Molecular effects of soy phytoalexin glyceollins in human prostate cancer cells LNCaP

Glyceollins from soybean: Their pharmacological effects and biosynthetic pathways

Flavonoids are a highly abundant class of secondary metabolites present in plants. Isoflavonoids, in particular, are primarily synthesized in leguminous plants within the subfamily Papilionoideae. Numerous reports have established the favorable role of isoflavonoids in preventing a range of human diseases. Among the isoflavonoid components, glyceollins are synthesized specifically in soybean plants and have displayed promising effects in mitigating the occurrence and progression of breast and ovarian cancers as well as other diseases. Consequently, glyceollins have become a sought-after natural component for promoting women's health. In recent years, extensive research has focused on investigating the molecular mechanism underlying the preventative properties of glyceollins against various diseases. Substantial progress has also been made toward elucidating the biosynthetic pathway of glyceollins and exploring potential regulatory factors. Herein, we provide a review of the research conducted on glyceollins since their discovery five decades ago (1972-2023). We summarize their pharmacological effects, biosynthetic pathways, and advancements in chemical synthesis to enhance our understanding of the molecular mechanisms of their function and the genes involved in their biosynthetic pathway. Such knowledge may facilitate improved glyceollin synthesis and the creation of health products based on glyceollins.

Novel Therapeutic Combination Targets the Growth of Letrozole-Resistant Breast Cancer through Decreased Cyclin B1

As breast cancer cells transition from letrozole-sensitive to letrozole-resistant, they over-express epidermal growth factor receptor (EGFR), mitogen-activated protein kinase (MAPK), and human epidermal growth factor receptor 2 (HER2) while acquiring enhanced motility and epithelial-to-mesenchymal transition (EMT)-like characteristics that are attenuated and reversed by glyceollin treatment, respectively. Interestingly, glyceollin inhibits the proliferation and tumor progression of triple-negative breast cancer (TNBC) and estrogen-independent breast cancer cells; however, it is unlikely that a single phytochemical would effectively target aromatase-inhibitor (AI)-resistant metastatic breast cancer in the clinical setting. Since our previous report indicated that the combination of lapatinib and glyceollin induced apoptosis in hormone-dependent AI-resistant breast cancer cells, we hypothesized that combination therapy would also be beneficial for hormone independent letrozole-resistant breast cancer cells (LTLT-Ca) compared to AI-sensitive breast cancer cells (AC-1) by decreasing the expression of proteins associated with proliferation and cell cycle progression. While glyceollin + lapatinib treatment caused comparable inhibitory effects on the proliferation and migration in both cell lines, combination treatment selectively induced S and G2/M phase cell cycle arrest of the LTLT-Ca cells, which was mediated by decreased cyclin B1. This phenomenon may represent a unique opportunity to design novel combinatorial therapeutic approaches to target hormone-refractory breast tumors.

Glyceollins Trigger Anti-Proliferative Effects in Hormone-Dependent Aromatase-Inhibitor-Resistant Breast Cancer Cells through the Induction of Apoptosis

Aromatase inhibitors (AIs) are standard treatment for estrogen-dependent postmenopausal breast tumors; however, resistance develops leading to tumor relapse and metastasis. We previously demonstrated that glyceollin inhibits proliferation, survival, and migration of hormone-independent letrozole-resistant breast cancer. Since many AI-resistant tumors remain hormone-dependent, identifying distinctions between estrogen-receptor-positive (ER+) and ER-negative (ER-) AI-resistant tumor response to therapy is critical. We hypothesize that treating ER+ letrozole-resistant T47D breast cancer cells (T47DaromLR) with a combination of 10 μM glyceollin and 0.5 μM lapatinib (a dual EGFR/HER2 inhibitor) will decrease cell proliferation through induction of apoptosis. The T47DaromLR cells were found to overexpress HER2 and MAPK while maintaining aromatase and ER levels compared to their letrozole-sensitive (T47Darom) counterparts. In the absence of estrogen stimulation, glyceollin ± lapatinib had no effect on the proliferation of the T47Darom cells, while glyceollin treatment caused 46% reduction in the proliferation of T47DaromLR cells, which was further diminished when combined with lapatinib. While neither agent influenced cell migration, glyceollin and lapatinib reduced S and G2/M phase cell entry and exclusively induced apoptosis by 1.29-fold in the T47DaromLR cells. Taken together, these results suggest that glyceollins and lapatinib may have potential as a novel combination therapeutic approach for hormone-dependent, letrozole-resistant tumors.

Modification of miRNA Expression through plant extracts and compounds against breast cancer: Mechanism and translational significance

BACKGROUND

Cancer is hyper-proliferative, multi-factorial and multi-step, heterogeneous group of molecular disorders. It is the second most reported disease after heart diseases. Breast carcinoma is the foremost death causing disease in female population worldwide. Cancer can be controlled by regulating the gene expression. Current therapeutic options are associated with severe side effects and are expensive for the people living in under-developed countries. Plant derived substances have potential application against different diseases like cancer, inflammation and viral infections.

HYPOTHESIS

The mechanism of action of the medicinal plants is largely unknown. Targeting gene network and miRNA using medicinal plants could help in improving the therapeutic options against cancer.

METHODS

The literature from 135 articles was reviewed by using PubMed, google scholar, Science direct to find out the plants and plant-based compounds against breast cancer and also the studies reporting their mechanistic route of action both at coding and noncoding RNA levels.

RESULTS

Natural products act as selective inhibitors of the cancerous cells by targeting oncogenes and tumor suppressor genes or altering miRNA expression. Natural compounds like EGCG from tea, Genistein from fava beans, curcumin from turmeric, DIM found in cruciferous, Resveratrol a polyphenol and Quercetin a flavonoid is found in various plants have been studied for their anticancer activity. The EGCG was found to inhibit proliferative activity by modulating miR-16 and miR-21. Similarly, DIM was found to down regulate miR-92a which results to modulate NFkB and stops cancer development. Another plant-based compound Glyceollins found to upregulate miR-181c and miR-181d having role in tumor suppression. It also found to regulate miR-22, 29b and c, miR-30d, 34a and 195. Quercetin having anti-cancer activity induce the apoptosis through regulating miR-16, 26b, 34a, let-7g, 125a and miR-605 and reduce the miRNA expression like miR-146a/b, 503 and 194 which are involved in metastasis.

CONCLUSION

Targeting miRNA expression using natural plant extracts can have a reverse effect on cell proliferation; turning on and off tumor-inducing and suppressing genes. It can be efficiently adopted as an adjuvant with the conventional form of therapies to increase their efficacy against cancer progression.

Acidity stress for the systemic elicitation of glyceollin phytoalexins in soybean plants

Glyceollins are the major pathogen- and stress-inducible natural products (phytoalexins) of soybean that possess broad-spectrum anticancer and neuroprotective properties. Yet like other phytoalexins, glyceollins are difficult to obtain because they are typically biosynthesized only transiently and in low amounts in plant tissues. We recently identified acidity stress (pH 3.0 growth medium) as an elicitor that exerted prolonged (week-long) inductive effects on glyceollin biosynthesis and identified the NAC family TF gene GmNAC42-1 that activates glyceollin biosynthesis in response to acidity stress or WGE from the soybean pathogen Phytophthora sojae. GmNAC42-1 was annotated as an SAR gene and SAR genes were statistically overrepresented in the transcriptomic response to acidity stress suggesting that acidity stress triggers the systemic elicitation of glyceollin biosynthesis. Here, we demonstrate that acidity stress acts as a systemic elicitor when provided to soybean roots. Acidity stress preferentially elicited specific glyceollins in different soybean organs with exceptionally high yields of glyceollin I in root tissues.

An Update on the Effects of Glyceollins on Human Health: Possible Anticancer Effects and Underlying Mechanisms

Biologically active plant-based compounds, commonly referred to as phytochemicals, can influence the expression and function of various receptors and transcription factors or signaling pathways that play vital roles in cellular functions and are then involved in human health and diseases. Thus, phytochemicals may have a great potential to prevent and treat chronic diseases. Glyceollins, a group of phytoalexins that are isolated from soybeans, have attracted attention because they exert numerous effects on human functions and diseases, notably anticancer effects. In this review, we have presented an update on the effects of glyceollins in relation to their potential beneficial roles in human health. Despite a growing number of studies suggesting that this new family of phytochemicals can be involved in critical cellular pathways, such as estrogen receptor, protein kinase, and lipid kinase signaling pathways, future investigations will be needed to better understand their molecular mechanisms and their specific significance in biomedical applications.

Food-based natural products for cancer management: Is the whole greater than the sum of the parts?

The rise in cancer incidence and mortality in developing countries together with the human and financial cost of current cancer therapy mandates a closer look at alternative ways to overcome this burgeoning global healthcare problem. Epidemiological evidence for the association between cancer and diet and the long latency of most cancer progression have led to active exploration of whole and isolated natural chemicals from different naturally occurring substances in various preclinical and clinical settings. In general the lack of systemic toxicities of most 'whole' and 'isolated' natural compounds, their potential to reduce toxic doses and potential to delay the development of drug-resistance makes them promising candidates for cancer management. This review article examines the suggested molecular mechanisms affected by these substances focusing to a large extent on prostate cancer and deliberates on the disparate results obtained from cell culture, preclinical and clinical studies in an effort to highlight the use of whole extracts and isolated constituents for intervention. As such these studies underscore the importance of factors such as treatment duration, bioavailability, route of administration, selection criteria, standardized formulation and clinical end points in clinical trial design with both entities. Overall lack of parallel comparison studies between the whole natural products and their isolated compounds limits decisive conclusions regarding the superior utility of one over the other. We suggest the critical need for rigorous comparative research to identify which one of the two or both entities from nature would be best qualified to take on the mantle of cancer management.

Soybean-derived glyceollins induce apoptosis through ROS generation

Glyceollins, which are synthesized from daidzein in soybeans infected with fungi, have been shown to have anti-fungal effects and antioxidant properties. However, the anti-proliferative mechanism of glyceollins against tumor cells is unknown. Glyceollin-induced apoptosis was evidenced by a decrease in cell viability and mitochondrial membrane potential, and an increase in early redistribution of plasma membrane phosphatidylserine, the sub G1 phase, and DNA fragmentation in hepa1c1c7 cells. Western blot analysis showed that treatment of the hepa1c1c7 cells with the glyceollins decreased the expression of pro-caspase-3, Bcl-2, and cell cycle-related proteins, but increased the expression of p21 and p27, and cytochrome C release into cytosol. At a concentration of 6 μg mL(-1) or higher, glyceollins significantly stimulated the production of reactive oxygen species (ROS), which appear to be responsible for the apoptotic activity of the compounds. Our present study demonstrated that the high dose of glyceollins possibly caused apoptosis in mouse hepatoma cells through the production of ROS, suggesting the potential to exploit glyceollins as anti-tumorigenic agents.

Soy isoflavones and prostate cancer: a review of molecular mechanisms

Soy isoflavones are dietary components for which an association has been demonstrated with reduced risk of prostate cancer (PCa) in Asian populations. However, the exact mechanism by which these isoflavones may prevent the development or progression of PCa is not completely understood. There are a growing number of animal and in vitro studies that have attempted to elucidate these mechanisms. The predominant and most biologically active isoflavones in soy products, genistein, daidzein, equol, and glycetin, inhibit prostate carcinogenesis in some animal models. Cell-based studies show that soy isoflavones regulate genes that control cell cycle and apoptosis. In this review, we discuss the literature relevant to the molecular events that may account for the benefit of soy isoflavones in PCa prevention or treatment. These reports show that although soy isoflavone-induced growth arrest and apoptosis of PCa cells are plausible mechanisms, other chemo protective mechanisms are also worthy of consideration. These possible mechanisms include antioxidant defense, DNA repair, inhibition of angiogenesis and metastasis, potentiation of radio- and chemotherapeutic agents, and antagonism of estrogen- and androgen-mediated signaling pathways. Moreover, other cells in the cancer milieu, such as the fibroblastic stromal cells, endothelial cells, and immune cells, may be targeted by soy isoflavones, which may contribute to soy-mediated prostate cancer prevention. In this review, these mechanisms are discussed along with considerations about the doses and the preclinical models that have been used.

Hormesis of glyceollin I, an induced phytoalexin from soybean, on budding yeast chronological lifespan extension

Glyceollin I, an induced phytoalexin isolated from soybean, has been reported to have various bioactivities, including anti-bacterial, anti-nematode, anti-fungal, anti-estrogenic and anti-cancer, anti-oxidant, anti-inflammatory, insulin sensitivity enhancing, and attenuation of vascular contractions. Here we show that glyceollin I has hormesis and extends yeast life span at low (nM) doses in a calorie restriction (CR)-dependent manner, while it reduces life span and inhibits yeast cell proliferation at higher (μM) doses. In contrast, the other two isomers (glyceollin II and III) cannot extend yeast life span and only show life span reduction and antiproliferation at higher doses. Our results in anti-aging activity indicate that glyceollin I might be a promising calorie restriction mimetic candidate, and the high content of glyceollins could improve the bioactivity of soybean as functional food ingredients.

Inhibitory effect of glyceollins on vasculogenesis through suppression of endothelial progenitor cell function

SCOPE

Endothelial progenitor cells (EPCs) are derived from hematopoietic stem cells, and have the ability to differentiate into mature endothelial cells and contribute to neovascularization. Glyceollins are a type of phytoalexin produced in soybeans under stress conditions. The aim of this study is to determine the effect of glyceollin treatment on EPCs during early tumor vasculogenesis.

METHODS AND RESULTS

We found that glyceollin treatment significantly decreased the number of EPC colony-forming units in human cord blood-derived AC133⁺ cells and mouse bone-marrow-derived c-Kit⁺/Sca-1⁺/Lin⁻ cells. Glyceollin treatment diminished the number of lineage-committed EPC cells in a dose-dependent manner (1-20 μM). Glyceollin treatment inhibited EPC migration, tube formation and the mRNA expression of angiopoietin-1 (Ang-1), Tie-2, stromal-derived factor-1 (SDF-1), C-X-C-chemokine receptor-4 (CXCR4), and endothelial nitric oxide synthase (eNOS) in cultured EPCs. Glyceollin treatment suppressed activation of Akt, Erk, and eNOS induced by SDF-1α or vascular endothelial growth factor (VEGF). Treatment with 10 mg/kg glyceollins significantly reduced the number of tumor-induced circulating EPCs and the incorporation of EPCs into neovessels in bone marrow transplanted mice.

CONCLUSION

These results suggest that glyceollins inhibit the function of EPCs in tumor neovascularization. Glyceollins from soybean elicitation could be beneficial in prevention of cancer development via vasculogenesis.

MEK5/ERK5 signaling suppresses estrogen receptor expression and promotes hormone-independent tumorigenesis

Endocrine resistance and metastatic progression are primary causes of treatment failure in breast cancer. While mitogen activated protein kinases (MAPKs) are known to promote ligand-independent cell growth, the role of the MEK5-ERK5 pathway in the progression of clinical breast carcinoma remains poorly understood. Here, we demonstrated increased ERK5 activation in 30 of 39 (76.9%) clinical tumor samples, as well as across breast cancer cell systems. Overexpression of MEK5 in MCF-7 cells promoted both hormone-dependent and hormone-independent tumorigenesis in vitro and in vivo and conferred endocrine therapy resistance to previously sensitive breast cancer cells. Expression of MEK5 suppressed estrogen receptor (ER)α, but not ER-β protein levels, and abrogated downstream estrogen response element (ERE) transcriptional activity and ER-mediated gene transcription. Global gene expression changes associated with upregulation of MEK5 included increased activation of ER-α independent growth signaling pathways and promotion of epithelial-to-mesenchymal transition (EMT) markers. Taken together, our findings show that the MEK5-ERK5 pathway mediates progression to an ER(-), mesenchymal and endocrine therapy resistant phenotype. Given the need for new clinical therapeutic targets, our results demonstrate the therapeutic potential of targeting the MEK5-ERK5 pathway in breast cancer.

Phytoalexins, miRNAs and breast cancer: a review of phytochemical-mediated miRNA regulation in breast cancer

There is growing interest in the diverse signaling pathways that regulate and affect breast tumorigenesis, including the role of phytochemicals and the emerging role of microRNAs (miRNAs). Recent studies demonstrate that miRNAs regulate fundamental cellular and developmental processes at the transcriptional and translational level under normal and disease conditions. While there is growing evidence to support the role of phytoalexin-mediated miRNA regulation of cancer, few reports address this role in breast cancer. Recent reports by our group and others demonstrate that natural products, including stilbenes, curcumin, and glyceollins, could alter the expression of specific miRNAs, which may lead to increased sensitivity of cancer cells to conventional anti-cancer agents and, therefore, hormone-dependent and hormone-independent tumor growth inhibition. This review will discuss how dietary intake of natural products, by regulating specific miRNAs, contribute to the prevention and treatment of breast cancer.

Cholesterol-lowering activity of soy-derived glyceollins in the golden Syrian hamster model

Hypercholesterolemia is one of the major factors contributing to the risk of cardiovascular disease (CVD), which is the leading cause of death in developed countries. Consumption of soy foods has been recognized to lower the risk of CVD, and phytochemicals in soy are believed to contribute to the health benefits. Glyceollin is one of the candidate phytochemicals synthesized in stressed soy that may account for many unique biological activities. In this study, the in vivo cholesterol-lowering effect of glyceollins was investigated. Male golden Syrian hamsters were fed diets including (1) 36 kcal% fat diet, (2) 36 kcal% fat diet containing 250 mg/kg diet glyceollins, or (3) chow for 28 days. Hepatic cholesterol esters and free cholesterol, hepatic total lipid content, plasma lipoproteins, fecal bile acid, fecal total cholesterol, and cholesterol metabolism related gene expressions were measured. Glyceollin supplementation led to significant reduction of plasma VLDL, hepatic cholesterol esters, and total lipid content. Consistent with changes in circulating cholesterol, glyceollin supplementation also altered expression of the genes related to cholesterol metabolism in the liver. In contrast, no change in plasma LDL and HDL, fecal bile acid, or cholesterol content was observed. The cholesterol-lowering effect of glyceollins appeared not to go through the increase of bile excretion. These results supported glyceollins' role as novel soy-derived cholesterol-lowering phytochemicals that may contribute to soy's health effects.

Glyceollins, a novel class of soybean phytoalexins, inhibit SCF-induced melanogenesis through attenuation of SCF/c-kit downstream signaling pathways

The anti-melanogenesis effect of glyceollins was examined by melanin synthesis, tyrosinase activity assay in zebrafish embryos and in B16F10 melanoma cells. When developing zebrafish embryos were treated with glyceollins, pigmentation of the embryos, melanin synthesis and tyrosinase activity were all decreased compared with control zebrafish embryos. In situ expression of a pigment cell-specific gene, Sox10, was dramatically decreased by glyceollin treatment in the neural tubes of the trunk region of the embryos. Stem cell factor (SCF)/c-kit signaling pathways as well as expression of microphthalmia-associated transcription factor (MITF) were determined by western blot analysis. Glyceollins inhibited melanin synthesis, as well as the expression and activity of tyrosinase induced by SCF, in a dose-dependent manner in B16F10 melanoma cells. Pretreatment of B16F10 cells with glyceollins dose-dependently inhibited SCF-induced c-kit and Akt phosphorylation. Glyceollins significantly impaired the expression and activity of MITF. An additional inhibitory function of glyceollins was to effectively downregulate intracellular cyclic AMP levels stimulated by SCF in B16F10 cells. Glyceollins have a depigmentation/whitening activity in vitro and in vivo, and that this effect may be due to the inhibition of SCF-induced c-kit and tyrosinase activity through the blockade of downstream signaling pathway.

Inhibition of p38 mitogen-activated protein kinase alters microRNA expression and reverses epithelial-to-mesenchymal transition

Acquired chemoresistance and epithelial-to-mesenchymal transition (EMT) are hallmarks of cancer progression and of increasing clinical relevance. We investigated the role of miRNA and p38 mitogen-activated protein kinase (MAPK) signaling in the progression of breast cancer to a drug-resistant and mesenchymal phenotype. We demonstrate that acquired death receptor resistance results in increased hormone-independent tumorigenesis compared to hormone-sensitive parental cells. Utilizing global miRNA gene expression profiling, we identified miRNA alterations associated with the development of death receptor resistance and EMT progression. We further investigated the role of p38 MAPK in this process, showing dose-dependent inactivation of p38 by its inhibitor RWJ67657 and decreased downstream ATF and NF-κB signaling. Pharmacological inhibition of p38 also decreased chemoresistant cancer tumor growth in xenograft animal models. Interestingly, inhibition of p38 partially reversed the EMT changes found in this cell system, as illustrated by decreased gene expression of the EMT markers Twist, Snail, Slug and ZEB and protein and mRNA levels of Twist, a known EMT promoter, concomitant with decreased N-cadherin protein. RWJ67657 treatment also altered the expression of several miRNAs known to promote therapeutic resistance, including miR-200, miR-303, miR-302, miR-199 and miR-328. Taken together, our results demonstrate the roles of multiple microRNAs and p38 signaling in the progression of cancer and demonstrate the therapeutic potential of targeting the p38 MAPK pathway for reversing EMT in an advanced tumor phenotype.

Screening and identification of glyceollins and their metabolites by electrospray ionization tandem mass spectrometry with precursor ion scanning

A method has been developed for screening glyceollins and their metabolites based on precursor ion scanning. Under higher-energy collision conditions with the employment of a triple quadrupole mass spectrometer in the negative ion mode, deprotonated glyceollin precursors yield a diagnostic radical product ion at m/z 148. We propose this resonance-stabilized radical anion, formed in violation of the even-electron rule, to be diagnostic of glyceollins and glyceollin metabolites. Liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) established that scanning for precursors of m/z 148 can identify glyceollins and their metabolites from plasma samples originating from rats dosed with glyceollins. Precursor peaks of interest were found at m/z 337, 353, 355, 417, and 433. The peak at m/z 337 corresponds to deprotonated glyceollins, whereas the others represent metabolites of glyceollins. Accurate mass measurement confirmed m/z 417 to be a sulfated metabolite of glyceollins. The peak at m/z 433 is also sulfated, but it contains an additional oxygen, as confirmed by accurate mass measurement. The latter metabolite differs from the former likely by the replacement of a hydrogen with a hydroxyl moiety. The peaks at m/z 353 and 355 are proposed to correspond to hydroxylated metabolites of glyceollins, wherein the latter additionally undergoes a double bond reduction.

Glyceollin improves endoplasmic reticulum stress-induced insulin resistance through CaMKK-AMPK pathway in L6 myotubes

Glyceollin has been shown to have antidiabetic properties, although its molecular mechanism is not known. Here, we have investigated the metabolic effects of glyceollin in animal models of insulin resistance and in endoplasmic reticulum (ER) stress-responsive muscle cells. db/db mice were treated with glyceollin for 4weeks and triglycerides, total cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) levels were measured. Glyceollin reduced serum insulin and triglycerides and increased HDL levels in db/db mice. Furthermore, glyceollin caused a significant improvement in glucose homeostasis without altering body weight and food intake in db/db mice. In muscle cells, glyceollin increased the activity of AMP-activated protein kinase (AMPK) as well as cellular glucose uptake. Fatty acid oxidation was also increased. In parallel, phosphorylation of acetyl-CoA carboxylase (ACC) at Ser-79 was increased, consistent with decreased ACC activity. An insulin-resistant state was induced by exposing cells to 5μg/ml of tunicamycin as indicated by decreased insulin-mediated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and glucose uptake. Inhibition of insulin-mediated tyrosine phosphorylation of IRS-1 and glucose uptake under ER stress was prevented by glyceollin. Strikingly, glyceollin reduced ER stress-induced, c-Jun NH2-terminal kinase activation and subsequently increased insulin signaling via stimulation of AMPK activity in L6 myotubes. Pharmacologic inhibition or knockdown of Ca(2+)/calmodulin-dependent protein kinase kinase blocked glyceollin-increased AMPK phosphorylation and insulin sensitivity under ER stress conditions. Taken together, these results indicate that glyceollin-mediated enhancement of insulin sensitivity under ER stress conditions is predominantly accomplished by activating AMPK, thereby having beneficial effects on hyperglycemia and insulin resistance.

Antiestrogenic activity of flavonoid phytochemicals mediated via the c-Jun N-terminal protein kinase pathway. Cell-type specific regulation of estrogen receptor alpha

Flavonoid phytochemicals act as both agonists and antagonists of the human estrogen receptors (ERs). While a number of these compounds act by directly binding to the ER, certain phytochemicals, such as the flavonoid compounds chalcone and flavone, elicit antagonistic effects on estrogen signaling independent of direct receptor binding. Here we demonstrate both chalcone and flavone function as cell type-specific selective ER modulators. In MCF-7 breast carcinoma cells chalcone and flavone suppress ERα activity through stimulation of the stress-activated members of the mitogen-activated protein kinase (MAPK) family: c-Jun N-terminal kinase (JNK)1 and JNK2. The use of dominant-negative mutants of JNK1 or JNK2 in stable transfected cells established that the antiestrogenic effects of chalcone and flavone required intact JNK signaling. We further show that constitutive activation of the JNK pathway partially suppresses estrogen (E2)-mediated gene expression in breast, but not endometrial carcinoma cells. Our results demonstrate a role for stress-activated MAPKs in the cell type-specific regulation of ERα function.

Glyceollin-containing fermented soybeans improve glucose homeostasis in diabetic mice

OBJECTIVE

Our previous in vitro study demonstrated that glyceollins help normalize glucose homeostasis by potentiating β-cell function and survival in insulinoma cells as well as improving glucose utilization in adipocytes. Here, we investigated whether fermented soybeans containing glyceollins had an antidiabetic action in type 2 diabetic animals.

METHODS

The diabetic mice, their diabetes induced by intraperitoneal injections of streptozotocin (20 mg/kg bw), were administered a high fat diet with no soybeans (control), 10% unfermented soybeans and 10% fermented soybeans containing glyceollins, respectively, (FSG) for 8 weeks. As positive controls, rosiglitazone (20 mg/kg/bw) was given to diabetic mice fed a no soybean diet and non-diabetic mice were also placed on the same diet.

RESULTS

Among the diabetic mice, FSG-treated mice exhibited the lowest peak for blood glucose levels with an elevation of serum insulin levels during the first part of oral glucose tolerance testing. FSG also made blood glucose levels drop quickly after the peak and it decreased blood glucose levels more than the control during insulin tolerance testing. This improvement was associated with increased hepatic glycogen accumulation and decreased triglyceride storage. The phosphorylation of Akt, AMP-kinase, and acetyl-CoA carboxylase in the liver was potentiated by FSG, whereas phosphoenolpyruvate carboxykinase expression decreased. The enhancement of glucose homeostasis was comparable to the effect induced by rosiglitazone, a commercial peroxisome proliferator-activated receptor-γ agonist, but it did not match the level of glucose homeostasis in the non-diabetic mice.

CONCLUSION

Glyceollin-containing FSG improves glucose homeostasis, partly by enhancing hepatic insulin sensitivity in type 2 diabetic mice.

Anti-inflammatory effects of glyceollins derived from soybean by elicitation with Aspergillus sojae

OBJECTIVE

Given the preventive effect of soy intake against several chronic diseases, this study was conducted to investigate the inhibitory activity against inflammatory response of phytoalexins glyceollins derived from soybean isoflavones by treatment with a biotic elicitor.

METHODS

Using RAW264.7 cells, we examined the effects of glyceollins on production of nitric oxide (NO) and inflammatory cytokines, expression of inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2, and activation of NF-кB, induced by lipopolysaccharide (LPS).

RESULTS

Our data showed that glyceollins effectively inhibited NO production, IL-6 release, and expression of iNOS and COX-2 induced by LPS. In particular, glyceollins suppressed the LPS-induced phosphorylation of NF-кB p65, suggesting that the compounds inhibit the production of NO and transcriptional activation of COX-2 by regulating NF-кB activity. In another experiment we found that glyceollins enhanced the expression of heme oxygenase 1 in LPS-treated RAW264.7 cells. Glyceollins also reduced TPA-induced skin inflammation in a mouse model, confirming the anti-inflammatory activity of glyceollins in an in-vivo system as well as in a cell culture system.

CONCLUSION

Glyceollins exert an anti-inflammatory effect, which is mediated through the inhibition of NF-κB activation in LPS-activated murine RAW264.7 cells. Glyceollins merit further study as potential therapeutic agents for inflammatory disorders.

Effects of SDF-1-CXCR4 signaling on microRNA expression and tumorigenesis in estrogen receptor-alpha (ER-α)-positive breast cancer cells

The majority of breast cancer cases ultimately become unresponsive to endocrine therapies, and this progression of breast cancer from hormone-responsive to hormone-independent represents an area in need of further research. Additionally, hormone-independent carcinomas are characterized as being more aggressive and metastatic, key features of more advanced disease. Having previously shown the ability of the stromal-cell derived factor-1 (SDF-1)-CXCR4 signaling axis to promote primary tumorigenesis and hormone independence by overexpressing CXCR4 in MCF-7 cells, in this study we further examined the role of SDF-1/CXCR4 in the endogenously CXCR4-positive, estrogen receptor α (ER-α)-positive breast carcinoma cell line, MDA-MB-361. In addition to regulating estrogen-induced and hormone-independent tumor growth, CXCR4 signaling stimulated the epithelial-to-mesenchymal transition, evidenced by decreased CDH1 expression following SDF-1 treatment. Furthermore, inhibition of CXCR4 with the small molecule inhibitor AMD3100 induced CDH1 gene expression and inhibited CDH2 gene expression in MDA-MB-361 cells. Further, exogenous SDF-1 treatment induced ER-α-phosphorylation in both MDA-MB-361 and MCF-7-CXCR4 cells, demonstrating ligand-independent activation of ER-α through CXCR4 crosstalk. qPCR microRNA array analyses of the MDA-MB-361 and MCF-7-CXCR4 cell lines revealed changes in microRNA expression profiles induced by SDF-1, consistent with a more advanced disease phenotype and further supporting our hypothesis that the SDF-1/CXCR4 signaling axis drives ER-α-positive breast cancer cells to a hormone independent and more aggressive phenotype. In this first demonstration of SDF-1-CXCR4-induced microRNAs in breast cancer, we suggest that this signaling axis may promote tumorigenesis via microRNA regulation. These findings represent future potential therapeutic targets for the treatment of hormone-independent and endocrine-resistant breast cancer.

Glyceollins inhibit platelet-derived growth factor-mediated human arterial smooth muscle cell proliferation and migration

Platelet-derived growth factor (PDGF)-BB can induce abnormal proliferation and migration of vascular smooth muscle cells (VSMC) that are involved in the development of CVD. In our preliminary study, phytoalexin glyceollins (glyceollins I, II and III) isolated from soyabean seeds cultured withAspergillus sojaeshowed strong antioxidant and anti-inflammatory activity. Since antioxidants showed beneficial effects on chronic inflammatory diseases, the purpose of the present study was to examine the effects of glyceollins on PDGF-induced proliferation and migration in human aortic smooth muscle cells (HASMC). Incubation of resting HASMC with glyceollins for 24 h significantly diminished PDGF-increased cell number and DNA synthesis in a dose-dependent manner without any cytotoxicity. In addition to blocking of the PDGF-inducible progression through the G0/G1to the S phase of the cell cycle, glyceollins down-regulated the expression of cyclin-dependent kinase (CDK)2 and cyclin D1, and up-regulated the expression of CDK inhibitors such as p27kip1and p53.Glyceollins also effectively inhibited reactive oxygen species generation and phosphorylation of PDGF receptor-β, phospholipase Cγ1, Akt and extracellular signal-regulated kinase 1/2 by PDGF stimulation. Furthermore, glyceollins were found to inhibit PDGF-induced dissociation of actin filaments and cell migration. Thus, the results suggest that glyceollins could become a potent therapeutic agent for regulating VSMC-associated vascular disease such as atherosclerosis and restenosis after angioplasty.

Nrf2-mediated induction of phase 2 detoxifying enzymes by glyceollins derived from soybean exposed to Aspergillus sojae

Numerous antioxidants have been reported to cause transcriptional activation of several antioxidant enzymes through binding antioxidant-response element on their promoter region. We, therefore, attempted to examine whether glyceollins, which share common structural features with many phase 2 enzyme inducers and antioxidant activity, could induce detoxifying/antioxidant enzymes. Glyceollins induced NAD(P)H:quinone oxidoreductase activity in a dose-dependent manner in both mouse hepatoma Hepa1c1c7 and its mutant BPRc1 cells. The compounds also increased the expression of some representative antioxidant enzymes, such as heme oxygenase 1,gamma-glutamylcysteine synthase, and glutathione reductase, by promoting nuclear translocation of the NF-E2-related factor-2 (Nrf2). Furthermore, phosphorylation of Akt and antioxidant response element-mediated reporter gene expression were enhanced by glyceollins but suppressed by LY294002, an inhibitor of phosphoinositide 3-kinases (PI3K). This suggests that glyceollins may cause Nrf2-mediated phase 2 enzyme induction through activation of the PI3K signaling pathway as well as interaction with Keap1. Our molecular docking simulations also suggest that the glyceollin isomers tightly bind into the binding pocket around Cys151, preventing Nrf2 from docking to Keap1. In conclusion, the current data suggest that glyceollins induced phase 2 detoxifying enzymes likely through promoting nuclear translocation of Nrf2, which is known to be regulated by phosphorylation of Nrf2 and/or disrupting Keap1-Nrf2 complex formation.

Broccoli-derived phytochemicals indole-3-carbinol and 3,3'-diindolylmethane exerts concentration-dependent pleiotropic effects on prostate cancer cells: comparison with other cancer preventive phytochemicals

In the present studies, we utilized prostate cancer cell culture models to elucidate the mechanisms of action of broccoli-derived phytochemicals 3,3'-diindolylmethane (DIM) and indole-3-carbinol (I3C). We found DIM and I3C at 1-5 µM inhibited androgen and estrogen-mediated pathways and induced xenobiotic metabolism pathway. By contrast, DIM and I3C induced cyclin inhibitors, indicators of stress/DNA damage, only at ≥25 µM. We also demonstrated that an inhibitory effect of DIM and I3C on cell growth involves inhibition of insulin-like growth factor-1 receptor expression. More importantly, we showed that differences in efficacies and mechanisms existed between DIM and I3C. These included differences in effective concentrations, a differential effect on androgen receptor binding, and a differential effect on xenobiotic metabolic pathway through aryl hydrocarbon receptor-dependent and -independent mechanism. Furthermore we determined that several other diet-derived cancer protective compounds, similar to DIM and I3C, exhibited pleiotrophic effects on signaling pathways that included proliferation, cell cycle, and nuclear receptors-mediated pathways. However, the efficacies and mechanisms of these compounds vary. We also showed that some cellular pathways are not likely to be affected by DIM or I3C when circulating concentration of orally ingested DIM or I3C is considered. Based on our results, a model for cancer protective effects of DIM and I3C was proposed.

The effects of fungal stress on the antioxidant contents of black soybeans under germination

Black soybeans were germinated with or without Rhizopus oligosporus for 3 days. The samples collected from each day were freeze-dried and extracted with chloroform-methanol-water mixture to simultaneously obtain organic phase (lipophilic extract) and aqueous phase (hydrophilic extract). In the lipophilic extract, α-, γ-, and δ-tocopherol were drastically decreased by 51%, 97%, and 88%, respectively, after 3 day germination under stress. On the other hand, the lipid peroxide concentration was increased in the fungi stressed, germinating beans from day 2 onward, while it was continually decreased in the nonstressed germinating counterpart. The change of antioxidant capacity (ORACoil value) was correlated to the changes of tocopherols and lipid peroxide concentrations. In nonstressed germinatng beans, ORACoil value dropped by 38% after 3 days, while in the fungi-stressed germinating beans, ORACoil was decreased by 80%. In hydrophilic extract, the antioxidant activity, measured by ORAChydro assay, is about 80 times higher than the ORACoil values, but there is no significant change before and after germination (either with or without stress). The total phenolic content in the hydrophilic extract increased only slightly by 9% in germinated beans and 15% in fungus-stress germinated samples, respectively. The advantage of stress germination of soybeans in enriching phytoalexins is traded off by loss of tocopherols.

Cytokine receptor CXCR4 mediates estrogen-independent tumorigenesis, metastasis, and resistance to endocrine therapy in human breast cancer

Estrogen independence and progression to a metastatic phenotype are hallmarks of therapeutic resistance and mortality in breast cancer patients. Metastasis has been associated with chemokine signaling through the SDF-1-CXCR4 axis. Thus, the development of estrogen independence and endocrine therapy resistance in breast cancer patients may be driven by SDF-1-CXCR4 signaling. Here we report that CXCR4 overexpression is indeed correlated with worse prognosis and decreased patient survival irrespective of the status of the estrogen receptor (ER). Constitutive activation of CXCR4 in poorly metastatic MCF-7 cells led to enhanced tumor growth and metastases that could be reversed by CXCR4 inhibition. CXCR4 overexpression in MCF-7 cells promoted estrogen independence in vivo, whereas exogenous SDF-1 treatment negated the inhibitory effects of treatment with the anti-estrogen ICI 182,780 on CXCR4-mediated tumor growth. The effects of CXCR4 overexpression were correlated with SDF-1-mediated activation of downstream signaling via ERK1/2 and p38 MAPK (mitogen activated protein kinase) and with an enhancement of ER-mediated gene expression. Together, these results show that enhanced CXCR4 signaling is sufficient to drive ER-positive breast cancers to a metastatic and endocrine therapy-resistant phenotype via increased MAPK signaling. Our findings highlight CXCR4 signaling as a rational therapeutic target for the treatment of ER-positive, estrogen-independent breast carcinomas needing improved clinical management.

Antioxidant activity of glyceollins derived from soybean elicited with Aspergillus sojae

The extract of soybean exposed to biotic elicitors such as food-grade fungus is known to have antioxidant activity. Glyceollins were major bioactive compounds present in soybean elicited by fungi and shown to have antifungal and anticancer activities. The purpose of present study was to evaluate the antioxidant activities of glyceollins by measuring ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, singlet oxygen quenching, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, hydroxyl radical scavenging activity, and lipid peroxidation inhibition. In addition, the antioxidant potential of glyceollins were measured by a fluorescent probe, 2',7'-dichlorofluorescin diacetate (DCFDA), and dihydroethidium (DHE) in mouse hepatoma hepa1c1c7 cells in which they were insulted with H2O2 to generate reactive oxygen species (ROS). Glyceollins showed a strong reducing power and inhibited lipid peroxidation, with significant scavenging activities of radicals including singlet oxygen, superoxide anion, ABTS, and DPPH. We also found that glyceollins significantly suppressed H2O2-induced ROS production in hepa1c1c7 cells. Therefore, glyceollins deserve further study as natural antioxidants and nutraceuticals.

Inhibitory effect of glyceollin isolated from soybean against melanogenesis in B16 melanoma cells

Natural products with non-toxic and environmentally friendly properties are good resources for skin-whitening cosmetic agents when compared to artificial synthetic chemicals. Here, we investigated the effect of glyceollin produced to induce disease resistance responses of soybean to specific races of an incompatible pathogen, phytophthora sojae, on melanogenesis and discussed their mechanisms in melanin biosynthesis. We found that glyceollin inhibits melanin synthesis and tyrosinase activity in B16 melanoma cells without cytotoxicity. To elucidate the mechanism of the effect of glyceollin on melanogenesis, we conducted western blot analysis for melanogenic enzymes such as tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2. Glyceollin inhibited tyrosinase and TRP-1 protein expression. Additionally, glyceollin effectively inhibited intracellular cAMP levels in B16 melanoma cells stimulated by alpha-melanocyte stimulating hormone (alpha-MSH). These results suggest that the whitening activity of glyceollin may be due to the inhibition of cAMP involved in the signal pathway of alpha-MSH in B16 melanoma cells.

Estrogenic activity of glyceollins isolated from soybean elicited with Aspergillus sojae

Glyceollins, which are synthesized from daidzein in soybeans cultured with fungi, have been shown to have antifungal effects and cancer preventive properties. Several studies have proposed that isoflavones and their metabolites act as a mixed agonist/antagonist for estrogen. Although glyceollins were reported to suppress some cancer cells via anti-estrogenic activity, it is not clear whether the compounds possess estrogenic potential. In contrast to the anti-estrogenic action reported thus far, we observed estrogenic effects of glyceollins using E-screen assay and pS2 expression, whereas glyceollins showed higher affinity for estrogen receptor (ER) beta than ERalpha. We also found that glyceollins were more efficiently produced de novo in minced than in half-sliced soybean, following infection with Aspergillus sojae. In conclusion, glyceollins may be useful in the prevention or amelioration of postmenopausal complications because they had strong estrogenic activity, and their production could be variable depending upon processing prior to fungal inoculation.

Glyceollins, one of the phytoalexins derived from soybeans under fungal stress, enhance insulin sensitivity and exert insulinotropic actions

Glyceollins are a category of phytoalexins that are produced by soybeans under fungal stress, but their effects on glucose homeostasis remain unknown. We hypothesized that glyceollins play an important role in glucose homeostasis by regulating glucose utilization in adipocytes and improving beta-cell function and survival. Glyceollins improved insulin-stimulated glucose uptake in 3T3-L1 adipocytes without activating the peroxisome proliferator-activated receptor-gamma agonist. They decreased triacylglycerol accumulation in adipocytes. In addition, glyceollins slightly improved glucose-stimulated insulin secretion without palmitate treatment in Min6 cells, and they potentiated insulinotropic actions when 500 microM palmitate was used to induce beta-cell dysfunction. This was associated with decreased beta-cell apoptosis because of the attenuation of endoplasmic reticulum stress, as determined by mRNA levels of XBP-1, ATF-4, ATF-6, and CHOP. Glyceollins also potentiated GLP-1 secretion to enhance insulinotropic actions in enteroendocrine cells. In conclusion, glyceollins help normalize glucose homeostasis by potentiating beta-cell function and survival and improving glucose utilization in adipocytes.