Dietary lignan intakes and risk of breast cancer by tumor estrogen receptor status

Genistein and sex hormone treatment alleviated hepatic fat accumulation and inflammation in orchidectomized rats with nonalcoholic steatohepatitis

Testosterone deficiency has been reported to accelerate nonalcoholic fatty liver disease (NAFLD). However, there are minimal data on the risk of NAFLD in transgender women and the treatment of NAFLD in this population. This study aimed to investigate the treatment effects and the mechanisms of action of genistein and sex hormones in orchiectomized (ORX) rats with nonalcoholic steatohepatitis (NASH) induced by a high fat high fructose diet (HFHF). Seven-week old male Sprague-Dawley rats were randomly divided into 7 groups (n = 6 each group); 1) control group, 2) ORX + standard diet group, 3) HFHF group, 4) ORX + HFHF group, 5) ORX + HFHF diet + testosterone group (50 mg/kg body weight (BW) once weekly), 6) ORX + HFHF diet + estradiol group (1.6 mg/kg BW daily), and 7) ORX + HFHF diet + genistein group (16 mg/kg BW daily). The duration of treatment was 6 weeks. Liver tissue was used for histological examination by hematoxylin and eosin staining and hepatic fat measurement by Oil Red O staining. Protein expression levels of histone deacetylase3 (HDAC3) and peroxisome proliferator-activated receptor delta (PPARδ) were analyzed by immunoblotting. Hepatic nuclear factor (NF)-ĸB expression was evaluated by immunohistochemistry. Rats in the ORX + HFHF group had the highest degree of hepatic steatosis, lobular inflammation, hepatocyte ballooning and the highest percentage of positive Oil Red O staining area among all groups. The expression of HDAC3 and PPARδ was downregulated, while NF-ĸB expression was upregulated in the ORX + HFHF group when compared with control and ORX + standard diet groups. Testosterone, estradiol and genistein treatment improved histological features of NASH together with the reversal of HDAC3, PPARδ and NF-ĸB protein expression comparing with the ORX + HFHF group. In summary, genistein and sex hormone treatment could alleviate NASH through the up-regulation of HDAC3 and PPARδ, and the suppression of NF-ĸB expression.

Phytosterols activating nuclear receptors are involving in steroid hormone-dependent cancers: Myth or fact?

Nuclear receptors (NRs) represent intracellular proteins that function as a signaling network of transcriptional factors to control genes in response to a variety of environmental, dietary, and hormonal stimulations or serve as orphan receptors lacking a recognized ligand. They also play an essential role in normal development, metabolism, cell growth, cell division, physiology, reproduction, and homeostasis and function as biological markers for tumor subclassification and as targets for hormone therapy. NRs, including steroid hormone receptors (SHRs), have been studied as tools to examine the fundamentals of transcriptional regulation within the development of mammals and human physiology, in addition to their links to disturbances. In this regard, it is widely recognized that aberrant NR signaling is responsible for the pathological growth of hormone-dependent tumors in response to SHRs dysregulation and consequently represents a potential therapeutic candidate in a range of diseases, as in the case of prostate cancer and breast cancer. On the other hand, phytosterols are a group of plant-derived compounds that act directly as ligands for NRs and have proven their efficacy in the management of diabetes, heart diseases, and cancers. However, these plants are not suggested in cases of hormone-dependent cancer since a certain group of plants contains molecules with a chemical structure similar to that of estrogens, which are known as phytoestrogens or estrogen-like compounds, such as lignans, coumestans, and isoflavones. Therefore, it remains an open and controversial debate regarding whether consuming a phytosterol-rich diet and adopting a vegetarian lifestyle like the Mediterranean diet may increase the risk of developing steroid hormone-dependent cancers by constitutively activating SHRs and thereby leading to tumor transformation. Overall, the purpose of this review is to better understand the relevant mechanistic pathways and explore epidemiological investigations in order to establish that phytosterols may contribute to the activation of NRs as cancer drivers in hormone-dependent cancers.

Schisandrol A Exhibits Estrogenic Activity via Estrogen Receptor α-Dependent Signaling Pathway in Estrogen Receptor-Positive Breast Cancer Cells

The aim of this study was to examine the estrogen-like effects of gentiopicroside, macelignan, γ-mangostin, and three lignans (schisandrol A, schisandrol B, and schisandrin C), and their possible mechanism of action. Their effects on the proliferation of the estrogen receptor (ER)-positive breast cancer cell line (MCF-7) were evaluated using Ez-Cytox reagents. The expression of extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K), AKT, and estrogen receptor α (ERα) was measured by performing Western blot analysis. 17β-estradiol (E2), also known as estradiol, is an estrogen steroid and was used as a positive control. ICI 182,780 (ICI), an ER antagonist, was used to block the ER function. Our results showed that, except for gentiopicroside, all the compounds promoted proliferation of MCF-7 cells, with schisandrol A being the most effective; this effect was better than that of E2 and was mitigated by ICI. Consistently, the expression of ERK, PI3K, AKT, and ERα increased following treatment with schisandrol A; this effect was slightly better than that of E2 and was mitigated by ICI. Taken together, the ERα induction via the PI3K/AKT and ERK signaling pathways may be a potential mechanism underlying the estrogen-like effects of schisandrol A. This study provides an experimental basis for the application of schisandrol A as a phytoestrogen for the prevention of menopausal symptoms.

Genetic Variation in Steroid and Xenobiotic Metabolizing Pathways and Enterolactone Excretion Before and After Flaxseed Intervention in African American and European American Women

BACKGROUND

Metabolism and excretion of the phytoestrogen enterolactone (ENL), which has been associated with breast cancer risk, may be affected by variation in steroid hormone and xenobiotic-metabolizing genes.

METHODS

We conducted a randomized, crossover flaxseed intervention study in 252 healthy, postmenopausal women [137 European ancestry (EA) and 115 African ancestry (AA)] from western New York. Participants were randomly assigned to maintain usual diet or consume 10 g/day ground flaxseed for 6 weeks. After a 2-month washout period, participants crossed over to the other diet condition for an additional 6 weeks. Urinary ENL excretion was measured by gas chromatography-mass spectrometry and 70 polymorphisms in 29 genes related to steroid hormone and xenobiotic metabolism were genotyped. Mixed additive genetic models were constructed to examine association of genetic variation with urinary ENL excretion at baseline and after the flaxseed intervention.

RESULTS

SNPs in several genes were nominally (P < 0.05) associated with ENL excretion at baseline and/or after intervention: ESR1, CYP1B1, COMT, CYP3A5, ARPC1A, BCL2L11, SHBG, SLCO1B1, and ZKSCAN5. A greater number of SNPs were associated among AA women than among EA women, and no SNPs were associated in both races. No SNP-ENL associations were statistically significant after correction for multiple comparisons.

CONCLUSIONS

Variation in several genes related to steroid hormone metabolism was associated with lignan excretion at baseline and/or after flaxseed intervention among postmenopausal women.

IMPACT

These findings may contribute to our understanding of the differences observed in urinary ENL excretion among AA and EA women and thus hormone-related breast cancer risk.

Dietary Patterns for Women With Triple-negative Breast Cancer and Dense Breasts

Triple-negative breast cancer (TNBC) is a common subtype of breast cancer among women with dense breasts and is associated with a poor prognosis. Diet is a modifiable risk factor for breast cancer, but the association between the risk of TNBC and diet has not been studied. The present study investigated the hypothesis that a healthy dietary pattern was negatively associated with risk of TNBC in women with dense breasts (density types 3 and 4). After total mastectomy or breast conserving surgery, patients with TNBC (n = 38) and non-TNBC (n = 178) were recruited. The risk of TNBC was negatively associated with a healthy dietary pattern involving consumption of seafood and vegetables, and positively associated with a dietary pattern of consuming grains, meats, and eggs. Additionally, intake of animal fat, eggs, and meat was positively associated with the risk of TNBC, but intake of vegetable fats, nuts, and vegetables showed a negative association. Patients with TNBC had higher proportion of obesity or abdominal obesity than those with non-TNBC. The present study is the first to show a negative association between risk of TNBC and a healthy dietary pattern in women with dense breasts and suggests the importance of diet in the prevention of TNBC.

Pharmacokinetics and bioavailability of plant lignan 7-hydroxymatairesinol and effects on serum enterolactone and clinical symptoms in postmenopausal women: a single-blinded, parallel, dose-comparison study

Objective

7-Hydroxymaitairesinol (7-HMR) is a naturally occurring plant lignan found in whole grains and the Norway spruce (Piciea abies). The purpose of this study was to evaluate the bioavailability of a proprietary 7-HMR product (HMRlignan, Linnea SA, Locarno, Switzerland) through measurement of lignan metabolites and metabolic precursors.

Methods

A single-blind, parallel, pharmacokinetic and dose-comparison study was conducted on 22 post-menopausal females not receiving hormone replacement therapy. Subjects were enrolled in either a 36 mg/d (low-dose) or 72 mg/d dose (high-dose) regimen for 8 weeks. Primary measured outcomes included plasma levels of 7-HMR and enterolactone (ENL), and single-dose pharmacokinetic analysis was performed on a subset of subjects in the low-dose group. Safety data and adverse event reports were collected as well as data on hot flash frequency and severity.

Results

Pharmacokinetic studies demonstrated 7-HMR C_max = 757.08 ng/ml at 1 hour and ENL C_max = 4.8 ng/ml at 24 hours. From baseline to week 8, plasma 7-HMR levels increased by 191% in the low-dose group (p < 0.01) and by 1238% in the high-dose group (p < 0.05). Plasma ENL levels consistently increased as much as 157% from baseline in the low-dose group and 137% in the high-dose group. Additionally, the mean number of weekly hot flashes decreased by 50%, from 28.0/week to 14.3/week (p < 0.05) in the high-dose group. No significant safety issues were identified in this study.

Conclusion

The results demonstrate that HMRlignan is quickly absorbed into the plasma and is metabolized to ENL in healthy postmenopausal women. Clinically, the data demonstrate a statistically significant improvement in hot flash frequency. Doses up to 72 mg/d HMRlignan for 8 weeks were safe and well tolerated in this population.

Vitexin 6, a novel lignan, induces autophagy and apoptosis by activating the Jun N-terminal kinase pathway

Previous studies have reported that vitexins induce cytotoxic effects. In the present study, we investigate a new native lignan vitexin 6 (VB6) in vitro to determine the molecular mechanism underlying its cytotoxicity. We screened and cultured several tumor cell lines and subsequently analyzed VB6 cytotoxicity against 14 different tumor cell lines using a 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. The expression of proteins that regulate apoptosis and autophagy was determined using western blot analysis. VB6 showed an excellent cytotoxic effect against various cancer cell lines in vitro. It induced apoptosis and autophagy of cancer cells. VB6-induced apoptosis showed a time-dependent and concentration-dependent relationship with cleaved poly (ADP-ribose) polymerase, cleaved caspase-3, Bax upregulation, and Bcl-2 downregulation. The levels of Beclin-1 and LC3-II, which are markers for cell autophagy, gradually increased after VB6 treatment. Jun N-terminal kinase (JNK) phosphorylation was increased after VB6 treatment, accompanied by upregulation of P-Bcl-2 and P-C-Jun expression. Cotreatment with a JNK inhibitor significantly decreased VB6-induced cell death and downregulated P-Bcl-2, and cleaved PARP and Beclin-1 expression. The new native lignan VB6 inhibits cancer cell proliferation by activating the JNK pathway. We believe that VB6 could be a valuable chemotherapeutic drug after further evaluation.

Dietary flavonoid and lignan intake and breast cancer risk according to menopause and hormone receptor status in the European Prospective Investigation into Cancer and Nutrition (EPIC) Study

Evidence on the association between dietary flavonoids and lignans and breast cancer (BC) risk is inconclusive, with the possible exception of isoflavones in Asian countries. Therefore, we investigated prospectively dietary total and subclasses of flavonoid and lignan intake and BC risk according to menopause and hormonal receptor status in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. The study included 334,850 women, mostly aged between 35 and 70 years from ten European countries. At baseline, country-specific validated dietary questionnaires were used. A flavonoid and lignan food composition database was developed from the US Department of Agriculture, the Phenol-Explorer and the UK Food Standards Agency databases. Cox regression models were used to analyse the association between dietary flavonoid/lignan intake and the risk of developing BC. During an average 11.5-year follow-up, 11,576 incident BC cases were identified. No association was observed between the intake of total flavonoids [hazard ratio comparing fifth to first quintile (HRQ5-Q1) 0.97, 95 % confidence interval (CI): 0.90-1.04; P trend = 0.591], isoflavones (HRQ5-Q1 1.00, 95 % CI: 0.91-1.10; P trend = 0.734), or total lignans (HRQ5-Q1 1.02, 95 % CI: 0.93-1.11; P trend = 0.469) and overall BC risk. The stratification of the results by menopausal status at recruitment or the differentiation of BC cases according to oestrogen and progesterone receptors did not affect the results. This study shows no associations between flavonoid and lignan intake and BC risk, overall or after taking into account menopausal status and BC hormone receptors.

Dual association between polyphenol intake and breast cancer risk according to alcohol consumption level: a prospective cohort study

Studies of the association between polyphenols dietary intake and breast cancer risk have been limited due to the lack of detailed food composition tables. In addition, none has examined this association according to alcohol intake, despite the facts that alcohol is an established risk factor for breast cancer and that the contribution of alcoholic beverages to polyphenol intake varies according to the level of alcohol consumption. Our objectives were (1) to estimate the associations between breast cancer risk and a wide range of dietary polyphenols using the recently published Phenol-Explorer database; and (2) to evaluate if/how alcohol intake modulates these relationships. 4,141 women from the SU.VI.MAX prospective cohort were followed from 1994 to 2007 (median followup: 12.6 years); 152 developed a first incident invasive primary breast cancer. Dietary intakes were assessed by repeated 24-h records. The Phenol-Explorer database was used to estimate polyphenol intake. Multivariable Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95 % confidence intervals (CIs) for quartiles of polyphenol intake. Analyses were stratified by median alcohol intake (< vs. ≥ 6.5 g/d). In non-to-low alcohol drinkers, intakes of some classes of polyphenols were associated with decreased breast cancer risk: hydroxybenzoic acids (HR(Q4vsQ1) = 0.38, 95 % CI: 0.17-0.86, P (trend) = 0.005), flavonoids (0.35, 0.17-0.75, P (trend) = 0.02), flavonols (0.36, 0.18-0.74, P (trend) = 0.002), catechins (0.48, 0.22-1.05, P (trend) = 0.02), theaflavins (0.42, 0.19-0.93, P (trend) = 0.02), and proanthocyanidins (0.39, 0.18-0.84, P (trend) = 0.02). In contrast, in women with higher alcohol use, intakes of hydroxybenzoic acids (2.28, 1.16-4.49, P (trend) = 0.04), flavonoids (2.46, 1.23-4.92, P (trend) = 0.01), anthocyanins (2.94, 1.32-6.53, P (trend) = 0.01), catechins (2.28, 1.19-4.36, P (trend) = 0.02), and proanthocyanidins (2.98, 1.40-6.33, P (trend) = 0.006) were associated with increased breast cancer risk. In conclusion, this prospective study suggests that several classes of polyphenols could potentially contribute to breast cancer prevention among non-to-low alcohol drinkers, but some may increase breast cancer risk among women with higher alcohol intake.

The blackberry fruit: a review on its composition and chemistry, metabolism and bioavailability, and health benefits

Blackberry (Rubus sp.) fruit contains high levels of anthocyanins and other phenolic compounds, mainly flavonols and ellagitannins, which contribute to its high antioxidant capacity and other biological activities. Blackberry phenolic composition and concentrations are known to be influenced by genetics, growing conditions, and maturation. Despite the current knowledge of their chemistry, research specific to blackberry phenolic compounds' health benefits, metabolism, bioavailability, and mechanism by which they confer health benefits is scarce. Blackberry phenolic compounds have protective effects on age-related neurodegenerative diseases and bone loss in vivo and can inhibit low-density lipoprotein and liposomal oxidation in vitro. Blackberry extracts have also exerted antimutagenic effects in vitro and in vivo by modifying cell signaling pathways and suppressing tumor promotion factors. However, the antiobesity, antidiabetic, antimicrobial, and anti-inflammatory properties of blackberry phenolic compounds need investigation. Similarly, studies that elucidate the in vivo physiologically effective concentrations of blackberry phenolic compounds are necessary.

Dietary intakes of total and specific lignans are associated with clinical breast tumor characteristics

Dietary lignans may affect breast cancer by modifying tumor characteristics likely to affect prognosis. We investigated usual dietary intakes of total and specific lignans with tumor characteristics in 683 women with breast cancer and 611 healthy women without breast cancer enrolled in the Data Bank and BioRepository at Roswell Park Cancer Institute (RPCI). Clinicopathologic data were abstracted from the RPCI breast cancer database. Dietary lignan intakes were calculated from FFQ. OR and 95% CI were estimated with logistic regression adjusting for potential confounders and stratified by menopausal status. Women in the highest compared to the lowest tertile of total lignan intakes had a 40-50% lower odds of breast cancer regardless of menopausal status and substantially reduced odds of an invasive tumor, especially among premenopausal women [OR 0.48 (95% CI 0.26-0.86)]. Lignan intakes were inversely associated with odds of grade 3 tumors among premenopausal women. Lignan intakes were inversely associated with risk of estrogen receptor (ER) negative (ER(-)) breast cancer among premenopausal women [OR 0.16 (95% CI 0.03-0.44)] and particularly triple negative tumors [ER(-), progesterone receptor negative, HER2 negative; OR 0.16 (95% CI 0.04-0.62)]. There were significant differences in the contribution to these effects by specific lignans, especially matairesinol and lariciresinol. In summary, in this case-control study of dietary lignan intakes and breast cancer, we found that higher lignan intakes were associated with lower risks of breast cancer with more favorable prognostic characteristics. Future investigations are warranted to explore the strong associations observed with ER(-) cancer in premenopausal women.

A critical view of the effects of phytoestrogens on hot flashes and breast cancer risk

The increased risk of breast cancer recently observed with some specific estro-progestin associations has raised concerns about the harmful effects of menopausal hormone replacement therapy (HRT). It has been proposed that phytoestrogens (PEs), which have a similar chemical structure to estrogens, could be used as HRT. The main selling points of these preparations concern the management of hot flashes and their potential beneficial effects on breast tissue. In this review, we will address the effects of PE on hot flashes and breast cancer risk as well as the questions raised on a chemical point of view. We conclude that the efficacy of a PE rich diet or nutritional supplements is not clearly established. The use of PE as an alternative for HRT cannot be advocated for now, due to insufficient and conflicting data on efficacy and safety. Moreover, due to the hormone dependence of breast cancer, PE use must be contraindicated in breast cancer survivors.

Can rye intake decrease risk of human breast cancer?

BACKGROUND

Rye contains more fibre and bioactive compounds than other cereals used for bread production. The fibre and compounds of the fibre complex could provide protection against breast cancer (BC).

OBJECTIVE

To review the evidence and theoretical background for a role of rye and some of its components in the prevention of BC.

DESIGN

A short review based to a great extent on the work by scientists in the Nordic countries.

RESULTS

Some of the possible mechanisms by which the fibre complex could reduce BC risk are presented. The fibre through its effect on fermentation increases esterification of bile acids reducing toxicity of the free bile acids and is involved in the production of butyrate with potential anticancer effects including BC. The fibre reduces the enterohepatic circulation of the oestrogens leading to lower plasma oestrogen concentrations. The fibre complex contains bioactive compounds such as lignans and alkylresorcinols that are antioxidative and potentially anticarcinogenic. In addition, vitamins, minerals, and phytic acid in rye may provide protection against BC.

CONCLUSION

Rye products made from wholegrain rye flour are likely to contribute to reduced BC risk.

Reduction in Ki-67 in benign breast tissue of high-risk women with the lignan secoisolariciresinol diglycoside

Preclinical and correlative studies suggest reduced breast cancer with higher lignan intake or blood levels. We conducted a pilot study of modulation of risk biomarkers for breast cancer in premenopausal women after administration of the plant lignan secoisolariciresinol given as the diglycoside (SDG). Eligibility criteria included regular menstrual cycles, no oral contraceptives, a >3-fold increase in 5-year risk, and baseline Ki-67 of ≥2% in areas of hyperplasia in breast tissue sampled by random periareolar fine-needle aspiration (RPFNA) during the follicular phase of the menstrual cycle. SDG (50 mg/d) was given for 12 months, followed by repeat RPFNA. The primary end point was change in Ki-67. Secondary end points included change in cytomorphology, mammographic breast density, serum bioavailable estradiol and testosterone insulin-like growth factor-I and IGF-binding protein-3, and plasma lignan levels. Forty-five of 49 eligible women completed the study with excellent compliance (median = 96%) and few serious side effects (4% grade 3). Median plasma enterolactone increased ∼9-fold, and total lignans increased 16-fold. Thirty-six (80%) of the 45 evaluable subjects showed a decrease in Ki-67, from a median of 4% (range, 2-16.8%) to 2% (range, 0-15.2%; P < 0.001, Wilcoxon signed rank test). A decrease from baseline in the proportion of women with atypical cytology (P = 0.035) was also observed. Based on favorable risk biomarker modulation and lack of adverse events, we are initiating a randomized trial of SDG versus placebo in premenopausal women.

Meta-analyses of lignans and enterolignans in relation to breast cancer risk

BACKGROUND

Epidemiologic studies that examined whether lignans, the most important class of phytoestrogens in the Western diet, protect against breast cancer have yielded inconsistent results.

OBJECTIVE

In this study, we conducted meta-analyses on the association between lignans and breast cancer risk.

DESIGN

We performed a systematic MEDLINE search to identify epidemiologic studies published between 1997 and August 2009. We calculated pooled risk estimates (REs) for total lignan exposure, dietary lignan intake, enterolignan exposure, and blood or urine concentrations of enterolactone and according to menopausal and estrogen receptor (ER) status of tumors.

RESULTS

We included 21 studies (11 prospective cohort studies and 10 case-control studies) in the meta-analyses. Lignan exposure was not associated with an overall breast cancer risk (RE: 0.92; 95% CI: 0.81, 1.02; P for heterogeneity = 0.004). However, in postmenopausal women, high lignan intake was associated with a significant reduced risk of breast cancer (13 studies; RE: 0.86; 95% CI: 0.78, 0.94; P for heterogeneity = 0.32). Breast cancer risk was also inversely associated with enterolignan exposure (4 studies; RE: 0.84; 95% CI: 0.71, 0.97) but not with blood or urine enterolactone concentrations. The associations were not significantly different between ER-status subgroups (6 studies).

CONCLUSIONS

High lignan exposure may be associated with a reduced breast cancer risk in postmenopausal women. Additional work is warranted to clarify the association between lignan exposure and breast cancer risk.

Estrogen receptor-dependent genomic expression profiles in breast cancer cells in response to fatty acids

CONTEXT

The estrogen receptor (ER) status in breast cancer plays a major role in the progression and metastatic potential of breast cancer in women. Breast cancer cells lacking the ER are usually more advanced and more difficult to treat than ER+ breast cancer cells. ER- women have more advanced breast cancer at the time of diagnosis than ER+ women. ER- breast cancer cells in women, regardless of age, are more likely to have tumor Grade III or IV with fewer Grade I and II tumor stages combined for each individual stage group. Studies have suggested a strong correlation between fat intake and the elevated risk of ER+ breast cancer cells.

MATERIALS AND METHODS

We studied the role of ER status on the gene expression in breast cancer cells in response to omega-3 and omega-6 fatty acids using microarrays. We have studied gene expression patterns in 8 breast cancer cell lines (4 ER- and 4 ER+) in response to Eicosapentanoic (EPA) and Arachidonic (AA) acids.

STATISTICAL ANALYSIS

Analysis of Variance (ANOVA) t-test analysis was carried out to identify genes differentially expressed between the two groups.

RESULTS

We identified genes which were significantly correlated with the ER status when breast cancer cells were treated with these fatty acids.

CONCLUSION

We have determined ER-related gene expression patterns in breast cancer cells in response to fatty acids. Additional studies of these biomarkers may enlighten the importance of the ER status on the mechanistic and therapeutic roles of fatty acids in breast cancer.

Breast, colorectal, and prostate cancer risk in the European Prospective Investigation into Cancer and Nutrition-Norfolk in relation to phytoestrogen intake derived from an improved database

BACKGROUND

The characterization of phytoestrogen intake and cancer risk has been hindered by the absence of accurate dietary phytoestrogen values.

OBJECTIVE

We examined the risk of breast, colorectal, and prostate cancers relative to phytoestrogen intake on the basis of a comprehensive database.

DESIGN

Demographic and anthropometric characteristics, a medical history, and 7-d records of diet were collected prospectively from participants (aged 40-79 y) in the European Prospective Investigation into Cancer and Nutrition-Norfolk (EPIC-Norfolk). Five hundred nine food items were analyzed by liquid chromatography-mass spectrometry/mass spectrometry, and (13)C(3)-labeled internal standards were analyzed for isoflavones (genistein, daidzein, glycitein, biochanin A, and formononetin), lignans (secoisolariciresinol and matairesinol), and enterolignans from gut microbial metabolism in animal food sources (equol and enterolactone). From the direct analysis, values for 10,708 foods were calculated. Odds ratios (ORs) for breast (244 cases, 941 controls), colorectal (221 cases, 886 controls), and prostate (204 cases, 812 controls) cancers were calculated relative to phytoestrogen intake.

RESULTS

Phytoestrogen intake was not associated with breast cancer among women or colorectal cancer among men. Among women, colorectal cancer risk was inversely associated with enterolactone (OR: 0.33; 95% CI: 0.14, 0.74) and total enterolignans (OR: 0.32; 95% CI: 0.13, 0.79), with a positive trend detected for secoisolariciresinol (OR: 1.60; 95% CI: 0.96, 2.69). A positive trend between enterolignan intake and prostate cancer risk (OR: 1.27; 95% CI: 0.97, 1.66) was attenuated after adjustment for dairy intake (OR: 1.19; 95% CI: 0.77, 1.82).

CONCLUSION

Dietary phytoestrogens may contribute to the risk of colorectal cancer among women and prostate cancer among men.

Dietary lignan intakes in relation to survival among women with breast cancer: the Western New York Exposures and Breast Cancer (WEB) Study

Dietary lignan intakes have been associated with reduced breast cancer risks; however, no previous studies have investigated whether lignan intake might be associated with breast cancer survival. We examined the association of dietary lignan intakes with survival in 1122 women with primary, incident, histologically confirmed breast cancer identified between 1996 and 2001, and with vital status determined through December 31, 2006. Diet in the 12-24 months before diagnosis was assessed with an extensive food frequency questionnaire, and potential confounders assessed from an extensive epidemiologic interview and abstracted clinical data. Lignan intake was calculated using published food composition data. Hazard ratios (HR), and 95% confidence intervals (CIs) for dietary lignan intakes with all cause, and breast cancer mortality were estimated using Cox proportional hazards adjusting for age, education, race, total energy intake, tumor stage, and body mass index. Of the 1122 women with complete dietary data, 160 had died by the end of follow-up. Among postmenopausal women only, those in the highest versus lowest quartile of lignan intakes had a statistically significant reduction in the risk of all cause mortality (HR 0.49, 95% CI 0.26-0.91) and a significantly reduced risk of breast cancer mortality (HR 0.29, 95% CI 0.11-0.76). Higher intakes of dried beans (HR 0.61, 95% CI 0.36-1.03), but not fruits, vegetables, or grains, were also weakly associated with overall mortality. In summary, our results suggest that higher lignan intakes may be associated with improved survival among postmenopausal women with breast cancer.

Flaxseed and pure secoisolariciresinol diglucoside, but not flaxseed hull, reduce human breast tumor growth (MCF-7) in athymic mice

Previous studies have shown that dietary flaxseed (FS) can reduce the growth of established human breast tumors in athymic mice with low circulating estrogen concentrations. In this study, we determined the effect of FS compared with pure lignan at the level it is present in FS [secoisolariciresinol diglucoside (SDG)] and to the lignan-rich fraction [FS hull (FH)] on human breast tumor growth and their potential mechanisms of action. Ovariectomized, athymic mice, each with an implanted 17 beta-estradiol (E2) pellet (0.36 mg), were injected with human estrogen receptor (ER) positive breast cancer cells (MCF-7). When tumors were established, the E2 pellet was removed. Mice were fed either the control basal diet (BD), FS (100 g/kg diet), SDG (1 g/kg diet), or FH (18 g/kg diet) for 8 wk. Compared with the BD, FS and SDG significantly decreased the palpable tumor size, but effects of FS, SDG, and FH did not differ from one another. All treatments significantly inhibited cell proliferation, but only FS and SDG induced significantly higher apoptosis. Both FS and SDG significantly decreased mRNA expressions of Bcl2, cyclin D1, pS2, ERalpha, and ERbeta, epidermal growth factor receptor, and insulin-like growth factor receptor. FS also reduced human epidermal growth factor receptor 2 mRNA and SDG decreased phospho-specific mitogen-activated protein kinase expression. FH did not significantly reduce these biomarkers. In conclusion, pure SDG has a similar effect as FS in reducing tumor growth and in mechanisms of action, including downregulating ER- and growth factor-mediated cell signaling. The lesser effects of FH indicate a need for a higher dose to be more effective.

Dietary patterns and breast cancer risk in women participating in the Black Women's Health Study

BACKGROUND

No studies have examined dietary patterns and breast cancer risk in a large cohort of African American women.

OBJECTIVE

We investigated the association between dietary patterns and breast cancer risk in the Black Women's Health Study.

DESIGN

This is a prospective cohort study of 50,778 participants followed biennially from 1995 through 2007. During 443,742 person-years of follow-up, 1094 incident cases of breast cancer were identified. Factor analysis was used to derive food patterns based on 69 food variables. We used Cox regression models to obtain incident rate ratios (IRRs) for breast cancer in relation to quintiles of each of the 2 dietary patterns, with adjustment for other breast cancer risk factors.

RESULTS

Through factor analysis, we identified 2 dietary patterns: Western (refined grains, processed meat, and sweets) and prudent (whole grains, vegetables, fruit, and fish). The prudent diet was weakly associated with lower breast cancer risk overall; P for trend = 0.06. In analyses stratified by body mass index (BMI; in kg/m(2)), the prudent dietary pattern was associated with a significantly lower risk of breast cancer in women with a BMI <25 (IRR: 0.64; 95% CI: 0.43, 0.93; P for trend = 0.01). The prudent dietary pattern was also associated with a significantly lower risk of breast cancer in premenopausal women (IRR: 0.70; 95% CI: 0.52, 0.96; P for trend = 0.01), and we found a significant inverse association for the prudent dietary pattern and estrogen receptor-negative breast cancer (IRR: 0.52; 95% CI: 0.28, 0.94; P for trend <0.01).

CONCLUSION

Our findings suggest that the prudent dietary pattern may protect against breast cancer in some black women.

Lignans and breast cancer risk in pre- and post-menopausal women: meta-analyses of observational studies

Phyto-oestrogens are plant compounds structurally similar to oestradiol, which have been proposed to have protective effects against breast cancer. The main class of phyto-oestrogens in the Western diet is lignans. Literature reports on the effect of lignans in breast cancer risk have been conflicting. We performed three separate meta-analyses to examine the relationships between (i) plant lignan intake, (ii) enterolignan exposure and (iii) blood enterolactone levels and breast cancer risk. Medline, BIOSIS and EMBASE databases were searched for publications up to 30 September 2008, and 23 studies were included in the random effects meta-analyses. Overall, there was little association between high plant lignan intake and breast cancer risk (11 studies, combined odds ratio (OR): 0.93, 95% confidence interval (95% CI): 0.83-1.03, P=0.15), but this association was subjected to marked heterogeneity (I(2)=44%). Restricting the analysis to post-menopausal women, high levels of plant lignan intake were associated with reduced breast cancer risk (7 studies, combined OR: 0.85, 95% CI: 0.78, 0.93, P<0.001) and heterogeneity was markedly reduced (I(2)=0%). High enterolignan exposure was also associated with breast cancer (5 studies, combined OR: 0.73, 95% CI: 0.57, 0.92, P=0.009) but, again, there was marked heterogeneity (I(2)=63%). No association was found with blood enterolactone levels (combined OR: 0.82, 95% CI: 0.59-1.14, P=0.24). In conclusion, plant lignans may be associated with a small reduction in post-menopausal breast cancer risk, but further studies are required to confirm these results.

Do phytoestrogens reduce the risk of breast cancer and breast cancer recurrence? What clinicians need to know

Oestrogen is an important determinant of breast cancer risk. Oestrogen-mimicking plant compounds called phytoestrogens can bind to oestrogen receptors and exert weak oestrogenic effects. Despite this activity, epidemiological studies suggest that the incidence of breast cancer is lower in countries where the intake of phytoestrogens is high, implying that these compounds may reduce breast cancer risk, and possibly have an impact on survival. Isoflavones and lignans are the most common phytoestrogens in the diet. In this article, we present findings from human observational and intervention studies related to both isoflavone and lignan exposure and breast cancer risk and survival. In addition, the clinical implications of these findings are examined in the light of a growing dietary supplement market. An increasing number of breast cancer patients seek to take supplements together with their standard treatment in the hope that these will either prevent recurrence or treat their menopausal symptoms. Observational studies suggest a protective effect of isoflavones on breast cancer risk and the case may be similar for increasing lignan consumption although evidence so far is inconsistent. In contrast, short-term intervention studies suggest a possible stimulatory effect on breast tissue raising concerns of possible adverse effects in breast cancer patients. However, owing to the dearth of human studies investigating effects on breast cancer recurrence and survival the role of phytoestrogens remains unclear. So far, not enough clear evidence exists on which to base guidelines for clinical use, although raising patient awareness of the uncertain effect of phytoestrogens is recommended.

Dietary phytoestrogens are not associated with risk of overall breast cancer but diets rich in coumestrol are inversely associated with risk of estrogen receptor and progesterone receptor negative breast tumors in Swedish women

Results from epidemiological and experimental studies indicate that phytoestrogens may protect against breast cancer. Because one of the biological effects of phytoestrogens is probably estrogenic, it's possible that the preventive effect on breast cancer differs by estrogen receptor (ER) or progesterone receptor (PR) status of the tumor. We evaluated the associations between dietary phytoestrogen (isoflavonoids, lignans, and coumestrol) intake and risk of breast cancer and whether the ER/PR statuses of the tumor influence this relationship. In 1991-2 a prospective population-based cohort study among Swedish pre- and postmenopausal women was performed, making questionnaire data available for 45,448 women. A total of 1014 invasive breast cancers were diagnosed until December 2004. Cox proportional hazards models were performed to estimate multivariate risk ratios, 95% CI for associations with risk of breast cancer. Intakes of lignan, isoflavonoid, or coumestrol were not associated with breast cancer risk overall or before or after 50 y of age. The effects of lignans or isoflavonoids were independent of receptor status. However, intake of coumestrol was associated with decreased risk of receptor negative tumors (ER-PR-) but not positive tumors. The risk of ER-PR- tumors was significantly lower (50%) in women with intermediate coumestrol intake compared with those who did not consume any. In conclusion, we found no association between intake of isoflavonoids or lignans and breast cancer risk. Our results of a decreased risk of ER-PR- tumors in women with intermediate intake of coumestrol could be due to chance because of the low intake. The results should be confirmed in other studies.

Breast cancer risk in relation to urinary and serum biomarkers of phytoestrogen exposure in the European Prospective into Cancer-Norfolk cohort study

INTRODUCTION

Phytoestrogens are a group of compounds found in plants that structurally resemble the hormone oestradiol, and thus have the potential to act as oestrogen agonists or antagonists. Their potential effects may alter the risk of breast cancer, but only a limited range of phytoestrogens has been examined in prospective cohort studies.

METHODS

Serum and urine samples from 237 incident breast cancer cases and 952 control individuals (aged 45 to 75 years) in the European Prospective into Cancer-Norfolk cohort were analysed for seven phytoestrogens (daidzein, enterodiol, enterolactone, genistein, glycitein, o-desmethylangolensin, and equol) using liquid chromatography/mass spectrometry. Data on participants' diet, demographics, anthropometrics, and medical history were collected upon recruitment. All models were adjusted for weight, fat and energy intake, family history of breast cancer, social class, analytical batch, and factors related to oestrogen exposure.

RESULTS

Urinary or serum phytoestrogens were not associated with protection from breast cancer in the European Prospective into Cancer-Norfolk cohort. Breast cancer risk was marginally increased with higher levels of total urinary isoflavones (odds ratio = 1.08 (95% confidence interval = 1.00 to 1.16), P = 0.055); among those with oestrogen receptor-positive tumours, the risk of breast cancer was increased with higher levels of urinary equol (odds ratio = 1.07 (95% confidence interval = 1.01 to 1.12), P = 0.013).

CONCLUSION

There was limited evidence of an association between phytoestrogen biomarkers and breast cancer risk in the present study. There was no indication of decreased likelihood of breast cancer with higher levels of phytoestrogen biomarkers, but the observation that some phytoestrogen biomarkers may be associated with greater risk of breast cancer warrants further study with greater statistical power.

Lignans and human health

This review focuses on the possible role in human health of the consumption of lignan-rich foods. Most of the plant lignans in human foods are converted by the intestinal microflora in the upper part of the large bowel to enterolactone and enterodiol, called mammalian or enterolignans. The protective role of these compounds, particularly in chronic Western diseases, is discussed. Evidence suggests that fiber- and lignan-rich whole-grain cereals, beans, berries, nuts, and various seeds are the main protective foods. Many factors, in addition to diet, such as intestinal microflora, smoking, antibiotics, and obesity affect circulating lignan levels in the body. Lignan-rich diets may be beneficial, particularly if consumed for life. Experimental evidence in animals has shown clear anticarcinogenic effects of flaxseed or pure lignans in many types of cancer. Many epidemiological results are controversial, partly because the determinants of plasma enterolactone are very different in different countries. The source of the lignans seems to play a role because other factors in the food obviously participate in the protective effects. The results are promising, but much work is still needed in this area of medicine.

Dietary lignans and postmenopausal breast cancer risk by oestrogen receptor status: a prospective cohort study of Swedish women

Among the 51 823 postmenopausal women in the Swedish Mammography Cohort, we investigated breast cancer risk in relation to the FFQ-based estimated lignan intake by oestrogen receptor (ER) and progesterone receptor (PR) subtypes. A significant 17% risk reduction for breast cancer overall in the high lignan quartile was observed, especially among PMH user (P_interaction<0.010), but no heterogeneity across ER/PR subtypes.

Differential effects of soybean and fenugreek extracts on the growth of MCF-7 cells

The effect of aqueous and ethanol extracts of soybean and fenugreek on the growth of MCF-7 cells, an estrogen receptor positive breast cancer cell line, has been examined in this study. Soybean is well known for the presence of phytoestrogens and fenugreek is reported to have medicinal use including anticancer properties. In a dose dependent manner soybean aqueous and ethanol extract promoted the growth and DNA synthesis in MCF-7 cells. On the contrary ethanol extract of fenugreek decreased the cell viability and induced early apoptotic changes such as flipping of phosphatidylserine and decrease of mitochondrial membrane potential. Degradation of cellular DNA into fragments comprising multiples of approximately 180-200 base pair was also observed. Cell cycle analysis by flow cytometry showed the presence of a subG1 apoptotic population which was more prominent at higher concentrations along with cell cycle arrest at G2/M phase. Our experiments show that while the soybean extract acts as a promoter of MCF-7 cell growth, the fenugreek extract induces apoptosis.

Microwave-assisted extraction of the main phenolic compounds in flaxseed

A microwave-assisted extraction (MAE) method has been applied for the first time to the extraction of the main lignan, secoisolariciresinol diglucoside (SDG), and the two most concentrated hydroxycinnamic acid glucosides in flaxseed. The effects of microwave power, extraction time and alkaline treatment were investigated. It was shown that a 3 min MAE resulted in an SDG content of 16.1+/-0.4 mg/g, a p-coumaric acid glucoside content of 3.7+/-0.2 mg/g and a ferulic acid glucoside content of 4.1+/-0.2 mg/g. These values were compared with those obtained using conventional extraction methods and the results demonstrated that MAE was more effective in terms of both yield and time consumption.

Dietary lignan intake and postmenopausal breast cancer risk by estrogen and progesterone receptor status

BACKGROUND

Studies conducted in Asian populations have suggested that high consumption of soy-based foods that are rich in isoflavone phytoestrogens is associated with a reduced risk of breast cancer. However, the potential associations of other dietary phytoestrogens--i.e., the lignans or their bioactive metabolites, the enterolignans--with the risk of breast cancer are unclear.

METHODS

We prospectively examined associations between the risk of postmenopausal invasive breast cancer and dietary intakes of four plant lignans (pinoresinol, lariciresinol, secoisolariciresinol, and matairesinol) and estimated exposure to two enterolignans (enterodiol and enterolactone), as measured with a self-administered diet history questionnaire, among 58,049 postmenopausal French women who were not taking soy isoflavone supplements. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated using multivariable Cox proportional hazards regression models. Analyses were further stratified by the combined estrogen and progesterone receptor (ER/PR) status of the tumors. Statistical tests were two-sided.

RESULTS

During 383,425 person-years of follow-up (median follow-up, 7.7 years), 1469 cases of breast cancer were diagnosed. Compared with women in the lowest intake quartiles, those in the highest quartile of total lignan intake (>1395 microg/day) had a reduced risk of breast cancer (RR = 0.83, 95% CI = 0.71 to 0.95, P(trend) = .02, 376 versus 411 cases per 100,000 person-years), as did those in the highest quartile of lariciresinol intake (RR = 0.82, 95% CI = 0.71 to 0.95, P(trend) = .01). The inverse associations between phytoestrogen intakes and postmenopausal breast cancer risk were limited to ER- and PR-positive disease (e.g., RR for highest versus lowest quartiles of total plant lignan intake = 0.72, 95% CI = 0.58 to 0.88, P(trend) = .01, 174 versus 214 cases per 100,000 person-years, and RR for highest versus lowest quartiles of total enterolignan level = 0.77, 95% CI = 0.62 to 0.95, P(trend) = .01, 164 versus 204 cases per 100,000 person-years).

CONCLUSIONS

High dietary intakes of plant lignans and high exposure to enterolignans were associated with reduced risks of ER- and PR-positive postmenopausal breast cancer in a Western population that does not consume a diet rich in soy.