Deciphering the divergent roles of progestogens in breast cancer

Antiprogestins for breast cancer treatment: We are almost ready

The development of antiprogestins was initially a gynecological purpose. However, since mifepristone was developed, its application for breast cancer treatment was immediately proposed. Later, new compounds with lower antiglucocorticoid and antiandrogenic effects were developed to be applied to different pathologies, including breast cancer. We describe herein the studies performed in the breast cancer field with special focus on those reported in recent years, ranging from preclinical biological models to those carried out in patients. We highlight the potential use of antiprogestins in breast cancer prevention in women with BRCA1 mutations, and their use for breast cancer treatment, emphasizing the need to elucidate which patients will respond. In this sense, the PR isoform ratio has emerged as a possible tool to predict antiprogestin responsiveness. The effects of combined treatments of antiprogestins together with other drugs currently used in the clinic, such as tamoxifen, CDK4/CDK6 inhibitors or pembrolizumab in preclinical models is discussed since it is in this scenario that antiprogestins will be probably introduced. Finally, we explain how transcriptomic or proteomic studies, that were carried out in different luminal breast cancer models and in breast cancer samples that responded or were predicted to respond to the antiprogestin therapy, show a decrease in proliferative pathways. Deregulated pathways intrinsic of each model are discussed, as well as how these analyses may contribute to a better understanding of the mechanisms involved.

Mechanistic analysis of enhancer sequences in the estrogen receptor transcriptional program

Estrogen Receptor α (ERα) is a major lineage determining transcription factor (TF) in mammary gland development. Dysregulation of ERα-mediated transcriptional program results in cancer. Transcriptomic and epigenomic profiling of breast cancer cell lines has revealed large numbers of enhancers involved in this regulatory program, but how these enhancers encode function in their sequence remains poorly understood. A subset of ERα-bound enhancers are transcribed into short bidirectional RNA (enhancer RNA or eRNA), and this property is believed to be a reliable marker of active enhancers. We therefore analyze thousands of ERα-bound enhancers and build quantitative, mechanism-aware models to discriminate eRNAs from non-transcribing enhancers based on their sequence. Our thermodynamics-based models provide insights into the roles of specific TFs in ERα-mediated transcriptional program, many of which are supported by the literature. We use in silico perturbations to predict TF-enhancer regulatory relationships and integrate these findings with experimentally determined enhancer-promoter interactions to construct a gene regulatory network. We also demonstrate that the model can prioritize breast cancer-related sequence variants while providing mechanistic explanations for their function. Finally, we experimentally validate the model-proposed mechanisms underlying three such variants.

Bisphenol-A in Drinking Water Accelerates Mammary Cancerogenesis and Favors an Immunosuppressive Tumor Microenvironment in BALB-neuT Mice

Bisphenol-A (BPA), a synthetic compound ubiquitously present in the environment, can act as an endocrine disruptor by binding to both canonical and non-canonical estrogen receptors (ERs). Exposure to BPA has been linked to various cancers, in particular, those arising in hormone-targeted tissues such as the breast. In this study, we evaluated the effect of BPA intake through drinking water on ErbB2/neu-driven cancerogenesis in BALB-neuT mice, transgenic for a mutated ErbB2/neu receptor gene, which reproducibly develop carcinomas in all mammary glands. In this model, BPA accelerated mammary cancerogenesis with an increase in the number of tumors per mouse and a concurrent decrease in tumor-free and overall survival. As assessed by immunohistochemistry, BALB-neuT tumors were ER-negative but expressed high levels of the alternative estrogen receptor GPR30, regardless of BPA exposure. On the other hand, BPA exposure resulted in a marked upregulation of progesterone receptors in preinvasive tumors and of Ki67, CD31, and phosphorylated Akt in invasive tumors. Moreover, based on several infiltration markers of immune cells, BPA favored an immunosuppressive tumor microenvironment. Finally, in vitro cell survival studies performed on a cell line established from a BALB-neuT breast carcinoma confirmed that BPA's impact on cancer progression can be particularly relevant after chronic, low-dose exposure.

Progestins and breast cancer hallmarks: The role of the ERK1/2 and JNK pathways in estrogen receptor positive breast cancer cells

Progestins used in hormonal contraceptives and menopausal hormone therapy (MHT) have been linked to increased breast cancer risk. Whether the association holds for all progestins is unclear and the underlying mechanisms remain poorly understood. We directly compared the effects of four progestins (medroxyprogesterone acetate (MPA), norethisterone acetate (NET-A), levonorgestrel (LNG) and drospirenone (DRSP)) to each other and the natural progestogen progesterone (P4) on selected cancer hallmarks. To provide mechanistic insight into these effects, we assessed the role of the progesterone receptor (PR), and the extracellular signal-related kinase (ERK1/2) and c-Jun N terminal (JNK) signaling pathways. We showed that the increased proliferation of the luminal T47D breast cancer cell line by P4 and all progestins, albeit to different extents, was inhibited by PR knockdown and inhibition of both the ERK1/2 and JNK pathways. While knockdown of the PR also blocked the upregulation of MKI67 and CCND1 mRNA expression by selected progestogens, only a role for the ERK1/2 pathway could be established in these effects. Similarly, only a role for the ERK1/2 pathway could be confirmed for progestogen-induced colony formation, whereas both the ERK1/2 and JNK pathways were required for cell migration in response to the three older progestins implicated in the etiology of breast cancer, MPA, NET-A and LNG. Together our results show that all the progestins elicit their effects on cell proliferation via a mechanism requiring the PR, ERK1/2 and JNK pathways. While the ERK1/2 and JNK pathways are also required for increased cell migration by the older progestins, only a role for the ERK1/2 pathway could be established in their effects on colony formation. Notably, the cytoplasmic PR was not needed for activation of the ERK1/2 pathway by the progestogens. Given that DRSP showed significantly lower proliferation than MPA and NET-A, and that it had no effect on breast cancer cell migration and colony formation, hormonal formulations containing the newer generation progestin DRSP may provide a better benefit/risk profile towards breast cancer than those containing the older generation progestins.

SIK2-positive tumor epithelial cells in breast cancer maybe potential anti-cancer messengers: A systematic analysis from a single-cell perspective

Breast cancer is the most common malignancy in the world and one of the leading causes of cancer death, which is a heterogeneous disease involving genetic and environmental factors. Breast cancer stem cells (BCSCs) are the main players in the aggressiveness of different tumors, at the same time, these cells are the main challenge for cancer treatment. There are multiple treatment options for breast cancer (BC) patients and the lack of understanding of prognostic and predictive biomarkers for breast cancer is a potential research direction for us to develop better treatments in the future. In this paper, we conducted a correlation analysis between SIK2 and clinical traits by searching numerous BRCA datasets in the GEO database. The model was constructed and validated by incorporating tumor samples from the TCGA-BRCA cohort. Surprisingly, we found differential expression of SIK2 gene in individual tumor samples from the UCSC database. Subsequently, we found significantly high expression of SIK2 in epithelial cells by comparing the differential expression of SIK2 in different cell subpopulations and performed subsequent immune infiltration and pathway correlation analysis. Differential genes in SIK2+ epithelial cells, which may be potential therapeutic targets for breast cancer. In conclusion, our results suggest that SIK2 may be a potential prognostic and predictive biomarker that could serve as an oncogenic messenger for breast cancer. This discovery of SIK2 may provide more valuable references for potential therapeutic tools for breast cancer.

Addition of progesterone to feminizing gender-affirming hormone therapy in transgender individuals for breast development: a randomized controlled trial

BACKGROUND

Feminizing gender-affirming hormone therapy (GAHT) for transgender individuals traditionally includes estradiol and androgen deprivation. Research has demonstrated that breast size as a result of GAHT in transgender women is often limited. Therefore, transgender women often choose to undergo breast augmentation surgery. Progesterone is important for breast development in cisgender women during puberty. A potential role for progesterone in breast development in transgender women has not been investigated in a randomized controlled experimental set-up. The primary objective of this study is to explore the effects on breast volume of addition of oral progesterone to GAHT with estradiol in transgender women after vaginoplasty or orchiectomy. Secondary objectives include assessment of safety, satisfaction, mood, sleep and sexual pleasure.

METHODS

This is a non-blinded, non-placebo, randomized controlled trial using a factorial design in adult transgender individuals assigned male sex at birth who have undergone GAHT for at least one year and underwent vaginoplasty or orchiectomy. The study design allows for rapid assessment of potential synergistic effects of various dose combinations of estradiol and progesterone on breast volume change: Ninety participants will be randomized into six groups of 15 subjects each, receiving either the baseline dose of estradiol, the baseline dose of estradiol and progesterone 200 mg daily, the baseline dose of estradiol and progesterone 400 mg daily, twice the baseline dose of estradiol, twice the baseline dose of estradiol and progesterone 200 mg daily or twice the baseline dose of estradiol and progesterone 400 mg daily, all for a duration of 12 months. The main study parameters include changes in breast volume as determined by 3D measurements. Participants will be followed-up with laboratory testing including serum progesterone concentrations as well as surveys for satisfaction, mood, sleep quality and sexual pleasure.

DISCUSSION

This study will indicate whether progesterone is safe and of additional value with regard to breast volume change in transgender individuals receiving feminizing GAHT. The results of this study will be useful for innovation of feminizing GAHT.

TRIAL REGISTRATION

WHO International Clinical Trials Registry Platform: EUCTR2020-001952-16-NL; date of registration: 12 December 2020 https://trialsearch.who.int/Trial2.aspx?TrialID=EUCTR2020-001952-16-NL .

Therapeutic resistance to anti-oestrogen therapy in breast cancer

The hormone receptor oestrogen receptor-α (ER) orchestrates physiological mammary gland development, breast carcinogenesis and the progression of breast tumours into lethal, treatment-refractory systemic disease. Selective antagonism of ER signalling has been one of the most successful therapeutic approaches in oncology, benefiting patients as both a cancer preventative measure and a cancer treatment strategy. However, resistance to anti-oestrogen therapy is a major clinical challenge. Over the past decade, we have gained an understanding of how breast cancers evolve under the pressure of anti-oestrogen therapy. This is best depicted by the case of oestrogen-independent mutations in the gene encoding ER (ESR1), which are virtually absent in primary breast cancer but highly prevalent (20-40%) in anti-oestrogen-treated metastatic disease. These and other findings highlight the 'evolvability' of ER+ breast cancer and the need to understand molecular processes by which this evolution occurs. Recent development and approval of next-generation ER antagonists to target ESR1-mutant breast cancer underscores the clinical importance of this evolvability and sets a new paradigm for the treatment of ER+ breast cancers.

Progesterone receptor isoform ratios influence the transcriptional activity of progestins via the progesterone receptor

Progestins (synthetic progestogens) are progesterone receptor (PR) ligands used globally by women in both hormonal contraception and menopausal hormone therapy. Although four generations of unique progestins have been developed, studies seldom distinguish between the activities of progestins via the two functionally distinct PR isoforms, PR-A and PR-B. Moreover, not much is known about the action of progestins in breast cancer tumors where PR-A is mostly overexpressed relative to PR-B. Understanding progestin action in breast cancer is crucial since the clinical use of some progestins has been associated with an increased risk of developing breast cancer. This study directly compared the agonist activities of selected progestins from all four generations for transactivation and transrepression via either PR-A or PR-B, and when PR-A and PR-B were co-expressed at ratios comparable to those detected in breast cancer tumors. Comparative dose-response analysis showed that earlier generation progestins mostly displayed similar efficacies for transactivation on a minimal progesterone response element via the PR isoforms, while most of the 4th generation progestins, similar to the natural progestogen, progesterone (P4), were more efficacious via PR-B. Most of the progestogens were however more potent via PR-A. We are the first to show that the efficacies of the selected progestogens via the individual PR isoforms were generally decreased when PR-A and PR-B were co-expressed, irrespective of the ratio of PR-A:PR-B. While the potencies of most progestogens via PR-B were enhanced when the ratio of PR-A relative to PR-B was increased, those via PR-A were minimally influenced. This study is also the first to report that all progestogens evaluated, except 1st generation medroxyprogesterone acetate and 4th generation drospirenone, displayed similar agonist activity for transrepression via PR-A and PR-B on a minimal nuclear factor kappa B containing promoter. Moreover, we showed that the progestogen activity for transrepression was significantly increased when PR-A and PR-B were co-expressed. Taken together, our results highlight that PR agonists (progestogens) do not always display the same activity via PR-A and PR-B, or when PR-A and PR-B are co-expressed at ratios mimicking those found in breast cancer tumors. These results suggest that biological responses are progestogen- and PR isoform-dependent and may differ in target tissues expressing varying PR-A:PR-B ratios.

Molecular characterization of breast cancer cell pools with normal or reduced ability to respond to progesterone: a study based on RNA-seq

BACKGROUND

About one-third of patients with estrogen receptor alpha (ERα)-positive breast cancer have tumors which are progesterone receptor (PR) negative. PR is an important prognostic factor in breast cancer. Patients with ERα-positive/PR-negative tumors have shorter disease-free and overall survival than patients with ERα-positive/PR-positive tumors. New evidence has shown that progesterone (P4) has an anti-proliferative effect in ERα-positive breast cancer cells. However, the role of PR in breast cancer is only poorly understood.

METHODS

We disrupted the PR gene (PGR) in ERα-positive/PR-positive T-47D cells using the CRISPR/Cas9 system. This resulted in cell pools we termed PR-low as P4 mediated effects were inhibited or blocked compared to control T-47D cells. We analyzed the gene expression profiles of PR-low and control T-47D cells in the absence of hormone and upon treatment with P4 alone or P4 together with estradiol (E2). Differentially expressed (DE) genes between experimental groups were characterized based on RNA-seq and Gene Ontology (GO) enrichment analyses.

RESULTS

The overall gene expression pattern was very similar between untreated PR-low and untreated control T-47D cells. More than 6000 genes were DE in control T-47D cells upon stimulation with P4 or P4 plus E2. When PR-low pools were subjected to the same hormonal treatment, up- or downregulation was either blocked/absent or consistently lower. We identified more than 3000 genes that were DE between hormone-treated PR-low and control T-47D cells. GO analysis revealed seven significantly enriched biological processes affected by PR and associated with G protein-coupled receptor (GPCR) pathways which have been described to support growth, invasiveness, and metastasis in breast cancer cells.

CONCLUSIONS

The present study provides new insights into the complex role of PR in ERα-positive/PR-positive breast cancer cells. Many of the genes affected by PR are part of central biological processes of tumorigenesis.

A review of prognostic and predictive biomarkers in breast cancer

Breast cancer (BC) is a common cancer all over the world that affects women. BC is one of the leading causes of cancer mortality in women, which today has decreased with the advancement of technology and new diagnostic and therapeutic methods. BCs are histologically divided into in situ and invasive carcinoma, and both of them can be divided into ductal and lobular. The main function after the diagnosis of invasive breast cancer is which patient should use chemotherapy, which patient should receive adjuvant therapy, and which should not. If the decision is for adjuvant therapy, the next challenge is to identify the most appropriate treatment or combination of treatments for a particular patient. Addressing the first challenge can be helped by prognostic biomarkers, while addressing the second challenge can be done by predictive biomarkers. Among the molecular markers related to BC, ER, PR, HER2, and the Mib1/Ki-67 proliferation index are the most significant ones and are tightly confirmed in the standard care of all primary, recurrent, and metastatic BC patients. CEA and CA-15-3 antigens are the most valuable markers of serum tumors in BC patients. Determining the series of these markers helps monitor response to the treatment and early detection of recurrence or metastasis. miRNAs have been demonstrated to be intricate in mammary gland growth, proliferation, and formation of BC known to be incriminated in BC biology. By combining established prognostic factors with valid prognostic/predicted biomarkers, we can start the journey to personalized treatment for every recently diagnosed BC patient.

Upregulation of an estrogen receptor-regulated gene by first generation progestins requires both the progesterone receptor and estrogen receptor alpha

Progestins, synthetic compounds designed to mimic the activity of natural progesterone (P4), are used globally in menopausal hormone therapy. Although the older progestins medroxyprogesterone acetate (MPA) and norethisterone (NET) have been implicated in increased breast cancer risk, little is known regarding newer progestins, and no significant risk has been associated with P4. Considering that breast cancer is the leading cause of mortality in women, establishing which progestins increase breast cancer incidence and elucidating the underlying mechanisms is a global priority. We showed for the first time that the newer-generation progestin drospirenone (DRSP) is the least potent progestin in terms of proliferation of the estrogen-responsive MCF-7 BUS breast cancer cell line, while NET and P4 have similar potencies to estradiol (E2), the known driver of breast cancer cell proliferation. Notably, MPA, the progestin most frequently associated with increased breast cancer risk, was significantly more potent than E2. While all the progestogens enhanced the anchorage-independent growth of the MCF-7 BUS cell line, MPA promoted a greater number of colonies than P4, NET or DRSP. None of the progestogens inhibited E2-induced proliferation and anchorage-independent growth. We also showed that under non-estrogenic conditions, MPA and NET, unlike P4 and DRSP, increased the expression of the estrogen receptor (ER) target gene, cathepsin D, via a mechanism requiring the co-recruitment of ERα and the progesterone receptor (PR) to the promoter region. In contrast, all progestogens promoted the association of the PR and ERα on the promoter of the PR target gene, MYC, thereby increasing its expression under non-estrogenic and estrogenic conditions. These results suggest that progestins differentially regulate the way the PR and ER converge to modulate the expression of PR and ER-regulated genes. Our novel findings indicating similarities and differences between P4 and the progestins, emphasize the importance of comparatively investigating effects of individual progestins rather than grouping them as a class. Further studies are required to underpin the clinical relevance of PR/ERα crosstalk in response to different progestins in both normal and malignant breast tissue, to either confirm or refute their suitability in combination therapy for ER-positive breast cancer.

Association of serum reproductive hormones changes after neoadjuvant chemotherapy with hormone receptors expression alterations and survival outcomes in breast cancer

Purpose

This study aimed to determine the effect of neoadjuvant chemotherapy (NAC) on circulating levels of reproductive hormones and evaluate the correlation of hormone changes after NAC with hormone receptors expression alterations and relapse-free survival (RFS) outcomes in breast cancer.

Methods

Information from 181 breast cancer patients who received NAC was retrospectively analyzed. For hormones parameters, the median and interquartile range (IQR) were provided at baseline and the end of NAC then was compared by Wilcoxon signed-rank test. Categorical variables were represented as numbers and percentages and were compared via two-sided chi-square and Fisher's tests. The RFS outcomes were compared between patients according to hormone changes using the log-rank test. Univariate and multivariate survival analyses with hazard ratios (HR) and 95% confidence intervals (95% CI) were carried out using Cox regression.

Results

Sex steroids including estradiol, progesterone, testosterone, and dehydroepiandrosterone sulfate (DHEAS) levels decreased significantly after NAC among both premenopausal and postmenopausal patients (all P < 0.05). Decreased estradiol levels were associated with reduced progesterone receptor (PR) expression (P = 0.030). In multivariate survival analysis, the non-decreased progesterone level was strongly associated with worse RFS (non-decreased vs. decreased, HR = 7.178, 95% CI 2.340–22.019, P = 0.001). Patients with decreased progesterone levels exhibited better 3-year RFS compared with those with non-decreased (87.6% vs. 58.3%, log-rank, P = 0.001).

Conclusion

Multiple reproductive hormone levels were influenced by NAC. The change in estradiol level had a positive connection with PR expression alteration. Furthermore, an inverse association between the change in progesterone level and RFS outcomes was found. These findings may provide a theoretical basis for pre-operative endocrine therapy combined with NAC in breast cancer patients.

High Levels of Progesterone Receptor B in MCF-7 Cells Enable Radical Anti-Tumoral and Anti-Estrogenic Effect of Progestin

The widely reported conflicting effects of progestin on breast cancer suggest that the progesterone receptor (PR) has dual functions depending on the cellular context. Cell models that enable PR to fully express anti-tumoral properties are valuable for the understanding of molecular determinant(s) of the anti-tumoral property. This study evaluated whether the expression of high levels of PR in MCF-7 cells enabled a strong anti-tumoral response to progestin. MCF-7 cells were engineered to overexpress PRB by stable transfection. A single dose of Promegestone (R5020) induced an irreversible cell growth arrest and senescence-associated secretory phenotype in MCF-7 cells with PRB overexpression (MCF-7PRB cells) but had no effect on MCF-7 cells with PRA overexpression. The growth-arresting effect was associated with downregulations of cyclin A2 and B1, CDK2, and CDK4 despite an initial upregulation of cyclin A2 and B1. R5020 also induced an evident activation of Nuclear Factor κB (NF-κB) and upregulation of interleukins IL-1α, IL-1β, and IL-8. Although R5020 caused a significant increase of CD24+CD44+ cell population, R5020-treated MCF-7PRB cells were unable to form tumorspheres and underwent massive apoptosis, which is paradoxically associated with marked downregulations of the pro-apoptotic proteins BID, BAX, PARP, and Caspases 7 and 8, as well as diminution of anti-apoptotic protein BCL-2. Importantly, R5020-activated PRB abolished the effect of estrogen. This intense anti-estrogenic effect was mediated by marked downregulation of ERα and pioneer factor FOXA1, leading to diminished chromatin-associated ERα and FOXA1 and estrogen-induced target gene expression. In conclusion, high levels of agonist-activated PRB in breast cancer cells can be strongly anti-tumoral and anti-estrogenic despite the initial unproductive cell cycle acceleration. Repression of ERα and FOXA1 expression is a major mechanism for the strong anti-estrogenic effect.

Estrogen receptor positive breast cancers have patient specific hormone sensitivities and rely on progesterone receptor

Estrogen and progesterone receptor (ER, PR) signaling control breast development and impinge on breast carcinogenesis. ER is an established driver of ER + disease but the role of the PR, itself an ER target gene, is debated. We assess the issue in clinically relevant settings by a genetic approach and inject ER + breast cancer cell lines and patient-derived tumor cells to the milk ducts of immunocompromised mice. Such ER + xenografts were exposed to physiologically relevant levels of 17-β-estradiol (E2) and progesterone (P4). We find that independently both premenopausal E2 and P4 levels increase tumor growth and combined treatment enhances metastatic spread. The proliferative responses are patient-specific with MYC and androgen receptor (AR) signatures determining P4 response. PR is required for tumor growth in patient samples and sufficient to drive tumor growth and metastasis in ER signaling ablated tumor cells. Our findings suggest that endocrine therapy may need to be personalized, and that abrogating PR expression can be a therapeutic option.

A human breast atlas integrating single-cell proteomics and transcriptomics

The breast is a dynamic organ whose response to physiological and pathophysiological conditions alters its disease susceptibility, yet the specific effects of these clinical variables on cell state remain poorly annotated. We present a unified, high-resolution breast atlas by integrating single-cell RNA-seq, mass cytometry, and cyclic immunofluorescence, encompassing a myriad of states. We define cell subtypes within the alveolar, hormone-sensing, and basal epithelial lineages, delineating associations of several subtypes with cancer risk factors, including age, parity, and BRCA2 germline mutation. Of particular interest is a subset of alveolar cells termed basal-luminal (BL) cells, which exhibit poor transcriptional lineage fidelity, accumulate with age, and carry a gene signature associated with basal-like breast cancer. We further utilize a medium-depletion approach to identify molecular factors regulating cell-subtype proportion in organoids. Together, these data are a rich resource to elucidate diverse mammary cell states.

The Divergent Effects of Ovarian Steroid Hormones in the MCF-7 Model for Luminal A Breast Cancer: Mechanistic Leads for Therapy

The growth modulating effects of the ovarian steroid hormones 17β-estradiol (E₂) and progesterone (PRG) on endocrine-responsive target tissues are well established. In hormone-receptor-positive breast cancer, E₂ functions as a potent growth promoter, while the function of PRG is less defined. In the hormone-receptor-positive Luminal A and Luminal B molecular subtypes of clinical breast cancer, conventional endocrine therapy predominantly targets estrogen receptor function and estrogen biosynthesis and/or growth factor receptors. These therapeutic options are associated with systemic toxicity, acquired tumor resistance, and the emergence of drug-resistant cancer stem cells, facilitating the progression of therapy-resistant disease. The limitations of targeted endocrine therapy emphasize the identification of nontoxic testable alternatives. In the human breast, carcinoma-derived hormone-receptor-positive MCF-7 model treatment with E₂ within the physiological concentration range of 1 nM to 20 nM induces progressive growth, upregulated cell cycle progression, and downregulated cellular apoptosis. In contrast, treatment with PRG at the equimolar concentration range exhibits dose-dependent growth inhibition, downregulated cell-cycle progression, and upregulated cellular apoptosis. Nontoxic nutritional herbs at their respective maximum cytostatic concentrations (IC₉₀) effectively increase the E₂ metabolite ratio in favor of the anti-proliferative metabolite. The long-term exposure to the selective estrogen-receptor modulator tamoxifen selects a drug-resistant phenotype, exhibiting increased expressions of stem cell markers. The present review discusses the published evidence relevant to hormone metabolism, growth modulation by hormone metabolites, drug-resistant stem cells, and growth-inhibitory efficacy of nutritional herbs. Collectively, this evidence provides proof of the concept for future research directions that are focused on novel therapeutic options for endocrine therapy-resistant breast cancer that may operate via E₂- and/or PRG-mediated growth regulation.

Estrogens and Progestins Cooperatively Shift Breast Cancer Cell Metabolism

Metabolic reprogramming remains largely understudied in relation to hormones in estrogen receptor (ER) and progesterone receptor (PR) positive breast cancer. In this study, we investigated how estrogens, progestins, or the combination, impact metabolism in three ER and PR positive breast cancer cell lines. We measured metabolites in the treated cells using ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). Top metabolic processes upregulated with each treatment involved glucose metabolism, including Warburg effect/glycolysis, gluconeogenesis, and the pentose phosphate pathway. RNA-sequencing and pathway analysis on two of the cell lines treated with the same hormones, found estrogens target oncogenes, such as MYC and PI3K/AKT/mTOR that control tumor metabolism, while progestins increased genes associated with fatty acid metabolism, and the estrogen/progestin combination additionally increased glycolysis. Phenotypic analysis of cell energy metabolism found that glycolysis was the primary hormonal target, particularly for the progestin and estrogen-progestin combination. Transmission electron microscopy found that, compared to vehicle, estrogens elongated mitochondria, which was reversed by co-treatment with progestins. Progestins promoted lipid storage both alone and in combination with estrogen. These findings highlight the shift in breast cancer cell metabolism to a more glycolytic and lipogenic phenotype in response to combination hormone treatment, which may contribute to a more metabolically adaptive state for cell survival.

The Flavonoid Baicalein Negatively Regulates Progesterone Target Genes in the Uterus in Vivo

Baicalein is a flavonoid extracted from the root of Scutellaria baicalensis (Chinese skullcap) and is consumed as part of this botanical dietary supplement to reduce oxidative stress, pain, and inflammation. We previously reported that baicalein can also modify receptor signaling through the progesterone receptor (PR) and glucocorticoid receptor (GR) in vitro, which is interesting due to the well-established roles of both PR and GR in reducing inflammation. To understand the effects of baicalein on PR and GR signaling in vivo in the uterus, ovariectomized CD-1 mice were treated with DMSO, progesterone (P4), baicalein, P4 with baicalein, and P4 with RU486, a PR antagonist, for a week. The uteri were collected for histology and RNA sequencing. Our results showed that baicalein attenuated the antiproliferative effect of P4 on luminal epithelium as well as on the PR target genes HAND2 and ZBTB16. Baicalein did not change levels of PR or GR RNA or protein in the uterus. RNA sequencing data indicated that many transcripts significantly altered by baicalein were regulated in the opposite direction by P4. Similarly, a large portion of GO/KEGG terms and GSEA gene sets were altered in the opposite direction by baicalein as compared to P4 treatment. Treatment of baicalein did not change body weight, organ weight, or blood glucose level. In summary, baicalein functioned as a PR antagonist in vivo and therefore may oppose P4 action under certain conditions such as uterine hyperplasia, fibroids, and uterine cancers.

Estrogen Receptor Bio-Activities Determine Clinical Endocrine Treatment Options in Estrogen Receptor-Positive Breast Cancer

In estrogen receptor positive (ER+) breast cancer therapy, estrogen receptors (ERs) are the major targeting molecules. ER-targeted therapy has provided clinical benefits for approximately 70% of all breast cancer patients through targeting the ERα subtype. In recent years, mechanisms underlying breast cancer occurrence and progression have been extensively studied and largely clarified. The PI3K/AKT/mTOR pathway, microRNA regulation, and other ER downstream signaling pathways are found to be the effective therapeutic targets in ER+ BC therapy. A number of the ER+ (ER+) breast cancer biomarkers have been established for diagnosis and prognosis. The ESR1 gene mutations that lead to endocrine therapy resistance in ER+ breast cancer had been identified. Mutations in the ligand-binding domain of ERα which encoded by ESR1 gene occur in most cases. The targeted drugs combined with endocrine therapy have been developed to improve the therapeutic efficacy of ER+ breast cancer, particularly the endocrine therapy resistance ER+ breast cancer. The combination therapy has been demonstrated to be superior to monotherapy in overall clinical evaluation. In this review, we focus on recent progress in studies on ERs and related clinical applications for targeted therapy and provide a perspective view for therapy of ER+ breast cancer.

Interferon Signaling in Estrogen Receptor-positive Breast Cancer: A Revitalized Topic

Cancer immunology is the most rapidly expanding field in cancer research, with the importance of immunity in cancer pathogenesis now well accepted including in the endocrine-related cancers. The immune system plays an essential role in the development of ductal and luminal epithelial differentiation in the mammary gland. Originally identified as evolutionarily conserved antipathogen cytokines, interferons (IFNs) have shown important immune-modulatory and antineoplastic properties when administered to patients with various types of cancer, including breast cancer. Recent studies have drawn attention to the role of tumor- and stromal-infiltrating lymphocytes in dictating therapy response and outcome of breast cancer patients, which, however, is highly dependent on the breast cancer subtype. The emerging role of tumor cell-inherent IFN signaling in the subtype-defined tumor microenvironment could influence therapy response with protumor activities in breast cancer. Here we review evidence with new insights into tumor cell-intrinsic and tumor microenvironment-derived IFN signaling, and the crosstalk of IFN signaling with key signaling pathways in estrogen receptor-positive (ER+) breast cancer. We also discuss clinical implications and opportunities exploiting IFN signaling to treat advanced ER+ breast 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.

The role of estrogen and progesterone receptors in the rotator cuff disease: a retrospective cohort study

Background

Rotator cuff (RC) tears represent a common cause of shoulder pain and dysfunction in adults. The disease affects primarily women and occurs mainly in the postmenopausal period.

This study aimed to investigate immunohistochemically the presence of estrogen receptor-alpha (ER-⍺), estrogen receptor-beta (ER-β) and progesterone receptor (PR) in the supraspinatus tendon of patients with RC tendinopathy, searching for gender differences of expression. A secondary aim was to evaluate potential links between their expression and the typical histopathological findings of the ailment.

Methods

Biopsies of the supraspinatus tendon were collected intraoperatively from 15 postmenopausal women and 9 men undergoing RC surgery. Specimens were stained with Haematoxylin/Eosin, Masson-Goldner Trichrome, Alcian Blu and immunohistochemical stainings for ER-⍺, ER-β and PR were performed. Tendon alterations were evaluated with the Bonar histopathological scale. Statistical tests used in this study were the Spearman correlation coefficient and the Mann-Whitney U test.

Results

In the supraspinatus tendon, cells expressed ER-⍺ (p = 0.043), ER-β (p = 0.048) and PR (p = 0.004) with statistically significant differences related to age and sex of patients. Immunoreactivity was seen in the nuclei of tenocytes and vascular cells. Postmenopausal women’s samples showed a markedly higher expression of these receptors compared to their male counterpart. There was a positive correlation between the expression of ER-⍺ and ER-β (r = 0.59; p = 0.02) and between ER-β and PR (r = 0.72; p = 0.002) in women’s samples. Furthermore, in postmenopausal women the PR expression decreased with age (r = − 0.56; p = 0.027). Only in women, the ER-β expression positively correlated with the total Bonar histopathological score (p = 0.019) and the ER-β vascular expression positively correlated with ground substance alterations (p = 0.029).

Conclusions

These results reveal that ERs and PR are present in the supraspinatus tendon of patients with RC tears, suggesting a role of sex hormones in the pathogenesis of the disease.

Key to Life: Physiological Role and Clinical Implications of Progesterone

The most recent studies of progesterone research provide remarkable insights into the physiological role and clinical importance of this hormone. Although the name progesterone itself means “promoting gestation”, this steroid hormone is far more than a gestational agent. Progesterone is recognized as a key physiological component of not only the menstrual cycle and pregnancy but also as an essential steroidogenic precursor of other gonadal and non-gonadal hormones such as aldosterone, cortisol, estradiol, and testosterone. Based on current findings, progesterone and novel progesterone-based drugs have many important functions, including contraception, treatment of dysfunctional uterine bleeding, immune response, and prevention of cancer. Considering the above, reproduction and life are not possible without progesterone; thus, a better understanding of this essential molecule could enable safe and effective use of this hormone in many clinical conditions.

Type 1 Nuclear Receptor Activity in Breast Cancer: Translating Preclinical Insights to the Clinic

The nuclear receptor (NR) family of transcription factors is intimately associated with the development, progression and treatment of breast cancer. They are used diagnostically and prognostically, and crosstalk between nuclear receptor pathways and growth factor signalling has been demonstrated in all major subtypes of breast cancer. The majority of breast cancers are driven by estrogen receptor α (ER), and anti-estrogenic therapies remain the backbone of treatment, leading to clinically impactful improvements in patient outcomes. This serves as a blueprint for the development of therapies targeting other nuclear receptors. More recently, pivotal findings into modulating the progesterone (PR) and androgen receptors (AR), with accompanying mechanistic insights into NR crosstalk and interactions with other proliferative pathways, have led to clinical trials in all of the major breast cancer subtypes. A growing body of evidence now supports targeting other Type 1 nuclear receptors such as the glucocorticoid receptor (GR), as well as Type 2 NRs such as the vitamin D receptor (VDR). Here, we reviewed the existing preclinical insights into nuclear receptor activity in breast cancer, with a focus on Type 1 NRs. We also discussed the potential to translate these findings into improving patient outcomes.

Lost but Not Least-Novel Insights into Progesterone Receptor Loss in Estrogen Receptor-Positive Breast Cancer

Estrogen receptor α (ERα) and progesterone receptor (PgR) are crucial prognostic and predictive biomarkers that are usually co-expressed in breast cancer (BC). However, 12-24% of BCs present ERα(+)/PgR(-) phenotype at immunohistochemical evaluation. In fact, BC may either show primary PgR(-) status (in chemonaïve tumor sample), lose PgR expression during neoadjuvant treatment, or acquire PgR(-) phenotype in local relapse or metastasis. The loss of PgR expression in ERα(+) breast cancer may signify resistance to endocrine therapy and poorer outcomes. On the other hand, ERα(+)/PgR(-) BCs may have a better response to neoadjuvant chemotherapy than double-positive tumors. Loss of PgR expression may be a result of pre-transcriptional alterations (copy number loss, mutation, epigenetic modifications), decreased transcription of the PGR gene (e.g., by microRNAs), and post-translational modifications (e.g., phosphorylation, sumoylation). Various processes involved in the down-regulation of PgR have distinct consequences on the biology of cancer cells. Occasionally, negative PgR status detected by immunohistochemical analysis is paradoxically associated with enhanced transcriptional activity of PgR that might be inhibited by antiprogestin treatment. Identification of the mechanism of PgR loss in each patient seems challenging, yet it may provide important information on the biology of the tumor and predict its responsiveness to the therapy.

Leveraging Antiprogestins in the Treatment of Metastatic Breast Cancer

Although incurable, the prognosis for patients with metastatic breast cancer (MBC) has considerably improved with the approvals of multiple targeted and cytotoxic therapies. For hormone receptor-positive (HR+), ie, estrogen receptor and progesterone receptor positive (ER+/PgR+) and human epidermal growth factor receptor-2 negative (ie, ERBB2 gene nonamplified or HER2-) MBC, current approved treatment options include palliative endocrine therapy (ET), cyclin-dependent kinase (CDK 4/6) inhibitors, mTOR inhibitors, and PI3 kinase inhibitors. Most treatments target ER+ disease regardless of PgR status. Although the presence of PgR is crucial for ER+ cell proliferation in both normal and malignant mammary tissue, currently, there are no approved treatments that specifically target PgR. Recent literature has demonstrated the potential of antiprogestins in the treatment of MBC both in preclinical and clinical studies. Antiprogestins, including selective PgR modulators (SPRMs) that act as PgR antagonists, are a promising class of therapeutics for overcoming endocrine resistance in patients who develop activating estrogen receptor 1 (ESR1) and phosphatidylinositol 3-kinase (PI3K) gene mutations after prior endocrine therapy. Herein, we summarize the role of PgR and antiprogestins in the treatment of MBC. Other aspects on the use of functional imaging, clinical trials incorporating novel antiprogestins, and potential treatment combinations to overcome endocrine resistance will be briefly discussed.

Genome-wide crosstalk between steroid receptors in breast and prostate cancers

Steroid receptors (SRs) constitute an important class of signal-dependent transcription factors (TFs). They regulate a variety of key biological processes and are crucial drug targets in many disease states. In particular, estrogen (ER) and androgen receptors (AR) drive the development and progression of breast and prostate cancer, respectively. Thus, they represent the main specific drug targets in these diseases. Recent evidence has suggested that the crosstalk between signal-dependent TFs is an important step in the reprogramming of chromatin sites; a signal-activated TF can expand or restrict the chromatin binding of another TF. This crosstalk can rewire gene programs and thus alter biological processes and influence the progression of disease. Lately, it has been postulated that there may be an important crosstalk between the AR and the ER with other SRs. Especially, progesterone (PR) and glucocorticoid receptor (GR) can reprogram chromatin binding of ER and gene programs in breast cancer cells. Furthermore, GR can take the place of AR in antiandrogen-resistant prostate cancer cells. Here, we review the current knowledge of the crosstalk between SRs in breast and prostate cancers. We emphasize how the activity of ER and AR on chromatin can be modulated by other SRs on a genome-wide scale. We also highlight the knowledge gaps in the interplay of SRs and their complex interactions with other signaling pathways and suggest how to experimentally fill in these gaps.

Proteogenomic Workflow Reveals Molecular Phenotypes Related to Breast Cancer Mammographic Appearance

Proteogenomic approaches have enabled the generat̲ion of novel information levels when compared to single omics studies although burdened by extensive experimental efforts. Here, we improved a data-independent acquisition mass spectrometry proteogenomic workflow to reveal distinct molecular features related to mammographic appearances in breast cancer. Our results reveal splicing processes detectable at the protein level and highlight quantitation and pathway complementarity between RNA and protein data. Furthermore, we confirm previously detected enrichments of molecular pathways associated with estrogen receptor-dependent activity and provide novel evidence of epithelial-to-mesenchymal activity in mammography-detected spiculated tumors. Several transcript-protein pairs displayed radically different abundances depending on the overall clinical properties of the tumor. These results demonstrate that there are differentially regulated protein networks in clinically relevant tumor subgroups, which in turn alter both cancer biology and the abundance of biomarker candidates and drug targets.

O-GlcNAcylation and O-GlcNAc Cycling Regulate Gene Transcription: Emerging Roles in Cancer

Simple Summary

O-linked β-N-acetylglucosamine (O-GlcNAc) is a post-translational modification (PTM) linking nutrient flux through the hexosamine biosynthetic pathway (HBP) to gene transcription. Mounting experimental and clinical data implicates aberrant O-GlcNAcylation in the development and progression of cancer. Herein, we discuss how alteration of O-GlcNAc-regulated transcriptional mechanisms leads to atypical gene expression in cancer. We discuss the challenges associated with studying O-GlcNAc function and present several new approaches for studies of O-GlcNAc-regulated transcription.

Abstract

O-linked β-N-acetylglucosamine (O-GlcNAc) is a single sugar post-translational modification (PTM) of intracellular proteins linking nutrient flux through the Hexosamine Biosynthetic Pathway (HBP) to the control of cis-regulatory elements in the genome. Aberrant O-GlcNAcylation is associated with the development, progression, and alterations in gene expression in cancer. O-GlcNAc cycling is defined as the addition and subsequent removal of the modification by O-GlcNAc Transferase (OGT) and O-GlcNAcase (OGA) provides a novel method for cells to regulate various aspects of gene expression, including RNA polymerase function, epigenetic dynamics, and transcription factor activity. We will focus on the complex relationship between phosphorylation and O-GlcNAcylation in the regulation of the RNA Polymerase II (RNAP II) pre-initiation complex and the regulation of the carboxyl-terminal domain of RNAP II via the synchronous actions of OGT, OGA, and kinases. Additionally, we discuss how O-GlcNAcylation of TATA-box binding protein (TBP) alters cellular metabolism. Next, in a non-exhaustive manner, we will discuss the current literature on how O-GlcNAcylation drives gene transcription in cancer through changes in transcription factor or chromatin remodeling complex functions. We conclude with a discussion of the challenges associated with studying O-GlcNAcylation and present several new approaches for studying O-GlcNAc regulated transcription that will advance our understanding of the role of O-GlcNAc in cancer.

A comprehensive review on non-clinical methods to study transfer of medication into breast milk - A contribution from the ConcePTION project

Breastfeeding plays a major role in the health and wellbeing of mother and infant. However, information on the safety of maternal medication during breastfeeding is lacking for most medications. This leads to discontinuation of either breastfeeding or maternal therapy, although many medications are likely to be safe. Since human lactation studies are costly and challenging, validated non-clinical methods would offer an attractive alternative. This review gives an extensive overview of the non-clinical methods (in vitro, in vivo and in silico) to study the transfer of maternal medication into the human breast milk, and subsequent neonatal systemic exposure. Several in vitro models are available, but model characterization, including quantitative medication transport data across the in vitro blood-milk barrier, remains rather limited. Furthermore, animal in vivo models have been used successfully in the past. However, these models don't always mimic human physiology due to species-specific differences. Several efforts have been made to predict medication transfer into the milk based on physicochemical characteristics. However, the role of transporter proteins and several physiological factors (e.g., variable milk lipid content) are not accounted for by these methods. Physiologically-based pharmacokinetic (PBPK) modelling offers a mechanism-oriented strategy with bio-relevance. Recently, lactation PBPK models have been reported for some medications, showing at least the feasibility and value of PBPK modelling to predict transfer of medication into the human milk. However, reliable data as input for PBPK models is often missing. The iterative development of in vitro, animal in vivo and PBPK modelling methods seems to be a promising approach. Human in vitro models will deliver essential data on the transepithelial transport of medication, whereas the combination of animal in vitro and in vivo methods will deliver information to establish accurate in vitro/in vivo extrapolation (IVIVE) algorithms and mechanistic insights. Such a non-clinical platform will be developed and thoroughly evaluated by the Innovative Medicines Initiative ConcePTION.

Sequential Colocalization of ERa, PR, and AR Hormone Receptors Using Confocal Microscopy Enables New Insights into Normal Breast and Prostate Tissue and Cancers

Simple Summary

At present, platforms for multiplex immunohistochemistry (e.g., Opal) identify markers in distinct cell populations within a tissue section using multispectral fluorescence and optic microscopy. However, the optic resolution is not enough to colocalize markers at the subcellular level in the main epithelial or cancer population. We use confocal microscopy in multiplex detection of nuclear hormone receptors since they are an important part of the diagnosis and treatment of breast and prostate cancer. Moreover, we increased the quantitative dynamic range and resolution through increasing the signal/noise ration through reducing autofluorescence and increased longer antibody incubations. ColNu mIHCF identified distinct patterns of nuclear receptor colocalization in breast cancers. Furthermore, in prostate cancer all cancer epithelium was positive for ERa at the plasma membrane; and in normal prostate a small ERa+/p63+/AR− basal population suggest stem cell commitment to differentiation. ColNu mIHCF could be used for improving diagnosis and treatment in cancer.

Abstract

Multiplex immunohistochemistry (mIHC) use markers staining different cell populations applying widefield optical microscopy. Resolution is low not resolving subcellular co-localization. We sought to colocalize markers at subcellular level with antibodies validated for clinical diagnosis, including the single secondary antibody (combination of anti-rabbit/mouse-antibodies) used for diagnostic IHC with any primary antibody, and confocal microscopy. We explore colocalization in the nucleus (ColNu) of nuclear hormone receptors (ERa, PR, and AR) along with the baseline marker p63 in paired samples of breast and prostate tissues. We established ColNu mIHCF as a reliable technique easily implemented in a hospital setting. In ERa+ breast cancer, we identified different colocalization patterns (nuclear or cytoplasmatic) with PR and AR on the luminal epithelium. A triple-negative breast-cancer case expressed membrane-only ERa. A PR-only case was double positive PR/p63. In normal prostate, we identified an ERa+/p63+/AR-negative distinct population. All prostate cancer cases characteristically expressed ERa on the apical membrane of the AR+ epithelium. We confirmed this using ERa IHC and needle-core biopsies. ColNu mIHCF is feasible and already revealed a new marker for prostate cancer and identified sub-patterns in breast cancer. It could be useful for pathology as well as for functional studies in normal prostate and breast tissues.

Transcription Factors in Cancer Development and Therapy

Cancer is a multi-step process and requires constitutive expression/activation of transcription factors (TFs) for growth and survival. Many of the TFs reported so far are critical for carcinogenesis. These include pro-inflammatory TFs, hypoxia-inducible factors (HIFs), cell proliferation and epithelial-mesenchymal transition (EMT)-controlling TFs, pluripotency TFs upregulated in cancer stem-like cells, and the nuclear receptors (NRs). Some of those, including HIFs, Myc, ETS-1, and β-catenin, are multifunctional and may regulate multiple other TFs involved in various pro-oncogenic events, including proliferation, survival, metabolism, invasion, and metastasis. High expression of some TFs is also correlated with poor prognosis and chemoresistance, constituting a significant challenge in cancer treatment. Considering the pivotal role of TFs in cancer, there is an urgent need to develop strategies targeting them. Targeting TFs, in combination with other chemotherapeutics, could emerge as a better strategy to target cancer. So far, targeting NRs have shown promising results in improving survival. In this review, we provide a comprehensive overview of the TFs that play a central role in cancer progression, which could be potential therapeutic candidates for developing specific inhibitors. Here, we also discuss the efforts made to target some of those TFs, including NRs.

Transcription Factors in Cancer Development and Therapy

Cancer is a multi-step process and requires constitutive expression/activation of transcription factors (TFs) for growth and survival. Many of the TFs reported so far are critical for carcinogenesis. These include pro-inflammatory TFs, hypoxia-inducible factors (HIFs), cell proliferation and epithelial-mesenchymal transition (EMT)-controlling TFs, pluripotency TFs upregulated in cancer stem-like cells, and the nuclear receptors (NRs). Some of those, including HIFs, Myc, ETS-1, and β-catenin, are multifunctional and may regulate multiple other TFs involved in various pro-oncogenic events, including proliferation, survival, metabolism, invasion, and metastasis. High expression of some TFs is also correlated with poor prognosis and chemoresistance, constituting a significant challenge in cancer treatment. Considering the pivotal role of TFs in cancer, there is an urgent need to develop strategies targeting them. Targeting TFs, in combination with other chemotherapeutics, could emerge as a better strategy to target cancer. So far, targeting NRs have shown promising results in improving survival. In this review, we provide a comprehensive overview of the TFs that play a central role in cancer progression, which could be potential therapeutic candidates for developing specific inhibitors. Here, we also discuss the efforts made to target some of those TFs, including NRs.

CDH2/N-cadherin and early diagnosis of invasion in patients with ductal carcinoma in situ

PURPOSE

This proof-of-concept study investigates gene expression in core needle biopsies (CNB) to predict whether individuals diagnosed with ductal carcinoma in situ (DCIS) on CNB were affected by invasion at the time of diagnosis.

METHODS

Using a QuantiGene Plex 2.0 assay, 14 gene expression profiling was performed in 303 breast tissue samples. Preoperative diagnostic performance of a gene was measured by area under receiver-operating characteristic curve (AUC) with 95% confidence interval (CI). The gene mRNA positivity cutoff was computed using Gaussian mixture model (GMM); protein expression was measured by immunohistochemistry; DNA methylation was evaluated by targeted bisulfite sequencing.

RESULTS

mRNA from 69% (34/49) mammoplasties, 72% (75/104) CNB DCIS, and 89% (133/150) invasive breast cancers (IBC) were analyzed. Based on pre-and post-surgery DCIS chart reviews, 21 cases were categorized as DCIS synchronous with invasion and 54 DCIS were pure DCIS without pathologic evidence of invasive disease. The ectopic expression of neuronal cadherin CDH2 was probable in 0% mammoplasties, 6% pure DCIS, 29% synchronous DCIS, and 26% IBC. The CDH2 mRNA positivity in preoperative biopsies showing pure DCIS was predictive of a final diagnosis of invasion (AUC = 0.67; 95% CI 0.53-0.80; P = 0.029). Site-specific methylation of the CDH2 promoter (AUC = 0.76; 95% CI 0.54-0.97; P = 0.04) and measurements of N-cadherin, a pro-invasive cell-cell adhesion receptor encoded by CDH2 (AUC = 0.8; 95% CI 0.66-0.99; P < 0.005) had a discriminating power allowing for discernment of CDH2-positive biopsy.

CONCLUSIONS

Evidence of CDH2/N-cadherin expression, predictive of invasion synchronous with DCIS, may help to clarify a diagnosis and direct the course of therapy earlier in a patient's care.

Reciprocal fine-tuning of progesterone and prolactin-regulated gene expression in breast cancer cells

Progesterone and prolactin are two key hormones involved in development and remodeling of the mammary gland. As such, both hormones have been linked to breast cancer. Despite the overlap between biological processes ascribed to these two hormones, little is known about how co-expression of both hormones affects their individual actions. Progesterone and prolactin exert many of their effects on the mammary gland through activation of gene expression, either directly (progesterone, binding to the progesterone receptor [PR]) or indirectly (multiple transcription factors being activated downstream of prolactin, most notably STAT5). Using RNA-seq in T47D breast cancer cells, we characterized the gene expression programs regulated by progestin and prolactin, either alone or in combination. We found significant crosstalk and fine-tuning between the transcriptional programs executed by each hormone independently and in combination. We divided and characterized the transcriptional programs into four broad categories. All crosstalk/fine-tuning shown to be modulated by progesterone was dependent upon the expression of PR. Moreover, PR was recruited to enhancer regions of all regulated genes. Interestingly, despite the canonical role for STAT5 in transducing prolactin-signaling in the normal and lactating mammary gland, very few of the prolactin-regulated transcriptional programs fine-tuned by progesterone in this breast cancer cell line model system were in fact dependent upon STAT5. Cumulatively, these data suggest that the interplay of progesterone and prolactin in breast cancer impacts gene expression in a more complex and nuanced manner than previously thought, and likely through different transcriptional regulators than those observed in the normal mammary gland. Studying gene regulation when both hormones are present is most clinically relevant, particularly in the context of breast cancer.

90 YEARS OF PROGESTERONE: Molecular mechanisms of progesterone receptor action on the breast cancer genome

Gene regulation by steroid hormones has been at the forefront in elucidating the intricacies of transcriptional regulation in eukaryotes ever since the discovery by Karlson and Clever that the insect steroid hormone ecdysone induces chromatin puffs in giant chromosomes. After the successful cloning of the hormone receptors toward the end of the past century, detailed mechanistic insight emerged in some model systems, in particular the MMTV provirus. With the arrival of next generation DNA sequencing and the omics techniques, we have gained even further insight into the global cellular response to steroid hormones that in the past decades also extended to the function of the 3D genome topology. More recently, advances in high resolution microcopy, single cell genomics and the new vision of liquid-liquid phase transitions in the context of nuclear space bring us closer than ever to unravelling the logic of gene regulation and its complex integration of global cellular signaling networks. Using the function of progesterone and its cellular receptor in breast cancer cells, we will briefly summarize the history and describe the present extent of our knowledge on how regulatory proteins deal with the chromatin structure to gain access to DNA sequences and interpret the genomic instructions that enable cells to respond selectively to external signals by reshaping their gene regulatory networks.

Metronomic chemotherapy combined with endocrine therapy: are we challenging some dogmas?

INTRODUCTION

Metronomic chemotherapy exerts its effects via inhibition of angiogenesis, immune modulation of the tumoral stroma, induction of senescence and apoptosis of tumor cells. Due to its favorable toxicity profile and its oral administration, metronomic chemotherapy arises as a promising alternative to be combined with endocrine therapy for the treatment of patients with luminal breast cancer.

AREAS COVERED

The present manuscript reviews the rationale supporting the combination of metronomic chemotherapy and endocrine therapy, discussing the studies that evaluated this regimen in the treatment of early-stage and metastatic breast cancer patients. Finally, we conclude by providing an expert opinion on the current role and perspectives for the combination of metronomic chemotherapy and endocrine therapy in the management of patients with luminal breast cancer.

EXPERT OPINION

Retrospective series and early-phase clinical trials have shown promising signs of activity and a favorable toxicity profile with this regimen, which warrants further investigation as a treatment option for luminal breast cancer patients.

Long non-coding NR2F1-AS1 is associated with tumor recurrence in estrogen receptor-positive breast cancers

The tenacity of late recurrence of estrogen receptor (ER)‐positive breast cancer remains a major clinical issue to overcome. The administration of endocrine therapies within the first 5 years substantially minimizes the risk of relapse; however, some tumors reappear 10–20 years after the initial diagnosis. Accumulating evidence has strengthened the notion that long noncoding RNAs (lncRNAs) are associated with cancer in various respects. Because lncRNAs may display high tissue/cell specificity, we hypothesized this might provide new insights to tumor recurrence. By comparing transcriptome profiles of 24 clinical primary tumors obtained from patients who developed distant metastases and patients with no signs of recurrence, we identified lncRNA NR2F1‐AS1 whose expression was associated with tumor recurrence. We revealed the relationship between NR2F1‐AS1 and the hormone receptor expressions in ER‐positive breast cancer cells. Gain of function of NR2F1‐AS1 steered cancer cells into quiescence‐like state by the upregulation of dormancy inducers and pluripotency markers, and activates representative events of the metastatic cascade. Our findings implicated NR2F1‐AS1 in the dynamics of tumor recurrence in ER‐positive breast cancers and introduce a new biomarker that holds a therapeutic potential, providing favorable prospects to be translated into the clinical field.

ERα-36 regulates progesterone receptor activity in breast cancer

Background

Alterations in estrogen and progesterone signaling, via their respective receptors, estrogen receptor alpha (ERα) and progesterone receptor (PR), respectively, are largely involved in the development of breast cancer (BC). The recent identification of ERα-36, a splice variant of ERα, has uncovered a new facet of this pathology. Although ERα-36 expression is associated with poor prognosis, metastasis development, and resistance to treatment, its predictive value has so far not been associated with a BC subtype and its mechanisms of action remain understudied.

Methods

To study ERα-36 expression in BC specimens, we performed immunochemical experiments. Next, the role of ERα-36 in progesterone signaling was investigated by generating KO clones using the CRISPR/CAS9 technology. PR signaling was also assessed by proximity ligation assay, Western blotting, RT-QPCR, and ChIP experiments. Finally, proliferation assays were performed with the IncuCyte technology and migration experiments using scratch assays.

Results

Here, we demonstrate that ERα-36 expression at the plasma membrane is correlated with a reduced disease-free survival in a cohort of 160 BC patients, particularly in PR-positive tumors, suggesting a crosstalk between ERα-36 and PR. Indeed, we show that ERα-36 interacts constitutively with PR in the nucleus of tumor cells. Moreover, it regulates PR expression and phosphorylation on key residues, impacting the biological effects of progesterone.

Conclusions

ERα-36 is thus a regulator of PR signaling, interfering with its transcriptional activity and progesterone-induced anti-proliferative effects as well as migratory capacity. Hence, ERα-36 may constitute a new prognostic marker as well as a potential target in PR-positive BC.

The glucocorticoid receptor interferes with progesterone receptor-dependent genomic regulation in breast cancer cells

The glucocorticoid and progesterone receptors (GR and PR) are closely related members of the steroid receptor family. Despite sharing similar structural and functional characteristics; the cognate hormones display very distinct physiological responses. In mammary epithelial cells, PR activation is associated with the incidence and progression of breast cancer, whereas the GR is related to growth suppression and differentiation. Despite their pharmacological relevance, only a few studies have compared GR and PR activities in the same system. Using a PR⁺/GR⁺ breast cancer cell line, here we report that either glucocorticoid-free or dexamethasone (DEX)-activated GR inhibits progestin-dependent gene expression associated to epithelial-mesenchymal-transition and cell proliferation. When both receptors are activated with their cognate hormones, PR and GR can form part of the same complex according to co-immunoprecipitation, quantitative microscopy and sequential ChIP experiments. Moreover, genome-wide studies in cells treated with either DEX or R5020, revealed the presence of several regions co-bound by both receptors. Surprisingly, GR also binds novel genomic sites in cells treated with R5020 alone. This progestin-induced GR binding was enriched in REL DNA motifs and located close to genes coding for chromatin remodelers. Understanding GR behavior in the context of progestin-dependent breast cancer could provide new targets for tumor therapy.

Anti-proliferative transcriptional effects of medroxyprogesterone acetate in estrogen receptor positive breast cancer cells are predominantly mediated by the progesterone receptor

Medroxyprogesterone acetate (MPA) is a first generation progestin that has been in clinical use for various hormonal conditions in women since the 1960s. Although developed as a progesterone receptor (PR) agonist, MPA also has strong binding affinity for other steroid receptors. This promiscuity confounds the mechanistic action of MPA in target cells that express multiple steroid receptors. This study is the first to assess the relative contribution of progesterone, androgen and glucocorticoid receptors in mediating the transcriptional activity of MPA on endogenous targets in breast cancer cells that endogenously express all three receptors at comparable levels. Gene expression profiling in estrogen receptor positive (ER+) ZR-75-1 breast cancer cells demonstrated that although the MPA-regulated transcriptome strongly overlapped with that of Progesterone (PROG), 5α-dihydrotestosterone (DHT) and Dexamethasone (DEX), it clustered most strongly with that of PROG, suggesting that MPA predominantly acts via the progesterone receptor (PR) rather than androgen receptor (AR) or glucocorticoid receptor (GR). Subsequent experiments manipulating levels of these receptors, either through specific culture conditions or with lentiviral shRNAs targeting individual receptors, also revealed a stronger contribution of PR compared to AR and GR on the expression of endogenous target genes that are either commonly regulated by all ligands or specifically regulated only by MPA. A predominant contribution of PR to MPA action in ER+ T-47D breast cancer cells was also observed, although a stronger role for AR was evident in T-47D compared to that observed in ZR-75-1 cells. Network analysis of ligand-specific and commonly regulated genes demonstrated that MPA utilises different transcription factors and signalling pathways to inhibit proliferation compared with PROG. This study reaffirms the importance of PR in mediating MPA action in an endogenous breast cancer context where multiple steroid receptors are co-expressed and has potential implications for PR-targeting therapeutic strategies in ER+ breast cancer.

Breast cancer: Biology, biomarkers, and treatments

During the past recent years, various therapies emerged in the era of breast cancer. Breast cancer is a heterogeneous disease in which genetic and environmental factors are involved. Breast cancer stem cells (BCSCs) are the main player in the aggressiveness of different tumors and also, these cells are the main challenge in cancer treatment. Moreover, the major obstacle to achieve an effective treatment is resistance to therapies. There are various types of treatment for breast cancer (BC) patients. Therefore, in this review, we present the current treatments, novel approaches such as antibody-drug conjugation systems (ADCs), nanoparticles (albumin-, metal-, lipid-, polymer-, micelle-based nanoparticles), and BCSCs-based therapies. Furthermore, prognostic and predictive biomarkers will be discussed also biomarkers that have been applied by some tests such as Oncotype DX, Mamm αPrint, and uPA/PAI-1 are regarded as suitable prognostic and predictive factors in breast cancer.

Baicalein Is a Phytohormone that Signals Through the Progesterone and Glucocorticoid Receptors

While flavonoids have been studied extensively for estrogen receptor activity, they have not been well studied for their ability to modify progesterone receptor (PR) and glucocorticoid receptor (GR) signaling. Three flavonoid compounds, tangeretin, wogonin, and baicalein, were selected for testing for PR and GR activity based on their structural similarity to known phytoprogesterone-like compounds. Each compound was docked in the binding pocket of PR and GR. Of these compounds, baicalein was predicted to be most likely to bind to both receptors. A fluorescence polarization competitive binding assay for PR and GR confirmed that baicalein binds to both the PR and GR with IC₅₀ values of 15.30 μM and 19.26 μM, respectively. In Ishikawa PR-B and T47D cells, baicalein acted as a PR antagonist in a hormone response element (HRE) luciferase (Luc) assay. In OVCAR5 cells, which only express GR, baicalein was a GR agonist via an HRE/Luc assay and induced GR target genes, FKBP5 and GILZ. RU486, a PR and GR antagonist, abrogated baicalein's activity in OVCAR5 cells, confirming baicalein's activity is mediated through the GR. In vivo, baicalein administered intraperitoneally to female mice twice a week for 4 weeks at a dose of 25 mg/kg induced the GR target gene GILZ in the reproductive tract, which was blocked by RU486. In summary, baicalein has PR antagonist and GR agonist activity in vitro and demonstrates GR agonist activity in the uterus in vivo.

Sex steroid hormone function in the brain niche: Implications for brain metastatic colonization and progression

BACKGROUND

While sex hormones and their receptors play well-known roles in progression of primary tumors through direct action on sex steroid hormone-responsive cancer cells, emerging evidence suggest that hormones also play important roles in metastatic progression by modulating the tumor microenvironment. Estrogens and androgens synthesized in gonads and within the brain influence memory, behavior, and outcomes of brain pathologies. Yet, their impact on brain metastatic colonization and progression is just beginning to be explored.

RECENT FINDINGS

Estradiol and testosterone cross the blood-brain barrier and are synthesized de novo in astrocytes and other cells within the adult brain. Circulating and brain-synthesized estrogens have been shown to promote brain metastatic colonization of tumors lacking estrogen receptors (ERs), through mechanisms involving the upregulation of growth factors and neurotrophins in ER+ reactive astrocytes. In this review, we discuss additional mechanisms by which hormones may influence brain metastases, through modulation of brain endothelial cells, astrocytes, and microglia.

CONCLUSION

A greater understanding of hormone-brain-tumor interactions may shed further light on the mechanisms underlying the adaptation of cancer cells to the brain niche, and provide therapeutic alternatives modulating the brain metastatic niche.

Non-clinical Models to Determine Drug Passage into Human Breast Milk

BACKGROUND

Successful practice of clinical perinatal pharmacology requires a thorough understanding of the pronounced physiological changes during lactation and how these changes affect various drug disposition processes. In addition, pharmacokinetic processes unique to lactation have remained understudied. Hence, determination of drug disposition mechanisms in lactating women and their babies remains a domain with important knowledge gaps. Indeed, lack of data regarding infant risk during breastfeeding far too often results in discontinuation of breastfeeding and subsequent loss of all the associated benefits to the breastfed infant. In the absence of age-specific toxicity data, human lactation data alone are considered insufficient to rapidly generate the required evidence regarding risks associated with medication use during lactation.

METHODS

Systematic review of literature to summarize state-of-the art non-clinical approaches that have been developed to explore the mechanisms underlying drug milk excretion.

RESULTS

Several studies have reported methods to predict (to some extent) milk drug excretion rates based on physicochemical properties of the compounds. In vitro studies with primary mammary epithelial cells appear excellent approaches to determine transepithelial drug transport rates across the mammary epithelium. Several of these in vitro tools have been characterized in terms of transporter expression and activity as compared to the mammary gland tissue. In addition, with the advent of physiology-based pharmacokinetic (PBPK) modelling, these in vitro transport data may prove instrumental in predicting drug milk concentration time profiles prior to the availability of data from clinical lactation studies. In vivo studies in lactating animals have proven their utility in elucidating the mechanisms underlying drug milk excretion.

CONCLUSION

By combining various non-clinical tools (physicochemistry-based, in vitro and PBPK, in vivo animal) for drug milk excretion, valuable and unique information regarding drug milk concentrations during lactation can be obtained. The recently approved IMI project ConcePTION will address several of the challenges outlined in this review.

Progesterone Receptor Gene Variants in Metastatic Estrogen Receptor Positive Breast Cancer

Tumor mutations in the gene encoding estrogen receptor alpha (ESR1) have been identified in metastatic breast cancer patients with endocrine therapy resistance. However, relatively little is known about the occurrence of mutations in the progesterone receptor (PGR) gene in this population. The study objective was to determine the frequency and prognostic significance of tumor PGR mutations for patients with estrogen receptor (ER)-positive metastatic breast cancer. Thirty-five women with metastatic or locally recurrent ER+ breast cancer were included in this IRB-approved, retrospective study. Targeted next-generation sequencing of the PGR gene was performed on isolated tumor DNA. Associations between mutation status and clinicopathologic factors were analyzed as well as overall survival (OS) from time of metastatic diagnosis. The effect of the PGR variant Y890C (c.2669A>G) identified in this cohort on PR transactivation function was tested using ER-PR- (MDA-MB-231), ER+PR+ (T47D), and ER+PR- (T47D PR KO) breast cancer cell lines. There were 71 occurrences of protein-coding PGR variants in 67% (24/36; 95% CI 49-81%) of lesions. Of the 49 unique variants, 14 are single nucleotide polymorphisms (SNPs). Excluding SNPs, the median OS of patients with PGR variants was 32 months compared to 79 months with wild-type PGR (p = 0.42). The most frequently occurring (4/36 lesions) non-SNP variant was Y890C. Cells expressing Y890C had reduced progestin-stimulated PR transactivation compared to cells expressing wild-type PR. PGR variants occur frequently in ER+ metastatic breast cancer. Although some variants are SNPs, others are predicted to be functionally deleterious as demonstrated with Y890C PR.

Association of polymorphisms in LOC105377871 and CASC16 with breast cancer in the northwest Chinese Han population

BACKGROUND

Breast cancer represents the cancer with the highest incidence and mortality among women in the world, and its pathogenesis is complex. Single nucleotide polymorphisms (SNPs) are one of the factors that influence the risk of breast cancer. The present study aimed to investigate the effects of LOC105377871 and CASC16 polymorphisms on the risk of breast cancer in the northwest Chinese Han population.

METHODS

We selected 503 breast cancer patients and 503 healthy controls for the present study. Genotyping was performed using the Agena MassARRAY system (Agenea Bioscience, San Diego, CA, USA) and we evaluated the association between SNPs (rs17530068 and rs4784227) and the risk of breast cancer in four genetic models. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

It was found that the rs17530068 increased the breast cancer risk in log-additive model (p = 0.047, OR = 1.23, 95% CI = 1.00-1.50). After stratification, the "T" allele of rs4784227 increased the risk of lymph node metastasis in breast cancer patients (allele: p = 0.025, OR = 1.51, 95% CI = 1.05-2.17; codominant model: p = 0.008, OR = 1.99, 95% CI = 1.20-3.31; dominant model: p = 0.008, OR = 1.94, 95% CI = 1.19-3.16; log-additive model: p = 0.023, OR = 1.52, 95% CI = 1.06-2.19).

CONCLUSIONS

The results of the present study show that, in the northwest Chinese Han population, SNP rs17530068 (LOC105377871) increases the risk of breast cancer and SNP rs4784227 (CASC16) promotes lymph node metastasis in breast cancer patients.

Rapid and structure-specific cellular uptake of selected steroids

Steroid hormones and their respective nuclear receptors are essential mediators in numerous physiologic and pathophysiologic processes, ranging from regulation of metabolism, immune function, and reproductive processes to the development of hormone-dependent cancers such as those of the breast and prostate. Because steroids must enter cells before activating nuclear receptors, understanding the mechanisms by which cellular uptake occurs is critical, yet a clear understanding of these mechanisms has been elusive. It is generally assumed that diffusion-driven uptake is similar across various steroids whereas an elevated cellular concentration is thought to reflect active uptake, but these assumptions have not been directly tested. Here we show that intact cells rapidly accumulate free steroids to markedly elevated concentrations. This effect varies widely depending on steroid structure; more lipophilic steroids reach more elevated concentrations. Strong preferences exist for 3β-OH, Δ⁵-steroids vs. 3-keto, Δ⁴-structural features and for progestogens vs. androgens. Surprisingly, steroid-structure-specific preferences do not require cell viability, implying a passive mechanism, and occur across cells derived from multiple tissue types. Physiologic relevance is suggested by structure-specific preferences in human prostate tissue compared with serum. On the other hand, the presence of serum proteins in vitro blocks much, but not all, of the passive accumulation, while still permitting a substantial amount of active accumulation for certain steroids. Our findings suggest that both passive and active uptake mechanisms make important contributions to the cellular steroid uptake process. The role of passive, lipophilicity-driven accumulation has previously been largely unappreciated, and its existence provides important context to studies on steroid transport and action both in vitro and in vivo.