Dioxin and estrogen signaling in lung adenocarcinoma cells with different aryl hydrocarbon receptor/estrogen receptor α phenotypes

Using homing pigeons to monitor atmospheric organic pollutants in a city heavily involving in coal mining industry

Coal is the most extensively used fossil fuel in China. It is well documented that coal combustion detrimentally affected air quality, yet the contribution of coal mining activity to air pollution is still largely unknown. Homing pigeons have been applied to assess the occurrence of atmospheric pollutants within cities. Herein, we sampled homing pigeons from both urban and mining areas in a typical coal industry city (Datong, China) as biomonitors for assessing local air pollution. Target organic contaminants, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) were frequently detected in lung, liver, and fat tissues of the pigeons. The pollutants were predominately accumulated in lung, validating that respiration was the main accumulation route for these compounds in homing pigeons. In addition, pathological damage examination in lung and liver tissues revealed that the exposure to atmospheric pollutants impaired pigeon health. While the concentrations of PCBs and OCPs were similar in pigeons from urban and mining areas, the concentrations of PAHs were higher in pigeons from urban area. In contrast, more elevated levels of PBDEs (particularly BDE-209) were found in the mining area, which was consistent with the greater pathological damages and particulate matter levels. Unlike coal combustion, coal mining activities did not increase atmospheric PAH exposure to homing pigeons, but intensified PBDE contamination along with increasing emission of particulate matters. Overall, homing pigeons are promising biomonitors for assessing the respiratory exposure and risk of atmospheric pollutants within cities.

The association between circulating docosahexaenoic acid and lung cancer: A Mendelian randomization study

BACKGROUND

Lung cancer is a malignant tumor with a high incidence, it is vital to identify modifiable and avoidable risk factors for primary prevention, which can significantly lower the risk of cancer by preventing exposure to hazards and altering risky behavior. Some observational studies suggest that an increase in docosahexaenoic acid (DHA) consumption can reduce lung cancer risk. However, interpretation of these observational findings is difficult due to residual confounding or reverse causality. To evaluate the link between DHA and lung cancer, we have undertaken this analysis to examine the causal association between DHA and the risk of lung cancer using a two-sample Mendelian randomization (MR) framework.

METHODS

We performed a two-sample MR analysis to evaluate the causal effect of plasma DHA levels on lung cancer risk. For the exposure data, we extracted genetic variants as instrumental variables (IVs) that are strongly associated with DHA from a large-scale genome-wide association study (GWAS). We obtained the corresponding effect estimates for IVs on the risk of lung cancer with 11,348 cases and 15,861 controls. Finally, we applied Mendelian randomization analysis to obtain preliminary MR results and performed sensitivity analyses to verify the robustness of our results.

RESULTS

According to the primary MR estimates and further sensitivity analyses, a higher serum DHA level was associated with a higher risk of lung cancer [OR = 1.159, 95% CI (1.04-1.30), P = 0.01]. For lung adenocarcinoma, the results also showed a close correlation between the DHA level and lung adenocarcinoma [OR = 1.277, 95% CI (1.09-1.50), P = 0.003], but it was not statistically significant for squamous cell carcinoma [OR = 1.071, 95% CI (0.89-1.29), P = 0.467].

CONCLUSIONS

Our study revealed that plasma DHA is positively associated with the risk of lung cancer overall, especially for lung adenocarcinoma. This study provides new information to develop dietary guidelines for primary lung cancer prevention.

The smoking estrogens - a potential synergy between estradiol and benzo(a)pyrene

According to recent statistics, Lung Cancer (LC) is one of the most frequently diagnosed tumor types, representing nearly 12% of all global cancer cases. Moreover, in recent years, an increased mortality rate and incidence of this cancer were observed, especially among nonsmokers. Lung cancer patients are often characterized by poor prognosis and low survival rates, which encourages the scientific community to investigate the biochemical and molecular processes leading to the development of this malignancy. Furthermore, the mechanisms of LC formation and progression are not yet fully elucidated due to their high complexity, as well as a multitude of environmental, genetic, and molecular factors involved. Even though LC's association with exposure to cigarette smoke is indisputable, current research provides evidence that the development of this cancer can also be affected by the presence of estrogens and their interaction with several tobacco smoke components. Hence, the main goal of this brief review was to investigate reports of a possible synergy between 17β estradiol (E2), the most biologically active estrogen, and benzo(a)pyrene (BaP), a strongly carcinogenic compound produced as a result of incomplete tobacco combustion. The literature sources demonstrate a possible carcinogenic synergy between estrogens, especially E2, and BaP, a toxic tobacco smoke component. Therefeore, the combined effect of disturbed estrogen production in cancer cells, as well as the molecular influence exerted by BaP, could explain the increased aggressiveness and rate of LC development. Summarizing, the synergistic effect of these risk factors is an interesting area of further research.

ERα-dependent estrogen-TNFα signaling crosstalk increases cisplatin tolerance and migration of lung adenocarcinoma cells

Lung adenocarcinoma is the most common type of lung cancer in women. Our previous studies demonstrated that 17β-estradiol (E2) promoted lung adenocarcinoma cell proliferation and tumor growth through estrogen receptor ERα. Transcriptomic analysis suggested that E2 potentiated TNFα-NFκB signaling in ERα-expressing lung adenocarcinoma cells. This study further demonstrated that E2 increased TNFα receptor expression and TNFα-triggered NFκB activity in ERα-expressing cells. E2-activated ERα had no physical association with NFκB p65/p50 heterodimer but facilitated TNFα-initiated IκBα degradation, NFκB nuclear translocation, and S468/S536 phosphorylation of p65 essential for NFκB activity. While knockdown of ERα prevented E2 from boosting NFκB activity, antiestrogen ICI 182,780 stimulated NFκB activity like E2. Inhibition of GSK3β hampered E2:ERα-promoted NFκB activity and abolished S468 phosphorylation of p65, suggesting that GSK3β played a role in the E2-TNFα signaling crosstalk. In ERα-expressing cells, E2 and TNFα synergistically regulated many genes that were not typically responsive to either E2 or TNFα. Functional analysis of microarray data inferred that E2/TNFα-induced transcriptomic changes improved cell survival and movement. Viability and colony formation assays validated that E2 and TNFα together increased cisplatin tolerance of ERα-expressing cells. Wound healing assays also confirmed that E2/TNFα cotreatment increased cell migration in an ERα-dependent manner. E2/TNFα-induced dysregulation of genes such as cell survival and movement-associated genes, proto-oncogenes, metallothioneins and histone core genes was correlated with poor overall survival in patients. In summary, E2 and TNFα engaged in an ERα-dependent positive crosstalk in lung adenocarcinoma cells, consequently increasing NFκB activation, cisplatin tolerance and cell migration and worsening prognosis.

Environmental six-ring polycyclic aromatic hydrocarbons are potent inducers of the AhR-dependent signaling in human cells

The toxicities of many environmental polycyclic aromatic hydrocarbons (PAHs), in particular those of high-molecular-weight PAHs (with MW higher than 300), remain poorly characterized. The objective of this study was to evaluate the ability of selected environmentally relevant PAHs with MW 302 (MW302 PAHs) to activate the aryl hydrocarbon receptor (AhR), since this represents a major toxic mode of action of PAHs. A large number of the evaluated compounds exhibited strong AhR-mediated activities, in particular in human models. The studied MW302 PAHs also significantly contributed to the overall calculated AhR activities of complex environmental mixtures, including both defined standard reference materials and collected diesel exhaust particles. The high AhR-mediated activities of representative MW302 PAHs, e.g. naphtho[1,2-k]fluoranthene, corresponded with the modulation of expression of relevant AhR target genes in a human lung cell model, or with the AhR-dependent suppression of cell cycle progression/proliferation in estrogen-sensitive cells. This was in a marked contrast with the limited genotoxicity of the same compound(s). Given the substantial levels of the AhR-activating MW302 PAHs in combustion particles, it seems important to continue to investigate the toxic modes of action of this large group of PAHs associated with airborne particulate matter.

Xanthohumol Effect on 2,3,7,8-Tetrachlorodibenzo-p-dioxin-Treated Japanese Quails in Terms of Serum Lipids, Liver Enzymes, Estradiol, and Thyroid Hormones

Dioxins are compounds classified as persistent organic pollutants, from which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic to living organisms. TCDD is considered a carcinogen and has proinflammatory influence on animals and humans, promoting free radicals' formation, and binding with the aryl hydrocarbon receptor (AhR) leads to expression of cytochrome p-450 genes that in turn predisposes to mutations. Natural flavonoids, in this case xanthohumol (XN), have been reported to attenuate TCDD toxicity through inhibition of the transformation of the AhR. Moreover, XN shows antioxidant properties. The aim of the study was to compare the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and XN on lipid, liver enzyme, estradiol, and thyroid enzyme levels in the serum of Japanese quails. Adult, six-month-old, Japanese quails were divided into eight groups according to treatment procedures. Serum levels of total cholesterol (TCh), high-density lipoproteins (HDLs), triglycerides (TGs), estradiol, triiodothyronine, and thyroxine, and activities of alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase were measured. In comparison with the control group, 2,3,7,8-tetrachlorodibenzo-p-dioxin significantly decreased concentrations of serum HDLs and thyroid hormones and significantly increased the serum TCh level. Levels of serum TGs, liver enzymes, and estradiol were not changed after 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment. Based on our data, XN treatment may also increase the levels of thyroid hormones. Moreover, the tested dioxin disrupts the liver function, especially changing lipids' metabolism. Therefore, more studies are needed for better understanding the mechanism of toxic influence of 2,3,7,8-tetrachlorodibenzo-p-dioxin on key metabolic pathways and organs in living organisms.

Aryl Hydrocarbon Receptor-Dependent Metabolism Plays a Significant Role in Estrogen-Like Effects of Polycyclic Aromatic Hydrocarbons on Cell Proliferation

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants that interact in a complex manner with both the aryl hydrocarbon receptor (AhR) and estrogen receptors (ER). Their potential endocrine-disrupting activities may depend on both inhibitory AhR-ER cross-talk and on AhR-dependent metabolic production of estrogenic PAH metabolites. Here, we analyzed the impact of AhR on estrogen-like effects of PAHs, such as benzo[a]pyrene (BaP), in particular, on control of cell cycle progression/cell proliferation. Using AhR knockout variant of estrogen-sensitive human breast cancer MCF-7 cells (MCF-7 AhRKO cells), we observed that the AhR-dependent control of cytochrome P450 family 1 (CYP1) expression played a major role in formation of estrogenic BaP metabolites, most notably 3-OH-BaP, which contributed to the ER-dependent induction of cell cycle progression/cell proliferation. Both BaP metabolism and the BaP-induced S-phase transition/cell proliferation were inhibited in MCF-7 AhRKO cells, whereas these cells remained sensitive towards both endogenous estrogen 17β-estradiol or hydroxylated BaP metabolites. BaP was found to increase the activity of ER-dependent luciferase reporter gene in wild-type MCF-7 cells; however, unlike its hydroxylated metabolite, BaP failed to stimulate luciferase activity in MCF-7 AhRKO cells. Similarly, estrogen-like effects of other known estrogenic PAHs, such as benz[a]anthracene or 3-methylcholanthrene, were diminished in MCF-7 AhRKO cells. Ectopic expression of human CYP1A1 and CYP1B1 enzymes partly restored both BaP metabolism and its effects on cell proliferation. Taken together, our data suggest that the AhR-dependent metabolism of PAHs contributes significantly to the impact of PAHs on cell proliferation in estrogen-sensitive cells.

Multigenerational and Transgenerational Effects of Dioxins

Dioxins are ubiquitous and persistent environmental contaminants whose background levels are still reason for concern. There is mounting evidence from both epidemiological and experimental studies that paternal exposure to the most potent congener of dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), can lower the male/female ratio of offspring. Moreover, in laboratory rodents and zebrafish, TCDD exposure of parent animals has been reported to result in reduced reproductive performance along with other adverse effects in subsequent generations, foremost through the paternal but also via the maternal germline. These impacts have been accompanied by epigenetic alterations in placenta and/or sperm cells, including changes in methylation patterns of imprinted genes. Here, we review recent key studies in this field with an attempt to provide an up-to-date picture of the present state of knowledge to the reader. These studies provide biological plausibility for the potential of dioxin exposure at a critical time-window to induce epigenetic alterations across multiple generations and the significance of aryl hydrocarbon receptor (AHR) in mediating these effects. Currently available data do not allow to accurately estimate the human health implications of these findings, although epidemiological evidence on lowered male/female ratio suggests that this effect may take place at realistic human exposure levels.

Health risk of metal exposure via inhalation of cigarette sidestream smoke particulate matter

Cigarette sidestream smoke particulate matter (CSSP) is a major source of airborne metals in the indoor environment. However, the health impacts of inhalation of CSSP-bound metals are rarely studied. In this study, we quantify the amount of 37 metals discharged through CSSP from a leading Taiwan brand of cigarette, Long Life. We also estimate cancer and non-cancer risks due to inhalation of these metals and investigate possible modes of toxic action. Long Life CSSP exhibits a distinctive carcinogenic metal profile compared with Western brands. When released to a 60-m³ poorly ventilated room, Long Life CSSP metals increase the risk for cancer by a 9.26 or 20.90 in a million chance and the hazard quotient for non-cancer toxicity by 0.496 or 0.286 per cigarette depending on risk estimation system. Cd accounts for more than 90% and 80% of cancer and non-cancer risk, respectively. Long Life CSSP also contains considerable amounts of Al, Ba, and Fe. Metals are not responsible for CSSP-induced cytotoxicity, oxidative stress, and transactivation activity of AhR, Nrf2, and ERα. However, they diminish resveratrol-activated Nrf2 activity and downstream antioxidant gene expression in low-AhR-expressing lung cells. Our results suggest that chronic exposure to Long Life CSSP elevates Cd-associated cancer and non-cancer risks. Furthermore, exposure to Long Life CSSP metals may impair Nrf2-mediated antioxidant protection.

17α-Ethynylestradiol and 4-nonylphenol stimulate lung adenocarcinoma cell production in xenoestrogenic way

Lung cancer has been one of the major cancers leading to mortalities worldwide. In addition to smoking, estrogen is considered to play an important role in the lung cancer development because women have a higher proportion of adenocarcinoma than men. In the environment, there are many metabolites and waste products that mimic human estrogen structurally and functionally. 17α-Ethynylestradiol (EE2) which is used as an oral contraceptive is released into wastewater after being utilized. Moreover, 4-nonylphenol (NP) which is found in the petrochemical products and air pollutants reveals estrogenic activity. In the present study, 17β-estradiol (E2), EE2, and NP are administered to stimulate male lung adenocarcinoma cells (A549) and female lung adenocarcinoma cells (H1435). The results demonstrate that EE2 and NP stimulate A549 and H1435 cells proliferation in a dose- and time-dependent manner. Both estrogen receptors α and β are simultaneously activated. In response to estrogens, up-regulation of the epidermal growth factor receptor and extracellular signal-regulated kinase expression occurs. In conclusion, this is the first study to report that EE2 and NP exert a biotoxic effect to stimulate the proliferation of both male and female lung cancer cell in a dose- and time- dependent manner. The environmental hormones posing new challenges for lung cancer deserve further investigation.

Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.

The aryl hydrocarbon receptor is indispensable for dioxin-induced defects in sexually-dimorphic behaviors due to the reduction in fetal steroidogenesis of the pituitary-gonadal axis in rats

Many forms of the toxic effects produced by dioxins and related chemicals take place following activation of the aryl hydrocarbon receptor (AHR). Our previous studies have demonstrated that treating pregnant rats with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a highly toxic dioxin, attenuates the pituitary expression of gonadotropins to reduce testicular steroidogenesis during the fetal stage, resulting in the impairment of sexually-dimorphic behaviors after the offspring reach maturity. To investigate the contribution of AHR to these disorders, we examined the effects of TCDD on AHR-knockout (AHR-KO) Wistar rats. When pregnant AHR-heterozygous rats were given an oral dose of 1 µg/kg TCDD at gestational day (GD) 15, TCDD reduced the expression of pituitary gonadotropins and testicular steroidogenic proteins in male wild-type fetuses at GD20 without affecting body weight, sex ratio and litter size. However, the same defect did not occur in AHR-KO fetuses. Further, fetal exposure to TCDD impaired the activity of masculine sexual behavior after reaching adulthood only in the wild-type offspring. Also, in female offspring, not only the fetal gonadotropins production but also sexual dimorphism, such as saccharin preference, after growing up were suppressed by TCDD only in the wild-type. Interestingly, in the absence of TCDD, deleting AHR reduced masculine sexual behavior, as well as fetal steroidogenesis of the pituitary-gonadal axis. These results provide novel evidence that 1) AHR is required for TCDD-produced defects in sexually-dimorphic behaviors of the offspring, and 2) AHR signaling plays a role in gonadotropin synthesis during the developmental stage to acquire sexual dimorphism after reaching adulthood.

Decreased expression of cytochrome p450 1B1 in non-small cell lung cancer

Recent studies have associated oestrogen metabolism and cigarette smoking with their carcinogenic impact on the lungs. Compounds commonly found in tobacco smoke induce the activity of CYP1B1, the enzyme responsible for the synthesis of catecholic derivatives of oestrogens. During their redox transformations, these structures can release large amounts of reactive oxygen species or can form DNA adducts, which lead to the decomposition of genetic material. This process may illustrate the synergistic effect of oestrogenic activity and tobacco combustion on oestrogen-dependant lung cancer development. There is considerable evidence suggesting that the level of oestrogen in lung tumours is elevated. Therefore, by using reverse transcription, real-time PCR and Western Blot analysis, we evaluated the CYP1B1 status in tissues from 76 patients diagnosed with non-small cell lung cancer (NSCLC) to confirm whether potential overexpression of CYP1B1 may impact lung cancerogenesis induced by oestrogens. We found significantly lower levels of CYP1B1 transcripts (p=0.00001) and proteins (p=0.000085) in lung tumour material compared to corresponding, histopathologically unchanged tissues. We also analysed the association of CYP1B1 expression with gender, age and clinicopathological data of NSCLC patients. We observed lower amounts of CYP1B1 occurring in the middle stages of LC, regardless of gender, age or histological type of lung cancer.

Estrogen and cigarette sidestream smoke particulate matter exhibit ERα-dependent tumor-promoting effects in lung adenocarcinoma cells

Estrogen and secondhand smoke are key risk factors for nonsmoking female lung cancer patients who frequently have lung adenocarcinoma and show tumor estrogen receptor α (ERα) expression. We speculated that estrogen and secondhand smoke might cause harmful effects via ERα signaling. Our results showed that 17β-estradiol (E2), the primary form of endogenous estrogen, exacerbated proliferation, migration, and granzyme B resistance of lung adenocarcinoma cells in an ERα-dependent manner. Cigarette sidestream smoke particulate matter (CSSP), the major component of secondhand smoke, could activate ERα activity dose dependently in human lung adenocarcinoma cells. The estrogenic activity of CSSP was abolished by an ERα-selective antagonist. CSSP regulated the nuclear entry, phosphorylation, and turnover of ERα similarly to E2. Furthermore, CSSP enhanced E2-stimulated ERα activity and Ser118 phosphorylation even when ERα became saturated with E2. Activation of ERα by CSSP required GSK3β activity, but not involving polycyclic aromatic hydrocarbons, reactive oxygen species, calcium, epidermal growth factor receptor, and PI3K/Akt. Although CSSP possessed cytotoxicity, ERα-expressing cells grew and migrated faster than nonexpressing cells on recovery from CSSP exposure as observed in E2-pretreated cells. Knockdown of ERα by siRNA diminished E2- and CSSP-stimulated cell migration. Twenty-one genes, including SERPINB9, were identified to be upregulated by both E2 and CSSP via ERα. Increased SERPINB9 expression was accompanied with increased resistance to granzyme B-mediated apoptosis. This study demonstrates that estrogen has ERα-dependent tumor-promoting activity. CSSP acts like estrogen and shows a potential to enhance estrogen-induced ERα action.

In vitro analysis of factors influencing CYP1A2 expression as potential determinants of interindividual variation

Individual differences in drug metabolism contribute to interindividual variation that characterizes responses to drugs and risk in exposure to foreign chemicals. Large individual differences are found in expression levels of CYP1A2, a major drug-metabolizing enzyme. Underlying causes for this variation are not well understood. Several factors, including tobacco smoking, consumption of cruciferous vegetables, and sex, have been associated with modulating CYP1A2 expression. To understand factors regulating expression of CYP1A2 in establishing a causal relationship, this study examined effects of cigarette smoke condensate (CSC), indole-3-carbinol (I3C), and 17β-estradiol (estradiol) on CYP1A2 expression in in vitro systems using human liver and lung cells. Treatment with CSC (2-25 μg/mL) significantly increased levels of CYP1A2 in six cell lines examined, in a concentration- and time-dependent manner. Fold changes in expression levels relative to controls varied among cell lines. CYP1A2 enzymatic activity also increased with CSC exposure. Treatment of H1299 and HepB3 cells with dietary agent I3C (50 and 100 μmol/L) increased CYP1A2 expression. In human cell lines H1299 and H1395, treatment with estradiol (10 and 100 nmol/L) significantly reduced expression of CYP1A2. Using ChIP assays, effects of CSC on histone modifications were analyzed. Increases in H3K4me3 and H4K16ac were observed at several segments in the CYP1A2 gene, whereas H3K27me3 decreased, following CSC treatment. These results suggest that CYP1A2 expression is affected epigenetically by CSC. Additional studies will be needed to further establish regulatory mechanisms underlying effects of various environmental, dietary, and endogenous factors on CYP1A2 expression in better predicting individual variation.

Reduction in breast cancer susceptibility due to XbaI gene polymorphism of alpha estrogen receptor gene in Jordanians

Breast cancer is a global health concern among women worldwide. Estrogen receptor alpha (ERα) mediates diverse polymorphic effects in breast tissues that may relate to breast cancer susceptibility. The aim of this study was to evaluate the effect of -397 PvuII (T/C) and -351 XbaI (A/G) restriction fragment length polymorphism within intron 1 of ERα, and its effect on breast cancer susceptibility. A total of 156 women who were histopathologically diagnosed with breast cancer and 142 healthy Jordanian women were enrolled in this case-control study. Genomic DNA was extracted from whole peripheral blood, and the desired fragment was amplified using polymerase chain reaction followed by restriction digestion with PvuII and XbaI restriction enzymes. The results showed no significant association between PvuII polymorphism and breast cancer risk. However, a significant association was found between XbaI polymorphism and reduction in breast cancer risk within the "x" allele of heterozygotes (odds ratio [OR] 0.199, 95% confidence interval [CI] 0.09-0.044) and heterozygotes (OR 0.208, 95% CI 0.09-0.047). The combined analysis of PvuII and XbaI polymorphisms revealed a synergistic effect of Pp/Xx and pp/xx genotypes and a significant reduction in breast cancer risk with these genotypes. The results also showed no statistical differences among PvuII or XbaI polymorphisms based on stage, ER, progesterone receptor and expression of hormone receptor such as human epidermal growth factor receptor 2. This case-control study showed that XbaI polymorphism of alpha estrogen gene modified and reduced breast cancer susceptibility among Jordanians.

Estrogen regulation of gene expression in the teleost fish immune system

Elucidating the mechanisms of estrogens-induced immunomodulation in teleost fish is of great importance due to the observed worldwide continuing decrease in pristine environments. However, little is know about the immunotoxicological consequences of exposure to these chemicals in fish, or of the mechanisms through which these effects are mediated. In this review, we summarize the results showing estrogens (natural or synthetic) acting through estrogen receptors and regulating specific target genes, also through microRNAs (miRNAs), leading to modulation of the immune functioning. The identification and characterization of miRNAs will provide new opportunities for functional genome research on teleost immune system and can also be useful when screening for novel molecule biomarkers for environmental pollution.