Epigenetic mechanisms regulating CYP19 transcription in human breast adipose fibroblasts

DNA Methylation Profiling of Ovarian Tissue of Climbing Perch (Anabas testudienus) in Response to Monocrotophos Exposure

Epigenetic modifications like DNA methylation can alter an organism's phenotype without changing its DNA sequence. Exposure to environmental toxicants has the potential to change the resilience of aquatic species. However, little information is available on the dynamics of DNA methylation in fish gonadal tissues in response to organophosphates. In the present work, reduced-representation bisulfite sequencing was performed to identify DNA methylation patterns in the ovarian tissues of Anabas testudienus exposed to organophosphates, specifically monocrotophos (MCP). Through sequencing, an average of 41,087 methylated cytosine sites were identified and distributed in different parts of genes, i.e., in transcription start sites (TSS), promoters, exons, etc. A total of 1058 and 1329 differentially methylated regions (DMRs) were detected as hyper-methylated and hypo-methylated in ovarian tissues, respectively. Utilizing whole-genome data of the climbing perch, the DMRs, and their associated overlapping genes revealed a total of 22 genes within exons, 45 genes at transcription start sites (TSS), and 218 genes in intergenic regions. Through gene ontology analysis, a total of 16 GO terms particularly involved in ovarian follicular development, response to oxidative stress, oocyte maturation, and multicellular organismal response to stress associated with reproductive biology were identified. After functional enrichment analysis, relevant DMGs such as steroid hormone biosynthesis (Cyp19a, 11-beta-HSD, 17-beta-HSD), hormone receptors (ar, esrrga), steroid metabolism (StAR), progesterone-mediated oocyte maturation (igf1ar, pgr), associated with ovarian development in climbing perch showed significant differential methylation patterns. The differentially methylated genes (DMGs) were subjected to analysis using real-time PCR, which demonstrated altered gene expression levels. This study revealed a molecular-level alteration in genes associated with ovarian development in response to chemical exposure. This work provides evidence for understanding the relationship between DNA methylation and gene regulation in response to chemicals that affect the reproductive fitness of aquatic animals.

DNA methylation mediates gonadal development via regulating the expression levels of cyp19a1a in loach Misgurnus anguillicaudatus

DNA methylation-mediated transcriptional regulation has been considered to significantly impact some steroidogenic enzyme genes expression. To uncover the roles of DNA methylation on the regulation of aromatase gene expression during gametogenesis in Misgurnus anguillicaudatus, the expression profiles and cellular localization of cyp19a1a and cyp19a1b were analyzed, and the landscape of DNA methylation dynamics was investigated. We found that cyp19a1a was predominantly expressed in granulosa cells of oocytes, while cyp19a1b expression was enriched in radial glial cells of the forebrain. In ovary, cyp19a1a was highly expressed until the vitellogenesis stage. The average methylation levels, especially for two CpG sites within the cAMP response element, were negatively correlated with cyp19a1a expression levels, indicating that methylation could regulate cyp19a1a transcriptional activity by modulating the binding efficiency of cAMP to its response elements. Compared with in ovary, cyp19a1a showed lower expression in testis but was hypermethylated. Cyp19a1b in female brain weakly expressed before the vitellogenesis stage, but significantly elevated at the maturation stage. In both sexes, it maintained high methylation levels in brain despite the obvious fluctuation of the cyp19a1b expression. This study revealed that DNA methylation plays a key role in establishing cyp19a1a spatiotemporal expression patterns and thus mediates gonadal development in teleosts.

Expression and DNA methylation analysis of cyp19a1a in Chinese sea perch Lateolabrax maculatus

Cytochrome P450 aromatase (P450arom), which is encoded by cyp19a1a, can convert androgen to estrogen. Therefore, P450arom is important in gonadal differentiation and maintenance. In this study, we analyzed the expression and DNA methylation of cyp19a from Chinese sea perch Lateolabrax maculatus (sp. cyp19a1a). The sp. cyp19a1a gene consists of 9 exons, but only 3.5 kb, being smaller than the human cyp19a1a, as a result of small introns. The sp. cyp19a1a protein contains 518 amino acid residues and evolutionarily conserved domains and is clustered in the teleost subfamily on the phylogenetic tree. Amino acid alignment indicates that sp. cyp19a1a shares the highest identity (91.6%) to Epinephelus akaara and Lates calcarifer. Endogenous sp. cyp19a1a is detected mainly in stromal cells around the oocytes of stage I ovary, and the gene expression level has no difference after 40 days fresh water culture in both ovary and testis. The sp. Cyp19a1a can catalyze the production of estrogen from androgen in vitro. Seven CpG dinucleotides are found in the proximal promoter. Binding sites of the conserved predicted transcription factors include cAMP response element, steroidogenic factor-1, and SRY-Box. The deletion of this region reduces promoter activity significantly. The methylation level of the seven CpG dinucleotides in cyp19a1a promoter is higher in the testis (44.25 ± 4.04) than in the ovary (24.71 ± 3.05). The induced hypermethylation of the sp. cyp19a1a promoter suppressed promoter transcription function in vitro. These results suggest that DNA methylation may be a mechanism used for natural sex maintenance.

Effects of Neonicotinoid Pesticides on Promoter-Specific Aromatase (CYP19) Expression in Hs578t Breast Cancer Cells and the Role of the VEGF Pathway

BACKGROUND

Aromatase (CYP19) is a key enzyme in estrogens biosynthesis. In the mammary gland, CYP19 gene is expressed at low levels under the regulation of its I.4 promoter. In hormone-dependent breast cancer, fibroblast cells surrounding the tumor express increased levels of CYP19 mRNA due to a decrease of I.4 promoter activity and an increase of PII, I.3, and I.7 promoter activity. Little is known about the effects of environmental chemicals on the promoter-specific CYP19 expression.

OBJECTIVE

We aimed to determine the effects of two neonicotinoids (thiacloprid and imidacloprid) on promoter-specific CYP19 expression in Hs578t breast cancer cells and understand the signaling pathways involved.

METHODS

Hs578t cells were exposed to various signaling pathway stimulants or neonicotinoids for 24 h. Promoter-specific expression of CYP19 was determined by real-time quantitative polymerase chain reaction and catalytic activity of aromatase by tritiated water release assay.

RESULTS

To our knowledge, we are the first to demonstrate that the normal I.4 promoter and the breast cancer-relevant PII, I.3, and I.7 promoters of CYP19 are active in these cells. We found that the expression of CYP19 via promoters PII, I.3, and I.7 in Hs578t cells was, in part, dependent on the activation of two VEGF signaling pathways: mitogen-activated protein kinase (MAPK) 1/3 and phospholipase C (PLC). Exposure of Hs578t cells to environmental concentrations of imidacloprid and thiacloprid resulted in a switch in CYP19 promoter usage, involving inhibition of I.4 promoter activity and an increase of PII, I.3, and I.7 promoter-mediated CYP19 expression and aromatase catalytic activity. Greater effects were seen at lower concentrations. Our results suggest that thiacloprid and imidacloprid exert their effects at least partially by inducing the MAPK 1/3 and/or PLC pathways.

CONCLUSIONS

We demonstrated in vitro that neonicotinoids may stimulate a change in CYP19 promoter usage similar to that observed in patients with hormone-dependent breast cancer. https://doi.org/10.1289/EHP2698.

Methylation dictates PI.f-specific CYP19 transcription in human glial cells

CYP19 is the single copy gene encoding for the estrogen synthetic enzyme aromatase. Alternate splicing of the promoter is the regulatory mechanism of this gene. In the brain, estrogen is synthesized in neuronal and glial cells and the gene is mainly regulated by the alternate promoter PI.f. The hormone produced in this vicinity has been associated with maintaining normal brain functions. Previously, epigenetic regulation has been shown in the promoters PII and I.3 of CYP19 in adipocytes. In the present study, the methylation of PI.f in CYP19 was examined in glial cells. Treatment of the hypomethylating agent 5-aza-2'deoxycytidine increased CYP19 mRNA species in U87 MG cells while little changes were observed in the other glia cell lines. As PI.f is also chiefly used in T98G cells with high expression of CYP19, the methylation statuses of the promoter in these two cell models were compared. Our results showed that treating U87 MG cells with 10 μM 5-aza-2'deoxycytidine significantly induced a ∼10-fold increase in CYP19 transcription and ∼80% increase in aromatase activity. In contrast, the same treatment did not change either endpoint in T98G cells. Further investigation illustrated the CpGs in PI.f were differentially methylated in the two cell lines; 63% and 37% of the 14 CpG sites were methylated in U87 MG and T98G cells respectively. In conclusion, this study illustrated that the brain-specific PI.f derived CYP19 expression can be regulated by DNA methylation.

Transposable Elements in Human Cancer: Causes and Consequences of Deregulation

Transposable elements (TEs) comprise nearly half of the human genome and play an essential role in the maintenance of genomic stability, chromosomal architecture, and transcriptional regulation. TEs are repetitive sequences consisting of RNA transposons, DNA transposons, and endogenous retroviruses that can invade the human genome with a substantial contribution in human evolution and genomic diversity. TEs are therefore firmly regulated from early embryonic development and during the entire course of human life by epigenetic mechanisms, in particular DNA methylation and histone modifications. The deregulation of TEs has been reported in some developmental diseases, as well as for different types of human cancers. To date, the role of TEs, the mechanisms underlying TE reactivation, and the interplay with DNA methylation in human cancers remain largely unexplained. We reviewed the loss of epigenetic regulation and subsequent genomic instability, chromosomal aberrations, transcriptional deregulation, oncogenic activation, and aberrations of non-coding RNAs as the potential mechanisms underlying TE deregulation in human cancers.

Dynamic methylation pattern of cyp19a1a core promoter during zebrafish ovarian folliculogenesis

In vertebrates, the aromatase coded by the cyp19a1a gene can catalyze the conversion from androgens to estrogens. Thus, the regulatory mechanisms of cyp19a1a gene expression are a critical research field in reproductive endocrinology. In this study, we use zebrafish as a model to study the dynamic methylation levels of the cyp19a1a gene core promoter during zebrafish ovarian folliculogenesis. The results show that there is an apparent fluctuation of the methylation levels of zebrafish cyp19a1a core promoter. Moreover, the methylation levels are inversely correlated with the expression levels of cyp19a1a transcripts when the ovarian follicles develop from PV into the MV stage. Also, the CpG dinucleotides which are close to the transcriptional starting site may have provided a significant blocking effect on inhibiting the transcriptional function of RNA polymerase II. Taken together, the results from the present study strongly suggest that DNA methylation was one of mechanisms that are involved in the regulation of cyp19a1a gene expression during folliculogenesis. This methylation mechanism modifying transcriptional process accompanied with zebrafish ovarian folliculogenesis might also shed new light on the regulation of cyp19a1a expression during the ovarian developmental stage in other vertebrates.

Epigenetic regulation of bovine spermatogenic cell-specific gene boule

Non-primate mammals have two deleted azoospermia (DAZ) family genes, DAZL and Boule; genes in this family encode RNA-binding proteins essential for male fertility in diverse animals. Testicular DAZL transcription is regulated by epigenetic factors such as DNA methylation. However, nothing is known about the epigenetic regulation of Boule. Here, we explored the role of DNA methylation in the regulation of the bovine Boule (bBoule) gene. We found that a long CpG island (CGI) in the bBoule promoter was hypermethylated in the testes of cattle-yak hybrids with low bBoule expression, whereas cattle had relatively low methylation levels (P < 0.01), and there was no difference in the methylation level in the short CGI of the gene body between cattle and cattle-yak hybrids (P > 0.05). We identified a 107 bp proximal core promoter region of bBoule. Intriguingly, the differences in the methylation level between cattle and cattle-yak hybrids were larger in the core promoter than outside the core promoter. An in vitro methylation assay showed that the core promoter activity of bBoule decreased significantly after M.SssI methylase treatment (P < 0.01). We also observed dramatically increased bBoule transcription in bovine mammary epithelial cells (BMECs) after treatment with the methyltransferase inhibitor 5-Aza-dC. Taken together, our results establish that methylation status of the core promoter might be involved in testicular bBoule transcription, and may provide new insight into the epigenetic regulation of DAZ family genes and clinical insights regarding male infertility.

Transcriptional control of local estrogen formation by aromatase in the breast

Aromatase is the critical enzyme that converts androgens to estrogens. It is frequently highly expressed in the tumour bearing breast of women diagnosed with estrogen receptor positive tumours, resulting in dramatically increased local estrogen production to drive tumour progression. Expression of aromatase is regulated primarily at the transcriptional level of its encoding gene CYP19A1, located on chromosome 15 of the human genome. A characteristic feature of CYP19A1 expression is its use of alternative promoters to regulate transcription in a tissue-specific manner. In breast cancer, the increase in aromatase expression is mediated via higher expression of the distal adipose-specific promoter I.4 and a switch to the preferential use of proximal promoters I.3 and II. This results in a net increase of CYP19A1 transcripts in tumour-bearing breast up to 3-4-fold higher than normal breast. Current aromatase inhibitors - whilst efficacious - exhibit significant side effects that reduce patient compliance. Understanding the transcription factors and signalling pathways that control aromatase expression will lead to opportunities to develop breast-specific inhibitors with an improved side-effects profile. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Genes encoding aromatases in teleosts: evolution and expression regulation

Cytochrome P450 aromatases, encoded by cyp19a1 genes, catalyzes the conversion of androgens to estrogens and plays important roles in the reproduction of vertebrates. Vertebrate cyp19a1 genes showed high synteny in chromosomal locations and conservation in sequences during evolution. However, amphioxus cyp19a1 does not show synteny to vertebrate cyp19a1. Teleost fish possess two copies of the cyp19a1 gene, which were postulated to result from a fish-specific genome duplication. The duplicated copies of fish cyp19a1 genes evolved into the brain and ovarian forms of cytochrome P450 aromatase genes, cyp19a1a and cyp19a1b, respectively, with different regulatory mechanisms of expression, through subfunctionalization under long-term selective pressure. In addition to the estradiol (E2) auto-regulatory loop, there may be other mechanisms responsible for the high expression of aromatase in the teleost brain. The study of the two cyp19a1 copies in teleost fish will shed light on the general evolution, function, and regulation of vertebrate cyp19a1.

Endocrine disruption of the epigenome: a breast cancer link

The heritable component of breast cancer accounts for only a small proportion of total incidences. Environmental and lifestyle factors are therefore considered to among the major influencing components increasing breast cancer risk. Endocrine-disrupting chemicals (EDCs) are ubiquitous in the environment. The estrogenic property of EDCs has thus shown many associations between ongoing exposures and the development of endocrine-related diseases, including breast cancer. The environment consists of a heterogenous population of EDCs and despite many identified modes of action, including that of altering the epigenome, drawing definitive correlations regarding breast cancer has been a point of much discussion. In this review, we describe in detail well-characterized EDCs and their actions in the environment, their ability to disrupt mammary gland formation in animal and human experimental models and their associations with exposure and breast cancer risk. We also highlight the susceptibility of early-life exposure to each EDC to mediate epigenetic alterations, and where possible describe how these epigenome changes influence breast cancer risk.

Activation of endocrine-related gene expression in placental choriocarcinoma cell lines following DNA methylation knock-down

Increasingly, placental DNA methylation is assessed as a factor in pregnancy-related complications, yet the transcriptional impact of such findings is not always clear. Using a proliferative in vitro placental model, the effect of DNA methylation loss on gene activation was evaluated at a number of genes selected for being differentially methylated in pre-eclampsia-associated placentae in vivo. We aimed to determine whether reduced DNA methylation at specific loci was associated with transcriptional changes at the corresponding gene, thus providing mechanistic underpinnings for previous clinical findings and to assess the degree of transcriptional response amongst our candidate genes. BeWo and JEG3 choriocarcinoma cells were exposed to 1 μM 5-Aza-2'-deoxycytidine (5-Aza-CdR) or vehicle control for 48 h, and re-plated and cultured for a further 72 h in normal media before cells were harvested for RNA and DNA. Bisulphite pyrosequencing confirmed that DNA methylation was reduced by ∼30-50% points at the selected loci studied in both cell lines. Gene activation, measured by qRT-PCR, was highly variable and transcript specific, indicating differential sensitivity to DNA methylation. Most notably, loss of DNA methylation at the leptin (LEP) promoter corresponded to a 200-fold and 40-fold increase in LEP expression in BeWo and JEG3 cells, respectively (P < 0.01). Transcripts of steroidogenic pathway enzymes CYP11A1 and HSD3B1 were up-regulated ∼40-fold in response to 5-Aza-CdR exposure in BeWo cells (P < 0.01). Other transcripts, including aromatase (CYP19), HSD11B2, inhibin (INHBA) and glucocorticoid receptor (NR3C1) were more moderately, although significantly, affected by loss of associated DNA methylation. These data present a mixed effect of DNA methylation changes at selected loci supporting cautionary interpretation of DNA methylation results in the absence of functional data.

Stromal cells in tumor microenvironment and breast cancer

Cancer is a systemic disease encompassing multiple components of both tumor cells themselves and host stromal cells. It is now clear that stromal cells in the tumor microenvironment play an important role in cancer development. Molecular events through which reactive stromal cells affect cancer cells can be defined so that biomarkers and therapeutic targets can be identified. Cancer-associated fibroblasts (CAFs) make up the bulk of cancer stroma and affect the tumor microenvironment such that they promote cancer initiation, angiogenesis, invasion, and metastasis. In breast cancer, CAFs not only promote tumor progression but also induce therapeutic resistance. Accordingly, targeting CAFs provides a novel way to control tumors with therapeutic resistance. This review summarizes the current understandings of tumor stroma in breast cancer with a particular emphasis on the role of CAFs and the therapeutic implications of CAFs. In addition, the effects of other stromal components such as endothelial cells, macrophages, and adipocytes in breast cancer are also discussed. Finally, we describe the biologic markers to categorize patients into a specific and confirmed subtype for personalized treatment.

Intracrine oestrogen production and action in breast cancer: an epigenetic focus

Epigenome changes have been widely demonstrated to contribute to the initiation and progression of a vast array of cancers including breast cancer. The reversible process of many epigenetic modifications is thus an attractive feature for the development of novel therapeutic measures. In oestrogen receptor α (hereinafter referred to as ER) positive tumours, endocrine therapies have proven beneficial in patient care, particularly in postmenopausal women where two-thirds of tumours are oestrogen dependent. However, resistance to such therapies is a common feature amongst individuals. In the current review, we discuss the influence that epigenetics has on oestrogen dependent breast cancers, in particular (i) the production of intracrine oestrogen in postmenopausal women, (ii) the action of oestrogen on epigenetic processes, and (iii) the links between epigenetics and endocrine resistance and the current advancements in epigenetic therapy that target this process. This article is part of a Special Issue entitled 'CSR 2013'.

DNA methylation within the I.4 promoter region correlates with CYPl19A1 gene expression in human ex vivo mature omental and subcutaneous adipocytes

Background

DNA methylation at specific CpG sites within gene promoter regions is known to regulate transcriptional activity in vitro. In human adipose tissue, basal transcription of the aromatase (CYP19A1) gene is driven primarily by the I.4 promoter however the role of DNA methylation in regulating expression in ex vivo mature adipocytes is unknown. This observational study reports the correlation of DNA methylation within the I.4 promoter region of human mature subcutaneous and omental adipocytes with aromatase expression and body composition measures.

Methods

Omental and subcutaneous adipose tissue were collected from 25 obese subjects undergoing bariatric surgery and the mature adipocyte fraction purified. DNA methylation status of 5 CpG sites within a 550 base pair region encompassing the transcription start site (TSS) of promoter I.4 was determined using pyrosequencing. Relative aromatase and I.4 promoter specific mRNA expression was determined by qRT-PCR and whole body DXA performed in 25 participants.

Results

Site-specific DNA methylation varied from 21 ± 10% to 81 ± 11%. In omental adipocytes percentage methylation at the I.4.1 and I.4.2 CpG sites, but not other nearby sites, was negatively correlated with relative aromatase mRNA expression (R = - 0.52, P = 0.017 and R = - 0.52, P = 0.015). In contrast subcutaneous adipocytes percentage DNA methylation at the I.4.3 and I.4.5 sites were positively correlated with relative aromatase mRNA expression (R = 0.47, P = 0.022 and R = 0.55, P = 0.004). In a small subset of patients DNA methylation at the I.4.5 site was also positively correlated with whole body lean mass, bone mineral content and density.

Conclusions

In conclusion in mature adipocytes, the primary source of estradiol after menopause, increasing DNA methylation was correlated with aromatase mRNA expression and thus estradiol biosynthesis. These findings support a tissue-specific epigenetic regulation of the basal promoter activity in mature adipocytes; the mechanisms influencing this regulation and its physiological role remain to be elucidated.

Epigenetic modifications during sex change repress gonadotropin stimulation of cyp19a1a in a teleost ricefield eel (Monopterus albus)

In vertebrates, cytochrome P450 aromatase, encoded by cyp19a1, converts androgens to estrogens and plays important roles in gonadal differentiation and development. The present study examines whether epigenetic mechanisms are involved in cyp19a1a expression and subsequent gonadal development in the hermaphroditic ricefield eel. The expression of the ricefield eel cyp19a1a was stimulated by gonadotropin via the cAMP pathway in the ovary but not the ovotestis or testis. The CpG within the cAMP response element (CRE) of the cyp19a1a promoter was hypermethylated in the ovotestis and testis compared with the ovary. The methylation levels of CpG sites around CRE in the distal region (region II) and around steroidogenic factor 1/adrenal 4 binding protein sites and TATA box in the proximal region (region I) were inversely correlated with cyp19a1a expression during the natural sex change from female to male. In vitro DNA methylation decreased the basal and forskolin-induced activities of cyp19a1a promoter. Chromatin immunoprecipitation assays indicated that histone 3 (Lys9) in both regions I and II of the cyp19a1a promoter were deacetylated and trimethylated in the testis, and in contrast to the ovary, phosphorylated CRE-binding protein failed to bind to these regions. Lastly, the DNA methylation inhibitor 5-aza-2'-deoxycytidine reversed the natural sex change of ricefield eels. These results suggested that epigenetic mechanisms involving DNA methylation and histone deacetylation and methylation may abrogate the stimulation of cyp19a1a by gonadotropins in a male-specific fashion. This may be a mechanism widely used to drive natural sex change in teleosts as well as gonadal differentiation in other vertebrates.

Early onset pre-eclampsia is associated with altered DNA methylation of cortisol-signalling and steroidogenic genes in the placenta

Placental cortisol is inactivated in normotensive pregnancies, but is frequently present in pre-eclampsia associated placentae. Since glucocorticoids are strongly associated with the programming of long-term health, we assessed DNA methylation of genes involved in cortisol signalling and bioavailability, and hormonal signalling in the placenta of normotensive and hypertensive pregnancies. Candidate genes/CpG sites were selected through analysis of Illumina Infinium HumanMethylation450 BeadChip array data on control (n = 19) and early onset pre-eclampsia (EOPET; n = 19) placental samples. DNA methylation was further quantified by bisulfite pyrosequencing in a larger cohort of control (n = 111) cases, in addition to EOPET (n = 19), late onset pre-eclampsia (LOPET; n = 18) and normotensive intrauterine growth restriction (nIUGR; n = 13) cases. DNA methylation (percentage points) was increased at CpG sites within genes encoding the glucocorticoid receptor (NR3C1 exon 1D promoter; +8.46%; P<0.01) and corticotropin releasing hormone (CRH) binding protein (CRHBP intron 3; +9.14%; P<0.05), and decreased within CRH (5' UTR; -4.30%; P = 0.11) in EOPET-associated placentae, but not in LOPET nor nIUGR cases, compared to controls. Differential DNA methylation was not observed among groups at the 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2) gene promoter. Significant hypomethylation was observed in pre-eclampsia but not nIUGR placentae for steroidogenic genes, including CYP11A1 (exon1; EOPET; -9.66%; P<0.00001, and LOPET; -5.77%; P<0.001), 3β-hydroxy-delta-5-steroid dehydrogenase type 1 (HSD3B1 exon 2; EOPET; -12.49%; P<0.00001, and LOPET; -6.88%; P<0.001), TEA domain family member 3 (TEAD3 intron 1; EOPET; -12.56%; P<0.00001) and CYP19 (placental-specific exon 1.1 promoter; EOPET; -10.62%, P<0.0001). These data represent dysregulation of the placental epigenome in pre-eclampsia related to genes involved in maintaining the hormonal environment during pregnancy and highlights particular susceptibility in the early onset syndrome.

Origins and actions of tumor necrosis factor α in postmenopausal breast cancer

Tumor necrosis factor α (TNFα) has many roles in both physiological and pathological states. Initially thought to cause necrosis of tumors, research has shown that in many tumor types, including breast cancer, TNFα contributes to growth and proliferation. The presence of TNFα-derived from the tumor and infiltrating immune cells-within a breast tumor microenvironment has been correlated with a more aggressive phenotype, and the postmenopausal ER+ subtype of breast cancers appears to strongly respond to its many pro-growth signaling functions. We discuss how TNFα regulates estrogen biosynthesis within the breast, affecting the activity of the key estrogen-synthesizing enzymes aromatase, estrone sulfatase, and 17β-HSD type 1. Additionally, we describe the anti-adipogenic actions of TNFα that are critical in preventing adjacent estrogen-producing adipose fibroblasts from differentiating, ensuring that the tumor maintains a constant source of estrogen-producing cells. We examine how the increased risk of developing breast cancer in older and obese individuals may be linked to the levels of TNFα in the body. Finally, we evaluate the feasibility of targeting TNFα and its associated pathways as a novel approach to breast cancer therapeutics.

Epigenetic mechanisms regulate the prostaglandin E receptor 2 in breast cancer

The increase in local oestrogen production seen in oestrogen receptor positive (ER+) breast cancers is driven by increased activity of the aromatase enzyme. CYP19A1, the encoding gene for aromatase, is often overexpressed in the oestrogen-producing cells of the breast adipose fibroblasts (BAFs) surrounding an ER+ tumour, and the molecular processes underlying this upregulation is important in the development of breast-specific aromatase inhibitors for breast cancer therapy. Prostaglandin E2 (PGE2), a factor secreted by tumours, is known to stimulate CYP19A1 expression in human BAFs. The hormonal regulation of this process has been examined; however, what is less well understood is the emerging role of epigenetic mechanisms and how they modulate PGE2 signalling. This present study characterises the epigenetic processes underlying expression of the prostanoid receptor EP2 in the context of ER+ breast cancer. Sodium bisulphite sequencing of CpG methylation within the promoter region of EP2 revealed that an inverse correlation existed between methylation levels and relative EP2 expression in breast cancer cell lines MDA-MB-231, MCF7 and MCF10A but not in HS578t and T47D. Inhibition of DNA methylation with 5-aza-2'-deoxycytidine (5aza) and histone deacetylation with Trichostatin A (TSA) resulted in upregulation of EP2 mRNA in all cell lines with varying influences of each epigenetic process observed. Expression of EP2 was detected in human BAFs despite a natively methylated promoter, and this expression was further increased upon 5aza treatment. An examination of 3 triple negative, 3 ductal carcinoma in situ and 3 invasive ductal carcinoma samples revealed that there was no change in EP2 promoter methylation status between normal and cancer associated stroma, despite observed differences in relative mRNA levels. Although EP2 methylation status is inversely correlated to expression levels in established breast cancer cell lines, we could not identify that such a correlation existed in tumour-associated stroma cells.

Age dependency of estrogen responsiveness in the uterus and adipose tissue of aromatase-knockout (ArKO) mice

Aging is often associated with weight gain caused by metabolic changes including an increase of body fat. In this study we assessed the impact of age on estrogen responsiveness in the uterus and adipose tissue (AT) in aromatase-knockout (ArKO) mice. ArKO mice at the age of three or twelve months respectively were treated s.c. with vehicle, E(2) (10 μg/kg BW/d) or genistein (15 mg/kg BW/d) for three days. In the ArKO mouse model we were able to demonstrate that estrogen treatment resulted in an age specific response pattern both on a physiological and molecular level. Assessment of basal gene expression levels revealed significant age dependent differences only for elevated Esr1 levels in the uterus and leptin levels in infrarenal fat as well as lower levels of Pparg in the gonadal fat tissue. Investigating age dependency of estrogen responsiveness we were able to show that the E(2) and genistein resulted in age related pattern of regulation of expression of Esr1 and Lep in infrarenal and gonadal AT as well as the uterine expression of Pgr, Ltf and Pparg. In conclusion, evidence is provided that aging has an impact on the effectiveness of estrogen regulated processes in uterus and AT of ArKO mice. It remains to be elucidated whether or not this is associated with weight gain caused by an increase in body fat mass.

DNA methylation of the gonadal aromatase (cyp19a) promoter is involved in temperature-dependent sex ratio shifts in the European sea bass

Sex ratio shifts in response to temperature are common in fish and reptiles. However, the mechanism linking temperature during early development and sex ratios has remained elusive. We show in the European sea bass (sb), a fish in which temperature effects on sex ratios are maximal before the gonads form, that juvenile males have double the DNA methylation levels of females in the promoter of gonadal aromatase (cyp19a), the enzyme that converts androgens into estrogens. Exposure to high temperature increased the cyp19a promoter methylation levels of females, indicating that induced-masculinization involves DNA methylation-mediated control of aromatase gene expression, with an observed inverse relationship between methylation levels and expression. Although different CpGs within the sb cyp19a promoter exhibited different sensitivity to temperature, we show that the increased methylation of the sb cyp19a promoter, which occurs in the gonads but not in the brain, is not a generalized effect of temperature. Importantly, these effects were also observed in sexually undifferentiated fish and were not altered by estrogen treatment. Thus, methylation of the sb cyp19a promoter is the cause of the lower expression of cyp19a in temperature-masculinized fish. In vitro, induced methylation of the sb cyp19a promoter suppressed the ability of SF-1 and Foxl2 to stimulate transcription. Finally, a CpG differentially methylated by temperature and adjacent to a Sox transcription factor binding site is conserved across species. Thus, DNA methylation of the aromatase promoter may be an essential component of the long-sought-after mechanism connecting environmental temperature and sex ratios in vertebrate species with temperature-dependent sex determination.

Shu-Gan-Liang-Xue Decoction Simultaneously Down-regulates Expressions of Aromatase and Steroid Sulfatase in Estrogen Receptor Positive Breast Cancer Cells

OBJECTIVE

Estradiol (E2) plays an important role in the development of breast cancer. In postmenopausal women, the estrogen can be synthesized via aromatase (CYP19) pathway and steroid-sulfatase (STS) pathway in peripheral tissues, when the production in ovary has ceased. The objective of our study was to explore the effects of Shu-Gan-Liang-Xue Decoction (SGLXD) on the expressions of CYP19 and STS in estrogen receptor positive breast cancer MCF-7 and T47D cells.

METHODS

The effects of SGLXD on the cell viability of MCF-7 and T47D were analyzed by MTT assay. By quantitative real-time RT-PCR and Western blot, we evaluated the mRNA and protein expressions of CYP19 and STS in MCF-7 and T47D cells after SGLXD treatment.

RESULTS

By MTT assay, the cell viability rates of MCF-7 and T47D were significantly inhibited by SGLXD in a dose-dependent manner, the IC50 values were 40.07 mg/ml for MCF-7 cells and 25.62 mg/ml for T47D cells, respectively. As evidenced by real-time PCR and Western blot, the high concentrations of SGLXD significantly down-regulated the expressions of CYP19 and STS both in the transcript level and the protein level.

CONCLUSION

The results suggest that SGLXD is a potential dual aromatase-sulfatase inhibitor by simultaneously down-regulating the expressions of CYP19 and STS in MCF-7 and T47D cells.

Tissue-specific promoter methylation and histone modification regulate CYP19 gene expression during folliculogenesis and luteinization in buffalo ovary

Aromatase, the key enzyme of estrogen biosynthesis, is encoded by the CYP19 gene. The expression of CYP19 gene is regulated in species- and tissue-specific manner by alternate use of different promoters. We have previously, cloned and characterized the tissue-specific promoter and tissue-specific transcripts in preovulatory (granulosa cells) and postovulatory (corpus luteum) structure of buffalo ovary. The present study was aimed to understand if epigenetic gene regulation through DNA methylation and histone modifications is involved in tissue-specific CYP19 gene regulation during folliculogenesis and luteinization in buffalo ovary. Methylation analysis of five CpG dinucleotides of ovary specific proximal promoter II showed hypo-methylation in large follicle while hyper-methylation in corpus luteum. However, PI.1, the exclusive promoter responsible for residual CYP19 gene expression in corpus luteum, was found to be hypermethylated. Analysis of histone modifications using ChIP assay revealed that the distal promoter (PI.1) of CYP19 gene is ~40-fold more enriched with acetylated Histone H3 in corpus luteum than in the large follicle. This indicates that PI.1 chromatin was more accessible for transcription in corpus luteum as compared to large follicles. The chromatin accessibility for the proximal promoter (PII) in the preovulatory stage tends to be higher than the luteal tissue. However, the difference was not found to be significant. In vitro experiments showed the similar results. In conclusion, results of the present study suggests that tissue-specific methylation status of PII and chromatin remodeling through histone modifications of PI.1, coincides with the changes in expression of CYP19 gene and thus are the regulatory mechanism controlling its tissue-specific expression and promoter activity during folliculogenesis and luteinization.

Potential utility of natural products as regulators of breast cancer-associated aromatase promoters

Aromatase, the key enzyme in estrogen biosynthesis, converts androstenedione to estrone and testosterone to estradiol. The enzyme is expressed in various tissues such as ovary, placenta, bone, brain, skin, and adipose tissue. Aromatase enzyme is encoded by a single gene CYP 19A1 and its expression is controlled by tissue-specific promoters. Aromatase mRNA is primarily transcribed from promoter I.4 in normal breast tissue and physiological levels of aromatase are found in breast adipose stromal fibroblasts. Under the conditions of breast cancer, as a result of the activation of a distinct set of aromatase promoters (I.3, II, and I.7) aromatase expression is enhanced leading to local overproduction of estrogen that promotes breast cancer. Aromatase is considered as a potential target for endocrine treatment of breast cancer but due to nonspecific reduction of aromatase activity in other tissues, aromatase inhibitors (AIs) are associated with undesirable side effects such as bone loss, and abnormal lipid metabolism. Inhibition of aromatase expression by inactivating breast tumor-specific aromatase promoters can selectively block estrogen production at the tumor site. Although several synthetic chemical compounds and nuclear receptor ligands are known to inhibit the activity of the tumor-specific aromatase promoters, further development of more specific and efficacious drugs without adverse effects is still warranted. Plants are rich in chemopreventive agents that have a great potential to be used in chemotherapy for hormone dependent breast cancer which could serve as a source for natural AIs. In this brief review, we summarize the studies on phytochemicals such as biochanin A, genistein, quercetin, isoliquiritigenin, resveratrol, and grape seed extracts related to their effect on the activation of breast cancer-associated aromatase promoters and discuss their aromatase inhibitory potential to be used as safer chemotherapeutic agents for specific hormone-dependent breast cancer.

Epigenetics meets endocrinology

Although genetics determines endocrine phenotypes, it cannot fully explain the great variability and reversibility of the system in response to environmental changes. Evidence now suggests that epigenetics, i.e. heritable but reversible changes in gene function without changes in nucleotide sequence, links genetics and environment in shaping endocrine function. Epigenetic mechanisms, including DNA methylation, histone modification, and microRNA, partition the genome into active and inactive domains based on endogenous and exogenous environmental changes and developmental stages, creating phenotype plasticity that can explain interindividual and population endocrine variability. We will review the current understanding of epigenetics in endocrinology, specifically, the regulation by epigenetics of the three levels of hormone action (synthesis and release, circulating and target tissue levels, and target-organ responsiveness) and the epigenetic action of endocrine disruptors. We will also discuss the impacts of hormones on epigenetics. We propose a three-dimensional model (genetics, environment, and developmental stage) to explain the phenomena related to progressive changes in endocrine functions with age, the early origin of endocrine disorders, phenotype discordance between monozygotic twins, rapid shifts in disease patterns among populations experiencing major lifestyle changes such as immigration, and the many endocrine disruptions in contemporary life. We emphasize that the key for understanding epigenetics in endocrinology is the identification, through advanced high-throughput screening technologies, of plasticity genes or loci that respond directly to a specific environmental stimulus. Investigations to determine whether epigenetic changes induced by today's lifestyles or environmental 'exposures' can be inherited and are reversible should open doors for applying epigenetics to the prevention and treatment of endocrine disorders.

Tissue-specific promoter methylation coincides with Cyp19 gene expression in buffalo (Bubalus bubalis) placenta of different stages of gestation

Aromatase is the key enzyme for estrogen biosynthesis and is encoded by Cyp19 gene. Placental cotyledons are the main site of Cyp19 gene expression during pregnancy. The present study was aimed to investigate if DNA methylation and thus epigenetic mechanisms play a potential role in stage-specific regulation of Cyp19 expression in placental cotyledons of pregnant water buffaloes (Bubalus bubalis). Significantly higher expression of Cyp19 gene (p<0.05) in placental cotyledons of early gestation period and post parturition period was found in comparison to mid-gestation placenta. Tissue-specific promoter driven transcript analyses showed that the change in expression was mainly due to change in the relative abundance of transcripts from exon I.1 while the transcripts from exon II showed comparatively less variation. Methylation analysis of 5 CpG dinucleotides of placenta-specific promoter I.1 and proximal promoter, PII showed hypo-methylation of PI.1 in early and term placenta while hyper-methylation in mid-placenta. However, PII was found to be hypomethylated in all the three tissues. In conclusion, result of the present study demonstrated that stage-specific methylation status of PI.1, the major promoter responsible for aromatase expression in buffalo placental cotyledons, coincides with the change in expression of Cyp19 gene in different stages of pregnancy.