Genistein blocks breast cancer cells in the G2M phase of the cell cycle

Unveiling the therapeutic potential of natural-based anticancer compounds inducing non-canonical cell death mechanisms

In the Mid-19th century, Rudolf Virchow considered necrosis to be a prominent form of cell death; since then, pathologists have recognized necrosis as both a cause and a consequence of disease. About a century later, the mechanism of apoptosis, another form of cell death, was discovered, and we now know that this process is regulated by several molecular mechanisms that "programme" the cell to die. However, discoveries on cell death mechanisms are not limited to these, and recent studies have allowed the identification of novel cell death pathways that can be molecularly distinguished from necrotic and apoptotic cell death mechanisms. Moreover, the main goal of current cancer therapy is to discover and develop drugs that target apoptosis. However, resistance to chemotherapeutic agents targeting apoptosis is mainly responsible for the failure of clinical therapy and adverse side effects of the chemotherapeutic agents currently in use pose a major threat to the well-being and lives of patients. Therefore, the development of natural-based anticancer drugs with low cellular and organismal side effects is of great interest. In this comprehensive review, we thoroughly examine and discuss natural anticancer compounds that specifically target non-canonical cell death mechanisms.

Structural mechanism of human oncochannel TRPV6 inhibition by the natural phytoestrogen genistein

Calcium-selective oncochannel TRPV6 is the major driver of cell proliferation in human cancers. While significant effort has been invested in the development of synthetic TRPV6 inhibitors, natural channel blockers have been largely neglected. Here we report the structure of human TRPV6 in complex with the plant-derived phytoestrogen genistein, extracted from Styphnolobium japonicum, that was shown to inhibit cell invasion and metastasis in cancer clinical trials. Despite the pharmacological value, the molecular mechanism of TRPV6 inhibition by genistein has remained enigmatic. We use cryo-EM combined with electrophysiology, calcium imaging, mutagenesis, and molecular dynamics simulations to show that genistein binds in the intracellular half of the TRPV6 pore and acts as an ion channel blocker and gating modifier. Genistein binding to the open channel causes pore closure and a two-fold symmetrical conformational rearrangement in the S4-S5 and S6-TRP helix regions. The unprecedented mechanism of TRPV6 inhibition by genistein uncovers new possibilities in structure-based drug design.

Genistein, a Potential Phytochemical against Breast Cancer Treatment-Insight into the Molecular Mechanisms

Breast cancer (BC) is one of the most common malignancies in women. Although widespread successful synthetic drugs are available, natural compounds can also be considered as significant anticancer agents for treating BC. Some natural compounds have similar effects as synthetic drugs with fewer side effects on normal cells. Therefore, we aimed to unravel and analyze several molecular mechanisms of genistein (GNT) against BC. GNT is a type of dietary phytoestrogen included in the flavonoid group with a similar structure to estrogen that might provide a strong alternative and complementary medicine to existing chemotherapeutic drugs. Previous research reported that GNT could target the estrogen receptor (ER) human epidermal growth factor receptor-2 (HER2) and several signaling molecules against multiple BC cell lines and sensitize cancer cell lines to this compound when used at an optimal inhibitory concentration. More specifically, GNT mediates the anticancer mechanism through apoptosis induction, arresting the cell cycle, inhibiting angiogenesis and metastasis, mammosphere formation, and targeting and suppressing tumor growth factors. Furthermore, it acts via upregulating tumor suppressor genes and downregulating oncogenes in vitro and animal model studies. In addition, this phytochemical synergistically reverses the resistance mechanism of standard chemotherapeutic drugs, increasing their efficacy against BC. Overall, in this review, we discuss several molecular interactions of GNT with numerous cellular targets in the BC model and show its anticancer activities alone and synergistically. We conclude that GNT can have favorable therapeutic advantages when standard drugs are not available in the pharma markets.

In vitro evaluation of Annona muricata L. (Soursop) leaf methanol extracts on inhibition of tumorigenicity and metastasis of breast cancer cells

PURPOSE

The present study evaluates the in-vitro anti-tumorigenic potential of leaf methanol extracts of Annona muricata (LMAM).

MATERIALS AND METHODS

The cytotoxic activity was assessed in MCF-7 cells by MTT assay at various concentrations ranging from 25-250µg/mL. MCF-7 cells were treated with 50 and 100 µg/mL LMAM for 24 h. To detect LMAM-induced apoptosis; Hoescht 33342 staining along with Cell cycle analysis, Annexin-PI probe as well as oxidative stress damage by reactive oxygen species (ROS) measurements were determined using flow cytometric analysis. While caspase-3 expression levels were studied employing the qRT-PCR method.

RESULTS

LMAM exhibited significant inhibition of MCF-7 cells with an IC₅₀ value of 85.55 µg/mL. Hoescht staining showed marked morphological features characteristic of apoptosis in LMAM treated cells. Cell cycle analysis confirmed the proven capability of LMAM showing a 30% rise in G₁ phase upon treatment with 100 µg/mL LMAM, thus inducing cell cycle arrest at G₁ phase and a rise in sub G₀-G₁ population paralleled with a decrease in S phase. Flow cytometric analysis with Annexin V-FITC-PI staining indicated an increase in the early and late apoptotic population with a 3.38% and 19.47% rise respectively when treated with 100 µg/mL LMAM. Treatment with 100 µg/mL LMAM caused an increase in intracellular ROS with MFI value 3334.08. Upregulation of caspase-3 was observed with a 2.18 and 32.47 fold increase compared to control in MCF-7 cells cultured at 50 µg/mL and 100 µg/mL LMAM respectively suggesting caspase-dependent apoptosis.

CONCLUSION

LMAM proved as a potent ethno-chemopreventive agent and a potential lead in cancer treatment attributable to the synergistic interactive properties of phytoconstituents.

Tofu intake is inversely associated with risk of breast cancer: A meta-analysis of observational studies

Observational studies on the association between tofu intake and breast cancer incidence have reported inconsistent results. We reviewed the current evidence and quantitatively assessed this association by conducting a dose-response meta-analysis. The electronic databases PubMed and EMBASE were searched for relevant studies published up to August, 2018. We included epidemiological studies that reported relative risks (RRs) or odds ratios (ORs) with 95% confidence intervals (CIs) for the association between tofu intake and breast cancer risk. A total of 14 studies (2 cohort studies, 12 case-control studies) were included in the meta-analysis. The overall OR of breast cancer for highest vs lowest intake of tofu was 0.78 (95% CI 0.69–0.88), with moderate heterogeneity (P = 0.011, I² = 49.7%). Dose-response analysis based on 5 case-control studies revealed that each 10 g/d increase in tofu intake was associated with 10% reduction in the risk of breast cancer (95% CI 7%–13%, P = 0.037, I² = 40.8%). In summary, our findings suggest an inverse dose-response association between tofu intake and risk of breast cancer. However, owing to the limitations of case-control studies, more properly designed prospective studies are warranted to confirm this association.

Genistein Inhibits Proliferation of BRCA1 Mutated Breast Cancer Cells: The GPR30-Akt Axis as a Potential Target

Background

BRCA1 mutated breast cancer cells exhibit the elevated cell proliferation and the higher metastatic potential. G protein-coupled receptor 30 (GPR30) has been shown to regulate growth of hormonally responsive cancers, such as ovarian and breast cancers, and high expression of GPR30 is found in estrogen receptor (ER)-negative breast cancer cells. ER-negative breast cancer patients often have a mutation in the tumor suppressor gene, BRCA1. This study explored antiproliferative effects of genistein, a chemopreventive isoflavone present in legumes, and underlying molecular mechanisms in triple negative breast cancer cells with or without functionally active BRCA1.

Methods

Expression of BRCA1, GPR30 and Nrf2 was measured by Western blot analysis. Reactive oxygen species (ROS) accumulation was monitored by using the fluorescence-generating probe, 2’,7’-dichlorofluorescein diacetate. The effects of genistein on breast cancer cell viability and proliferation were assessed by the MTT, migration and clonogenic assays.

Results

The expression of GPR30 was dramatically elevated at both transcriptional and translational levels in BRCA1 mutated breast cancer cells compared to cells with wild-type BRCA1. Notably, there was diminished Akt phosporylation in GPR30 silenced cells. Treatment of BRCA1 silenced breast cancer cells with genistein resulted in the down-regulation of GPR30 expression and the inhibition of Akt phosphorylation as well as the reduced cell viability, migration and colony formation. Genistein caused cell cycle arrest at the G2/M phase in BRCA1-mutant cells through down-regulation of cyclin B1 expression. Furthermore, BRCA1-mutant breast cancer cells exhibited higher levels of intracellular ROS than those in the wild-type cells. Genistein treatment lowered the ROS levels through up-regulation of Nrf2 expression.

Conclusions

Lack of functional BRCA1 activates GPR30 signaling, thereby stimulating Akt phosphorylation and cell proliferation. Genistein induces G2/M phase arrest by down-regulating cyclin B1 expression, which is attributable to its suppression of GPR30 activation and Akt phosphorylation in BRCA1 impaired breast cancer cells.

Genistein inhibits proliferation and induces senescence in neonatal mouse pituitary gland explant cultures

Genistein is an isoflavone abundant in soybean and infants are exposed to high levels of genistein in soy-based formula. It is known that genistein mediates estrogen receptor (ER) signaling, and exposure during neonatal development could cause acute and long term endocrine effects. We assayed genistein's impact on the neonatal mouse pituitary gland because it is an endocrine signaling hub and is sensitive to endocrine disruption during critical periods. Pituitary explant cultures, which actively proliferate and differentiate, were exposed to 0.06 μM-36 μM genistein and assayed for mRNA and protein changes. Genistein induced mRNA expression of the ERα regulated gene, Cckar, to the same magnitude as estradiol (E2) but with less potency. Interestingly, 36 μM genistein strongly inhibited pituitary proliferation, measured by a reduction in mKi67 mRNA and phospho-Histone H3 immunostaining. Examining cell cycle dynamics, we found that 36 μM genistein decreased Ccnb1 (Cyclin B1) mRNA; while mRNA for the cyclin dependent kinase inhibitor Cdkn1a (p21) was upregulated, correlated with an apparent increase in p21 immunostained cells. Strikingly, we observed a robust onset of cellular senescence, permanent cell cycle exit, in 36 μM genistein treated pituitaries by increased senescence activated β-galactosidase staining. We also found that 36 μM genistein decreased Bcl2 mRNA levels, a gene protective against apoptosis. Taken together these data suggest that genistein exposure during the neonatal period could initiate senescence and halt proliferation during a time when the proper numbers of endocrine cells are being established for mature gland function.

Molecular Targets of Genistein and Its Related Flavonoids to Exert Anticancer Effects

Increased health awareness among the public has highlighted the health benefits of dietary supplements including flavonoids. As flavonoids target several critical factors to exert a variety of biological effects, studies to identify their target-specific effects have been conducted. Herein, we discuss the basic structures of flavonoids and their anticancer activities in relation to the specific biological targets acted upon by these flavonoids. Flavonoids target several signaling pathways involved in apoptosis, cell cycle arrest, mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/AKT kinase, and metastasis. Polo-like kinase 1 (PLK1) has been recognized as a valuable target in cancer treatment due to the prognostic implication of PLK1 in cancer patients and its clinical relevance between the overexpression of PLK1 and the reduced survival rates of several carcinoma patients. Recent studies suggest that several flavonoids, including genistein directly inhibit PLK1 inhibitory activity. Later, we focus on the anticancer effects of genistein through inhibition of PLK1.

Cotargeting Plk1 and androgen receptor enhances the therapeutic sensitivity of paclitaxel-resistant prostate cancer

Backgrounds:

Despite the clinical success of taxanes, they still have limitations, such as chemoresistance. To overcome the limitations of paclitaxel, genetic alterations and targeting effects of altered genes were observed in paclitaxel-resistant cancer. Because paclitaxel-resistant cancer shows high levels of Plk1, a promising target in chemotherapy, the effectiveness of Plk1 inhibitors in paclitaxel-resistant cancer cells has been investigated.

Methods:

Paclitaxel-resistant cancer cells were developed by exposure of stepwise escalating levels of paclitaxel. Genetic alterations were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunoblotting. Using a cell viability assay, combined targeting effects for Plk1 and androgen receptor (AR) were determined. Clinical data were analyzed to understand the relationship between Plk1 and AR in prostate cancer patients.

Results:

Treatment with Plk1 inhibitors markedly reduced the expression of MDR1, MRP1, and Plk1 in the paclitaxel-resistant cancer. Among Plk1 inhibitors, genistein, recently found as a direct Plk1 inhibitor, tended to be more effective in the paclitaxel-resistant prostate cancer than the parental cancer cells, which was related to the suppression of the AR, as well as inhibition of Plk1 activity. A combination of Plk1 inhibitors and AR antagonist bicalutamide exhibited a synergistic effect in LNCaP^TXR, as well as LNCaP cells, by inhibiting Plk1 and AR. Analysis of clinical data provides evidence for the relevance between Plk1 and AR in prostate cancer patients, showing that Plk1 and AR are strong predictors of poor survival rates.

Conclusions:

We suggest that cotargeting Plk1 and AR would be effective in advanced chemoresistant prostate cancer cells to overcome the limitations associated with paclitaxel.

Solubilization of Genistein in Phospholipid Vesicles and Their Atioxidant Capacity

Water-insoluble genistein was solubilized in aqueous medium by using phospholipid vesicles composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycerophosphocholine (DOPC) with 0-30% cholesterol. For each vesicle, the maximum solubilization amount of genistein was investigated by X-ray scattering measurement. In addition, the antioxidant capacity of the solubilized genistein was evaluated by the ABTS assay. Genistein was found to be solubilized by 10-20% and 40-50% of the vesicle concentrations of pure DPPC and DOPC respectively. The maximum solubilization amount of genistein decreased to 0-10% and 20-30% when 30% of cholesterol is present in the respective vesicles. Cholesterol is solubilized in a hydrophobic core whereas genistein is solubilized in the polar head region or in the polar-apolar interface. The overlapping of solubilizing sites affected the solubilization of genistein when cholesterol was present in the vesicles. Moreover, the lamellar interval was largely affected by cholesterol in compared to the little impact of genistein because the later can indirectly affect the acyl chains. Genistein solubilized in DOPC showed the same degree of antioxidant capacity as that of vesicle-free genistein system. On the other hand, genistein solubilized in DPPC had lower antioxidant activity than the former systems. The distinction of antioxidant activity at different systems probably related to the difference of accessibility of ABTS radical cation to solubilized genistein through different vesicles. Finally, cholesterol-free DOPC vesicles were found to be the best solubilizer for genistein among the investigated systems.

Polyfluorinated iodine alkanes regulated distinct breast cancer cell progression through binding with estrogen receptor alpha or beta isoforms

Polyfluorinated iodine alkanes (PFIs) are a kind of emerging chemicals with endocrine disrupting effects. Based on the different binding preferences of PFIs to estrogen receptor alpha and beta isoforms (ERα and β), two representative PFIs, dodecafluoro-1,6-diiodohexane (PFHxDI) and tridecafluorohexyl iodide (PFHxI), were selected to evaluate their effects on the proliferation of two kinds of breast cancer cells with different ERα/β expression levels, MCF-7 and T47D. The cell viability assay showed PFHxDI could cause higher cellular toxicity than did PFHxI in both MCF-7 and T47D. MCF-7 with relatively higher ERα/β expression ratio was more vulnerable to the cytotoxic treatments of PFHxI and PFHxDI when compared with T47D cells with relatively lower ERα/β expression ratio. EdU incorporation and cell cycle analysis revealed that, similar to 17β-estrodiol (E₂), non-cytotoxic levels of PFHxDI could significantly promote the proliferation of MCF-7 by increasing cell population at S phase (p < 0.01), while T47D proliferation was not influenced by PFHxI exposure due to cell cycle arrest at G2/M phase. The cellular responses caused by estrogenic PFIs were dominantly mediated by their preferential binding affinities for ER isoforms, which would be helpful in the accurate assessment for their potential influences on the breast cancer progression.

Effect of Genistein in Comparison with Trichostatin A on Reactivation of DNMTs Genes in Hepatocellular Carcinoma

Background and Aims: DNA methylation and histone modification are epigenetic modifications essential for normal function of mammalian cells. The processes are mediated by biochemical interactions between DNA methyltransferases (DNMTs) and histone deacetylases. Promoter hypermethylation and deacetylation of tumor suppressor genes play major roles in cancer induction, through transcriptional silencing of these genes. DNA hypermethylation is carried out by a family of DNMTs including DNMT1, DNMT3a and DNMT3b. In hepatocellular carcinoma, a significant positive correlation between over-expression of these genes and cancer induction has been reported. The DNA demethylating agent genistein (GE) has been demonstrated to reduce different cancers. Previously, we reported that GE can induce apoptosis and inhibit proliferation in hepatocellular carcinoma PLC/PRF5 and HepG2 cell lines. Besides, histone deacetylase inhibitors, such as trichostatin A (TSA), were successfully used to inhibit cancer cell growth. The present study was designed to assess the effect of GE in comparison with TSA on DNMT1, DNMT3a and DNMT3b gene expression, cell growth inhibition and apoptosis induction in the HepG2 cell line. Methods: Cells were seeded and treated with various doses of GE and TSA. The MTT assay, flow cytometry assay, and real-time RT-PCR were used to determine viability, apoptosis, and DNMT1, DNMT3a and DNMT3b gene expression respectively. Results: Both agents inhibited cell growth, induced apoptosis and reactivated DNMT1, DNMT3a and DNMT3b gene expression. Furthermore, TSA demonstrated a significantly greater apoptotic effect than the other agent, whereas GE improved gene expression more significantly than TSA. Conclusions: Our findings suggest that GE and TSA can significantly inhibit cell growth, induce apoptosis and restore DNMT1, DNMT3a and DNMT3b gene reactivation.

Integrating virtual screening and biochemical experimental approach to identify potential anti-cancer agents from drug databank

Chemical libraries constitute a reservoir of pharmacophoric molecules to identify potent anti-cancer agents. Virtual screening of heterocyclic compound library in conjugation with the agonist-competition assay, toxicity-carcinogenicity analysis, and string-based structural searches enabled us to identify several drugs as potential anti-cancer agents targeting protein kinase C (PKC) as a target. Molecular modeling study indicates that Cinnarizine fits well within the PKC C2 domain and exhibits extensive interaction with the protein residues. Molecular dynamics simulation of PKC-Cinnarizine complex at different temperatures (300, 325, 350, 375, and 400[Formula: see text]K) confirms that Cinnarizine fits nicely into the C2 domain and forms a stable complex. The drug Cinnarizine was found to bind PKC with a dissociation constant Kd of [Formula: see text]M. The breast cancer cells stimulated with Cinnarizine causes translocation of PKC-[Formula: see text] to the plasma membrane as revealed by immunoblotting and immunofluorescence studies. Cinnarizine also dose dependently reduced the viability of MDAMB-231 and MCF-7 breast cancer cells with an IC[Formula: see text] of [Formula: see text] and [Formula: see text]g/mL, respectively. It is due to the disturbance of cell cycle of breast cancer cells with reduction of S-phase and accumulation of cells in G1-phase. It disturbs mitochondrial membrane potentials to release cytochrome C into the cytosol and activates caspase-3 to induce apoptosis in cancer cells. The cell death was due to induction of apoptosis involving mitochondrial pathway. Hence, the current study has assigned an additional role to Cinnarizine as an activator of PKC and potentials of the approach to identify new molecules for anti-cancer therapy. Thus, in silico screening along with biochemical experimentation is a robust approach to assign additional roles to the drugs present in the databank for anti-cancer therapy.

Sensitivity of TP53-Mutated Cancer Cells to the Phytoestrogen Genistein Is Associated With Direct Inhibition of Plk1 Activity

Polo-like kinase 1 (Plk1), a conserved Ser/Thr mitotic kinase, has been identified as a promising target for anticancer drug development because its overexpression is correlated with malignancy. Here, we found that genistein, an isoflavone, inhibits Plk1 kinase activity directly. Previously the mitotic disturbance phenomenon induced by treatment with genistein was not fully explained by its inhibitory effect on EGFR. In kinase profiling assays, it showed selectivity relative to a panel of kinases, including EGFR. Treatment with genistein induced cell death in a concentration-dependent manner in cancer cells from diverse tissue origins, but not in non-transformed cells such as hTERT-RPE or MCF10A cells. We also observed that genistein tended to be more selective against cancer cells with mutations in the TP53 gene. TP53-depeleted LNCaP and NCI-H460 cells using shRNA targeting human TP53 were more sensitive to cell death by treatment of genistein. Furthermore, genistein induced mitotic arrest by inhibiting Plk1 activity and, consequently, led to mitotic catastrophe and apoptosis. These data suggest that genistein may be a promising anticancer drug candidate due to its inhibitory activity against Plk1 as well as EGFR and effectiveness toward cancer cells, especially those with p53-mutation. J. Cell. Physiol. 232: 2818-2828, 2017. © 2016 Wiley Periodicals, Inc.

The role of soybean extracts and isoflavones in hormone-dependent breast cancer: aromatase activity and biological effects

Estrogen receptor-positive (ER+) breast cancer is the most common cause of cancer death in women worldwide. Nowadays, the relationship between soya diet and breast cancer is controversial due to the unknown role of its isoflavones, genistein (G) and daidzein (D). In this work, we investigated not only the anti-tumor properties of a soybean extract (NBSE) but also whether the biotransformation of extract (BSE) by the fungus Aspergillus awamori increased its effectiveness. The BSE showed a stronger anti-aromatase activity and anti-proliferative efficacy in ER+ aromatase-overexpressing breast cancer cells. D and G were weak aromatase inhibitors, but inhibited cancer cell growth, being G the isoflavone that contributed to the BSE-induced effects. This work demonstrated that the biotransformation increased the anti-aromatase activity and the anti-tumoral efficacy of soybean extract in breast cancer cells. Moreover, it elucidated the potential use of soya in the prevention and/or treatment of ER+ breast cancer.

Premature or pathological aging: longevity

Abstract The main objective of this literature review was to summarize and characterize the main factors and events that may negatively influence quality of life and human longevity. The factors that act on premature aging processes are essentially the same as those of natural or healthy aging, but in a more intense and uncontrolled manner. Such factors are: 1) genetic (genome); 2) metabolic (metabolome); 3) environmental (life conditions and style, including diet). Factors 1 and 2 are more difficult to control by individuals; once depending on socioeconomic, cultural and educational conditions. Differently of environmental factors that may be totally controlled by individuals. Unfamiliarity with these factors leads to chronic and/or degenerative diseases that compromise quality of life and longevity.

Phytoestrogens Induce Differential Estrogen Receptor Alpha- or Beta-Mediated Responses in Transfected Breast Cancer Cells

Increased intake of phytoestrogens may be associated with a lower risk of cancer in the breast and several other sites, although there is controversy surrounding this activity. One of the mechanisms proposed to explain the activity of phytoestrogens is their ability to bind and activate human estrogen receptor a (ERα) and human estrogen receptor β (ERβ). Nine phytoestrogens were tested for their ability to transactivate ERα or ERβ at a range of doses. Mammary adenocarcinoma (MCF-7) cells were co-transfected with either ERα or ERβ, and an estrogen-response element was linked to a luciferase reporter gene. Dose-dependent responses were compared with the endogenous ligand 17β-estradiol. Purified genistein, daidzein, apigenin, and coumestrol showed differential and robust transactivation of ERα- and ERβ-induced transcription, with an up to 100-fold stronger activation of ERβ. Equol, naringenin, and kaempferol were weaker agonists. When activity was evaluated against a background of 0.5 nM 17β-estradiol, the addition of genistein, daidzein, and resveratrol superstimulated the system, while kaempferol and quercetin were antagonists at the highest doses. This transfection assay provides an excellent model to evaluate the activation of ERα and ERβ by different phytoestrogens in a breast cancer context and can be used as a screening bioassay tool to evaluate the estrogenic activity of extracts of herbs and foods.

Quantitative phosphoproteomics reveals genistein as a modulator of cell cycle and DNA damage response pathways in triple-negative breast cancer cells

Around one sixth of breast cancer cases are classified as triple-negative breast cancer (TNBC), named after the absence of the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2); however, patients with TNBC suffer from poor clinical outcome and shortage of targeted therapy. Genistein, an estrogenic soy isoflavone, shows anticancer effects in TNBC cells such as inducing G2/M cell cycle arrest and apoptosis. However, the underlying mechanism of its anticancer effects is poorly understood and its elucidation can help the development of novel therapeutic strategies for TNBC. In this study, by combining isobaric tag-based TMT labeling with titanium dioxide-based phosphopeptide enrichment, we quantitated 5,445 phosphorylation sites on 2,008 phosphoproteins in the TNBC cell line MDA-MB-231, upon genistein treatment. Our analysis revealed 332 genistein-regulated phosphorylation sites on 226 proteins. Our data show that genistein can regulate several biological processes during the cell cycle, including DNA replication, cohesin complex cleavage, and kinetochore formation. Furthermore, genistein can also activate DNA damage response, including activation of ATR and BRCA1 complex. Overall, our study presents evidence at a phosphoproteomic level that genistein is able to inhibit TNBC cell growth by regulating the cell cycle and DNA damage response in a more complex manner. Our findings help elucidate the mechanisms through which genistein exerts its anticancer effects in TNBC cells.

Potential therapeutic mechanism of genistein in breast cancer involves inhibition of cell cycle regulation

Genistein can prevent tumorigenesis and reduce the incidence of diseases that are dependent upon estrogen. Previous research, however, has shown that genistein can also increase the risk of breast cancer. Thus, the aim of the present study was to investigate the mechanism underlying the effect of genistein in breast cancer and to determine whether genistein produces a therapeutic effect or promotes the development of breast cancer. Gene microarray data obtained from three samples treated with alcohol (control group), three samples treated with 3 μmol/l genistein and three samples treated with 10 μmol/l genistein for 48 h, were downloaded from the Gene Expression Omnibus database. Analysis of the differentially expressed genes (DEGs) and functional enrichment in the two genistein groups was performed. The interaction networks of the DEGs were constructed and the overlapping network was extracted. Finally, the functions and pathways of the DEGs in the overlapping network were enriched. In total, 224 DEGs coexisted in the two genistein groups, and the most significant function of these was the cell cycle. The number and the fold change of expression values of the DEGs in the 10 μmol/l genistein group were significantly higher compared with that of the 3 μmol/l genistein group. The most significant function and pathway of the DEGs in the overlapping network was the cell cycle involving several genes, including GLIPR1, CDC20, BUB1, MCM2 and CCNB1. Thus, genistein stimulation resulted in gene expression changes in breast cancer cell lines and discrepancies increased with higher doses of genistein. The DEGs were most significantly associated with cell cycle regulation.

Genistein decreases cellular redox potential, partially suppresses cell growth in HL‑60 leukemia cells and sensitizes cells to γ‑radiation‑induced cell death

Various mechanisms have been proposed to underlie the cellular activity of genistein, based on biological experiments and epidemiological studies. The present study demonstrated that genistein inhibited the expression of cytoplasmic nicotinamide adenine dinucleotide phosphate (NADP)‑dependent isocitrate dehydrogenase (cICDH), thus increasing levels of intracellular reactive oxygen species (ROS) in human promyeloid leukemia HL‑60 cells. In genistein‑treated cells, the cellular redox potential (GSH/GSSG) was significantly decreased. This decrease in redox potential was caused by significant downregulation of the cICDH gene, generating the reducing equivalents (NADPH) for maintenance of cellular redox potential and cellular ROS level, which may regulate cell growth and cell death. Genistein‑induced ROS partially induced rapid transition into the G2/M phase by upregulation of p21wap1/cip1 and apoptotic cell death. Treatment of cells with N‑acetylcysteine, a well‑known antioxidant (ROS scavenger), not only partially restored cell growth and inhibited cell cycle arrest in G2/M, but also prevented apoptotic cell death. By contrast, normal lymphocytes did not significantly progress into the G2/M phase and radiation‑induced cell death was inhibited by genistein treatment. Therefore, genistein and γ‑irradiation together synergistically cause cell death in leukemia cells, however, genistein has a radioprotective effect in normal human lymphocytes. In conclusion, it was suggested that genistein selectively functions, not as an antioxidant, but as a pro‑oxidant in HL‑60 cells. This property can increase ionizing radiation‑induced cell cycle arrest and sensitivity to apoptotic cell death in human promyeloid leukemia HL‑60 cells, but does not cause significant damage to normal cells.

Genistein induces cytokinesis failure through RhoA delocalization and anaphase chromosome bridging

Genistein, an isoflavone abundantly present in soybeans, possesses anticancer properties and induces growth inhibition including cell cycle arrest and apoptosis. Although abnormal cell division, such as defects in chromosome segregation and spindle formation, and polyploidization have been described, the mechanisms underlying the induction of abnormal cell division are unknown. In this study, we examined the effect of genistein on cell division in cells that are synchronized in M phase, since genistein treatment delays mitotic entry in asynchronous cells. HeLa S3 cells were arrested at the G2 phase and subsequently released into the M phase in presence of genistein. Immunofluorescence staining showed that genistein treatment delays M phase progression. Time-lapse analysis revealed that the delay occurs until anaphase onset. In addition, genistein treatment induces cleavage furrow regression, resulting in the generation of binucleated cells. Central spindle formation, which is essential for cytokinesis, is partially disrupted in genistein-treated cells. Moreover, aberrant chromosome segregation, such as a chromosome bridge and lagging chromosome, occurs through progression of cytokinesis. RhoA, which plays a role in the assembly and constriction of an actomyosin contractile ring, is delocalized from the cortex of the ingressing cleavage furrow. These results suggest that genistein treatment induces binucleated cell formation through cleavage furrow regression, which is accompanied by chromosome bridge formation and RhoA delocalization. Our results provide the mechanism that underlies genistein-induced polyploidization, which may be involved in genistein-induced growth inhibition.

Pro-apoptotic and anti-adhesive effects of four African plant extracts on the breast cancer cell line MCF-7

Background

Jatropha curcas (JCP1), Pyrenacantha staudtii (PS), Picralima nitida (ZI) and Jatropha gossypifolia (JCP2) are plants used in the African folklore for the treatment of various cancers.

Methods

This study investigated the in vitro anticancer effects of the ethanol extracts against human epithelial MCF-7 breast cancer cells in a dose-dependent manner (1–50 μg/ml) by using cell cycle analysis, viability assay, annexin V/PI staining, TUNEL method and expression determination of apoptotic and adhesion relevant proteins. Adhesion processes were monitored by detachment via flow cytometry, β1-integrin expression and formation of the actin cytoskeleton.

Results

The three extracts, termed PS, JCP1 and JCP2 at a concentration of 10 μg/ml induced cell death in MCF-7 breast cancer cells verified by high amounts of PI-positive cells in the cell cycle analysis, Annexin V/PI staining and DNA fragmentation measurements. In parallel cell detachment was accompanied by decreased β1- integrin expression and phosphorylation of the focal adhesion kinase at Tyr397. ZI extract was the exception by the increasing β1-integrin expression and strengthening the cortical actin cytoskeleton. However, all four plant extracts mediated strong anti-cancer properties with IC₅₀ values between 23–38 μg/ml.

Conclusion

PS, JCP1 and JCP2 were found to be very active against MCF-7 cells by inducing anoikis and therefore possessing vast potential as medicinal drugs especially in estrogen receptor positive breast cancer treatment. ZI mediated their anti-cancer action by different signaling mechanisms which should be analyzed in future studies. Our results further supported the idea that medicinal plants can be promising sources of putative anticancer agents.

Electronic supplementary material

The online version of this article (doi:10.1186/1472-6882-14-334) contains supplementary material, which is available to authorized users.

Isorhamnetin suppresses colon cancer cell growth through the PI3K‑Akt‑mTOR pathway

Isorhamnetin, a flavonoid isolated from the fruits of herbal medicinal plants, such as Hippophae rhamnoides L., exerts anticancer effects similar to other flavonoids. However, the effect of isorhamnetin on colorectal cancer (CRC) and the underlying molecular mechanism are unclear. This study aimed to determine the effect of isorhamnetin on the proliferation of cells from the human CRC cell lines, HT‑29, HCT116 and SW480. It was demonstrated that isorhamnetin suppressed the proliferation of cells from all three cell lines, induced cell cycle arrest at the G2/M phase and suppressed cell proliferation by inhibiting the PI3K‑Akt‑mTOR pathway. Isorhamnetin also reduced the phosphorylation levels of Akt (ser473), phosph‑p70S6 kinase and phosph‑4E‑BP1 (t37/46) protein, and enhanced the expression of Cyclin B1 protein. Therefore, this compound was revealed to be a selective PI3K‑Akt‑mTOR pathway inhibitor, and may be a potent anticancer agent for the treatment of CRC, as it restrains the proliferation of CRC cells.

Hydrolysis of isoflavone glycoside by immobilization of β-glucosidase on a chitosan-carbon in two-phase system

We explored a method to examine the hydrolysis of isoflavone glycoside by immobilizing β-glucosidase on chitosan-carbon beads in an aqueous-organic two-phase system. The chitosan-carbon beads were cross-linked with glutaraldehyde to immobilize β-glucosidase from Exiguobacterium sp. DAU5. The optimal pH and temperature were 9.0 and 55 °C, respectively. Under the optimized conditions, crude and purified enzymes immobilized onto chitosan-carbon beads gave yields of 16.7% and 60%, respectively. The specific activities of immobilized crude and purified enzymes were 4.3 U/g and 6 U/g, respectively. The immobilized enzyme retained more than 80% of its maximum activity at pH 7.0-11.0, while temperature was more influential (80% activity after 40 °C for 1.5 h, but only 40% activity after 55 °C for 0.5 h, respectively. The immobilized enzyme was able to hydrolyze isoflavone glycoside in an aqueous-organic two-phase system, and the hydrolyzed products were enriched in the organic phase, making it easy to recover the products, i.e., genistein and daidein from the reaction system. These results suggest that immobilized β-glucosidase may be applicable for the industrial-scale hydrolysis of isoflavone glycoside.

Rapid magnetic solid-phase extraction for the selective determination of isoflavones in soymilk using baicalin-functionalized magnetic nanoparticles

Most protocols of sample preparation for isoflavone determination in soymilk and other liquid soybean products involves tedious freeze-drying and time-consuming extraction procedures. We report a facile and rapid magnetic solid-phase extraction (MSPE) of isoflavones from soymilk for subsequent high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) analysis. The extraction was based on the selective binding of isoflavones to baicalin-functionalized core-shell magnetic nanoparticles (BMNPs). The proposed MSPE-HPLC-MS/MS analytical method had a linear calibration curve in the concentration range from 0.3 to 80 mg/L isoflavones. With the use of calycosin, an isomer of one of the isoflavones targeted as an internal standard, interday (5 days) precisions of the slope and intercept of the calibration curves were found to be in the range between 2.5% and 3.6% (RSD, n = 5). Six isoflavones, that is, daidzein, glycitein, genistein, daidzin, glycitin, and genistin were detected in commercial soymilk samples and quantified by the proposed analytical method. The results indicated that the method was useful for fast determination of isoflavones in soymilk and other liquid soybean products.

Soy extracts suppressed iodine uptake and stimulated the production of autoimmunogen in rat thyrocytes

Soy consumption is associated with thyroid disorders such as hypothyroidism, goiter, and autoimmune thyroid disease (ATD) as well as increased iodine requirement in certain cases. However, the anti-thyroid component(s) in soy are yet to be identified and the molecular mechanism(s) involved remain unclear. This study examined the effects of soy isoflavones (ISF) on iodide uptake and expression of thyroglobulin (Tg) and sodium/iodide symporter (NIS) in thyrocytes. Fischer rat thyroid cells (FRTL) were treated with Novasoy (a soy alcohol extract containing 30% ISF) or major ISF aglycones or glycosides for 24 h. Iodide uptake was measured by a colorimetric assay. The protein level of Tg and NIS was measured by Western blotting. Cytotoxicity of tested compounds was determined by the MTT cell proliferation assay. Iodide uptake in FRTL cells was dose-dependently suppressed by Novasoy added into the cell culture (10, 25, or 50 µg/mL, P < 0.05). However, neither the major ISF aglycones nor glycosides alone or in combination had similar effects. Novasoy (up to 200 µg/mL) had no cytotoxic effect. Novasoy (1, 10, and 50 µg/mL) and genistein (1 and 10 µM) markedly increased the protein content of a 40 kDa Tg fragment (P40, a known autoimmunogen) and non-glycosylated NIS in the FRTL cells (P < 0.05). Overall, this study demonstrated that the alcohol soluble component(s) other than the major ISF in soy remarkably inhibited iodide uptake in the FRTL cells. Soy ISF, particularly genistein, induced the production of P40, which might be responsible for the higher incidence of ATD reported in soy infant formula-fed children.

Soybean isoflavone genistein regulates apoptosis through NF-κB dependent and independent pathways

Cyclooxygenase-2 (COX-2), the key enzyme of the conversion of arachidonic acid to prostaglandins is an important regulator of inflammation and perhaps apoptosis. Genistein is an active component of legumes and other related food associated with prevention of degenerative diseases possibly through modulating certain signaling pathways. It was investigated whether the induction of apoptosis with genistein was carried out via COX-2 suppression through the regulation of NF-κB. The cox-2 positive and negative cells were used to compare the effect of genistein on the modulation of NF-κB in COX-2 expressed or non-expressed genotypic systems. Suppression of COX-2 as well as decreasing NF-κB DNA binding activity was accompanied with the induction of apoptosis in genistein-treated COX-2 expressed cells. However, in cox-2 negative cells, apoptosis occurred without any involvement of NF-κB with genistein treatement. Genistein induced apoptosis through the generation of reactive oxygen species (ROS) both of cox-2 positive and negative cells. These results suggested that genistein is capable of exihibiting NF-κB-dependent and NF-κB-independent apoptotic control via ROS generation depending on genetic cell types.

Soyfoods and soybean products: from traditional use to modern applications

Soybean products (soyfoods), reported as potential functional foods, are implicated in several health-enhancing properties, such as easing the symptoms of postmenopausal women, reducing the risk of osteoporosis, preventing cardiovascular disease, and antimutagenic effects. Isoflavone, for example, is one of the most important compounds abundantly found in soybean, mainly accounting for the health-enhancing properties as mentioned earlier. However, most biological activities of isoflavones are mainly attributed to their aglycone forms. It has also been demonstrated that isoflavone aglycones are absorbed faster and in greater amount than their glycosides in human intestines. Fortunately, deglycosylation of isoflavones can be achieved during fermentation process by several strains such as lactic acid bacteria, basidiomycetes, filamentous fungus, and Bacillus subtilis with their β-glucosidase activity. This article presents an overview of soybean's chemistry, application, state-of-the-art advances in soybean fermentation processing and products as well as their applications in food and pharmaceutical industries. Different compounds, such as isoflavone, dietary fibers, and proteins which exhibit significant bioactivities, are summarized. The roles of different microorganisms in bioconversion and enhancement of bioactivities of fermented soybean are also discussed.

Genistein inhibit cytokines or growth factor-induced proliferation and transformation phenotype in fibroblast-like synoviocytes of rheumatoid arthritis

The purpose of this research is to study the effect of genistein on cytokines or growth factor-induced proliferation and transformation phenotype of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS). RA-FLS were primarily cultured. With respective stimulation of IL-1β, TNF-α, and EGF, genistein was applied to elucidate its effect on synoviocytes' growth number, cell proliferation assay, cell cycle using cell counts, (3)H-TdR incorporation and flow cytometry, the colony numbers under anchorage-independent condition, and the expression of MMP-2 and MMP-9 in synovial fibroblasts. EGF, IL-1β, and TNF-α increased (3)H incorporation in RA-FLS, respectively. EGF augmented clone numbers of RA-FLS under anchorage-independent condition and not IL-1β and TNF-α. Genistein had an inhibitory role on cell number and (3)H-TdR incorporation of RA-FLS stimulated with IL-1β, TNF-α and EGF; genistein arrested the cell cycle at G(1) restriction point; genistein decreased colony numbers under anchorage-independent condition stimulated by EGF in serum condition. IL-1β or TNF-α increased expression of MMP-9 and MMP-2 in rheumatoid synoviocytes; EGF stimulated expression of MMP-9 but not of MMP-2; genistein suppressed production of MMP-9 more than MMP-2 induced by IL-1β or TNF-α; rMMP-9, rMMP-2, or their inhibitors had no effect on the (3)H-TdR incorporation of synovial cells. Erk1/2 inhibitor (PD098 059) had obvious inhibitory effect on the (3)H incorporation induced by TNF-α or IL-1β; inhibitors of JNK (SP600 125) had no significant effect on the (3)H incorporation. While pretreatment with PD098059 had no marked inhibitory effect on MMP-9 expression induced by TNF-α or IL-1β, SP600125 decreased significantly the MMP-9 expression induced by TNF-α or IL-1β. Neither PD098059 nor SP600 125 could inhibit the MMP-2 expression induced by TNF-α or IL-1β. Genistein inhibited IL-1β, TNF-α or EGF-induced proliferation and MMP-9 expression in fibroblast-like synoviocytes of rheumatoid arthritis; the proliferation of RA-FLS was mediated by Erk1/2 but not JNK activation, while JNK activation was involved in the signal transduction pathway leading to MMP-9 expression in rheumatoid synoviocytes.

A process for high-efficiency isoflavone deglycosylation using Bacillus subtilis natto NTU-18

In order to produce isoflavone aglycosides effectively, a process of isoflavone hydrolysis by Bacillus subtilis natto NTU-18 (BCRC 80390) was established. This process integrates the three stages for the production of isoflavone aglycosides in one single fermenter, including the growth of B. subtilis natto, production of β-glucosidase, deglycosylation of fed isoflavone glycosides. After 8 h of batch culture of B. subtilis natto NTU-18 in 2 L of soy medium, a total of 3 L of soy isoflavone glucoside solution containing 3.0 mg/mL of daidzin and 1.0 mg/mL of genistin was fed continuously over 34 h. The percentage deglycosylation of daidzin and genistin was 97.7% and 94.6%, respectively. The concentration of daidzein and genistein in the broth reached 1,066.8 μg/mL (4.2 mM) and 351 μg/mL (1.3 mM), respectively, and no residual daidzin or genistin was detected. The productivity of the bioconversion of daidzein and genistein over the 42 h of culture was 25.6 mg/L/h and 8.5 mg/L/h, respectively. This showed that this is an efficient bioconversion process for selective estrogen receptor modulator production.

Discovery of chrysoeriol, a PI3K-AKT-mTOR pathway inhibitor with potent antitumor activity against human multiple myeloma cells in vitro

This study was designed to determine the impact of chrysoeriol on proliferation and cell cycle progression in the human multiple myeloma cell lines RPMI 8226 and KM3, and its related molecular mechanisms. Chryseoriol was identified by using the phosphorylated AKT-specific cytoblot high throughput assay. CCK-8 assay was employed to examine the growth inhibition rate and IC(50) (48 h) in peripheral blood mononuclear cells (PBMNCs), RPMI 8226 and KM3 cells treated with chrysoeriol at various concentrations. Cells were labeled with 5-6-carboxyfluorescein diacetate succinimidyl ester (CFSE), and the proliferation dynamics was detected by flow cytometry and analyzed with ModFit software. The cell cycles of RPMI 8226 and KM3 cells were measured by flow cytometry when the IC(50) concentration of chrysoeriol was adopted. The alterations in cell-cycle related proteins (Cyclin B1, Cyclin D1, p21) and proteins in PI3K-AKT-mTOR pathway were determined by Western blot analysis. The results showed the proliferation of multiple myeloma cells was significantly inhibited by chrysoeriol, resulting in cell cycle arrest in G(2)/M phase. Chrysoeriol could significantly reduce the expression of p-AKT (s473) and p-4eBP1 (t37/46) protein, meanwhile enhanced Cyclin B1 and p21 protein expression. Similar effects were not observed in PBMNCs from normal donors. It was concluded that chrysoeriol was a selective PI3K-AKT-mTOR pathway inhibitor. It restrained the proliferation of human multiple myeloma cells, but didn't affect proliferation of PBMNCs from normal donors. It might exhibit the cell cycle regulatory effect via the inhibition of PI3K-AKT-mTOR signal pathway.

Inhibition of cancer cell invasion and metastasis by genistein

Genistein is a small, biologically active flavonoid that is found in high amounts in soy. This important compound possesses a wide variety of biological activities, but it is best known for its ability to inhibit cancer progression. In particular, genistein has emerged as an important inhibitor of cancer metastasis. Consumption of genistein in the diet has been linked to decreased rates of metastatic cancer in a number of population-based studies. Extensive investigations have been performed to determine the molecular mechanisms underlying genistein's antimetastatic activity, with results indicating that this small molecule has significant inhibitory activity at nearly every step of the metastatic cascade. Reports have demonstrated that, at high concentrations, genistein can inhibit several proteins involved with primary tumor growth and apoptosis, including the cyclin class of cell cycle regulators and the Akt family of proteins. At lower concentrations that are similar to those achieved through dietary consumption, genistein can inhibit the prometastatic processes of cancer cell detachment, migration, and invasion through a variety of mechanisms, including the transforming growth factor (TGF)-beta signaling pathway. Several in vitro findings have been corroborated in both in vivo animal studies and in early-phase human clinical trials, demonstrating that genistein can both inhibit human cancer metastasis and also modulate markers of metastatic potential in humans, respectively. Herein, we discuss the variety of mechanisms by which genistein regulates individual steps of the metastatic cascade and highlight the potential of this natural product as a promising therapeutic inhibitor of metastasis.

Potential health-modulating effects of isoflavones and metabolites via activation of PPAR and AhR

Isoflavones have multiple actions on cell functions. The most prominent one is the activation of estrogen receptors. Other functions are often overlooked, but are equally important and explain the beneficial health effects of isoflavones. Isoflavones are potent dual PPARα/γ agonists and exert anti-inflammatory activity, which may contribute to the prevention of metabolic syndrome, atherosclerosis and various other inflammatory diseases. Some isoflavones are potent aryl hydrocarbon receptor (AhR) agonists and induce cell cycle arrest, chemoprevention and modulate xenobiotic metabolism. This review discusses effects mediated by the activation of AhR and PPARs and casts a light on the concerted action of isoflavones.

Analytical and compositional aspects of isoflavones in food and their biological effects

This paper provides an overview of analytical techniques used to determine isoflavones (IFs) in foods and biological fluids with main emphasis on sample preparation methods. Factors influencing the content of IFs in food including processing and natural variability are summarized and an insight into IF databases is given. Comparisons of dietary intake of IFs in Asian and Western populations, in special subgroups like vegetarians, vegans, and infants are made and our knowledge on their absorption, distribution, metabolism, and excretion by the human body is presented. The influences of the gut microflora, age, gender, background diet, food matrix, and the chemical nature of the IFs on the metabolism of IFs are described. Potential mechanisms by which IFs may exert their actions are reviewed, and genetic polymorphism as determinants of biological response to soy IFs is discussed. The effects of IFs on a range of health outcomes including atherosclerosis, breast, intestinal, and prostate cancers, menopausal symptoms, bone health, and cognition are reviewed on the basis of the available in vitro, in vivo animal and human data.

Effects of a diet rich in sesame (Sesamum indicum) pericarp on the expression of oestrogen receptor α and oestrogen receptor β in rat prostate and uterus

The expression of oestrogen receptors (ERα and ERβ) in the prostate and uterus tissues of Wistar rats supplied for 8 weeks with a diet rich in sesame (Sesamum indicum) pericarp (30 %) was monitored. Eight male rats, aged 6 weeks, were divided into a control group fed on a normal diet, and an experimental one, provided with the normal diet enriched with 30 % sesame pericarp. A similar experiment was performed with female rats. At the end of the experiment, the prostate and uterus tissues were surgically removed and kept at − 80°C for up to 2 months. Western blotting and quantitative real-time PCR (qRT-PCR) methods were used in order to investigate the levels of receptor proteins and mRNA. Significant increase in the expression of ERβ in prostate and uterus was evident in both methods, while the magnitude of the observed alteration depended on the applied method. No statistically significant change was observed in the expression of ERα in uterus. In prostate, although the increase was more evident when investigated by means of qRT-PCR, the difference in expression of ERα was not statistically significant. In both tissues, a shift of the ratio of ERα:ERβ in favour of ERβ was evident, indicating, according to existing literature, a beneficial effect of the diet provided upon the health status of the organisms. It is suggested that this effect is attributed to the lignans present in the pericarp which exert phyto-oestrogenic activity.

Low concentrations of the soy phytoestrogen genistein induce proteinase inhibitor 9 and block killing of breast cancer cells by immune cells

The risks and benefits of diets and supplements containing the estrogenic soy isoflavone genistein are not well established. We report that 10 nm genistein potently induces the granzyme B inhibitor, proteinase inhibitor 9 (PI-9) in MCF-7 human breast cancer cells. By inducing PI-9, genistein inhibits the ability of human natural killer (NK) cells to lyse the target breast cancer cells. In ERalphaHA cells, stably transfected MCF-7 cells, which contain elevated levels of estrogen receptor-alpha (ERalpha), 100 pm genistein or 17beta-estradiol potently induce PI-9 and prevent NK cells from killing the target breast cancer cells. The concentrations of genistein that fully induce PI-9 in MCF-7 cells, and in ERalphaHA cells, are far lower than those previously reported to elicit estrogenic responses through ERalpha. Because 4-hydroxytamoxifen, raloxifene, and ICI 182,780/Faslodex all block genistein induction of PI-9 and elevated levels of ERalpha enhance induction of PI-9, genistein acts via ERalpha to induce PI-9. Increasing levels of ERalpha in breast cancer cells results in a progressive increase in induction of PI-9 by genistein and in the cell's ability to evade killing by NK cells. Moderate levels of dietary genistein and soy flour effectively induce PI-9 in human breast cancers grown in ovariectomized athymic mice. A significant population consumes levels of genistein in soy products that may be high enough to induce PI-9, perhaps potentiating the survival of some preexisting breast cancers by enabling them to evade immunosurveillance.

The molecular basis of genistein-induced mitotic arrest and exit of self-renewal in embryonal carcinoma and primary cancer cell lines

Background

Genistein is an isoflavonoid present in soybeans that exhibits anti-carcinogenic properties. The issue of genistein as a potential anti-cancer drug has been addressed in some papers, but comprehensive genomic analysis to elucidate the molecular mechanisms underlying the effect elicited by genistein on cancer cells have not been performed on primary cancer cells, but rather on transformed cell lines. In the present study, we treated primary glioblastoma, rhabdomyosarcoma, hepatocellular carcinoma and human embryonic carcinoma cells (NCCIT) with μ-molar concentrations of genistein and assessed mitotic index, cell morphology, global gene expression, and specific cell-cycle regulating genes. We compared the expression profiles of NCCIT cells with that of the cancer cell lines in order to identify common genistein-dependent transcriptional changes and accompanying signaling cascades.

Methods

We treated primary cancer cells and NCCIT cells with 50 μM genistein for 48 h. Thereafter, we compared the mitotic index of treated versus untreated cells and investigated the protein expression of key regulatory self renewal factors as OCT4, SOX2 and NANOG. We then used gene expression arrays (Illumina) for genome-wide expression analysis and validated the results for genes of interest by means of Real-Time PCR. Functional annotations were then performed using the DAVID and KEGG online tools.

Results

We found that cancer cells treated with genistein undergo cell-cycle arrest at different checkpoints. This arrest was associated with a decrease in the mRNA levels of core regulatory genes, PBK, BUB1, and CDC20 as determined by microarray-analysis and verified by Real-Time PCR. In contrast, human NCCIT cells showed over-expression of GADD45 A and G (growth arrest- and DNA-damage-inducible proteins 45A and G), as well as down-regulation of OCT4, and NANOG protein. Furthermore, genistein induced the expression of apoptotic and anti-migratory proteins p53 and p38 in all cell lines. Genistein also up-regulated steady-state levels of both CYCLIN A and B.

Conclusion

The results of the present study, together with the results of earlier studies show that genistein targets genes involved in the progression of the M-phase of the cell cycle. In this respect it is of particular interest that this conclusion cannot be drawn from comparison of the individual genes found differentially regulated in the datasets, but by the rather global view of the pathways influenced by genistein treatment.

Gene expression module-based chemical function similarity search

Investigation of biological processes using selective chemical interventions is generally applied in biomedical research and drug discovery. Many studies of this kind make use of gene expression experiments to explore cellular responses to chemical interventions. Recently, some research groups constructed libraries of chemical related expression profiles, and introduced similarity comparison into chemical induced transcriptome analysis. Resembling sequence similarity alignment, expression pattern comparison among chemical intervention related expression profiles provides a new way for chemical function prediction and chemical–gene relation investigation. However, existing methods place more emphasis on comparing profile patterns globally, which ignore noises and marginal effects. At the same time, though the whole information of expression profiles has been used, it is difficult to uncover the underlying mechanisms that lead to the functional similarity between two molecules. Here a new approach is presented to perform biological effects similarity comparison within small biologically meaningful gene categories. Regarding gene categories as units, a reduced similarity matrix is generated for measuring the biological distances between query and profiles in library and pointing out in which modules do chemical pairs resemble. Through the modularization of expression patterns, this method reduces experimental noises and marginal effects and directly correlates chemical molecules with gene function modules.

Cancer chemoprevention and chemotherapy: dietary polyphenols and signalling pathways

Prevention of cancer through dietary intervention recently has received an increasing interest, and dietary polyphenols have become not only important potential chemopreventive, but also therapeutic, natural agents. Polyphenols have been reported to interfere at the initiation, promotion and progression of cancer. They might lead to the modulation of proteins in diverse pathways and require the integration of different signals for the final chemopreventive or therapeutic effect. Polyphenols have been demonstrated to act on multiple key elements in signal transduction pathways related to cellular proliferation, differentiation, apoptosis, inflammation, angiogenesis and metastasis; however, these molecular mechanisms of action are not completely characterized and many features remain to be elucidated. The aim of this review is to provide insights into the molecular basis of potential chemopreventive and therapeutic activities of dietary polyphenols with emphasis in their ability to control intracellular signalling cascades considered as relevant targets in a cancer preventive approach.