Inhibition of human breast cancer growth by GCP (genistein combined polysaccharide) in xenogeneic athymic mice: involvement of genistein biotransformation by beta-glucuronidase from tumor tissues

Gut microbial beta-glucuronidase: a vital regulator in female estrogen metabolism

A growing amount of evidence has supported that gut microbiota plays a vital role in the reproductive endocrine system throughout a woman's whole life, and gut microbial β-glucuronidase (gmGUS) is a key factor in regulating host estrogen metabolism. Moreover, estrogen levels also influence the composition as well as the diversity of gut microbiota. In normal condition, the gmGUS-estrogen crosstalk maintains body homeostasis of physiological estrogen level. Once this homeostasis is broken, the estrogen metabolism will be disturbed, resulting in estrogen-related diseases, such as gynecological cancers, menopausal syndrome, etc. together with gut microbial dysbiosis, which may accelerate these pathological processes. In this review, we highlight the regulatory role of gmGUS on the physical estrogen metabolism and estrogen-related diseases, summarize the present evidence of the interaction between gmGUS and estrogen metabolism, and unwrap the potential mechanisms behind them. Finally, gmGUS may become a potential biomarker for early diagnosis of estrogen-induced diseases. Regulating gmGUS activity or transplanting gmGUS-producing microbes shows promise for treating estrogen-related diseases.

Understanding the Phytoestrogen Genistein Actions on Breast Cancer: Insights on Estrogen Receptor Equivalence, Pleiotropic Essence and Emerging Paradigms in Bioavailability Modulation

Prevalent as a major phenolic ingredient of soy and soy products, genistein is recognized as an eminent phytoestrogen owing to its interacting ability with estrogen receptors (ERs). The metabolic conversion of plant-derived genistin to genistein by gut microbes and intestinal enzymes enhances its absorption at intestinal pH of ~7.5-7.8. Genistein interferes in breast cancer (BC) development via pleiotropic actions on cell proliferation, survival, angiogenesis, and apoptosis. Though multiple investigations have demonstrated genistein intake-driven reduced BC risk, similar efficacy has not been replicated in clinical trials. Furthermore, multiple studies have structurally and functionally equated genistein extents with 17-β-estradiol (E2), the most available physiological estrogen in females, culminating in aggravated BC growth. Of note, both genistein and E2 function via interacting with ERs (ERα and ERβ). However, although E2 shows almost equal affinity towards both ERα and ERβ, genistein shows more affinity towards ERβ than ERα. Our cautious literature survey revealed typical intake mode, ER expression pattern and the ratio of ERα and ERβ, transactivators/ regulators of ERα and ERβ expression and activities, patient age, and menopausal status as decisive factors affecting genistein BC activities. Of further interest are the mechanisms by which genistein inhibits triple-negative breast cancers (TNBCs), which lack ERs, progesterone receptors (PRs), and human epidermal growth factor receptors (HER2). Herein, we attempt to understand the dosage-specific genistein actions in BC cells and patients with an insight into its better response via derivative development, nanocarrier-assisted, and combinatorial delivery with chemotherapeutic drugs.

Microbial polysaccharides: An emerging family of natural biomaterials for cancer therapy and diagnostics

Microbial polysaccharides (MPs) offer immense diversity in structural and functional properties. They are extensively used in advance biomedical science owing to their superior biodegradability, hemocompatibility, and capability to imitate the natural extracellular matrix microenvironment. Ease in tailoring, inherent bio-activity, distinct mucoadhesiveness, ability to absorb hydrophobic drugs, and plentiful availability of MPs make them prolific green biomaterials to overcome the significant constraints of cancer chemotherapeutics. Many studies have demonstrated their application to obstruct tumor development and extend survival through immune activation, apoptosis induction, and cell cycle arrest by MPs. Synoptic investigations of MPs are compulsory to decode applied basics in recent inclinations towards cancer regimens. The current review focuses on the anticancer properties of commercially available and newly explored MPs, and outlines their direct and indirect mode of action. The review also highlights cutting-edge MPs-based drug delivery systems to augment the specificity and efficiency of available chemotherapeutics, as well as their emerging role in theranostics.

Dietary Phenolics against Breast Cancer. A Critical Evidence-Based Review and Future Perspectives

Breast cancer (BC) is the most common malignancy and the leading cause of cancer-related death in adult women worldwide. Over 85% of BC cases are non-hereditary, caused by modifiable extrinsic factors related to lifestyle, including dietary habits, which play a crucial role in cancer prevention. Although many epidemiological and observational studies have inversely correlated the fruit and vegetable consumption with the BC incidence, the involvement of their phenolic content in this correlation remains contradictory. During decades, wrong approaches that did not consider the bioavailability, metabolism, and breast tissue distribution of dietary phenolics persist behind the large currently existing gap between preclinical and clinical research. In the present review, we provide comprehensive preclinical and clinical evidence according to physiologically relevant in vitro and in vivo studies. Some dietary phenolics such as resveratrol (RSV), quercetin, isoflavones, epigallocatechin gallate (EGCG), lignans, and curcumin are gaining attention for their chemopreventive properties in preclinical research. However, the clinical evidence of dietary phenolics as BC chemopreventive compounds is still inconclusive. Therefore, the only way to validate promising preclinical results is to conduct clinical trials in BC patients. In this regard, future perspectives on dietary phenolics and BC research are also critically discussed.

Prevention effect of quercetin and its glycosides on obesity and hyperglycemia through activating AMPKα in high-fat diet-fed ICR mice

Quercetin and its glycosides possess various health beneficial functions, but comparative study of them on energy metabolism in different tissues are not well studied. In this study, we investigated AMP-activated protein kinase regulated glucose metabolism in the skeletal muscle and lipid metabolism in the white adipose tissue and liver to compare the effectiveness of quercetin and its glycosides, namely isoquercitrin, rutin, and enzymatically modified isoquercitrin, in male ICR mice. The mice were fed a standard or high-fat diet supplemented with 0.1% quercetin and its glycosides for 13 weeks. Quercetin glycosides, but not quercetin, decreased body weight gain and fat accumulation in the mesenteric adipose tissue in high-fat groups. All compounds decreased high-fat diet-increased plasma glucose and insulin levels. Moreover, all compounds significantly increased AMP-activated protein kinase phosphorylation in either standard or high-fat diet-fed mice in all tissues tested. As its downstream events, all compounds induced glucose transporter 4 translocation in the muscle. In the white adipose tissue and liver, all compounds increased lipogenesis while decreased lipolysis. Moreover, all compounds increased browning markers and decreased differentiation markers in adipose tissue. Therefore, quercetin and its glycosides are promising food components for prevention of adiposity and hyperglycemia through modulating AMP-activated protein kinase-driven pathways.

Overestimation of flavonoid aglycones as a result of the ex vivo deconjugation of glucuronides by the tissue β-glucuronidase

Flavonoid glucuronides are the main circulating metabolites of flavonoids in humans and animals. There has been a growing interest in the biological function of glucuronides. In order to differentiate biological activity and to assess efficacy it is essential to accurately determine the levels of flavonoid aglycone and metabolic conjugate in vivo. Many organs and body fluids of humans and animals exhibit β-glucuronidase against flavonoid glucuronides. Studies have shown that β-glucuronidase within the tissues hydrolyzes glucuronides to their aglycones during the tissue extraction, leading to artificially higher reported tissue levels of aglycone than actual in vivo concentrations. The aims of this study were to estimate the extent by which the aglycones were overestimated and to investigate the use of saccharo-1,4-lactone, a β-glucuronidase inhibitor, to block the ex vivo hydrolysis of flavonoid glucuronides. Our data demonstrate that in mouse liver tissues and human tumor xenografts levels of quercetin and methylated quercetin aglycones could be over-estimated by 7-fold. The inhibition of deconjugation of quercetin and baicalein glucuronides by saccharo-1,4-lactone is dose-dependent. The amount of saccharo-1,4-lactone used to produce optimal inhibition of the enzyme activity is in the range of 15-24μmol per gram of liver tissue. The use of β-glucuronidase inhibitor blocks the ex vivo deconjugation resulting in an accurate estimation of tissue levels of aglycone and conjugate. Our study described here can be extended to other animal models and human studies with different types of substrates of β-glucuronidase.

Isoflavone phytoestrogens in soymilk fermented with β-glucosidase producing probiotic lactic acid bacteria

Isoflavones significantly contribute to human health and disease prevention, and exist as glucosides and aglycones. The β-glucosidase enzyme that hydrolyzes glucosides to aglycones is very sensitive to molecular structure, and thus the profile of the isoflavones can affect their rate of hydrolysis. Soymilk was fermented with Lactobacillus acidophilus B4496 (La), Lactobacillus bulgaricus CFR2028 (Lb), Lactobacillus casei B1922 (Lc), Lactobacillus plantarum B4495 (Lp) and Lactobacillus fermentum B4655 (Lf) for 48 h at 37°C. β-Glucosidase activity was determined using p-nitrophenyl β-D-glucopyranoside as a substrate and the hydrolysis was carried out in soymilk. During fermentation, maximum growth was seen at 24 h with Lb, Lc, Lp and Lf and at 48 h with La. Polyphenol content ranged from 12.98 to 17.90 at 24 h and from 12.44 to 15.24 mg/100 ml at 48 h of fermentation. All the lactic acid bacteria produced β-glucosidase enzyme, which hydrolyzed isoflavone glucosides to aglycones at a significant level (P < 0.05) in the fermented soymilk.

Expanded Utility of the β-Glucuronide Linker: ADCs That Deliver Phenolic Cytotoxic Agents

The β-glucuronide linker has been used for antibody-drug conjugates (ADCs) to deliver amine-containing cytotoxic agents. The linker is stable in circulation, hydrophilic and provides ADCs that are highly active in vitro and in vivo. To extend the utility of the β-glucuronide linker toward phenol-containing drugs, an N,N'-dimethylethylene diamine self-immolative spacer was incorporated with the linker for release of the potent cytotoxic phenol psymberin A. Exposure of the drug-linker to β-glucuronidase resulted in facile drug release. The corresponding ADCs were active and immunologically selective against CD30-positive L540cy and CD70-positive Caki-1 cell lines.

Influence of natural coagulants on isoflavones and antioxidant activity of tofu

Tofu (instead of preparing using synthetic coagulant) was prepared using coagulants of plant origin (Citrus limonum, Garcinia indica, Tamarindus indica, Phyllanthus acidus and Passiflora edulis). Total crude protein and fat contents were highest in tofu prepared using G. indica and T. indica (72.5% dbw) compared to synthetic coagulant. Tofu prepared with natural coagulants had signifi cantly higher antioxidant activity compared to synthetic coagulant. Bioconversion of isoflavone glucosides (daidzin and genistin) into their corresponding bioactive aglycones (daidzein and genistein) was observed in tofu. The difference between glucosides and aglycones contents in soy milk was significant but there was not much difference in tofu coagulated with synthetic and natural coagulants.

Quercetin aglycone is bioavailable in murine pancreas and pancreatic xenografts

Quercetin is a potential chemopreventive and chemotherapeutic agent for pancreatic and other cancers. This study examined the distribution of quercetin in plasma, lung, liver, pancreas, and pancreatic cancer xenografts in a murine in vivo model and the uptake of quercetin in pancreatic cancer MiaPaCa-2 cells in a cellular in vitro model. Mice were randomly allocated to control or 0.2 and 1% quercetin diet groups utilizing the AIN93G-based diet (n = 12 per group) for 6 weeks. In addition, 6 mice from each group were injected weekly with the chemotherapeutic drug gemcitabine (120 mg/kg mouse, ip). MiaPaCa cells were collected from culture medium after cells were exposed to 30 muM quercetin for 0.5, 1, 2, 4, 8, and 24 h. Levels of quercetin and 3-O'-methylquercetin in mouse tissues and MiaPaCa-2 cells were measured by high-pressure liquid chromatography following enzymatic hydrolysis and then extraction. The study showed that quercetin is accumulated in pancreatic cancer cells and is absorbed in the circulating system, tumors, and tissues of pancreas, liver, and lung in vivo. A higher proportion of total quercetin found in tumors and pancreas is aglycones. Gemcitabine cotreatment with quercetin reduced absorption of quercetin in the mouse circulatory system and liver. Results from the study provide important information on the interpretation of the chemotherapeutic efficacy of quercetin.

Effect of genistein and daidzein on the proliferation and differentiation of human preadipocyte cell line

Isoflavones are known to have several biological activities, including a hypolipidemic effect. However, the mechanism of the lipid lowering effect of genistein remains to be elucidated. There is conflicting evidence on the effect of genistein for the deposition of adipocyte tissues. We examined the effect of the isoflavones on the growth and differentiation of human preadipocyte cells, AML-I. Growth arrest accompanied by the appearance of characteristics of apoptosis was observed by genistein or daidzein treatment under the adipogenic stimulation. The expressions of apoptosis-related proteins, Bad, Akt, and p-Akt, were modulated in the genistein-treated cells by Western blot analysis. On the other hand, exposure of AML-I to the isoflavones increased accumulation of cytoplasmic lipid droplets. Actually, the cytoplasmic expressions of fatty acid synthase (FAS) and peroxisome proliferator-activated receptor (PPAR)-gamma were increased in the genistein-treated cells. Glycosylated forms of the isoflavones genistein and puerarin did not have such activities. These results suggested that only aglycon forms of isoflavones induced not only apoptosis but also lipogenesis in the preadipocyte cell line AML-I. The possible mechanism of these phenomena has been discussed in the text.

Nanobioengineering and Characterization of a Novel Estrogen Receptor Biosensor

We constructed an original supramolecular assembly on a surface of sensor composed of an innovative combination of an engineered cytochrome b5 and a modified nucleic acid bound to a synthetic lipid hemimembrane. The protein/DNA block, called (PDNA) 2, was synthesized and purified before its immobilization onto a hybrid bilayer reconstituted on a gold surface. Surface plasmon resonance (SPR) and atomic force microscopy (AFM) were engaged in parallel on the same substrates in order to better understand dynamic events that occur at the surface of the biosensor. Good correlations were obtained in terms of specificity and reversibility. These findings allow us to present a first application of such biosensor in the study of the interaction processes between nuclear receptor and DNA.

GCP-mediated growth inhibition and apoptosis of prostate cancer cells via androgen receptor-dependent and -independent mechanisms

BACKGROUND

Genistein combined polysaccharide (GCP) is a nutritional supplement that can inhibit prostate cancer growth experimentally and clinically. It is composed predominantly of the isoflavones genistein, daidzein, and glycitein, which have anti-cancer properties. Although genistein is well studied, the properties of GCP are not well defined. The goal of this work was to better characterize the signaling pathways impacted by GCP in an effort to optimize its efficacy.

METHODS

Cell growth and apoptosis were evaluated by MTS proliferation, caspase-based assays, and flow cytometry. Modulation of androgen receptor (AR) levels and activation status of signaling molecules were monitored by immunoblot analysis. AR function was measured by evaluating prostate-specific antigen (PSA) message and protein levels and by reporter assays.

RESULTS

GCP inhibited proliferation of androgen-dependent LNCaP and androgen-independent LNCaP-p53(GOF) and 22Rv1 cell lines in a dose-dependent manner and cells were more responsive in the presence of androgen. GCP markedly suppressed mTOR-p70S6K signaling while Akt and p53 were only modestly modulated. GCP significantly attenuated androgen signaling as evidenced by diminished AR protein levels and a consequent reduction in transcriptional activity and PSA expression. AR expression was enhanced by de-repression of translation with inhibitors of PI3K-Akt-mTOR signaling and by inhibition of proteasome-dependent degradation. Neither inhibitor could counteract GCP-mediated AR downregulation, suggesting the involvement of a mechanism(s) independent of these pathways.

CONCLUSIONS

Our results suggest that GCP mediates growth inhibition and apoptosis through multiple mechanisms including (1) molecular mimicry of androgen ablation (via AR downregulation) and (2) by providing an AR-independent, pro-apoptotic signal (mTOR inhibition).

Isoflavones made simple - genistein's agonist activity for the beta-type estrogen receptor mediates their health benefits

Soy isoflavones, the focus of much research and controversy, are often referred to as "weak estrogens". In fact, genistein is a relatively potent agonist for the recently characterized beta isoform of the estrogen receptor (ERbeta). The low nanomolar serum concentrations of unconjugated free genistein achieved with high-nutritional intakes of soy isoflavones are near the binding affinity of genistein for this receptor, but are about an order of magnitude lower than genistein's affinity for the "classical" alpha isoform of the estrogen receptor (ERalpha). Moreover, these concentrations are far too low to inhibit tyrosine kinases or topoisomerase II, in vitro activities of genistein often cited as potential mediators of its physiological effects. The thesis that these physiological effects are in fact mediated by ERbeta activation provides a satisfying rationale for genistein's clinical activities. Hepatocytes do not express ERbeta; this explains why soy isoflavones, unlike oral estrogen, neither modify serum lipids nor provoke the prothrombotic effects associated with increased risk for thromboembolic disorders. The lack of uterotrophic activity of soy isoflavones reflects the fact that ERalpha is the exclusive mediator of estrogen's impact in this regard. Vascular endothelium expresses both ERalpha and ERbeta, each of which has the potential to induce and activate nitric oxide synthase; this may account for the favorable influence of soy isoflavones on endothelial function in postmenopausal women and ovariectomized rats. The ERbeta expressed in osteoblasts may mediate the reported beneficial impact of soy isoflavones on bone metabolism. Suggestive evidence that soy-rich diets decrease prostate cancer risk, accords well with the observation that ERbeta appears to play an antiproliferative role in healthy prostate. In the breast, ERalpha promotes epithelial proliferation, whereas ERbeta has a restraining influence in this regard - consistent with the emerging view that soy isoflavones do not increase breast cancer risk, and possibly may diminish it. Premenopausal women enjoy a relative protection from kidney failure; since ERbeta is an antagonist of TGF-beta signaling in mesangial cells, soy isoflavones may have nephroprotective potential. Estrogen also appears to protect women from left ventricular hypertrophy, and recent evidence suggests that this effect is mediated by ERbeta. In conjunction with reports that isoflavones may have a modestly beneficial impact on menopausal symptoms - perhaps reflecting the presence of ERbeta in the hypothalamus - these considerations suggest that soy isoflavone regimens of sufficient potency may represent a safe and moderately effective alternative to HRT in postmenopausal women. Further clinical research is required to characterize the impact of optimal genistein intakes on endothelial and bone function in men. Studies with ERbeta-knockout mice could be helpful for clarifying whether ERbeta does indeed mediate the chief physiological effects of low nanomolar genistein. S-equol, a bacterial metabolite of daidzein, has an affinity for ERbeta nearly as high as that of genistein; whether this compound contributes meaningfully to the physiological efficacy of soy isoflavones in some individuals is still unclear.

The Role of β-Glucuronidase in Induction of Apoptosis by Genistein Combined Polysaccharide (GCP) in Xenogeneic Mice Bearing Human Mammary Cancer Cells

In order to reveal the mechanisms underlying genistein combined polysaccharide (GCP) inhibition of tumor proliferation, we investigated the effects of GCP on the growth of human breast cancer cells transplanted to athymic nude mice. We further investigated the metabolism of genistein and its association with the beta-glucuronidase activity in tumor and normal tissues.

Tissue distribution of quercetin in rats and pigs

Quercetin is a dietary polyphenolic compound with potentially beneficial effects on health. Claims that quercetin has biological effects are based mainly on in vitro studies with quercetin aglycone. However, quercetin is rapidly metabolized, and we have little knowledge of its availability to tissues. To assess the long-term tissue distribution of quercetin, 2 groups of rats were given a 0.1 or 1% quercetin diet [approximately 50 or 500 mg/kg body weight (wt)] for 11 wk. In addition, a 3-d study was done with pigs fed a diet containing 500 mg quercetin/kg body wt. Tissue concentrations of quercetin and quercetin metabolites were analyzed with an optimized extraction method. Quercetin and quercetin metabolites were widely distributed in rat tissues, with the highest concentrations in lungs (3.98 and 15.3 nmol/g tissue for the 0.1 and 1% quercetin diet, respectively) and the lowest in brain, white fat, and spleen. In the short-term pig study, liver (5.87 nmol/g tissue) and kidney (2.51 nmol/g tissue) contained high concentrations of quercetin and quercetin metabolites, whereas brain, heart, and spleen had low concentrations. These studies have for the first time identified target tissues of quercetin, which may help to understand its mechanisms of action in vivo.

SOY AND THE PREVENTION OF LIFESTYLE-RELATED DISEASES

1. Epidemiological studies suggest that consumption of soy foods is associated with reduced risks of cardiovascular disease, and breast and prostate cancers. 2. Clinical intervention studies indicate that some soy components, especially soy isoflavone-containing soy protein isolate, reduced serum total cholesterol and LDL-cholesterol. 3. Animal studies generally support the conclusion that some soy components prevent the development and progression of breast and prostate cancers. 4. Epidemiological investigations and intervention studies suggest that some soy products are effective for the relief of menopausal symptoms.

Effects of a genistein-rich extract on PSA levels in men with a history of prostate cancer

OBJECTIVES

To determine whether supplemental amounts of soy isoflavone (genistein-rich extract) would lower prostate-specific antigen (PSA) levels more than 50% in patients with prostate cancer (CaP).

METHODS

A total of 62 men (mean age 73.6 years, range 61.4 to 89.3) with histologically proven CaP who had two consecutive elevated PSA readings were accrued during a 13-month period. An open-label pilot study was conducted for 6 months in which the patients took capsules containing the genistein-rich extract three times daily by mouth. The subjects were in one of five groups: after radical retropubic prostatectomy (n = 9), after radiotherapy (n = 17), after both radical retropubic prostatectomy and radiotherapy (n = 6), off-cycle during hormonal therapy (intermittent hormones; n = 14), or active surveillance (n = 16). The primary endpoint for the trial was a 50% reduction in the PSA level at 6 months compared with before treatment.

RESULTS

Of the 62 men enrolled, 52 were available for evaluation at 6 months. Three patients discontinued because of adverse events (diarrhea) and seven because of personal choice. One of 52 patients had a more than 50% reduction in the PSA level (1.9% response, 95% confidence interval 0.1% to 10.3%). An additional 7 patients had PSA reductions that were less than 50%. All 8 patients with lower PSA levels at 6 months were in the active surveillance (watchful waiting) treatment subgroup. Repeated measure regression models allowing for correlation between initial levels and change also indicated a decline in PSA in this group compared with other groups: 0 of 52 had a complete response, 9 (17%) had a partial response, 8 (15%) had stable disease, and 35 (67%) had disease progression. In the 9 patients with a partial response, 6 had pathologic findings that were moderately differentiated, 2 had well-differentiated findings, and 1 had poorly differentiated findings. Therefore, the response in this group of patients did not appear to be driven by the Gleason score. The total testosterone level was lowered in one of the patients responding, but it was higher in five others.

CONCLUSIONS

A genistein-rich extract as the sole treatment for CaP did not reduce PSA levels by 50% or more in 51 of 52 subjects. Thus, it does not appear to be an effective treatment for CaP when given alone. However, 8 of 13 evaluated patients in the active surveillance group had either no rise or a decline in PSA levels of less than 50%. More study is warranted for those choosing active surveillance.

Health benefits of soy isoflavonoids and strategies for enhancement: a review

Soybean consumption has been linked to a reduced risk for certain cancers and diseases of old age. The health benefits associated with soybean consumption have been linked to the action of isoflavonoids, the major phenolic phytochemicals found in soybean. Isoflavonoids possess numerous biological activities that may support chemoprevention through the promotion of apoptosis in diseased cells. In this study, we discuss the current state of knowledge concerning soybean isoflavonoids, their chemopreventive actions against postmenopausal health problems, cancer, and cardiovascular disease, and also biotechnology approaches toward the enrichment of soybean for isoflavonoid content.

Dietary and medicinal antimutagens and anticarcinogens: molecular mechanisms and chemopreventive potential--highlights of a symposium

Antimutagens and anticarcinogens are common amongst many traditional herbal remedies and dietary therapies. With increased understanding of the mechanistic basis of cancer development and cancer prevention, we are now better aware of ways in which some of these traditional remedies may act at the cellular or subcellular levels. This special issue features some of the highlights of the conference on this topic that was held in Seoul on October 17-19, 2001.