Molecular effects of the isoflavonoid genistein in prostate cancer

Differences in diet have been proposed to be at least partially responsible for the low rate of prostate cancer in Asian populations compared with men in Western countries. One of the compounds that occurs in a greater quantity in the Eastern diet is genistein, an isoflavonoid found in high concentrations in serum after ingestion of soy-rich foods. Extensive molecular studies have been performed to determine its potential health benefits. The mechanism of action of genistein is complex and includes several cellular pathways. In addition to its estrogenic and/or antiestrogenic activities, genistein has been reported to inhibit steroidogenesis and block several protein tyrosine kinases, including epidermal growth factor receptor and src tyrosine kinases. Moreover, it arrests the cell cycle, induces apoptosis, and has antiangiogenic and antimetastatic properties and antioxidant activity. Herein, we review the current literature on the molecular mechanisms of genistein in relation to its effects on prostate cancer cells.

Oral administration of soy-derived genistin suppresses lipopolysaccharide-induced acute liver inflammation but does not induce thymic atrophy in the rat

Genistein, the principal isoflavone present in soy, has been identified as a protein tyrosine kinase (PTK) inhibitor that has in vitro anti-inflammatory effects. Whether genistein has in vivo anti-inflammatory effects remains unknown yet. Injecting or feeding rats with the unconjugated form of genistein (aglycone) results in decreased thymic weight and lymphocytopenia. However, 95-99% of genistein is present as the conjugated form genistin (genistein glycoside) in soy or soy-derived products. This study was undertaken to reveal whether genistin, as well as genistein, has anti-inflammatory effects in vivo. After oral administration of equimolar genistein (namely 7.4 or 74 micromol/dose) at daily doses of 2.0 or 20 mg/kg, or genistin at daily doses of 3.2 or 32 mg/kg for 3 days to male rats, both aglycone and glycoside suppressed the production of lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6 in both from the liver and in the sera. Aglycone induced thymic atrophy while glycoside did not. In vitro preincubation of liver slices from naïve rat with genistein aglycone or glycoside suppressed LPS-induced TNF-alpha production in a dose-dependent manner. Taken together, both in vivo and in vitro administration of genistin and genistein suppressed LPS-induced liver pro-inflammatory cytokine production. However, equimolar oral administration of genistin did not induce thymus atrophy. Further investigation in long-term isoflavone intake is required especially among neonates. The results suggest that the safety evaluation of the consumption of isoflavone should be based on isoflavone glycoside but not aglycone.

Soy isoflavones alter expression of genes associated with cancer progression, including interleukin-8, in androgen-independent PC-3 human prostate cancer cells

High consumption of soy isoflavones in Asian diets has been correlated with a lower incidence of clinically important cases of prostate cancer. The chemopreventive properties of these diets may result from an interaction of several types of isoflavones, including genistein and daidzein. The present study investigated the effects of a soy isoflavone concentrate (ISF) on growth and gene expression profiles of PC-3 human prostate cancer cells. Trypan blue exclusion and [3H]-thymidine incorporation assays showed that ISF decreased cell viability and caused a dose-dependent inhibition of DNA synthesis, respectively, with 50% inhibition (IC50) of DNA synthesis at 52 mg/L (P = 0.05). The glucoside conjugates of genistein and daidzein in ISF were converted to bioactive free aglycones in cell culture in association with the inhibition of DNA synthesis. Flow cytometry and Western immunoblot analyses showed that ISF at 200 mg/L caused an accumulation of cells in the G2/M phase of the cell cycle (P < 0.05) and decreased cyclin A by 20% (P < 0.05), respectively. The effect of ISF on the gene expression profile of PC-3 cells was analyzed using Affymetrix oligonucleotide DNA microarrays that interrogate approximately 17,000 human genes. Of the 75 genes altered by ISF, 28 were upregulated and 47 were downregulated (P < 0.05). Further analysis showed that IL-8, matrix metalloproteinase 13, inhibin beta A, follistatin, and fibronectin mRNA levels were significantly reduced, whereas the expression of p21(CIP1), a major cell cycle inhibitory protein, was increased. The effects of ISF on the expression of IL-8 and p21(CIP1) mRNA and protein were validated at high and low ISF concentrations. Our data show that ISF inhibits the growth of PC-3 cells through modulation of cell cycle progression and the expression of genes involved in cell cycle regulation, metastasis, and angiogenesis.

Genistein replacement therapy on endothelial dysfunction and bone loss in bilateral ovariectomized rats

The objective of this study is to examine roles of genistein in postmenopausal induced-endothelial dysfunction and bone loss, the ovariectomized (OVX) rat model was used. The animals were divided into three groups of sham treated with vehicle (DMSO 100 microl/day; Sham(veh)), OVX treated with vehicle (OVX(veh)) and OVX treated with genistein (0.25 mg/kg/day; OVX(gen)). At 3 and 7 weeks after the surgery, endothelial dysfunction in mesenteric microcirculation of each group was determined by using intravital fluorescence microscopy and analyzed with digital image software. The parameters of bone mass density (BMD) and bone formation marker were represented by percentage of ash/dry matter and osteocalcin activity (using radioimmunoassay (RIA)), respectively. Mean arterial pressures (MAP) in OVX(veh) groups were significantly increased compared to their aged-matched sham groups (p<0.05). Interestingly, the treatment of genistein could significantly attenuate this abnormality (p<0.001). Besides, it could increase the vascular response to acetylcholine (Ach; 10(-6) M) significantly compared to OVX-rats (p<0.05). Moreover, BMD and osteocalcin activity were significantly increased in Ovx(gen) as well. Therefore, our findings suggested that genistein supplementation could effectively prevent endothelial dysfunction and bone loss in OVX-rat model.

The phytoestrogen biochaninA weakens acute cardiac allograft rejection without affecting the reproductive system

BACKGROUND

Since the two estrogen receptor isoforms ERalpha and ERbeta have been discovered it is unclear by which receptor immunomodulating or feminizing effects are mediated. In this study, the effects of the two selective ERalpha- and ERbeta-agonists ethinylestradiol and biochaninA, respectively, on acute cardiac allograft rejection, uterus growth, vascular adhesion molecule and MHC-II expression were investigated and verified using in vitro cell culture.

METHODS

Heterotopic Lewis to ovarectomized F344 cardiac transplantations were performed. The study groups received supplemental biochaninA or ethinylestradiol, the control group received no treatment. Grafts and uteri were harvested on the fifth postoperative day and blood was taken for hormone plasma level quantifications. Purified Lewis aortic endothelial cell cultures were pre-treated with biochaninA or ethinylestradiol and stimulated with TNF-alpha or IFN-gamma for quantification of ICAM-1/VCAM-1 and MHC-II expression. Endothelium-lymphocyte adhesion assays were performed using purified F344 lymphocytes.

RESULTS

Both biochaninA and ethinylestradiol treatment significantly reduced graft mononuclear infiltration of CD8(+) and ED1(+) cells and markedly reduced ISHLT grading compared to untreated controls. Either agent significantly inhibited lymphocyte adhesion, endothelial VCAM-1 upregulation during graft rejection and during TNF-alpha-stimulation in vitro, whereas no effect was observed for ICAM-1 upregulation. BiochaninA but not ethinylestradiol significantly reduced endothelial MHC-II upregulation in vivo and in vitro. Only ethinylestradiol treatment strongly affected uterus growth in ovarectomized recipients.

CONCLUSIONS

Only the treatment with the phytoestrogen biochaninA reduced endothelial MHC-II expression in vivo and in vitro and weakened allograft rejection without affecting the reproductive system. Supplemental phytoestrogens may therefore provide further benefits in the clinical setting.

Chemoprevention of breast cancer, proteomic discovery of genistein action in the rat mammary gland

Genistein, the primary isoflavone component of soy, consumed in the diet during the prepubertal period only, and the combined prepubertal and adult periods, suppresses chemically induced mammary cancer in rats. Gestational or adult-only exposures do not provide protection. An inverse relation exists between cancer susceptibility and mammary gland differentiation. The current study used proteomic technology to investigate genistein mechanisms of action as related to programming against chemically induced mammary cancer. Rats were injected subcutaneously with 500 microg genistein/g body weight on d 16, 18, and 20 postpartum. At d 21, mammary glands were subjected to 2-dimensional polyacrylamide gel electrophoresis. After gel scanning, image analysis, and MS, 6 proteins were determined to be differentially regulated and identified. One protein, GTP-cyclohydrolase 1 (GTP-CH1), was confirmed as being significantly upregulated at d 21 by immunoblot analysis. Investigation of downstream signaling from GTP-CH1 showed that tyrosine hydroxylase was upregulated and vascular endothelial growth factor receptor 2 (VEGFR2) was downregulated in the mammary glands of 50-d-old rats treated with genistein in the prepubertal period. This and previous work suggest that early prepubertal exposure to genistein enhances cell proliferation by upregulating GTP-CH1 and the epidermal growth factor (EGF)-signaling pathway, and hence cell differentiation and gland maturation. This unique developmental maturation leads to a new biochemical blueprint, whereby the cells have reduced EGF signaling and VEGFR2, which renders the mature mammary gland less proliferative and less susceptible to cancer. This study demonstrated the usefulness of proteomics for the discovery of novel pathways that may be involved in cancer prevention.

Genistein potentiates the growth inhibitory effects of 1,25-dihydroxyvitamin D3 in DU145 human prostate cancer cells: role of the direct inhibition of CYP24 enzyme activity

In a search for improved therapies for prostate cancer, we investigated the effect of genistein in combination with 1alpha-25-dihydroxyvitamin D3 [1,25(OH)2D3], on the growth of DU145 human prostate cancer cells. DU145 cells were very resistant to the growth inhibitory action of 1,25(OH)2D3 or genistein when administered individually. However, the combination caused a significant growth inhibition seen at lower concentrations of both agents. 1,25(OH)2D3 induces the expression of the CYP24 gene, which codes for the enzyme that initiates the catabolism of 1,25(OH)2D3. We showed for the first time that genistein at low doses (50-100 nM) directly inhibited CYP24 at the enzyme level. Addition of genistein to mitochondrial preparations inhibited CYP24 enzyme activity in a noncompetitive manner. CYP24 inhibition by genistein increased the half-life of 1,25(OH)2D3 thereby augmenting the homologous up-regulation of the vitamin D receptor (VDR) both at the mRNA and protein levels. Genistein co-treatment enhanced 1,25(OH)2D3-mediated transactivation of the vitamin D responsive reporters OC-Luc and OP-Luc transfected into DU145 cells. Consistent with the growth inhibition due to the combination treatment, significant changes in the expression of genes involved in growth arrest and apoptosis were seen. We conclude that genistein potentiates the antiproliferative actions of 1,25(OH)2D3 in DU145 cells by two mechanisms: (i) an increase in the half-life of 1,25(OH)2D3 due to the direct inhibition of CYP24 enzyme activity and (ii) an amplification of the homologous up-regulation of VDR. Together these two effects lead to a substantial enhancement of the cellular responses to the growth inhibitory and pro-apoptotic signaling by 1,25(OH)2D3.

Genistein induces apoptosis in T lymphoma cells via mitochondrial damage

The soy isoflavone genistein has been identified as having antiproliferative and apoptotic effects on various malignant cell types derived from solid tumors. Because little information regarding the effect of genistein on hematopoietic malignancies is available, we undertook this study of T-cell lymphomas. We tested the effect of genistein on murine T-cell lines derived from thymic lymphomas induced by an oncogenic murine leukemia virus. When T lymphoma cells were treated with genistein concentrations of 15 microM and greater, it was observed that the percentage of viable cells was significantly reduced in a dose- and time-dependent manner. The observed cell killing was found to be the result of apoptosis as detected by flow cytometric analysis of cells stained with annexin V and propidium iodide and assays for caspase-3 activation and DNA fragmentation. Cell staining with the mitochondrial specific dye JC-1 and detection of caspase-9 activation revealed that genistein produced mitochondrial depolarization as an early step in the induction of apoptosis. Bongkrekic acid inhibition of mitochondrial depolarization identified the mitochondria permeability transition pore (PTP) as a potential target of genistein activity. These results indicate that the induction of apoptosis by pharmacological concentrations of genistein in T lymphoma cells occurs via mitochondrial damage with the involvement of the PTP.

Genistein inhibited retinal neovascularization and expression of vascular endothelial growth factor and hypoxia inducible factor 1alpha in a mouse model of oxygen-induced retinopathy

The effects of genistein on neovascularization, vascular endothelial growth factor (VEGF), and hypoxia inducible factor 1alpha (HIF1alpha) protein expression in a mouse model of oxygen-induced retinopathy were studied. The model of oxygen-induced retinal neovascularization was induced in newborn C57BL/6 mice by exposing 7-day-old mice to 75% oxygen for 5 days and then housing them in room air (relative hypoxia). Retinopathy was assessed by quantitation of vascular cell nuclei anterior to inner limiting membrane. Judged by relative fluorescence using a confocal scanning laser microscope coupled to a computer, VEGF and HIF1alpha protein expression were investigated. Genistein markedly inhibited the numbers of nuclei protruding above the inner limiting membrane under relative hypoxia conditions. The levels of nuclei numbers were suppressed by 50, 100, and 200 mg/kg body weight /day genistein to 87.4%, 72.0%, and 59.4%, respectively, compared to that untreated with genistein. VEGF protein was constitutively expressed in the preretinal area under normoxia conditions. Genistein markedly inhibited relative-hypoxia-elicited VEGF expression elevation in a dose-dependent manner. HIF1alpha expression was also observed in normoxia conditions. There was a 2.4-fold induction in preretinal HIF1alpha expression in oxygen-reared animals when compared to room-air-reared animals. Genistein dose-dependently suppressed HIF1alpha protein expression. These results indicated that the inhibition of VEGF and HIF1alpha protein expression by genistein may partly account for its effect on retinal neovascularization in vivo, and genistein could be an effective agent in the prevention and treatment of ocular neovascularization.

Regulation of gene expression and inhibition of experimental prostate cancer bone metastasis by dietary genistein

Prostate cancer frequently metastasizes to the bone, and the treatment outcome for metastatic prostate cancer has been disappointing so far. Dietary genistein, derived primarily from soy product, has been proposed to be partly responsible for the low rate of prostate cancer in Asians. Our previous studies have shown that genistein elicits pleiotropic effects on prostate cancer cells, but there are no studies documenting comprehensive gene expression profiles and antitumor effects of dietary genistein on human prostate cancer grown in human bone environment. In this study, we investigated the effects of genistein on PC3 prostate cancer cells and experimental PC3 bone tumors created by injecting PC3 cells into human bone fragments previously implanted in severe combined immunodeficient (SCID) mice (SCID human model). We found that genistein significantly inhibited PC3 bone tumor growth using both prevention and intervention strategies. By using microarray and real-time polymerase chain reaction technology, we found that genistein regulated the expression of multiple genes involved in the control of cell growth, apoptosis, and metastasis both in vitro and in vivo. For example, the expression of various metalloproteinases (MMPs) in PC3 bone tumors was inhibited by genistein treatment, whereas osteoprotegerin was upregulated. MMP immunostaining and transfection experiments also demonstrated that MMP-9 expression was inhibited in PC3 cells in vitro and PC3 bone tumors in vivo after genistein treatment. These results, particularly the in vivo results, demonstrate that dietary genistein may inhibit prostate cancer bone metastasis by regulating metastasis-related genes. Genistein may thus be a promising agent for the prevention and/or treatment of prostate cancer.

Antiproliferative and antiangiogenic activities of genistein in human renal cell carcinoma

OBJECTIVES

To determine whether genistein, an isoflavone that is plentiful in soy beans, could inhibit the growth of human renal cell carcinoma (RCC) cells in vitro, induce apoptosis, and suppress neovascularization in vivo induced by human RCC cells.

METHODS

We investigated the effect of genistein on cell proliferation in four human RCC cell lines, SMKT R-1, R-2, R-3, and R-4. The terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assay was performed to examine whether genistein could induce apoptosis in SMKT R-1 cells. To evaluate the effect of genistein on in vivo angiogenesis, we used a new mouse dorsal air sac model in which we could evaluate it simply and quantitatively. Radioisotope-labeled red blood cells were injected into a tail vein in mice bearing a Millipore filter chamber containing genistein, and the vascular volume was examined by measuring the radioactivity of the mouse dorsal skin.

RESULTS

Treatment with genistein for 48 hours inhibited cell proliferation in a dose-dependent manner and 100 microg/mL genistein inhibited it in a time-dependent manner. A dose of 50 microg/mL genistein clearly induced cell apoptosis. The vascular volume after implantation of the Millipore filter chamber containing RCC cells increased to threefold that without RCC cells. Genistein in the Millipore filter chamber significantly decreased the neovascularization induced by human RCC cells in vivo.

CONCLUSIONS

The results of this study demonstrated that genistein inhibited cell proliferation, induced apoptosis, and suppressed in vivo angiogenesis in human RCC cells. Genistein may be a promising antitumorigenic and antiangiogenic agent for the treatment and prevention of RCC.

Inhibition of carcinogenesis by polyphenols: evidence from laboratory investigations

Many plant polyphenolic compounds have been shown to have cancer-preventing activities in laboratory studies. For example, tea and tea preparations have been shown to inhibit tumorigenesis in a variety of animal models of carcinogenesis, involving organ sites such as the skin, lungs, oral cavity, esophagus, stomach, liver, pancreas, small intestine, colon, and prostate. In some of these models, inhibitory activity was demonstrated when tea was administered during the initiation, promotion, or progression stage of carcinogenesis. The cancer-preventing activities of these and other polyphenols, such as curcumin, genistein, and quercetin, are reviewed. In studies in vitro, many of these compounds have been shown to affect signal transduction pathways, leading to inhibition of cell growth and transformation, enhanced apoptosis, reduced invasive behavior, and slowed angiogenesis. However, the concentrations used in cell culture studies were much higher than those found in vivo. If we propose mechanisms for cancer prevention on the basis of cell line experiments, then these activities must be demonstrated in vivo. The bioavailability, ie, tissue and cellular concentrations, of dietary polyphenols is a determining factor in their cancer-preventing activity in vivo. For example, compounds such as curcumin are effective when applied topically to the skin or administered orally to affect the colon but are not effective in internal organs such as the lungs. More in-depth studies on bioavailability should facilitate correlation of mechanisms determined in vitro with in vivo situations, increase our understanding of dose-response relationships, and facilitate extrapolation of results from animal studies to human situations.

Genistein alone or combined with cyclophosphamide may stimulate 16/C transplantable mouse mammary cancer growth

Among the many potential antiangiogenic agents now in various stages of preclinical or clinical study, genistein (GEN) has generated wide interest being because of its natural origin (soybeans) and epidemiological studies showing the cancer chemopreventive effects of soybean consumption. In this paper the in vivo effects of GEN applied either alone or together with cyclophosphamide on the growth of mouse transplantable mammary carcinoma (16/C) transplanted either orthotopically or ectopically is presented. The growth of 16/C mouse mammary cancer transplanted subcutaneously (s.c.) or into the mammary gland (orthotopically-orth.) was stimulated by GEN administered from day 4 after tumor cell inoculation. Such stimulation was not observed when the treatment with GEN was started at day 12 after cell inoculation. Stimulation of tumor growth by GEN was markedly higher in mice transplantedorth. than in those transplanted s.c.. However, GEN did not affect the expression of estrogen (ER)and progesterone receptors (PgR) in the orthotopic model of 16/C cancer. In the case of subcutaneously growing tumors, treatment with GEN lowered (2-fold) the expression of both ER and PgR. In the interpretation of these results, the pleiotropic (including hormonal and antiproliferative), sometimes opposing effects of genistein in vivo should be considered. It seems rather reasonable to exclude breast and, perhaps, other hormone-dependent cancers from the treatment and chemoprevention with soy-derived phytoestrogens until its mechanism(s) of action on various cancer cells is completely understood.

Cellular and physiological effects of soy flavonoids

Recent experimental and epidemiological studies have provided convincing evidence for a variety of health benefits derived from the consumption of soy and soy food products. For example, soy isoflavones are felt to protect against different cancers, cardiovascular disease, and bone loss. Many studies have demonstrated the effect of soy isoflavones on specific target molecules and signaling pathways, including but not limited to, cell proliferation and differentiation, cell cycle regulation, apoptosis, angiogenesis, cell adhesion and migration, metastasis, and activity of different enzymes. Isoflavones also share structural homologies with estrogens and are therefore classified as phytoestrogens with weak estrogenic properties. Since isoflavones bind to estrogen receptors (ER alpha and ER beta), they are considered to be possible estrogen receptor modulators. However, isoflavones can also exert biological effects independent of their phytoestrogenic activities. Recent studies suggest beneficial health effects of soy and recommend increasing the intake of isoflavone-rich soy protein to the level of intake commonly used in Asian countries.

Effects of genistein on hot flushes in early postmenopausal women: a randomized, double-blind EPT- and placebo-controlled study

OBJECTIVE

We evaluated and compared the effects of the phytoestrogen genistein, estrogen-progestogen therapy (EPT), and placebo on hot flushes and endometrial thickness in postmenopausal women.

DESIGN

Ninety healthy, postmenopausal women, 47 to 57 years of age, were randomly assigned to receive for 1 year continuous EPT (n = 30; 1 mg 17beta-estradiol combined with 0.5 mg norethisterone acetate), the phytoestrogen genistein (n = 30; 54 mg/day), or placebo (n = 30). Endometrial safety was evaluated by intravaginal ultrasounds at baseline, 6 and 12 months.

RESULTS

By comparison with placebo, daily flushes reduced significantly by a mean of 22% (95% CI: -38 to -6.2; P < 0.01) after 3 months, by a mean of 29% (95% CI: -45 to -13; P < 0.001) after 6 months, and by a mean of 24% (95% CI: -43 to -5; P < 0.01) after 12 months of genistein treatment. Flush score decreased by a mean of 53% (95% CI: -79 to -26; P < 0.001) after 3 months, by a mean of 56% (95% CI: -83 to -28; P < 0.001) after 6 months, and by a mean of 54% (95% CI: -74 to -33; P < 0.001) after 12 months of EPT, as compared with placebo. No side effect was observed on the uterus of the participants.

CONCLUSIONS

The present study confirms that genistein might have positive effects on hot flushes without a negative impact on endometrial thickness and suggests a future role of this phytoestrogen as a strategically therapeutic alternative in the management of postmenopausal symptoms.

Phyto-oestrogens in the prophylaxis of menstrual migraine

BACKGROUND

Falling levels of estrogen is the major provocative factor in migraine associated with menstruation.

OBJECTIVE

We assessed the efficacy of the combination of two phyto-oestrogens, as perimenstrual, prophylactic treatment of menstrual migraine and tested their effect on cerebral haemodynamic.

SUBJECTS AND METHODS

Women with a history of menstrual migraine (i.e., attacks occurring exclusively on day 1+/-2 days of menstruation and at no other time of the cycle) were included in the study. Eleven women fulfilling the inclusion criteria underwent to a 3-month cyclic treatment with 56 mg of genisteine and 20 mg of diadzeine per day. Transcranial doppler evaluation (TCD) was performed at baseline and after treatment.

RESULTS

Among the ten women who completed the study the average number of days with migraine during the baseline period decreased significantly after 3 months of therapy (P < 0.005). There were no major side-effects. Therapy did not affect cerebral blood flow velocities.

CONCLUSIONS

Phyto-oestrogens appear to be an effective treatment in menstrual migraine prophylaxis. This effect seems to be unrelated to cerebral hemodynamic. Placebo-controlled trials on larger number of patients are necessary to confirm our findings.

[Effect of genistein on expression of angiogenesis related factors in HER-2/neu-overexpressing breast cancer cells]

To study the molecular mechanism of inhibition of angiogenesis in HER-2/neu-overexpressing breast cancer by genistein, HER-2/neu negative expression breast cancer MCF-7 cells were transfected with HER-2/neu to establish HER-2/neu-overexpressing MCF-7 cells (named MCF-7/HER-2). Expression of vascular endothelial growth factor (VEGF), urokinase-type plasminogen activator (uPA), matrix metalloproteinase-2,9 (MMP-2,9) in MCF-7, MCF-7/HER-2 as well as genistein-treated MCF-7/HER-2 were measured by immunocytochemistry and Western blot. We found that the expression of VEGF, MMP-2,9 and uPA in MCF-7/HER-2 cells were highter than that in MCF-7 cells, those angiogenesis related factors expression in MCF-7/HER-2 cells significantly decreased after treatment with genistein. Genistein could inhibit expression of angiogenesis-related factors VEGF, MMP-2,9 and uPA in HER-2/neu-overexpressing breast cancer cells, and this may be part of molecular mechanism of its anti-angiogenesis in HER-2/neu-overexpressing breast cancer.

Chemopreventive potential of epigallocatechin gallate and genistein: evidence from epidemiological and laboratory studies

A wide array of antioxidative and anti-inflammatory substances derived from edible plants have been reported to possess chemopreventive and chemoprotective activities. Among the most extensively investigated and well-defined dietary chemopreventives are epigallocatechin gallate (EGCG), a principal antioxidant derived from green tea and genistein, a major pharmacologically active isoflavone widely present in soy products. Multiple lines evidence from epidemiologic studies indicate that frequent consumption of green tea is inversely associated with the risk of several types of human cancer, and studies with animal and in vitro cell culture models have revealed EGCG as a major chemopreventive ingredient of green tea. The lower frequencies of breast and prostate cancer in Asian population in general, compared to those in Western societies have been attributed to their consumption of relatively large amounts of soy products. Genistein, as a principal chemopreventive components of soy, exerts a wide array of chemopreventive activities in each stage of multistep carcinogenesis. The purpose of this review is to provide perspectives on the molecular basis of chemopreventive activities of EGCG and geneistein as representative functional food phytochemicals with emphasis on their ability to control intracellular signaling cascades responsible for regulating cell growth and differentiation.

Apoptosis-inducing effect of chemotherapeutic agents is potentiated by soy isoflavone genistein, a natural inhibitor of NF-kappaB in BxPC-3 pancreatic cancer cell line

Cancer chemotherapeutic strategies should be devised to provide higher tumor response and lower toxicity for combination chemotherapy. Genistein has been shown to inhibit the growth of various cancer cells in vitro and in vivo without toxicity to normal cells. The antitumor effects of genistein could be in part due to inactivation of NF-kappaB activity. In contrast, chemotherapeutic agents inadvertently induce NF-kappaB activity, which may lead to chemoresistance. In this study, we investigated whether the inactivation of NF-kappaB by genistein would enhance the efficacy of chemotherapeutic agents. BxPC-3 pancreatic cancer cells were pretreated with 30 micromol/L genistein for 24 hours and then exposed to lower concentrations of chemotherapeutic agents for an additional 24 hours. Cell growth inhibition assay, apoptosis assay, and NF-kappaB EMSA were performed. The combination of 30 micromol/L genistein with 1 nmol/L docetaxel or 100 nmol/L cisplatin elicited significantly greater inhibition of cell growth compared with either agent alone. The combination treatment induced more apoptosis in BxPC-3 cells compared with single agents. Moreover, the NF-kappaB activity was significantly increased within 2 hours of docetaxel or cisplatin treatment, and the NF-kappaB-inducing activity of these agents was completely abrogated in cells pretreated with genistein. These results clearly suggest that genistein pretreatment, which inactivates NF-kappaB activity, together with other cellular effects of genistein, may contribute to increased cell growth inhibition and apoptosis inducing effects of nontoxic doses of docetaxel and cisplatin, which could be a novel strategy for the treatment of pancreatic cancer.

Vitamin D receptor and p21/WAF1 are targets of genistein and 1,25-dihydroxyvitamin D3 in human prostate cancer cells

We investigated mechanisms by which genistein and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] act synergistically to inhibit the growth of the human prostate cancer cell line LNCaP. We demonstrate that 1,25(OH)(2)D(3) and genistein cooperate to up-regulate the vitamin D receptor protein by increasing the stability of the vitamin D receptor. Genistein and 1,25(OH)(2)D(3) also cooperate to up-regulate the levels of p21/WAF1 (p21). Small interfering RNA-mediated knockdown of p21 expression showed that p21 is essential for significant growth inhibition of LNCaP cells in response to either compound or their combination. We conclude that one mechanism of synergism between genistein and 1,25(OH)(2)D(3) is through genistein modulation of vitamin D signaling.

Cardiovascular Effects of the Phytoestrogen Genistein

Phytoestrogenic molecules have received a great deal of attention over the last few years because of their potentially preventive roles against a few of today's most prevalent chronic diseases, namely cardiovascular diseases, osteoporosis and hormone related cancers. Of the several phytoestrogens, genistein in particular has been shown to be the most efficacious in animal models and experimental studies. Genistein in vitro relaxes rat arteries by a nitric oxide dependent mechanism and enhances the dilator response to acetylcholine of atherosclerotic arteries. Genistein supplementation improves endothelial dysfunction induced by oophorectomy in rats and reduces infarct size in an experimental model of myocardial ischaemia-reperfusion injury. Furthermore, genistein in postmenopausal women increases plasma nitric oxide breakdown products, reduces endothelin-1 levels and improves endothelial dependent vasodilation in post-menopausal women. All these findings, taken together, would suggest that this molecule might represent an attractive alternative for cardiovascular protection.

Effects of a genistein-rich extract on PSA levels in men with a history of prostate cancer

OBJECTIVES

To determine whether supplemental amounts of soy isoflavone (genistein-rich extract) would lower prostate-specific antigen (PSA) levels more than 50% in patients with prostate cancer (CaP).

METHODS

A total of 62 men (mean age 73.6 years, range 61.4 to 89.3) with histologically proven CaP who had two consecutive elevated PSA readings were accrued during a 13-month period. An open-label pilot study was conducted for 6 months in which the patients took capsules containing the genistein-rich extract three times daily by mouth. The subjects were in one of five groups: after radical retropubic prostatectomy (n = 9), after radiotherapy (n = 17), after both radical retropubic prostatectomy and radiotherapy (n = 6), off-cycle during hormonal therapy (intermittent hormones; n = 14), or active surveillance (n = 16). The primary endpoint for the trial was a 50% reduction in the PSA level at 6 months compared with before treatment.

RESULTS

Of the 62 men enrolled, 52 were available for evaluation at 6 months. Three patients discontinued because of adverse events (diarrhea) and seven because of personal choice. One of 52 patients had a more than 50% reduction in the PSA level (1.9% response, 95% confidence interval 0.1% to 10.3%). An additional 7 patients had PSA reductions that were less than 50%. All 8 patients with lower PSA levels at 6 months were in the active surveillance (watchful waiting) treatment subgroup. Repeated measure regression models allowing for correlation between initial levels and change also indicated a decline in PSA in this group compared with other groups: 0 of 52 had a complete response, 9 (17%) had a partial response, 8 (15%) had stable disease, and 35 (67%) had disease progression. In the 9 patients with a partial response, 6 had pathologic findings that were moderately differentiated, 2 had well-differentiated findings, and 1 had poorly differentiated findings. Therefore, the response in this group of patients did not appear to be driven by the Gleason score. The total testosterone level was lowered in one of the patients responding, but it was higher in five others.

CONCLUSIONS

A genistein-rich extract as the sole treatment for CaP did not reduce PSA levels by 50% or more in 51 of 52 subjects. Thus, it does not appear to be an effective treatment for CaP when given alone. However, 8 of 13 evaluated patients in the active surveillance group had either no rise or a decline in PSA levels of less than 50%. More study is warranted for those choosing active surveillance.

Prepubertal estradiol and genistein exposures up-regulate BRCA1 mRNA and reduce mammary tumorigenesis

Prepubertal exposure to soy or its biologically active component genistein reduces later breast cancer risk in both animal models and human populations. We investigated whether that might be due to reported estrogenic properties of genistein. Our study indicated that daily prepubertal exposures between postnatal days 7 and 20 to 10 microg 17beta-estradiol (E2) reduced later risk of developing 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors. Assessment of mammary gland morphology revealed that both prepubertal E2 and genistein (50 microg daily) exposures reduced the size of mammary epithelial area and number of terminal end buds (TEBs) and increased the density of lobulo-alveolar structures, suggesting that these exposures induced elimination of targets for malignant transformation by differentiation. Next, the mechanisms mediating the protective effects of E2 and genistein were investigated. E2 is shown to up-regulate BRCA1, a tumor suppressor gene that participates in DNA damage repair processes and cell differentiation and that down-regulates the activity of estrogen receptor (ER)-alpha. The expression of BRCA1 mRNA was up-regulated in the mammary glands of rats exposed to E2 or genistein during prepuberty, when determined at the ages of 3, 8 and 16 weeks. Prepubertal E2 exposure reduced ER-alpha levels in the mammary gland, while prepubertal genistein exposure had an opposite effect. Our results suggest that prepubertal estrogenic exposures may reduce later breast cancer risk by inducing a persistent up-regulation of BRCA1 in the mammary gland.

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 clinical use of a preparation based on phyto-oestrogens in the treatment of menopausal disorders

In order to evaluate the efficacy of soya isoflavones (genistein and daidzein) in the treatment of the principal menopausal disorders, a double blind randomized study was performed on a sample of 50 women (with an average age of 53.3 +/- 3.1 years) with Climacteric syndrome referred to the I Clinica Ostetrica e Ginecologica, Policlinico Umberto I, Roma. The research protocol involved the random subdivision of the enrolled sample into two groups of 25 women, group 1 (with an average age of 53.3 +/- 3.5 years, and an average menopausal age of 51.6 +/- 1.8 years) and group 2 (with an average age of 53.1 +/- 2.9 years, and an average menopausal age of 51.3 +/- 1.2 years), who were to receive treatment for three months with the product being studied and with a placebo. After the three-month period, as an additional check, the group initially treated with the placebo would move to the phyto-oestrogens and viceversa. All of the patients were subjected to a series of clinical and instrumental examinations and were asked to fill in a questionnaire concerning their complaints, at the start, at halfway (third month) and at the end (sixth month) of the trial. The results of the evaluation of the questionnaires performed on the 47 patients who had completed the trial showed, in the first three months, an improvement in the symptoms (hot flushes) in 11 patients treated with phyto-oestrogens against 6 patients from the group that received only the placebo. In the second three-month period the hot flushes reappeared in 4 of the 11 patients who had previously seen improvements and had then passed to the placebo. In contrast, the group that passed to the phyto-oestrogens, after treatment with the placebo, experienced the disappearance of hot flushes in 11 women, including the 6 who had already improved in the first three months. There was no significant reduction in anxiety, insomnia or vaginal dryness. None of the enrolled patients indicated complaints linked to the treatment. It can be concluded that the use of a product based on phyto-oestrogens, such as the one experimented, can lead to a significant reduction in some of the disorders linked with the menopause, especially hot flushes.

Isoflavone genistein: photoprotection and clinical implications in dermatology

Genistein is a soybean isoflavone with diverse biological activities. It is a potent antioxidant, a specific inhibitor of protein tyrosine kinase, and a phytoestrogen. In recent years, increasing evidence has accumulated that this natural ingredient shows preventative and therapeutic effects for breast and prostate cancers, postmenopausal syndrome, osteoporosis, and cardiovascular diseases in animals and humans. In the past decade we have conducted a series of studies and demonstrated that genistein has significant antiphotocarcinogenic and antiphotoaging effects. Genistein substantially inhibits skin carcinogenesis and cutaneous aging induced by ultraviolet (UV) light in mice, and photodamage in humans. The mechanisms of action involve protection of oxidative and photodynamically damaged DNA, downregulation of UVB-activated signal transduction cascades, and antioxidant activities. In this article, we review the biological activities of genistein, as well as published and unpublished research from our laboratory. In addition, we discuss the potential application of genistein to clinical dermatology.

Genistein Appears to Prevent Early Postmenopausal Bone Loss as Effectively as Hormone Replacement Therapy

Recent data from a randomized, double-blind, placebo-controlled, yearlong clinical trial suggest that supplementation with the dietary phytoestrogen genistein (54 mg/day) may be as effective as hormone replacement therapy in attenuating menopause-related bone loss without causing the associated side effects. These findings may have implications for the development of diet-based strategies aimed at osteoporosis prevention.

Genistein enhances the cisplatin-induced inhibition of cell growth and apoptosis in human malignant melanoma cells

Genistein, a naturally occurring isoflavone found chiefly in soybeans, has been reported to be a potent antitumor agent. Genistein is presumed to exert multiple effects related to the inhibition of cancer growth. Metastatic melanoma is a chemotherapy-refractory neoplasm. The present study was designed to explore the possible activity of genistein to inhibit the aberrant proliferation and to induce apoptosis of human malignant melanoma cells in cooperation with cisplatin treatment. Five human melanoma cell lines were utilized for these experiments. Genistein at physiologic concentrations (20 microM) did not induce apoptosis by itself but did enhance cisplatin-induced apoptosis in all five human melanoma cell lines tested. The enhanced susceptibility among the cell lines was diverse. Changes in the expression of two anti-apoptotic proteins, bcl-2 and bcl-xL, and one pro-apoptotic protein, apoptotic protease activating factor-1 (Apaf-1), were examined. Genistein alone or cisplatin alone generally did not alter bcl-2 expression or bcl-xL expression, but slightly increased Apaf-1 in some cell lines. The combined treatment with genistein and cisplatin significantly reduced bcl-2 and bcl-xL protein and increased Apaf-1 protein expression. These data suggest that genistein therapy may enhance the chemosensitivity of melanoma patients.

In vivo vascular effects of genistein on a rat model of septic shock induced by lipopolysaccharide

The aim of this study was to investigate the effects of in vivo administration of genistein on rat cardiovascular abnormalities induced by lipopolysaccharide (LPS). Four hours after injection, LPS (10 mg/kg) caused a stable fall in mean arterial pressure (13%) accompanied by ex vivo vascular hyporeactivity to noradrenaline (NA) and relaxation to l-arginine (L-arg), which were inhibited by previous incubation with l-NAME. Endotoxin also caused impairment of aortic relaxant response to acetylcholine, increase nitrite and malonaldehyde plasma levels by 8.6-fold and 2-fold, respectively, and induced aortic expression of inducible nitric-oxide synthase (iNOS) and nitrotyrosine protein. Genistein (1 mg/kg) and daidzein (1 mg/kg) reduced contractile response to NA in vascular tissue, but only genistein was able to inhibit hyporesponsiveness to NA, relaxation to l-arg, increase in nitrite plasma levels, and iNOS expression produced by endotoxin. Moreover, genistein restored impaired aortic relaxation to acetylcholine, lipid peroxidation, and suppressed long-term hypotension. In conclusion, genistein administrated in vivo prevents hypotension and vascular alterations induced by LPS. These protective effects are mediated by both its antioxidant properties and the inhibition of nitric oxide overproduction from de novo synthesis of iNOS due to its tyrosine kinase inhibitor effect.

[The beneficial effect of genistein on mandible bone metabolism in ovariectomized rats]

OBJECTIVE

To detect the effect of genistein on mandible metabolism in ovariectomized rats.

METHODS

Forty 12 week-old female SD rats were randomly assigned to four groups: (1) sham operated; (2) ovariectomized; (3) ovariectomized and treated with estradiol; (4) ovariectomized and received genistein, 45 mg/kg body weight per day. After 12 weeks, bone mineral density (BMD), serum level of alkaline phosphatase (ALP), acid phosphatase (ACP), osteocalcin, IL-1beta, TNF-alpha, IL-6 and calcitonin (CT) were evaluated. In addition, the serum estradiol and the weight of uteri were also examined to indicate the side effect of genistein to the uteri.

RESULTS

Ovariectomized animals had a significant decrease in BMD, and increased serum level of ALP, ACP, IL-1beta and osteocalcin compared with sham rats. After treated with genistein, BMD and the serum level of ALP, ACP, osteocalcin increased significantly, while the serum level of IL-1beta and TNF-alpha decreased. Especially, the increase of ALP and osteocalcin was higher than that of estradiol-treated animal. Additionally, the uterus weight index and the serum estradiol in genistein-treated rats were lower significantly than those of estradiol-treated rats.

CONCLUSIONS

Genistein can improve the mandible bone metabolism as well as its effect on femur through the promotion of bone formation and the prevention of bone resorption with slight side effect. Genistein provides an additional viable way to therapy for osteoporosis in the jaw bones.

Inhibitory actions of genistein in human breast cancer (MCF-7) cells

Genistein, a natural isoflavanoid phytoestrogen, is thought to be the active ingredient in soy that possesses breast cancer preventive properties. The molecular mechanisms that are involved in its cancer preventive properties have not been completely understood. The present study is designed to investigate the mechanism involved in the inhibitory action of genistein in MCF-7 cells. Genistein at 50 and 100 microM significantly arrested the growth of MCF-7 cells at G2/M phase (P<0.05) and decreased at the proliferative S phase (P<0.05). Using cDNA microarray technology, genes differentially regulated by genistein were identified. In particular, as confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR), genistein up-regulated heat shock protein 105 (HSP) mRNA and down-regulated mRNA expression of serum response factor (SRF), estrogen receptor (ER) alpha, disabled homolog 2 (DOC 2) and recombination activation gene 1 (RAG-1). Using real time RT-PCR, we have shown that HSP and SRF mRNA were both regulated by genistein in a time- and dose-dependent manner; however, it appears that only the effect of genistein on SRF mRNA, but not HSP mRNA expression, can be partially abolished by cotreatment with estrogen antagonist ICI 182,780. Western blotting analysis showed that the expressions of the ERalpha and SRF protein decreased significantly with genistein treatment (P<0.05). These results suggest that the inhibitory action of genistein on human breast cancer cells appears to be complex and is only partially mediated by the alteration of estrogen receptor-dependent pathways.

The red clover (Trifolium pratense) isoflavone biochanin A modulates the biotransformation pathways of 7,12-dimethylbenz[a]anthracene

Several flavonoids have shown their anti-carcinogenic effects in various models. The soyabean isoflavone genistein was demonstrated earlier in our laboratory to be an effective inhibitor of dimethylbenz[a]anthracene (DMBA)-induced DNA damage in MCF-7 cells by curbing cytochrome P450 (CYP) 1 enzymes. The red clover (Trifolium pratense) isoflavone biochanin A is a methylated derivative of genistein, and its anti-mutagenic effect in bacterial cells has been shown previously. Because of its protection against chemical carcinogenesis in an animal model, biochanin A was selected for testing in our established MCF-7 cell system. From the results obtained in the semi-quantitative reverse transcription-polymerase chain reaction and xenobiotic response element (XRE)-luciferase reporter assays, biochanin A could reduce xenobiotic-induced CYP1A1 and -1B1 mRNA abundances through the interference of XRE-dependent transactivation. Enzyme kinetic studies also indicated that biochanin A inhibited both CYP1A1 and -1B1 enzymes with inhibition constant (Ki) values 4.00 and 0.59 microm respectively. Since the biotransformation of DMBA was dependent on CYP1 enzyme activities, biochanin A was able to decrease the DMBA-DNA lesions. The present study illustrated that the red clover isoflavone could protect against polycylic aromatic hydrocarbon-induced DNA damage.

Indole-3-carbinol is a negative regulator of estrogen

Studies increasingly indicate that dietary indole-3-carbinol (I3C) prevents the development of estrogen-enhanced cancers including breast, endometrial and cervical cancers. Epidemiological, laboratory, animal and translational studies support the efficacy of I3C. Whereas estrogen increases the growth and survival of tumors, I3C causes growth arrest and increased apoptosis and ameliorates the effects of estrogen. Our long-range goal is to best use I3C together with other nutrients to achieve maximum benefits for cancer prevention. This study examines the possibility that induction of growth arrest in response to DNA damage (GADD) in genes by diindolylmethane (DIM), which is the acid-catalyzed condensation product of I3C, promotes metabolically stressed cancer cells to undergo apoptosis. We evaluated whether genistein, which is the major isoflavonoid in soy, would alter the ability of I3C/DIM to cause apoptosis and decrease expression driven by the estrogen receptor (ER)-alpha. Expression of GADD was evaluated by real-time reverse transcription-polymerase chain reaction. Proliferation and apoptosis were measured by a mitochondrial function assay and by fluorescence-activated cell sorting analysis. The luciferase reporter assay was used to specifically evaluate expression driven by ER-alpha. The estrogen-sensitive MCF-7 breast cancer cell line was used for these studies. We show a synergistic effect of I3C and genistein for induction of GADD expression, thus increasing apoptosis, and for decrease of expression driven by ER-alpha. Because of the synergistic effect of I3C and genistein, the potential exists for prophylactic or therapeutic efficacy of lower concentrations of each phytochemical when used in combination.

DING, a genistein target in human breast cancer: a protein without a gene

Because most noncancer cells are tolerant to high micromolar concentrations of genistein (GEN), inhibitory or stimulatory effects of GEN have been claimed for a wide variety of biochemical targets that lead to a plethora of potential mechanisms. However, because GEN is present in tissues in the nanomol-per-liter range, most of these mechanisms are unlikely to be relevant in vivo. To better identify proteins that are targets of GEN, we used a GEN-agarose-affinity phase. Cytosols from human breast cancer MCF-7 cells were fractionated over a Sephadex diethylaminoethyl column, and nonabsorbed proteins in the flow-through were affinity absorbed onto a 2-carboxygenistein-agarose column. After proteins were washed with 100 mmol NaCl/L to remove weakly bound proteins, affinity elution was conducted with 1 mmol 2-carboxygenistein/L. Using this method, a p38 protein was recovered from MCF-7 cells. N-terminal chemical sequencing of the first 30 residues of the protein revealed a peptide sequence similar to those that have been discovered in human tissues (a T-cell attractant protein from synovial fluid from patients with osteoarthritis and an analogous human skin fibroblast protein using a hirudin-affinity column) as well as a cotonine-binding protein from rat brain and related proteins in plants. In each case, the corresponding gene has not been found. In conclusion, although much of the human genome has been sequenced, novel proteins that are not described by genome data remain to be found. The DING protein (N-terminal amino acid sequence Asp-Ile-Asn-Gly) that binds to genistein with high affinity is one of these. Its biological role, however, remains to be defined.

Effect of prenatal and prepubertal genistein exposure on N-methyl-N-nitrosourea-induced mammary tumorigenesis in female Sprague-Dawley rats

BACKGROUND

The effect of prenatal and prepubertal genistein exposure on the development of chemically-induced mammary carcinomas in rat was investigated.

MATERIALS AND METHODS

Genistein was subcutaneously (s.c.) injected daily, from gestational days 15 to 19, into pregnant Sprague-Dawley rats at 0, 1.5 or 30 mg/kg/day. Female offspring of mothers not exposed to genistein during pregnancy received daily s.c. injection, from prepubertal days 15 to 19, at a dose of 1.5 or 30 mg/kg/day. At 28 days of age, 6 female offspring from each group were sacrificed to observe the influence of genistein and the remaining rats were injected intraperitoneally with 50 mg/kg N-methyl-N-nitrosourea (MNU). Rats injected with MNU were sacrificed at 26 weeks of age or when their largest mammary tumor was > or = 1 cm in size.

RESULTS

At the time when MNU was administered, the different groups had comparable mammary gland development; genistein-treated and -untreated rats had similar numbers of terminal end buds (TEBs) at the periphery of the mammary glandular tree. However, estrogen receptor alpha (ER alpha)- and progesterone receptor (PgR)-positive cells, p63-positive cells and proliferating cell nuclear antigen (PCNA)-labeling index were lower in genistein-exposed TEBs. Although tumor multiplicity and latency were not significant, prenatal or prepubertal genistein exposure, at low or high dosage, tended to suppress the incidence of mammary carcinomas > or = 1 cm; suppression was significant in the prepubertal low-dose group.

CONCLUSION

The majority of the mammary carcinomas in the present study were hormone-dependent. The present findings suggest that administration of genistein in the perinatal period has protective effects against MNU-induced mammary carcinoma in Sprague-Dawley rats, via reduction of levels of ER alpha- and/or PgR-positive cells (presumed progenitor cells of mammary carcinomas), p63-positive mammary progenitor/stem cells (involved in cell renewal) and PCNA-positive cells (necessary for cell proliferation).

Genistein as an anti-inflammatory agent

OBJECTIVE AND DESIGN

The aim of this study was to investigate the impact of the isoflavone genistein on in vivo cell-mediated responses. In addition, we wanted to study the influence of genistein on collagen induced arthritis (CIA) in mice.

METHODS

Delayed type hypersensitivity reaction (DTH) to oxazolone and the inflammatory response to olive oil were measured in mice treated with genistein. In addition, the impact of genistein treatment on disease progression and outcome of collagen induced arthritis (CIA) was examined.

RESULTS

The DTH reaction to oxazolone and the granulocyte-mediated response were significantly suppressed in genistein-treated as compared to control mice. Also, genistein treatment led to decreased levels of oxazolone-specific antibodies. Histologically, mice exposed to genistein and immunized with collagen II displayed somewhat lower degree of inflammation and joint destruction. In addition, serum levels of autoantibodies to collagen II were significantly lower following genistein-treatment in immunized mice.

CONCLUSION

We conclude that genistein exerts evident anti-inflammatory properties affecting granulocytes, monocytes, and lymphocytes.

[Phytoestrogens]

The soy-isoflavones genistein and daidzein and the flaxseed-lignans secoisolariciresinol and matairesinol belong to the group of phytoestrogens. Epidemiological data suggest that phytoestrogens have a preventive effect against various estrogen-related diseases/symptoms such as breast cancer, menopausal symptoms, cardiovascular diseases, and osteoporosis. To prove these assumptions, available controlled clinical trials have been critically reviewed. Especially soy-isoflavones have been extensively studied. There is no scientific evidence for an effect of phytoestrogens on menopausal symptoms and risk factors of breast cancer. However, isoflavones-containing soy protein can lower total cholesterol, LDL cholesterol, and triglyceride serum levels. The strongest evidence exists for a preventive effect of soy isoflavones on postmenopausal bone loss of the lumbar spine. Distinct effects on estrogen-related diseases can be explained at least in part by the different affinity of isoflavones to estrogen receptors alpha and beta and the distinct tissue distribution of these receptors.

Targeting colon cancer cells with genistein-17.1A immunoconjugate

We have shown that genistein, a major component of soy, has anti-colon cancer effects in vitro. These effects are attainable at high concentrations that are difficult to achieve in the serum. The purpose of this study was to enhance the activity of genistein against colon cancer cells by coupling it to 17.1A. The monoclonal antibody 17.1A recognizes an epithelial membrane antigen that is overexpressed in colon cancer. Synthesis of Gen-17.1A was achieved by photochemical conjugation using sulfa-SANPAH. Its purity was evaluated by SDS-PAGE. Binding of Gen-17.1A to SW-620 and HT-29 cells was shown using flow cytometry. Internalization was demonstrated by FITC-labeling. Gen-17.1A induced apoptosis in colon cancer cells as evidenced by the acridine orange/ethidium bromide staining method. Gen-17.1A significantly inhibited colon cancer cell growth in vitro and in vivo. Our findings suggest that conjugating genistein to 17.1A monoclonal antibody enhances its effects against colon cancer cells.

Prevention of metastatic pancreatic cancer growth in vivo by induction of apoptosis with genistein, a naturally occurring isoflavonoid

INTRODUCTION

The critical need for novel therapeutic approaches to pancreatic cancer treatment is clear. Genistein, a naturally occurring isoflavonoid, is active against certain solid malignancies, but its effect on pancreatic cancer is unknown.

AIMS

To investigate the bioactivity of genistein in experimental pancreatic cancer in vitro and in vivo.

METHODOLOGY

The effect of intraperitoneal genistein administration on local tumor growth and metastatic disease was determined in an orthotopic nude mouse model. Apoptosis in tumor specimens was determined by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) technique. In vitro, the effect of genistein on cell growth was assessed by cell count and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) colorimetric assay. Apoptosis was determined in vitro by DNA laddering and annexin-V. Caspase-3 and nuclear factor-kappaB activity were measured following genistein treatment.

RESULTS

In vivo, genistein significantly improved survival, almost completely inhibited metastasis, and increased apoptosis in an orthotopic model of pancreatic cancer. In vitro genistein treatment resulted in apoptosis in all pancreatic cancer cell lines tested, and this appeared to be mediated by activation of caspase-3.

CONCLUSION

These findings suggest that the antimetastatic effect of genistein treatment in vivo is mediated by induction of apoptosis. Genistein may have a therapeutic benefit for patients with pancreatic cancer, in particular after surgery, to prevent recurrence of metastatic disease.

Lack of significant genotoxicity of purified soy isoflavones (genistein, daidzein, and glycitein) in 20 patients with prostate cancer

BACKGROUND

Genistein may be useful in the prevention or treatment of prostate cancer; however, it causes genetic damage in cultured human cells.

OBJECTIVE

The objective was to assess the potential genotoxicity of a purified soy unconjugated isoflavone mixture in men with prostate cancer.

DESIGN

Twenty patients with prostate cancer were treated with 300 mg genistein/d for 28 d and then with 600 mg/d for another 56 d. In peripheral lymphocytes, DNA strand breaks were assessed as nuclear tail moment, chromosomal damage was assessed as micronucleus frequency (MF), and translocations of the MLL gene (11q23) were assessed by using fluorescence in situ hybridization. Values are also reported for 6 healthy men. The studies were performed under Investigational New Drug application no. 54 137 at a tertiary referral academic medical center.

RESULTS

No changes in group average or individual nuclear tail moment and MF were observed. We observed a single elevated MF value in one subject that exceeded a clinical threshold set before we initiated the study. A significant decrease in average COMET tail moment was observed on day 28 relative to day 0. We detected no genistein-induced rearrangements of the MLL gene in the 3 subjects we studied with this technique. MF increased significantly in lymphocytes exposed in vitro to unconjugated genistein at concentrations > or = 100 micromol/L. Total genistein never exceeded a peak concentration of 27.1 micro mol/L, and unconjugated genistein never exceeded a peak concentration of 0.32 micromol/L.

CONCLUSION

Although isoflavones are capable of inducing genetic damage in vitro, a similar effect was not observed in subjects treated with a purified soy unconjugated isoflavone mixture.

Soy extract inhibits mammary adenocarcinoma growth in a syngeneic mouse model

The effects of the soybean isoflavone genistein and a commercially-available isoflavone-containing soy extract on the growth of F3II mouse mammary adenocarcinoma cells were investigated. Female Balb/c mice injected (s.c.) with F3II cells and fed diets supplemented with 0.6% soy extract (containing genistein at 750 ppm) exhibited a significant 90% reduction in tumor weight compared to controls, whereas female mice fed diets supplemented with 750 ppm genistein alone exhibited a significant 40% reduction in tumor weight compared to controls. Tumor samples from animals fed the 0.6% soy extract, but not from those animals fed the 750 ppm genistein diet alone, exhibited significantly higher protein levels of the cyclin-dependent kinase inhibitor p21(waf1/cip1) compared to controls. Neither of the two experimental diets altered tumor estrogen receptor-alpha or progesterone receptor protein levels. In vitro, genistein significantly inhibited F3II cell proliferation (IC(50) approximately 2-3 microM) and caused a G2/M block in cell cycle progression at concentrations as low as 5 microM. This genistein-induced G2/M arrest in vitro was associated with a significant increase in the protein expression of phosphorylated p34(cdc2) and of cyclin B1. These results indicate that genistein is an inhibitor of F3II mouse mammary adenocarcinoma cell growth in vivo and in vitro, in part due to its effect on specific cell cycle regulatory proteins. In addition, genistein fed to mice as part of the soy extract resulted in a greater magnitude of inhibition of mouse mammary adenocarcinoma tumor growth, compared to tumor growth of animals fed an equivalent amount of genistein alone. This suggests that genistein along with other constituent(s) in the soy extract may also contribute to suppression of F3II tumor growth.

Anti-cancer effect of genistein in oral squamous cell carcinoma with respect to angiogenesis and in vitro invasion

Oral squamous cell carcinoma (OSCC) is one of the most common head and neck cancers. OSCC generally has a poor prognosis due to its tendency towards local invasion and subsequent metastasis, which is mediated by multiple proteolytic enzymes and angiogenesis. The purpose of this study was to evaluate the anti-cancer effects of genistein, a soybean product known to be an effective natural anti-angiogenic agent, with respect to tumor growth, angiogenesis and in vitro invasion in an OSCC model. Northern blot analysis for vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and matrix metalloproteinase-2 (MMP-2), in vitro invasion assay and gelatin zymography were carried out for HSC-3 cells treated with genistein (27.3 microg/ml). In the animal experiment, genistein (0.5 mg/kg) was injected into tumor (HSC-3)-bearing mice (male balb/c/nu). The tumor growth rate and metastasis to lymph node or lung were compared and the microvessel density (CD31) was subsequently analyzed by immunohistochemistry. The genistein-treated group showed a down-regulation in VEGF mRNA expression, but not in bFGF and MMP-2 mRNA expression. Genistein reduced in vitro invasion through the artificial basement membrane and gelatin zymography also showed a reduced gelatinolytic activity in the genistein-treated group. In the genistein-treated mice, a significantly lower CD31 immunoreactivity was found. However, the tumor growth and metastatic behavior in the experimental group and the control group were similar and there were no significant differences. These results suggest the possible use of genistein as an anti-cancer agent in oral squamous cell carcinoma. However, it appears from the present study that anti-angiogenic therapy consisting of a single application of genistein may not provide a satisfactory treatment for OSCC. As a result, further research is recommended to confirm that genistein may be employed as an adjunct treatment modality for OSCC.

Genistein and daidzein downregulate prostate androgen-regulated transcript-1 (PART-1) gene expression induced by dihydrotestosterone in human prostate LNCaP cancer cells

Epidemiologic investigations and laboratory studies suggest that bioactive soy phytochemical components may be used as an effective dietary regimen for prevention of prostate cancer. Studies designed to identify new genes that are responsive to androgens and are sensitive to the prevention of prostate cancer using soy bioactive components have become a research priority. In this study, we determined the effect of soy isoflavones on the expression of prostate androgen-regulated transcript 1 (PART-1), a newly discovered androgen-induced gene that may represent a novel androgen-dependent prostate cancer tumor marker. In an androgen-depleted cell culture system, 5alpha-dihydrotestosterone (DHT) induced expression of PART-1 transcript in androgen-sensitive LNCaP, but not in androgen-independent DU 145 or PC-3 human prostate cancer cells. The soy isoflavones genistein and daidzein dose-dependently inhibited DHT-induced expression of the PART-1 transcript. Genistein at 50 micro mol/L completely inhibited expression of the PART-1 transcript in LNCaP cells induced by DHT at 0.1 and 1.0 nmol/L. Daidzein was less potent than genistein, whereas glycitein at the same levels as genistein or daidzein did not inhibit DHT-induced PART-1 transcript expression. Our studies suggest that use of the PART-1 gene as a biomarker for evaluating the efficacy of soy isoflavones on androgen-dependent prostate cancer warrants further investigation.

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.

Genistein replacement therapy for vasodilation disorder in bilateral ovariectomized rats

The objective of this study is to examine the effects of genistein on endothelial dysfunction in bilateral ovariectomized rats. Female Wistar rats were subjected to a bilateral ovariectomy (OVX rat). The animals were divided into three groups: sham treated with vehicle (DMSO 100 microliters/day, Shamveh), OVX treated with vehicle (DMSO 100 microliters/day, OVXveh), and OVX treated with genistein (0.25 mg/kg BW/day, OVXgen). Mean arterial pressure (MAP), heart rate (HR), body weight (BW), uterine weight and plasma E2 were monitored at 4-week after the treatment. We investigated the endothelium-dependent and -independent vasorelaxation by using acetylcholine (Ach 10(-6) M) and sodium nitroprusside (SNP 10(-7) M), respectively. The experimental results indicated that the uterine weights of all OVX rats were significantly decreased as compared to the sham groups (OVXveh = 0.007+/-0.004 g, OVXgen =0.003+/-0.001 g, Shamveh =0.017+/-0.001 g). MAP of OVXveh group was significantly increased compared to the Sham group (OVXveh=139.99+/-7.50 mmHg, Shamveh =118.10+/-19.33 mmHg, p<0.05). No significant increase in MAP was observed in OVXgen (OVXgen =123.33+/-8.61 mmHg; p<0.05). HR showed no significant difference among those groups. The present study of vasodilator responses demonstrated only the significant decrease in endothelium-dependent, not for endothelium-independence, in OVX rats, while the treatment of genistein could significantly attenuate this abnormality (OVXveh =3.03+/-3.99%, Shamveh =45.46+/-3.59%, OVXgen =33.52+/-3.25% in % change of vessel diameter). The present findings suggest that genistein could be used as a therapeutic agent for menopausal vascular complications.

Genistein, a soy isoflavone, enhances necrotic-like cell death in a breast cancer cell treated with a chemotherapeutic agent

Genistein is a major component of soybean isoflavone and has preventive effect against breast cancer. In breast cancer, the over-expression of HER-2 contributes to malignant transformation of the cancer cells. The present study was undertaken to estimate if genistein could act as a useful anti-cancer agent against a breast cancer cell overexpressing HER-2 in combination with a conventional chemotherapy agent, adriamycin (ADR). Genistein enhanced cytotoxic effect of ADR at low doses less than IC50 against the human breast cancer cell. The enhancing effect was mainly dependent on the elevation of necrotic-like cell death but not apoptotic cell death. In conjugation with this event, remarkable inactivation of HER-2 and Akt in the breast cancer cell was caused by the combination of genistein and ADR. These results suggest that genistein enhances necrotic-like cell death of the breast cancer cells through the inactivation of HER-2 receptor and Akt in combination with ADR.

Down-regulation of invasion and angiogenesis-related genes identified by cDNA microarray analysis of PC3 prostate cancer cells treated with genistein

Prostate cancer is the second leading cause of cancer related deaths in men in the United States and for many years the treatment results for metastatic prostate cancer have been disappointing. Our previous studies have shown that genistein elicits pleiotropic effects on prostate cancer cells; however, its role in invasion and metastasis has not been fully elucidated. In order to better understand the precise molecular mechanism(s) by which genistein exerts its effects on PC3 cells, we have utilized cDNA microarray to interrogate 12558 known genes to determine the gene expression profile altered by genistein treatment. We found a total of 832 genes which showed >2-fold change after genistein treatment. Among these genes, we found down-regulation of 11 genes (MMP-9, protease M, uPAR, VEGF, neuropilin, TSP, BPGF, LPA, TGF-beta2, TSP-1, PAR-2) and up-regulation of two genes (connective tissue growth factor, connective tissue activation peptide), which are related to angiogenesis, tumor cell invasion and metastasis. Reverse transcription-polymerase chain reaction, Western blot, and zymographic analysis were conducted to confirm the data of microarray at the level of mRNA, protein, and biological function. The results were in direct agreement with the microarray data. From these results, we conclude that genistein down-regulates the transcription and translation of genes critically involved in the control of angiogenesis, tumor cell invasion and metastasis, suggesting the possible therapeutic role of genistein for metastatic prostate cancer. Thus, genistein-induced alternations of gene expressions may be exploited for devising chemopreventive or therapeutic strategies, particularly for chemosensitization of metastatic prostate cancer to existing chemotherapeutic agents.