breast cancer cells that express each PR isoform under control of an inducible promoter. We identified 79 genes regulated by progesterone (P), mainly by PR-B, and 51 genes regulated without progesterone, mainly by PR-A. Only nine genes were regulated with and without ligand, leading to definition of three classes: I) genes regulated only by liganded PR; II) genes regulated only by unliganded PR; III) genes regulated by both. Unliganded PR-A and PR-B differentially regulate genes that coordinate extracellular signaling pathways and influence tumor cell biology. Indeed, in the absence of P, compared with ER+/PR-B+ or PR- cells, ER+, PR-A+ cells exhibit an aggressive phenotype, are more adhesive to an extracellular matrix, and are more migratory. Additionally, unliganded PR-A and PR-B both inhibit cell growth and provoke resistance to Taxol-induced apoptosis. We propose that PR-A:PR-B ratios, even in the absence of P, influence the biology and treatment response of ER+ tumors, that PR-A isoforms are functionally dominant in P-deficient states, and that PR-A rich tumors are especially aggressive.

Exogenous progestagens and the human breast

The role of progestins (or progestagens) on the breast tissue remains controversial. However, according to the molecule and the duration of application, cell differentiation and apoptosis may predominate over proliferation. Progestins are also used as second-line agents for the treatment of metastatic breast cancer. In young women with benign breast disease, long-term treatment with 19-nortestosterone progestins had a trend to decrease breast cancer risk contrarily to what was observed in postmenopausal women receiving estrogens. Several compounds with progestational activity have been used for HRT. Small differences in the structure of the molecules may lead to pronounced differences in activities, some progestins exerting androgenic effects and some exerting estrogenic or glucocorticoid like activities. While most progestins do not bind to the estrogen receptors, it has been shown that some androgenic progestins stimulate MCF7 cells proliferation while progestins derived from progesterone did not induce cell multiplication in the same cell lines. Therefore, different progestins may induce different effects on the breast cells. Whether the progestins available to date are able to bind specifically to the progesterone receptors PR-A or PR-B and whether this is of clinical relevance to breast cell proliferation is still unclear. Although the relationship between progestin use and breast cancer risk is still the subject of debate and controversy, the data reported to date suggest that 5 years of treatment carry a low risk but further duration of use increases the risk. Further studies are still needed, randomised long-term prospective studies as well as from the laboratory, especially to determine whether a sequential or continuous regimen would be preferable as far as breast-cell response and apoptosis are concerned, and what are the effects of the various molecules used for HRT.

Progestin-dependent induction of vascular endothelial growth factor in human breast cancer cells: preferential regulation by progesterone receptor B

The progesterone receptor (PR) is a ligand-dependent transcription factor that promotes progestin-stimulated expression of target genes. Two functional PR isoforms, PRA and PRB, are expressed in progestin-responsive cells. PRA and PRB have distinct roles in gene expression and in mammary gland development. One role of PRs in T47-D cells is regulating expression of vascular endothelial growth factor (VEGF), a potent angiogenic growth factor. This study explores the isoform specificity of this PR function using parental T47-Dco cells that express both PRA and PRB and clonal derivatives that express either PRA (YA cells) or PRB (YB cells) or lack PR (Y cells). Treatment with progesterone induces VEGF mRNA and protein approximately 2-fold in T47-Dco and YA cells and 3-7-fold in YB cells, suggesting that PRA inhibits PRB-dependent induction of VEGF. This is consistent with the observation that clinically relevant progestins induce a much higher level of VEGF in YB cells than in YA cells. Another novel finding in this report is that estradiol (10(-8) M) induces VEGF production from YB cells. However, this induction is not blocked by 100-fold excess tamoxifen or ICI-182,780. Moreover, both tamoxifen (10(-6) M) and ICI-182,780 (10(-6) M) function as agonists for VEGF in YB cells. Small interfering RNA against PR or estrogen receptor abrogated estradiol and tamoxifen induction, indicating that the agonist-like response of these compounds in YB cells is estrogen receptor and PR dependent. Estradiol, tamoxifen, and ICI-182780 also induce VEGF in BT-474 cells when their PRB levels were elevated by transfecting an expression plasmid for PRB, but not when the cells were transfected with vector alone. These results indicate that (a) PRB preferentially regulates VEGF expression in breast cancer cells and (b) PRB-enriched tumor cells may produce more VEGF, have a better developed vasculature, and potentially are more resistant to tamoxifen and ICI-182,780 than cells that express an equivalent or higher level of PRA than PRB. These results imply that PRB-enriched breast tumors may respond well to anticancer therapies that include inhibitors of angiogenesis.

New Progestogens

The progestins have different pharmacological properties depending upon the parent molecule, usually testosterone or progesterone, from which they are derived. Very small structural changes in the parent molecule may induce considerable differences in the activity of the derivative. In postmenopausal women with an intact uterus, progestins are used in combination with estrogen as hormone-replacement therapy (HRT). The development of new generations of progestins with improved selectivity profiles has been a great challenge. Steroidal and nonsteroidal progesterone-receptor (PR) agonists have been synthesised as well, although the latter are still in a very early stage of development. Several new progestins, which have been synthesised in the last 2 decades, may be considered fourth-generation progestins. These include dienogest, drospirenone, Nestorone (Population Council, New York, NY, USA), nomegestrol acetate and trimegestone. The fourth-generation progestins have been designed to have no androgenic or estrogenic actions and to be closer in activity to the physiological hormone progesterone. Drospirenone differs from the classic progestins as it is derived from spirolactone. It is essentially an antimineralocorticoid steroid with no androgenic effect but a partial antiandrogenic effect. The antiovulatory potency of the different progestins varies. Trimegestone and Nestorone are the most potent progestins synthesised to date, followed by two of the older progestins, 3-keto-desogestrel and levonorgestrel. The new molecules trimegestone, drospirenone and dienogest also have antiandrogenic activity. Following the publication of the results of the Women's Health Initiative study, the role of progestins in HRT became controversial. Unfortunately, this concern has been directed towards progestins as a class, although striking differences exist among the progestins. Natural progesterone and some of its derivatives, such as the 19-norprogesterone molecules, and the new molecules drospirenone and dienogest are not androgenic and, therefore, have no negative effect on the lipid profile. The effects of progestins on breast tissue remain controversial as well. However, depending on the progestin and the duration of application, breast cell differentiation and apoptosis may predominate over proliferation. It is still unclear if the currently available progestins are able to bind specifically to the PR isoforms PR-A or PR-B and whether this is of clinical relevance to breast cell proliferation is also unclear. Although it is likely that the new progestins may have neutral effects on the risk of coronary heart disease or breast cancer in younger postmenopausal women, this hypothesis must be confirmed in large randomised, well controlled clinical trials.