Transcription Of Estrogen-responsive Genes Research Articles

The Estrogenic Effect of Lysiphyllum strychnifolium (Craib) A. Schmitz Leaf Water Extract in MCF-7 Cells

Lysiphyllum strychnifolium (Craib) A. Schmitz (LS) has been widely used as traditional medicine in the northeast region of Thailand to stimulate the production of breast milk. There are no known studies on the estrogenic action of LS on the stimulation of breast milk production. Hence, the present study aimed to investigate the estrogenic effect of LS leaf water extract compared with quercetin, one of the compounds in LS, in human breast cancer cells (MCF-7). The effect of LS leaf water extract and quercetin on cell viability of MCF-7 cells was studied by MTT assay at a concentration range of 0 to 500 µg/mL. The expression of estrogen-dependent genes, the pS2, ERα, and ERβ was also examined by real-time RT-PCR, and the expression of ERα protein was detected by Western blotting. The quercetin content in the LS water extract was 285.67 ± 0.11 µg/g of dry extract. MCF-7 cells treated with LS leaf water extract (20 µg/mL) showed an upregulation of pS2 gene expression similar to that of the treatment with E2 (10−9 M) compared with that of the untreated control. The ERα gene expression was found to be upregulated by quercetin (0.16 µg/mL) and E2 (10−5 M) compared with the untreated control. In addition, quercetin (0.16 µg/mL) and LS extract (0.8, 4, and 20 µg/mL) decreased the phosphorylation of ERα at Ser167. LS extract (20 µg/mL) decreased ERα, but there was no significant effect on the ERα at Ser118 protein expression. This study provided scientific evidence for the potential estrogenic activities of LS leaf water extract. This indicates that ER-dependent pathways in MCF-7 cells served as mediators, facilitating the estrogenic properties of LS and its compounds to function effectively. Since LS induced pS2 gene transcription, it was confirmed that this could affect the transcription of estrogen-responsive genes, causing estrogenic effects. HIGHLIGHTSThis is the first study to demonstrate the estrogenic effect of Lysiphyllum strychnifolium leaf water extract. L. strychnifolium leaf water extract induced pS2 gene transcription, and it was confirmed that this could affect the transcription of estrogen-responsive genes which cause estrogenic effects. The results of this study support the mechanism and scientific evaluation on the use of L. strychnifolium for stimulation of breast milk in folk medicine. GRAPHICAL ABSTRACT

The SET oncoprotein promotes estrogen-induced transcription by facilitating establishment of active chromatin

SET is a multifunctional histone-binding oncoprotein that regulates transcription by an unclear mechanism. Here we show that SET enhances estrogen-dependent transcription. SET knockdown abrogates transcription of estrogen-responsive genes and their enhancer RNAs. In response to 17β-estradiol (E2), SET binds to the estrogen receptor α (ERα) and is recruited to ERα-bound enhancers and promoters at estrogen response elements (EREs). SET functions as a histone H2 chaperone that dynamically associates with H2A.Z via its acidic C-terminal domain and promotes H2A.Z incorporation, ERα, MLL1, and KDM3A loading and modulates histone methylation at EREs. SET depletion diminishes recruitment of condensin complexes to EREs and impairs E2-dependent enhancer-promoter looping. Thus, SET boosts E2-induced gene expression by establishing an active chromatin structure at ERα-bound enhancers and promoters, which is essential for transcriptional activation.

Hepatic estrogen-responsive genes relating to oogenesis in cutthroat trout (Oncorhynchus clarki): The transcriptional induction in primary cultured hepatocytes and the in vitro promoter transactivation in responses to estradiol-17β

Estradiol-17β (E2) regulates transcription of estrogen-responsive genes via estrogen receptors (Esr). In many teleost species, choriogenin (chg), vitellogenin (vtg) and esr genes are transactivated by E2 in the liver. This study aimed i) to compare expression properties of all subtypes of these genes (chg: chgHα, chgHβ, chgL; vtg: vtgAs, vtgC; esr: esr1a, esr1b, esr2a, esr2b) in response to estrogen stimulation, and ii) to confirm how each of four Esr subtypes is involved in the transcriptional regulation of these estrogen-responsive genes in cutthroat trout hepatocytes. In hepatocytes in primary culture, all chg and vtg subtype mRNA levels, and those of esr1a, were increased by E2 treatment (10−6 M) at 24 and 72 h post initiation (hpi), but esr1b, esr2a and esr2b mRNA levels were not. Treatment of hepatocytes with various concentrations of E2 (10−11–10−6 M) induced dose-dependent increases in the levels of all chg and vtg subtype mRNAs at 24 and 72 hpi. At both time points, the lowest dose that induced a significant increase in the expression levels of mRNAs (LOEC) for E2 differed among the genes; LOECs were estimated as 10−11 M for chgHα at 24 hpi, as 10−9 M for vtgC at 72 hpi, and as 10−10 M for other mRNAs at both 24 and 72 hpi. Meanwhile, the levels of esr1a mRNA exhibited a dose-dependent increase at 24 and 72 hpi, but the LOEC shifted from 10−9 M at 24 hpi to 10−7 M at 72 hpi because of a decrease in mRNA levels at treatment groups exposed to high concentrations of E2. All Esr subtypes transactivated chg, vtg and esr1a promoters in the presence of E2 in vitro. The activation levels indicated that promoter activity of chgHα ≥ vtgAs > chgHβ > chgL ≥ vtgC ≥ esr1a when mediated by Esr1a, chgHβ > chgHα > chgHL > vtgAs ≥ vtgC ≥ esr1a by Esr1b, chgHβ ≥ chgL > chgHα ≥ vtgAs > vtgC > esr1a by Esr2a, and chgHβ ≥ chgHα ≥ vtgAs > chgL ≥ vtgC > esr1a by Esr2b. Collectively, different Esr subtypes were distinctly different in their ability to transactivate estrogen-responsive target genes, resulting in differential expression of chg, vtg and esr1a genes in the estrogen-exposed hepatocytes.

Molecular mechanisms of estrogen receptor β-induced apoptosis and autophagy in tumors: implication for treating osteosarcoma.

The estrogen receptors α (ERα) and β (ERβ) are located in the nucleus and bind to estrogen to initiate transcription of estrogen-responsive genes. In a variety of tumor cells, ERβ has been shown to be a tumor suppressor. In particular, ERβ has anti-proliferative effects in osteosarcoma cells. Additionally, ERβ has been proven to regulate the apoptosis-related molecules IAP, BAX, caspase-3, and PARP, and to act on the NF-κB/BCL-2 pathway to induce apoptosis in tumors. Moreover, ERβ can regulate the expression of the autophagy associated markers LC3-I/LC-3II and p62 and induce autophagy in tumors by inhibiting the PI3K/AKT/mTOR pathway and activating the AMPK pathway. Here, we review the molecular mechanisms by which ERβ induces apoptosis and autophagy in a variety of tumors to further delineate more specific molecular mechanisms underlying osteosarcoma tumorigenesis and pathogenesis. Considering the broad involvement of ERβ in apoptosis, autophagy, and their interaction, it is plausible that the critical role of ERβ in inhibiting the proliferation and metastasis of osteosarcoma cells is closely related to its regulation of apoptosis and autophagy.

Abstract 5250: Notch signaling in ER+ breast cancer in response to endocrine therapy agents

Abstract Breast cancer is the most frequent cancer in women in the world, and more than 70% of breast cancer cases are estrogen receptor α positive (ER+). Standard treatment for ER+ breast cancers is endocrine therapy that consists of selective estrogen receptor modulators (SERMs) such as tamoxifen in pre-menopausal patients; aromatase inhibitors (AIs); or selective estrogen receptor down-regulators (SERDs); fulvestrant, and treatment is dependent on the menopausal state of the patient. Many luminal tumors acquire resistance to therapy and recur, leading to disease progression and mortality. Resistance may result from the activation of quiescent signaling pathways that drive cancer stem cell (CSC) activity, such as the Notch signaling pathway. Previous studies demonstrate that activation of Notch via the NOTCH1 receptor recruits ERα in the absence of estrogen to facilitate transcription of estrogen responsive genes. However, NOTCH4 is often upregulated in resistant ER+ breast cancers, driving endocrine therapy resistance via breast CSC activity. We hypothesize that NOTCH4 promotes the transcription of estrogen-responsive genes in the absence of estrogen in a selective manner that is unlike NOTCH1. Understanding how NOTCH4 regulates the transcription of estrogen responsive genes upon treatment with endocrine therapy may suggest the need for combination therapy for ER+ breast cancer that includes a Notch targeted therapy. We have measured mRNA expression of classic estrogen responsive genes in ER+ breast cancer cell lines that either overexpress NOTCH1 or NOTCH4. Our data demonstrate differential expression of estrogen-responsive genes between NOTCH1 and NOTCH4 in the presence of tamoxifen. We have also measured Notch contribution to breast cancer stem cell activity through mammosphere formation assays using ER+ breast cancer cell lines in the presence of fulvestrant and Notch signaling inhibitors. The expression of classical estrogen responsive genes from mammospheres was altered in the presence of fulvestrant, Notch signaling inhibitors, or combinations of the two treatments. Further, combination treatment led to the disruption of mammosphere formation suggesting that combination therapy in the clinic may be suitable for the prevention of endocrine resistance by inhibition of BCSC activity through NOTCH4. Citation Format: Ciera S. Singleton, Lucio Miele, Judy S. Crabtree. Notch signaling in ER+ breast cancer in response to endocrine therapy agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5250.

Abstract SY43-03: Long-range epigenetic control of estrogen-responsive transcription

Abstract SY43-03: Long-range epigenetic control of estrogen-responsive transcription

Intranuclear Mobility of Estrogen Receptor: Implication for Transcriptional Regulation.

The estrogen receptor (ER) is a ligand-dependent transcription factor that has two subtypes: ERα and ERβ. ERs regulate transcription of estrogen-responsive genes through interactions with multiple intranuclear components, such as cofactors and the nuclear matrix. Live cell imaging using fluorescent protein-labeled ERs has revealed that ligand-activated ERs are highly mobile in the nucleus, with transient association with the DNA and nuclear matrix. Scaffold attachment factor B (SAFB) 1 and its paralogue, SAFB2, are nuclear matrix-binding proteins that negatively modulate ERα-mediated transcription. Expression of SAFB1 and SAFB2 reduces the mobility of ERα in the presence of ligand. This regulatory machinery is emerging as an epigenetic-like mechanism that alters transcriptional activity through control of intranuclear molecular mobility.

Nucleosome dynamics: HMGB1 facilitates nucleosome restructuring and collaborates in estrogen-responsive gene expression

AbstractThe genome in the human cell is extraordinarily compacted in the nucleus. As a result, much of the DNA is inaccessible and functionally inert. Notwithstanding the highly efficient packaging, mechanisms have evolved to render DNA sites accessible that then enable a multitude of factors to carry out ongoing and vital functions. The compaction is derived from DNA complexation within nucleosomes, which can further consolidate into a higher-order chromatin structure. The nucleosome and nucleosomal DNA are not static in nature, but are dynamic, undergoing structural and functional changes as the cell responds to stresses and/or metabolic or environmental cues. We are only beginning to understand the forces and the complexes that engage the nucleosome to unearth the tightly bound and inaccessible DNA sequences and provide an opening to more accessible target sites. In many cases, current findings support a major role for the action of ATP-dependent chromatin remodeling complexes (CRCs) in providing an avenue to factor accessibility that leads to the activation of transcription. The estrogen receptor α (ERα) does not bind to the estrogen response element (ERE) in the canonical nucleosome. However, evidence will be presented that HMGB1 restructures the nucleosome in an ATP-independent manner and also facilitates access and strong binding of ERα to ERE. The features that appear important in the mechanism of action for HMGB1 will be highlighted, in addition to the characteristic features of the restructured nucleosome. These findings, together with previous evidence, suggest a collaborative role for HMGB1 in the step-wise transcription of estrogen-responsive genes. In addition, alternate mechanistic pathways will be discussed, with consideration that “HMGB1 restructuring” of the nucleosome may generally be viewed as a perturbation of the equilibrium of an ensemble of nearly isoenergetic nucleosome states in an energy landscape that is driven by conformational selection by HMGB1.

HDAC8 Inhibition Blocks SMC3 Deacetylation and Delays Cell Cycle Progression without Affecting Cohesin-dependent Transcription in MCF7 Cancer Cells

Cohesin, a multi-subunit protein complex involved in chromosome organization, is frequently mutated or aberrantly expressed in cancer. Multiple functions of cohesin, including cell division and gene expression, highlight its potential as a novel therapeutic target. The SMC3 subunit of cohesin is acetylated (ac) during S phase to establish cohesion between replicated chromosomes. Following anaphase, ac-SMC3 is deacetylated by HDAC8. Reversal of SMC3 acetylation is imperative for recycling cohesin so that it can be reloaded in interphase for both non-mitotic and mitotic functions. We blocked deacetylation of ac-SMC3 using an HDAC8-specific inhibitor PCI-34051 in MCF7 breast cancer cells, and examined the effects on transcription of cohesin-dependent genes that respond to estrogen. HDAC8 inhibition led to accumulation of ac-SMC3 as expected, but surprisingly, had no influence on the transcription of estrogen-responsive genes that are altered by siRNA targeting of RAD21 or SMC3. Knockdown of RAD21 altered estrogen receptor α (ER) recruitment at SOX4 and IL20, and affected transcription of these genes, while HDAC8 inhibition did not. Rather, inhibition of HDAC8 delayed cell cycle progression, suppressed proliferation and induced apoptosis in a concentration-dependent manner. We conclude that HDAC8 inhibition does not change the estrogen-specific transcriptional role of cohesin in MCF7 cells, but instead, compromises cell cycle progression and cell survival. Our results argue that candidate inhibitors of cohesin function may differ in their effects depending on the cellular genotype and should be thoroughly tested for predicted effects on cohesin's mechanistic roles.

Disruption of endocrine function in H295R cell in vitro and in zebrafish in vivo by naphthenic acids

Oil sands process-affected water (OSPW) have been reported to exhibit endocrine disrupting effects on aquatic organisms. Although the responsible compounds are unknown, naphthenic acids (NAs) have been considered to be implicated. The current study was designed to investigate the endocrine disruption of OSPW extracted NAs (OS-NAs) and commercial NAs (C-NAs) using a combination of in vitro and in vivo assays. The effects of OS-NAs and C-NAs on steroidogenesis were assessed both at hormone levels and expression levels of hormone-related genes in the H295R cells. The transcriptions of biomarker genes involved in endocrine systems in zebrafish larvae were investigated to detect the effects of OS-NAs and C-NAs on endocrine function in vivo. Exposure to OS-NAs and C-NAs significantly increased production of 17β-estradiol (E2) and progesterone (P4), and decreased production of testosterone (T). Both OS-NAs and C-NAs significantly induced the expression of several genes involved in steroidogenesis. The abundances of transcripts of biomarker gene CYP19b, ERα, and VTG were significantly up-regulated in zebrafish larvae exposed to OS-NAs and C-NAs, which indicated that NAs had negative effects on estrogen-responsive gene transcription in vivo. These results indicated that NAs should be partly responsible for the endocrine disrupting effects of OSPW.

Benzimidazoles diminish ERE transcriptional activity and cell growth in breast cancer cells

Estrogen receptors (ERα and ERβ) are members of the nuclear receptor superfamily. They regulate the transcription of estrogen-responsive genes and mediate numerous estrogen related diseases (i.e., fertility, osteoporosis, cancer, etc.). As such, ERs are potentially useful targets for developing therapies and diagnostic tools for hormonally responsive human breast cancers. In this work, two benzimidazole-based sulfonamides originally designed to reduce proliferation in prostate cancer, have been evaluated for their ability to modulate growth in estrogen dependent and independent cell lines (MCF-7 and MDA-MB 231) using cell viability assays. The molecules reduced growth in MCF-7 cells, but differed in their impact on the growth of MDA-MB 231 cells. Although both molecules reduced estrogen response element (ERE) transcriptional activity in a dose dependent manner, the contrasting activity in the MDA-MB-231 cells seems to suggest that the molecules may act through alternate ER-mediated pathways. Further, the methyl analog showed modest selectivity for the ERβ receptor in an ER gene expression array panel, while the naphthyl analog did not significantly alter gene expression. The molecules were docked in the ligand binding domains of the ERα-antagonist and ERβ-agonist crystal structures to evaluate the potential of the molecules to interact with the receptors. The computational analysis complimented the results obtained in the assay of transcriptional activity and gene expression suggesting that the molecules upregulate ERβ activity while down regulating that of ERα.

Bisphenol AF-induced endogenous transcription is mediated by ERα and ERK1/2 activation in human breast cancer cells.

Bisphenol AF (BPAF)-induced transcriptional activity has been evaluated by luciferase reporter assay. However, the molecular mechanism of BPAF-induced endogenous transcription in human breast cancer cells has not been fully elucidated. In the present study, we investigated the effect and mechanism of BPAF-induced endogenous transcription detected by real-time PCR in human breast cancer cells. We found that BPAF stimulated transcription of estrogen responsive genes, such as trefoil factor 1 (TFF1), growth regulation by estrogen in breast cancer 1 (GREB1) and cathepsin D (CTSD), through dose-dependent and time-dependent manners in T47D and MCF7 cells. Gene-silencing of ERα, ERβ and G protein-coupled estrogen receptor 1 (GPER) by small interfering RNA revealed that BPAF-induced endogenous transcription was dependent on ERα and GPER, implying both genomic and nongenomic pathways might be involved in the endogenous transcription induced by BPAF. ERα-mediated gene transcription was further confirmed by inhibition of ER activity using ICI 182780 in ERα-positive T47D and MCF7 cells as well as overexpression of ERα in ERα-negative MDA-MB-231 breast cancer cells. Moreover, we utilized Src tyrosine kinase inhibitor PP2 and two MEK inhibitors PD98059 and U0126 to elucidate the rapid nongenomic activation of Src/MEK/ERK1/2 cascade on endogenous transcription. Our data showed that BPAF-induced transcription could be significantly blocked by PP2, PD98059 and U0126, suggesting activation of ERK1/2 was also required to regulate endogenous transcription. Taken together, these results indicate that BPAF-induced endogenous transcription of estrogen responsive genes is mediated through both genomic and nongenomic pathways involving the ERα and ERK1/2 activation in human breast cancer cells.

Endocrine Disruptor Agent Nonyl Phenol Exerts An Estrogen-like Transcriptional Activity on Estrogen Receptor Positive Breast Cancer Cells

Several substances widely dispersed in the environment including hormones, industrial by-products and pollutants exert hormone like activity affecting steroid-responsive physiological systems. These compounds, named endocrine disruptors, are suspected to affect the mammalian reproductive system. However it is still unclear whether these substances are able to elicit estrogen like activity at the low concentrations encountered in the environment. Here we compare the effects of the endocrine disruptor nonylphenol with the effects elicited by 17-β-estradiol on gene transcription in the human breast cancer cell line MCF7. The correlation of the nonylphenol induced gene expression alterations with a reference profile of estradiol treated cells shows that nonylphenol at a concentration of 100 nM exerts a significant effect on estrogen responsive gene transcription in MCF7 cells. Most of the genes regulated by 17-β-estradiol respond to the nonylphenol in the same direction though to a much lesser extent. Molecular modeling of the potential interaction of nonylphenol with the estrogen receptor α shows that nonylphenol is likely to bind to the estrogen receptor α.

Analysis of histone posttranslational modifications in the control of chromatin plasticity observed at estrogen-responsive sites in human breast cancer cells.

It is well established that histone posttranslational modifications mediate the control of gene expression played by chromatin. Such modifications are commonly reversible and many alternatives are open to drive transcription of inducible genes. Estrogens govern growth and survival of hormone-sensitive cells by inducing expression of genes important for cell cycle progression and apoptosis. Transcription of estrogen-responsive genes is triggered by the lysine-specific demethylase 1 (LSD1)-dependent demethylation of dimethylated lysine 9 in histone H3 (H3K9me2) that accompanies to local generation of oxygen reactive species (ROS). Production of ROS modifies guanines in neighbor DNA with consequent recruitment of base-excision repair (BER) enzymes and formation of breaks that support creation of bridges between sites that, although distant on linear DNA, establish strategic contacts useful for productive transcription.

SIRT1 represses estrogen-signaling, ligand-independent ERα-mediated transcription, and cell proliferation in estrogen-responsive breast cells.

In prostate and breast cancer, the androgen receptor and estrogen receptor (ER) mediate induction of androgen- and estrogen-responsive genes respectively and stimulate cell proliferation in response to the binding of their cognate steroid hormones. Sirtuin 1 (SIRT1) is a NAD+-dependent class III histone deacetylase that has been linked to gene silencing, control of the cell cycle, apoptosis, and energy homeostasis. In prostate cancer, SIRT1 is required for androgen antagonist-mediated transcriptional repression and growth suppression of prostate cancer cells. Whether SIRT1 plays a similar role in the actions of estrogen or antagonists had not been determined. We report here that SIRT1 represses the transcriptional and proliferative response of breast cancer cells to estrogens, and this repression is ERα dependent. Inhibition of SIRT1 activity results in the phosphorylation of ERα in an AKT-dependent manner, and this activation requires phosphoinositide 3-kinase activity. Phosphorylated ERα subsequently accumulates in the nucleus, where ERα binds DNA ER-responsive elements and activates transcription of estrogen-responsive genes. This ER-dependent transcriptional activation augments estrogen-induced signaling, but also activates ER signaling in the absence of estrogen, thus defining a novel and unexpected mechanism of ligand-independent ERα-mediated activation and target gene transcription. Like ligand-dependent activation of ERα, SIRT1 inhibition-mediated ERα activation in the absence of estrogen also results in breast cancer cell proliferation. Together, these data demonstrate that SIRT1 regulates the most important cell signaling pathway for the growth of breast cancer cells, both in the presence and the absence of estrogen.

Transcriptional Responses of the Brain–Gonad–Liver Axis of Fathead Minnows Exposed to Untreated and Ozone-Treated Oil Sands Process-Affected Water

Oil sands process-affected water (OSPW) produced by the surface mining oil sands industry in Alberta, Canada, is toxic to aquatic organisms. Ozonation of OSPW attenuates this toxicity. Altered concentrations of sex steroid hormones, impaired reproductive performance, and less prominent secondary sexual characteristics have been reported for fish exposed to OSPW. However, the mechanism(s) by which these effects occur and whether ozonation can attenuate these effects in fish was unknown. The objective of this in vivo study was to investigate the endocrine-disrupting effects of OSPW and ozone-treated OSPW on the abundances of transcripts of genes in the brain-gonad-liver (BGL) axis in male and female fathead minnows (Pimephales promelas). Abundances of transcripts of genes important for synthesis of gonadotropins were greater in brains from both male and female fish exposed to untreated OSPW compared to that of control fish. In gonads from male fish exposed to untreated OSPW the abundances of transcripts of gonadotropin receptors and several enzymes of sex hormone steroidogenesis were greater than in control fish. The abundances of transcripts of estrogen-responsive genes were greater in livers from male fish exposed to untreated OSPW than in control fish. In female fish exposed to untreated OSPW there was less abundance of transcripts of gonadotropin receptors in gonads, as well as less abundance of transcripts of estrogen-responsive genes in livers. Many effects were either fully or partially attenuated in fish exposed to ozone-treated OSPW. The results indicate that (1) OSPW has endocrine-disrupting effects at all levels of BGL axis, (2) OSPW has different effects in male and female fish, (3) ozonation attenuates the effects of OSPW on abundances of transcripts of some genes, and the attenuation is more prominent in males than in females, but effects of ozonation on endocrine-disrupting effects of OSPW were less clear than in previous in vitro studies. The results provide a mechanistic basis for the endocrine-disrupting effects of OSPW from other studies.

Gene Regulation by Cohesin in Cancer: Is the Ring an Unexpected Party to Proliferation?

Cohesin is a multisubunit protein complex that plays an integral role in sister chromatid cohesion, DNA repair, and meiosis. Of significance, both over- and underexpression of cohesin are associated with cancer. It is generally believed that cohesin dysregulation contributes to cancer by leading to aneuploidy or chromosome instability. For cancers with loss of cohesin function, this idea seems plausible. However, overexpression of cohesin in cancer appears to be more significant for prognosis than its loss. Increased levels of cohesin subunits correlate with poor prognosis and resistance to drug, hormone, and radiation therapies. However, if there is sufficient cohesin for sister chromatid cohesion, overexpression of cohesin subunits should not obligatorily lead to aneuploidy. This raises the possibility that excess cohesin promotes cancer by alternative mechanisms. Over the last decade, it has emerged that cohesin regulates gene transcription. Recent studies have shown that gene regulation by cohesin contributes to stem cell pluripotency and cell differentiation. Of importance, cohesin positively regulates the transcription of genes known to be dysregulated in cancer, such as Runx1, Runx3, and Myc. Furthermore, cohesin binds with estrogen receptor α throughout the genome in breast cancer cells, suggesting that it may be involved in the transcription of estrogen-responsive genes. Here, we will review evidence supporting the idea that the gene regulation function of cohesin represents a previously unrecognized mechanism for the development of cancer.

Induction of estrogen-responsive gene transcription in the embryo, larval, juvenile and adult life stages of zebrafish as biomarkers of short-term exposure to endocrine disrupting chemicals

Real-time quantitative RT-PCR was adopted to investigate the transcription of the estrogen-responsive genes in different developmental stages of zebrafish exposed to endocrine disrupting chemicals (EDCs). The lowest observed effect concentrations (LOECs) of 17β-estradiol for inducing vtg1 transcription were 0.25, 0.5, 0.25 and ≤ 0.1 μg/L for embryo, larvae, juvenile and adult male zebrafish, respectively, while the LOECs of nonylphenol for induction of vtgs transcription were 50 μg/L in embryo and 100 μg/L in larvae and adult stages. The mRNA levels of the two vtgs were low in both the embryo and larvae stages, even at the highest 17β-estradiol or nonylphenol exposure concentrations, while the mRNA levels in liver of adult zebrafish of the two vtgs were 10 2 or even 10 4 times higher than those of the control groups at the corresponding nonylphenol or 17β-estradiol exposure concentrations. Similarity, the ERα and ERβ mRNA levels in juvenile and adult zebrafish livers were also higher. Results suggest that in the early developmental stages of zebrafish might be more sensitive (low LOECs) to the presence of EDCs such as nonylphenol, but juvenile and adult zebrafish have a more effective (high induction levels). The use of zebrafish juveniles, larvae and embryos offers an alternative stage to detect EDCs.

Photoperiod and temperature influence endocrine disruptive chemical-mediated effects in male adult zebrafish

Potential adverse effects of endocrine-disrupting chemicals (EDCs) in human and wildlife have become a major research topic. However, little is known about the effects of ambient conditions, including temperature and photoperiod, on endocrine disruption in zebrafish. We found that zebrafish hepatic estrogen-responsive gene transcription levels were greatly affected by temperature and photoperiod. Estrogen-responsive gene transcription levels at higher temperatures and with longer photoperiods were significantly higher than those at lower temperatures and with shorter photoperiods upon exposure to 17β-estradiol (E2) or nonylphenol (NP). Specifically, mRNA expression levels of vitellogenin 1 (vtg1) and vitellogenin 2 (vtg2) induced by both E2 and NP at high temperature (30 °C) were approximately 2–10 and 1.5–2.5 times higher than those exposed to low temperature (20 °C) under identical photoperiod conditions. mRNA expression levels of vtg1, vtg2 and estrogen receptor α (esrα) with a long photoperiod (16L) were also several folds higher than those with a short photoperiod (8L) upon exposure to E2 and NP at both high and low temperatures. Two-way analysis of variance revealed a significant interaction between temperature and photoperiod in hepatic vtg1 and esrα gene transcription in both high and low concentration treatment groups upon exposure to E2. However, no significant interactions were found for hepatic estrogen-responsive gene transcription at either NP concentrations. These results suggest that temperature and photoperiod could confound the risk assessment of estrogenic chemicals, and they also have potential implications for future environmental monitoring studies.

Induction of hepatic estrogen-responsive gene transcription by permethrin enantiomers in male adult zebrafish

Despite recent studies on enantioselectivity in acute aquatic toxicity and biodegradation of some pyrethroid pesticides, including permethrin (PM), enantiomer-specific estrogenic activity has been the subject of limited research. In this study, real-time quantitative RT-PCR was adopted to investigate induction of hepatic expression of mRNA of selected genes in male adult zebrafish after short-term exposure to PM enantiomers. The PM enantiomers were completely separated by a chiral HPLC column. The in vivo study found that a 2-day exposure to 100 ng/l PM racemate and its enantiomers was sufficient to stimulate transcription of two vitellogenin ( vtg) genes, while 250 ng/l exposure significantly induced gene transcription in a pattern and content similar to that of the control (50 ng/l 17β-estradiol (E2)). Significant differences were detected between the enantiomers in induction of hepatic gene transcription. At exposure level of 500 ng/l, the response to the (−)- trans enantiomer was 2.6 and 1.8 times greater than the (+)- trans enantiomer based on zebrafish vtg1 and vtg2 mRNA induction ( p < 0.05), respectively. Of the four enantiomers, the (−)- trans enantiomer showed the greatest estrogenic activity, with a relative activity 4-fold higher than the 50 ng/l E2 group. The results strongly suggested the occurrence of significant enantioselectivity in estrogenic activity of PM enantiomers. It would appear from our results and previous studies that using chiral pesticide as a single compound would increase the environmental risk of chronic toxicity, such as endocrine disruption, to humans and wildlife.