Effects of genistein and equol on human and rat testicular 3β-hydroxysteroid dehydrogenase and 17β-hydroxysteroid dehydrogenase 3 activities

The objective of the present study was to investigate the effects of genistein and equol on 3β-hydroxysteroid de- hydrogenase （3β-HSD） and 17β-hydroxysteroid dehydrogenase 3 （17β-HSD3） in human and rat testis microsomes. These enzymes （3β-HSD and 17β-HSD3）, along with two others （cytochrome P450 side-chain cleavage enzyme and cytochrome P450 17α-hydroxylase/17-20 lyase）, catalyze the reactions that convert the steroid cholesterol into the sex hormone testosterone. Genistein inhibited 3β-HSD activity （0.2 μmol L^-1 pregnenolone） with half-maximal inhibition or a half-maximal inhibitory concentration （IC50） of 87 ± 15 （human） and 636 ± 155 nmol L^-1 （rat）. Genistein＇s mode of action on 3β-HSD activity was competitive for the substrate pregnenolonrge and noncompetitive for the cofactor NAD＋. There was no difference in genistein＇s potency of 3β-HSD inhibition between intact rat Leydig cells and testis microsomes. In contrast to its potent inhibition of 3β-HSD, genistein had lesser effects on human and rat 17β-HSD3 （0.1 μmol L^-1 androstenedione）, with an IC50 〉 100μmol L^-1. On the other hand, equol only inhibited human 3β-HSD by 42%, and had no effect on 3β-HSD and 17β-HSD3 in rat tissues. These observations imply that the ability of soy isoflavones to regulate androgen biosynthesis in Leydig cells is due in part to action on Leydig cell 3β- HSD activity. Given the increasing intake of soy-based food products and their potential effect on blood androgen levels, these findings are greatly relevant to public health.

Bioconversion of genistein to(–)-5-hydroxy-equol by a newly isolated cock intestinal anaerobic bacterium

A newly isolated bacterium, named as AUH-JLC257, was found to be capable of bioconverting isoflavone genistein to 5-hydroxy-equol under anaerobic conditions. The metabolite 5-hydroxy-equol was identified by using UV spectrum, electrospray ionization mass spectrometry （ESI-MS） as well as IH and 13C NMR analyses. Chiral stationary-phase high-performance liquid chromatography analysis and specific rotation examination demonstrated that the bio-synthesized 5-hydroxy-equol was just （-）-5-hydroxy-equol. The average bioconverting rate was 83.1%, and the strain AUH-JLC257 could efficiently transform genistein at a maximal substrate concentration of 0.6 mmol/L. We, for the first time, showed that the bio-synthesized 5-hydroxy-equol had 1,1-diphenyl-2-picrylhydrazyl （DPPH） radical-scavenging activity at concentrations as low as 3.3μmol/L. In addition, the 16S rRNA gene sequence （1401 bp） of the bacterium strain AUH-JLC257 showed the highest similarity （99.27%） to that of Slackia equolifaciens strain DZE.

Equol inhibits proliferation of human gastric carcinoma cells via modulating Akt pathway

AIM: To investigate the anti-tumor effects of equol in gastric cancer cells and the underlying molecular mechanisms.METHODS: MGC-803 cells were employed for in vitro experiments in this study. Cells were treated with control(vehicle,0.1% DMSO) or equol under specified dose titration or time courses. Cell viability was examined by MTS assay,and the levels of Ki67 were determined by q PCR and immunofluorescent assay. Changes in cell cycle distribution and apoptosis rate were detected by flow cytometry. The m RNA expression of cyclin E1 and P21WAF1 was determined by q PCR. The protein levels of cell cycle regulators,PARP and Caspase-3 cleavage,and the phosphorylation of Akt were examined by Western blot. In addition,to characterize the role of elevated Akt activation in the anti-tumor effect exerted by equol,Ly294002,a PI3K/AKT pathway inhibitor,was used to pretreat MGC-803 cells. RESULTS: Equol(5,10,20,40,or 80 μmol/L) inhibited viability of MGC-803 cells in a dose- and timedependent manner after treatment for 24,36,or 48 h(P < 0.05 for all). Equol also decreased the m RNA(P <0.05 for 12 and 24 h treatment) and protein levels of Ki67. Equol treatment significantly induced G0/G1 cell cycle arrest(P < 0.05),with the percentages of G0/G1 cells of 32.23% ± 3.62%,36.31% ± 0.24%,45.58% ± 2.29%,and 65.10% ± 2.04% for equol(0,10,20,or 30 μmol/L) treatment,respectively,accompanied by a significant decrease of CDK2/4(P < 0.05 for 24 and 48 h treatment) and Cyclin D1/Cyclin E1(P < 0.05),and an increased level of P21WAF1(P < 0.05). A marked increase of apoptosis was observed,with the percentages of apoptotic cells of 5.01% ± 0.91%,14.57% ± 0.99%,37.40% ± 0.58%,and 38.46% ± 2.01% for equol(0,5,10,or 20 μmol/L) treatment,respectively,accompanied by increased levels of cleaved PARP and caspase-3. In addition,we found that equol treatment increased P-Akt(Ser473 and Thr308) at 12 and 24 h compared to vehicle-treated control; longer treatment for 48 h decreased P-Akt(Ser473 and Thr308). P-Akt at Thr450,however,was decreased by equol treatment at all time points examined(P < 0.05 for all). Moreover,Akt inhibition by Ly294002 could not prevent but led to enhanced G0/G1 arrest and apoptosis. CONCLUSION: Equol inhibits MGC-803 cells proliferation by induction of G0/G1 arrest and apoptosis. Its anti-cancer effects are likely mediated by dephosphorylation of Akt at Thr450.

<i>In Vitro</i>Effect of Soy Isoflavone and Equol on Soluble CD40L Release Stimulated by Ristocetin in Platelets from Postmenopause Women

The inhibition of specific flavonoid on the in vitro platelet aggregation induced by collagen, arachidonic acid and thromboxane A2 (TxA2) agonist, seems to be related mostly to their ability to compete for binding to the TxA2 receptor (TP). The aim of this study was to analyze the effect of soy isoflavone and equol in terms of inhibiting the platelet aggregation and sCD40L release stimulated by ristocetin, an in vitro-activator of glycoprotein Ib/IX/V, in platelets from postmenopausal women. When platelets were stimulated by 0.75 mg/ml ristocetin, equol (10 μM) exhibited a greater inhibitory activity on platelet aggregation (~68%) than genistein or daidzein. The effect of equol was dependent on the concentration of platelet aggregation agonist. In the presence of ristocetin (0.75 mg/ml, 1.125 mg/ml and 1.5 mg/ml), the inhibitory effect of 10 μM equol was 68% ± 5%, 54% ± 4% and 31% ± 5%, respectively. Equol (10 μM) was a potent inhibitor (~35%) of sCD40L release when stimulated with 1.5 mg/ml ristocetin. However, no significant differences were noted in platelets incubated in the presence of genistein or daidzein and stimulated by ristocetin. On the other hand, SQ29548, a high TP antagonist, also inhibited the sCD40L release stimulated by ristocetin. Finally, 10 μM of genistein, daidzein or equol did not significantly affect the thromboxane B2 production when platelets were incubated with 1.5 mg/ml ristocetin. The relevance of this study was to find that equol exhibits a potent activity by inhibiting ristocetin-induced sCD40L release, suggesting that soy isoflavone has important biological effects on the hemostatic system. However, clinical trials will be necessary to assess the effect of equol on platelet and their impact on inflammatory markers.

Severe &Moderate BPH Symptoms in Mid-Aged Men Improve with Isoflavonoid-Equol Treatment: Pilot Intervention Study

Benign prostatic hyperplasia (BPH) is the pathological cellular progression of glandular proliferation associated with aging. Current available treatment options for BPH have limitations and various adverse effects. Equol is a polyphenolic/isoflavonoid molecule derived from intestinal metabolism, dairy and dietary plant sources. It has the unique characteristic to bind specifically 5α-dihydrotestosterone (5α-DHT) by sequestering 5α-DHT from the androgen receptor, thus decreasing androgen hormone actions to improve prostate health by acting as a selective androgen modulator (SAM). It also has affinity for estrogen related receptor gamma (ERR-γ) and estrogen receptor beta (ER-β) within the prostate that is known to improve male health via selective estrogen receptor modulatory (SERM) activities to decrease inflammation, cellular proliferation and carcinogenesis. We investigated the possible clinical efficacy of equol on the symptoms associated with benign prostatic hyperplasia (BPH) in this study. Materials and Methods: We performed a pilot intervention study evaluating the effects of low dose oral equol supplement (6 mg, twice a day with meals) for 4 weeks in a total of 18 men (49 - 60 years old) with moderate or severe BPH. Subjects included in the study: gave informed consent, underwent a physical examination and verified their BPH symptoms as measured by the International Prostate Symptom Scores (IPSS) and then were assigned to the moderate or severe BPH groups based upon their total IPSS index. All adverse events were reported. The primary efficacy measure was the IPSS parameters comparing baseline to 2 and 4 week IPSS indices. Blood samples were collected at the baseline and 4th week visits that served as secondary efficacy parameters that included testosterone, 5α-DHT and general blood chemistries along with cardiac and hepatic function panels. Results: Low dose equol positively improved moderate to severe BPH symptoms according to the IPSS indices. In moderately symptomatic men (n = 10) 5 out of 7 of the IPSS parameters significantly improved by 4 weeks of equol treatment. In severely symptomatic men (n = 8) all 7 of the IPSS parameters significantly improved with 4 weeks of equol treatment. There were no significant changes in androgen levels, general blood chemistries or cardiac and hepatic function parameters. Although, 5α-DHT levels declined by 21% in severely symptomatic men (from baseline vs. 4 week values). Conclusion: These findings suggest that equol may provide a well tolerated and rapid beneficial therapy for BPH that can be used alone or in combination with current pharmaceutical therapies. The beneficial clinical efficacy of equol observed in this study may be due to the multiple positive biological actions that are not present in current pharmaceutical treatments.

Maternal Genistein Intake Can Reduce Body Weight in Male Offspring

The study objectives were to investigate the relationship between early exposure to genistein and obesity in young adulthood and to evaluate changes in reproductive health during puberty and adulthood following in utero exposure to genistein.

Oxidative Metabolism of Estrone Modified by Genistein and Bisphenol A in Rat Liver Microsomes

Genistein, the main isoflavone from soy, and bisphenol A （BPA）, a food contaminant, are considered ubiquitous xenoestrogens. Here we investigated the influence of genistein and BPA on estrone （El） metabolism in rat liver microsomes. Both substances inhibited the 2-hydroxylation and 16a-hydroxylation of E1, but in different degrees, thereby reducing the 2-OH-E1/16a-OH-E1 ratio,

Review: Anti-Oxidant and Anti-Aging Properties of Equol in Prostate Health (BPH)

Benign prostatic hyperplasia (BPH) is the pathological cellular progression of glandular proliferation associated with aging. The primary changes in prostate disorders are mediated by the conversion of the principle androgen, testosterone, to its more potent metabolite, 5α-dihydrotestosterone (5α-DHT). However, recent evidence suggests that estrogen hormonal actions via estrogen receptor subtypes also play an important role in BPH. Current pharmaceutical options for BPH have advantages, limitations and adverse effects. Complementary and Alternative Medicine (CAM) treatments for BPH include botanicals such as polyphenols and isoflavones. Equol is a polyphenolic/isoflavonoid molecule derived from intestinal metabolism, dairy and dietary plant sources. Equol has potent anti-oxidant and anti-aging properties to decrease prostatic irritation and potentially neoplastic growth. It has the unique characteristic to bind specifically 5α-DHT by sequestering 5α-DHT from the androgen receptor (AR), thus decreasing androgen hormone actions to improve prostate health by acting as a selective androgen modulator (SAM). It also has affinity for estrogen related receptor gamma (ERR-γ) and estrogen receptor beta (ER-β) within the prostate that is known to improve male health via selective estrogen receptor modulatory (SERM) activities to decrease inflammation, cellular proliferation and carcinogenesis. The possible clinical efficacy of equol on the symptoms associated with BPH is presented and the reviewed findings suggest that equol may provide a well-tolerated and rapid beneficial therapy for BPH that can be used alone or in combination with current pharmaceutical therapies. The beneficial clinical efficacy of equol observed may be due to the multiple positive biological actions that are not present in current pharmaceutical treatments.

Correlation of Equol (7-Hydroxy-3-(4-Hydroxyphenyl)Chroman) in Woman Urine with the Symptoms of Menopause

Objective: In order to identify the correlation between equol excreted through human urine and the symptom of menopause. Methods: The method used is cross sectional study examined to 99 postmenopausal women fulfilling the inclusion criteria from February 2014 to July 2014. This research was taken in the Endocrinology Clinic, Department of Obstetrics and Gynecology, Hasan Sadikin Hospital and Unpad’s Pharmacokinetic Laboratory. All objects were interviewed using menopause rating scale (MRS) questionnaire. Their urine samples were analyzed using high performance liquid chromatography (HPLC). Then the results of questionnaire and HPLC test were evaluated. Results: The result is 97 objects (98%) detected having menopausal symptoms, produced equol. There is significant correlation between the level of equol in post-menopausal women that showed correlation (-0.71) which mean the higher the equol level, the lower the MRS score (p < 0.001) that mean the symptom is milder. Conclusion: Equol level in menopause women urine is a good predictor to identify the level of menopause symptoms.

Antifibrotic Effects of Genistein and Quercetin In Vitro

Objective: To study the antifibrotic effects of genistein(GE) and quercetin(QU) on rat hepatic stellate HSC-T6 cell proliferation stimulated with platelet-derived growth factor (PDGF), collagen synthesis and type I procollagen messenger RNA (mRNA) expression stimulated with transforming growth factor b1 (TGFb1). Methods: Cell proliferation was measured by crystal violet staining assay. Collagen synthesis was determined by 3H-proline incorporation assay. Type I procollagen mRNA level was determined by reverse transcription polymerase chain reaction (RT-PCR). Results: GE (25~70 mmolL-1) and QU (6.25~50 mmolL-1) concentration-dependently attenuated PDGF-driven HSC-T6 cell proliferative activity. TGFb1-stimulated collagen synthesis was also reduced. This was associated with a decrease in type I procollagen mRNA expression, indicating an effect at a pretranslational level. Conclusion: GE and QU may have therapeutic potential against liver fibrosis by regulating PDGF and TGFb1 actions.

The Development of S-Equol Diastereoisomer Specific ELISA

Equol is a metabolite of soybean isoflavone, daidzein, and many health benefits are expected. Endogenous equol in urine is S-equol and mostly exists as glucuronate or sulfate conjugate. In this study we preliminary established the simple enzyme-linked immunosorbent assay (ELISA) without deconjugation, then developed the S-equol specific ELISA involves deconjugation showing high stereospecificity to S-equol without using stereospecific antibody. For the simple ELISA, we used a polyclonal antibody that targets the regions not influenced by inhibition by conjugation of glucuronate and sulfate and achieved the correlation coefficient;r = 0.975, but the value was 30 % lower than high performance liquid chromatography (HPLC). Developing upon this we invented the specific ELISA established from S-equol homogeneous combination for the standard and enzyme-labeled antigen to enhance stereospecificity. The correlation with HPLC was favorable: r = 0.986, y = 0.996x – 6. Compared to the previous method using (R,S)-equol combination, cross-reactivity with R-equol was reduced from 65 to 13 %, and that with daidzein from 0.31% to 0.08%, markedly increased in the specificity. This study is expected to be applied for both simple clinical researches, and stereospecific immunoassays in which specific antibody preparation is difficult.

Determination of Genistein in the Fermented By-product of Soybean Curd, an Indonesian Food, and Its in vivo Assay on Carrageenan-lnduced Mice

In our country, Indonesia, especially in West Java, people frequently consume fermented by-product of soybean curd for their main course. The by-product of curd, usually is discarded, can be fermented using either Neurospora （Neurospora sitophila） or Rhizopus （Rhizopus oligosporus） yeast to make oncom Genistein is a phytoestrogen, an estrogen-like chemical compound present in plants, that has anti-inflammatory property. Genistein can be determined by UV spectrophotometric method based on the UV absorbance of its complex with aluminum chloride. Addition of acid is a critical point in the procedure. The aim of this research was to know whether genistein is still contained in oncom This research also studied about oncom＇s activity on carrageenan-induced mice. Acetosal was used as drug control. Result showed that genistein was detected contained in oncom extract. The in vivo assay indicated that oncom extract （dose 1,000 mg/kg of body weight） reduced oedema in carragenan-induced paw of mice, which potencies were 066 times lower than that of acetosal＇s. Oncom might be useful as food and as a weak inflammation reducer as well.

雌马酚(S-equol, Eq)对慢性不可预知温和刺激小鼠抑郁样行为的改善作用

为探究雌马酚(S-equol, Eq)对慢性不可预知温和刺激抑郁模型(Chronic Unpredictable Mild Stress, CUMS)小鼠的改善作用,试验设空白组(Con)、模型组(CUMS)、雌马酚低剂量组(Eq-L,10 mg·kg-1)、雌马酚中剂量组(Eq-M,20 mg·kg-1)和雌马酚高剂量组(Eq-H,40 mg·kg-1),在预防给药14 d后,对模型组和雌马酚组进行CUMS造模刺激,造模42 d之后监测体重,依次进行空场、糖水偏爱、悬尾、强迫游泳和新奇抑制摄食5种行为学试验,并检测血清中皮质酮(CORT)水平。行为学结果显示:与空白组相比,CUMS模型组小鼠的自主活动能力未受到显著影响,体重和糖水偏爱指数显著下降,悬尾、强迫游泳中不动时间和新奇抑制摄食潜伏期显著延长;与模型组相比,雌马酚没有影响小鼠的自主活动,显著提高了小鼠的糖水偏爱指数,缩短了悬尾、强迫游泳不动时间和新奇抑制摄食潜伏期。此外,CUMS模型组小鼠血清中CORT显著上调,雌马酚给药显著改善上述异常指标。该结果表明雌马酚可以改善CUMS小鼠抑郁样行为,并通过抑制下丘脑-垂体-肾上腺轴的过度亢进发挥改善抑郁的作用。

Effect of genistein supplementation of thawing medium on characteristics of frozen human spermatozoa

In this study, we evaluated the effects of genistein supplementation of the thawing extender on frozen-thawed human semen parameters. We analyzed the effect of supplementation on sperm motility, capacitation （membrane lipid disorder）, reactive oxygen species （ROS） generation, chromatin condensation and DNA damage. Using this preliminary information, it maybe possible to improve the cryopreservation process and reduce the cellular damage. We have confirmed that the isoflavone genistein （10 μmol L-1） has antioxidant properties on the frozen-thawed spermatozoa. This results in a decreased ROS production that shows a slight improvement in the sperm motility, and decreases the membrane lipid disorder and DNA damage caused by cryopreservation. These results suggest an effect of genistein on sperm functionality that could be of interest for assisted reproduction treatments using frozen- thawed human spermatozoa, but further studies will be necessary to confirm our findings and to evaluate the possible clinical applications.

Combination of genistein with ionizing radiation on andro-gen-independent prostate cancer cells

Aim: To study the effect of the combined use of genistein and ionizing radiation (IR) on prostate DU145 cancer cells. Methods: DU145, an androgen-independent human prostate cancer cell line, was used in the experiment. Clonogenic assay was used to compare the survival of DU145 cells after treatments with genistein alone and in combination with graded IR. Apoptosis was assayed by DNA ladder and TUNEL stain. Cell cycle alterations were observed by flow cytometry and related protein expressions by immunoblotting. Results: Clonogenic assay demonstrated that genistein, even at low to medium concentrations, enhanced the radiosensitivity of DU145 cells. Twenty-four hours after treatment with IR and/or genistein, apoptosis was mainly seen with genistein at high concentrations and was minimally related to IR. At 72 h, apoptosis also occurred in treatment with lower concentration of genistein, especially when combined with IR. While both IR and genistein led to G2/M cell cycle arrest, combination of them further increased the DU145 cells at G2/M phase. This Gz/M arrest was largely maintained at 72 h, accompanied by increasing apoptosis and hyperdiploid cell population. Cell-cycle related protein analysis disclosed biphasic changes in cyclin B1 and less dramatically cdc-2, but stably elevated p21cipl levels with increasing genistein concentrations. Conclusion: Genistein enhanced the radiosensitivity of DU145 prostate cancer cells. The mechanisms might be involved in the increased apoptosis, prolonged cell cycle arrest and impaired damage repair.

Effects of genistein on neuronal apoptosis,and expression of Bcl-2 and Bax proteins in the hippocampus of ovariectomized rats

Genistein is one of several isoflavones that has a structure similar to 17β-estradiol, has a strong antioxidant effect, and a high affinity to estrogen receptors. At 15 weeks after ovariectomy, the expression of Bcl-2 in the hippocampus of rats decreased and Bax expression increased, with an obvious upregulation of apoptosis. However, intraperitoneal injection of genistein or 17β-estradiol for 15 consecutive weeks from the second day after operation upregulated Bcl-2 protein expression downregulated Bax protein expression, and attenuated hippocampal neuron apoptosis. Our experimental findings indicate that long-term intervention with genistein can lead to a decrease in apoptosis in hippocampal neurons following ovadectomy, upregulate the expression of Bcl-2, and downregulate the expression of Bax. In addition, genistein and 17β-estradiol play equal anti-apoptotic and neuroprotective roles.

Synthesis and Crystal Structure of a Genistein-derived Compound

A genistein derivative, 5-hydroxy-3-（4-hydroxyphenyl）-7-（2-（piperidin- 1-yl）ethoxy）- 4H-chromen-4-one 3, was designed, prepared and structurally characterized by single-crystal X-ray diffraction. X-ray structure analysis reveals that 3 crystallizes in the orthorhombic system, space group Pbca, with a = 16.238（3）, b = 10.308（2）, c = 22.987（5）A, V = 3847.6（13）A3, Z = 8,μ= 0.093 mm^-1, Dc = 1.317 g/cm^3, F（000） = 1616, R = 0.0789 and wR = 0.1554 for 1463 observed reflections with I 〉 2σ（I）.

Blocking effects of genistein on cell proliferation and possible mechanism in human gastric carcinoma

AIM: To study the blocking effects of genistein on cell proliferation cycle in human gastric carcinoma cells (SGC-7901) and the possible mechanism. METHODS: MTT assay was applied in the detection of the inhibitory effects of genistein on cell proliferation. Flow cytometry was used to analyze the cell cycle distribution. Immunocytochemical technique and Western blotting were performed to detect the protein expression of cyclin D_1, cyclin B_1 and p21^(waf1/cip1). RESULTS: Genistein significantly inhibited the growth and proliferation of human gastric carcinoma cells (SGC-7901). Seven days after treatment with different concentrations of genistein (2.5, 5.0, 10.0, 20.0 μg/mL), the growth inhibitory rates were 11.2%, 28.8%, 55.3%, 84.7% respectively and cell cycles were arrested at the G(2)/ M phase. Genistein decreased cyclin D_1 protein expression and enhanced cyclin B_1 and p21^(waf1/cip1) protein expression in a concentration-dependent manner. CONCLUSION: The growth and proliferation of SGC-7901 cells can be inhibited by genistein via blocking the cell cycle, with reduced expression of cyclin D_1 and enhanced expression of cyclin B_1 and p21^(waf1/cip1) protein in the concentration range of 0-20 μg/mL.

Synthesis, Characterization and Antioxidative Activity of Lanthanide Complexes with Genistein

Six genistein lanthanide complexes, LnL_2 (OAc)·nH_2O [Ln=La(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), (Tb(Ⅲ),) Dy(Ⅲ); L=genistein; n=4, 7, 8] were synthesized and characterized on the basis of elemental analyses, IR, (()~1H) NMR spectra and molar conductivity. The scavenging activity of genistein and five lanthanides complexes on the hydroxyl free radicals (OH·) was also investigated by spectrophotometric methods. The results show that the scavenging activity of the complexes is better than that of the ligand and their scavenging ability can be assembled in the following order: Sm>La>Dy>Eu>Tb>L.

Anticancer activity of genistein on implanted tumor of human SG7901 cells in nude mice

AIM： To investigate genistein-induced apoptosis of implanted tumors of SG7901 cells in nude mice, and the relationship between this apoptosis and expression of Bcl-2 and Bax. METHODS： Establishing a transplanted tumor model by injecting human SG7901 cells into subcutaneous tissue of nude mice. Genistein （0.5, 1 and 1.5 mg/kg） was directly injected adjacent to the tumor, six times at 2-d intervals. Then, changes in tumor volume were measured continuously and tumor inhibition rate of each group was calculated. We observed the morphological alterations by transmission electron microscopy （TEN）, measured the apoptotic rate by the TUNEL staining method, and detected the expression of apoptosisregulated gene Bcl-2 and bax by immunohistochemical staining and RT-PCR. RESULTS： Genistein 0.5, 1 and 1.5 mg/kg significantly inhibited carcinoma growth when it was injected near the tumor by 10.8%, 29.9% and 39.6%, respectively. Genistein induced implanted tumor cells to undergo apoptosis, with apoptotic characteristics seen by TEM. The apoptosis index was increased progressively with increasing genistein dose （28.9% ± 1.2%, 33.8% ±1.6% and 37.7% ±1.2%）. The positive rate of Bcl-2 protein was decreased progressively （11.9%± 0.9%, 5.9%± 0.7% and 4.2% ±0.6%）, and the positive rate of bax protein was increased progressively （0.9% ±1.7%, 24.9% ±0.8% and 29.6% ± 1.7%） by immunohistochemical staining, with increasing dose of genistein. The density of Bcl-2 mRNA decreased progressively and the density of bax mRNA increased progressively with elongation of time by RT-PCR. CONCLUSION： Genistein was able to induce apoptosisof transplanted tumor cells. This apoptosis may be mediated by down-regulation of the apoptosis-regulated gene Bcl-2 and up-regulation of apoptosis-regulated gene bax.