Soy Isoflavones and Breast Cancer Cell Lines: Molecular Mechanisms and Future Perspectives

The cytotoxic and genotoxic effects of daidzein on MIA PaCa-2 human pancreatic carcinoma cells and HT-29 human colon cancer cells

Daidzein (DZ) has anti-inflammatory and antioxidant effects, as well as the dose-dependent inhibition effect on cancer cells. In this study, the cytotoxic and genotoxic effects of DZ on HT-29 (human colorectal adenocarcinoma cells) and MIA PaCa-2 (human pancreatic cancer cells) cell lines were determined using the XTT method and Comet assay, respectively. IC₅₀ concentrations of DZ were found to be 200 µM in both MIA PaCa-2 and HT-29 cells treated with DZ for 48 hours (h). When the cells were treated with 200 μM of DZ for 48 h, DNA damage was observed in both cell lines. DNA tail length (TL), tail moment (TM), and tail intensity (TI) increased more in MIA PaCa-2 cells treated with 200 μM of DZ than those in the control cell (untreated MIA PaCa-2 cell) group (p < 0.01). However, only DNA-TI and DNA-TM exhibited higher increases in HT-29 cells treated with 200 μM of DZ than those in the control cell (untreated HT-29 cell) group (p < 0.01). This shows that DZ has cytotoxic and genotoxic effects on both cell lines. The observed genotoxic effects of DZ still need to be confirmed in additional future studies.

The "Yin and Yang" of Natural Compounds in Anticancer Therapy of Triple-Negative Breast Cancers

Among the different types of breast cancers, triple-negative breast cancers (TNBCs) are highly aggressive, do not respond to conventional hormonal/human epidermal growth factor receptor 2 (HER2)-targeted interventions due to the lack of the respective receptor targets, have chances of early recurrence, metastasize, tend to be more invasive in nature, and develop drug resistance. The global burden of TNBCs is increasing regardless of the number of cytotoxic drugs being introduced into the market each year as they have only moderate efficacy and/or unforeseen side effects. Therefore, the demand for more efficient therapeutic interventions, with reduced side effects, for the treatment of TNBCs is rising. While some plant metabolites/derivatives actually induce the risk of cancers, many plant-derived active principles have gained attention as efficient anticancer agents against TNBCs, with fewer adverse side effects. Here we discuss the possible oncogenic molecular pathways in TNBCs and how the purified plant-derived natural compounds specifically target and modulate the genes and/or proteins involved in these aberrant pathways to exhibit their anticancer potential. We have linked the anticancer potential of plant-derived natural compounds (luteolin, chalcones, piperine, deguelin, quercetin, rutin, fisetin, curcumin, resveratrol, and others) to their ability to target multiple dysregulated signaling pathways (such as the Wnt/β-catenin, Notch, NF-κB, PI3K/Akt/mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK) and Hedgehog) leading to suppression of cell growth, proliferation, migration, inflammation, angiogenesis, epithelial-mesenchymal transition (EMT) and metastasis, and activation of apoptosis in TNBCs. Plant-derived compounds in combination with classical chemotherapeutic agents were more efficient in the treatment of TNBCs, possibly with lesser side effects.

Genistein and Ascorbic Acid Reduce Oxidative Stress-Derived DNA Damage Induced by the Antileishmanial Meglumine Antimoniate

Meglumine antimoniate (Glucantime) is a pentavalent antimonial used to treat leishmaniasis, despite its acknowledged toxic effects, such as its ability to cause oxidative damage to lipids and proteins. Recently, our group demonstrated that meglumine antimoniate causes oxidative stress-derived DNA damage. Knowing that antioxidants modulate reactive oxygen species, we evaluated the capacity of genistein and ascorbic acid for preventing genotoxicity caused by meglumine antimoniate. For that, mice (n = 5/group) received genistein (via gavage) in doses of 5, 10, and 20 mg/kg for three consecutive days. After this period, they were treated with 810 mg/kg meglumine antimoniate via intraperitoneal (i.p.) route. Furthermore, mice (n = 5/group) simultaneously received ascorbic acid (i.p.) in doses of 30, 60, and 120 mg/kg and 810 mg/kg meglumine antimoniate. We also conducted post- and pretreatment assays, in which animals received ascorbic acid (60 mg/kg) 24 h prior to or after receiving meglumine antimoniate. Genomic instability and mutagenicity were analyzed through conventional comet assay and enzymatic assay using formamide pyrimidine DNA glycosylase (Fpg) enzyme, as well as the micronucleus test, respectively. Meglumine antimoniate induced an increase in the DNA damage after digestion with Fpg, reinforcing its mutagenic potential by oxidizing DNA bases, which was prevented by genistein. Similarly, ascorbic acid was capable of reducing mutagenic effects in simultaneous treatment as well as in posttreatment. Therefore, our results demonstrate that both compounds are efficient in preventing mutations in mammalian cells treated with meglumine antimoniate.

Genistein Improves Skin Flap Viability in Rats: A Preliminary In Vivo and In Vitro Investigation

Selective estrogen receptor modulators (SERMs) have been developed to achieve beneficial effects of estrogens while minimizing their side effects. In this context, we decided to evaluate the protective effect of genistein, a natural SERM, on skin flap viability in rats and in a series of in vitro experiments on endothelial cells (migration, proliferation, antioxidant properties, and gene expression profiling following genistein treatment). Our results showed that administration of genistein increased skin flap viability, but importantly, the difference is only significant when treatment is started 3 days prior the flap surgery. Based on our in vitro experiments, it may be hypothesized that the underlying mechanism may rather by mediated by increasing SOD activity and Bcl-2 expression. The gene expression profiling further revealed 9 up-regulated genes (angiogenesis/inflammation promoting: CTGF, CXCL5, IL-6, ITGB3, MMP-14, and VEGF-A; angiogenesis inhibiting: COL18A1, TIMP-2, and TIMP-3). In conclusion, we observed a protective effect of genistein on skin flap viability which could be potentially applied in plastic surgery to women undergoing a reconstructive and/or plastic intervention. Nevertheless, further research is needed to explain the exact underlying mechanism and to find the optimal treatment protocol.

In Vitro Estrogenic and Breast Cancer Inhibitory Activities of Chemical Constituents Isolated from Rheum undulatum L

We investigated the estrogenic and breast cancer inhibitory activities of chemical constituents isolated from Rhei undulati Rhizoma (roots of Rheum undulatum L.), which is used as a laxative, an anti-inflammatory, and an anti-blood stagnation agent. Estrogen-like activity was studied using the well characterized E-screen assay in estrogen receptor (ER)-positive MCF-7 cells. The mechanism underlying the breast cancer inhibitory activity of the compounds was studied using human ER-negative MDA-MB-231 and ER-positive MCF-7 cells. The activation of apoptosis pathway-related proteins was investigated by western blotting, using extracts of R. undulatum prepared in three solvent conditions (EX1, EX2, and EX3). The R. undulatum chemical constituents (compounds 1⁻3) showed estrogen-like activity in the concentration range of 10 to 50 μM, by increasing the proliferation of human ER-positive MCF-7 cells. These effects were attenuated by co-treatment with 100 nM fulvestrant, an ER antagonist. Compounds 1⁻3 decreased the viability of MCF-7 cells in a concentration-dependent manner. Compounds 1 (aloe emodin) and 2 (rhapontigenin) induced mitochondria-independent apoptosis by activating the caspase-8 pathway, whereas the cytotoxic effect of compound 3 (chrysophanol 1-O-β-d-glucopyranoside) was mediated through the mitochondria-dependent apoptotic pathway.

Daidzein reductase of Eggerthella sp. YY7918, its octameric subunit structure containing FMN/FAD/4Fe-4S, and its enantioselective production of R-dihydroisoflavones

S-Equol is a metabolite of daidzein, a type of soy isoflavone, and three reductases are involved in the conversion of daidzein by specific intestinal bacteria. S-Equol is thought to prevent hormone-dependent diseases. We previously identified the equol producing gene cluster (eqlABC) of Eggerthella sp. YY7918. Daidzein reductase (DZNR), encoded by eqlA, catalyzes the reduction of daidzein to dihydrodaidzein (the first step of equol synthesis), which was confirmed using a recombinant enzyme produced in Escherichia coli. Here, we purified recombinant DZNR to homogeneity and analyzed its enzymological properties. DZNR contained FMN, FAD, and one 4Fe-4S cluster per 70-kDa subunit as enzymatic cofactors. DZNR reduced the CC bond between the C-2 and C-3 positions of daidzein, genistein, glycitein, and formononetin in the presence of NADPH. R-Dihydrodaidzein and R-dihydrogenistein were highly stereo-selectively produced from daidzein and genistein. The K_m and k_cat for daidzein were 11.9 μM and 6.7 s^-1, and these values for genistein were 74.1 μM and 28.3 s^-1, respectively. This enzyme showed similar kinetic parameters and wide substrate specificity for isoflavone molecules. Thus, this enzyme appears to be an isoflavone reductase. Gel filtration chromatography and chemical cross-linking analysis of the active form of DZNR suggested that the enzyme consists of an octameric subunit structure. We confirmed this by small-angle X-ray scattering and transmission electron microscopy at a magnification of ×200,000. DZNR formed a globular four-petal cloverleaf structure with a central vertical hole. The maximum particle size was 173 Å.

Novel vitexin-inspired scaffold against leukemia

Acute lymphoblastic leukemia (ALL) is the most common type of leukemia in children. Up to a quarter of ALL patients relapse and face poor prognosis. To identify new compound leads, we conducted a phenotypic screen using terrestrial natural product (NP) fractions against immortalized ALL cellular models. We identified vitexin, a flavonoid, as a promising hit with biological activity (EC₅₀ = 30 μM) in pre-B cell ALL models with no toxicity against normal human tissue (BJ cells) at the tested concentrations. To develop more potent compounds against ALL and elucidate its potential mode of action, a vitexin-inspired compound library was synthesized. Thus, we developed an improved and scalable protocol for the direct synthesis of 4-quinolone core heterocycles containing an N-sulfonamide using a one-pot condensation reaction protocol. The newly generated compounds represent a novel molecular scaffold against ALL as exemplified by compounds 13 and 15, which demonstrated EC₅₀ values in the low micromolar range (0.3-10 μM) with little to no toxicity in normal cellular models. Computational studies support the hypothesis that these compounds are potential CDK inhibitors. The compounds induced apoptosis, caused cell arrest at G0/G1 and G2/M, and induced ROS in cancer cells.

Genistein inhibits the S-phase kinase-associated protein 2 expression in breast cancer cells

Breast cancer is one of the most lethal cancers affecting women worldwide and was estimated to account for ~30% of all new cancer diagnoses in women. Although available evidence has proved the tumor suppressor role of genistein in cancer, the underling mechanisms have remained to be fully elucidated. S-phase kinase-associated protein 2 (Skp2) has been revealed to critically enhance the pathogenesis of multiple human cancers. The present study determined whether genistein exerts its anti-tumor function by suppressing Skp2 in breast cancer cells. Genistein significantly inhibited the proliferation, invasion and migration of breast cancer cells. Furthermore, genistein treatment also induced marked apoptosis and a typical cell cycle arrest in G2/M phase. Mechanistically, genistein treatment was identified to cause a significant downregulation of Skp2. Two crucial tumor suppressors, p21 and p27, were upregulated in genistein-treated breast cancer cells. The present results revealed that genistein exerted its tumor suppressor effect at least partially via inhibition of Skp2 and promotion of its downstream targets p21 and p27. Therefore, inactivation of Skp2 by genistein may be a promising approach for breast cancer treatment.

Calycosin inhibits the in vitro and in vivo growth of breast cancer cells through WDR7-7-GPR30 Signaling

BACKGROUND

Clinically, breast cancer is generally classified into estrogen receptor-positive (ER+) or estrogen receptor-negative (ER-) subtypes. The phytoestrogen calycosin has been shown to inhibit the proliferation of ER+ cells, which may be mediated by a feedback loop that involves miR-375, RAS dexamethasone-induced 1 (RASD1), and ERα. However, how calycosin acts on ER- breast cancer cells remains unclear.

RESULTS

Here, we show that calycosin inhibited the proliferation of both ER- (MDA-MB-468 and SKBR3) and ER+ breast cancer cells (MCF-7 and T47D) and that these inhibitory effects were associated with the up-regulation of the long non-coding RNA (lncRNA) WDR7-7. For the first time, we demonstrate that the expression of WDR7-7 is reduced in breast cancer cell lines and that the overexpression of WDR7-7 inhibits growth through a mechanism that involves G-protein coupled estrogen receptor 30 (GPR30). Meanwhile, we show that calycosin stimulated the WDR7-7-GPR30 signaling pathway in MCF-7, T47D, MDA-MB-468, and SKBR3 breast cancer cells. In contrast, in MCF10A and GPR30-deficient MDA-MB-231 cells, due to a lack of WDR7-7-GPR30 for activation, calycosin failed to inhibit cell growth. Additionally, in all four GPR30-positive breast cancer lines, calycosin decreased the phosphorylation levels of SRC, EGFR, ERK1/2 and Akt, but the inhibition of WDR7-7 blocked these changes and increased proliferation. In mice bearing MCF-7 or SKBR3 xenografts, tumor growth was inhibited by calycosin, and changes in expression the levels of WDR7-7 and GPR30 in tumor tissues were similar to those in cultured MCF-7 and SKBR3 cells.

CONCLUSIONS

These results suggest the possibility that calycosin inhibited the proliferation of breast cancer cells, at least partially, through WDR7-7-GPR30 signaling, which may explain why calycosin can exert inhibitory effects on ER- breast cancer.

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.

Establishment of primary mixed cell cultures from spontaneous canine mammary tumors: Characterization of classic and new cancer-associated molecules

There are many factors which make canine cancer like cancer in humans. The occurrence of spontaneous mammary tumors in pet dogs, tumor genetics, molecular targets and exposure to the same environmental risk factors are among these factors. Therefore, the study of canine cancer can provide useful information to the oncology field. This study aimed to establish and characterize a panel of primary mixed cell cultures obtained from spontaneous canine mammary tumors. Eight established cell cultures obtained from one normal mammary gland, one complex adenoma, one mixed adenoma, two complex carcinomas and two mixed carcinomas were analyzed. The gene expression levels of classic molecular cancer players such as fibroblast growth factor receptor (FGFR) 2, breast cancer (BRCA) 1, BRCA2 and estrogen receptor (ESR) 1 were evaluated. For the first time, three orphan nuclear receptors, estrogen-related receptors (ERRs) α, β and γ were studied in canine mammary cancer. The highest expression level of ERRα was observed in complex carcinoma-derived cell culture, while the highest levels of ERRβ and γ were observed in cells derived from a mixed carcinoma. Meanwhile, complex carcinomas presented the highest levels of expression of ESR1, BRCA1 and FGFR2 among all samples. BRCA2 was found exclusively in complex adenoma. The transcription factor GATA3 had its highest levels in mixed carcinoma samples and its lowest levels in complex adenoma. Proliferation assays were also performed to evaluate the mixed cell cultures response to ER ligands, genistein and DES, both in normoxia and hypoxic conditions. Our results demonstrate that morphological and functional studies of primary mixed cell cultures derived from spontaneous canine mammary tumors are possible and provide valuable tool for the study of various stages of mammary cancer development.

Potential of plant polyphenols to combat oxidative stress and inflammatory processes in farm animals

Polyphenols are secondary plant metabolites which have been shown to exert antioxidative and antiinflamma tory effects in cell culture, rodent and human studies. Based on the fact that conditions of oxidative stress and inflammation are highly relevant in farm animals, polyphenols are considered as promising feed additives in the nutrition of farm animals. However, in contrast to many studies existing with model animals and humans, potential antioxidative and antiinflammatory effects of polyphenols have been less investigated in farm animals so far. This review aims to give an overview about potential antioxidative and antiinflammatory effects in farm animals. The first part of the review highlights the occurrence and the consequences of oxidative stress and inflammation on animal health and performance. The second part of the review deals with bioavailability and metabolism of polyphenols in farm animals. The third and main part of the review presents an overview of the findings from studies which investigated the effects of polyphenols of various plant sources in pigs, poultry and cattle, with particular consideration of effects on the antioxidant system and inflammation.

Antiangiogenic cancer treatment: The great discovery and greater complexity (Review)

The discovery of tumor angiogenesis opened a new path in fighting cancer. The approval of different antiangiogenic agents, most targeting vascular endothelial growth factor (VEGF) signaling, has either increased the effectiveness of standard chemotherapy or even replaced it by offering better patient outcomes. However, an increasing number of preclinical and clinical observations have shown that the process of angiogenesis is far from clearly understood. Apart from targeting the VEGF pathway, novel strategies aim to influence other molecular factors that are involved in tumor angiogenesis. In addition, naturally occurring compounds seem to offer additional agents for influencing angiogenesis. The first concept of antiangiogenic therapy aimed to destroy tumor vessels, while it turned out that, paradoxically, antiangiogenic drugs normalized vasculature and as a result offered an improvement in chemotherapeutic delivery. In order to design an effective treatment schedule, methods for detecting the time window of normalization and biomarkers predicting patient response are needed. The initial idea that antiangiogenic therapy would be resistance-free failed to materialize and currently we still face the obstacle of resistance to antiangiogenic therapy.

Phytoestrogens and Mycoestrogens Induce Signature Structure Dynamics Changes on Estrogen Receptor α

Endocrine disrupters include a broad spectrum of chemicals such as industrial chemicals, natural estrogens and androgens, synthetic estrogens and androgens. Phytoestrogens are widely present in diet and food supplements; mycoestrogens are frequently found in grains. As human beings and animals are commonly exposed to phytoestrogens and mycoestrogens in diet and environment, it is important to understand the potential beneficial or hazardous effects of estrogenic compounds. Many bioassays have been established to study the binding of estrogenic compounds with estrogen receptor (ER) and provided rich data in the literature. However, limited assays can offer structure information with regard to the ligand/ER complex. Our current study surveys the global structure dynamics changes for ERα ligand binding domain (LBD) when phytoestrogens and mycoestrogens bind. The assay is based on the structure dynamics information probed by hydrogen deuterium exchange mass spectrometry and offers a unique viewpoint to elucidate the mechanism how phytoestrogens and mycoestrogens interact with estrogen receptor. The cluster analysis based on the hydrogen deuterium exchange (HDX) assay data reveals a unique pattern when phytoestrogens and mycoestrogens bind with ERα LBD compared to that of estradiol and synthetic estrogen modulators. Our study highlights that structure dynamics could play an important role in the structure function relationship when endocrine disrupters interact with estrogen receptors.

The Impact of Soy Isoflavones on MCF-7 and MDA-MB-231 Breast Cancer Cells Using a Global Metabolomic Approach

Despite substantial research, the understanding of the chemopreventive mechanisms of soy isoflavones remains challenging. Promising tools, such as metabolomics, can provide now a deeper insight into their biochemical mechanisms. The purpose of this study was to offer a comprehensive assessment of the metabolic alterations induced by genistein, daidzein and a soy seed extract on estrogen responsive (MCF-7) and estrogen non-responsive breast cancer cells (MDA-MB-231), using a global metabolomic approach. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that all test compounds induced a biphasic effect on MCF-7 cells and only a dose-dependent inhibitory effect on MDA-MB-231 cells. Proton nuclear magnetic resonance (¹H-NMR) profiling of extracellular metabolites and gas chromatography-mass spectrometry (GC-MS) profiling of intracellular metabolites confirmed that all test compounds shared similar metabolic mechanisms. Exposing MCF-7 cells to stimulatory concentrations of isoflavones led to increased intracellular levels of 6-phosphogluconate and ribose 5-phosphate, suggesting a possible upregulation of the pentose phosphate pathway. After exposure to inhibitory doses of isoflavones, a significant decrease in glucose uptake was observed, especially for MCF-7 cells. In MDA-MB-231 cells, the glutamine uptake was significantly restricted, leading to alterations in protein biosynthesis. Understanding the metabolomic alterations of isoflavones represents a step forward in considering soy and soy derivates as functional foods in breast cancer chemoprevention.

Genistein Induces Apoptosis and Inhibits Proliferation of HT29 Colon Cancer Cells

Soybean isoflavone genistein has multiple anticancer properties and its pro-apoptotic and anti-proliferative effects have been studied in different cancer cells. However, the mechanisms of action of genistein and its molecular targets on human colon cells have not been fully elucidated. Therefore, caspase-3 and p38 mitogen-activated protein kinase (p38 MAPK) as the main therapeutic targets were investigated in this study at both gene expression and protein levels in HT29 colon cancer cells. The caspase-3 and p38 MAPK gene expression levels were examined by real time PCR whereas flow cytometry technique was performed to determine their intracellular protein levels. The caspase-3 enzyme activity was obtained by colorimetric method while the gelatinase activity of matrix metalloproteinase-2 (MMP2) was determined by zymography. In addition, MTT test, wound healing assay and clonogenic assay were carried out to determine the effect of genistein on HT29 cell viability, migration, and proliferation, respectively. Genistein induced apoptotic death in HT29 cells through activation of caspase-3 pathway at the transcriptional, protein, and enzymatic levels. Moreover, genistein inhibited the proliferation of HT29 cells by reducing of both p38 MAPK gene expression and its active phosphorylated protein level. Also, we showed that genistein strongly suppressed the metastatic potency of HT29 colon cancer cells via the reduction of MMP2 activity. Based on the results of this study, we conclude that genistein may exhibit its anticancer properties on HT29 colon cancer cells by modulating caspase-3 and p38 MAPK pathway at different transcriptional and protein levels.