Soy for breast cancer survivors: a critical review of the literature

Enhanced effects of 1,25(OH)(2)D(3) plus genistein on adipogenesis and apoptosis in 3T3-L1 adipocytes

OBJECTIVE

To investigate the ability of 1,25(OH)(2)D(3) (D) and genistein (G), alone and in combination, to inhibit adipogenesis and induce apoptosis in 3T3-L1 adipocytes.

METHODS AND PROCEDURES

3T3-L1 preadipocytes and mature adipocytes were incubated with various concentrations of D and G, alone and in combination, for 48 h. Viability was determined using the Cell Titer 96 Aqueous One Solution Cell Proliferation Assay. Post-confluent preadipocytes were incubated with D and G for up to 6 days during adipogenesis and lipid content was quantified by Nile Red dye; apoptosis was quantified by measurement of single-stranded DNA. Expression of adipocyte-specific proteins and VDR was analyzed by western blotting.

RESULTS

Combining D and G did not cause an enhanced effect on cell viability in either preadipocytes or mature adipocytes. In maturing preadipocytes, D at 0.5 nmol/l (D0.5) increased apoptosis by 47 +/- 10.25% (P < 0.05) and inhibited lipid accumulation by 28 +/- 10% (P < 0.001), while G at 25 micromol/l (G25) had no significant effect. However, D+G caused an enhanced apoptosis by 136 +/- 12.6% (P < 0.001) and enhanced inhibition of lipid accumulation by 82.46 +/- 2.95% (P < 0.001). Similarly, D0.5 alone decreased adipose-specific gene 422 (aP2) expression to 34.2 +/- 2.3% and increased VDR expression levels by 41.8 +/- 11% (P < 0.001), but G25 showed no effect. However, D0.5+G25 decreased aP2 expression to 52 +/- 4.2% (P < 0.05) and increased VDR expression levels by 131 +/- 14.5% (P < 0.0001).

DISCUSSION

These findings suggest that combining 1,25(OH)(2)D(3) with genistein results in an enhanced inhibition of lipid accumulation and induction of apoptosis in maturing 3T3-L1 preadipocytes.

Dietary soy isoflavone-aglycone lowers food intake in female rats with and without ovariectomy

OBJECTIVE

Estrogens downregulate eating behavior, and soy isoflavones are known to be estrogenic agents. We aimed to examine whether the estrogenic property of soy isoflavones can affect food intake and body weight.

METHODS AND PROCEDURES

Seven-week-old male, female, and ovariectomized (OVX) Sprague-Dawley rats were given free access to a diet containing 100-300 mg total isoflavone/kg diet, or to a control diet, either with or without concurrent administration of estradiol by subcutaneous implantation.

RESULTS

Dietary soy isoflavone was shown to lower food intake in female rats, whether or not the animals had undergone ovariectomy. Administration of estradiol lowered the food intake in male rats and in OVX female rats. The decrease in weekly food intake in female rats led to a reduction in their weekly gain in body weight. Dietary soy isoflavone significantly increased the concentration of serum isoflavones, especially equol (a metabolite of daidzein), regardless of gender or ovariectomy. Dietary soy isoflavone did not affect either serum estradiol concentration or uterine and didymus weights, but estradiol administration improved the uterine atrophy in OVX rats, and decreased the didymus weight in male rats.

DISCUSSION

Soy isoflavone lowers the food intake in female rats, but not in the male animals. Contrary to the hypothesis currently in vogue, the reduction in food intake caused by soy isoflavone may not be a purely estrogenic effect. This follows from the finding that the effects of soy isoflavones on food intake and on the reproductive organs differ from the corresponding effects produced by estrogen.

Resveratrol potentiates genistein's antiadipogenic and proapoptotic effects in 3T3-L1 adipocytes

Genistein (G) and resveratrol (R) individually inhibit adipogenesis in 3T3-L1 adipocytes and induce apoptosis in cancer cells. We investigated whether the combination of G and R resulted in enhanced effects on adipogenesis, lipolysis, and apoptosis in 3T3-L1 cells. Preadipocytes and mature adipocytes were treated with G and R individually at 50 and 100 micromol/L (G100; R100) and in combination. Both in preadipocytes and mature adipocytes, G and R individually decreased cell viability dose-dependently, but G100 + R100 further decreased viability by 59 +/- 0.97% (P < 0.001) and 69.7 +/- 1.2% (P < 0.001) after 48 h compared with G100 and R100, respectively. G100 + R100 induced apoptosis 242 +/- 8.7% (P < 0.001) more than the control after 48 h, whereas G100 and R100 individually increased apoptosis only 46 +/- 9.2 and 46 +/- 7.9%, respectively. G and R did not modulate mitogen-activated protein kinase expression by themselves, but G100 + R100 increased Jun-N-terminal kinase phosphorylation by 38.8 +/- 4.4% (P < 0.001) and decreased extracellular signal-regulating kinase phosphorylation by 48 +/- 3.4% (P < 0.001). Individually, G and R at 25 micromol/L (G25; R25) decreased lipid accumulation by 30 +/- 1.7% and 20.07 +/- 4.27%, respectively (P < 0.001). However, G25 + R25 decreased lipid accumulation by 77.9 +/- 3.4% (P < 0.001). Lipolysis assay revealed that neither G25 nor R25 induced lipolysis, whereas G25 + R25 significantly increased lipolysis by 25.5 +/- 4.6%. The adipocyte-specific proteins PPARgamma and CCAAT/enhancer binding protein-alpha were downregulated after treatment with G + R, but no effect was observed with individual compounds. These results indicate that G and R in combination produce enhanced effects on inhibiting adipogenesis, inducing apoptosis, and promoting lipolysis in 3T3-L1 adipocytes. Thus, the combination of G and R is more potent in exerting antiobesity effects than the individual compounds.

Isolation and identification of novel estrogenic compounds in yam tuber (Dioscorea alata Cv. Tainung No. 2)

Yam (Dioscorea spp.) is a common food in tropical areas and has been shown to improve the status of sex hormone in postmenopausal women. In this study, the estrogenic activity of yam was examined and active compounds were isolated and identified based on ligand-dependent transcriptional activation through estrogen receptors. Ethyl acetate extracts of various species/varieties of yam were found to activate estrogen receptors alpha and beta to various extents. The extract of Dioscorea alata cv. Tainung No. 2 tuber was fractionated by repeated silica gel column chromatography. The active compounds were isolated and purified by preparative HPLC. Based on NMR and mass spectrometry, two new compounds, hydro-Q(9) chromene (1) and gamma-tocopherol-9 (2), together with three known compounds, RRR-alpha-tocopherol (3), coenzyme Q(9) (4), and 1-feruloylglycerol (5), were identified and shown to activate human ERalpha and beta. These results provide basic evidence for the beneficial effect of yam for menopausal women.

Genistein affects HER2 protein concentration, activation, and promoter regulation in BT-474 human breast cancer cells

The HER2 proto-oncogene, a member of the epidermal growth factor receptor family, is overexpressed in 20-30% of breast cancers. Genistein, the main soy isoflavone, interacts with estrogen receptors (ER) and it is also a potent tyrosine kinase inhibitor. Previously, our laboratory found that genistein delayed mammary tumor onset in transgenic mice that overexpress HER2 gene. Our goal was to define the mechanism through which genistein affects mammary tumorigenesis in HER2 overexpressing mice. We hypothesized that genistein inhibits HER2 activation and expression through ER-dependent and ER-independent mechanisms. Genistein inhibited total HER2 protein expression and tyrosine phosphorylation in BT-474, an ERalpha (-) and ERbeta (+) human breast cancer cell line, however, E2 had no effect. Taken together, these data suggest that genistein has an ER-independent inhibitory effect, presumably, through tyrosine kinase inhibition activity. Genistein at 1.0 microM mimicked E2 and down-regulated HER2 protein phosphorylation when BT-474 was co-transfected with ERalpha, but not ERbeta. Although E2 and overexpression of HER2 can promote mammary tumorigenesis, an inverse relationship between ER expression and HER2 overexpression has been found in human breast cancer. We cloned a 500-bp promoter region upstream of the HER2 transcription initiation site. Co-transfection with ERalpha, but not with ERbeta, down-regulated HER2 promoter reporter in BT-474. At concentrations > or =1 microM, genistein inhibited HER2 promoter reporter in the absence of ERalpha. In conclusion, genistein at > or =1 microM inhibited HER2 protein expression, phosphorylation, and promoter activity through an ER-independent mechanism. In the presence of ERalpha, genistein mimicked E2 and inhibited HER2 protein phosphorylation. These data support genistein's chemo-prevention and potential chemo-therapeutic roles in breast cancer.

Can the combination of flaxseed and its lignans with soy and its isoflavones reduce the growth stimulatory effect of soy and its isoflavones on established breast cancer?

Consumption of phytoestrogen (PE)-rich foods (i. e., soy and flaxseed (FS)) is increasing because of their suggested health benefits. However, recent studies raise concern over the safety of soy and its isoflavones, particularly genistein (GEN), for postmenopausal breast cancer (BC), due to their potential stimulatory effects on human breast tissue and on the growth of existing tumors in rodents. FS, rich in PE lignans, which is metabolized to the mammalian lignans enterolactone (ENL) and enterodiol (END), has consistently been shown to have tumor inhibitory effects in a human clinical trial as well as rodent BC models. Using the preclinical athymic mouse postmenopausal BC model, combining FS with soy protein or GEN with END and ENL, was found to negate the tumor stimulatory effects of soy protein or GEN alone. The mechanism may be related to the modulation of estrogen receptor and MAPK signaling pathways. If these studies can be confirmed in clinical trials, then consumption of combined soy and FS, or their PEs, may reduce the tumor growth stimulatory effect of soy or GEN. This may indicate that if soy is consumed with lignan-rich foods, it may continue to induce its other beneficial health effects, without inducing adverse effect on postmenopausal BC.

Cell-surface H+-ATP synthase as a potential molecular target for anti-obesity drugs

Here we show that the cell-surface expression of the alpha subunit of H(+)-ATP synthase is markedly increased during adipocyte differentiation. Treatment of differentiated adipocytes with small molecule inhibitors of H(+)-ATP synthase or antibodies against alpha and beta subunits of H(+)-ATP synthase leads to a decrease in cytosolic lipid droplet accumulation. Apolipoprotein A-I, which has been shown to bind to the ectopic beta-chain of H(+)-ATP synthase and inhibit the activity of cell-surface H(+)-ATP synthase, also was found to inhibit cytosolic lipid accumulation. These results suggest that the cell-surface H(+)-ATP synthase has a previously unsuspected role in lipid metabolism in adipocytes.

Age-related uterotrophic response of soy isoflavone intake in rats

This study investigated the effects of soy isoflavone intake on uterotrophic responses in growing (juvenile) and adult female rats. In the growing rats, feed intake showed a decreasing trend as the level of dietary isoflavones increased to 0.02%, 0.1%, and 0.2% of the diets. However, in the case of the adult rats there were no significant differences among groups. Weight gains were significantly lower in the rats fed 0.1% and 0.2% isoflavones than the controls in both juvenile and adult rats. The urinary excretion of daidzein and genistein was significantly increased with increasing levels of dietary isoflavones. The calculated urinary recoveries of daidzein and genistein were significantly lower in the groups fed 0.1% and 0.2% isoflavones compared to the juvenile and adult rat groups fed 0.02% isoflavones; no significant difference was observed between the 0.1% and 0.2% groups. The calculated urinary recoveries of daidzein and genistein in the adult rats were significantly higher than in the juvenile rats. The differences in the urinary recoveries between ages may be due to greater availability of the isoflavones in the adult rats. Isoflavone supplementation did not alter the histological phenotype of endometrial cells in growing rats, but a hyperplastic response of endometrium was shown in the adult rats. Dietary isoflavones, therefore, may not have an estrogenic effect on the uterus at these dose levels during the growth period, but this organ would be expected to be a likely target for isoflavone action in adults. We observed in the present study that isoflavones are more bioavailable in adult rats than in the juvenile rats. Therefore, soy isoflavone supplementation may not act as an endocrine disrupter during the growth period but may exert a phytoestrogenic effect on the uterus of adult rats.

Soy phytochemicals synergistically enhance the preventive effect of tamoxifen on the growth of estrogen-dependent human breast carcinoma in mice

The objective of this work was to determine the interactive effects between soy bioactive components and tamoxifen (TAM) on prevention of estrogen-dependent breast cancer (BRCA). We initially investigated the effects of soy isoflavone genistein and TAM on the growth and cell cycle progression of estrogen-dependent MCF-7 human BRCA cells, and on the expression of ERalpha, pS2 and EGFR genes in vitro. Genistein or TAM alone inhibited the growth of MCF-7 cells in part via G(1) phase arrest, but their combinations showed suggestive antagonistic effects. We further evaluated the effects of bioactive soy components and TAM on the growth inhibition of MCF-7 tumors in a clinically relevant breast tumor model. TAM and bioactive soy components, genistein and soy phytochemical concentrate (SPC), delayed the growth of MCF-7 tumors. The combination of TAM with genistein or SPC, especially at the lower dose of TAM, had synergistic effects on delaying the growth of MCF-7 tumors. Biomarker determination suggests that the combination of TAM and soy components may synergistically delay the growth of MCF-7 tumors via their combined effects on induction of tumor cell apoptosis and inhibition of tumor cell proliferation. In addition, genistein and TAM combination synergistically delayed the growth of breast tumor via decreased estrogen level and activity, and down-regulation of EGFR expression. The results from our studies suggest that further investigations may be warranted to determine if the combination of TAM and bioactive soy components may be used for prevention and/or treatment of estrogen-dependent BRCA.

Tamoxifen, soy, and lifestyle factors in Asian American women with breast cancer

PURPOSE

Soy foods have been a staple in Asia for centuries but the consumption of this food in the West is recent. Intake of soy among women at high risk for or with breast cancer has become a public health concern because genistein, a major component of soy, has weak estrogenic effects on breast epithelium, and has been found to negate the benefit of tamoxifen in some animal and in vitro studies.

PATIENTS AND METHODS

We conducted a cross-sectional study in Asian Americans with breast cancer who were tamoxifen users (n = 380) to investigate the association between soy intake and circulating levels of tamoxifen and its metabolites (N-desmethyl tamoxifen [N-DMT], 4-hydroxytamoxifen [4-OHT], and 4-hydroxy-N-desmethyl-tamoxifen [endoxifen]).

RESULTS

Serum levels of tamoxifen or its metabolites were unrelated to self-reported intake of soy or serum levels of isoflavones. Blood levels of tamoxifen were 81% higher in postmenopausal women age 65 or older compared with premenopausal women age 45 or younger (P = .005); similar patterns of results were observed for the tamoxifen metabolites. Levels of N-DMT were 27% (P = .03) lower among women in the highest tertile of body mass index (BMI, > 24.4 kg/m2) compared with those in the lowest category (BMI 21.5). Women who used hypertensive medications had higher levels of tamoxifen (P = .02) and N-DMT (P = .04) compared with nonusers.

CONCLUSION

We found no evidence that soy intake adversely affected levels of tamoxifen or its metabolites. However, age, menopausal status, BMI, and use of hypertensive medications significantly influenced circulating levels of tamoxifen and its metabolites in this population.

Resveratrol induces apoptosis in chemoresistant cancer cells via modulation of AMPK signaling pathway

Resveratrol has been reported to possess therapeutic effects for various cancers including colon cancers. In this article, the molecular basis of resveratrol with emphasis on its ability to control intracellular signaling cascades of adenosine monophosphate (AMP)-activated protein kinase (AMPK) responsible for inducing apoptosis in drug-resistant cancer cells was investigated. Recently, the evolutionarily conserved serine/threonine kinase, AMPK, emerges as a possible target molecule of cancer control. We have investigated the effects of resveratrol on apoptosis in relation to AMPK in HT-29 cells shown chemoresistant to a cancer chemotherapeutic drug, etoposide. Resveratrol exhibited a variety of molecular events in etoposide-based combination therapy in HT-29 colon cancer cells including the AMPK activation, inhibition of cell growth, induction of apoptosis, and reactive oxygen species (ROS) generation. The involvement of AMPK signaling cascade in resveratrol-based cancer therapy was clearly shown by comparing the conditions of AMPK activated states and inactivated states. We have identified ROS as an upstream regulator of AMPK. Further investigation warrants to elucidate the mechanism by which resveratrol generates ROS and AMPK activation.

Modifiable Risk Factors for Breast Cancer Recurrence: What Can We Tell Survivors?

The potential for recurrence causes considerable distress for breast cancer survivors. Major information sources for survivors and providers offer few clear recommendations for postdiagnosis lifestyle change related to recurrence. To design interventions to improve long-term survivors' care and quality of life, we must know what survivors are doing to prevent recurrence in the absence of solid evidence, whether survivors' perceptions and behaviors correspond to hypothesized modifiable risk factors for recurrence, and whether survivors are adopting behaviors that could otherwise be harmful to their health. Our review first addresses the general lack of consensus on the impact of specific lifestyle factors on breast cancer recurrence and the resulting equivocal lifestyle recommendations for survivors. Second, we describe inadequacies of the studies of survivors' lifestyle changes related to recurrence. Because much of the existing knowledge about modifiable risk factors for recurrence comes from studies of survivors whose participation and behavior change were potentially influenced by their concern about recurrence, we need large, population-based observational studies of randomly selected breast cancer survivors, adequately representing the target population. Critical are data on lifestyle change from prediagnosis to postdiagnosis and changes over time after diagnosis, extensive data on conventional and nonconventional treatments, and the temporal relationship between behaviors and treatments, and inclusion of the full complement of potential lifestyle risk factors for recurrence. Understanding in detail the current status of survivors' perceptions and behaviors related to modifiable risk factors for recurrence can provide considerable practical information to inform future interventions and communication strategies for breast cancer survivors.

Adolescent dietary phytoestrogen intake and breast cancer risk (Canada)

OBJECTIVE

It has been suggested that dietary phytoestrogen intake during adolescence may reduce the risk of developing breast cancer. This population-based case-control study evaluated the association between adolescent dietary phytoestrogen intake and adult breast cancer risk among women in Ontario, Canada.

METHODS

Pathology-confirmed, population-based breast cancer cases, aged 25-74 years, diagnosed between June 2002 and April 2003, were identified using the Ontario Cancer Registry. Population-based controls were recruited, and matched to cases within 5-year age groups. Adolescent phytoestrogen intake was obtained using a brief food frequency questionnaire (n = 3,024 cases, n = 3,420 controls). Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Higher phytoestrogen intake (both isoflavones and lignans) during adolescence was associated with a reduced breast cancer risk, and a monotonic trend was observed from the lowest to the highest quartile (OR [Q2] = 0.91, 95% CI 0.79-1.04, OR[Q3] = 0.86, 95% CI 0.75-0.98, and OR[Q4] = 0.71, 95% CI 0.62-0.82, p-trend < 0.001).

CONCLUSION

Adolescent dietary phytoestrogen intake may be associated with a decreased risk of adult breast cancer. If verified, this finding has important implications with regard to breast cancer prevention since diet is a potentially modifiable factor.

Estimated Asian adult soy protein and isoflavone intakes

There is substantial interest in the possible anticancer effects of soy foods. In part, this is because of the historically low incidence rates of breast and prostate cancer in Asia. Of the several putative soybean chemopreventive agents, isoflavones have received the most attention. Awareness of this research has led increasing numbers of consumers to use soy foods, isoflavone-fortified foods, and isoflavone supplements. Therefore, there is a need for guidance regarding appropriate isoflavone intake levels. To this end, this article analyzed soy protein (as a surrogate for isoflavones) and isoflavone intake of the major soy food-consuming countries using individual dietary surveys for the bulk of the information. In total, 24 surveys from 4 countries that met the inclusion criteria were identified: Japan (n = 11), China (n = 7), Hong Kong (n = 4), and Singapore (n = 2). The results indicate that older Japanese adults consume approximately 6-11 g of soy protein and 25-50 mg of isoflavones (expressed as aglycone equivalents) per day. Intake in Hong Kong and Singapore is lower than in Japan, whereas significant regional intake differences exist for China. Evidence suggests that < or =10% of the Asian population consumes as much as 25 g of soy protein or 100 mg of isoflavones per day. The applicability of these findings for making soy intake recommendations for non-Asians is discussed.

Review of the factors affecting bioavailability of soy isoflavones in humans

Soy isoflavones have anticarcinogenic, antioxidant, and antiatherosclerotic activities. They also interact with the estrogen receptor, which makes them weak or moderate phytoestrogens. Because of their bioactivity, isoflavone bioavailability has been extensively studied in humans. This review summarizes data from intervention studies in humans, focusing on the factors that affect bioavailability. Summarizing data from 16 studies shows that the maximum concentration in plasma normalized to a constant dose of genistin is approximately 1.6 times that of genistein, and daidzin is approximately 1.8-fold higher than daidzein, whereas the half-life is not significantly different for aglycone and glucoside. There is a wide variation in the reported percentage urinary excretion that is not dependent on dose. Bioavailability is increased by a rapid gut transit time and by low fecal digestion rates and is decreased by a fiber-rich diet. There is no difference in bioavailability between pre- and postmenopausal women. The daily ingestion of soymilk for 1 wk does not affect bioavailability, but daily ingestion for a month increases excretion of equol in women. The factors or habitual diet characteristics that influence equol production are not clear, but equol production is limited with an immature flora. There is no consensus on which source of isoflavones results in the highest isoflavone bioavailability, and published studies present different results, although bioavailability is affected by whether the dose is given as food or drink. In conclusion, it is important to consider the factors affecting bioavailability of isoflavones when designing intervention studies.

Soy and red clover for mid-life and aging

INTRODUCTION

Menopause is associated with mid-life, a time when many women begin to experience the signs and symptoms of aging, such as increases in blood pressure, changes in lipid profiles, loss of bone mass density, and diminished memory and cognition. Given the result of the Women's Health Initiative, many women no longer consider hormone therapy the first option for promoting healthy aging. Instead, they are turning to botanical and dietary supplement (BDS) products in place of hormone therapy. This paper reviews the evidence available for use of isoflavones from soy and red clover for the treatment or prevention of these health issues.

METHODS

The MEDLINE and EMBASE databases were searched for articles relating to soy or red clover supplement use for prevention and/or treatment of heart disease, hyperlipidemia, osteoporosis, mood disorders and cognitive abilities. Studies were included if they were randomized, controlled trials and included peri- or postmenopausal women.

RESULTS

Isoflavone products appear to be the most useful for improving lipid profiles; however, the evidence suggests that isoflavone extracts from soy are less effective than products containing soy protein or red clover isoflavones. Soy protein appears to reduce levels of total cholesterol and low density lipoprotein cholesterol, while red clover reduces levels of triglycerides and increases high density lipoprotein cholesterol. The data were somewhat less convincing, although promising, for increasing bone mass density and improving cognitive abilities.

CONCLUSIONS

Research suggests that isoflavones found in soy foods and red clover appear to have a small but positive health effect on plasma lipid concentrations, bone mass density, and cognitive abilities. Given the lack of serious safety concerns in the short term, it would appear that including soy and red clover in the diet of postmenopausal women, not withstanding a soy allergy, might be beneficial.

A delayed nonlinear PBPK model for genistein dosimetry in rats

Genistein is an endocrine-active compound (EAC) found in soy products. It has been linked to beneficial effects such as mammary tumor growth suppression and adverse endocrine-related effects such as reduced birth weight in rats and humans. In its conjugated form, genistein is excreted in the bile, which is a significant factor in its pharmacokinetics. Experimental data suggest that genistein induces a concentration-dependent suppression of biliary excretion. In this article, we describe a physiologically based pharmacokinetic (PBPK) model that focuses on biliary excretion with the goal of accurately simulating the observed suppression. The mathematical model is a system of nonlinear differential equations with state-dependent delay to describe biliary excretion. The model was analyzed to examine local existence and uniqueness of a solution to the equations. Furthermore, unknown parameters were estimated, and the mathematical model was compared against published experimental data.

Addressing the soy and breast cancer relationship: review, commentary, and workshop proceedings

The impact of soyfood intake on breast cancer risk has been investigated extensively. Much of this focus can be attributed to the soybean being a dietary source that is uniquely rich in isoflavones. The chemical structure of isoflavones is similar to that of estrogen, and isoflavones bind to both estrogen receptors (ER alpha and ER beta) (although they preferentially bind to and activate ER beta) and exert estrogen-like effects under some experimental conditions. Isoflavones also possess nonhormonal properties that are associated with the inhibition of cancer cell growth. Thus, there are several possible mechanisms by which soy may reduce the risk of breast cancer. However, the role of isoflavones in breast cancer has become controversial because, in contrast to the possible beneficial effects, some data from in vitro and animal studies suggest that isoflavones, especially genistein, the aglycone of the main soybean isoflavone genistin, may stimulate the growth of estrogen-sensitive tumors. Limited human data directly address the tumor-promoting effects of isoflavones and soy. Because the use of soyfoods and isoflavone supplements is increasing, it is important from a public health perspective to understand the impact of these products on breast cancer risk in women at high risk of the disease and on the survival of breast cancer patients. To this end, a workshop was held in November 2005 to review the existing literature and to make research recommendations. This paper summarizes the workshop findings and recommendations. The primary research recommendation is that the impact of isoflavones on breast tissue needs to be evaluated at the cellular level in women at high risk for breast cancer.

Dietary genistein intake and cognitive performance in a multiethnic cohort of midlife women

OBJECTIVE

To examine the relationship between food frequency questionnaire estimated isoflavone intakes and cognitive performance.

DESIGN

The Study of Women's Health Across the Nation (SWAN), is a multiethnic, community based, longitudinal study of women aged 42 to 52 years at entry. Dietary isoflavone intakes were estimated from an interviewer-administered food frequency questionnaire at baseline. Intakes of genistein and daidzein were highly correlated (r = 0.98); therefore, analyses were conducted using genistein only. The SWAN includes white, African American, Hispanic, Chinese, and Japanese women; this analysis was performed only in the latter two ethnic groups because the others had minimal genistein intake (median, <4 microg/day). Cognitive function tests were measured at the fourth annual follow-up visit using the East Boston Memory Test (Immediate and Delayed), Symbol Digit Modalities Test, and Digit Span Backward Test. Ethnicity-specific general linear models were used to examine the relationship between each of these cognitive tests and energy-adjusted genistein intake controlling for age, menopause stage, ever-use of any hormones, and current use of any hormones.

RESULTS

Among 195 Japanese and women and 185 Chinese women, median intakes of genistein (mug/day) were 6,788 and 3,534, respectively. No associations between genistein intake and measures of cognitive performance were found in either ethnic group.

CONCLUSIONS

Our results did not support the hypothesis that genistein intake, at the levels consumed by the study sample, benefits cognitive performance. It also possible that the bioavailability of genistein in food sources is insufficient to exert a neurophysiological effect or that the potential effect of genistein is only manifest in low-estrogen states; the current study is not able to address these possibilities.

Lowering effect of an isoflavone-rich fermented soybean extract on the serum cholesterol concentrations in female rats, with or without ovariectomy, but not in male rats

We examined the effect of administering an isoflavone-rich fermented soybean extract (FSBE) on the serum cholesterol concentrations in male rats and in intact and ovariectomized (OVX) female rats. Dietary FSBE decreased the serum cholesterol concentrations in intact female and OVX rats, but did not affect the concentrations in male rats. Dietary FSBE increased the hepatic total and esterified cholesterol contents in the intact female rats, but decreased them in the OVX rats. This hypocholesterolemic effect was not a simple estrogenic effect because it has appeared in some reports that estrogen administration decreased serum cholesterol both male and female rats. Dietary FSBE increased the hepatic low-density lipoprotein receptor (LDLR) gene expression in the intact female rats as has previously been reported from many studies, but did not affect that of the OVX rats. Further investigation is needed into the hypocholesterolemic mechanism of FSBE.

Genistein alone and in combination with the mammalian lignans enterolactone and enterodiol induce estrogenic effects on bone and uterus in a postmenopausal breast cancer mouse model

The use of phytoestrogens, such as isoflavones and lignans, for treatment of postmenopausal breast cancer is increasing, but their effects on bone and other major organs are not clear. While the isoflavone genistein (GEN) has been shown to prevent or slow the loss of bone mineral density (BMD), the effect of lignans enterodiol (END) and enterolactone (ENL) are unknown. In this study, we determined in ovariectomized mice with human MCF-7 breast tumor xenografts the effects of the lignans, and GEN, alone and in combination, on bone and uterus. Mice with established MCF-7 tumors were fed a basal diet (AIN-93G), divided into 5 groups, and given daily subcutaneous injections (10 mg/kg body weight) of either ENL, END, GEN, a mixture of these compounds (MIX), or vehicle as a negative control for 22 weeks. Results showed that GEN acts estrogenically in both the uterus and bone by increasing the uterus weight, femur BMD, and femur biomechanical strength (yield load), while the lignans do not. However, treatment with MIX induced minimal effects on femur biomechanical strength parameters but significantly increased uterus weight. A significant positive correlation was observed between MCF-7 tumor volume and femur BMD and biomechanical strength parameters (femur peak load and yield load) but not with uterus weight, suggesting that the uterus may respond differently to phytoestrogens compared to MCF-7 tumors and bone. It is concluded that GEN induces beneficial effects on bone but has adverse effects on tumors and uterus in this model of postmenopausal breast cancer. The lignans do not exert adverse effects on any tissue, however, when combined with GEN, they exert an adverse effect on the uterus.

Phase III Double-Blind, Randomized, Placebo-Controlled Crossover Trial of Black Cohosh in the Management of Hot Flashes: NCCTG Trial N01CC1

Purpose

Hot flashes can cause significant morbidity in postmenopausal women undergoing or finished with breast cancer treatment. Black cohosh has been used to treat hot flashes, but definitive clinical data about efficacy have been equivocal.

Methods

A double-blind, randomized, cross-over clinical trial with two 4-week periods, was used to study the efficacy of black cohosh (1 capsule, Cimicifuga racemosa 20 mg BID) for the treatment of hot flashes in women. Participants kept a daily hot flash diary during a baseline week and then during two 4-week crossover treatment periods. Hot flash scores were measured by assigning points (1 to 4 for mild to very severe) to each hot flash based on severity and then adding the points for a given time period.

Results

Between October 31, 2003, to March 4, 2004, 132 patients were randomly assigned. Toxicity was minimal and not different by treatment group. Patients receiving black cohosh reported a mean decrease in hot flash score of 20% (comparing the fourth treatment week to the baseline week) compared with a 27% decrease for patients on placebo (P = .53). Mean hot flash frequency was reduced 17% on black cohosh and 26% on placebo (P = .36). Patient treatment preferences were measured after completion of both treatment periods by ascertaining which treatment period, if any, the patient preferred. Thirty-four percent of patients preferred the black cohosh treatment, 38% preferred the placebo, and 28% did not prefer either treatment.

Conclusion

This trial failed to provide any evidence that black cohosh reduced hot flashes more than the placebo.

Protective effects of soybean isoflavone against gamma-irradiation induced damages in mice

In the present work, we investigated the radioprotective efficacy of soybean isoflavone (SI) in mitigating gamma-irradiation-induced oxidative damage to the livers and blood systems of adult Swiss albino mice. We administered various doses of SI (50 mg/kg b.wt, 100 mg/kg b.wt, and 400 mg/kg b.wt) to the mice for seven consecutive days before exposing them to a single dose of 4.56 Gy 60Co-gamma whole-body irradiation. The irradiated mice continued to receive SI for two or seven days before sacrifice. The SI treatments significantly elevated liver catalase (CAT) and glutathione peroxidase (GPx) enzyme activities and mRNA abundances, and decreased the malonaldehyde (MDA) levels. The SI treatments also accelerated the recovery of circulating white blood cells (WBCs) and reticulocytes (RETs) seven days following irradiation. These effects were dose-dependent, and the strongest effect on most biomarkers (but not on histopathology) was seen with an intermediate dose. Our results provide useful information for future investigations, and strongly implicate a clinical application for SI.

Infertility, ovulation induction treatments and the incidence of breast cancer--a historical prospective cohort of Israeli women

CONTEXT

Ovulation induction drugs may be associated with increased breast cancer risk. Results so far have been inconclusive.

OBJECTIVE

To evaluate the association between infertility, exposure to ovulation induction drugs and the incidence of breast cancer.

DESIGN

Historical prospective cohort and nested case-control study.

SETTING

Institutional practice

PATIENTS

About 5,788 women attending five infertility centers in Israel between 1964 and 1984.

INTENTION

Abstracting of medical records and telephone interviews.

MAIN OUTCOME MEASURE

Breast cancer incidence was determined through linkage with the National Cancer Registry database. Standardized incidence ratios (SIRs) and 95% confidence intervals were computed by comparing the observed to the expected cancer rates in the general population. In addition, a nested case-control study within the cohort was performed with interviews of breast cancer cases and two matched controls.

RESULTS

The study cohort included 120,895 women years of follow-up. Compared to 115.2 expected breast cancer cases, 131 cases were observed (SIR = 1.1; 95% CI 0.9-1.4). Risk for breast cancer was significantly higher for women treated with clomiphene citrate (SIR = 1.4; 95% CI 1.0-1.8). Similar results were noted when comparisons were carried out between treated and untreated women, and when multivariate models were applied. In the nested case-control study, higher cycle index (OR = 2.2; 95% CI 1.0-4.8) and treatment with clomiphene citrate (OR=2.7; 95% CI 1.3-5.7) were associated with higher risk for breast cancer.

CONCLUSION

Infertility and usage of infertility drugs in general are not associated with increased risk for breast cancer. However, for infertile women treated with clomiphene citrate, breast cancer risk is elevated.

The soybean isoflavone genistein induces differentiation of MG63 human osteosarcoma osteoblasts

A soybean-rich diet was shown to reduce the incidence of osteoporosis in Eastern countries; its effect on bone metabolism was ascribed to the action of the soybean isoflavones such as genistein. Although many studies have shown isoflavone-induced osteoblast differentiation, its preventative action on bone mass loss has not been clarified. Here, the osteogenetic effects of genistein on human cell line MG63 osteoblasts were elucidated using a variety of approaches. In particular, phalloidin-rhodamine staining revealed that genistein-treated osteoblasts possessed a more organized cytoskeleton, and genistein's inhibitory effect upon cell proliferation was associated with exposure of phosphatidylserines on the external plasmalemma surface. Although this phosphatidylserine exposure is considered a typical apoptotic marker, scanning and transmission electron microscopy revealed that genistein-treated osteoblasts released matrix vesicles and showed no evidence of chromatin condensation. Assays, stainings, and scanning electron microscopy showed that genistein-treated osteoblasts synthesized relatively high levels of collagen and alkaline phosphatase and, even in a nonosteogenic growth medium, formed mineralized bone noduli. A clear pattern of genistein-induced osteoblast activation therefore emerges, in which all of the essential components required for the rapid production of mineralized bone extracellular matrix are stimulated by this soybean isoflavone.

Meta-Analysis of Soy Intake and Breast Cancer Risk

BACKGROUND

High intake of soy foods has been proposed to contribute to the low breast cancer risk in Asian countries. However, results of epidemiologic studies of this association are highly variable, and experimental data suggest that soy constituents can be estrogenic and potentially risk enhancing. Thus, rigorous evaluation of available epidemiologic data is necessary before appropriate recommendations can be made, especially for women at high risk of breast cancer or those who have survived the disease.

METHODS

We performed a meta-analysis of 18 epidemiologic studies (12 case-control and six cohort or nested case-control) published from 1978 through 2004 that examined soy exposure and breast cancer risk. Pooled relative risk estimates were based on either the original soy exposure measure defined in each study or on an estimate of daily soy protein intake.

RESULTS

Risk estimates, levels and measures of soy exposure, and control for confounding factors varied considerably across studies. In a pooled analysis, among all women, high soy intake was modestly associated with reduced breast cancer risk (odds ratio [OR] = 0.86, 95% confidence interval [CI] = 0.75 to 0.99); the association was not statistically significant among women in Asian countries (OR = 0.89, 95% CI = 0.71 to 1.12). Among the 10 studies that stratified by menopausal status the inverse association between soy exposure and breast cancer risk was somewhat stronger in premenopausal women (OR = 0.70, 95% CI = 0.58 to 0.85) than in postmenopausal women (OR = 0.77, 95% CI = 0.60 to 0.98); however, eight studies did not provide menopause-specific results, six of which did not support an association. When exposure was analyzed by soy protein intake in grams per day, a statistically significant association with breast cancer risk was seen only among premenopausal women (OR = 0.94, 95% CI = 0.92 to 0.97).

CONCLUSIONS

Soy intake may be associated with a small reduction in breast cancer risk. However, this result should be interpreted with caution due to potential exposure misclassification, confounding, and lack of a dose response. Given these caveats and results of some experimental studies that suggest adverse effects from soy constituents, recommendations for high-dose isoflavone supplementation to prevent breast cancer or prevent its recurrence are premature.

Soy isoflavones and bone health: a double-edged sword?

Numerous publications and research studies on isoflavones have prompted a nationwide increase in the consumption of soy-based foods and supplements in the United States. Isoflavones are natural endocrine active compounds generally considered to promote health and prevent or slow the onset of certain chronic diseases such as osteoporosis. The beneficial effects of soy isoflavones on bone may, however, be life-stage specific and dependent on the estrogen receptor number and endogenous hormone milieu. Perimenopausal and early menopausal women may therefore be more receptive to the therapeutic effects of isoflavones on bone loss prior to the diminution of estrogen receptors that occurs in the postmenopausal years, whereas laboratory studies in developmental age range animals have demonstrated the potential for adverse effects following exposure to high levels of soy isoflavones. Clinical studies in developing humans that either support or refute findings in animal studies are lacking. The effects of chronic consumption of high levels of soy isoflavones at each life stage to assess risk-benefit ratios should be a high priority of research.

Stage matters: choosing relevant model systems to address hypotheses in diet and cancer chemoprevention research

Clinical evidence reveals that the efficacy of dietary factors to prevent cancer is probably stage-dependent. The ability to demonstrate stage-specific effects of dietary compounds on normal, preneoplastic and malignant cell models may provide insights into puzzling clinical results from cancer chemoprevention trials. The relevance of these models to the field of cancer prevention is immense and will undoubtedly facilitate the ability to discover which dietary factors are most effective at preventing cancer and which, if any, specific steps in neoplastic transformation render cells refractory to the effects of dietary compounds. There are illustrative examples where exposure of high-risk individuals to dietary chemopreventive agents increases rather than decreases cancer risk. While geneticists and clinical oncologists acknowledge the morphological continuum along which tumors develop in specific tissues, tumor cells, rather than normal and preneoplastic cells, continue to be the primary in vitro reductionist tool employed to elucidate mechanisms underlying disease progression and to investigate the potential utility of dietary as well as other chemopreventive agents. Currently, there are few relevant model systems to study the progression of neoplastic transformation, especially in epithelial cells. We highlight examples of model systems isolated from prostate, breast, endometrial and intestinal tissue, with special emphasis on a specific set of non-tumorigenic, conditionally immortal cell lines derived from C57/BL6 mice [YAMC (Young Adult Mouse Colon cells; Apc+/+) cells and IMCE (Immorto-Min Colonic Epithelium cells; ApcMin/+) cells] that have yielded important information on early events in colorectal neoplasia development. These cell lines are an illustrative example of how researchers can examine stage-dependent effects of specific dietary components on carcinogenesis. The utilization of cell culture systems modeling early, middle and late stages of tumorigenesis will yield important insights into mechanisms by which dietary components impact cancer progression.

Lack of stimulatory activity of a phytoestrogen-containing soy extract on the growth of breast cancer tumors in mice

The present study was designed to investigate the effects of a phytoestrogens-containing soy extract (SOYSELECT, SSE) on the growth of estrogen-dependent (MCF-7) and estrogen-unresponsive (MDA-MB-231) human breast cancer xenografts in athymic mice. Results obtained provided evidence that MCF-7 tumors did not grow over the treatment period (5 weeks) in ovariectomized females receiving 50 or 100 mg/kg/day SSE (oral route); administration of SSE also did not affect the estradiol-sustained growth of MCF-7 tumors in mice. Similarly, no effects on tumor growth were observed in SSE-treated mice bearing MDA-MB-231 xenografts. Data from pS2, progesterone receptor and cyclin D1 mRNA expression in tumors showed that, although SSE was able to induce a moderate estrogenic effect in MCF-7 cells, it did not increase cellular proliferation and tumor growth, in our experimental conditions. Besides, when used in association with 17beta-estradiol, it displayed antiestrogenic activity. The expression of other genes involved in tumor progression and angiogenesis, such as Thrombospondin 1, Transforming Growth Factor beta2 and Kallikrein 6 was also evaluated in tumor samples, results showing a decrease in mRNA expression upon SSE treatment. The effect of SSE on angiogenesis in vivo was also evaluated in the Matrigel plug assay; results obtained showed a striking anti-angiogenic activity in mice receiving 100 mg/kg/day SSE, thereby confirming that this extract may interfere with angiogenesis. Collectively, these experimental data suggest that SSE could be not harmful for women with a history of or at high risk for breast cancer, at least for short treatment periods; however, further studies are needed to thoroughly characterize the activity profile of the extract in this specific setting of patients.

Estradiol and phytoestrogens differently influence the rodent postmenopausal mammary gland

OBJECTIVE

In the following study, we investigated treatment-related changes in mammary gland histomorphology and structure after the administration of soy to adult virgin ovariectomized (OVX) female rats. Additionally, mammary receptor regulation was extensively evaluated by immunohistochemical analysis, and tissue proliferative activity analyzed by cell nuclear proliferating antigen expression (Ki67).

DESIGN

OVX rats were treated, for 6 weeks, with either the vehicle, the soy extract (SSE 100 mg/kg/d PO), or 17beta-estradiol (0.5 mg/kg/d PO); a sham control group (SHAM) was also included in the study. When killed, mammary glands were collected and subsequently processed for light microscopy or immunohistochemistry. Immunoreactivity was quantified by a scoring system that took into account both the percentage of positive cells and the intensity of the staining.

RESULTS

The 17beta-estradiol--treated rats had stimulated mammary glands compared with OVX rats, with an average lobulo-alveolar development not different from the SHAM controls. Only a partial regression of the glandular atrophy was observed in OVX rats receiving 100 mg/kg/d SSE, with a histological appearance between that of the OVX and SHAM controls. No significant changes were observed among experimental groups in the median ERalpha scores of the epithelial compartment (score of 3 in all groups); in the stromal compartment, a tendency toward decreased expression was seen with 17beta-estradiol rats compared with OVX controls (scores of 2 and 5, respectively). A significant reduction in ERbeta immunostaining was observed in the mammary glands of SSE-treated rats, in both epithelium and stroma (scores of 4 and 3, respectively), compared with those of OVX controls (score of 8 in both compartments). The ERbeta receptor status was not significantly affected by 17beta-estradiol. Compared with OVX rats (score of 1), PR expression was up-regulated by 17beta-estradiol (score of 6), whereas an ovariectomy-like pattern was observed after the administration of SSE (score of 0). Ki67 immunoreactivity in the epithelium and stroma was increased by the administration of 17beta-estradiol (scores of 4 and 5, respectively) and was unchanged after SSE treatment (scores of 0 and 2, respectively), compared with OVX controls (scores of 1 and 2, respectively).

CONCLUSIONS

The differences observed in the histological pattern, hormonal receptor status regulation, and Ki67 modulation suggest a different role for phytoestrogens and 17beta-estradiol in postmenopausal rodent mammary glands.

Exploiting our knowledge of NF-kappaB signaling for the treatment of mammary cancer

Nuclear Factor-kappaB (NF-kappaB) has been implicated in the lobuloalveolar development of the mammary gland. In breast cancer its activation has been linked to tumor progression via stimulation of cell proliferation, pro-survival, and angiogenesis pathways and metastasis. Whether NF-kappaB activation in the immune system influences mammary cancer remains unclear. In addition to the constitutive activation frequently found in mammary carcinoma tissue, radio- and chemotherapeutic agents used in the treatment of mammary cancer can lead to activation of NF-kappaB. This effect has been postulated to contribute to the development of resistance to these agents and suggests the use of NF-kappaB inhibitors as sensitizers for therapy. The review describes principle targets and drugs used to inhibit NF-kappaB function and discusses future perspectives in the use of these inhibitors for the treatment of mammary cancer.

Reported attitudes and beliefs toward soy food consumption of soy consumers versus nonconsumers in natural foods or mainstream grocery stores

OBJECTIVE

To examine the attitudes and beliefs of soy foods consumers (SCs) versus nonconsumers (NCs).

DESIGN

Seven focus groups were conducted.

SETTING

Mainstream or natural foods grocery stores.

PARTICIPANTS

Fifty-three participants, ages 18 to 91 years.

VARIABLES MEASURED

Focus groups included discussions on lifestyle practices, beliefs about soy, conversion to soy consumption, and suggestions on how to increase soy consumption.

ANALYSIS

Common themes were identified, coded, and compared using NVivo computer software.

RESULTS

Barriers to soy consumption included soy's image, a lack of familiarity with how to prepare soy foods, and a perception that soy foods were an inadequate flavor substitute for animal-based products. SCs' conversion to regular consumption was initiated by food intolerances, an increased interest in health, or an adoption of a vegetarian or natural foods lifestyle and was sustained because they enjoyed the flavor. Many participants did not know why soy was considered healthful, whereas others identified it as "heart healthy," a source of protein, and good for women's health. Some SCs had become concerned regarding the controversy surrounding breast cancer and soy consumption.

CONCLUSIONS AND IMPLICATIONS

Improving soy's image and educating consumers on its preparation could increase soy consumption.

Genistein, EGCG, and capsaicin inhibit adipocyte differentiation process via activating AMP-activated protein kinase

Phytochemicals such as soy isoflavone genistein have been reported to possess therapeutic effects for obesity, diabetes, and cardiovascular diseases. In the present study, the molecular basis of selective phytochemicals with emphasis on their ability to control intracellular signaling cascades of AMP-activated kinase (AMPK) responsible for the inhibition of adipogenesis was investigated. Recently, the evolutionarily conserved serine/threonine kinase, AMPK, emerges as a possible target molecule of anti-obesity. Hypothalamic AMPK was found to integrate nutritional and hormonal signals modulating feeding behavior and energy expenditure. We have investigated the effects of genistein, EGCG, and capsaicin on adipocyte differentiation in relation to AMPK activation in 3T3-L1 cells. Genistein (20-200muM) significantly inhibited the process of adipocyte differentiation and led to apoptosis of mature adipocytes. Genistein, EGCG, and capsaicin stimulated the intracellular ROS release, which activated AMPK rapidly. We suggest that AMPK is a novel and critical component of both inhibition of adipocyte differentiation and apoptosis of mature adipocytes by genistein or EGCG or capsaicin further implying AMPK as a prime target of obesity control.

Contents and bioactivities of lunasin, bowman-birk inhibitor, and isoflavones in soybean seed

It has been previously demonstrated that lunasin is a novel and promising cancer preventive peptide from soybean. The Bowman-Birk protease inhibitor (BBI) and isoflavones are well-studied substances from soy. This study evaluated the levels and bioactivities of these three compounds as affected by stages of seed development and sprouting under light and dark conditions. BBI and lunasin appear at 7 and 6 weeks, respectively, after flowering and increase as the seed matures. Daidzein and genistein both decrease during seed maturation. During sprouting under light, BBI increases up to the 6th day and decreases thereafter, disappearing at the 9th day after soaking. Under dark conditions, BBI increases up to the 7th day after soaking and decreases thereafter, disappearing at the 10th day. Lunasin starts to decrease at 2 days after soaking and disappears completely at 7 days under light and dark conditions. Daidzein and genistein increase continuously during the 10 days of soaking, and both increase more in the dark than under light conditions. Protein extracts from early seed development (2-5 weeks after flowering) suppress cell viability to a greater degree than those from later stages (6-9 weeks). Inhibition of foci formation by protein extracts from later stages is greater than those from earlier stages. Lunasin and BBI suppress foci formation more than the isoflavones. Sprouting decreases lunasin and BBI contents but increases isoflavones. Protein extracts from early soaking times inhibit foci formation more and suppress cell viability less than those from later soaking times. Light and dark conditions have no influence on the bioactivities of protein extracts. These data are useful in the preparation of soy fractions enriched in lunasin, BBI, and isoflavones and in making dietary recommendations.

Fermented soy product supplemented with isoflavones affected fat depots in juvenile rats

OBJECTIVES

This study investigated the effects of soy product fermented by Enterococcus faecium and Lactobacillus jugurti supplemented with isoflavones on adipose tissue, blood lipid, and glucose levels on juvenile rats.

METHODS

Rats were fed a cholesterol-enriched diet for 3 wk as a preliminary treatment to create hypercholesterolemia. They were then fed a chow diet (HC), a chow diet plus fermented soy product supplemented with isoflavones (HCFI), a chow diet plus placebo (HCP), or a chow diet plus placebo supplemented with isoflavones (HCPI), respectively, for an additional 3 wk.

RESULTS

The beneficial effects of fermented soy product supplemented with isoflavones on epididymal (EPI) and retroperitoneal (RET) fat pads was likely due to isoflavones because adipocyte circumference (micrometers) in the HC group was significantly larger (EPI: 105.66 +/- 13.36; RET: 134.95 +/- 25.40) than that in the HCFI group (EPI: 93.17 +/- 12.80; RET: 108.62 +/- 15.50) and HCPI group (EPI: 93.06 +/- 15.10; RET: 112.34 +/- 18.21). The probiotic micro-organism accentuated the antilipogenic effect of isoflavones on RET (HCFI: 108.62 +/- 15.50 micrometers versus HCPI: 112.34 +/- 18.21 micrometers). Moreover, the fermented product increased glucose concentration similar to that in the chow group but did not change blood lipids.

CONCLUSION

This product may offer new approaches to obesity prevention.

The meaning of food to breast cancer survivors

Although a definitive relationship between diet and breast cancer remains controversial, many women adopt dietary change after diagnosis. To understand factors motivating dietary change, we explored the meanings that breast cancer survivors attached to food during recovery. Six women who were breast cancer survivors for six to 19 years participated in semi-structured interviews exploring personal meanings attached to food, dietary changes after diagnosis, factors influencing dietary change, and experiences with food in relation to breast cancer. Two distinct phases emerged. These corresponded to active treatment, when women used food to gain control, to cope, for comfort, and for hope, and to post-treatment, when the meanings that women attached to food were shaped by the perception of food's role in breast cancer causation. Women who believed that diet prevents a first diagnosis adopted change to prevent recurrence, while those who did not believe in the relationship between diet and breast cancer adopted change to improve health. In women with breast cancer, food can be an important coping mechanism. Women may benefit from counselling grounded in the meanings they attach to food over the recovery continuum.

Soybean Foods and Their Benefits: Potential Mechanisms of Action

Isoflavones have been proposed to be the active component responsible for the beneficial effects of soybean foods, and appear to work in conjunction with the proteins to protect against cancer, cardiovascular disease, and osteoporosis. Most of the research activities on the benefits of soybean foods have focused on the role these isoflavones play in disease prevention or treatment; however, there is also some evidence that the benefits are attributable to certain peptides or protein fractions from soybeans. This review will focus on some of the potential mechanisms whereby soybeans exert their protective effects against heart disease, cancer, and osteoporosis.

Combination of 5-fluorouracil and genistein induces apoptosis synergistically in chemo-resistant cancer cells through the modulation of AMPK and COX-2 signaling pathways

5-Fluorouracil (5-FU) is one of the widely used chemotherapeutic drugs targeting various cancers, but its chemo-resistance remains as a major obstacle in clinical settings. In the present study, HT-29 colon cancer cells were markedly sensitized to apoptosis by both 5-FU and genistein compared to the 5-FU treatment alone. There is an emerging evidence that genistein, soy-derived phytoestrogen, may have potential as a chemotherapeutic agent capable of inducing apoptosis or suppressing tumor promoting proteins such as cyclooxygenase-2 (COX-2). However, the precise mechanism of cellular cytotoxicity of genistein is not known. The present study focused on the correlation of AMPK and COX-2 in combined cytotoxicity of 5-FU and genistein, since AMPK is known as a primary cellular homeostasis regulator and a possible target molecule of cancer treatment, and COX-2 as cell proliferation and anti-apoptotic molecule. Our results demonstrated that the combination of 5-FU and genistein abolished the up-regulated state of COX-2 and prostaglandin secretion caused by 5-FU treatment in HT-29 colon cancer cells. These appear to be followed by the specific activation of AMPK and the up-regulation of p53, p21, and Bax by genistein. Under same conditions, the induction of Glut-1 by 5-FU was diminished by the combination treatment with 5-FU and genistein. Furthermore, the reactive oxygen species (ROS) was found as an upstream signal for AMPK activation by genistein. These results suggested that the combination of 5-FU and genistein exert a novel chemotherapeutic effect in colon cancers, and AMPK may be a novel regulatory molecule of COX-2 expression, further implying its involvement in cytotoxicity caused by genistein.

A randomised double-blind controlled trial of oral soy supplements versus placebo for treatment of menopausal symptoms in patients with early breast cancer

Menopausal symptoms are a major survivorship issue for patients treated for breast cancer. There are increasing concerns over the use of hormone replacement therapy (HRT) in this setting and a growing consumer interest in "natural" therapies. It had been suggested that soy phyto-oestrogens might be beneficial in the treatment of menopausal symptoms. Seventy-two patients with a histologically confirmed pre-existing diagnosis of breast cancer who were having menopausal symptoms were randomised between 12 weeks of treatment with soy capsules or placebo. Quality of life and menopausal symptom scores were assessed at baseline, 4, 8 and 12 weeks. There was no statistical difference in menopausal symptom scores or quality of life between the two arms of the study.

Isoflavones and postmenopausal women: a critical review

Isoflavonic phytoestrogens, or isoflavones, constitute a class of phytoestrogens that have properties similar to selective estrogen receptor modulators, and have attracted a substantial degree of attention in recent years, particularly as a possible alternative to the conventional hormone replacement therapy regimens used by postmenopausal women. Despite great promise, it is difficult to make many specific recommendations about their use at the current time, in light of the many outstanding questions that hopefully will be answered in the future by focused interventional studies involving humans. Studies to date indicate that the use of isoflavones to address vasomotor symptoms provides at most small benefits beyond a placebo effect, and no benefit for genital atrophy. As for postmenopausal women whose primary concern is cardiovascular disease, the recommendation of the American Heart Association to include soy protein foods as part of an otherwise healthy diet is well justified, and similarly the substitution of supplements containing soy protein for animal protein can also be recommended. The use of purified isoflavone supplements not containing soy protein may have some cardiovascular benefits, but these appear to be less substantial in degree than those provided by soy protein with isoflavones. In particular, more research is needed to assess the effects of isoflavones on osteoporosis, for which no recommendation regarding isoflavones can be made based on the current data. Also, isoflavones should not be taken by postmenopausal women for the specific purpose of decreasing their risk of breast or endometrial cancer, although, at least for those without pre-existing disease or at high risk, it seems quite unlikely that isoflavone use is harmful in this regard.

Potential beneficial metabolic interactions between tamoxifen and isoflavones via cytochrome P450-mediated pathways in female rat liver microsomes

PURPOSE

This study aims to evaluate a cytochrome P450-based tamoxifen-isoflavone interaction and to determine the mechanisms responsible for inhibitory effects of isoflavones (e.g., genistein) on the formation of alpha-hydroxytamoxifen.

METHODS

Metabolism studies were performed in vitro using female rat liver microsomes. The effects of genistein and an isoflavone mixture on tamoxifen metabolism and the inhibition mechanism were determined using standard kinetic analysis, preincubation, and selective chemical inhibitors of P450.

RESULTS

Metabolism of tamoxifen was saturable with Km values of 4.9+/-0.6, 14.6+/-2.2, 25+/-5.9 microM and Vmax values of 34.7+/-1.4, 297.5+/-19.2, 1867+/-231 pmol min(-1) mg(-1) for a-hydroxylation, N-desmethylation, and N-oxidation, respectively. Genistein (25 microM) inhibited alpha-hydroxylation at 2.5 microM tamoxifen by 64% (p < 0.001) but did not affect the 4-hydroxylation, N-desmethylation, and N-oxidation. A combination of three (genistein, daidzein, and glycitein) to five isoflavones (plus biochanin A and formononetin) inhibited tamoxifen alpha-hydroxylation to a greater extent but did not decrease the formation of identified metabolites. The inhibition on alpha-hydroxylation by genistein was mixed-typed with a Ki, value of 10.6 microM. Studies using selective chemical inhibitors showed that tamoxifen alpha-hydroxylation was mainly mediated by rat CYP1A2 and CYP3A1/2 and that genistein 3'-hydroxylation was mainly mediated by rat CYP1A2, CYP2C6 and CYP2D1.

CONCLUSIONS

Genistein and its isoflavone analogs have the potential to decrease side effects of tamoxifen through metabolic interactions that inhibit the formation of a-hydroxytamoxifen via inhibition of CYP1A2.

Dietary Genistein Reduces Metastasis in a Postsurgical Orthotopic Breast Cancer Model

Metastatic spread, not primary tumor burden, is the leading cause of breast cancer deaths. For patient prognosis to improve, new systemic adjuvant therapies that are capable of effectively inhibiting the outgrowth of seeded tumor cells after surgical treatment of the primary breast tumor are needed. To facilitate the preclinical development of such therapies, relevant animal models of breast cancer metastasis that can mimic the postsurgical adjuvant setting are required. Here we developed a preclinical xenograft model of breast cancer metastasis where the primary tumor was removed by surgical resection before systemic adjuvant treatment. We used this model to assess the antimetastatic effect of postsurgical dietary intervention with the soy isoflavone genistein. The anticancer activity of genistein has been established in vitro and in vivo, however, few studies have tested the potential of genistein as an antimetastatic therapy. Using our model, we tested the efficacy of adjuvant treatment with genistein to inhibit the outgrowth of metastases postsurgery. To establish primary tumors, human breast carcinoma cells, MDA-MB-435/HAL, were implanted into the mammary fat pad of female nude mice. Primary tumors were left to grow for 5 weeks before being surgically removed. Mice were then randomized into two diet groups: control soy-free diet versus genistein-supplemented diet. Five weeks later, metastatic burden was assessed. Genistein reduced the percent metastatic burden in the lungs by 10-fold. These results indicate that dietary intervention following cancer surgery can affect the outgrowth of seeded tumor cells. The availability of well-characterized, clinically relevant animal models for studying factors that regulate metastatic outgrowth postsurgery will provide an important tool for developing new systemic adjuvant therapies.