Genistein inhibits growth of estrogen-independent human breast cancer cells in culture but not in athymic mice

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

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

Understanding the Phytoestrogen Genistein Actions on Breast Cancer: Insights on Estrogen Receptor Equivalence, Pleiotropic Essence and Emerging Paradigms in Bioavailability Modulation

Prevalent as a major phenolic ingredient of soy and soy products, genistein is recognized as an eminent phytoestrogen owing to its interacting ability with estrogen receptors (ERs). The metabolic conversion of plant-derived genistin to genistein by gut microbes and intestinal enzymes enhances its absorption at intestinal pH of ~7.5-7.8. Genistein interferes in breast cancer (BC) development via pleiotropic actions on cell proliferation, survival, angiogenesis, and apoptosis. Though multiple investigations have demonstrated genistein intake-driven reduced BC risk, similar efficacy has not been replicated in clinical trials. Furthermore, multiple studies have structurally and functionally equated genistein extents with 17-β-estradiol (E2), the most available physiological estrogen in females, culminating in aggravated BC growth. Of note, both genistein and E2 function via interacting with ERs (ERα and ERβ). However, although E2 shows almost equal affinity towards both ERα and ERβ, genistein shows more affinity towards ERβ than ERα. Our cautious literature survey revealed typical intake mode, ER expression pattern and the ratio of ERα and ERβ, transactivators/ regulators of ERα and ERβ expression and activities, patient age, and menopausal status as decisive factors affecting genistein BC activities. Of further interest are the mechanisms by which genistein inhibits triple-negative breast cancers (TNBCs), which lack ERs, progesterone receptors (PRs), and human epidermal growth factor receptors (HER2). Herein, we attempt to understand the dosage-specific genistein actions in BC cells and patients with an insight into its better response via derivative development, nanocarrier-assisted, and combinatorial delivery with chemotherapeutic drugs.

Molecular and Cellular Mechanisms of Propolis and Its Polyphenolic Compounds against Cancer

In recent years, interest in natural products such as alternative sources of pharmaceuticals for numerous chronic diseases, including tumors, has been renewed. Propolis, a natural product collected by honeybees, and polyphenolic/flavonoid propolis-related components modulate all steps of the cancer progression process. Anticancer activity of propolis and its compounds relies on various mechanisms: cell-cycle arrest and attenuation of cancer cells proliferation, reduction in the number of cancer stem cells, induction of apoptosis, modulation of oncogene signaling pathways, inhibition of matrix metalloproteinases, prevention of metastasis, anti-angiogenesis, anti-inflammatory effects accompanied by the modulation of the tumor microenvironment (by modifying macrophage activation and polarization), epigenetic regulation, antiviral and bactericidal activities, modulation of gut microbiota, and attenuation of chemotherapy-induced deleterious side effects. Ingredients from propolis also "sensitize" cancer cells to chemotherapeutic agents, likely by blocking the activation of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). In this review, we summarize the current knowledge related to the the effects of flavonoids and other polyphenolic compounds from propolis on tumor growth and metastasizing ability, and discuss possible molecular and cellular mechanisms involved in the modulation of inflammatory pathways and cellular processes that affect survival, proliferation, invasion, angiogenesis, and metastasis of the tumor.

Mechanism of Soy Isoflavone Daidzein-Induced Female-Specific Anorectic Effect

Epidemiological studies suggest that regular intake of soy isoflavone exerts a preventive effect on postmenopausal obesity and other forms of dysmetabolism. Estrogens inhibit eating behavior. Soy isoflavones may act as estrogen agonist in estrogen-depleted conditions, whereas they may either act as an estrogen antagonist or be ineffective in estrogen-repleted conditions. We investigated the effects of dietary soy isoflavone on food intake under various estrogen conditions using male, ovariectomized (OVX), and non-OVX female rats, and compared the effects with those of estradiol. We found that soy isoflavones reduced food intake in females specifically, regardless of whether ovariectomy had been performed, whereas subcutaneous implantation of estradiol pellet did not reduce food intake in intact female rats, but did so in OVX female and male rats. Contrary to this hypothesis, the reduction in food intake may not be caused by the estrogenic properties of soy isoflavones. It is of great interest to understand the mechanisms underlying the anorectic effects of soy isoflavones. In this non-systematic review, we summarize our recent studies that have investigated the bioactive substances of anorectic action, pharmacokinetic properties of soy isoflavones, and the modification of central and peripheral signals regulating appetite by soy isoflavones, and selected studies that were identified via database mining.

Genistein, a Potential Phytochemical against Breast Cancer Treatment-Insight into the Molecular Mechanisms

Breast cancer (BC) is one of the most common malignancies in women. Although widespread successful synthetic drugs are available, natural compounds can also be considered as significant anticancer agents for treating BC. Some natural compounds have similar effects as synthetic drugs with fewer side effects on normal cells. Therefore, we aimed to unravel and analyze several molecular mechanisms of genistein (GNT) against BC. GNT is a type of dietary phytoestrogen included in the flavonoid group with a similar structure to estrogen that might provide a strong alternative and complementary medicine to existing chemotherapeutic drugs. Previous research reported that GNT could target the estrogen receptor (ER) human epidermal growth factor receptor-2 (HER2) and several signaling molecules against multiple BC cell lines and sensitize cancer cell lines to this compound when used at an optimal inhibitory concentration. More specifically, GNT mediates the anticancer mechanism through apoptosis induction, arresting the cell cycle, inhibiting angiogenesis and metastasis, mammosphere formation, and targeting and suppressing tumor growth factors. Furthermore, it acts via upregulating tumor suppressor genes and downregulating oncogenes in vitro and animal model studies. In addition, this phytochemical synergistically reverses the resistance mechanism of standard chemotherapeutic drugs, increasing their efficacy against BC. Overall, in this review, we discuss several molecular interactions of GNT with numerous cellular targets in the BC model and show its anticancer activities alone and synergistically. We conclude that GNT can have favorable therapeutic advantages when standard drugs are not available in the pharma markets.

Natural product-based Radiopharmaceuticals:Focus on curcumin and its analogs, flavonoids, and marine peptides

Natural products provide a bountiful supply of pharmacologically relevant precursors for the development of various drug-related molecules, including radiopharmaceuticals. However, current knowledge regarding the importance of natural products in developing new radiopharmaceuticals remains limited. To date, several radionuclides, including gallium-68, technetium-99m, fluorine-18, iodine-131, and iodine-125, have been extensively studied for the synthesis of diagnostic and therapeutic radiopharmaceuticals. The availability of various radiolabeling methods allows the incorporation of these radionuclides into bioactive molecules in a practical and efficient manner. Of the radiolabeling methods, direct radioiodination, radiometal complexation, and halogenation are generally suitable for natural products owing to their simplicity and robustness. This review highlights the pharmacological benefits of curcumin and its analogs, flavonoids, and marine peptides in treating human pathologies and provides a perspective on the potential use of these bioactive compounds as molecular templates for the design and development of new radiopharmaceuticals. Additionally, this review provides insights into the current strategies for labeling natural products with various radionuclides using either direct or indirect methods.

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Potential use of natural products for the development of diagnostic and therapeutic radiopharmaceuticals.

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Profile of potential natural products as molecular templates for the synthesis of new radiopharmaceuticals: Focus on curcumin and its closely related substances, flavonoids, and marine peptides.

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Radiolabeling strategies, challenges, and examples of natural product-based radiopharmaceuticals under investigation.

Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data

Soybeans are a rich source of isoflavones, which are classified as phytoestrogens. Despite numerous proposed benefits, isoflavones are often classified as endocrine disruptors, based primarily on animal studies. However, there are ample human data regarding the health effects of isoflavones. We conducted a technical review, systematically searching Medline, EMBASE, and the Cochrane Library (from inception through January 2021). We included clinical studies, observational studies, and systematic reviews and meta-analyses (SRMA) that examined the relationship between soy and/or isoflavone intake and endocrine-related endpoints. 417 reports (229 observational studies, 157 clinical studies and 32 SRMAs) met our eligibility criteria. The available evidence indicates that isoflavone intake does not adversely affect thyroid function. Adverse effects are also not seen on breast or endometrial tissue or estrogen levels in women, or testosterone or estrogen levels, or sperm or semen parameters in men. Although menstrual cycle length may be slightly increased, ovulation is not prevented. Limited insight could be gained about possible impacts of in utero isoflavone exposure, but the existing data are reassuring. Adverse effects of isoflavone intake were not identified in children, but limited research has been conducted. After extensive review, the evidence does not support classifying isoflavones as endocrine disruptors.

Phenolic Compounds of Soybean Seeds from Two European Countries and Their Antioxidant Properties

There is only a small acreage of planted soybeans in northern Europe, as the global production of this crop is mainly dictated by the warmer temperatures needed for bountiful yields. The defense response of soybean plants to a cold climate entails the secretion of specific compounds which help mitigate oxidative stress, i.e., antioxidants, including phenolic compounds. The objective of this study was to examine differences in the concentrations of phenolic compounds, their antioxidant properties, and the concentration of key isoflavones (namely genistein, daidzein, malonyl daidzein, malonyl genistein, and daidzin) in the seeds of six soybean cultivars from two different regions of Europe, namely Poland and France. The total phenolic contents, isoflavone levels, and in vitro antioxidant capacities of soybean seeds from most of the investigated cultivars of northeast Europe were found to be greater than those from southwest Europe. The phenolic compounds of seed extracts are primarily responsible for the free-radical scavenging of soybeans. Factors regulating the production of phenolic compounds in the seeds have not been thoroughly elucidated. Hence, the results presented in this paper can be useful in the selection of soybean cultivars with higher levels of seed phenolics, because of their beneficial impact on human health and on the soybean's defense mechanism against plant stresses.

Investigating the Antiangiogenic, Anti-drug Resistance and Apoptotic Effects of Soy Isoflavone Extract Alone or in Combination with Docetaxel on Murine 4T1 Breast Tumor Model

BACKGROUND

One major concern in the treatment of cancer patients during chemotherapy is drug resistance. Here we investigated the effects of soy isoflavone extracts alone or in combination with Docetaxel on the drug resistance, angiogenesis, apoptosis, and tumor volume in mouse 4T1 breast tumor model.

METHODS

Sixty female BALB/c mice were randomly divided into 4 groups: control, dietary soy isoflavone extract [Iso, 100 mg/kg diet (0.01%)], Docetaxel (10 mg/kg) injection, and the combination of dietary soy isoflavone extract and intravenous Docetaxel injection (Docetaxel + Iso). One week after the third injection, the breast tumors of eight mice from each group were excised to analyze NF-κBp65' vascular endothelial growth factor receptor-2 (VEGFR2) and Pgp gene and protein expressions and the other seven mice were monitored for survival rate analysis until they died.

RESULTS

NF-κBp65 gene and protein expressions were significantly lower in the Docetaxel + Iso group in comparison with that of the Docetaxel group. VEGFR2 protein expression in the Docetaxel + Iso and Iso groups was significantly lower than that of the Docetaxel group.

CONCLUSION

These findings may indicate that the combined use of isoflavone extracts together with chemotherapeutic agents has more efficient anti-carcinogenic effects than their individual use.

Soy isoflavone exposure through all life stages accelerates 17β-estradiol-induced mammary tumor onset and growth, yet reduces tumor burden, in ACI rats

There is an ongoing debate whether the intake of soy-derived isoflavones (sISO) mediates beneficial or adverse effects with regard to breast cancer risk. Therefore, we investigated whether nutritional exposure to a sISO-enriched diet from conception until adulthood impacts on 17β-estradiol (E2)-induced carcinogenesis in the rat mammary gland (MG). August-Copenhagen-Irish (ACI) rats were exposed to dietary sISO from conception until postnatal day 285. Silastic tubes containing E2 were used to induce MG tumorigenesis. Body weight, food intake, and tumor growth were recorded weekly. At necropsy, the number, position, size, and weight of each tumor were determined. Plasma samples underwent sISO analysis, and the morphology of MG was analyzed. Tumor incidence and multiplicity were reduced by 20 and 56 %, respectively, in the sISO-exposed rats compared to the control rats. Time-to-tumor onset was shortened from 25 to 20 weeks, and larger tumors developed in the sISO-exposed rats. The histological phenotype of the MG tumors was independent of the sISO diet received, and it included both comedo and cribriform phenotypes. Morphological analyses of the whole-mounted MGs also showed no diet-dependent differences. Lifelong exposure to sISO reduced the overall incidence of MG carcinomas in ACI rats, although the time-to-tumor was significantly shortened.

Quantitative phosphoproteomics reveals genistein as a modulator of cell cycle and DNA damage response pathways in triple-negative breast cancer cells

Around one sixth of breast cancer cases are classified as triple-negative breast cancer (TNBC), named after the absence of the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2); however, patients with TNBC suffer from poor clinical outcome and shortage of targeted therapy. Genistein, an estrogenic soy isoflavone, shows anticancer effects in TNBC cells such as inducing G2/M cell cycle arrest and apoptosis. However, the underlying mechanism of its anticancer effects is poorly understood and its elucidation can help the development of novel therapeutic strategies for TNBC. In this study, by combining isobaric tag-based TMT labeling with titanium dioxide-based phosphopeptide enrichment, we quantitated 5,445 phosphorylation sites on 2,008 phosphoproteins in the TNBC cell line MDA-MB-231, upon genistein treatment. Our analysis revealed 332 genistein-regulated phosphorylation sites on 226 proteins. Our data show that genistein can regulate several biological processes during the cell cycle, including DNA replication, cohesin complex cleavage, and kinetochore formation. Furthermore, genistein can also activate DNA damage response, including activation of ATR and BRCA1 complex. Overall, our study presents evidence at a phosphoproteomic level that genistein is able to inhibit TNBC cell growth by regulating the cell cycle and DNA damage response in a more complex manner. Our findings help elucidate the mechanisms through which genistein exerts its anticancer effects in TNBC cells.

Consumption of soy isoflavone enriched bread in men with prostate cancer is associated with reduced proinflammatory cytokines and immunosuppressive cells

We hypothesized that soy phytochemicals may have immunomodulatory properties that may affect prostate carcinogenesis and progression. A randomized, phase II trial was conducted in 32 patients with prostate cancer with asymptomatic biochemical recurrence but no measurable disease on standard staging studies. Patients were randomized to two slices of soy bread (34 mg isoflavones/slice) or soy bread containing almond powder daily as a source of β-glucosidase. Flow cytometry and bioplex assays were used to measure cytokines or immune cell phenotype in blood at baseline (day 0) and following intervention (day 56). Adequate blood samples were available at enrollment and day 56 and evaluated. Multiple plasma cytokines and chemokines were significantly decreased on day 56 versus baseline. Subgroup analysis indicated reduced TH1 (P = 0.028) and myeloid-derived suppressor cell (MDSC)-associated cytokines (P = 0.035). TH2 and TH17 cytokines were not significantly altered. Phenotypic analysis revealed no change in CD8(+) or CD4(+) T cells but showed increased CD56(+) natural killer (NK) cells (P = 0.038). The percentage of cells with a T regulatory cell phenotype (CD4(+)CD25(+)FoxP3(+)) was significantly decreased after 56 days of soy bread (P = 0.0136). Significantly decreased monocytic (CD33(+)HLADR(neg)CD14(+)) MDSC were observed in patients consuming soy bread (P = 0.0056). These data suggest that soy bread modulates systemic soluble and cellular biomarkers consistent with limiting inflammation and suppression of MDSCs. Additional studies to elucidate impact on the carcinogenic process or as a complement to immune-based therapy are required.

Adverse Effects of Genistein in a Mucopolysaccharidosis Type I Mouse Model

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disorder characterized by diminished degradation of the glycosaminoglycans heparan sulfate (HS) and dermatan sulfate (DS). Patients present with a variety of symptoms, including severe skeletal disease. Current therapeutic strategies have only limited effects on bone disease. The isoflavone genistein has been studied as a potential therapy for the mucopolysaccharidoses because of its putative ability to inhibit GAG synthesis and subsequent accumulation. Cell, animal, and clinical studies, however, showed variable outcomes. To determine the effects of genistein on MPS I-related bone disease, wild-type (WT) and MPS I mice were fed a genistein-supplemented diet (corresponding to a dose of approximately 160 mg/kg/day) for 8 weeks. HS and DS levels in bone and plasma remained unchanged after genistein supplementation, while liver HS levels were decreased in genistein-fed MPS I mice as compared to untreated MPS I mice. Unexpectedly, genistein-fed mice exhibited significantly decreased body length and femur length. In addition, 60% of genistein-fed MPS I mice developed a scrotal hernia and/or scrotal hydrocele, manifestations, which were absent in WT or untreated MPS I mice. In contrast to studies in MPS III mice, our study in MPS I mice demonstraes no beneficial but even potential adverse effects of genistein supplementation. Our results urge for a cautious approach on the use of genistein, at least in patients with MPS I.

A hypothesis regarding the molecular mechanism underlying dietary soy-induced effects on seizure propensity

Numerous neurological disorders including fragile X syndrome, Down syndrome, autism, and Alzheimer’s disease are co-morbid with epilepsy. We have observed elevated seizure propensity in mouse models of these disorders dependent on diet. Specifically, soy-based diets exacerbate audiogenic-induced seizures in juvenile mice. We have also found potential associations between the consumption of soy-based infant formula and seizure incidence, epilepsy comorbidity, and autism diagnostic scores in autistic children by retrospective analyses of medical record data. In total, these data suggest that consumption of high levels of soy protein during postnatal development may affect neuronal excitability. Herein, we present our theory regarding the molecular mechanism underlying soy-induced effects on seizure propensity. We hypothesize that soy phytoestrogens interfere with metabotropic glutamate receptor signaling through an estrogen receptor-dependent mechanism, which results in elevated production of key synaptic proteins and decreased seizure threshold.

Effect of soy isoflavones on the growth of human breast tumors: findings from preclinical studies

Breast cancer is the most common cancer among women worldwide, and many women with breast cancer live more than 5 years after their diagnosis. Breast cancer patients and survivors have a greater interest in taking soy foods and isoflavone supplements. However, the effect of isoflavones on breast cancer remains controversial. Thus, it is critical to determine if and when isoflavones are beneficial or detrimental to breast cancer patients. According to the available preclinical data, high concentrations of isoflavones inhibit the proliferation of breast cancer cells, regardless of their estrogen receptor (ER) status. In comparison, genistein, a major isoflavone, has stimulated tumor growth at low concentrations and mitigated tamoxifen efficacy in ER-positive breast cancer. Studies have indicated that the relative levels of genistein and estrogen at the target site are important to determine the genistein effect on the ER-positive tumor growth. However, studies using ovariectomized mice and subcutaneous xenograft models might not truly reflect estrogen concentrations in human breast tumors. Moreover, it may be an oversimplification that isoflavones stimulate hormone-dependent tumor growth due to their potential estrogenic effect since studies also suggest nonestrogenic anticancer effects of isoflavones and ER-independent anticancer activity of tamoxifen. Therefore, the concentrations of isoflavones and estrogen in human breast tumors should be considered better in future preclinical studies and the parameters that can estimate those levels in breast tumors are required in human clinical/epidemiological investigation. In addition, it will be important to identify the molecular mechanisms that either inhibit or promote the growth of breast cancer cells by soy isoflavones, and use those molecules to evaluate the relevance of the preclinical findings to the human disease and to predict the health effects of isoflavones in human breast tumors.

Soy-based diet exacerbates seizures in mouse models of neurological disease

Seizures are a common phenotype in many neurological disorders including Alzheimer's disease, Down syndrome, and fragile X syndrome. Mouse models of these disorders overexpress amyloid-β protein precursor (AβPP) and amyloid-β (Aβ) and are highly susceptible to audiogenic-induced seizures (AGS). We observed decreased AGS in these mice fed a casein-based, purified diet (D07030301) as opposed to a standard soy protein-containing, non-purified diet (Purina 5015). Our objective in this manuscript was to determine if soy protein, and in particular soy isoflavones, in the Purina 5015 were contributing to the seizure phenotype. Wild running, AGS, and death rates were assessed in juvenile mice fed Purina 5015, D07030301, D07030301 containing soy protein, or D07030301 supplemented with individual isoflavones (750 mg/kg daidzein or genistein). A short treatment (3 days) with Purina 5015 induced wild running and AGS in Alzheimer's disease mice. A 3-day treatment with daidzein-supplemented diet, but not genistein, induced wild running in wild type mice. To understand the mechanism underlying daidzein activity, we assessed dendritic AβPP expression in primary, cultured, wild type neurons treated with daidzein or genistein. In vitro, daidzein significantly increased dendritic AβPP. Thus, the soy isoflavone daidzein recapitulated seizure induction in vivo and altered AβPP expression in vitro. These results have important implications for individuals on soy-based diets as well as for rodent model research.

Endometrial, breast and liver safety of soy isoflavones plus Lactobacillus sporogenes in post-menopausal women

OBJECTIVE

To assess the safety of a nutraceutical compound containing soy isoflavones and Lactobacillus sporogenes on endometrium, breast and liver function.

SETTING

Outpatient Menopausal Clinic.

STUDY DESIGN

130 healthy postmenopausal women suffering from menopausal symptoms were randomized to receive soy isoflavones 60 mg and Lactobacillus sporogenes 1 billion spores (group E: 65 women) or calcium and vitamin D₃ (group C: 65 women). Safety of the treatment was assessed at baseline and after 1 year taking into account endometrial thickness, mammographic density, serum levels of transaminases, γ-GT and bilirubin. Efficacy of the treatment was evaluated rating the score of menopausal symptoms at baseline and every 3 months. The statistical analysis was carried out with χ², Fisher exact's test and ANOVA.

RESULTS

After 12 months of treatment mammographic density, endometrial thickness and hepatic function did not show significant differences between groups, while menopausal symptoms were progressively and significantly reduced in severity and frequency during treatment with soy isoflavones plus Lactobacillus sporogenes versus calcium plus vitamin D₃.

CONCLUSION

A 12 months treatment with a nutraceutical compound based on isoflavones and Lactobacillus sporogenes at the recommended doses is safe for endometrium, mammary glands and liver function in postmenopausal women.

Current knowledge and future direction of research on soy isoflavones as a therapeutic agents

Isoflavones, the most abundant phytoestrogens in Soy beans, are structurally similar to 17beta-estradiol. The antioxidant property of the soy isoflavones, namely, genistein and daidzein is well established in different experimental models and also in clinical studies. The compounds have been found effective in the management of diabetes by acting on peroxisome proliferator-activated receptors. It reduces the risk of coronary heart disease by reducing the level of low-density lipoprotein and triglycerides. Soy isoflavones have the potential in the treatment of osteoporosis to act on osteoclasts further to inhibit tyrosine kinase. Among the soy isoflavones, genistein is the potential compound found effective in the treatment of cancer by acting on androgen receptor further to inhibit tyrosine kinases. In this article, various aspects of the diverse biological activities of soy isoflavones and their potential clinical implications with mechanism of action, especially in the treatment and prevention of diabetes, cardiovascular diseases, cancer, osteoporosis, neuroprotection, and also future area of research on soy isoflavones are reviewed and discussed.

Inhibition of proliferation and induction of G1-phase cell-cycle arrest by dFMGEN, a novel genistein derivative, in lung carcinoma A549 cells

Genistein (GEN) is a molecule of great interest as a potent chemopreventive agent against atherosclerosis and cancer. However, the bioavailability of GEN is very low in vivo. Our previous study showed that a GEN derivative, 7-difluoromethyl-5,4'-dimethoxygenistein (dFMGEN) has a better bioavailability than GEN in vivo. In this study, we further evaluated the efficacy of dFMGEN as a candidate for cancer therapy. We demonstrated that dFMGEN treatment decreased the viability of A549 cells in a concentration- and time-dependent manner and induced cell-cycle arrest at the G(1) phase. G(1) phase arrest was correlated with a significant reduction of Cdk4 and cyclin D1 protein level. Further studies showed that cyclin-dependent kinase (Cdk)4 and cyclin D1 protein-level decrease was caused by Cdk inhibitors p15, p21, and p27 level increase, and decreased protein level directly suppressed Rb protein phosphorylation and E2F-1 expression, then cell-cycle progression was arrested. Finally, we also found that dFMGEN has a dosage effect in suppressing tumor growth in vivo, and that dFMGEN was well tolerated by animals. In summary, our results suggest that dFMGEN has therapeutic potential for the treatment of human lung cancer.

Soy isoflavone phase II metabolism differs between rodents and humans: implications for the effect on breast cancer risk

BACKGROUND

Human and animal studies have produced conflicting results with regard to the effect of soy isoflavones on breast cancer risk. This may be due to differences in isoflavone metabolism.

OBJECTIVE

The objective of this study was to determine whether soy isoflavone phase II metabolism differs between humans and rodents.

DESIGN

Circulating total and unconjugated isoflavone concentrations were determined by mass spectrometry in plasma samples from 7 separate studies: 1) in Sprague-Dawley rats and in 3 strains of mice fed commercial soy-containing diets; 2) in Sprague-Dawley rats gavaged with genistein; 3) in healthy adults who consumed single servings of soy nuts, soy milk, and tempeh; 4) in healthy adults subchronically given soy milk; 5) in healthy women orally administered 50 mg genistein; 6) in healthy women orally administered 20 mg pure S-(-)equol; and 7) in 6-mo-old infants fed soy infant formula and later, at age 3 y, a soy germ isoflavone supplement.

RESULTS

The proportion of unconjugated genistein in plasma from adults and infants who consumed different soy foods, pure genistein, or an isoflavone supplement was <1% in steady state and <2% at peak concentrations. By contrast, rodents fed soy-containing diets conjugate isoflavones less efficiently. The plasma percentages of unconjugated genistein concentrations in Sprague-Dawley rats and C57BL/6, nude, and transgenic AngptL4B6 mice were 4.0 ± 0.6%, 4.6 ± 0.6%, 11.6 ± 0%, and 30.1 ± 4.3%, respectively, which represent 20, 23, 58, and 150 times that in humans.

CONCLUSION

The markedly higher circulating concentrations of biologically active (unconjugated) genistein in certain strains of mice cast doubt on the value of the use of these rodents for gaining insight into the effects of isoflavones in humans, especially with regard to the effects on breast tissue.

Individual and combined soy isoflavones exert differential effects on metastatic cancer progression

To investigate the effects soy isoflavones in established cancers, the role of genistein, daidzein, and combined soy isoflavones was studied on progression of subcutaneous tumors in nude mice created from green fluorescent protein (GFP) tagged-MDA-MB-435 cells. Following tumor establishment, mice were gavaged with vehicle or genistein or daidzein at 10 mg/kg body weight (BW) or a combination of genistein (10 mg/kg BW), daidzein (9 mg/kg BW), and glycitein (1 mg/kg BW) three times per week. Tumor progression was quantified by whole body fluorescence image analysis followed by microscopic image analysis of excised organs for metastases. Results show that daidzein increased while genistein decreased mammary tumor growth by 38 and 33% respectively, compared to vehicle. Daidzein increased lung and heart metastases while genistein decreased bone and liver metastases. Combined soy isoflavones did not affect primary tumor growth but increased metastasis to all organs tested, which include lung, liver, heart, kidney, and bones. Phosphoinositide-3-kinase (PI3-K) pathway real time PCR array analysis and western blotting of excised tumors demonstrate that genistein significantly downregulated 10/84 genes, including the Rho GTPases RHOA, RAC1, and CDC42 and their effector PAK1. Daidzein significantly upregulated 9/84 genes that regulate proliferation and protein synthesis including EIF4G1, eIF4E, and survivin protein levels. Combined soy treatment significantly increased gene and protein levels of EIF4E and decreased TIRAP gene expression. Differential regulation of Rho GTPases, initiation factors, and survivin may account for the disparate responses of breast cancers to genistein and daidzein diets. This study indicates that consumption of soy foods may increase metastasis.

Guidance from an NIH workshop on designing, implementing, and reporting clinical studies of soy interventions

The NIH sponsored a scientific workshop, "Soy Protein/Isoflavone Research: Challenges in Designing and Evaluating Intervention Studies," July 28-29, 2009. The workshop goal was to provide guidance for the next generation of soy protein/isoflavone human research. Session topics included population exposure to soy; the variability of the human response to soy; product composition; methods, tools, and resources available to estimate exposure and protocol adherence; and analytical methods to assess soy in foods and supplements and analytes in biologic fluids and other tissues. The intent of the workshop was to address the quality of soy studies, not the efficacy or safety of soy. Prior NIH workshops and an evidence-based review questioned the quality of data from human soy studies. If clinical studies are pursued, investigators need to ensure that the experimental designs are optimal and the studies properly executed. The workshop participants identified methodological issues that may confound study results and interpretation. Scientifically sound and useful options for dealing with these issues were discussed. The resulting guidance is presented in this document with a brief rationale. The guidance is specific to soy clinical research and does not address nonsoy-related factors that should also be considered in designing and reporting clinical studies. This guidance may be used by investigators, journal editors, study sponsors, and protocol reviewers for a variety of purposes, including designing and implementing trials, reporting results, and interpreting published epidemiological and clinical studies.

The effect of genistein aglycone on cancer and cancer risk: a review of in vitro, preclinical, and clinical studies

In Asian epidemiological studies, health benefits, including reduced incidence of breast and prostate cancers, are attributed to soy food and isoflavone consumption. The recent increased intake of soy foods and supplements in the American diet has raised concerns about the possible estrogen-like effects of natural isoflavones and possible promotion or propagation of estrogen-sensitive cancers. These concerns are primarily based on in vitro and rodent data which suggest that genistein aglycone can stimulate tumor cell proliferation and growth in mice having deficient immune systems. In contrast, a recent nested case-control study and meta-analysis of numerous epidemiological studies show an inverse correlation between genistein intake and breast cancer risk. Furthermore, clinical studies in osteopenic and osteoporotic, postmenopausal women support the breast and uterine safety of purified naturally derived genistein administered for up to 3 years. In this review, we summarize the in vitro, preclinical and clinical evidence for the safety of natural genistein.

Evidence that low-dose, long-term genistein treatment inhibits oestradiol-stimulated growth in MCF-7 cells by down-regulation of the PI3-kinase/Akt signalling pathway

The reduced incidence of breast cancer in certain Eastern countries has been attributed to high soy diets although this evidence is simply epidemiological. One of the major constituents of soy is genistein, but paradoxically this phytoestrogen binds to oestrogen receptors and stimulates growth at concentrations that would be achieved by a high soy diet, but inhibits growth at high experimental concentrations. To determine the effects of low-dose, long-term genistein exposure we have cultured MCF-7 breast cancer cells in 10 nM genistein for 10-12 weeks and investigated whether or not this long-term genistein treatment (LTGT) altered the expression of oestrogen receptor alpha (ERalpha) and the activity of the PI3-K/Akt signalling pathway. This is known to be pivotal in the signalling of mitogens such as oestradiol (E(2)), insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF). LTGT significantly reduced the growth promoting effects of E(2) and increased the dose-dependent growth-inhibitory effect of the PI3-K inhibitor, LY 294002, compared to untreated control MCF-7 cells. This was associated with a significant decreased protein expression of total Akt and phosphorylated Akt but not ERalpha. Rapamycin, an inhibitor of one of the down-stream targets of Akt, mammalian target of rapamycin (mTOR), also dose-dependently inhibited growth but the response to this drug was similar in LTGT and control MCF-7 cells. The protein expression of liver receptor homologue-1 (LRH1), an orphan nuclear receptor implicated in tumourigenesis was not affected by LTGT. The results show that LTGT results in a down-regulation of the PI3-K/Akt signalling pathway and may be a mechanism through which genistein could offer protection against breast cancer.

Modulation of CXCR4, CXCL12, and Tumor Cell Invasion Potential In Vitro by Phytochemicals

CXCR4 is a chemokine receptor frequently overexpressed on primary tumor cells. Organs to which these cancers metastasize secrete CXCL12, the unique ligand for CXCR4, which stimulates invasion and metastasis to these sites. Similar to our previous work with the chemoprotective phytochemical, 3,3′-diindolylmethane (DIM), we show here that genistein also downregulates CXCR4 and CXCL12 and subsequently lowers the migratory and invasive potentials of breast and ovarian cancer cells. Moreover, genistein and DIM elicit a significantly greater cumulative effect in lowering CXCR4 and CXCL12 levels than either compound alone. Our data suggest a novel mechanism for the protective effects of phytochemicals against cancer progression and indicate that in combination, these compounds may prove even more efficacious.

Soy isoflavones and immunity

The amount of soy products consumed in Japan is much greater than that in Western countries. Recent evidence indicates that soy isoflavones play a beneficial role in obesity, cancer, osteoporosis, and cardiovascular disease. The soybean isoflavone genistein is present at high levels in soy products. Genistein is structurally similar to 17beta-estradiol (E2), and genistein has been suggested to be act as E2 or an antagonist against E2. Genistein suppresses antigen-specific immune response in vivo and lymphocyte proliferation response in vitro. However, genistein enhances the cytotoxic response mediated by NK and cytotoxic T cells and the cytokine production from T cells. Thus, the effect of genistein on immunity is immune cell-dependent. Due to its unique effect on immune function, genistein has been used for the treatment of the diseases in animal models and it has been found that genistein inhibits allergic inflammatory responses. In this review, we summarize current studies related to the effect of isoflavone genistein on the immune system.

Tea polyphenols and their roles in cancer prevention and chemotherapy

Many plant-derived, dietary polyphenols have been studied for their chemopreventive and chemotherapeutic properties against human cancers, including green tea polyphenols, genistein (found in soy), apigenin (celery, parsley), luteolin (broccoli), quercetin (onions), kaempferol (broccoli, grapefruits), curcumin (turmeric), etc. The more we understand their involved molecular mechanisms and cellular targets, the better we could utilize these “natural gifts” for the prevention and treatment of human cancer. Furthermore, better understanding of their structure-activity relationships will guide synthesis of analog compounds with improved bio-availability, stability, potency and specificity. This review focuses on green tea polyphenols and seeks to summarize several reported biological effects of tea polyphenols in human cancer systems, highlight the molecular targets and pathways identified, and discuss the role of tea polyphenols in the prevention and treatment of human cancer. The review also briefly describes several other dietary polyphenols and their biological effects on cancer prevention and chemotherapy.

Extended treatment with physiologic concentrations of dietary phytochemicals results in altered gene expression, reduced growth, and apoptosis of cancer cells

Dietary phytochemicals exhibit chemopreventive potential in vivo through persistent low-dose exposures, whereas mechanistic in vitro studies with these agents generally use a high-dose single treatment. Because the latter approach is not representative of an in vivo steady state, we investigated antitumor activity of curcumin, 3,3'-diindolylmethane (DIM), epigallocatechin gallate (EGCG), genistein, or indole-3-carbinol (I3C) in breast cancer MDA-MB-231 cells, exposed in long-term culture to low concentrations, achievable in vivo. Curcumin and EGCG increased cell doubling time. Curcumin, EGCG, and I3C inhibited clonogenic growth by 55% to 60% and induced 1.5- to 2-fold higher levels of the basal caspase-3/7 activity. No changes in expression of cell cycle-related proteins or survivin were found; however, I3C reduced epidermal growth factor receptor expression, contributing to apoptosis. Because some phytochemicals are shown to inhibit DNA and histone modification, modulation of expression by the agents in a set of genes (cadherin-11, p21Cip1, urokinase-type plasminogen activator, and interleukin-6) was compared with changes induced by inhibitors of DNA methylation or histone deacetylation. The phytochemicals modified protein and/or RNA expression of these genes, with EGCG eliciting the least and DIM the most changes in gene expression. DIM and curcumin decreased cadherin-11 and increased urokinase-type plasminogen activator levels correlated with increased cell motility. Curcumin, DIM, EGCG, and genistein reduced cell sensitivity to radiation-induced DNA damage without affecting DNA repair. This model has revealed that apoptosis and not arrest is likely to be responsible for growth inhibition. It also implicated new molecular targets and activities of the agents under conditions relevant to human exposure.

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.

Decreased 7,12-dimethylbenz[a]anthracene-induced carcinogenesis coincides with the induction of antitumor immunities in adult female B6C3F1 mice pretreated with genistein

The objective of this study was to determine if genistein (GEN) modulation of the immune responses might contribute to the increased host resistances to tumors. A time-course study was performed in adult female B6C3F1 mice that had been exposed to GEN for 1-4 weeks at the dose level of 20 mg/kg by gavage. A significant increase in ex vivo cytotoxic T lymphocyte (CTL) activity was observed in the periods of 2 weeks and 4 weeks. Moreover, increased activities of CTLs were associated with a decrease in the percentage of CD4(+)CD25(+) T cells and an increase in the production of interferon-gamma and activation of STAT1 (signal transducer and activator of transcription 1) and STAT4. Additionally, exposure of mice to GEN increased the activities of in vivo CTLs. An increased activity of natural killer (NK) cells was also observed. Further study in the B16F10 tumor model suggested that GEN-mediated enhancement in host resistance to B16F10 tumor was partially related to its potentiating effect on NK cells. Finally, 7,12-dimethylbenz[a]anthracene (DMBA)-induced tumor model was employed to determine the chemopreventive effect of oral GEN treatment. Mice pretreated with GEN for 2 weeks by gavage, the time when an enhanced CTL activity had been produced, had a decreased susceptibility toward DMBA-mediated carcinogenesis, while treatment with GEN after tumor induction conferred no protection. In conclusion, pretreatment with GEN by gavage could enhance host resistances to the B16F10 tumor and DMBA-induced carcinogenesis, suggesting that GEN modulation of immune response was, at least partially, responsible for the antitumor effect of this compound.

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.

Genistein modulates the effects of parathyroid hormone in human osteoblastic SaOS-2 cells

Genistein and parathyroid hormone (PTH) are anabolic agents that stimulate bone formation through their direct actions in osteoblastic cells. In the present study, we aimed to determinewhether genistein modulates the actions of PTH in human osteoblastic SaOS-2 cells in an oestrogen-depleted condition. The present results showed that genistein (10−8to 10−6m) induced alkaline phosphatase (ALP) activity and osteoprotegrin (OPG) expression in SaOS-2 cells in a dose-dependent manner. These effects could be completely abolished by co-treatment with oestrogen antagonist ICI 182780 (7α-[9-[(4,4,5,5,5-pentafluoropentyl)sulfonyl]nonyl]-estra-1,3,5(10)-triene-3,17β-diol). Genistein (at 1μm) could stimulate the mRNA expression of receptor activator of NF-κB ligand (RANKL). As OPG and RANKL are known to modulate osteoclastogenesis, the ability of genistein to modulate OPG and RANKL expression in SaOS-2 cells suggested that it might modulate osteoclastogenesis through its direct actions on osteoblastic cells. PTH (at 10nm) stimulated ALP activity, induced RANKL mRNA expression and suppressed OPG mRNA expression in SaOS-2 cells, confirming its bi-directional effects on osteoblastic cells. Pre-treatment of SaOS-2 cells with genistein andoestrogen not only enhanced PTH-induced ALP activity, but also attenuated PTH up regulation ofRANKL mRNA expression and PTH down regulation of OPG mRNA expression. Taken together, the present study provides the first evidence that genistein could modulate the actions of PTH in human osteoblastic SaOS-2 cells in an oestrogen-depleted condition.

Changes in gene expressions elicited by physiological concentrations of genistein on human endometrial cancer cells

The incidence of hormone-related diseases such as prostatic, breast, ovarian, and endometrial cancer is lower in Asian populations compared to Western countries. High consumption of soybean products that are rich in phytoestrogens, predominantly genistein, is postulated to be responsible for the lower incidence of hormone-related disease, although the mechanism through which this effect might be mediated is unclear. In this study, microarray analysis was used to identify the changes in gene expression elicited by treatment of the human endometrial cancer cell line, Ishikawa, with genistein at both physiologically achievable and supraphysiological concentrations. Genistein treatment at 5 microM concentration induced multiple changes in gene expression including some implicated in oncogenesis. In contrast, treatment with a supraphysiological concentration of genistein predominantly activated stress response genes and showed very limited overlap with the genes regulated at lower concentrations. Of the genes regulated by genistein, 9.3% were also regulated by 17beta-estradiol suggesting that genistein exerts its response via the estrogen pathway. These results indicate that at physiological concentrations, genistein is able to elicit pleiotropic effects on a variety of pathways believed to be involved in tumorigenesis. Supraphysiological concentrations of genistein, such as those used in many previous studies, elicit changes in gene expression that are unlikely to occur in vivo.

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.

Soy isoflavone glycitein protects against beta amyloid-induced toxicity and oxidative stress in transgenic Caenorhabditis elegans

BACKGROUND

Epidemiological studies have associated estrogen replacement therapy with a lower risk of developing Alzheimer's disease, but a higher risk of developing breast cancer and certain cardiovascular disorders. The neuroprotective effect of estrogen prompted us to determine potential therapeutic impact of soy-derived estrogenic compounds. Transgenic C. elegans, that express human beta amyloid (Abeta), were fed with soy derived isoflavones genistein, daidzein and glycitein (100 microg/ml) and then examined for Abeta-induced paralysis and the levels of reactive oxygen species.

RESULTS

Among the three compounds tested, only glycitein alleviated Abeta expression-induced paralysis in the transgenic C. elegans. This activity of glycitein correlated with a reduced level of hydrogen peroxide in the transgenic C. elegans. In vitro scavenging effects of glycitein on three types of reactive oxygen species confirmed its antioxidant properties. Furthermore, the transgenic C. elegans fed with glycitein exhibited reduced formation of beta amyloid.

CONCLUSION

These findings suggest that a specific soy isoflavone glycitein may suppress Abeta toxicity through combined antioxidative activity and inhibition of Abeta deposition, thus may have therapeutic potential for prevention of Abeta associated neurodegenerative disorders.

Regulation of HMG-CoA reductase in MCF-7 cells by genistein, EPA, and DHA, alone and in combination with mevastatin

We investigated the regulation of HMG-CoA reductase in MCF-7 human breast cancer cells by genistein, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). All three compounds down-regulated reductase activity, primarily through post-transcriptional effects. In mevastatin-treated cells, only genistein and DHA abrogated the induction of reductase activity caused by this competitive inhibitor. Diets rich in soy isoflavones and fish oils, therefore, may exert anti-cancer effects through the inhibition of mevalonate synthesis in the breast. Genistein and DHA, in particular, may augment the efficacy of statins, increasing the potential for use of these drugs in adjuvant therapy for breast cancer.

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.

Dietary factors and the regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase: Implications for breast cancer development

A role for mevalonate in cancer development has long been suggested by findings that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity is elevated in malignant cells. Increased synthesis mevalonate and mevalonate-derived nonsterol isoprenoids supports increased cell proliferation through the activation of growth-regulatory proteins and oncoproteins, and by promoting DNA synthesis. We have recently shown that mevalonate promotes the growth of human breast cancer cells both in culture and as tumors grown in nude mice. Inhibition mevalonate synthesis, therefore, may be an effective strategy to impair the growth of malignant breast cells. Several dietary compounds with known anti-cancer effects are also reported to inhibit HMG-CoA reductase activity. Here, we review evidence suggesting that inhibition of mevalonate synthesis may mediate the protective effects of cholesterol, plant isoprenoids, genistein, and long-chain n-3 polyunsaturated fatty acids (PUFAs) on experimental breast cancer.

Dietary resveratrol does not affect intestinal tumorigenesis in Apc(Min/+) mice

To determine its effect on intestinal tumorigenesis and the protumorigenic COX pathway in Apc(Min/+) mice, resveratrol was administered as a powdered admixture in the diet at 0, 4, 20, or 90 mg/kg body weight for 7 wk. In two separate experiments, resveratrol did not affect intestinal tumor load. It was stable in the diet under experimental conditions, circulated in the plasma as the glucuronide-conjugated form and reached the tumors as evidenced by significant decreases in PGE2 levels. However, immunohistochemical staining of intestinal tumors revealed no changes in COX-2 expression. This study demonstrates that resveratrol consumed ad libitum in the diet, does not modify tumorigenesis in Apc(Min/+) mice.

Clinical characteristics and pharmacokinetics of purified soy isoflavones: multiple-dose administration to men with prostate neoplasia

A phase I clinical trial was conducted to determine the safety, pharmacokinetic parameters, and efficacy of orally administered isoflavones (genistein and daidzein, potential cancer chemotherapeutic agents) over a 3-mo period in men with prostate neoplasia. Twenty men, ages 40 and above, with stage B, C, or D adenocarcinoma of the prostate were treated with a multiple-dose regimen of a soy isoflavone formulation (delivering approximately 300 or 600 mg/day genistein and half this much daidzein) for 84 days. The delivered dose of isoflavones was more than 10-fold higher than that typically taken by prostate cancer patients. In men with prostate cancer, relatively minor side effects of chronic isoflavone treatment were observed including some estrogenic effects (breast changes, increased frequency of hot flashes). Serum dehydroepiandrosterone was decreased by 31.7% (P = 0.0004) at the end of treatment. Except for those subjects whose prostate-specific antigen (PSA) values were below 0.4 ng/ml, subjects had a history of increasing PSA levels prior to the trial. This increase continued during the trial both while on soy isoflavones and after treatment was discontinued. On average the rate of rise accelerated after soy isoflavones were discontinued, but that difference did not attain statistical significance. Genistein and daidzein were rapidly cleared from plasma and excreted in urine. Pharmacokinetic data for chronic dose administration were similar to single-dose administration for the isoflavones investigated except that we observed slightly longer circulation time for daidzein.

A pilot clinical study of short-term isoflavone supplements in breast cancer patients

Many laboratory-based studies have shown that soy can suppress breast cancer proliferation. However, given the recent controversy generated by animal experiments that soy may under certain conditions stimulate breast cancer growth, we decided to carry out a pilot clinical trial in order to elucidate any interaction(s) between short-term isoflavone supplement administration and breast cancer growth. After a core-needle biopsy established the diagnosis of breast cancer, 17 patients were administered soy isoflavone tablets for two weeks. This surgically based study provided the unique opportunity to make objective observations based on human breast cancer tissues and blood obtained prior to and after isoflavone supplement treatment in the same patient. Twenty-six historical control cases with similar characteristics to the experimental patients were selected for comparison. We observed that the apoptosis/mitosis ratios in isoflavone-treated cancer specimens were not significantly different from those of control untreated cancer specimens. Furthermore, there appeared to be a statistically nonsignificant trend towards cancer growth inhibition in the isoflavone treatment group, as manifested by higher apoptosis/mitosis ratios compared with those from the control untreated group. Ex vivo/in vitro assays using serum from breast cancer patients prior to and at the conclusion of soy treatment reveal no significant proliferative changes on both breast cancer cells and endothelial cells. We concluded that the effect of soy on breast cancer deserves further studies in larger clinical trials.

Anticancer therapeutic potential of soy isoflavone, genistein

Genistein (4'5, 7-trihydroxyisoflavone) occurs as a glycoside (genistin) in the plant family Leguminosae, which includes the soybean (Glycine max). A significant correlation between the serum/plasma level of genistein and the incidence of gender-based cancers in Asian, European and American populations suggests that genistein may reduce the risk of tumor formation. Other evidence includes the mechanism of action of genistein in normal and cancer cells. Genistein inhibits protein tyrosine kinase (PTK), which is involved in phosphorylation of tyrosyl residues of membrane-bound receptors leading to signal transduction, and it inhibits topoisomerase II, which participates in DNA replication, transcription and repair. By blocking the activities of PTK, topoisomerase II and matrix metalloprotein (MMP9) and by down-regulating the expression of about 11 genes, including that of vascular endothelial growth factor (VEGF), genistein can arrest cell growth and proliferation, cell cycle at G2/M, invasion and angiogenesis. Furthermore, genistein can alter the expression of gangliosides and other carbohydrate antigens to facilitate their immune recognition. Genistein acts synergistically with drugs such as tamoxifen, cisplatin, 1,3-bis 2-chloroethyl-1-nitrosourea (BCNU), dexamethasone, daunorubicin and tiazofurin, and with bioflavonoid food supplements such as quercetin, green-tea catechins and black-tea thearubigins. Genistein can augment the efficacy of radiation for breast and prostate carcinomas. Because it increases melanin production and tyrosinase activity, genistein can protect melanocytes of the skin of Caucasians from UV-B radiation-induced melanoma. Genistein-induced antigenic alteration has the potential for improving active specific immunotherapy of melanoma and carcinomas. When conjugated to B43 monoclonal antibody, genistein becomes a tool for passive immunotherapy to target B-lineage leukemias that overexpress the target antigen CD19. Genistein is also conjugated to recombinant EGF to target cancers overexpressing the EGF receptor. Although genistein has many potentially therapeutic actions against cancer, its biphasic bioactivity (inhibitory at high concentrations and activating at low concentrations) requires caution in determining therapeutic doses of genistein alone or in combination with chemotherapy, radiation therapy, and/or immunotherapies. Of the more than 4500 genistein studies in peer-reviewed primary publications, almost one fifth pertain to its antitumor capabilities and more than 400 describe its mechanism of action in normal and malignant human and animal cells, animal models, in vitro experiments, or phase I/II clinical trials. Several biotechnological firms in Japan, Australia and in the United States (e.g., Nutrilite) manufacture genistein as a natural supplement under quality controlled and assured conditions.

The soy isoflavone genistein decreases adipose deposition in mice

Adipose tissue is responsive to estrogen and expresses both estrogen receptor alpha and beta. To test the hypothesis that the estrogenic soy isoflavone genistein can have effects on adipose tissue, juvenile or adult C57/BL6 mice were ovariectomized and given daily injections of vehicle, 17beta-estradiol (5 microg/kg.d) or genistein (8-200 mg/kg.d) sc for 21-28 d. To test effects of dietary genistein, 25- to 27-d-old mice were fed diets containing 0-1500 parts per million (ppm) genistein for 12 d. Mice were killed and fat pads weighed. Parametrial fat pads were used for morphometric and Northern analysis. Genistein injections decreased adipose weight and adipocyte circumference at higher doses; effects in adult and juvenile mice were similar. Genistein decreased lipoprotein lipase mRNA, which may be a critical aspect of its adipose effects. Juveniles fed 500-1500 ppm dietary genistein had dose-responsive decreases in fat pad weights of 37-57%, compared with controls; 300 ppm genistein did not cause decreases. Genistein doses of 300, 500, 1000, and 1500 ppm produced serum genistein concentrations of 1.02 +/- 0.14 microM, 1.79 +/- 0.32 microM, 2.55 +/- 0.18 microM, and 3.81 +/- 0.39 microM, respectively. These results indicate dietary genistein at 500-1500 ppm produces antilipogenic effects in mice at serum levels that humans are realistically exposed to.

Effect of Dietary Constituents With Chemopreventive Potential on Adduct Formation of a Low Dose of the Heterocyclic Amines PhIP and IQ and Phase II Hepatic Enzymes

We conducted a study to evaluate dietary chemopreventive strategies to reduce genotoxic effects of the carcinogens 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). PhIP and IQ are heterocyclic amines (HCAs) that are found in cooked meat and may be risk factors for cancer. Typical chemoprevention studies have used carcinogen doses many thousand-fold higher than usual human daily intake. Therefore, we administered a low dose of [14C]PhIP and [3H]IQ and utilized accelerator mass spectrometry to quantify PhIP adducts in the liver, colon, prostate, and blood plasma and IQ adducts in the liver and blood plasma with high sensitivity. Diets supplemented with phenethylisothiocyanate (PEITC), genistein, chlorophyllin, or lycopene were evaluated for their ability to decrease adduct formation of [14C]PhIP and [3H]IQ in rats. We also examined the effect of treatments on the activity of the phase II detoxification enzymes glutathione S-transferase (GST), UDP-glucuronyltransferase (UGT), phenol sulfotransferase (SULT) and quinone reductase (QR). PEITC and chlorophyllin significantly decreased PhIP-DNA adduct levels in all tissues examined, which was reflected by similar changes in PhIP binding to albumin in the blood. In contrast, genistein and lycopene tended to increase PhIP adduct levels. The treatments did not significantly alter the level of IQ-DNA or -protein adducts in the liver. With the exception of lycopene, the treatments had some effect on the activity of one or more hepatic phase II detoxification enzymes. We conclude that PEITC and chlorophyllin are protective of PhIP-induced genotoxicity after a low exposure dose of carcinogen, possibly through modification of HCA metabolism.

Inhibition of human breast cancer growth by GCP (genistein combined polysaccharide) in xenogeneic athymic mice: involvement of genistein biotransformation by beta-glucuronidase from tumor tissues

The role of beta-glucuronidase in genistein biotransformation was investigated in a human breast cancer MDA-MB-231 xenogeneic athymic mouse model. Genistein combined polysaccharide (GCP), a genistein aglycone rich functional food supplement was used in these experiments. Tumor-bearing mice were subjected to oral administration of GCP for 28 days. GCP treatment significantly inhibited tumor growth. Induction of apoptosis by GCP treatment was related to activation of cleavage of poly(ADP-ribose)polymerase, induction of the p21 protein expression and reduction of cyclin B1 expression in the tumor tissues. Genistein exists as a glucuronide conjugate in normal organ tissues, and the conjugated genistein lacks the physiological activity of the aglycone. Tumor tissues contain large amounts of beta-glucuronidase, the enzyme that converts the genistein beta-glucuronide conjugate into genistein aglycone. The resulting genistein aglycone exerts its chemopreventive activities, including the induction of apoptosis in tumor tissues, and, finally, leads to tumor growth inhibition.

Phytoestrogens and breast cancer

The role of phytoestrogens and consumption of phytoestrogen-rich foods such as soy containing isoflavones and whole grain products with lignans for the prevention of breast cancer is reviewed. It is concluded that soy-containing diet in adult women is not or only slightly protective with regard to breast cancer, but that it may be beneficial if consumed in early life before puberty or during adolescence supporting results of immigrant and epidemiological studies. No negative effects of soy on breast cancer have been observed. On the other hand, a diet low in lignans, resulting in a low plasma enterolactone concentration, increases risk both in a case-control and a prospective study, but some controversial results have also been obtained. Some of these results may be explained by the fact that the determinants of plasma or urinary enterolactone concentration are very different in different countries. In Scandinavia, the main determinants are whole grain cereal food, vegetables and berries. Whether the protective effect is caused by the phytoestrogens in the diet or whether they are only biomarkers of a healthy diet has not been established.