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

Antiproliferative and cytostatic effects of the natural product eupatorin on MDA-MB-468 human breast cancer cells due to CYP1-mediated metabolism

Introduction

The natural product eupatorin has been reported to have antiproliferative activity in tumour cell lines, but the exact mechanism is unclear. The cytochromes P450 CYP1B1, CYP1A1, and CYP1A2 have been shown to participate in the activation of various xenobiotics, compounds derived from the diet as well as chemotherapeutic drugs. CYP1B1 and CYP1A1 have also been proposed as targets for cancer chemotherapy for their differential and selective overexpression in tumour cells. In this study, we aimed to identify a possible mechanism of action for the antiproliferative effect of eupatorin, which can be attributed to CYP1 family-mediated metabolism.

Methods

The study focuses on the antiproliferative action of eupatorin on the human breast carcinoma cell line MDA-MB-468 and on a cell line derived from normal mammary tissue, MCF-10A. The cytotoxicity of the flavone, its effect on the cell cycle of the abovementioned cell lines, and its metabolism by CYP1 family enzymes were examined.

Results

Eupatorin showed a dose-dependent inhibitory effect of cell growth on MDA-MB-468 cells with a submicromolar median inhibition concentration (IC₅₀) whereas the IC₅₀ of this compound in MCF-10A cells was considerably higher. The antiproliferative effect, as measured by EROD (ethoxyresorufin-O-deethylase) assay and Western immunoblotting, was attributed mainly to CYP1A1 expression in MDA-MB-468 cells but not in MCF-10A cells. Moreover, CYP1 family enzymes were shown to metabolise eupatorin in vitro to the flavone cirsiliol and two other unidentified metabolites. Metabolism of eupatorin was also detected in MDA-MB-468 cell cultures, whereas metabolism by MCF-10A cells was negligible. Eupatorin was further shown to arrest the cell cycle of the CYP1-expressing cell line MDA-MB-468 in G₂/M phase, whereas no effect was observed in MCF-10A cells, which do not express CYP1 enzymes. The effect of eupatorin on the MDA-MB-468 cell cycle could be reversed by co-application of the CYP1 inhibitor acacetin.

Conclusion

The flavone eupatorin is selectively activated in breast cancer cells, but not in normal breast cells, due to CYP1 family metabolism. This provides a basis for selectivity which is desired against breast tumour cells. In this sense, eupatorin is shown by this study to be a very promising chemopreventative candidate that should be examined further in an in vivo study.

Increased expression of catalase in human hepatoma cells by the soy isoflavone, daidzein

The reduced incidence of cancer that has been observed in Asian population traditionally consuming soy-based food has been linked to the antioxidant potential of soy isoflavones, in particular daidzein and genistein. The present study was undertaken in order to test the antioxidative potential of daidzein and to examine the effect of daidzein treatment on the expression of the antioxidant enzyme catalase in the human hepatoma cell lines Huh-7 and HepG2. Daidzein itself did not display radical scavenging activity but it significantly increased the activity of the antioxidant enzyme catalase. Huh-7 cells were much more susceptible to daidzein cytotoxicity than HepG2 cells and showed much lower basal activity in luciferase reporter gene assays with the 3.2 kb fragment of the human catalase promoter. However, treatment with daidzein at a non-toxic concentration resulted in a similar induction of promoter activity in both cell lines. Reporter gene studies with different promoter constructs in HepG2 cells restrict the potential localization of the main regulatory elements for basal and inducible activity of the catalase promoter to a region approximately 120 bp to 300 bp upstream of the start codon of the catalase gene. From our results, we conclude that in human hepatoma cells daidzein at a non-toxic concentration increases the activity of human catalase and induces the transcription of the catalase gene via interaction with the proximal part of the promoter.

Preferential induction of cytochrome P450 1A1 over cytochrome P450 1B1 in human breast epithelial cells following exposure to quercetin

Estrogen metabolism is suggested to play an important role in estrogen-induced breast carcinogenesis. Epidemiologic studies suggest that diets rich in phytoestrogens are associated with a reduced risk of breast cancer. Phytoestrogens are biologically active plant compounds that structurally mimic 17beta-estradiol (E(2)). We hypothesize that phytoestrogens, may provide protection against breast carcinogenesis by altering the expression of estrogen-metabolizing enzymes cytochrome P450 1A1 (Cyp1A1) and 1B1 (Cyp1B1). Cyp1A1 and Cyp1B1 are responsible for the metabolism of E(2) to generate 2-hydroxyestradiol (2-OHE(2)) and 4-hydroxyestradiol (4-OHE(2)), respectively. Studies suggest that 2-OHE(2) and 2-methoxyestradiol may protect against breast carcinogenesis, while 4-OHE(2) is carcinogenic in rodent models. Thus, agents that increase the metabolism of E(2) by Cyp1A1 to produce 2-OHE(2) may have chemoprotective properties. The human immortalized non-neoplastic breast cell line MCF10F was treated with quercetin at 10 and 50muM concentrations for time points ranging from 3 to 48h. Total RNA and protein were isolated. Real-time PCR was used to measure the expression of Cyp1A1 and Cyp1B1 mRNA. Quercetin treatment produced differential regulation of Cyp1A1 and Cyp1B1 mRNA expression in a time- and dose-dependent manner. Treatment with 10 and 50 microM doses of quercetin produced 6- and 11-times greater inductions of Cyp1A1 mRNA over Cyp1B1 mRNA, respectively. Furthermore, quercetin dramatically increased Cyp1A1 protein levels and only slightly increased Cyp1B1 protein levels in MCF10F cells. Thus, our data suggest that phytoestrogens may provide protection against breast cancer by modulating expression of estrogen-metabolizing genes such that production of the highly carcinogenic estrogen metabolite 4-OHE(2) by Cyp1B1 is reduced and the production of the less genotoxic 2-OHE(2) by Cyp1A1 is increased.

Influence of diet on metastasis and tumor dormancy

Tumor metastasis is responsible for most cancer deaths, and can occur after long periods of tumor dormancy. Information learned from experimental studies on tumor metastasis and dormancy is shedding light on mechanisms responsible and possible therapeutic approaches. 'Seed' (the cancer cell) and 'soil' (the microenvironment of the secondary organ) factors contribute to metastatic outcome. This review considers the possibility that various dietary components may affect both 'seed' and 'soil' compartments, thereby influencing the growth of metastases, and discusses an experimental study on dietary genistein that illustrates this concept. While studies on human diet are complex, the possibility that relatively non-toxic dietary intervention strategies could impact on metastasis and patient survival is attractive and worthy of further study in appropriate experimental models of metastasis and tumor dormancy.

Early life and adult exposure to isoflavones and breast cancer risk

Soy and red-clover isoflavones are commonly consumed within the diet or as a dietary supplement due to a range of presumed beneficial health benefits. These isoflavones are thought to protect against heart diseases as well as breast and other types of cancer. Isoflavones are structurally similar to estrogens and may act as estrogen agonists or antagonists by binding to estrogen receptors. Because of an increased use of isoflavones in processed foods and dietary supplements as well as the greater consumption of soy products, dietary intakes of isoflavones are increasing in children and adolescents in North America. Estrogens are a known component of numerous hormone related cancers including breast cancer. It is with these facts in mind that we review the existing epidemiological and experimental animal studies for a resolution to a proposed correlation between increased isoflavone consumption and breast cancer. There is conflicting evidence from epidemiological, intervention and experimental animal studies regarding the chemopreventing effects of soy isoflavones in breast cancer. Isoflavones are weak estrogens and their effect depends upon the dose, time of exposure and species involved. It would, therefore, not be safe to indisputably accept soy or red-clover as a source of isoflavone resource to prevent breast cancer.

Equol status modifies the association of soy intake and mammographic density in a sample of postmenopausal women

Only 30% to 50% of people produce the daidzein-metabolite equol after eating soy. We conducted a cross-sectional study of the associations between equol status, intake of soy foods, and mammographic density in a sample of postmenopausal women recruited at a radiology clinic near Buffalo, New York. Participants were 48 to 82 years old, had no history of cancer or breast reduction/augmentation, and no recent use of antibiotics or hormones. Percent density was measured by computer-assisted analysis of digitized images of craniocaudal films. Equol status was assessed using a soy-challenge protocol and usual soy intake by questionnaire. General linear models were used to assess independent and joint effects of equol status and intake of soy on multivariate adjusted percent density (covariates included age, body mass index, parity, age at first birth, and ever use of combined hormone therapy). Of 325 enrolled, 232 (71%) participants completed study assessments and are included in the present analysis. Mean percent density was 34% (+/-18%). Seventy-five (30%) participants were producers of equol. Forty-three (19%) participants reported regularly eating >1 soy food or supplement/wk. There were no significant independent associations of equol status or soy intake with percent density, but the interaction between these factors was significant (P < 0.01). Among equol producers, those with weekly soy intake had lower percent density (30.7% in weekly consumers of soy versus 38.9% in others; P = 0.08); among nonproducers, weekly soy intake was associated with higher percent density (37.5% in weekly soy consumers versus 30.7% in others; P = 0.03). Results suggest that equol producers and nonproducers may experience different effects of dietary soy on breast tissue.

Phytoestrogens and breast cancer prevention: possible mechanisms of action

OBJECTIVE

Phytoestrogens display an array of pharmacologic properties, and in recent years investigation of their potential as anticancer agents has increased dramatically. In this article we review the published literature related to phytoestrogens and breast cancer as well as suggest the possible mechanisms that may underlie the relationship between phytoestrogens and breast cancer.

DATA SOURCES

Electronic searches on phytoestrogens and breast cancer were performed on MEDLINE and EMBASE in June 2007. No date restriction was placed on the electronic search.

DATA EXTRACTION

We focused on experimental data from published studies that examined the characteristics of phytoestrogens using in vivo or in vitro models. We also include human intervention studies in this review.

DATA SYNTHESIS

We evaluated evidence regarding the possible mechanisms of phytoestrogen action. Discussions of these mechanisms were organized into those activities related to the estrogen receptor, cell growth and proliferation, tumor development, signaling pathways, and estrogen-metabolizing enzymes.

CONCLUSIONS

We suggest that despite numerous investigations, the mechanisms of phytoestrogen action in breast cancer have yet to be elucidated. It remains uncertain whether these plant compounds are chemoprotective or whether they may produce adverse outcomes related to breast carcinogenesis.

Soy isoflavones decrease the catechol-O-methyltransferase-mediated inactivation of 4-hydroxyestradiol in cultured MCF-7 cells

The tissue concentrations of the female sex hormone 17beta-estradiol (E2) and its reactive catechol metabolites such as 4-hydroxyestradiol (4-HO-E2) play important roles in hormonal carcinogenesis. They are influenced by the activity of local enzymes involved in the metabolic activation and inactivation of E2. In the mammary gland, catechol estrogens are predominately inactivated by catechol-O-methyltransferase (COMT). Food supplements containing the soy isoflavones genistein and daidzein are consumed because they are believed to protect from breast cancer; however, this proposed benefit is controversial. The aim of the present study was to investigate the influence of soy isoflavones on the gene expression and activity of COMT in cultured human mammary adenocarcinoma MCF-7 cells. Levels of COMT messenger RNA (mRNA) were determined by reverse transcription/competitive polymerase chain reaction and COMT activity was determined by high-performance liquid chromatography analysis of the methylation products of both the model substrate quercetin and the physiological relevant substrate 4-HO-E2. Our study demonstrates for the first time that soy isoflavones at hormonally active concentrations cause a significant reduction of both COMT mRNA levels and COMT activity as well as of the methylation of 4-HO-E2. Experiments using the estrogen receptor (ER) antagonist ICI 182,780 support a role of the ER in the isoflavone-induced down-regulation of COMT expression. Thus, this study not only demonstrates that hormonally active concentrations of soy isoflavones inhibit the detoxification of catechols in this human breast cancer cell line but also implies that diet might influence COMT activity to a greater extent than heretofore recognized.

Epidemiology of soy exposures and breast cancer risk

Most of the early studies published on soy and breast cancer were not designed to test the effect of soy; the assessment of soy intake was usually crude and few potential confounders were considered in the analysis. In this review, we focused on studies with relatively complete assessment of dietary soy exposure in the targeted populations and appropriate consideration for potential confounders in the statistical analysis of study data. Meta-analysis of the 8 (1 cohort, 7 case-control) studies conducted in high-soy-consuming Asians show a significant trend of decreasing risk with increasing soy food intake. Compared to the lowest level of soy food intake (<or=5 mg isoflavones per day), risk was intermediate (OR=0.88, 95% confidence interval (CI)=0.78-0.98) among those with modest ( approximately 10 mg isoflavones per day) intake and lowest (OR=0.71, 95% CI=0.60-0.85) among those with high intake (>or=20 mg isoflavones per day). In contrast, soy intake was unrelated to breast cancer risk in studies conducted in the 11 low-soy-consuming Western populations whose average highest and lowest soy isoflavone intake levels were around 0.8 and 0.15 mg per day, respectively. Thus, the evidence to date, based largely on case-control studies, suggest that soy food intake in the amount consumed in Asian populations may have protective effects against breast cancer.

WHI and WHIMS follow-up and human studies of soy isoflavones on cognition

Recent follow-up analyses of the previous findings from the Women's Health Initiative and the Women's Health Initiative Memory Study confirmed some health benefits of estrogen-containing hormone therapy (HT) in women within 10 years from the onset of menopause. However, the potential risks associated with long-term administration of HT, such as breast cancer and stroke, remain a concern for therapy recipients, underlying the need for an alternative treatment that is functionally equivalent but with a greater safety profile. Owing to their structural and functional resemblance to mammalian estrogens and lack of evident adverse effects, research interest in plant-derived phytoestrogens has increased in the past decade. While multiple health-promoting benefits of phytoestrogens have been proposed from basic science, the clinical data remain inconclusive. This review provides a comparative analysis of human studies on the effects of soy-based isoflavones on cognition. Of the eight studies published in 2000-2007, seven were conducted in postmenopausal women, four of which revealed a positive impact of isoflavones on cognitive function. Multiple factors could have contributed to the discrepant outcomes across studies, such as variation in the composition of phytoestrogen interventions and the heterogeneous characteristics of the study population. Thus, a well-designed clinical study based on a standardized stable formulation in a well-characterized study population is required in order to reach a clinical consensus. A formulation composed of select estrogen receptor beta-selective phytoestrogens with a rationally designed composition would avoid the potential antagonism present in a mixture and thus enhance therapeutic efficacy. In addition, inclusion of equol in a study formulation offers a potential synergistic effect from equol in both equol-producing and nonproducing individuals, as well as added benefits for men. With respect to the design of study population, a clinically consistent effect could potentially be achieved by stratifying populations based on genotype, age, hormonal history and even diets. Development of an effective phytoestrogen formulation would benefit both women and men to prevent or treat hormone-dependent conditions and, most of all, to improve neurological health and reduce the risk of Alzheimer's disease.

Aromatase inhibition by synthetic lactones and flavonoids in human placental microsomes and breast fibroblasts--a comparative study

Interference of exogenous chemicals with the aromatase enzyme can be useful as a tool to identify chemicals that could act either chemopreventive for hormone-dependent cancer or adverse endocrine disruptive. Aromatase is the key enzyme in the biosynthesis of steroids, as it converts androgens to estrogens. Certain flavonoids, plant derived chemicals, are known catalytic aromatase inhibitors. Various systems are in use to test aromatase inhibitory properties of compounds. Commonly used are microsomes derived from ovary or placental tissue characterized by high aromatase activity. To a lesser extent whole cell systems are used and specifically cell systems that are potential target tissue in breast cancer development. In this study aromatase inhibitory properties of fadrozole, 8-prenylnaringenin and a synthetic lactone (TM-7) were determined in human placental microsomes and in human primary breast fibroblasts. In addition, apigenin, chrysin, naringenin and two synthetic lactones (TM-8 and TM-9) were tested in human microsomes only. Comparison of the aromatase inhibitory potencies of these compounds between the two test systems showed that the measurement of aromatase inhibition in human placental microsomes is a good predictor of aromatase inhibition in human breast fibroblasts.

Soy isoflavones as safe functional ingredients

In recent years, isoflavones have increased in popularity as an alternative to estrogen therapy, particularly after the Women's Health Initiative demonstrated an increased risk of breast cancer, stroke, and heart attacks in response to estrogen and progesterone intervention. Isoflavones are heterocyclic phenols with structural similarity to estradiol-17beta and selective estrogen receptor modulators. Actions at the cellular level depend on the target tissue, receptor status of the tissue, and the level of endogenous estrogen. Clinical studies of soy-based diets evaluating the relation between soy consumption and serum lipid concentrations revealed that soy consumption significantly decreased total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels. Epidemiological studies suggest a protective effect of soy protein on breast tissue as evidenced by the lower rates of breast cancer in East Asian countries where soy is a predominant part of the diet. Soy products also alleviate menopausal symptoms by reducing hot flashes. However, whether these biological effects of soy products originated from isoflavones is not clear. Furthermore, data available from human studies on the effect of isoflavones on osteoporosis are limited, and additional studies are needed to support a role in osteoporosis prevention. To date, no adverse effects of short- or long-term use of soy proteins are known in humans, and the only adverse effects known are those reported in animals. In conclusion, isoflavones are biologically active compounds, and current data are insufficient to draw definitive conclusions regarding the use of isoflavones as an alternative to estrogen for hormone replacement in postmenopausal women. Large, long-term intervention studies examining adverse effects and disease outcomes are needed before definitive conclusion can be drawn.

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.

Comparison of genistein metabolism in rats and humans using liver microsomes and hepatocytes

Species differences and metabolism are the most crucial factors in considering the effects of genistein. The aim of this study was to have a better knowledge of the metabolic fate of genistein in humans as compared with rats. For this purpose, radiolabeled genistein was incubated with human and rat liver microsomes and with cryopreserved hepatocytes from both species. Incubations were performed using a wide range of genistein concentrations to analyze the kinetics of formation of the metabolites. Metabolite profiling was obtained using an HPLC system connected to a radioactivity detector. Identification of the metabolites was based on their retention times as compared with those of authentic standards and on LC-MS (ESI-MS/MS) or NMR analyses. In both species, liver microsomes produced the same three hydroxylated metabolites (8-OH, 6-OH and 3'-OH-genistein) whereas cryopreserved hepatocytes produced the same glucurono- and sulfo-conjugates (genistein 4'-O-sulfate 7-O-glucuronide, genistein 7-O-glucuronide, genistein 4'-O-glucuronide, genistein 7-O-sulfate and genistein 4'-O-sulfate). The rate of metabolism varied with species. 3'-Hydroxygenistein was the predominant metabolite produced by rat liver microsomes, whereas in humans 3'-hydroxy and 8-hydroxygenistein were produced in the same range. In both human and rat hepatocyte incubations, genistein 7-O-glucuronide represented more than 50% of the incubated dose. Our results on hepatocytes confirmed the predominance of conjugation reaction compared to oxidative reaction observed in vivo.

Phytochemicals for health, the role of pulses

Pulses are the seeds of legumes that are used for human consumption and include peas, beans, lentils, chickpeas, and fava beans. Pulses are an important source of macronutrients, containing almost twice the amount of protein compared to cereal grains. In addition to being a source of macronutrients and minerals, pulses also contain plant secondary metabolites that are increasingly being recognised for their potential benefits for human health. The best-studied legume is the soybean, traditionally regarded as an oilseed crop rather than a pulse. The potential health benefits of soy, particularly with respect to isoflavone content, have been the subject of much research and the focus of several reviews. By comparison, less is known about pulses. This review investigates the health potential of pulses, examining the bioactivity of pulse isoflavones, phytosterols, resistant starch, bioactive carbohydrates, alkaloids and saponins. The evidence for health properties is considered, as is the effect of processing and cooking on these potentially beneficial phytochemicals.

The prevalence of intrinsic subtypes and prognosis in breast cancer patients of different races

A recent report indicated that a high prevalence of basal-like breast tumors (estrogen receptor [ER]-negative, progesterone receptor [PR]-negative, human epidermal growth factor receptor [HER] 2-negative, and cytokeratin 5/6-positive and/or HER1-positive) could contribute to a poor prognosis in African American women with breast cancer. It has been reported that Japanese women with breast cancer have a significantly better survival rate than other races in the USA. These findings suggest that breast cancers in Japanese women have favorable biological characteristics. To clarify this hypothesis, we conducted a cohort study to investigate the prevalence of intrinsic subtypes and prognosis for each subtype in 793 Japanese patients. This study revealed a very low prevalence (only 8%) of basal-like breast tumors with aggressive biological characteristics in Japanese patients. Survival analysis showed a significantly poorer prognosis in patients with basal-like tumors than in those with luminal A tumors (ER- and/or PR-positive, and HER2-negative) with favorable biological characteristics. These findings support the hypothesis that breast cancers in Japanese women have more favorable biological characteristics and a better prognosis than those in other races. In conclusion, the prevalence of basal-like breast tumors could influence the prognosis of breast cancer patients of different races. The prevalence of intrinsic subtypes should be taken into account when analyzing survival data in a multi-racial/international clinical study.

Alterations of Metastasis-Related Genes Identified Using an Oligonucleotide Microarray of Genistein-Treated HCC1395 Breast Cancer Cells

Genistein, one of the major isoflavones, potently inhibits the growth and metastasis of breast cancer. However, the precise molecular mechanism in metastasis inhibition is not clear. We investigated the effect of genistein in HCC1395 cells, a cell line derived from an early-stage primary breast cancer. Genistein dose dependently both decreased cell viability and inhibited the invasion potential. We used human oligonucleotide microarrays to determine the gene expression profile altered by genistein treatment. TFPI-2, ATF3, DNMT1, and MTCBP-1, which inhibit invasion and metastasis, were upregulated, and MMP-2, MMP-7, and CXCL12, which promote invasion and metastasis, were downregulated. We used quantitative real-time polymerase chain reaction to verify the microarray data at the mRNA level. We conclude that genistein-induced alternations of gene expression involving metastasis may be exploited for devising chemopreventive and therapeutic strategies, particularly for early-stage 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.

Black cohosh (Cimicifuga racemosa [L.] Nutt.): safety and efficacy for cancer patients

GOALS OF WORK

Black cohosh is commonly used to treat hot flashes and other symptoms associated with menopause. It is thought to have multiple mechanisms of action, including potential phytoestrogenic properties. This has caused some concern about its use by patients with hormone-sensitive cancer. This paper will present the results of a systematic review of the safety and efficacy of black cohosh (Cimicifuga racemosa [L.] Nutt.) in patients with cancer.

MATERIALS AND METHODS

A critical assessment of clinical (n = 5) and preclinical (n = 21) studies of black cohosh and cancer (breast and prostate) to treat hot flashes and other related symptoms is presented. In addition, clinical studies, case reports, animal studies, and in vitro assessments of the safety of black cohosh for patients with hormonally sensitive cancers is summarized and interpreted.

MAIN RESULTS

In general, the research assessing efficacy of black cohosh for the treatment of hot flashes in women with breast cancer is inconclusive. There is laboratory evidence of antiproliferative properties but no confirmation from clinical studies for a protective role in cancer prevention. Black cohosh seems to have a relatively good safety profile. Concerns about liver toxicity are inconclusive. With relevance to cancer patients, black cohosh also seems not to exhibit phytoestrogenic activity and is in fact possibly an inhibitor of tumor growth.

CONCLUSIONS

The use of black cohosh appears to be safe in breast cancer patients without risk for liver disease, although further research is needed in this and other populations.

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.