Equol induces apoptosis in human hepatocellular carcinoma SMMC-7721 cells through the intrinsic pathway and the endoplasmic reticulum stress pathway. Anticancer Drugs. 2014;25:633-640. [PMID: 24487643 DOI: 10.1097/cad.0000000000000085]

Protective Effect of Daidzein against Diethylnitrosamine/Carbon Tetrachloride-Induced Hepatocellular Carcinoma in Male Rats

Hepatocellular carcinoma (HCC) is the second-largest cause of death among all cancer types. Many drugs have been used to treat the disease for a long time but have been mostly discontinued because of their side effects or the development of resistance in the patients with HCC. The administration of DZ orally is a great focus to address the clinical crisis. Daidzein (DZ) is a prominent isoflavone polyphenolic chemical found in soybeans and other leguminous plants. It has various pharmacological effects, including anti-inflammatory, antihemolytic, and antioxidant. This present study investigates the protective effect of DZ on chemically induced HCC in rat models. The DZ was administered orally four weeks before HCC induction and continued during treatment. Our study included four treatment groups: control (group 1, without any treatment), HCC-induced rats (group II), an HCC group treated with DZ at 20 mg/kg (group III), and an HCC group treated with DZ at 40 mg/kg (group IV). HCC rats showed elevation in all the HCC markers (AFP, GPC3, and VEGF), liver function markers (ALP, ALT, and AST), inflammatory markers (IL-6, TNF-α, and CRP), and lipid markers concomitant with a decrease in antioxidant enzymes and protein. However, groups III and IV demonstrated dose-dependent alleviation in the previous parameters resulting from HCC. In addition, the high dose of DZ reduces many hepatological changes in HCC rats. All study parameters improved with DZ administration. Due to its antioxidant and anti-inflammatory characteristics, DZ is a promising HCC treatment option for clinical use.

Galectin-9 in Gastroenterological Cancer

Immunochemotherapy has become popular in recent years. The detailed mechanisms of cancer immunity are being elucidated, and new developments are expected in the future. Apoptosis allows tissues to maintain their form, quantity, and function by eliminating excess or abnormal cells. When apoptosis is inhibited, the balance between cell division and death is disrupted and tissue homeostasis is impaired. This leads to dysfunction and the accumulation of genetically abnormal cells, which can contribute to carcinogenesis. Lectins are neither enzymes nor antibodies but proteins that bind sugar chains. Among soluble endogenous lectins, galectins interact with cell surface sugar chains outside the cell to regulate signal transduction and cell growth. On the other hand, intracellular lectins are present at the plasma membrane and regulate signal transduction by regulating receptor–ligand interactions. Galectin-9 expressed on the surface of thymocytes induces apoptosis of T lymphocytes and plays an essential role in immune self-tolerance by negative selection in the thymus. Furthermore, the administration of extracellular galectin-9 induces apoptosis of human cancer and immunodeficient cells. However, the detailed pharmacokinetics of galectin-9 in vivo have not been elucidated. In addition, the cell surface receptors involved in galectin-9-induced apoptosis of cancer cells have not been identified, and the intracellular pathways involved in apoptosis have not been fully investigated. We have previously reported that galectin-9 induces apoptosis in various gastrointestinal cancers and suppresses tumor growth. However, the mechanism of galectin-9 and apoptosis induction in gastrointestinal cancers and the detailed mechanisms involved in tumor growth inhibition remain unknown. In this article, we review the effects of galectin-9 on gastrointestinal cancers and its mechanisms.

Gut Microbiota-Assisted Synthesis, Cellular Interactions and Synergistic Perspectives of Equol as a Potent Anticancer Isoflavone

It is well known that, historically, plants have been an important resource of anticancer agents, providing several clinically approved drugs. Numerous preclinical studies have shown a strong anticancer potential of structurally different phytochemicals, including polyphenolic constituents of plants, flavonoids. In this review article, suppressing effects of equol in different carcinogenesis models are unraveled, highlighting the mechanisms involved in these anticancer activities. Among flavonoids, daidzein is a well-known isoflavone occurring in soybeans and soy products. In a certain part of population, this soy isoflavone is decomposed to equol under the action of gut microflora. Somewhat surprisingly, this degradation product has been shown to be more bioactive than its precursor daidzein, revealing a strong and multifaceted anticancer potential. In this way, it is important to bear in mind that the metabolic conversion of plant flavonoids might lead to products that are even more efficient than the parent compounds themselves, definitely deserving further studies.

4-phenylbutyric acid promotes hepatocellular carcinoma via initiating cancer stem cells through activation of PPAR-α

Background and aims

4‐phenylbutyric acid (4‐PBA) is a low molecular weight fatty acid that is used in clinical practice to treat inherited urea cycle disorders. In previous reports, it acted as a chemical chaperone inhibiting endoplasmic reticulum (ER) stress and unfolded protein response signaling. A few studies have suggested its function against hepatic fibrosis in mice models. However, its role in hepatocarcinogenesis remained unknown.

Methods

4‐PBA was administered alone or in combination with diethylnitrosamine to investigate its long‐term effect on liver tumorigenesis. The role of 4‐PBA in oncogene‐induced hepatocellular carcinoma (HCC) mice model using sleeping beauty system co‐expressed with hMet and β‐catenin point mutation (S45Y) was also observed. RNA‐seq and PCR array were used to screen the pathways and genes involved. In vitro and in vivo studies were conducted to explore the effect of 4‐PBA on liver and validate the underlying mechanism.

Results

4‐PBA alone didn't cause liver tumor in long term. However, it promoted liver tumorigenesis in HCC mice models via initiation of liver cancer stem cells (LCSCs) through Wnt5b‐Fzd5 mediating β‐catenin signaling. Peroxisome proliferator‐activated receptors (PPAR)‐α induced by 4‐PBA was responsible for the activation of β‐catenin signaling. Thus, intervention of PPAR‐α reversed 4‐PBA‐induced initiation of LCSCs and HCC development in vivo. Further study revealed that 4‐PBA could not only upregulate the expression of PPAR‐α transcriptionally but also enhance its stabilization via protecting it from proteolysis. Moreover, high PPAR‐α expression predicted poor prognosis in HCC patients.

Conclusions

4‐PBA could upregulate PPAR‐α to initiate LCSCs by activating β‐catenin signaling pathway, promoting HCC at early stage. Therefore, more discretion should be taken to monitor the potential tumor‐promoting effect of 4‐PBA under HCC‐inducing environment.

Soy-Induced Fecal Metabolome Changes in Ovariectomized and Intact Female Rats: Relationship with Cardiometabolic Health

Phytoestrogens are plant-derived compounds found in a variety of foods, most notably, soy. These compounds have been shown to improve immuno-metabolic health, yet mechanisms remain uncertain. We demonstrated previously that dietary phytoestrogen-rich soy (SOY) rescued metabolic dysfunction/inflammation following ovariectomy (OVX) in female rats; we also noted remarkable shifts in gut microbiota in SOY vs control diet-fed rats. Importantly, specific bacteria that significantly increased in those fed the SOY correlated positively with several favorable host metabolic parameters. One mechanism by which gut microbes might lead to such host effects is through production of bacterial metabolites. To test this possibility, we utilized non-targeted gas chromatography-mass spectrometry (GCMS) to assess the fecal metabolome in those previously studied animals. Partial least square discriminant analysis (PLSDA) revealed clear separation of fecal metabolomes based on diet and ovarian state. In particular, SOY-fed animals had greater fecal concentrations of the beneficial bacterial metabolite, S-equol, which was positively associated with several of the bacteria upregulated in the SOY group. S-equol was inversely correlated with important indicators of metabolic dysfunction and inflammation, suggesting that this metabolite might be a key mediator between SOY and gut microbiome-positive host health outcomes.

Ethylacetate extract from Tetrastigma hemsleyanum inhibits proliferation and induces apoptosis in HepG2 and SMMC-7721 cells

PURPOSE

This study aimed to investigate the effect of ethylacetate extract from Tetrastigma hemsleyanum (EET) on the proliferation and apoptosis of HepG2 and SMMC-7721 cells and determine the underlying mechanisms.

MATERIALS AND METHODS

HepG2 and SMMC-7721 cells were cultured in vitro until the exponential growth phase and then treated with different concentrations of EET for 24 h. We performed a colony forming assay to determine colony forming ability, CCK8 assay to detect cell proliferation, Annexin V-FITC/PI double staining to analyze cell apoptosis, and Western blot to measure the protein expression of Caspase-3, Bcl-2, and Bax.

RESULTS

EET significantly inhibited the proliferation of HepG2 and SMMC-7721 cells in a concentration- and time-dependent manner (P<0.05). After treatment with 0, 50, 100, 150, 200, and 250 μg/mL EET for 24 h, HepG2 the proliferation rates were 100.00%±0.00%, 90.33%±1.76%, 67.67%±0.88%, 47.33%±0.88%, 37.00%±0.00%, and 30.33%±0.67%, respectively, and 100.00%±0.00%, 18.25%±1.05%, 19.99%±0.59%, 23.42%±0.46%, 29.70%±0.79%, and 29.8%±0.41% for SMMC-7721 cells, respectively. After treatment with 0, 50, 100, 150, 200, and 250 μg/mL EET for 24 h, the apoptotic rates were 11.08%±0.72%, 27.44%±0.51%, 32.92%±0.41%, 26.20%±0.47%, 22.92%±0.24%, and 55.60%±0.08%, for HepG2 cells, respectively, and 59.18%±0.17%, 41.24%±2.05%, 52.54%±0.39%, 50.54%±1.08%, and 57.44%±1.93% for SMMC-7721 cells, respectively. Compared with the treatment groups, the control group showed a significantly lower apoptotic rate (47.91%±1.09%, P<0.05). EET at the different concentrations downregulated the protein expression of Caspase-3 in HepG2 cells and upregulated it in SMMC-7721 cells; it also downregulated the protein expression of Bcl-2 in HepG2 and SMMC-7721 cells and upregulated the protein expression of Bax in HepG2 and SMMC-7721 cells.

CONCLUSION

These findings suggest that EET exerts antiproliferative and proapoptotic effects against HepG2 and SMMC-7721 cells mediated by downregulation or upregulation of Caspase-3 expression. Our study may help to develop EET for the pharmacological treatment of hepatoblastoma or hepatocellular carcinoma.

Daidzein induces choriocarcinoma cell apoptosis in a dose-dependent manner via the mitochondrial apoptotic pathway

Choriocarcinoma is a malignant gestational trophoblastic disease and relapse or drug resistance occurs in ~25% of gestational trophoblastic tumors. Cell apoptosis serves a role in the progression from hydatidiform mole to persistent gestational trophoblastic disease. It has been demonstrated that daidzein [7‑hydroxy‑3‑(4‑hydroxyphenyl)‑4H‑chromen‑4‑one] may induce apoptosis in a number of cancer types via the mitochondrial apoptotic pathway by altering the B‑cell lymphoma (Bcl)‑2/Bcl‑2 associated X, apoptosis regulator (Bax) ratio, and activating the caspase cascade. Daidzein also serves a role in regulation of production of human chorionic gonadotropin in trophoblast cells and inhibition of cell proliferation. However, few reports have been published regarding the effect of daidzein on apoptosis in choriocarcinoma. Therefore, in the present study, JAR and JEG‑3 human gestational choriocarcinoma cells were used to investigate the effect of daidzein on apoptosis of choriocarcinoma cells. Treatment with daidzein for 48 h reduced cell viability in a dose‑dependent manner. The percentages of early and late apoptotic cells also increased following treatment with daidzein in a dose‑dependent manner, with the number of late apoptotic cells increasing more prominently. Furthermore, treatment with daidzein led to apoptosis‑associated alterations in nuclear morphology of JAR and JEG-3 cells. Expression levels of cleaved poly(ADP‑ribose) polymerase, cleaved caspase‑3 and cleaved caspase‑9 increased following treatment with daidzein, whereas the Bcl‑2/Bax ratio decreased in a dose‑dependent manner. In conclusion, the results of the present study demonstrate that daidzein may induce apoptosis of choriocarcinoma cells in a dose‑dependent manner via the mitochondrial apoptotic pathway.

Equol Enhances Apoptosis-inducing Activity of Genistein by Increasing Bax/Bcl-xL Expression Ratio in MCF-7 Human Breast Cancer Cells

Anticancer activities of soy isoflavones, such as genistein and equol, a bioactive metabolite of daidzein, have been extensively studied because of possible involvement in the prevention of breast cancer. However, their interactions still remain unclear. We investigated here whether cytotoxic activity of genistein was enhanced by equol, using estrogen receptor positive MCF-7, HER2-positive SK-BR-3, and triple-negative MDA-MB-468 cell lines. Although cytotoxicity of genistein did not significantly differ between three subtypes of breast cancer cells, cytotoxic activities of genistein were significantly enhanced in combination with 50 μM equol in MCF-7 cells, but not in SK-BR-3 and MDA-MB-468 cells. In fluorescence activated cell sorting (FACS) analyses, MCF-7 cells were arrested at the G2/M by genistein but at G1/S by equol. Combination treatment arrested cells at G2/M but abolished equol-induced G1 block, indicating an antagonistic activity of genistein against equol in cell-cycle progression. Although apoptosis was not so evident with genistein alone, the combination made a drastic induction of apoptosis, accompanied by the increase of Bax/Bcl-xL expression ratio, without affecting the activities of Akt and mTOR. Taken together, these data suggest that enhancement of genistein activity by equol would be mainly mediated by augmented induction of apoptosis rather than arrest or delay of the cell cycle.

Isolation and Characterization of a Human Intestinal Bacterium Eggerthella sp. AUH-JLD49s for the Conversion of (-)-3'-Desmethylarctigenin

Arctiin is the most abundant bioactive compound contained in the Arctium lappa plant. In our previous study, we isolated one single bacterium capable of bioconverting arctigenin, an aglycone of arctiin, to 3'-desmethylarctigenin (3'-DMAG) solely. However, to date, a specific bacterium capable of producing other arctiin metabolites has not been reported. In this study, we isolated one single bacterium, which we named Eggerthella sp. AUH-JLD49s, capable of bioconverting 3'-DMAG under anaerobic conditions. The metabolite of 3'-DMAG by strain AUH-JLD49s was identified as 3'-desmethyl-4'-dehydroxyarctigenin (DMDH-AG) based on electrospray ionization mass spectrometry (ESI-MS) and ¹H and ¹³C nuclear magnetic resonance spectroscopy. The bioconversion kinetics and bioconversion capacity of strain AUH-JLD49s were investigated. In addition, the metabolite DMDH-AG showed an inhibitory effect on cell growth of human colon cancer cell line HCT116 and human breast cancer cell line MDA-MB-231.

Dietary phytoestrogens, intestinal microflora and human health

With the growth of age, the amount of estrogens produced by the human body will get less and less. Studies have shown that estrogen deficiency may cause many kinds of diseases, such as cardiovascular diseases, osteoporosis, and syndrome of menopause. Estrogens are also distributed extensively in numerous types of plants. Since there is a trace amount of natural estrogen in plants, our body can achieve continuous phytoestrogen supplementation while our health will not be influenced or damaged by the absorbed phytoestrogens in diets. After being absorbed, the phytoestrogens in diets may be converted by intestinal microflora to different metabolites with higher estrogenic activity. This review summarizes the types and distributions of phytoestrogens in diets, their metabolism, metabolites and bioactivities, with an aim to provide some guidelines for further study and utilization of microbial biotransforming metabolites of phytoestrogens.

Equol Attenuates Atherosclerosis in Apolipoprotein E-Deficient Mice by Inhibiting Endoplasmic Reticulum Stress via Activation of Nrf2 in Endothelial Cells

The development of atherosclerosis is closely related to excessive endoplasmic reticulum stress (ERs). Equol reportedly protects against cardiovascular disease; however, the underlying mechanism for this protection remains unknown. Herein, the mechanisms contributing to the atheroprotective effect of equol were addressed using apolipoprotein E knockout (apoE-/-) mice fed a high-fat diet (HFD) with or without equol. Equol intervention reduced atherosclerotic lesions in the aorta in HFD-fed apoE-/- mice. Plasma lipid analysis showed that equol intervention reduced triglycerides, total cholesterol and LDL-cholesterol and increased HDL-cholesterol. Additionally, equol administration decreased lipid accumulation in the liver. Simultaneously, equol treatment inhibited cell apoptosis induced by t-BHP and thapsigargin in human umbilical vein endothelial cells (HUVECs). Furthermore, equol treatment attenuated palmitate, t-BHP or thapsigargin-induced upregulation of ER stress markers, including p-PERK, p-eIF2α, GRP78, ATF6 and CHOP proteins expression. The same tendency was also observed in aortic lysates in apoE-/- mice fed with equol plus HFD compared with HFD alone. Moreover, equol treatment dose dependently activated the Nrf2 signaling pathway under oxidative stress. Additionally, elevation of Nrf2 induction was found in aortic lysates in apoE-/- mice fed with a HFD diet containing equol compared with a HFD diet without equol. Importantly, Nrf2 siRNA interference induced CHOP and attenuated the effect of equol to inhibit t-BHP mediated CHOP induction, furthermore, abrogated cell apoptosis induced by t-BHP, suggesting a role for Nrf2 in the protective effect of equol in HUVECs. Collectively, these findings implicate that the improvement of atherosclerosis by equol through attenuation of ER stress is mediated, at least in part, by activating the Nrf2 signaling pathway.

Equol inhibits growth, induces atresia, and inhibits steroidogenesis of mouse antral follicles in vitro

Equol is a non-steroidal estrogen metabolite produced by microbial conversion of daidzein, a major soy isoflavone, in the gut of some humans and many animal species. Isoflavones and their metabolites can affect endogenous estradiol production, action, and metabolism, potentially influencing ovarian follicle function. However, no studies have examined the effects of equol on intact ovarian antral follicles, which are responsible for sex steroid synthesis and further development into ovulatory follicles. Thus, the present study tested the hypothesis that equol inhibits antral follicle growth, increases follicle atresia, and inhibits steroidogenesis in the adult mouse ovary. To test this hypothesis, antral follicles isolated from adult CD-1 mice were cultured with vehicle control (dimethyl sulfoxide; DMSO) or equol (600 nM, 6 μM, 36 μM, and 100 μM) for 48 and 96 h. Every 24h, follicle diameters were measured to monitor growth. At 48 and 96 h, the culture medium was subjected to measurement of hormone levels, and the cultured follicles were subjected to gene expression analysis. Additionally, follicles were histologically evaluated for signs of atresia after 96 h of culture. The results indicate that equol (100 μM) inhibited follicle growth, altered the mRNA levels of bcl2-associated X protein and B cell leukemia/lymphoma 2, and induced follicle atresia. Further, equol decreased the levels of estradiol, testosterone, androstenedione, and progesterone, and it decreased mRNA levels of cholesterol side-chain cleavage, steroid 17-α-hydroxalase, and aromatase. Collectively, these data indicate that equol inhibits growth, increases atresia, and inhibits steroidogenesis of cultured mouse antral follicles.

The interplay between GRP78 expression and Akt activation in human colon cancer cells under celecoxib treatment

It has been reported previously that celecoxib shows antitumor effects in many types of cancers. Here, we detected its effects on DLD-1 and SW480 (two human colon cancer cell lines) and investigated the dynamic relationship between the 78-kDa glucose-regulatory protein (GRP78) and the phosphoinositide 3-kinase (PI3K)/Akt pathway. Gene expression was detected by real-time PCR and western blot analysis; the cytotoxicity was determined by the MTT assay and flow cytometry. First, the results showed that celecoxib induced cytotoxicity in a dose-dependent and time-dependent manner. Furthermore, we found the celecoxib-triggered unfolded protein response and the bidirectional regulation of Akt activation in both cell lines. Inhibiting the Akt activation by the PI3K inhibitor LY294002 markedly enhanced GRP78 expression. Besides, silencing the GRP78 expression regulated Akt activation in a time-dependent manner and increased the induction of the C/EBP homologous protein (CHOP) as well as considerably promoted celecoxib-induced apoptosis. In conclusion, these findings provide evidence that under the celecoxib treatment, GRP78 plays a protective role by modulating Akt activation and abrogating CHOP expression. However, Akt activation can provide a feedback loop to inhibit GRP78 expression. These studies can lead to novel therapeutic strategies for human colon cancer.

Cancer therapy using natural ligands that target estrogen receptor beta

Estrogen receptor beta (ERβ) is one of the two key receptors (ERα, ERβ) that facilitate biological actions of 17β-estradiol (E2). ERβ is widely expressed in many tissues, and its expression is reduced or lost during progression of many tumors. ERβ facilitates estrogen signaling by both genomic (classical and non-classical) and extra-nuclear signaling. Emerging evidence suggests that ERβ functions as a tissue-specific tumor suppressor with anti-proliferative actions. Recent studies have identified a number of naturally available selective ERβ agonists. Targeting ERβ using its naturally available ligands is an attractive approach for treating and preventing cancers. This review presents the beneficial actions of ERβ signaling and clinical utility of several natural ERβ ligands as potential cancer therapy.

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 qPCR and immunofluorescent assay. Changes in cell cycle distribution and apoptosis rate were detected by flow cytometry. The mRNA expression of cyclin E1 and P21^WAF1 was determined by qPCR. 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 time-dependent manner after treatment for 24, 36, or 48 h (P < 0.05 for all). Equol also decreased the mRNA (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 P21^WAF1 (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.