An in vitro long-term culture model for normal human mammary gland: expression and regulation of steroid receptors

Inter-Individual Variation in Response to Estrogen in Human Breast Explants

Exposure to estrogen is strongly associated with increased breast cancer risk. While all women are exposed to estrogen, only 12% are expected to develop breast cancer during their lifetime. These women may be more sensitive to estrogen, as rodent models have demonstrated variability in estrogen sensitivity. Our objective was to determine individual variation in expression of estrogen receptor (ER) and estrogen-induced responses in the normal human breast. Human breast tissue from female donors undergoing reduction mammoplasty surgery were collected for microarray analysis of ER expression. To examine estrogen-induced responses, breast tissue from 23 female donors were cultured ex- vivo in basal or 10 nM 17β-estradiol (E2) media for 4 days. Expression of ER genes (ESR1 and ESR2) increased significantly with age. E2 induced consistent increases in global gene transcription, but expression of target genes AREG, PGR, and TGFβ2 increased significantly only in explants from nulliparous women. E2-treatment did not induce consistent changes in proliferation or radiation induced apoptosis. Responses to estrogen are highly variable among women and not associated with levels of ER expression, suggesting differences in intracellular signaling among individuals. The differences in sensitivity to E2-stimulated responses may contribute to variation in risk of breast cancer.

Novel ex vivo ovarian cancer tissue explant assay for prediction of chemosensitivity and response to novel therapeutics

The majority of ovarian cancer patients present with advanced disease and despite aggressive treatment, prognosis remains poor. Response to first-line carboplatin-containing chemotherapy is usually good, however, recurrence rates and subsequent chemoresistance are very high and ultimately responsible for the fatal outcome of the disease. To improve treatment outcomes pre-clinical models that can predict individual patient response to 1st line chemotherapy and novel therapeutics are urgently required. In this study, we employed an ex vivo ovarian cancer tissue explant assay to assess response to carboplatin and an inhibitor of the extracellular matrix molecule, hyaluronan (4-methylubelliferone, 4-MU), shown to inhibit cancer metastasis. Cryopreserved ovarian cancer tissues were cultured on gelatine sponges for 48-120 h with increasing concentrations of carboplatin (0-400 μM) or 4-MU (1 mM) alone or the combination of both drugs. Effects on apoptosis and proliferation were assessed by immunohistochemistry using antibodies to cleaved caspase 3 or Ki67, respectively. The ex vivo tissue explant assay maintained viable tumor cells in an intact tumor microenvironment similar to the in vivo situation over the 120 h culture period. Carboplatin treatment promoted apoptosis in chemosensitive (P = 0.0047) but not chemoresistant cancer tissues. The combination of 4-MU (1 mM) and carboplatin (100 μM) significantly increased apoptosis (P = 0.0111) and reduced proliferation (P = 0.0064) in chemoresistant tissues. Overall, our results show that the ex vivo explant assay is a robust and cost effective model to assess chemosensitivity and the effect of novel therapeutics in ovarian cancer.

Human Metaplastic Breast Carcinoma and Decorin

Metaplastic breast carcinoma (MBC) is a rare subtype of invasive breast cancer and has poor prognosis. In general, cancers are heterogeneous cellular masses comprised of different cell types and their extracellular matrix (ECM). However, little is known about the composition of the ECM and its constituents in MBC. Decorin is a ubiquitous ECM macromolecule known of its oncosuppressive activity. As such, it provides an intriguing molecule in the development of novel therapeutics for different malignancies such as MBC. In this study, decorin immunoreactivity and the effect of adenoviral decorin cDNA (Ad-DCN) transduction were examined in MBC. Multiple immunohistochemical stainings were used to characterize a massive breast tumour derived from an old woman. Furthermore, three-dimensional (3D) explant cultures derived from the tumour were transduced with Ad-DCN to study the effect of the transduction on the explants. The MBC tumour was shown to be completely negative for decorin immunoreactivity demonstrating that the malignant cells were not able to synthesize decorin. Ad-DCN transduction resulted in a markedly altered cytological phenotype of MBC explants by decreasing the amount of atypical cells and by inhibiting cell proliferation. The results of this study support approaches to develop new, decorin-based adjuvant therapies for MBC.

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.

Multiple nuclear receptor signaling pathways mediate the actions of synthetic progestins in target cells

Synthetic progestins are used clinically to treat a variety of women's health issues. Although progestins are designed to signal through the progesterone receptor (PR) to elicit specific pharmacological effects, they can also variably bind to and influence the activity of other nuclear receptors within target tissues, particularly the androgen and glucocorticoid receptors and, in some cases, they regulate mineralocorticoid and estrogen receptors. This article reviews current knowledge on progestin cross-talk to nuclear receptors other than PR, their resultant effect on receptor function in different in vitro models and the potential consequences of this activity for breast, ovarian and endometrial cancer. The impact of cell and tissue context, assay type, steroid metabolism and hormonal milieu in determining progestin-mediated activity are also presented. Collectively this review highlights the complexity of progestin action and the need for consideration of multiple mechanisms that act in concert to influence their ultimate biological activity.

Hormone-responsive 3D multicellular culture model of human breast tissue

A hormone-responsive 3D human tissue-like culture system was developed in which human primary mammary epithelial cells (MECs) were co-cultured with two types of predominant mammary stromal cells on silk protein scaffolds. Silk porous scaffolds with incorporated extracellular matrix provided a compatible environment for epithelial structure morphogenesis and differentiation. The presence of stromal cells promoted MEC proliferation, induced both alveolar and ductal morphogenesis and enhanced casein expression. In contrast, only alveolar structures were observed in monocultures. The alveolar structures generated from the heterotypic cultures in vitro exhibited proper polarity similar to human breast tissue in vivo. Consistent with their phenotypic appearance, more functional differentiation of epithelial cells was also observed in the heterotypic cultures, where casein-α and -β mRNA expression were increased significantly. Additionally, this 3D multicellular culture model displayed an estrogen-responsive physiologically relevant response, evidenced by enhanced cell proliferation, aberrant morphology, changes in gene expression profile and few polarized lumen structures after estrogen treatment. This culture system offers an excellent opportunity to explore the role of cell-cell and cell-substrate interactions during mammary gland development, the consequences of hormone receptor activation on MEC behavior and morphogenesis, as well as their alteration during neoplastic transformation in human breast tissue.

Investigating and critically appraising the expression and potential role of androgen receptor in breast carcinoma

The potential role of the androgen receptor (AR) as a predictive or prognostic factor in breast cancer remains unclear. We aimed to determine the prognostic significance of AR in a cohort of breast carcinomas with long-term follow-up and to critically appraise this in the context of existing literature. Four hundred and eight cases of invasive breast cancer were incorporated into tissue microarrays (TMAs). All received tamoxifen and comprised 108 cases which relapsed and 300 cases which did not. Mean follow-up time for the former was 84 months (range 1-142, SD 38.8) and for the latter was 77 months (range 11-229, SD 49.7). TMAs were immunohistochemically stained with AR and scored as a continuous variable and using the Allred score. AR expression was significantly associated with grade, recurrence on tamoxifen, non-breast cancer death estrogen receptor alpha (ERα) and progesterone receptor (PR). AR correlated significantly with better overall survival (OS) and disease-free survival (DFS) using an Allred cut-off of 4 (log rank=0.0053 and 0.0044, respectively), and 20% positive tumor cells (log rank=0.0027 and 0.0059, respectively). AR expression was additionally associated with a reduced risk of recurrence following endocrine therapy. In summary, AR positive breast tumors have better OS and DFS and are less likely to recur following endocrine treatment.

The Role of Androgens in Normal and Malignant Breast Tissue

Androgens, like estrogens, can be synthesized in the breast. As both active androgens and their corresponding receptors are present in breast tissue, we conclude that they play a role in breast physiology. This is supported by the fact that insufficient androgen production or sensitivity results in the development of gynecomastia. Complete androgen insensitivity due to receptor defects leads to normal female breast development in these XY women. While breast development is completely inhibited by male testosterone levels, partial but not total degradation of a developed breast by androgen treatment appears to be possible. Breast cancer in early stages seems to fulfill the prerequisites of androgen responsiveness. Androgen treatment of advanced breast cancer has shown similar effectiveness as anti-estrogen or estrogen-ablative therapy, but also considerable side effects. It has been speculated that the use of selective androgen modulators (SARMs), either alone or preferably in addition to anti-estrogens or aromatase inhibitors, may be a promising alternative to current therapy modalities in hormone-dependent breast cancer. In addition, future studies on the use of SARMs in prophylactic settings seem to be justified.

In vitro expansion of human breast cancer epithelial and mesenchymal stromal cells: optimization of a coculture model for personalized therapy approaches

Molecularly targeted, customized therapies are designed based on the molecular portraits of cancer tissue. The efficacy of targeted therapy in individual patients depends on the contribution of single individual cancer cells within the context of their microenvironment. We have developed an in vitro model of human mammary epithelial-stromal cocultures to answer specific clinical questions related to breast cancer, to provide a tool with which to identify a signature in each breast tumor, and to identify the metabolic molecular targets of therapy in an attempt to optimize the efficacy of targeted therapy in each patient. Fifty-five human breast cancer samples were obtained through surgery. Epithelial and stromal cells were isolated from tissue specimens by differential centrifugation, and cryopreserved. Western blot analysis and RT-PCR were used to identify the tissue-specific expression patterns of cancer cells. Dose-response curves were constructed for the aromatase inhibitor formestane and for herceptin, and a 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide assay was done for combined treatment. We collected and cryopreserved, for future use, viable living cells from 55 breast tumor specimens from which we derived short-term cocultures. The presence of cytokeratins and vimentin was evaluated in 20 samples, and pHER2/neu and aromatase were evaluated in 4 cocultures. Formestane and herceptin had a cumulative growth-inhibitory effect on cocultures expressing epidermal growth factor receptors and aromatase. The in vitro model of human mammary epithelial-stromal cocultures reported herein can be used to examine, and to store, a patient's tumor-derived, living cells that retain the characteristics of the mother-tissue and respond, in vitro, to therapy.

Disruption of androgen receptor signaling by synthetic progestins may increase risk of developing breast cancer

There is now considerable evidence that using a combination of synthetic progestins and estrogens in hormone replacement therapy (HRT) increases the risk of breast cancer compared with estrogen alone. Furthermore, the World Health Organization has recently cited combination contraceptives, which contain synthetic progestins, as potentially carcinogenic to humans, particularly for increased breast cancer risk. Given the above observations and the current trend toward progestin-only contraception, it is important that we have a comprehensive understanding of how progestins act in the millions of women worldwide who regularly take these medications. While synthetic progestins, such as medroxyprogesterone acetate (MPA), which are currently used in both HRT and oral contraceptives were designed to act exclusively through the progesterone receptor, it is clear from both clinical and experimental settings that their effects may be mediated, in part, by binding to the androgen receptor (AR). Disruption of androgen action by synthetic progestins may have serious deleterious side effects in the breast, where the balance between estrogen signaling and androgen signaling plays a critical role in breast homeostasis. Here, we review the role of androgen signaling in the normal breast and in breast cancer and present new data demonstrating that androgen receptor function can be perturbed by low doses of MPA, similar to doses achieved in serum of women taking HRT. We propose that the observed excess of breast malignancies associated with combined HRT may be explained, in part, by synthetic progestins such as MPA acting as endocrine disruptors to negate the protective effects of androgen signaling in the breast. Understanding the role of androgen signaling in the breast and how this is modulated by synthetic progestins is necessary to determine how combined HRT alters breast cancer risk, and to inform the development of optimal preventive and treatment strategies for this disease.

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.

Estradiol increases VEGF in human breast studied by whole-tissue culture

Sex steroid exposure constitutes a risk factor for breast cancer, but little is known about the effects of sex steroids on the normal breast, largely because of the lack of convenient models. We have developed a method of culturing normal breast tissue ex vivo. We have applied this method to investigate the effects of estradiol and progesterone on the key angiogenic mediator, vascular endothelial growth factor (VEGF), in the breast. Whole breast tissue was obtained from routine reduction mammoplasty. Tissue biopsies were cultured in vitro for 1-3 weeks, and the expression of luminal cytokeratin 18 was determined by immunohistochemistry. As an application, tissue biopsies were treated in vitro for 1 week with or without estradiol or estradiol and progesterone. Estrogen receptor, progesterone receptor, and Ki-67 were analyzed, and VEGF levels were examined by quantitative immunoassay and immunohistochemistry. Whole breast tissue was cultured ex vivo for 1 week with preserved morphology. Increased detachment of the luminal epithelium was observed after 2 weeks. Estradiol increased extracellular levels of VEGF in normal breast tissue biopsy medium. The addition of progesterone had neither stimulatory nor inhibitory effects on secreted VEGF. The method of whole breast tissue culturing thus provide a means by which to explore the biology of normal breast tissue. Our results suggest that estradiol exerts pro-angiogenic effects in normal breast by increasing levels of biologically active VEGF.

Steroid receptor expression in vaginal epithelium of healthy fertile women and influences of hormonal contraceptive usage

BACKGROUND

The objective of this study was to evaluate whether long-term usage of hormonal contraceptives modifies the steroid receptor expression in the human vaginal epithelium of healthy young women.

METHODS

In a cross-sectional study, three groups of hormonal contraceptive users [combined oral contraceptives (COCs), levonorgestrel implants (LNG) and depot medroxyprogesterone acetate injections (DMPAs)] were compared to controls. Fifteen subjects (20-34 years) were enrolled to each group. Vaginal biopsies were collected at two occasions from each subject, and serum concentrations of E(2) and progesterone were measured. Monoclonal antibodies directed against progesterone receptors (PRs) and estrogen receptors (ERs) were used in immunohistochemistry on formalin-fixed tissue sections of vaginal mucosa. A program for immunohistomorphometric quantification was devised to estimate frequency of epithelial steroid receptor-expressing cells.

RESULTS

Progesterone receptor expression was markedly down-regulated and significantly reduced in DMPA users compared to controls, COC and LNG users. In DMPA users, the ER expression was significantly elevated in the first compared to the second sample, and significantly elevated compared to LNG users. Estradiol concentration in serum was significantly reduced in hormonal contraceptive users compared to controls.

CONCLUSIONS

Steroid receptor expression in human vaginal epithelium is altered by long-term use of DMPA compared to controls.

Membrane 5alpha-pregnane-3,20-dione (5alphaP) receptors in MCF-7 and MCF-10A breast cancer cells are up-regulated by estradiol and 5alphaP and down-regulated by the progesterone metabolites, 3alpha-dihydroprogesterone and 20alpha-dihydroprogesterone, with associated changes in cell proliferation and detachment

Previous studies have shown that the progesterone metabolite, 5alpha-pregnane-3,20-dione (5alphaP), exhibits mitogenic and metastatic activity in breast cell lines and that specific, high affinity receptors for 5alphaP are located in the plasma membrane fractions of tumorigenic (ER/PR-positive) MCF-7 cells. The aim of this study was to determine the effects of the mitogenic (estradiol; 5alphaP) and anti-mitogenic (3alpha-hydroxy-4-pregnen-20-one, 3alphaHP; 20alpha-hydroxy-4-pregnen-3-one, 20alphaHP) endogenous steroid hormones on 5alphaP receptor (5alphaP-R) numbers and on cell proliferation and adhesion of MCF-7 and MCF-10A cells. Exposure of MCF-7 cells for 24h to estradiol or 5alphaP resulted in significant (p < 0.05-0.001) dose-dependent increases in 5alphaP-R levels. Conversely, treatment with 3alphaHP or 20alphaHP resulted in significant (p < 0.05-0.01) dose-dependent decreases in 5alphaP-R levels. Treatment with one mitogenic and one anti-mitogenic hormone resulted in inhibition of the mitogen-induced increases, whereas treatment with two mitogenic or two anti-mitogenic hormones resulted in additive effects on 5alphaP-R numbers. Treatments with cycloheximide and actinomycin D indicate that changes in 5alphaP-R levels depend upon transcription and translation. The non-tumorigenic breast cell line, MCF-10A, was also shown to posses specific, high affinity plasma membrane receptors for 5alphaP that were up-regulated by estradiol and 5alphaP and down-regulated by 3alphaHP. Estradiol binding was demonstrated in MCF-10A cell membrane fractions and may explain the estradiol action in these cells that lack intracellular ER. In both MCF-7 and MCF-10A cells, the increases in 5alphaP-R due to estradiol or 5alphaP, and decreases due to 3alphaHP or 20alphaHP correlate with respective increases and decreases in cell proliferation as well as detachment. These results show distribution of 5alphaP-R in several cell types and they provide further evidence of the significance of progesterone metabolites and their novel membrane-associated receptors in breast cancer stimulation and control. The findings that 3alphaHP and 20alphaHP down-regulate 5alphaP-R and suppress mitogenic and metastatic activity suggest that these endogenous anti-mitogenic progesterone metabolites deserve considerations in designing new breast cancer therapeutic agents.

An overview of nomegestrol acetate selective receptor binding and lack of estrogenic action on hormone-dependent cancer cells

The specific pharmacological profile of the 19-norprogestin nomegestrol acetate (NOMAC) is, at least in part, defined by its pattern of binding affinities to the different steroid hormone receptors. In the present study, its affinity to the progesterone receptor (PgR), the androgen receptor (AR) and the estrogen receptor (ER) was re-evaluated and compared to those obtained for progesterone (P) and several progestins. The characteristics of binding to the PgR in rat uterus were determined and Ki were found to be roughly similar with 22.8 and 34.3 nM for NOMAC and P, respectively. The binding characteristics of 3H-NOMAC were also determined and compared to that of 3H-ORG2058 with Kd of 5 and 0.6 nM, respectively for rat uterus and 4 and 3 nM, respectively for human T47-D cells. Structure-affinity and -activity relationships were studied on a variety of compounds related to NOMAC in order to assess its specificity as a progestin. The effects of NOMAC on the binding of androgen to the AR were investigated, using rat ventral prostate as target model. Contrary to what was observed for MPA, the RBA of NOMAC was found to decline with time, showing anti-androgenic rather than androgenic potential, a result that was confirmed in vivo. Regarding the ER, since none of the progestins were able to compete with estrogen for binding in rat uterus as well as in Ishikawa cells, the induction of alkaline phosphatase activity (APase) was used as an estrogen-specific response. It confirmed the intrinsic estrogenicity of progestins derived from 19-nor-testosterone (19NT), norethisterone acetate (NETA), levonorgestrel (LNG) or norgestimate (NGM) and others. In contrast, all P and 19-norP derivatives remained inactive. Finally, to complete this overview of NOMAC at the sex steroid receptor levels, the lack of estrogenic or estrogenic-like activity was checked out in different in vitro models. Data from this study have demonstrated that NOMAC is a progestin that has greater steroid receptor selectivity compared to MPA or some other synthetic progestins. It may provide a better pharmacological profile than those progestins currently in use in HRT and OC.

Purified malignant mammary epithelial cells maintain hormone responsiveness in culture

Currently, the therapy for breast cancer is determined by immunohistochemical staining of the primary tumour for oestrogen receptor alpha (ERalpha). However, a proportion of ERalpha-positive patients fail to respond to tamoxifen and a proportion of ERalpha-negative patients show response. Here, we describe a novel procedure for the purification of malignant breast epithelial cells in an attempt to identify these patients at an early stage. Using this procedure, we are able to purify malignant cells to >90% purity as determined by immunohistochemical staining, cytology and fluorescent in situ hybridisation (FISH). While the malignant cells can be maintained in culture they do not proliferate in contrast to purified breast epithelial cells from reduction mammoplasties. Moreover, ERalpha and progesterone receptor (PR) expression is maintained in malignant cells, whereas normal epithelial cells rapidly lose ERalpha and PR. Functional studies were performed on the separated malignant cells in terms of their response to oestradiol and tamoxifen. Four out of the seven ERalpha-positive tumours showed a significant reduction in cell numbers after tamoxifen treatment compared to oestradiol, ERalpha negative tumours failed to show a response. We conclude that (a) it is possible to purify and maintain breast cancer cells for a sufficient period to permit functional studies and (b) ERalpha is retained in culture facilitating the use of these cells in studies of the mechanism of endocrine response and resistance in vitro.