ER and PR signaling nodes during mammary gland development

Stem Cell Division and Its Critical Role in Mammary Gland Development and Tumorigenesis: Current Progress and Remaining Challenges

The origin of breast cancer (BC) has traditionally been a focus of medical research. It is widely acknowledged that BC originates from immortal mammary stem cells and that these stem cells participate in two division modes: symmetric cell division (SCD) and asymmetrical cell division (ACD). Although both of these modes are key to the process of breast development and their imbalance is closely associated with the onset of BC, the molecular mechanisms underlying these phenomena deserve in-depth exploration. In this review, we first outline the molecular mechanisms governing ACD/SCD and analyze the role of ACD/SCD in various stages of breast development. We describe that the changes in telomerase activity, the role of polar proteins, and the stimulation of ovarian hormones subsequently lead to two distinct consequences: breast development or carcinogenesis. Finally, gene mutations, abnormalities in polar proteins, modulation of signal-transduction pathways, and alterations in the microenvironment disrupt the balance of BC stem cell division modes and cause BC. Important regulatory factors such as mammalian Inscuteable mInsc, Numb, Eya1, PKCα, PKCθ, p53, and IL-6 also play significant roles in regulating pathways of ACD/SCD and may constitute key targets for future research on stem cell division, breast development, and tumor therapy.

Pharmacogenetics in Oncology: A useful tool for individualizing drug therapy

With the continuous development of genetics in healthcare, there has been a significant contribution to the development of precision medicine, which is ultimately aimed at improving the care of patients. Generally, drug treatments used in Oncology are characterized by a narrow therapeutic range and by their potential toxicity. Knowledge of pharmacogenomics and pharmacogenetics can be very useful in the area of Oncology, as they constitute additional tools that can help to individualize patients' treatment. This work includes a description of some genes that have been revealed to be useful in the field of Oncology, as they play a role in drug prescription and in the prediction of treatment response.

Obesity Induces DNA Damage in Mammary Epithelial Cells Exacerbated by Acrylamide Treatment through CYP2E1-Mediated Oxidative Stress

Obesity and environmental toxins are risk factors for breast cancer; however, there is limited knowledge on how these risk factors interact to promote breast cancer. Acrylamide, a probable carcinogen and obesogen, is a by-product in foods prevalent in the obesity-inducing Western diet. Acrylamide is metabolized by cytochrome P450 2E1 (CYP2E1) to the genotoxic epoxide, glycidamide, and is associated with an increased risk for breast cancer. To investigate how acrylamide and obesity interact to increase breast cancer risk, female mice were fed a low-fat (LFD) or high-fat diet (HFD) and control water or water supplemented with acrylamide at levels similar to the average daily exposure in humans. While HFD significantly enhanced weight gain in mice, the addition of acrylamide did not significantly alter body weights compared to respective controls. Mammary epithelial cells from obese, acrylamide-treated mice had increased DNA strand breaks and oxidative DNA damage compared to all other groups. In vitro, glycidamide-treated COMMA-D cells showed significantly increased DNA strand breaks, while acrylamide-treated cells demonstrated significantly higher levels of intracellular reactive oxygen species. The knockdown of CYP2E1 rescued the acrylamide-induced oxidative stress. These studies suggest that long-term acrylamide exposure through foods common in the Western diet may enhance DNA damage and the CYP2E1-induced generation of oxidative stress in mammary epithelial cells, potentially enhancing obesity-induced breast cancer risk.

Breast organoid suspension cultures maintain long-term estrogen receptor expression and responsiveness

Organoid cultures offer a powerful technology to investigate many different aspects of development, physiology, and pathology of diverse tissues. Unlike standard tissue culture of primary breast epithelial cells, breast organoids preserve the epithelial lineages and architecture of the normal tissue. However, existing organoid culture methods are tedious, difficult to scale, and do not robustly retain estrogen receptor (ER) expression and responsiveness in long-term culture. Here, we describe a modified culture method to generate and maintain organoids as suspension cultures in reconstituted basement membrane (™Matrigel). This method improves organoid growth and uniformity compared to the conventional Matrigel dome embedding method, while maintaining the fidelity of the three major epithelial lineages. Using this adopted method, we are able to culture and passage purified hormone sensing (HS) cells that retain ER responsiveness upon estrogen stimulation in long-term culture. This culture system presents a valuable platform to study the events involved in initiation and evolution of ER-positive breast cancer.

A Molecular Typing Method for Invasive Breast Cancer by Serum Raman Spectroscopy

BACKGROUND

The incidence of breast cancer ranks highest among cancers and is exceedingly heterogeneous. Immunohistochemical staining is commonly used clinically to identify the molecular subtype for subsequent treatment and prognosis.

PURPOSE

Raman spectroscopy and support vector machine (SVM) learning algorithm were utilized to identify blood samples from breast cancer patients in order to investigate a novel molecular typing approach.

METHOD

Tumor tissue coarse needle aspiration biopsy samples, and peripheral venous blood samples were gathered from 459 invasive breast cancer patients admitted to the breast department of Sichuan Cancer Hospital between June 2021 and September 2022. Immunohistochemical staining and in situ hybridization were performed on the coarse needle aspiration biopsy tissues to obtain their molecular typing pathological labels, including: 70 cases of Luminal A, 167 cases of Luminal B (HER2-positive), 57 cases of Luminal B (HER2-negative), 84 cases of HER2-positive, and 81 cases of triple-negative. Blood samples were processed to obtained Raman spectra taken for SVM classification models establishment with machine algorithms (using 80% of the sample data as the training set), and then the performance of the SVM classification models was evaluated by the independent validation set (20% of the sample data).

RESULTS

The AUC values of SVM classification models remained above 0.85, demonstrating outstanding model performance and excellent subtype discrimination of breast cancer molecular subtypes.

CONCLUSION

Raman spectroscopy of serum samples can promptly and precisely detect the molecular subtype of invasive breast cancer, which has the potential for clinical value.

Progesterone receptor-Grb2 interaction is associated with better outcomes in breast cancer

In addition to mediating nuclear transcription, PR mediates extranuclear functions mainly through the PR polyproline domain (PPD) interaction with the SH3 domain of cytoplasmic signaling molecules. PR-PPD-SH3 interaction inhibits EGF-mediated signaling and decreases lung cancer cell proliferation. Grb2 is an essential adaptor molecule with an SH2 domain flanked by two SH3 domains. In this study, we examined whether PR, through interaction between PR-PPD and Grb2-SH3, can interact with Grb2 in cells and breast cancer tissues. Our previous study shows that interaction between PR-PPD and Grb2 could interfere with cytoplasmic signaling and lead to inhibition of EGF-mediated signaling. GST-pulldown analysis shows that PR-PPD specifically interacts with the SH3 domains of Grb2. Immunofluorescence staining shows colocalization of PR and Grb2 in both the nucleus and cytoplasm in BT-474 breast cancer cells. Using Bimolecular Fluorescence Complementation (BiFC) analysis, we show that PR and Grb2 interact in breast cancer cells through the Grb2-SH3 domain. Proximity Ligation Assay (PLA) analysis of 43 breast cancer specimens shows that PR-Grb2 interaction is associated with low histological stage and negatively correlates with lymph node invasion and metastasis in breast cancer. These results, together with our previous findings, suggest that PR-PPD interaction with Grb2 plays an essential role in PR-mediated growth factor signaling inhibition and could contribute significantly to better prognosis in PR- and Grb2-positive breast cancer. Our finding provides a basis for additional studies to explore a novel therapeutic strategy for cancer treatment.

Altered hormone expression induced genetic changes leads to breast cancer

PURPOSE OF REVIEW

Breast cancer ranks first among gynecological cancer in India. It is associated with urbanization, changes in lifestyle and obesity. Hormones also play a crucial role in the development of breast cancer. Steroid hormones play critical role in development of breast cancer.

RECENT FINDING

Breast cancer is caused due to alteration in different hormone expressions leading to genetic instability. Loss or gains of functions due to genetic instability were associated with the alterations in housekeeping genes. Up-regulation in c-myc, signal transducer and activator of transcription (STAT), CREB-regulated transcription coactivator (CRTC), and eukaryotic translation initiation factor 4E (eIF4E) may cause the development of breast cancer. Peptide hormones are commonly following the phosphoinositide 3-kinases (PI3K) pathway for activation of cell cycle causing uncontrolled proliferation. Although steroid hormones are following the Ras/Raf/mitogen-activated protein kinase (MEK) pathway, their hyper-activation of these pathways causes extracellular-signal-regulated kinase (ERK) and MAPK activation, leading to carcinogenesis.

SUMMARY

Alteration in cell cycle proteins, oncogenes, tumor suppressor genes, transcription and translation factors lead to breast cancer. Apoptosis plays a vital role in the elimination of abnormal cells but failure in any of these apoptotic pathways may cause tumorigenesis. Hence, a complex interplay of hormonal and genetic factors is required to maintain homeostasis in breast cells. Imbalance in homeostasis of these hormone and genes may lead to breast cancer.

Visualization of breast cancer-related protein synthesis from the perspective of bibliometric analysis

Breast cancer, as a daunting global health threat, has driven an exponential growth in related research activity in recent decades. An area of research of paramount importance is protein synthesis, and the analysis of specific proteins inextricably linked to breast cancer. In this article, we undertake a bibliometric analysis of the literature on breast cancer and protein synthesis, aiming to provide crucial insights into this esoteric realm of investigation. Our approach was to scour the Web of Science database, between 2003 and 2022, for articles containing the keywords "breast cancer" and "protein synthesis" in their title, abstract, or keywords. We deployed bibliometric analysis software, exploring a range of measures such as publication output, citation counts, co-citation analysis, and keyword analysis. Our search yielded 2998 articles that met our inclusion criteria. The number of publications in this area has steadily increased, with a significant rise observed after 2003. Most of the articles were published in oncology or biology-related journals, with the most publications in Journal of Biological Chemistry, Cancer Research, Proceedings of the National Academy of Sciences of the United States of America, and Oncogene. Keyword analysis revealed that "breast cancer," "expression," "cancer," "protein," and "translation" were the most commonly researched topics. In conclusion, our bibliometric analysis of breast cancer and related protein synthesis literature underscores the burgeoning interest in this research. The focus of the research is primarily on the relationship between protein expression in breast cancer and the development and treatment of tumors. These studies have been instrumental in the diagnosis and treatment of breast cancer. Sustained research in this area will yield essential insights into the biology of breast cancer and the genesis of cutting-edge therapies.

Targeting Breast Cancer: The Familiar, the Emerging, and the Uncharted Territories

Breast cancer became the most diagnosed cancer in the world in 2020. Chemotherapy is still the leading clinical strategy in breast cancer treatment, followed by hormone therapy (mostly used in hormone receptor-positive types). However, with our ever-expanding knowledge of signaling pathways in cancer biology, new molecular targets are identified for potential novel molecularly targeted drugs in breast cancer treatment. While this has resulted in the approval of a few molecularly targeted drugs by the FDA (including drugs targeting immune checkpoints), a wide array of signaling pathways seem to be still underexplored. Also, while combinatorial treatments have become common practice in clinics, the majority of these approaches seem to combine molecularly targeted drugs with chemotherapeutic agents. In this manuscript, we start by analyzing the list of FDA-approved molecularly targeted drugs for breast cancer to evaluate where molecular targeting stands in breast cancer treatment today. We will then provide an overview of other options currently under clinical trial or being investigated in pre-clinical studies.

Clinicopathological characteristics and features of molecular subtypes of breast cancer at high altitudes

Background

Breast cancer is one of the major malignancies threatening women's health worldwide. The incidence of breast cancer at high altitudes increased over the years. But few studies focused on the characteristics of clinicopathology and molecular subtypes among breast cancer at high altitudes, which are still unknown. Tibet, with an average altitude over 4000 meters, is a representative city at high altitudes, lying in the Qinghai-Tibetan Plateau in southwestern China. This study aimed to identify the clinicopathological characteristics and features of molecular subtypes among Tibetan women with breast cancer, and provide evidence for cancer prevention and personalized therapeutics in high-altitude regions.

Methods

Between May 2013 and March 2022, 104 Tibetan women from high-altitude regions (Tibetan-group) and 34 Han Chinese women from low-altitude regions (Han-group), consecutively diagnosed with breast cancer in the Hospital of Chengdu Office of People's Government of Tibetan Autonomous Region, were included in the study. We retrospectively reviewed the clinical character, altitudes of residence, tumor size, lymph nodes metastasis, distant metastasis, pathological type, immunohistochemical index, and molecular subtype.

Results

In the study, we calculated the patient delay, equal to the period from symptoms onset to hospital visits. The patient delay of Tibetan-group was 7.47 ± 11.53 months, which was significantly longer than that of Han-group, 7.22 ± 22.96 months (p<0.05). Body Mass Index (BMI) was significantly different (p<0.05). Tumors in Tibetan-group were significantly larger than those in Han-group, 4.13 ± 2.98cm and 2.51 ± 0.82cm in diameter, respectively (p<0.05). According to ordinal logistic regression analysis, exposure to high altitudes might result in more advanced T stage (OR=2.45 95%CI 1.10-5.44). 41.3% (43/104) of cases in Tibetan-group had lymph node positive disease, whereas the percentage was found in 38.26% (13/34) in Han-group(p<0.05). The distribution of molecular subtypes was quite significantly different between two groups (p<0.05), according to the comparison of constituent ratios.

Conclusion

Our study verified that breast cancer at high altitudes possessed its own unique clinicopathological characteristics and distinct features of molecular subtypes. It broadened the understanding of this heterogenous disease and also provided valuable evidence for cancer prevention and personalized therapeutics of breast cancer at high altitudes.

Estrogen Receptor Signaling in the Immune System

The immune system functions in a sexually dimorphic manner, with females exhibiting more robust immune responses than males. However, how female sex hormones affect immune function in normal homeostasis and in autoimmunity is poorly understood. In this review, we discuss how estrogens affect innate and adaptive immune cell activity and how dysregulation of estrogen signaling underlies the pathobiology of some autoimmune diseases and cancers. The potential roles of the major circulating estrogens, and each of the 3 estrogen receptors (ERα, ERβ, and G-protein coupled receptor) in the regulation of the activity of different immune cells are considered. This provides the framework for a discussion of the impact of ER modulators (aromatase inhibitors, selective estrogen receptor modulators, and selective estrogen receptor downregulators) on immunity. Synthesis of this information is timely given the considerable interest of late in defining the mechanistic basis of sex-biased responses/outcomes in patients with different cancers treated with immune checkpoint blockade. It will also be instructive with respect to the further development of ER modulators that modulate immunity in a therapeutically useful manner.

Impacts of COVID-19 in Breast Cancer: From Molecular Mechanism to the Treatment Approach

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has already infected more than 272 million people, resulting in 5.3 million deaths worldwide from COVID-19. Breast tumors are considered the world's most commonly diagnosed cancer. Both breast cancer and COVID-19 share common pathogenic features, represented by inflammatory mediators and the potential of SARS-CoV-2 replication in metastatic cancer cells. This may intensify viral load in patients, thereby triggering severe COVID-19 complications. Thus, cancer patients have a high risk of developing severe COVID-19 with SARS-CoV-2 infection and a higher rate of complications and death than non-cancer patients. The present review discusses common mechanisms between COVID-19 and breast cancer and the particular susceptibility to COVID-19 in breast cancer patients. We describe the effects of chemotherapeutic agents that are used against this cancer, which should be considered from the perspective of susceptibility to SARS-CoV-2 infection and risk of developing severe events. We also present potential drug interactions between chemotherapies that are used to treat breast cancer and drugs that are applied for COVID-19. The drugs that are identified as having the most interactions are doxorubicin and azithromycin. Both drugs can interact with each other and with other drugs, which likely requires additional drug monitoring and changes in drug dosage and timing of administration. Further clinical and observational studies involving breast cancer patients who acquire COVID-19 are needed to define the best therapeutic approach when considering the course of both diseases.

Giredestrant reverses progesterone hypersensitivity driven by estrogen receptor mutations in breast cancer

ESR1 (estrogen receptor 1) hotspot mutations are major contributors to therapeutic resistance in estrogen receptor-positive (ER⁺) breast cancer. Such mutations confer estrogen independence to ERα, providing a selective advantage in the presence of estrogen-depleting aromatase inhibitors. In addition, ESR1 mutations reduce the potency of tamoxifen and fulvestrant, therapies that bind ERα directly. These limitations, together with additional liabilities, inspired the development of the next generation of ERα-targeted therapeutics, of which giredestrant is a high-potential candidate. Here, we generated Esr1 mutant-expressing mammary gland models and leveraged patient-derived xenografts (PDXs) to investigate the biological properties of the ESR1 mutations and their sensitivity to giredestrant in vivo. In the mouse mammary gland, Esr1 mutations promote hypersensitivity to progesterone, triggering pregnancy-like tissue remodeling and profoundly elevated proliferation. These effects were driven by an altered progesterone transcriptional response and underpinned by gained sites of ERα-PR (progesterone receptor) cobinding at the promoter regions of pro-proliferation genes. PDX experiments showed that the mutant ERα-PR proliferative program is also relevant in human cancer cells. Giredestrant suppressed the mutant ERα-PR proliferation in the mammary gland more so than the standard-of-care agents, tamoxifen and fulvestrant. Giredestrant was also efficacious against the progesterone-stimulated growth of ESR1 mutant PDX models. In addition, giredestrant demonstrated activity against a molecularly characterized ESR1 mutant tumor from a patient enrolled in a phase 1 clinical trial. Together, these data suggest that mutant ERα can collaborate with PR to drive protumorigenic proliferation but remain sensitive to inhibition by giredestrant.

A high-throughput drug screen reveals means to differentiate triple-negative breast cancer

Plasticity delineates cancer subtypes with more or less favourable outcomes. In breast cancer, the subtype triple-negative lacks expression of major differentiation markers, e.g., estrogen receptor α (ERα), and its high cellular plasticity results in greater aggressiveness and poorer prognosis than other subtypes. Whether plasticity itself represents a potential vulnerability of cancer cells is not clear. However, we show here that cancer cell plasticity can be exploited to differentiate triple-negative breast cancer (TNBC). Using a high-throughput imaging-based reporter drug screen with 9 501 compounds, we have identified three polo-like kinase 1 (PLK1) inhibitors as major inducers of ERα protein expression and downstream activity in TNBC cells. PLK1 inhibition upregulates a cell differentiation program characterized by increased DNA damage, mitotic arrest, and ultimately cell death. Furthermore, cells surviving PLK1 inhibition have decreased tumorigenic potential, and targeting PLK1 in already established tumours reduces tumour growth both in cell line- and patient-derived xenograft models. In addition, the upregulation of genes upon PLK1 inhibition correlates with their expression in normal breast tissue and with better overall survival in breast cancer patients. Our results indicate that differentiation therapy based on PLK1 inhibition is a potential alternative strategy to treat TNBC.

Gold(I)-Catalyzed Synthesis of 4H-Benzo[d][1,3]oxazines and Biological Evaluation of Activity in Breast Cancer Cells

The first gold(I)-catalyzed cycloisomerization procedure applied to the synthesis of substituted 4H-benzo[d][1,3]oxazines has been developed starting from N-(2-alkynyl)aryl benzamides. The chemoselective oxygen cyclization via the 6-exo-dig pathway yielded the observed heterocycles in modest to good chemical yields under very mild reaction conditions. The obtained oxazines were assayed on the breast cancer (BC)-derived cell lines MCF-7 and HCC1954 with differential biological activity. The newly synthesized 4H-benzo[d][1,3]oxazine compounds showed several degrees of cell proliferation inhibition with a remarkable effect for those compounds having a substituted aryl at C-2 of the molecules. The 4H-benzo[d][1,3]oxazines showed an IC₅₀ ranking from 3.1 to 95 μM in MCF-7 and HCC1954 cells. These compounds represent potential drug candidates for BC treatment. However, additional assays are needed to elucidate their complete effect over the cellular and molecular hallmarks of cancer.

Choosing the right partner in hormone-dependent gene regulation: Glucocorticoid and progesterone receptors crosstalk in breast cancer cells

Steroid hormone receptors (SHRs) belong to a large family of ligand-activated nuclear receptors that share certain characteristics and possess others that make them unique. It was thought for many years that the specificity of hormone response lay in the ligand. Although this may be true for pure agonists, the natural ligands as progesterone, corticosterone and cortisol present a broader effect by simultaneous activation of several SHRs. Moreover, SHRs share structural and functional characteristics that range from similarities between ligand-binding pockets to recognition of specific DNA sequences. These properties are clearly evident in progesterone (PR) and glucocorticoid receptors (GR); however, the biological responses triggered by each receptor in the presence of its ligand are different, and in some cases, even opposite. Thus, what confers the specificity of response to a given receptor is a long-standing topic of discussion that has not yet been unveiled. The levels of expression of each receptor, the differential interaction with coregulators, the chromatin accessibility as well as the DNA sequence of the target regions in the genome, are reliable sources of variability in hormone action that could explain the results obtained so far. Yet, to add further complexity to this scenario, it has been described that receptors can form heterocomplexes which can either compromise or potentiate the respective hormone-activated pathways with its possible impact on the pathological condition. In the present review, we summarized the state of the art of the functional cross-talk between PR and GR in breast cancer cells and we also discussed new paradigms of specificity in hormone action.

Estetrol and Mammary Gland: Friends or Foes?

Estrogens have pleiotropic effects on many reproductive and non-reproductive tissues and organs including the mammary gland, uterus, ovaries, vagina, and endothelium. Estrogen receptor α functions as the principal mediator of estrogenic action in most of these tissues. Estetrol (E4) is a native fetal estrogen with selective tissue actions that is currently approved for use as the estrogen component in a combined oral contraceptive and is being developed as a menopause hormone therapy (MHT, also known as hormone replacement therapy). However, exogenous hormonal treatments, in particular MHTs, have been shown to promote the growth of preexisting breast cancers and are associated with a variable risk of breast cancer depending on the treatment modality. Therefore, evaluating the safety of E4-based formulations on the breast forms a crucial part of the clinical development process. This review highlights preclinical and clinical studies that have assessed the effects of E4 and E4-progestogen combinations on the mammary gland and breast cancer, focusing in particular on the estrogenic and anti-estrogenic properties of E4. We discuss the potential advantages of E4 over current available estrogen-formulations as a contraceptive and for the treatment of symptoms due to menopause. We also consider the potential of E4 for the treatment of endocrine-resistant breast cancer.

Laminin alpha 5 regulates mammary gland remodeling through luminal cell differentiation and Wnt4-mediated epithelial crosstalk

Epithelial attachment to the basement membrane (BM) is essential for mammary gland development, yet the exact roles of specific BM components remain unclear. Here, we show that Laminin α5 (Lama5) expression specifically in the luminal epithelial cells is necessary for normal mammary gland growth during puberty, and for alveologenesis during pregnancy. Lama5 loss in the keratin 8-expressing cells results in reduced frequency and differentiation of hormone receptor expressing (HR⁺) luminal cells. Consequently, Wnt4-mediated crosstalk between HR⁺ luminal cells and basal epithelial cells is compromised during gland remodeling, and results in defective epithelial growth. The effects of Lama5 deletion on gland growth and branching can be rescued by Wnt4 supplementation in the in vitro model of branching morphogenesis. Our results reveal a surprising role for BM-protein expression in the luminal mammary epithelial cells, and highlight the function of Lama5 in mammary gland remodeling and luminal differentiation.

Summary: Luminal mammary epithelial cells produce basement membrane laminin α5 necessary for mammary epithelial growth and differentiation. Laminin α5 loss compromises hormone receptor-positive luminal cell function and Wnt4-mediated crosstalk between epithelial cells.

Deciphering the signaling network of breast cancer improves drug sensitivity prediction

One goal of precision medicine is to tailor effective treatments to patients' specific molecular markers of disease. Here, we used mass cytometry to characterize the single-cell signaling landscapes of 62 breast cancer cell lines and five lines from healthy tissue. We quantified 34 markers in each cell line upon stimulation by the growth factor EGF in the presence or absence of five kinase inhibitors. These data-on more than 80 million single cells from 4,000 conditions-were used to fit mechanistic signaling network models that provide insight into how cancer cells process information. Our dynamic single-cell-based models accurately predicted drug sensitivity and identified genomic features associated with drug sensitivity, including a missense mutation in DDIT3 predictive of PI3K-inhibition sensitivity. We observed similar trends in genotype-drug sensitivity associations in patient-derived xenograft mouse models. This work provides proof of principle that patient-specific single-cell measurements and modeling could inform effective precision medicine strategies.

Steroid Hormone Receptors: Links With Cell Cycle Machinery and Breast Cancer Progression

Progression of cells through cell cycle consists of a series of events orchestrated in a regulated fashion. Such processes are influenced by cell cycle regulated expression of various proteins where multiple families of transcription factors take integral parts. Among these, the steroid hormone receptors (SHRs) represent a connection between the external hormone milieu and genes that control cellular proliferation. Therefore, understanding the molecular connection between the transcriptional role of steroid hormone receptors and cell cycle deserves importance in dissecting cellular proliferation in normal as well as malignant conditions. Deregulation of cell cycle promotes malignancies of various origins, including breast cancer. Indeed, SHR members play crucial role in breast cancer progression as well as management. This review focuses on SHR-driven cell cycle regulation and moving forward, attempts to discuss the role of SHR-driven crosstalk between cell cycle anomalies and breast cancer.

The impact of oral contraceptive use on breast cancer risk: State of the art and future perspectives in the era of 4P medicine

Breast cancer is the most commonly occurring cancer in women, the second most frequent cancer overall, and it causes the greatest number of cancer-related deaths among women. The significant increased concern of breast cancer worldwide may be attributed to the prolonged life expectancy and the adoption of the western lifestyle with its related risks factors. A woman's risk for breast cancer is linked to her reproductive history and with her lifetime hormonal exposure. Among the known risk factors for breast cancer, several studies investigated the possible role of the assumption of hormonal "pills" in both breast cancer incidence and development. Nevertheless, data about the association between the assumption of oral contraceptives and breast cancer incidence are still controversial and not conclusive. Given the public health importance of breast cancer and the popularity of hormonal "pills" as contraceptive, the impact of oral contraceptive use on breast cancer risk assumes relevance from both a clinical and a social point of view. Therefore, in this review we wanted to illustrate this issue by addressing the following major themes: a) the role of sex steroid hormones in female breast development and carcinogenesis; b) the clinical impact of hormonal oral contraception according to the state of the art literature; c) the actual scientific debate and future perspectives.

Essential Oils and Health

Essential oils (EOs) have risen in popularity over the past decade. These oils function in society as holistic integrative modalities to traditional medicinal treatments, where many Americans substitute EOs in place of other prescribed medications. EOs are found in a multitude of products including food flavoring, soaps, lotions, shampoos, hair styling products, cologne, laundry detergents, and even insect repellents. EOs are complex substances comprised of hundreds of components that can vary greatly in their composition depending upon the extraction process by the producer or the origin of the plant. Thus, making it difficult to determine which pathways in the body are affected. Here, we review the published research that shows the health benefits of EOs as well as some of their adverse effects. In doing so, we show that EOs, as well as some of their individual components, possess antimicrobial, antiviral, antibiotic, anti-inflammatory, and antioxidant properties as well as purported psychogenic effects such as relieving stress, treating depression, and aiding with insomnia. Not only do we show the health benefits of using EOs, but we also indicate risks associated with their use such as their endocrine disrupting properties leading to the induction of premature breast growth in young adolescents. Taken together, there are many positive and potentially negative risks to human health associated with EOs, which make it important to bring awareness to all their known effects on the human body.

Steroid hormones regulate genome-wide epigenetic programming and gene transcription in human endometrial cells with marked aberrancies in endometriosis

Programmed cellular responses to cycling ovarian-derived steroid hormones are central to normal endometrial function. Abnormalities therein, as in the estrogen-dependent, progesterone-"resistant" disorder, endometriosis, predispose to infertility and poor pregnancy outcomes. The endometrial stromal fibroblast (eSF) is a master regulator of pregnancy success. However, the complex hormone-epigenome-transcriptome interplay in eSF by each individual steroid hormone, estradiol (E2) and/or progesterone (P4), under physiologic and pathophysiologic conditions, is poorly understood and was investigated herein. Genome-wide analysis in normal, early and late stage eutopic eSF revealed: i) In contrast to P4, E2 extensively affected the eSF DNA methylome and transcriptome. Importantly, E2 resulted in a more open versus closed chromatin, confirmed by histone modification analysis. Combined E2 with P4 affected a totally different landscape than E2 or P4 alone. ii) P4 responses were aberrant in early and late stage endometriosis, and mapping differentially methylated CpG sites with progesterone receptor targets from the literature revealed different but not decreased P4-targets, leading to question the P4-"resistant" phenotype in endometriosis. Interestingly, an aberrant E2-response was noted in eSF from endometriosis women; iii) Steroid hormones affected specific genomic contexts and locations, significantly enriching enhancers and intergenic regions and minimally involving proximal promoters and CpG islands, regardless of hormone type and eSF disease state. iv) In eSF from women with endometriosis, aberrant hormone-induced methylation signatures were mainly due to existing DNA methylation marks prior to hormone treatments and involved known endometriosis genes and pathways. v) Distinct DNA methylation and transcriptomic signatures revealed early and late stage endometriosis comprise unique disease subtypes. Taken together, the data herein, for the first time, provide significant insight into the hormone-epigenome-transcriptome interplay of each steroid hormone in normal eSF, and aberrant E2 response, distinct disease subtypes, and pre-existing epigenetic aberrancies in the setting of endometriosis, provide mechanistic insights into how endometriosis affects endometrial function/dysfunction.

The RNA binding protein CPEB2 regulates hormone sensing in mammary gland development and luminal breast cancer

Organogenesis is directed by coordinated cell proliferation and differentiation programs. The hierarchical networks of transcription factors driving mammary gland development and function have been widely studied. However, the contribution of posttranscriptional gene expression reprogramming remains largely unexplored. The 3' untranslated regions of messenger RNAs (mRNAs) contain combinatorial ensembles of cis-regulatory elements that define transcript-specific regulation of protein synthesis through their cognate RNA binding proteins. We analyze the contribution of the RNA binding cytoplasmic polyadenylation element-binding (CPEB) protein family, which collectively regulate mRNA translation for about 30% of the genome. We find that CPEB2 is required for the integration of hormonal signaling by controlling the protein expression from a subset of ER/PR- regulated transcripts. Furthermore, CPEB2 is critical for the development of ER-positive breast tumors. This work uncovers a previously unknown gene expression regulation level in breast morphogenesis and tumorigenesis, coordinating sequential transcriptional and posttranscriptional layers of gene expression regulation.

Lavender Products Associated With Premature Thelarche and Prepubertal Gynecomastia: Case Reports and Endocrine-Disrupting Chemical Activities

CONTEXT

Previous case reports associated prepubertal gynecomastia with lavender-containing fragrances, but there appear to be no reports of premature thelarche.

OBJECTIVE

To add to a case series about lavender-fragranced product use and breast growth in children and to measure endocrine-disrupting chemical activity of essential oil components.

DESIGN, SETTING, AND PATIENTS

Patients experiencing premature thelarche or prepubertal gynecomastia with continuous exposure to lavender-fragranced products were evaluated in the pediatric endocrinology departments of two institutions. Mechanistic in vitro experiments using eight components of lavender and other essential oils were performed at National Institute of Environmental Health Sciences.

MAIN OUTCOME MEASURES

Case reports and in vitro estrogen and androgen receptor gene expression activities in human cell lines with essential oils.

RESULTS

Three prepubertal girls and one boy with clinical evidence of estrogenic action and a history of continuous exposure to lavender-containing fragrances were studied. Breast growth dissipated in all patients with discontinuation of the fragranced products. Some of the components tested elicited estrogenic and antiandrogenic properties of varying degrees.

CONCLUSION

We report cases of premature thelarche that resolved upon cessation of lavender-containing fragrance exposure commonly used in Hispanic communities. The precise developmental basis for such conditions could be multifactorial. In vitro demonstration of estrogenic and antiandrogenic properties of essential oil components suggests essential oils in these cases could be considered a possible source and supports a possible link with idiopathic prepubertal breast development. Whether the level of lavender oil estrogenic potency is sufficient to cause these effects is unknown.

The effects of bisphenol A, benzyl butyl phthalate, and di(2-ethylhexyl) phthalate on estrogen receptor alpha in estrogen receptor-positive cells under hypoxia

Endocrine-disrupting chemicals (EDCs) are widely used in various consumer goods. Consequently, humans are constantly exposed to EDCs, which is associated with a variety of endocrine-related diseases. In this study, we demonstrated the effects of bisphenol A (BPA), benzyl butyl phthalate (BBP), and di(2-ethylhexyl) phthalate (DEHP) on estrogen receptor alpha (ERα) expression under normoxia and hypoxia. First, we confirmed the effects of EDCs on ER activity using OECD Test Guideline 455. Compared to the 100% activity induced by 1 nM 17-β-estradiol (positive control), BPA and BBP exhibited 50% ERα activation at concentrations of 1.31 μM and 4.8 μM, respectively. In contrast, and consistent with previous reports, DEHP did not activate ERα. ERα is activated and degraded by hypoxia in breast cancer cells. BPA, BBP, and DEHP enhanced ERα-mediated transcriptional activity under hypoxia. All three EDCs decreased ERα protein levels under hypoxia in MCF-7 cells. The transcriptional activity of hypoxia-inducible factor-1 was decreased and secretion of vascular endothelial growth factor (VEGF) was increased by BPA and BBP under hypoxia in MCF-7 cells, but not by DEHP. All three EDCs decreased the ERα protein expression level in Ishikawa human endometrial adenocarcinoma cells, and DEHP caused a weak decrease in VEGF secretion under hypoxia. These results demonstrate down-regulation of ERα by EDCs may influence the pathological state associated with hypoxia.

Zfhx3 is essential for progesterone/progesterone receptor signaling to drive ductal side-branching and alveologenesis in mouse mammary glands

Progesterone (Pg)/progesterone receptor (PR) signaling drives mammary gland side-branching and alveologenesis, but the mechanisms through which Pg/PR signaling functions remain to be clarified. Using in vitro and in vivo models and histological and molecular analyses, we determined the role of Zfhx3 transcription factor in mammary gland development driven by Pg/PR signaling. Postnatal deletion of Zfhx3 in mouse mammary epithelial cells attenuated side-branching morphogenesis and alveologenesis. These effects were undetectable in the absence of Pg/PR signaling. During the estrus cycle, Zfhx3 expression corresponded to that of Pg, being at the highest level at the diestrus stage; Zfhx3 deletion inhibited mammary gland branching more potently at diestrus than estrus stage. Loss of Zfhx3 not only attenuated the expansion of stem/progenitor cells driven by Pg/PR signaling, but also impaired the function of Pg/PR signaling in the transcriptional activation of multiple genes. In addition, Pg/PR signaling significantly expanded PR- and Zfhx3-positive epithelial cells, and induced the physical association of ZFHX3 with PR. These findings establish Zfhx3 as an integral transcription factor of Pg/PR signaling in driving side-branching and alveologenesis during mammary gland development.

Involvement of sex hormonal regulation of K+ channels in electrophysiological and contractile functions of muscle tissues

Sex hormones, such as testosterone, progesterone, and 17β-estradiol, control various physiological functions. This review focuses on the sex hormonal regulation of K⁺ channels and the effects of such regulation on electrophysiological and contractile functions of muscles. In the cardiac tissue, testosterone and progesterone shorten action potential, and estrogen lengthens QT interval, a marker of increased risk of ventricular tachyarrhythmias. We have shown that testosterone and progesterone in physiological concentration activate KCNQ1 channels via membrane-delimited sex hormone receptor/eNOS pathways to shorten the action potential duration. Mitochondrial K⁺ channels are also involved in the protection of cardiac muscle. Testosterone and 17β-estradiol directly activate mitochondrial inner membrane K⁺ channels (Ca²⁺ activated K⁺ channel (K_Ca channel) and ATP-sensitive K⁺ channel (K_ATP channel)) that are involved in ischemic preconditioning and cardiac protection. During pregnancy, uterine blood flow increases to support fetal growth and development. It has been reported that 17β-estradiol directly activates large-conductance Ca²⁺-activated K⁺ channel (BK_Ca channel) attenuating arterial contraction. Furthermore, 17β-estradiol increases expression of BK_Ca channel β1 subunit which enhances BK_Ca channel activity by DNA demethylation. These findings are useful for understanding the mechanisms of sex or generation-dependent differences in the physiological and pathological functions of muscles, and the mechanisms of drug actions.

The Tumor Microenvironment as a Regulator of Endocrine Resistance in Breast Cancer

Estrogen receptor positive breast neoplasias represent over 70% of diagnosed breast cancers. Depending on the stage at which the tumor is detected, HER2 status and genomic risk, endocrine therapy is combined with either radio, chemo and/or targeted therapy. A growing amount of evidence supports the notion that components of the tumor microenvironment play specific roles in response to treatment and that strategies targeting these key interactions with tumor cells could pave the way to a new generation of therapies. In this review, we analyze the evidence suggesting different components of the tumor microenvironment play a role in hormone receptor positive breast cancer progression. In particular we focus on the immune system, carcinoma associated fibroblasts and the extracellular matrix. Further insight into the cross talk between these constituents of the microenvironment and the tumor cells may lead to therapies that eliminate disseminated metastatic cells early on, and thus reduce distant disease relapse which is the leading cause of death for patients who are diagnosed with this illness.

Molecular mechanisms of the action of Arctigenin in cancer

Since antediluvian times, the scientific community has realized that natural compounds exhibit enormous potential for the treatment of terrible diseases, such as cancer. Despite a variety of effective bioactive molecules, effective therapies still need to be developed to treat cancer. Hence, it is necessary to study the interactions of natural molecules with their cellular targets. Arctigenin (ATG), a natural lignan compound extracted from Arctium lappa, inhibits the growth of various cancer cells, such as those of the stomach, lungs, liver, and colon, as well as leukocytes, and regulates numerous intracellular activities, such as antioxidative, anti-inflammatory, and anticancer activities. The intention of this paper is to summarize and generally analyse the molecular pathways that are involved in the anticancer effects of ATG. In addition, the interactions of ATG with other drugs are also highlighted in this paper.

Genome Wide Identification of Novel Long Non-coding RNAs and Their Potential Associations With Milk Proteins in Chinese Holstein Cows

Long non-coding RNAs (lncRNAs) have emerged as a novel class of regulatory molecules involved in various biological processes. However, their role in milk performance is unknown. Here, whole transcriptome RNA sequencing was used to generate the lncRNA transcriptome profiles in mammary tissue samples from 6 Chinese Holstein cows with 3 extremely high and 3 low milk protein percentage phenotypes. In this study, 6,450 lncRNA transcripts were identified through 5 stringent steps and filtration by coding potential. In total, 31 lncRNAs and 18 novel genes were identified to be differentially expressed in high milk protein samples (HP) relative to low milk protein samples (LP), respectively. Differentially expressed lncRNAs were selected to predict target genes through bioinformatics analysis, followed by the integration of differentially expressed mRNA data, gene function, gene ontology (GO) and pathway, genome wide association study (GWAS) and quantitative trait locus (QTL) information, as well as network analysis to further characterize potential interactions. Several lncRNAs were found (such as XLOC_059976) that could be used as candidate markers for milk protein content prediction. This is the first study to perform global expression profiling of lncRNAs and mRNAs related to milk protein traits in dairy cows. These results provide important information and insights into the synthesis of milk proteins, and potential targets for the future improvement of milk quality.

Prolactin Alters the Mammary Epithelial Hierarchy, Increasing Progenitors and Facilitating Ovarian Steroid Action

Hormones drive mammary development and function and play critical roles in breast cancer. Epidemiologic studies link prolactin (PRL) to increased risk for aggressive cancers that express estrogen receptor α (ERα). However, in contrast to ovarian steroids, PRL actions on the mammary gland outside of pregnancy are poorly understood. We employed the transgenic NRL-PRL model to examine the effects of PRL alone and with defined estrogen/progesterone exposure on stem/progenitor activity and regulatory networks that drive epithelial differentiation. PRL increased progenitors and modulated transcriptional programs, even without ovarian steroids, and with steroids further raised stem cell activity associated with elevated canonical Wnt signaling. However, despite facilitating some steroid actions, PRL opposed steroid-driven luminal maturation and increased CD61⁺ luminal cells. Our findings demonstrate that PRL can powerfully influence the epithelial hierarchy alone and temper the actions of ovarian steroids, which may underlie its role in the development of breast cancer.

Mechanisms of modulation of the Egr gene family in mammary epithelial cells of different species

In the adult female, within the estrous cycle, the mammary gland undergoes multiple rounds of growth, with increased cellular proliferation, and involution, with increased apoptosis. The increase in proliferation is elicited by endocrine (Estrogen, Progesterone), as well as locally produced (epidermal growth factor, insulin-like growth factor, etc) growth factors. Among the genes that are modulated during cellular proliferation, immediate early genes play a fundamental role, being rapidly upregulated and then downregulated within the G0/G1 phase of the cell cycle, allowing the progression to the subsequent phases. Egrs (1-4) are immediate early genes that encode for transcription factors that promote, within different cell types and depending on the strength and duration of the stimuli, several different responses like mitogenesis, differentiation, apoptosis or even anti-apoptosis. In this work we have studied the mechanisms of modulation of the Egr family, in mammary epithelial cells of different origin (bovine, canine, feline, murine). Following stimulation with growth medium, Egr mRNA expression showed a strong upregulation reaching a peak at 45-60min, that rapidly declined. Among several cytokines, particularly important for mammary morphogenesis, that we have tested (EGF, IGF-I, insulin, estrogen, progesterone), only EGF upregulated Egrs to levels close to those elicited by growth medium. In order to understand how the Egr transcription factors were regulated, we have inhibited Erk 1/2 and PI3K, molecules that drive two major intracellular signaling pathways. Inhibition of the Erk 1/2 pathway totally abolished Egr upregulation mediated by growth medium or EGF. On the other hand, the PI3K-Akt pathway played a minor role on Egr levels, with a strong inhibitory effect on cat GH2 cells only, that could be ascribed to reduced Erk phosphorylation following PI3K inhibition. Finally we showed that addition of growth medium also upregulated that the mammary luminal marker cytokeratin 18, but only in the murine NMuMG cell line. This is the first manuscript describing how the Egr transcription factors are expressed in mammary epithelial cells of domestic animals and which growth factors and signaling pathways modulate their expression.

Overexpression of lipid metabolism genes and PBX1 in the contralateral breasts of women with estrogen receptor-negative breast cancer

Risk biomarkers for estrogen receptor (ER)-negative breast cancer have clear value for breast cancer prevention. We previously reported a set of lipid metabolism (LiMe) genes with high expression in the contralateral unaffected breasts (CUBs) of ER-negative cancer cases. We now further examine LiMe gene expression in both tumor and CUB, and investigate the role of Pre-B-cell leukemia homeobox-1 (PBX1) as a candidate common transcription factor for LiMe gene expression. mRNA was extracted from laser-capture microdissected epithelium from tumor and CUB of 84 subjects (28 ER-positive cases, 28 ER-negative cases, 28 healthy controls). Gene expression was quantitated by qRT-PCR. Logistic regression models were generated to predict ER status of the contralateral cancer. Protein expression of HMGCS2 and PBX1 was measured using immunohistochemistry. The effect of PBX1 on LiMe gene expression was examined by overexpressing PBX1 in MCF10A cells with or without ER, and by suppressing PBX1 in MDA-MB-453 cells. The expression of DHRS2, HMGCS2, UGT2B7, UGT2B11, ALOX15B, HPGD, UGT2B28 and GLYATL1 was significantly higher in ER-negative versus ER-positive CUBs, and predicted ER status of the tumor in test and validation sets. In contrast, LiMe gene expression was significantly lower in ER-negative than ER-positive tumors. PBX1 overexpression in MCF10A cells up-regulated most LiMe genes, but not in MCF10A cells overexpressing ER. Suppressing PBX1 in MDA-MB-453 cells resulted in decrease of LiMe gene expression. Four binding sites of PBX1 and cofactor were identified in three lipid metabolism genes using ChIP-qPCR. These data suggest a novel role for PBX1 in the regulation of lipid metabolism genes in benign breast, which may contribute to ER-negative tumorigenesis.

After genome-wide association studies: Gene networks elucidating candidate genes divergences for number of teats across two pig populations

Number of teats (NT) is an important trait affecting both piglet's welfare and the production level of pig farms. Biologically, embryonic mammary gland development requires the coordination of many signaling pathways necessary for the proper development of teats. Several QTL for NT have been identified; however, further analysis is still lacking. Therefore, gene networks derived from genomewide association study (GWAS) results can be used to examine shared pathways and functions of putative candidate genes. Besides, such analyses may also be helpful to understand the genetic diversity between populations for the same trait or traits. In this study, we identified significant SNP for Landrace-based (line C) and Large White-based (line D) dam lines. Besides, gene-transcription factor (TF) networks were constructed aiming to obtain the most likely candidate genes for NT in each line followed by a comparative analysis between both lines to access similarities or dissimilarities at the marker and gene level. We identified 24 and 19 significant SNP (Bayes factor ≥ 100) for lines C and D, respectively. Only 1 significant SNP overlapped both lines. Network analysis illustrated gene interactions consistent with known mammal's breast biology and captured known TF. We observed different sets of putative candidate genes for NT in each line evaluated that may have common effects on the phenotype. Based on these results, we demonstrated the importance of post-GWAS analyses increasing the biological understanding of relevant genes for a complex trait. Moreover, we believe that this genomic diversity across lines should be taken into account, considering breed-specific reference populations for genomic selection.

β-Catenin Mediates Anti-adipogenic and Anticancer Effects of Arctigenin in Preadipocytes and Breast Cancer Cells

Arctigenin is a lignan abundant in Asteraceae plants and has anti-inflammatory, antiobesity, and anticancer activities. Obesity is one of the leading causes of several types of cancers including breast cancer. The current study was performed to investigate if arctigenin suppresses differentiation of preadipocytes and proliferation of breast cancer cells and to explore potential molecular mechanisms. Treatment of arctigenin reduced lipid accumulation in differentiated 3T3-L1 adipocytes in a dose- and time-dependent manner without toxicity. Arctigenin suppressed the expression of peroxisome proliferator-activated receptor-gamma (PPARγ), CCAAT/enhancer-binding protein-alpha (C/EBPα), perilipin, and fatty acid binding protein 4 (FABP4) in a dose-dependent manner in differentiated 3T3-L1 cells. Both total and unphosphorylated (active) β-catenin were increased in whole cell lysates and the nuclear fraction of differentiated 3T3-L1 cells treated with 25 μM arctigenin. On the other hand, arctigenin decreased proliferation of two human breast cancer cells (MCF-7 and MDA-MB-231). Arctigenin induced apoptosis and decreased expression of total and unphosphorylated (active) β-catenin and cyclin D1 in MCF-7, but not in MDA-MB-231. These data indicate that arctigenin suppressed adipogenesis in preadipocytes and activated apoptosis in estrogen receptor (ER) positive breast cancer cells through modulating expression of β-catenin.

Alterations in estrogen signalling pathways upon acquisition of anthracycline resistance in breast tumor cells

Intrinsic or acquired drug resistance is a major impediment to the successful treatment of women with breast cancer using chemotherapy. We have observed that MCF-7 breast tumor cells selected for resistance to doxorubicin or epirubicin (MCF-7_DOX2 and MCF-7_EPI cells, respectively) exhibited increased expression of several members of the aldo-keto reductase (AKR) gene family (in particular AKR1C3 and AKR1B10) relative to control MCF-7_CC cells selected by propagation in the absence of drug. Normal cellular roles for the AKRs include the promotion of estrogen (E2) synthesis from estrone (E1) and the hydroxylation and detoxification of exogenous xenobiotics such as anthracycline chemotherapy drugs. While hydroxylation of anthracyclines strongly attenuates their cytotoxicity, it is unclear whether the enhanced AKR expression in the above anthracycline-resistant cells promotes E2 synthesis and/or alterations in E2 signalling pathways and whether such changes contribute to enhanced survival and anthracycline resistance. To determine the role of AKRs and E2 pathways in doxorubicin resistance, we examined changes in the expression of E2-related genes and proteins upon acquisition of doxorubicin resistance. We also assessed the effects of AKR overexpression or downregulation or the effects of activators or inhibitors of E2-dependent pathways on previously acquired resistance to doxorubicin. In this study we observed that the enhanced AKR expression upon acquisition of anthracycline resistance was, in fact, associated with enhanced E2 production. However, the expression of estrogen receptor α (ERα) was reduced by 2- to 5-fold at the gene transcript level and 2- to 20-fold at the protein level upon acquisition of anthracycline resistance. This was accompanied by an even stronger reduction in ERα phosphorylation and activity, including highly suppressed expression of two proteins under E2-dependent control (Bcl-2 and cyclin D1). The diminished Bcl-2 and cyclin D1 expression would be expected to reduce the growth rate of the cells, a hypothesis which was confirmed in subsequent cell proliferation experiments. AKR1C3 or AKR1B10 overexpression alone had no effect on doxorubicin sensitivity in MCF-7_CC cells, while siRNA-mediated knockdown of AKR1C3 and/or AKR1B10 expression had no significant effect on sensitivity to doxorubicin in MCF-7_DOX2 or MCF-7_EPI cells. This suggested that enhanced or reduced AKR expression/activity is insufficient to confer anthracycline resistance or sensitivity to breast tumor cells, respectively. Rather, it would appear that AKR overexpression acts in concert with other proteins to confer anthracycline resistance, including reduced E2-dependent expression of both an important apoptosis inhibitor (Bcl-2) and a key protein associated with activation of cell cycle-dependent kinases (cyclin D1).

Hormonal Modulation of Breast Cancer Gene Expression: Implications for Intrinsic Subtyping in Premenopausal Women

Clinics are increasingly adopting gene-expression profiling to diagnose breast cancer subtype, providing an intrinsic, molecular portrait of the tumor. For example, the PAM50-based Prosigna test quantifies expression of 50 key genes to classify breast cancer subtype, and this method of classification has been demonstrated to be superior over traditional immunohistochemical methods that detect proteins, to predict risk of disease recurrence. However, these tests were largely developed and validated using breast cancer samples from postmenopausal women. Thus, the accuracy of such tests has not been explored in the context of the hormonal fluctuations in estrogen and progesterone that occur during the menstrual cycle in premenopausal women. Concordance between traditional methods of subtyping and the new tests in premenopausal women is likely to depend on the stage of the menstrual cycle at which the tissue sample is taken and the relative effect of hormones on expression of genes versus proteins. The lack of knowledge around the effect of fluctuating estrogen and progesterone on gene expression in breast cancer patients raises serious concerns for intrinsic subtyping in premenopausal women, which comprise about 25% of breast cancer diagnoses. Further research on the impact of the menstrual cycle on intrinsic breast cancer profiling is required if premenopausal women are to benefit from the new technology of intrinsic subtyping.

Strategies in functional proteomics: Unveiling the pathways to precision oncology

Personalised strategies in cancer care are required to overcome the therapeutic challenges posed by variability between patients and disease subsets. To this end, enhanced precision tools must be developed to describe the molecular drivers of malignant proliferation. Such tools must also identify druggable targets and biomarkers in order to provide essential information regarding drug development and therapeutic outcome. Here we discuss how proteomics-based approaches provide a set of viable methodologies capable of delivering quantitative information throughout the main stages of personalised oncology and a ratiometric platform that delivers systems-wide methods for drug evaluation.

Quantification of regenerative potential in primary human mammary epithelial cells

We present an organoid regeneration assay in which freshly isolated human mammary epithelial cells are cultured in adherent or floating collagen gels, corresponding to a rigid or compliant matrix environment. In both conditions, luminal progenitors form spheres, whereas basal cells generate branched ductal structures. In compliant but not rigid collagen gels, branching ducts form alveoli at their tips, express basal and luminal markers at correct positions, and display contractility, which is required for alveologenesis. Thereby, branched structures generated in compliant collagen gels resemble terminal ductal-lobular units (TDLUs), the functional units of the mammary gland. Using the membrane metallo-endopeptidase CD10 as a surface marker enriches for TDLU formation and reveals the presence of stromal cells within the CD49f(hi)/EpCAM(-) population. In summary, we describe a defined in vitro assay system to quantify cells with regenerative potential and systematically investigate their interaction with the physical environment at distinct steps of morphogenesis.

Hormone-sensing mammary epithelial progenitors: emerging identity and hormonal regulation

The hormone-sensing mammary epithelial cell (HS-MEC-expressing oestrogen receptor-alpha (ERα) and progesterone receptor (PGR)) is often represented as being terminally differentiated and lacking significant progenitor activity after puberty. Therefore while able to profoundly influence the proliferation and function of other MEC populations, HS-MECs are purported not to respond to sex hormone signals by engaging in significant cell proliferation during adulthood. This is a convenient and practical simplification that overshadows the sublime, and potentially critical, phenotypic plasticity found within the adult HS-MEC population. This concept is exemplified by the large proportion (~80 %) of human breast cancers expressing PGR and/or ERα, demonstrating that HS-MECs clearly proliferate in the context of breast cancer. Understanding how HS-MEC proliferation and differentiation is driven could be key to unraveling the mechanisms behind uncontrolled HS-MEC proliferation associated with ERα- and/or PGR-positive breast cancers. Herein we review evidence for the existence of a HS-MEC progenitor and the emerging plasticity of the HS-MEC population in general. This is followed by an analysis of hormones other than oestrogen and progesterone that are able to influence HS-MEC proliferation and differentiation: androgens, prolactin and transforming growth factor-beta1.

ERrrr…where are the progenitors? Hormone receptors and mammary cell heterogeneity

The mammary epithelium is a highly heterogenous and dynamic tissue that includes a range of cell types with varying levels of proliferative capacity and differentiation potential, from stem to committed progenitor and mature cells. Generation of mature cells through expansion and specification of immature precursors is driven by hormonal and local stimuli. Intriguingly, although circulating hormones can be directly sensed only by a subset of mammary cells, they also regulate the behaviour of cells lacking their cognate receptors through paracrine mechanisms. Thus, mapping the hormonal signalling network on to the emerging mammary cell hierarchy appears to be a difficult task. Nevertheless, a first step towards a better understanding is the characterization of the hormone receptor expression pattern across individual cell types in the mammary epithelium. Here we review the most relevant findings on the cellular distribution of hormone receptors in the mammary gland, taking into account differences between mice and humans, the methods employed to assess receptor expression as well as the variety of approaches used to resolve the mammary cell heterogeneity.

An ex vivo model to study hormone action in the human breast

The study of hormone action in the human breast has been hampered by lack of adequate model systems. Upon in vitro culture, primary mammary epithelial cells tend to lose hormone receptor expression. Widely used hormone receptor positive breast cancer cell lines are of limited relevance to the in vivo situation. Here, we describe an ex vivo model to study hormone action in the human breast. Fresh human breast tissue specimens from surgical discard material such as reduction mammoplasties or mammectomies are mechanically and enzymatically digested to obtain tissue fragments containing ducts and lobules and multiple stromal cell types. These tissue microstructures kept in basal medium without growth factors preserve their intercellular contacts, the tissue architecture, and remain hormone responsive for several days. They are readily processed for RNA and protein extraction, histological analysis or stored in freezing medium. Fluorescence activated cell sorting (FACS) can be used to enrich for specific cell populations. This protocol provides a straightforward, standard approach for translational studies with highly complex, varied human specimens.

Dual roles for Id4 in the regulation of estrogen signaling in the mammary gland and ovary

The HLH transcriptional regulator Id4 exerts important roles in different organs, including the neural compartment, where Id4 loss usually results in early lethality. To explore the role of this basally restricted transcription factor in the mammary gland, we generated a cre-inducible mouse model. MMTV- or K14-cre-mediated deletion of Id4 led to a delay in ductal morphogenesis, consistent with previous findings using a germ-line knockout mouse model. A striking increase in the expression of ERα (Esr1), PR and FoxA1 was observed in both the basal and luminal cellular subsets of Id4-deficient mammary glands. Together with chromatin immunoprecipitation of Id4 on the Esr1 and Foxa1 promoter regions, these data imply that Id4 is a negative regulator of the ERα signaling axis. Unexpectedly, examination of the ovaries of targeted mice revealed significantly increased numbers of secondary and antral follicles, and reduced Id4 expression in the granulosa cells. Moreover, expression of the cascade of enzymes that are crucial for estrogen biosynthesis in the ovary was decreased in Id4-deficient females and uterine weights were considerably lower, indicating impaired estrogen production. Thus, compromised ovarian function and decreased circulating estrogen likely contribute to the mammary ductal defects evident in Id4-deficient mice. Collectively, these data identify Id4 as a novel regulator of estrogen signaling, where Id4 restrains ERα expression in the basal and luminal cellular compartments of the mammary gland and regulates estrogen biosynthesis in the ovary.

Estrogen receptor coregulators and pioneer factors: the orchestrators of mammary gland cell fate and development

The steroid hormone, 17β-estradiol (E2), plays critical role in various cellular processes such as cell proliferation, differentiation, migration and apoptosis, and is essential for reproduction and mammary gland development. E2 actions are mediated by two classical nuclear hormone receptors, estrogen receptor α and β (ERs). The activity of ERs depends on the coordinated activity of ligand binding, post-translational modifications (PTMs), and importantly the interaction with their partner proteins called “coregulators.” Because coregulators are proved to be crucial for ER transcriptional activity, and majority of breast cancers are ERα positive, an increased interest in the field has led to the identification of a large number of coregulators. In the last decade, gene knockout studies using mouse models provided impetus to our further understanding of the role of these coregulators in mammary gland development. Several coregulators appear to be critical for terminal end bud (TEB) formation, ductal branching and alveologenesis during mammary gland development. The emerging studies support that, coregulators along with the other ER partner proteins called “pioneer factors” together contribute significantly to E2 signaling and mammary cell fate. This review discusses emerging themes in coregulator and pioneer factor mediated action on ER functions, in particular their role in mammary gland cell fate and development.

The Roles of Epithelial-to-Mesenchymal Transition (EMT) and Mesenchymal-to-Epithelial Transition (MET) in Breast Cancer Bone Metastasis: Potential Targets for Prevention and Treatment

Many studies have revealed molecular connections between breast and bone. Genes, important in the control of bone remodeling, such as receptor activator of nuclear kappa (RANK), receptor activator of nuclear kappa ligand (RANKL), vitamin D, bone sialoprotein (BSP), osteopontin (OPN), and calcitonin, are expressed in breast cancer and lactating breast. Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) effectors play critical roles during embryonic development, postnatal growth, and epithelial homeostasis, but also are involved in a number of pathological conditions, including wound repair, fibrosis, inflammation, as well as cancer progression and bone metastasis. Transforming growth factor β (TGFβ), insulin-like growth factor I & II (IGF I & II), platelet-derived growth factor (PDGF), parathyroid hormone-related protein (PTH(rP)), vascular endothelial growth factor (VEGF), epithelial growth factors II/I (ErbB/EGF), interleukin 6 (IL-6), IL-8, IL-11, IL-1, integrin αvβ3, matrix metalloproteinases (MMPs), catepsin K, hypoxia, notch, Wnt, bone morphogenetic proteins (BMP), and hedgehog signaling pathways are important EMT and MET effectors identified in the bone microenviroment facilitating bone metastasis formation. Recently, Runx2, an essential transcription factor in the regulation of mesenchymal cell differentiation into the osteoblast lineage and proper bone development, is also well-recognized for its expression in breast cancer cells promoting osteolytic bone metastasis. Understanding the precise mechanisms of EMT and MET in the pathogenesis of breast cancer bone metastasis can inform the direction of therapeutic intervention and possibly prevention.

Progesterone/RANKL is a major regulatory axis in the human breast

Estrogens and progesterones are major drivers of breast development but also promote carcinogenesis in this organ. Yet, their respective roles and the mechanisms underlying their action in the human breast are unclear. Receptor activator of nuclear factor κB ligand (RANKL) has been identified as a pivotal paracrine mediator of progesterone function in mouse mammary gland development and mammary carcinogenesis. Whether the factor has the same role in humans is of clinical interest because an inhibitor for RANKL, denosumab, is already used for the treatment of bone disease and might benefit breast cancer patients. We show that progesterone receptor (PR) signaling failed to induce RANKL in PR(+) breast cancer cell lines and in dissociated, cultured breast epithelial cells. In clinical specimens from healthy donors and intact breast tissue microstructures, hormone response was maintained and RANKL expression was under progesterone control, which increased RNA stability. RANKL was sufficient to trigger cell proliferation and was required for progesterone-induced proliferation. The findings were validated in vivo where RANKL protein expression in the breast epithelium correlated with serum progesterone levels and the protein was expressed in a subset of luminal cells that express PR. Thus, important hormonal control mechanisms are conserved across species, making RANKL a potential target in breast cancer treatment and prevention.