Phytoestrogens and breast cancer prevention: possible mechanisms of action

Quercetin Confers Tumoricidal Activity Through Multipathway Mechanisms in A N-Methylnitrosourea Rat Model of Colon Cancer

Objective: This research was conducted to explore mechanisms behind the potency of quercetin in inhibiting colon cancer induced in an experimental model. Materials and Methods: Forty adult male rats of Wistar strain were distributed into 4 groups; a negative control group, a colon cancer bearing group, a quercetin-treated group and a 5-fluorouracil (5-FU)-treated group. Serum TAG72 and GAL3 levels were quantified by ELISA. Colonic Wnt5a and Axin-1 gene expression was estimated by PCR. In addition, colonic tissues were subjected to immunohistochemical examination of Bax expression and histological investigation of histopathological alterations. Results: Quercetin elicited significant reduction in serum TAG72 and GAL3 levels, in addition to significant suppression of colonic Wnt5a gene expression and amplification of colonic Axin-1 gene expression. Also, it caused moderate positive reaction for Bax in mucosal epithelium. Conclusion: The present research provides experimental evidence about the activity of quercetin in the colon cancer of rats. Inhibitory effects on cancer development might be ascribable to regulatory action on Wnt signaling and induction of apoptosis.

Environmental and lifestyle risk factors of breast cancer in Malta-a retrospective case-control study

AIM AND BACKGROUND

Environmental exposures are known to play a role in the development of cancer, including breast cancer. There are known associations of breast cancer with environmental factors such as sunlight exposure, diet and exercise and alcohol consumption as well as physiological factors. This study examines the prevalence of risk factors for breast cancer related to dietary intake, environment and lifestyle in the female population of Malta. Malta has had little research in this area, and therefore an exploratory study was carried out.

METHODS

A retrospective case-control design was applied. Two hundred cases and 403 controls were included. Both cases and controls were subjects without a known family history for breast cancer. Controls were age-matched to cases in an age-decade category roughly at a 2:1 ratio. Interviews were carried out face-to-face using a questionnaire designed by Maltese and Sicilian researchers, encompassing various factors including diet, lifestyle, physiological factors and medical history. Breast cancer risk was then analysed using both univariate and multivariate analyses. For factors having a metric scale, the Mann-Whitney test was used to compare mean scores, while for categorical factors, the chi-square test was used to compare percentages between the case and control groups. Statistical modelling was carried out using binary logistic regression to relate the likelihood of breast cancer to over 50 risk/protective factors analysed collectively.

RESULTS

Univariate analysis showed around 20 parameters of interest, 14 of which were statistically significant at a 0.05 level of significance. Logistic regression analysis identified 11 predictors of interest that were statistically significant. Tomato, coffee and canned meat consumption were associated with lower likelihood of breast cancer (OR = 0.988, 0.901, 0.892, respectively), whereas beans and cabbage consumption and low sodium salt were positively associated with breast cancer (OR = 1.045, 1.834, 1.028, respectively). Premenopausal status was associated with a lower risk of breast cancer compared to postmenopausal status (OR = 0.067). Not having experienced myocardial infarction was associated with lower odds of breast cancer (OR = 0.331). Increased height was also found to have a strong association with risk of breast cancer, with the odds of having breast cancer increasing for every centimetre increase in height (OR = 1.048). In terms of quantity, odds of having breast cancer were lower in those exposed to sunlight (OR = 0.891). The odds of having breast cancer were also lower in those not using the oral contraceptive pill (OR = 0.454).

CONCLUSIONS

Various factors in this exploratory study were found to be associated with development of breast cancer. While causal conclusions cannot be made, tomato consumption is of particular interest, as these results corroborate findings found in other studies. A negative association of breast cancer with sunlight exposure and oral contraceptive pill use corroborates findings in other studies. Other associations with dietary intake can be explained by dietary changes. More robust studies in this area, including possible longitudinal studies, are warranted.

Celery root extract as an inducer of mania induction in a patient on venlafaxine and St John's Wort

Celery root belongs to a group of plants classified as the umbelliferous family, which contains phytoestrogens. Phytoestrogens are structurally similar to estrogen as they share a pair of hydroxyl groups and phenolic ring, which enables them to bind to estrogen receptors directly, making them a herbal remedy for low estrogen states such as menopause. We present a case of a female patient with depression who was stabilized on venlafaxine and St John's Wort, and who developed a manic episode due to elevated serum venlafaxine levels after she started taking celery extracts for menopausal related issues. We proffer a hypothesis for this unusual occurrence.

Isoflavones: Anti-Inflammatory Benefit and Possible Caveats

Inflammation, a biological response of body tissues to harmful stimuli, is also known to be involved in a host of diseases, such as obesity, atherosclerosis, rheumatoid arthritis, and even cancer. Isoflavones are a class of flavonoids that exhibit antioxidant, anticancer, antimicrobial, and anti-inflammatory properties. Increasing evidence has highlighted the potential for isoflavones to prevent the chronic diseases in which inflammation plays a key role, though the underlying mechanisms remain unclear. Recently, some studies have raised concerns about isoflavones induced negative effects like carcinogenesis, thymic involution, and immunosuppression. Therefore, this review aims to summarize the anti-inflammatory effects of isoflavones, unravel the underlying mechanisms, and present the potential health risks.

Polyphenols from Erythrina crista-galli: Structures, Molecular Docking and Phytoestrogenic Activity

OBJECTIVES

The current study aimed at exploring the secondary metabolites content of Erythrina crista-galli aqueous methanol extract and assessing its phytoestrogenic and cytoprotective activities.

METHODS

Isolation of the compounds was carried out using conventional chromatographic techniques. The structures of the isolated compounds were elucidated based on the UV, NMR spectral data along with their mass-spectrometric analyses. The phytoestrogenic activity was evaluated in-silico and in vitro using the Arabidopsis thaliana pER8: GUS reporter assay and the proliferation-enhancing activity of MCF-7 cells.

KEY FINDINGS

Phytochemical investigation of E. crista-galli aqueous methanol extract resulted in the isolation and identification of five flavonoids. The plant extract and its fractions showed significant estrogenic activities compared to controls.

CONCLUSION

Five flavonoids were identified from E. crista-galli aqueous methanol extract. To the best of our knowledge, among these flavonoids, apigenin-7-O-rhamnosyl-6-C-glucoside was isolated for the first time from nature. Moreover, luteolin-6-C-glucoside was isolated for the first time from this plant. The plant revealed promising phytoestrogenic activities. This gives rationale to some of its pharmacological properties and suggests additional phytoestrogenic effects, which have not been reported yet.

4-(E)-{(p-tolylimino)-methylbenzene-1,2-diol}, 1 a novel resveratrol analog, differentially regulates estrogen receptors α and β in breast cancer cells

Breast cancer is a public health concern worldwide. Prolonged exposure to estrogens has been implicated in the development of breast neoplasms. Epidemiologic and experimental evidence suggest a chemopreventive role of phytoestrogens in breast cancers. Resveratrol, a naturally occurring phytoestrogen, has been shown to have potent anti-cancer properties. However, poor efficacy and bioavailability have prevented the use of resveratrol in clinics. In order to address these problems, we have synthesized a combinatorial library of azaresveratrol analogs and tested them for their ability to inhibit the proliferation of breast cancer cells. We have recently shown that 4-(E)-{(p-tolylimino)-methylbenzene-1,2-diol} (TIMBD), has better anti-cancer properties than resveratrol and any other resveratrol analog we have synthesized so far. The objective of this study was to investigate the regulation of estrogen receptors (ERs) α and β by TIMBD in breast cancer cell lines. We demonstrate that TIMBD significantly induces the mRNA and protein expression levels of ERβ and inhibits that of ERα. TIMBD inhibits mRNA and protein expression levels of oncogene c-Myc, and cell cycle protein cyclin D1, which are important regulators of cellular proliferation. TIMBD significantly induces protein expression levels of tumor suppressor genes p53 and p21 in MCF-7 cells. TIMBD inhibits c-Myc in an ERβ-dependent fashion in MCF-10A and ERβ1-transfected MDA-MB-231 cells, suggesting regulation of ERs as an important upstream mechanism of this analog. ERβ plays a partial role in inhibition of proliferation by TIMBD while ERα overexpression does not significantly affect TIMBD's inhibition.

Chemoprevention of Breast Cancer by Dietary Polyphenols

The review will discuss in detail the effects of polyphenols on breast cancer, including both the advantages and disadvantages of the applications of these natural compounds. First, we focus on the characterization of the main classes of polyphenols and then on in vitro and in vivo experiments carried out in breast cancer models. Since the therapeutic effects of the administration of a single type of polyphenol might be limited because of the reduced bioavailability of these drugs, investigations on combination of several polyphenols or polyphenols with conventional therapy will also be discussed. In addition, we present recent data focusing on clinical trials with polyphenols and new approaches with nanoparticles in breast cancer. Besides the clinical and translational findings this review systematically summarizes our current knowledge about the molecular mechanisms of anti-cancer effects of polyphenols, which are related to apoptosis, cell cycle regulation, plasma membrane receptors, signaling pathways and epigenetic mechanisms. At the same time the effects of polyphenols on primary tumor, metastasis and angiogenesis in breast cancer are discussed. The increasing enthusiasm regarding the combination of polyphenols and conventional therapy in breast cancer might lead to additional efforts to motivate further research in this field.

Natural Products for Chemoprevention of Breast Cancer

Breast cancer is the primary cause of cancer death in women. Although current therapies have shown some promise against breast cancer, there is still no effective cure for the majority of patients in the advanced stages of breast cancer. Development of effective agents to slow, reduce, or reverse the incidence of breast cancer in high-risk women is necessary. Chemoprevention of breast cancer by natural products is advantageous, as these compounds have few side effects and low toxicity compared to synthetic compounds. In the present review, we summarize natural products which exert chemopreventive activities against breast cancer, such as curcumin, sauchinone, lycopene, denbinobin, genipin, capsaicin, and ursolic acid. This review examines the current knowledge about natural compounds and their mechanisms that underlie breast cancer chemopreventive activity both in vitro and in vivo. The present review may provide information on the use of these compounds for the prevention of breast cancer.

Urinary Phytoestrogens Are Associated with Subtle Indicators of Semen Quality among Male Partners of Couples Desiring Pregnancy

BACKGROUND

Phytoestrogens have been associated with subtle hormonal changes, although effects on male fecundity are largely unknown.

OBJECTIVE

We evaluated associations between male urinary phytoestrogen (isoflavone and lignan) concentrations and semen quality.

METHODS

This study was a prospective cohort study of 501 male partners of couples desiring pregnancy and discontinuing contraception. Each participant provided up to 2 semen samples that were analyzed for 35 semen quality endpoints the following day. Linear mixed-effects models were used to estimate associations between baseline urinary phytoestrogen concentrations and semen quality parameters, adjusted for age, body mass index (BMI), research site, and serum lipid and cotinine concentrations.

RESULTS

Most associations between urinary phytoestrogens and semen quality parameters were null. However, select individual phytoestrogens were associated with semen quality parameters, with associations dependent on the class of phytoestrogens and modified by BMI. Specifically, genistein and daidzein were associated with a lower percentage of normal sperm and increased abnormalities in semen morphology, with reduced associations observed as BMI increased (P < 0.05) [percentages (95% CIs) of normal morphology by WHO traditional criteria: genistein, main effect: -5.61% (-9.42%, -1.79%); interaction: 0.19% (0.06%, 0.31%) per log unit increase; daidzein, main effect: -5.35% (-9.36%, -1.34%); interaction: 0.18% (0.05%, 0.32%) per log unit increase]. Enterolactone was associated with fewer abnormalities in semen morphometry and morphology and decreased DNA fragmentation, with reduced associations observed as BMI increased (P < 0.05) [percentages (95% CIs) of abnormalities in the neck and midpiece: enterolactone, main effect: -3.35% (-6.51%, -0.19%); interaction: 0.11% (0.01%, 0.21%) per log unit increase].

CONCLUSIONS

These results suggest that male urinary phytoestrogen concentrations characteristic of the US population may be associated with subtle indicators of male fecundity and semen quality but were not associated with couple fecundity.

Caffeine, coffee, and tea intake and urinary estrogens and estrogen metabolites in premenopausal women

BACKGROUND

Prior studies have found weak inverse associations between breast cancer and caffeine and coffee intake, possibly mediated through their effects on sex hormones.

METHODS

High-performance liquid chromatography/tandem mass spectrometry was used to quantify levels of 15 individual estrogens and estrogen metabolites (EM) among 587 premenopausal women in the Nurses' Health Study II with mid-luteal phase urine samples and caffeine, coffee, and/or tea intakes from self-reported food frequency questionnaires. Multivariate linear mixed models were used to estimate geometric means of individual EM, pathways, and ratios by intake categories, and P values for tests of linear trend.

RESULTS

Compared with women in the lowest quartile of caffeine consumption, those in the top quartile had higher urinary concentrations of 16α-hydroxyestrone (28% difference; Ptrend = 0.01) and 16-epiestriol (13% difference; Ptrend = 0.04), and a decreased parent estrogens/2-, 4-, 16-pathway ratio (Ptrend = 0.03). Coffee intake was associated with higher 2-catechols, including 2-hydroxyestradiol (57% difference, ≥4 cups/day vs. ≤6 cups/week; Ptrend = 0.001) and 2-hydroxyestrone (52% difference; Ptrend = 0.001), and several ratio measures. Decaffeinated coffee was not associated with 2-pathway metabolism, but women in the highest (vs. lowest) category of intake (≥2 cups/day vs. ≤1-3 cups/month) had significantly lower levels of two 16-pathway metabolites, estriol (25% difference; Ptrend = 0.01) and 17-epiestriol (48% difference; Ptrend = 0.0004). Tea intake was positively associated with 17-epiestriol (52% difference; Ptrend = 0.01).

CONCLUSION

Caffeine and coffee intake were both associated with profiles of estrogen metabolism in premenopausal women.

IMPACT

Consumption of caffeine and coffee may alter patterns of premenopausal estrogen metabolism.

Global transcriptome analysis profiles metabolic pathways in traditional herb Astragalus membranaceus Bge. var. mongolicus (Bge.) Hsiao

BACKGROUND

Astragalus membranaceus Bge. var. mongolicus (Bge.) Hsiao (A. mongolicus, family Leguminosae) is one of the most important traditional Chinese herbs. Among many secondary metabolites it produces, the effective bioactive constituents include isoflavonoids and triterpene saponins. The genomic resources regarding the biosynthesis of these metabolites in A. mongolicus are limited. Although roots are the primary material harvested for medical use, the biosynthesis of the bioactive compounds and its regulation in A. mongolicus are not well understood. Therefore, a global transcriptome analysis on A. mongolicus tissues was performed to identify the genes essential for the metabolism and to profile their expression patterns in greater details.

RESULTS

RNA-sequencing was performed for three different A. mongolicus tissues: leaf, stem, and root, using the Illumina Hiseq2000 platform. A total of 159.5 million raw sequence reads were generated, and assembled into 186,324 unigenes with an N50 of 1,524bp. Among them, 129,966 unigenes (~69.7%) were annotated using four public databases (Swiss-Prot, TrEMBL, CDD, Pfam), and 90,202, 63,946, and 78,326 unigenes were found to express in leaves, roots, and stems, respectively. A total of 8,025 transcription factors (TFs) were identified, in which the four largest families, bHLH, MYB, C3H, and WRKY, were implicated in regulation of tissue development, metabolisms, stress response, etc. Unigenes associated with secondary metabolism, especially those with isolavonoids and triterpene saponins biosynthesis were characterized and profiled. Most genes involved in the isoflavonoids biosynthesis had the lowest expression in the leaves, and the highest in the stems. For triterpene saponin biosynthesis, we found the genes in MVA and non-MVA pathways were differentially expressed among three examined tissues, indicating the parallel but compartmentally separated biosynthesis pathways of IPP and DMAPP in A. mongolicus. The first committed enzyme in triterpene saponin biosynthesis from A. mongolicus, cycloartenol synthase (AmCAS), which belongs to the oxidosqualene cyclase family, was cloned by us to study the astragalosides biosynthesis. Further co-expression analysis indicated the candidate CYP450s and glycosyltransferases (GTs) in the cascade of triterpene saponins biosynthesis. The presence of the large CYP450 families in A. mongolicus was further compared with those from Medicago truncatula and Arabidopsis thaliana, and the diversity and phylegenetic relationships of the CYP450 families were established.

CONCLUSION

A transcriptome study was performed for A. mongolicus tissues to construct and profile their metabolic pathways, especially for the important bioactive molecules. The results revealed a comprehensive profile for metabolic activities among tissues, pointing to the equal importance of leaf, stem, and root in A. mongolicus for the production of bioactive compounds. This work provides valuable resources for bioengineering and in vitro synthesis of the natural compounds for medical research and for potential drug development.

Essences in metabolic engineering of lignan biosynthesis

Lignans are structurally and functionally diverse phytochemicals biosynthesized in diverse plant species and have received wide attentions as leading compounds of novel drugs for tumor treatment and healthy diets to reduce of the risks of lifestyle-related non-communicable diseases. However, the lineage-specific distribution and the low-amount of production in natural plants, some of which are endangered species, hinder the efficient and stable production of beneficial lignans. Accordingly, the development of new procedures for lignan production is of keen interest. Recent marked advances in the molecular and functional characterization of lignan biosynthetic enzymes and endogenous and exogenous factors for lignan biosynthesis have suggested new methods for the metabolic engineering of lignan biosynthesis cascades leading to the efficient, sustainable, and stable lignan production in plants, including plant cell/organ cultures. Optimization of light conditions, utilization of a wide range of elicitor treatments, and construction of transiently gene-transfected or transgenic lignan-biosynthesizing plants are mainly being attempted. This review will present the basic and latest knowledge regarding metabolic engineering of lignans based on their biosynthetic pathways and biological activities, and the perspectives in lignan production via metabolic engineering.

Phytonutrients as therapeutic agents

Nutrients present in various foods plays an important role in maintaining the normal functions of the human body. The major nutrients present in foods include carbohydrates, proteins, lipids, vitamins, and minerals. Besides these, there are some bioactive food components known as "phytonutrients" that play an important role in human health. They have tremendous impact on the health care system and may provide medical health benefits including the prevention and/or treatment of disease and various physiological disorders. Phytonutrients play a positive role by maintaining and modulating immune function to prevent specific diseases. Being natural products, they hold a great promise in clinical therapy as they possess no side effects that are usually associated with chemotherapy or radiotherapy. They are also comparatively cheap and thus significantly reduce health care cost. Phytonutrients are the plant nutrients with specific biological activities that support human health. Some of the important bioactive phytonutrients include polyphenols, terpenoids, resveratrol, flavonoids, isoflavonoids, carotenoids, limonoids, glucosinolates, phytoestrogens, phytosterols, anthocyanins, ω-3 fatty acids, and probiotics. They play specific pharmacological effects in human health such as anti-microbial, anti-oxidants, anti-inflammatory, antiallergic, anti-spasmodic, anti-cancer, anti-aging, hepatoprotective, hypolipidemic, neuroprotective, hypotensive, diabetes, osteoporosis, CNS stimulant, analgesic, protection from UVB-induced carcinogenesis, immuno-modulator, and carminative. This mini-review attempts to summarize the major important types of phytonutrients and their role in promoting human health and as therapeutic agents along with the current market trend and commercialization.

Urinary enterolactone is associated with obesity and metabolic alteration in men in the US National Health and Nutrition Examination Survey 2001-10

Phyto-oestrogens are a family of plant-derived xeno-oestrogens that have been shown to prevent cancer in some studies. Whether phyto-oestrogen intake affects obesity status in a population is still unclear. In the present cross-sectional study, we examined the association of urinary phyto-oestrogen metabolites with obesity and metabolic parameters in children and adults. Data from 1294 children (age 6-19 years) and from 3661 adults (age ≥ 20 years) who participated in the US National Health and Nutrition Examination Survey 2001-10 were analysed. Multivariate logistic regression was applied to investigate the associations of BMI, waist circumference, serum metabolites (total cholesterol, HDL-cholesterol, LDL-cholesterol, TAG, fasting glucose and fasting insulin) and the metabolic syndrome with urinary phyto-oestrogen levels. When stratified by age and sex, we found a stronger association (OR 0·30, 95 % CI 0·17, 0·54; P< 0·001) between urinary enterolactone levels and obesity in adult males (age 20-60 years) than in children (age 12-19 years) or the elderly (age >60 years) in the same survey. However, no associations with urinary daidzein, O-desmethylangolensin, equol, enterodiol or genistein were found in the overall population. We also found that the elevation of enterolactone levels was inversely associated with TAG levels, fasting glucose levels, fasting insulin levels and the metabolic syndrome in males aged 20-60 years, but positively associated with HDL-cholesterol levels. The present results provide epidemiological evidence that urinary enterolactone is inversely associated with obesity in adult males.

The molecular targets of resveratrol

Resveratrol has emerged in recent years as a compound conferring strong protection against metabolic, cardiovascular and other age-related complications, including neurodegeneration and cancer. This has generated the notion that resveratrol treatment acts as a calorie-restriction mimetic, based on the many overlapping health benefits observed upon both interventions in diverse organisms, including yeast, worms, flies and rodents. Though studied for over a decade, the molecular mechanisms governing the therapeutic properties of resveratrol still remain elusive. Elucidating how resveratrol exerts its effects would provide not only new insights in its fundamental biological actions but also new avenues for the design and development of more potent drugs to efficiently manage metabolic disorders. In this review we will cover the most recent advances in the field, with special focus on the metabolic actions of resveratrol and the potential role of SIRT1 and AMPK. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

Phytoestrogens and prevention of breast cancer: The contentious debate

Phytoestrogens have multiple actions within target cells, including the epigenome, which could be beneficial to the development and progression of breast cancer. In this brief review the action of phytoestrogens on oestrogen receptors, cell signalling pathways, regulation of the cell cycle, apoptosis, steroid synthesis and epigenetic events in relation to breast cancer are discussed. Phytoestrogens can bind weakly to oestrogen receptors (ERs) and some have a preferential affinity for ERβ which can inhibit the transcriptional growth-promoting activity of ERα. However only saturating doses of phytoestrogens, stimulating both ERα and β, exert growth inhibitory effects. Such effects on growth may be through phytoestrogens inhibiting cell signalling pathways. Phytoestrogens have also been shown to inhibit cyclin D1 expression but increase the expression of cyclin-dependent kinase inhibitors (p21 and p27) and the tumour suppressor gene p53. Again these effects are only observed at high (> 10) µmol/L doses of phytoestrogens. Finally the effects of phytoestrogens on breast cancer may be mediated by their ability to inhibit local oestrogen synthesis and induce epigenetic changes. There are, though, difficulties in reconciling epidemiological and experimental data due to the fact experimental doses, both in vivo and in vitro, far exceed the circulating concentrations of “free” unbound phytoestrogens measured in women on a high phytoestrogen diet or those taking phytoestrogen supplements.

Measuring the kinetics of the binding of xenoestrogens and estrogen receptor alpha by fluorescence polarization

The mechanism of endocrine disruption by environmental xenoestrogens is unclear. Bisphenol-A (BPA) is an example. Its concentration in human serum is low, and its binding with estrogen receptor (ER) is weak. Yet its effect on prostate and mammary gland development was observed. We investigated whether this effect could be explained in terms of binding kinetics. We used the method of fluorescence polarization anisotropy to measure the kinetic rate constants of the binding of ERα with 19 xenoestrogens. Relative binding affinities (RBA) were also deduced from the kinetics. We drew three observations. First, our RBAs were consistent with published values, thus establishing the validity of our results. Second, our method allowed the determination of low RBAs (∼ 10(-4)) of lipophilic ligands, such as dibutyl phthalate. They could not be measured by steady-state IC50 assays because of their low solubility. Third, we found that BPA had a surprisingly high kon > 10(4) M(-1) s(-1). While its RBA was 1500 times lower than that of 17β estradiol (E2), its kon was >1/90 that of E2. As a result, a 10 min surge of BPA from pM to nM could drive the fraction of BPA-activated ERα to a potent 0.1%. This might help to explain the observable estrogenic impacts of BPA.

Differential regulation of estrogen receptors α and β by 4-(E)-{(4-hydroxyphenylimino)-methylbenzene,1,2-diol}, a novel resveratrol analog

Breast cancer is the second leading cause of death among women in the United States. Estrogens have been implicated as major risk factors in the development of breast neoplasms. Recent epidemiologic studies have suggested a protective role of phytoestrogens in prevention of breast and other cancers. Resveratrol, a naturally occurring phytoestrogen found notably in red grapes, berries and peanuts, has been shown to possess potent anti-cancer properties. However, the poor efficacy of resveratrol has prevented its use in a clinical setting. In order to improve the efficacy of resveratrol, we have synthesized a small combinatorial library of azaresveratrol analogs and tested them for their ability to inhibit the growth of breast cancer cell lines. We have recently shown that one of the synthesized analogs, 4-(E)-{(4-hydroxyphenylimino)-methylbenzene,1,2-diol} (HPIMBD), has better anti-cancer properties than resveratrol. The objective of this study was to investigate the differential regulation of estrogen receptors (ERs) α and β as a potential mechanism of inhibition of breast cancer by HPIMBD. Estrogen receptors α and β have been shown to have opposing roles in cellular proliferation. Estrogen receptor α mediates the proliferative responses of estrogens while ERβ plays an anti-proliferative and pro-apoptotic role. We demonstrate that HPIMBD significantly induces the expression of ERβ and inhibits the expression of ERα. HPIMBD also inhibits the protein expression levels of oncogene c-Myc and cell cycle protein cyclin D1, genes downstream to ERα and important regulators of cell cycle, and cellular proliferation. HPIMBD significantly induces protein expression levels of tumor suppressors p53 and p21 in MCF-7 cells. Additionally, HPIMBD inhibits c-Myc in an ERβ-dependent fashion in MCF-10A and ERβ1-transfected MDA-MB-231 cells, suggesting regulation of ERs as an important upstream mechanism of this novel compound. Molecular docking studies confirm higher affinity for binding of HPIMBD in the ERβ cavity. Thus, HPIMBD, a novel azaresveratrol analog may inhibit the proliferation of breast cancer cells by differentially modulating the expressions of ERs α and β.

Resveratrol inhibits estrogen-induced breast carcinogenesis through induction of NRF2-mediated protective pathways

The importance of estrogens in the etiology of breast cancer is widely recognized. Estrogen-induced oxidative stress has been implicated in this carcinogenic process. Resveratrol (Res), a natural antioxidant phytoestrogen has chemopreventive effects against a variety of illnesses including cancer. The objective of the present study was to characterize the mechanism(s) of Res-mediated protection against estrogen-induced breast carcinogenesis. Female August Copenhagen Irish rats were treated with 17β-estradiol (E2), Res and Res + E2 for 8 months. Cotreatment of rats with Res and E2 inhibited E2-mediated proliferative changes in mammary tissues and significantly increased tumor latency and reduced E2-induced breast tumor development. Resveratrol treatment alone or in combination with E2 significantly upregulated expression of nuclear factor erythroid 2-related factor 2 (NRF2) in mammary tissues. Expression of NRF2-regulated antioxidant genes NQO1, SOD3 and OGG1 that are involved in protection against oxidative DNA damage was increased in Res- and Res + E2-treated mammary tissues. Resveratrol also prevented E2-mediated inhibition of detoxification genes AOX1 and FMO1. Inhibition of E2-mediated alterations in NRF2 promoter methylation and expression of NRF2 targeting miR-93 after Res treatment indicated Res-mediated epigenetic regulation of NRF2 during E2-induced breast carcinogenesis. Resveratrol treatment also induced apoptosis and inhibited E2-mediated increase in DNA damage in mammary tissues. Increased apoptosis and decreased DNA damage, cell migration, colony and mammosphere formation in Res- and Res + E2-treated MCF-10A cells suggested a protective role of Res against E2-induced mammary carcinogenesis. Small-interfering RNA-mediated silencing of NRF2 inhibited Res-mediated preventive effects on the colony and mammosphere formation. Taken together, these results suggest that Res inhibits E2-induced breast carcinogenesis via induction of NRF2-mediated protective pathways.

DNA microarray-based gene expression profiling of estrogenic chemicals

We summarize updated information about DNA microarray-based gene expression profiling by focusing on its application to estrogenic chemicals. First, estrogenic chemicals, including natural/industrial estrogens and phytoestrogens, and the methods for detection and evaluation of estrogenic chemicals were overviewed along with a comprehensive list of estrogenic chemicals of natural or industrial origin. Second, gene expression profiling of chemicals using a focused microarray containing estrogen-responsive genes is summarized. Third, silent estrogens, a new type of estrogenic chemicals characterized by their estrogenic gene expression profiles without growth stimulative or inhibitory effects, have been identified so far exclusively by DNA microarray assay. Lastly, the prospect of a microarray assay is discussed, including issues such as commercialization, future directions of applications and quality control methods.

Higher urinary lignan concentrations in women but not men are positively associated with shorter time to pregnancy

Phytoestrogens have been associated with subtle hormonal changes, although effects on fecundity are unknown. Our objective was to evaluate the association between male and female urinary phytoestrogen (isoflavone and lignan) concentrations and time to pregnancy (TTP) in a population-based cohort of 501 couples desiring pregnancy and discontinuing contraception. Couples were followed for 12 mo or until pregnancy. Fecundability ORs (FORs) and 95% CIs were estimated after adjusting for age, body mass index, race, site, creatinine, supplement use, and physical activity in relation to female, male, and joint couple concentrations. Models included the phytoestrogen of interest and the sum of the remaining individual phytoestrogens. FORs <1 denote a longer TTP and FORs >1 a shorter TTP. Urinary lignan concentrations were higher, on average, among female partners of couples who became pregnant during the study compared with women who did not become pregnant (median enterodiol: 118 vs. 80 nmol/L; P < 0.10; median enterolactone: 990 vs. 412 nmol/L; P < 0.05) and were associated with significantly shorter TTP in models based on both individual and couples' concentrations (couples' models: enterodiol FOR, 1.13; 95% CI: 1.02, 1.26; enterolactone FOR, 1.11; 95% CI: 1.01, 1.21). Male lignan concentrations were not associated with TTP, nor were isoflavone concentrations. Sensitivity analyses showed that associations observed are unlikely to be explained by potential unmeasured confounding by lifestyle or other nutrients. Our results suggest that female urinary lignan concentrations at levels characteristic of the U.S. population are associated with a shorter TTP among couples who are attempting to conceive, highlighting the importance of dietary influences on fecundity.

Enterolactone concentrations and prognosis after postmenopausal breast cancer: assessment of effect modification and meta-analysis

We previously reported that high concentrations of enterolactone, a lignan metabolite, are associated with lower mortality in 1,140 breast cancer patients from Germany. Using an extended set of 2,182 patients aged 50-74 years at diagnosis (2001-2005) and prospectively followed up until 2009, we investigated whether the association with mortality differs by lifestyle factors and tumor characteristics. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using multivariable Cox regression. Potential differential effects by tumor characteristics and lifestyle factors were assessed and a meta-analysis of five studies addressing lignan exposure and breast cancer prognosis was performed to summarize evidence. Median enterolactone concentrations were 17.4 (± 30.5 standard deviation) and 22.9 nmol L(-1) (± 44.8), respectively, for 269 deceased and 1,913 patients still alive. High enterolactone concentrations were significantly associated with lower all-cause mortality (per 10 nmol L(-1) : HR 0.94, 95% CI 0.90-0.98), breast cancer-specific mortality (HR 0.94, 0.89-0.99), and distant disease-free survival (HR 0.94, 0.90-0.98). Associations were found for stage 0-IIIA but not for stage IIIB-IV disease (p(het) = 0.01) and were stronger in patients with BMI <25 kg m(-2) than those with BMI ≥ 25 (p(het) = 0.04). In patients with healthy lifestyle (BMI <25, nonsmoker, physically active), the inverse association with all-cause mortality was still apparent (HR 0.92, 0.85-0.99). The meta-analysis yielded significant associations both for all-cause (HR 0.57, 0.42-0.78) and breast cancer-specific mortality (HR 0.54, 0.39-0.75). Our findings show that high lignan exposure is associated with reduced mortality in breast cancer patients. The inverse association observed in this study cannot be entirely explained by a healthy lifestyle.

Arctigenin, a dietary phytoestrogen, induces apoptosis of estrogen receptor-negative breast cancer cells through the ROS/p38 MAPK pathway and epigenetic regulation

This study investigates the anticancer effect of arctigenin (ATG), a natural lignan product of Arctium lappa L., in human breast cancer MDA-MB-231 cells. Results indicate that ATG inhibits MDA-MB-231 cell growth by inducing apoptosis in vitro and in vivo. ATG triggers the mitochondrial caspase-independent pathways, as indicated by changes in Bax/Bcl-2 ratio, resulting in AIF and EndoG nuclear translocation. ATG increased cellular reactive oxygen species (ROS) production by increasing p22(phox)/NADPH oxidase 1 interaction and decreasing glutathione level. ATG clearly increases the activation of p38 MAPK, but not JNK and ERK1/2. Antioxidant EUK-8, a synthetic catalytic superoxide and hydrogen peroxide scavenger, significantly decreases ATG-mediated p38 activation and apoptosis. Blocking p38 with a specific inhibitor suppresses ATG-mediated Bcl-2 downregulation and apoptosis. Moreover, ATG activates ATF-2, a transcription factor activated by p38, and then upregulates histone H3K9 trimethylation in the Bcl-2 gene promoter region, resulting in Bcl-2 downregulation. Taken together, the results demonstrate that ATG induces apoptosis of MDA-MB-231 cells via the ROS/p38 MAPK pathway and epigenetic regulation of Bcl-2 by upregulation of histone H3K9 trimethylation.

Related flavonoids cause cooperative inhibition of the sarcoplasmic reticulum Ca²⁺ ATPase by multimode mechanisms

Flavonoids are group of plant-derived hydroxylated polycyclic molecules found in fruit and vegetables. They are known to bio-accumulate within humans and are considered to have beneficial health effects, including cancer chemoprotection. One mechanism proposed to explain this is that they are able to induce apoptosis in cancer cells by inhibiting a variety of kinases and also the Ca²⁺ ATPase. An investigation was undertaken with respect to the mechanism of inhibition for three flavonoids: quercetin, galangin and 3,6 dihydroxyflavone (3,6-DHF). Each inhibited the Ca²⁺ ATPase with K(i) values of 8.7, 10.3 and 5.4 μM, respectively, showing cooperative inhibition with n ~ 2. Given their similar structures, the flavonoids showed several differences in their mechanisms of inhibition. All three flavonoids stabilized the ATPase in the E₁ conformation and reduced [³²P]-ATP binding. However, both galangin and 3,6-DHF increased the affinity of Ca²⁺ for the ATPase by decreasing the Ca²⁺-dissociation rate constant, whereas quercetin had little effect. Ca²⁺-induced changes in tryptophan fluorescence levels were reduced in the presence of 3,6-DHF and galangin (but not with quercetin), indicating that Ca²⁺-associated changes within the transmembrane helices are altered. Both galangin and quercetin reduced the rates of ATP-dependent phosphorylation and dephosphorylation, whereas 3,6-DHF did not. Modelling studies suggest that flavonoids could potentially bind to two sites: one directly where nucleotides bind within ATP binding site and the other at a site close by. We hypothesize that interactions of these two neighbouring sites may account for both the cooperative inhibition and the multimode mechanisms of action seen with related flavonoids.

Recent advances in the metabolic engineering of lignan biosynthesis pathways for the production of transgenic plant-based foods and supplements

Plant physiological, epidemiological, and food science studies have shed light on lignans as healthy diets for the reduction of the risk of lifestyle-related noncommunicable diseases and, thus, the demand for lignans has been rapidly increasing. However, the low efficiency and instability of lignan production via extraction from plant resources remain to be resolved, indicating the requirement for the development of new procedures for lignan production. The metabolic engineering of lignan-biosynthesizing plants is expected to be most promising for efficient, sustainable, and stable lignan production. This is supported by the recent verification of biosynthetic pathways of major dietary lignans and the exploration of lignan production via metabolic engineering using transiently gene-transfected or transgenic plants. The aim of this review is to present an overview of the biosynthetic pathways, biological activities, and metabolic engineering of lignans and also perspectives in metabolic engineering-based lignan production using transgenic plants for practical application.

Endocrine disruption: fact or urban legend?

Endocrine disruptors (EDs) are substances that cause adverse health effects via endocrine-mediated mechanisms in an intact organism or its progeny or (sub) populations. Purported EDCs in personal care products include 4-MBC (UV filter) or parabens that showed oestrogenic activity in screening tests, although regulatory toxicity studies showed no adverse effects on reproductive endpoints. Hormonal potency is the key issue of the safety of EDCs. Oestrogen-based drugs, e.g. the contraceptive pill or the synthetic oestrogen DES, possess potencies up to 7 orders of magnitude higher than those of PCP ingredients; yet, in utero exposure to these drugs did not adversely affect fertility or sexual organ development of offspring unless exposed to extreme doses. Additive effects of EDs are unlikely due to the multitude of mechanisms how substances may produce a hormone-like activity; even after uptake of different substances with a similar mode of action, the possibility of additive effects is reduced by different absorption, metabolism and kinetics. This is supported by a number of studies on mixtures of chemical EDCs. Overall, despite of 20 years of research a human health risk from exposure to low concentrations of exogenous chemical substances with weak hormone-like activities remains an unproven and unlikely hypothesis.

Anticancer effect of genistein on BG-1 ovarian cancer growth induced by 17 β-estradiol or bisphenol A via the suppression of the crosstalk between estrogen receptor α and insulin-like growth factor-1 receptor signaling pathways

The interaction between estrogen receptor (ER) and insulin-like growth factor-1 receptor (IGF-1R) signaling pathway plays an important role in proliferation of and resistance to endocrine therapy to estrogen dependent cancers. Estrogen (E2) upregulates the expression of components of IGF-1 system and induces the downstream of mitogenic signaling cascades via phosphorylation of insulin receptor substrate-1 (IRS-1). In the present study, we evaluated the xenoestrogenic effect of bisphenol A (BPA) and antiproliferative activity of genistein (GEN) in accordance with the influence on this crosstalk. BPA was determined to affect this crosstalk by upregulating mRNA expressions of ERα and IGF-1R and inducing phosphorylation of IRS-1 and Akt in protein level in BG-1 ovarian cancer cells as E2 did. In the mouse model xenografted with BG-1 cells, BPA significantly increased a tumor burden of mice and expressions of ERα, pIRS-1, and cyclin D1 in tumor mass compared to vehicle, indicating that BPA induces ovarian cancer growth by promoting the crosstalk between ER and IGF-1R signals. On the other hand, GEN effectively reversed estrogenicity of BPA by reversing mRNA and protein expressions of ERα, IGF-1R, pIRS-1, and pAkt induced by BPA in cellular model and also significantly decreased tumor growth and in vivo expressions of ERα, pIRS-1, and pAkt in xenografted mouse model. Also, GEN was confirmed to have an antiproliferative effect by inducing apoptotic signaling cascades. Taken together, these results suggest that GEN effectively reversed the increased proliferation of BG-1 ovarian cancer by suppressing the crosstalk between ERα and IGF-1R signaling pathways upregulated by BPA or E2.

Modulatory effect of Ganoderma lucidum on expression of xenobiotic enzymes, oxidant-antioxidant and hormonal status in 7,12-dimethylbenz(a)anthracene-induced mammary carcinoma in rats

BACKGROUND

Mushrooms are an important natural source represents a major and untapped potent pharmaceutical product. Ganoderma lucidum (G. lucidum) an important medicinal mushroom has been shown to contain high amount of antioxidant. However, in vivo studies on G. lucidum fruiting bodies are lacking.

OBJECTIVES

To determine the effects of G. lucidum fruiting bodies ethanolic extract (GLEet) on expression of xenobiotic enzymes, oxidant-antioxidant and hormonal status on 7,12-dimethyl benz[a]antheracene (DMBA) induced experimental breast cancer was investigated in female Sprague dawley rats.

MATERIALS AND METHODS

Cancer bearing female Sprague dawley rats was orally treated with GLEet (500mg/kg body weight) for 16 weeks. Incidence and tumor volume in each groups, and biochemical parameters were carried out in plasma, liver, and mammary tissues of animals. Histopathological and immunohistochemical analysis were also determined.

RESULT

Oral administration of GLEet on tumor bearing animals significantly diminished the levels of lipid peroxidation thereby enhancing the nonenzymatic antioxidants and also positively regulated the estrogen receptor hormones level to near normal when compared with DMBA treated rats. Moreover, it also positively modulates the xenobiotic metabolizing enzymes. Therefore, the dietary administration of G. lucidum may be efficiently used as a chemopreventive agent against mammary carcinogenesis.

CONCLUSION

We concluded that G. lucidum is a potent chemopreventive agent, thereby it offers maximum protection against DMBA-induced mammary carcinogenesis.

Daidzein affects steroidogenesis and oestrogen receptor expression in medium ovarian follicles of pigs

Daidzein, a phytoestrogen present in soybean products used in swine feed, has been demonstrated to affect both reproductive and endocrine functions. The aims of this study were to examine the in vitro effects of daidzein on (1) progesterone (P4) and oestradiol (E2) secretion by porcine luteinised granulosa cells harvested from medium follicles, and (2) the mRNA and protein expression of oestrogen receptors α and β (ERα and ERβ) in these cells. The influence of E2 on P4 secretion and ERα and ERβ expression in the granulosa cells of pigs was also investigated. It was found that daidzein inhibited progesterone secretion by luteinised granulosa cells isolated from medium follicles. In contrast, E2 did not affect progesterone production by these cells. Moreover, daidzein did not alter the granulosal secretion of E2. Both daidzein and E2 decreased mRNA expression of ERα in the cells examined. The expression of ERβ mRNA was not affected by daidzein but was inhibited by E2. ERα protein was not detected while ERβ protein was found in the nuclei of the cells. Daidzein and E2 upregulated the expression of ERβ protein in the cells. In summary, the phytoestrogen daidzein directly affected the porcine ovary by inhibiting progesterone production and increasing ERβ protein expression. Daidzein-induced changes in follicular steroidogenesis and granulosal sensitivity to oestrogens may disturb reproductive processes in pigs.

Genistein, a soy phytoestrogen, prevents the growth of BG-1 ovarian cancer cells induced by 17β-estradiol or bisphenol A via the inhibition of cell cycle progression

An endocrine disrupting chemical (EDC) is a global health concern. In this study, we examined the effects of genistein (GEN) on bisphenol A (BPA) or 17β-estradiol (E2)-induced cell growth and gene alterations of BG-1 ovarian cancer cells expressing estrogen receptors (ERs). In an in vitro cell viability assay, E2 or BPA significantly increased the growth of BG-1 cells. This increased proliferative activity was reversed by treatment with ICI 182,780, a well-known ER antagonist, while cell proliferation was further promoted in the presence of propyl pyrazole triol (PPT), an ERα agonist. These results imply that cell proliferation increased by E2 or BPA was mediated by ERs, particularly ERα. BPA clearly acted as a xenoestrogen in BG-1 ovarian cancer cells by mimicking E2 action. In contrast, GEN effectively suppressed BG-1 cell proliferation promoted by E2 or BPA by inhibiting cell cycle progression. E2 and BPA increased the expression of cyclin D1, a factor responsible for the G1/S cell cycle transition. They also decreased the expression of p21, a potent cyclin-dependent kinase (CDK) inhibitor that arrests the cell cycle in G1 phase, and promoted the proliferation of BG-1 cells. As shown by its repressive effect on cell growth, GEN decreased the expression of cyclin D1 augmented by E2 or BPA. On the other hand, GEN increased the p21 expression downregulated by E2 or BPA. Collectively, our findings suggest that GEN, a dietary phytoestrogen, has an inhibitory effect on the growth of estrogen-dependent cancers promoted by E2 or BPA.

Daidzein-estrogen interaction in the rat uterus and its effect on human breast cancer cell growth

Sex hormone replacement therapy provides several advantages in the quality of life for climacteric women. However, estrogen-induced cell proliferation in the uterus and mammary gland increases the risk of cancer development in these organs. The lower incidence of mammary cancer in Asian women as compared with Western women has been attributed to high intake of soy isoflavones, including genistein. We have previously shown that genistein induces an estradiol-like hypertrophy of uterine cells, but does not induce cell proliferation, uterine eosinophilia, or endometrial edema. It also inhibits estradiol-induced mitosis in uterine cells and hormone-induced uterine eosinophilia and endometrial edema. Nevertheless, genistein stimulates growth of human breast cancer cells in culture; therefore, it is not an ideal estrogen for use in hormone replacement therapy (HRD). The present study investigated the effect of another soy isoflavone, daidzein (subcutaneous, 0.066 mg/kg body weight), in the same animal model, and its effect on responses induced by subsequent treatment (1 h later) with estradiol-17β (E(2); subcutaneous, 0.33 mg/kg body weight). In addition, we investigated the effects of daidzein (1 μg/mL) or E(2) on the growth of human breast cancer cells in culture. Results indicate that daidzein stimulates growth of breast cancer cells and potentiates estrogen-induced cell proliferation in the uterus. We suggest caution for the use of daidzein or formulas containing this compound in HRD. Future research strategies should be addressed in the search for new phytoestrogens that selectively inhibit cell proliferation in the uterus and breast.

Interaction effects between genes involved in the AKT signaling pathway and phytoestrogens in gastric carcinogenesis: a nested case-control study from the Korean Multi-Center Cancer Cohort

SCOPE

To investigate whether genes involved in AKT/nuclear factor kappa B signaling and/or gene-environment interactions between the genes and phytoestrogens may be susceptible factors for gastric cancer.

METHODS AND RESULTS

The representative single nucleotide polymorphisms (SNPs) identified during the primary analysis (screening a total of 622 SNPs within ± 5 kbp of the 51 target gene locations) were further investigated in 317 matched case-control sets. The summary odds ratios (ORs) and 95% confidence intervals (CIs) for gastric cancer were calculated. Interaction effects between the SNPs and phytoestrogen biomarkers (genistein, daidzein, equol, and enterolactone) were computed. CDK1 rs4145643, FAS rs6586161, and FAS rs1468063 in the AKT signaling pathway presented significant genetic effects on gastric cancer (OR = 0.81 (95% CI: 0.66-0.99) for CDK1 rs4145643; OR = 1.27 (95% CI: 1.03-1.58) for FAS rs6586161; OR = 1.29 (95% CI: 1.03-1.56) for FAS rs1468063; Cochran Q statistics > 0.10). Risk alleles of FAS rs6586161, FAS rs1468063, MAP3K1 rs16886448, and MAP3K1 rs252902 showed significant interaction effects with enterolactone (p(interaction) < 0.05).

CONCLUSION

CDK1 and FAS genes involved in AKT signaling and influenced by anti-carcinogenic property of phytoestrogens can play a role as susceptible genetic factors in gastric carcinogenesis. FAS and MAP3K1 genes significantly interact with enterolactone, thereby modifying the individual's risk for gastric cancer.

Polyphenols sensitization potentiates susceptibility of MCF-7 and MDA MB-231 cells to Centchroman

Polyphenols as “sensitizers” together with cytotoxic drugs as “inducers” cooperate to trigger apoptosis in various cancer cells. Hence, their combination having similar mode of mechanism may be a novel approach to enhance the efficacy of inducers. Additionally, this will also enable to achieve the physiological concentrations facilitating significant increase in the activity at concentrations which the compound can individually provide. Here we propose that polyphenols (Resveratrol (RES) and Curcumin (CUR)) pre-treatment may sensitize MCF-7/MDA MB-231 (Human Breast Cancer Cells, HBCCs) to Centchroman (CC, antineoplastic agent). 6 h pre-treated cells with 10 µM RES/CUR and 100 µM RES/30 µM CUR doses, followed by 10 µM CC for 18 h were investigated for Ser-167 ER-phosphorylation, cell cycle arrest, redox homeostasis, stress activated protein kinase (SAPKs: JNK and p38 MAPK) pathways and downstream apoptosis effectors. Low dose RES/CUR enhances the CC action through ROS mediated JNK/p38 as well as mitochondrial pathway in MCF-7 cells. However, RES/CUR sensitization enhanced apoptosis in p53 mutant MDA MB-231 cells without/with involvement of ROS mediated JNK/p38 adjunct to Caspase-9. Contrarily, through high dose sensitization in CC treated cells, the parameters remained unaltered as in polyphenols alone. We conclude that differential sensitization of HBCCs with low dose polyphenol augments apoptotic efficacy of CC. This may offer a novel approach to achieve enhanced action of CC with concomitant reduction of side effects enabling improved management of hormone-dependent breast cancer.

Apigenin induces apoptosis via extrinsic pathway, inducing p53 and inhibiting STAT3 and NFκB signaling in HER2-overexpressing breast cancer cells

Phytoestrogens are known to prevent tumor induction. But their molecular mechanisms of action are still unknown. This study aimed to examine the effect of apigenin on proliferation and apoptosis in HER2-expressing breast cancer cells. In our experiments, apigenin inhibited the proliferation of MCF-7 vec and MCF-7 HER2 cells. This growth inhibition was accompanied with an increase of sub G(0)/G(1) apoptotic fractions. Overexpression of HER2 did not confer resistance to apigenin in MCF-7 cells. Apigenin-induced extrinsic apoptosis pathway up-regulating the levels of cleaved caspase-8, and inducing the cleavage of poly (ADP-ribose) polymerase, whereas apigenin did not induce apoptosis via intrinsic mitochondrial apoptosis pathway since this compound did not decrease mitochondrial membrane potential maintaining red fluorescence and did not affect the levels of B-cell lymphoma 2 (BCL2) and Bcl-2-associated X protein. Moreover, apigenin reduced the tyrosine phosphorylation of HER2 (phospho-HER2 level) in MCF-7 HER2 cells, and up-regulated the levels of p53, phospho-p53 and p21 in MCF-7 vec and MCF-7 HER2 cells. This suggests that apigenin induces apoptosis through p53-dependent pathway. Apigenin also reduced the expression of phospho-JAK1 and phospho-STAT3 and decreased STAT3-dependent luciferase reporter gene activity in MCF-7 vec and MCF-7 HER2 cells. Apigenin decreased the phosphorylation level of IκBα in the cytosol, and abrogated the nuclear translocation of p65 within the nucleus suggesting that it blocks the activation of NFκB signaling pathway in MCF-7 vec and MCF-7 HER2 cells. Our study indicates that apigenin could be a potential useful compound to prevent or treat HER2-overexpressing breast cancer.

The pro-apoptotic effect of quercetin in cancer cell lines requires ERβ-dependent signals

Quercetin has potentially beneficial effects on disease prevention, including cancer. An intriguing issue regarding the mechanisms of action of quercetin is the ability of this drug to modulate estrogen receptor (ER) activities. In a previous study, we demonstrated that quercetin elicited apoptosis through an ERα-dependent mechanism. However, the contribution of ERβ in quercetin-induced apoptosis remains elusive. Here, we report that quercetin, at nutritionally relevant concentrations, mimicked the 17β-estradiol (E2)-induced apoptotic effect in both ERβ1-transfected HeLa and in ERβ1-containing DLD-1 colon cancer cell lines by inducing the activation of p38. p38 activation is responsible for pro-apoptotic activation of caspase-3 and the cleavage of poly(ADP-ribose) polymerase. Notably, no inactivation or downregulation of the survival kinases (i.e., AKT and ERK1/2) or the antiapoptotic protein Bcl-2 was observed after quercetin stimulation. On the contrary, quercetin acted similarly to E2 by increasing the levels of the oncosuppressor protein PTEN and by impeding ERβ-dependent cyclin D1 promoter activity, which subsequently resulted in the transcription of the estrogen-responsive element remaining unchanged. As a whole, these data indicate that quercetin mimics the E2 effects in the presence of ERβ1, thus maintaining its anti-carcinogenic potential. In addition, the quercetin pro-apoptotic action in the presence of ERα may render it as a dual-sided protective agent against E2-related cancer in the reduction of tumour growth in organs that express ERα and/or ERβ.

In utero and postnatal exposure to isoflavones results in a reduced responsivity of the mammary gland towards estradiol

SCOPE

Exposure scenarios during different stages of development of an organism are discussed to trigger adverse and beneficial effects of isoflavones (ISO). The aim of this study was to investigate how in utero and postnatal ISO exposure modulates the estrogen sensitivity of the mammary gland and to identify the underlying molecular mechanisms.

METHODS AND RESULTS

Therefore, rats were exposed to either ISO-free (IDD), ISO-rich (IRD) or genistein-rich diet (GRD), up to young adulthood. Proliferative activity (PCNA expression) in the mammary gland at different ages and the estrogen sensitivity of the mammary gland to estradiol (E₂) or genistein (GEN) in adult ovariectomized animals was determined and compared with different treatments. Treatment with E₂ resulted in a significant lower proliferative and estrogenic response of the mammary gland in IRD and GRD compared with IDD. This correlates to a change in the gene expression pattern and a decrease in the ratio of estrogen receptor alpha (ERα) beta (ERβ

CONCLUSIONS

Our results provide evidence that in utero and postnatal exposure to a diet rich in ISO but also to GEN reduces the sensitivity of the mammary gland toward estrogens and support the hypothesis that in utero and postnatal ISO exposure reduces the risk to develop breast cancer.

Epigenetic events associated with breast cancer and their prevention by dietary components targeting the epigenome

Aberrant epigenetic alterations in the genome such as DNA methylation and chromatin remodeling play a significant role in breast cancer development. Since epigenetic alterations are considered to be more easily reversible compared to genetic changes, epigenetic therapy is potentially very useful in reversing some of these defects. Methylation of CpG islands is an important component of the epigenetic code, and a number of genes become abnormally methylated in breast cancer patients. Currently, several epigenetic-based synthetic drugs that can reduce DNA hypermethylation and histone deacetylation are undergoing preclinical and clinical trials. However, these chemicals are generally very toxic and do not have gene specificity. Epidemiological studies have shown that Asian women are less prone to breast cancer due to their high consumption of soy food than the Caucasian women of western countries. Moreover, complementary/and or alternative medicines are commonly used by Asian populations which are rich in bioactive ingredients known to be chemopreventive against tumorigenesis in general. Examples of such agents include dietary polyphenols, (-)-epigallocatechin-3-gallate (EGCG) from green tea, genistein from soybean, isothiocyanates from plant foods, curcumin from turmeric, resveratrol from grapes, and sulforaphane from cruciferous vegetables. These bioactive components are able to modulate epigenetic events, and their epigenetic targets are known to be associated with breast cancer prevention and therapy. This approach could facilitate the discovery and development of novel drugs for the treatment of breast cancer. In this brief review, we will summarize the epigenetic events associated with breast cancer and the potential of some of these bioactive dietary components to modulate these events and thus afford new therapeutic or preventive approaches.

Estimated enterolignans, lignan-rich foods, and fibre in relation to survival after postmenopausal breast cancer

Background:

Lignans – oestrogenic substances present in various foods – are associated with postmenopausal breast cancer risk, but not much is known regarding their effects on survival.

Methods:

In a follow-up study of 2653 postmenopausal breast cancer patients diagnosed between 2001 and 2005, vital status and causes of death were verified through end of 2009. Hazard ratios (HRs) and 95% confidence intervals (CIs) for estimated enterolignans, lignan-rich foods, and dietary fibre in relation to overall survival (OS) and breast cancer-specific survival (BCSS) were assessed using Cox proportional hazards models stratified by age at diagnosis and adjusted for prognostic/confounding factors.

Results:

Median follow-up time was 6.4 years, and 321 women died, 235 with breast cancer. High estimated enterolactone and enterodiol levels were associated with significantly lower overall mortality (highest quintile, HR=0.60, 95% CI=0.40–0.89, P_Trend=0.02 and HR=0.63, 95% CI=0.42–0.95, P_Trend=0.02, respectively). Fibre intake was also associated with a significantly lower overall mortality. Differentiated by median fibre intake, associations with estimated enterolignans were still evident at low but not high fibre intake. There was no effect modification by oestrogen receptor status and menopausal hormone therapy.

Conclusion:

Postmenopausal breast cancer patients with high estimated enterolignans may have a better survival.

Serum enterolactone and prognosis of postmenopausal breast cancer

PURPOSE

Lignans--plant-derived compounds with estrogen-dependent and -independent anticarcinogenic properties--have been associated with postmenopausal breast cancer risk, but data are limited regarding their effect on survival. Dietary lignans are metabolized to enterolignans, which are subsequently absorbed and become bioavailable.

PATIENTS AND METHODS

We assessed the prognosis of 1,140 postmenopausal patients with breast cancer age 50 to 74 years who were diagnosed between 2002 and 2005. Vital status through the end of 2009 was ascertained via local population registries, and deaths were verified by death certificates. Information on recurrences and secondary tumors was verified by clinical records and attending physicians. Associations of postdiagnostic serum enterolactone (a biomarker for dietary lignans) with overall survival and distant disease-free survival were assessed by using Cox proportional hazards models stratified by age at diagnosis and adjusted for prognostic factors.

RESULTS

Median enterolactone levels for deceased patients and those still alive were 17.0 and 21.4 nmol/L, respectively. During a median of 6.1 years of follow-up after diagnosis, 162 deaths were confirmed. Higher serum enterolactone levels were associated with significantly reduced hazard ratios (HRs) for death (HR per 10 nmol/L increment, 0.94; P = .04; HR for the highest quartile, 0.58; 95% CI, 0.34 to 0.99). For distant disease, HR was 0.94 per 10 nmol/L increment (P = .08) and 0.62 (95% CI, 0.35 to 1.09) for the highest quartile. The highest quartile of serum enterolactone was associated with a significantly reduced risk of death only for estrogen receptor-negative tumors (HR, 0.27; 95% CI, 0.08 to 0.87) but not for estrogen receptor-positive tumors (HR, 0.91; 95% CI, 0.45 to 1.84: P for heterogeneity = .09).

CONCLUSION

Postmenopausal patients with breast cancer who have high serum enterolactone levels may have better survival.

Induction of apoptotic cell death by phytoestrogens by up-regulating the levels of phospho-p53 and p21 in normal and malignant estrogen receptor α-negative breast cells

In this study, we investigated the underlying mechanism by which phytoestrogens suppress the growth of normal (MCF-10A) and malignant (MDA-MB-231) estrogen receptor α (ERα)-negative breast cells. We hypothesized that phytoestrogen inhibits the proliferation of ERα-negative breast cancer cells. We found that all tested phytoestrogens (genistein, apigenin, and quercetin) suppressed the growth of both MCF-10A and MDA-MB-231 cells, as revealed by proliferation assays. These results were accompanied by an increase in the sub-G0/G1 apoptotic fractions as well as an increase in the cell population in the G2/M phase in both cell types, as revealed by cell cycle analysis. When we assessed the effect of phytoestrogens on the level of intracellular signaling molecules by Western blot analysis, we found that phytoestrogens increased the level of active p53 (phospho-p53) without changing the p53 level in both MCF-10A and MDA-MB-231 cells. Phytoestrogens also induced an increase in p21, a p53 target gene, and a decrease in either Bcl-xL or cyclin B1 in both cell types. In contrast, the protein levels of phosphatase and tensin homolog, cyclin D1, cell division control protein 2 homolog, phospho-cell division control protein 2 homolog, and p27 were not changed after phytoestrogen treatment. Our data indicate that phytoestrogens induce apoptotic cell death of ERα-negative breast cancer cells via p53-dependent pathway and suggest that phytoestrogens may be promising agents in the treatment and prevention of ERα-negative breast cancer.

Multiple-targeting and conformational selection in the estrogen receptor: computation and experiment

Conformational selection is a primary mechanism in biomolecular recognition. The conformational ensemble may determine the ability of a drug to compete with a native ligand for a receptor target. Traditional docking procedures which use one or few protein structures are limited and may not be able to represent a complex competition among closely related protein receptors in agonist and antagonist ensembles. Here, we test a protocol aimed at selecting a drug candidate based on its ability to synergistically bind to distinct conformational states. We demonstrate, for the case of estrogen receptor α (ERα) and estrogen receptor β (ERβ), that the functional outcome of ligand binding can be inferred from its ability to simultaneously bind both ERα and ERβ in agonist and antagonist conformations as calculated docking scores. Combining a conformational selection method with an experimental reporter gene system in yeast, we propose that several phytoestrogens can be novel estrogen receptor β selective agonists. Our work proposes a computational protocol to select estrogen receptor subtype selective agonists. Compared with other models, present method gives the best prediction in ligands' function.

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.

Lactogens and estrogens in breast cancer chemoresistance

Tumor resistance to chemotherapy in advanced breast cancer is a major impediment to treatment success. Resistance can be induced by the drugs themselves or result from the action of internal factors. The role of hormones in chemoresistance has received little attention. This article focuses on two classes of hormones: lactogens and estrogens. Lactogens include prolactin, growth hormone and placental lactogen, all of which can activate the prolactin receptor. Estrogens include endogenous steroids and nonsteroidal compounds from the environment termed endocrine disruptors, all of which can activate 'classical' estrogen receptors (ERα and ERβ), as well as other types of receptors. Both lactogens and estrogens antagonize cytotoxicity of multiple chemotherapeutic agents through complementary mechanisms. The implications of chemoresistance by these hormones to patients with breast cancer, and the potential benefits of developing combinatorial anti-lactogen/anti-estrogen treatment regimens, are discussed.

Glycine soya diet synergistically enhances the suppressive effect of tamoxifen and inhibits tamoxifen-promoted hepatocarcinogenesis in 7,12-dimethylbenz[α]anthracene-induced rat mammary tumor model

There is increasing interest in phytoestrogens as potential alternatives to synthetic selective estrogen receptor modulators (SERMs) in the prevention and therapy of breast cancer. The present study is aimed at determining whether dietary glycine soya (Glycine max seeds; GS), which is rich in phytoestrogens, can enhance the anti breast cancer efficacy of the SERM tamoxifen (TAM) and the effect of TAM and GS, either alone or in combination, on DMBA-initiated hepatocarcinogenesis in rat. For determination of enhancing effect, rats bearing palpable 7, 12-dimethylbenz[α] anthracene (DMBA)-induced mammary tumors were treated with TAM (10 mg kg(-1)/day) while being fed AIN-93G diet with or without added GS (3×10(4) mg kg(-1)), and the tumor growth was monitored up to 5 weeks of treatment. For determining the effect on hepatocarcinogenesis, DMBA-initiated rats were exposed to TAM and dietary GS as above for 6 weeks during promotion stage in a medium-term bioassay, and the development of placental form of glutathione-S-transferase (GST-P)-expressing preneoplastic liver lesions was quantified. Exposure to both TAM and dietary GS enhanced the anti tumor efficacy of TAM via a combination of tumor cell apoptosis (determined by TUNEL) and inhibition of tumor cell proliferation (determined by PCNA immunostaining) and suppressed the growth of GST-P-positive liver lesions. The findings show that dietary GS enhances the therapeutic efficacy of TAM against mammary tumors and minimizes TAM's hepatocarcinogenesis promotion potential.