Mechanistic issues concerning cancer prevention by tea catechins

Epigallocatechin gallate delays age-related cataract development via the RASSF2/AKT pathway

Age-related cataract (ARC) is a common eye disease, the main cause of which is oxidative stress-mediated apoptosis of lens epithelial cells (LECs). Epigallocatechin gallate (EGCG) is the most potent antioxidant in green tea. Our results demonstrated that EGCG could effectively reduce apoptosis of LECs and retard lens clouding in aged mice. By comparing transcriptome sequencing results of three groups of mice (young control, untreated aged, and EGCG-treated) and screening using GO and KEGG analyses, we selected RASSF2 as the effector gene of EGCG for mechanistic exploration. We verified that the differential expression of RASSF2 was associated with the occurrence of ARC in clinical samples and mouse tissues by immunohistochemistry and western blotting, respectively. We showed that high RASSF2 expression plays a crucial role in the oxidative induction of apoptosis in LECs, as revealed by overexpression and interference experiments. Further studies showed that RASSF2 mediates the inhibitory effect of EGCG on apoptosis and ARCogenesis in LECs by regulating AKT (Ser473) phosphorylation. In this study, we found for the first time the retarding effect of EGCG on lens clouding in mice and revealed the mechanism of action of RASSF2/AKT in it, which provides a theoretical basis for the targeted treatment of EGCG.

The Potential Role of Epigallocatechin-3-Gallate (EGCG) in Breast Cancer Treatment

Breast cancer is one of the most diagnosed cancers worldwide, with an incidence of 47.8%. Its treatment includes surgery, radiotherapy, chemotherapy, and antibodies giving a mortality of 13.6%. Breast tumor development is driven by a variety of signaling pathways with high heterogeneity of surface receptors, which makes treatment difficult. Epigallocatechin-3-gallate (EGCG) is a natural polyphenol isolated as the main component in green tea; it has shown multiple beneficial effects in breast cancer, controlling proliferation, invasion, apoptosis, inflammation, and demethylation of DNA. These properties were proved in vitro and in vivo together with synergistic effects in combination with traditional chemotherapy, increasing the effectiveness of the treatment. This review focuses on the effects of EGCG on the functional capabilities acquired by breast tumor cells during its multistep development, the molecular and signal pathways involved, the synergistic effects in combination with current drugs, and how nanomaterials can improve its bioavailability on breast cancer treatment.

The potential chemo-preventive roles of Malus domestica against the risk of colorectal cancer: A suggestive insight into clinical application

Biologically active compounds in fruit-derived ingredients, particularly phytochemicals, have significant potential to modulate and mitigate many pathological processes in the development of disease conditions, including cancer. Colorectal cancer (CRC) remains a major public health issue. Nonetheless, prevention is an important step in lowering the rate of mortality from this cancer. Currently, the link between apple consumption and improved health is becoming remarkably evident and is reported to be beneficial for human health. Phytochemicals, such as flavonoids and other polyphenol compounds extensively available in apple fruits, have well-known positive effects on health outcomes and the potential to combat and prevent the development of CRC, including antioxidant, anti-proliferative, and anti-carcinogenic effects. This review describes the bioactive compounds derived from apple fruits, particularly the polyphenols and flavonoids, their proposed mechanisms responsible for their bioactive properties and health-promoting attributes that could provide potential chemo-preventive effects against the risk of CRC development. The conclusion of the review provides insights into the potential effects of apple-derived bioactive compounds and proposes the need for more clinical studies in large trials for future strategies regarding the valuable effects of apple phytochemicals, which might be therapeutic candidates in the campaign against CRC.

Gut/Oral Bacteria Variability May Explain the High Efficacy of Green Tea in Rodent Tumor Inhibition and Its Absence in Humans

Consumption of green tea (GT) and GT polyphenols has prevented a range of cancers in rodents but has had mixed results in humans. Human subjects who drank GT for weeks showed changes in oral microbiome. However, GT-induced changes in RNA in oral epithelium were subject-specific, suggesting GT-induced changes of the oral epithelium occurred but differed across individuals. In contrast, studies in rodents consuming GT polyphenols revealed obvious changes in epithelial gene expression. GT polyphenols are poorly absorbed by digestive tract epithelium. Their metabolism by gut/oral microbial enzymes occurs and can alter absorption and function of these molecules and thus their bioactivity. This might explain the overall lack of consistency in oral epithelium RNA expression changes seen in human subjects who consumed GT. Each human has different gut/oral microbiomes, so they may have different levels of polyphenol-metabolizing bacteria. We speculate the similar gut/oral microbiomes in, for example, mice housed together are responsible for the minimal variance observed in tissue GT responses within a study. The consistency of the tissue response to GT within a rodent study eases the selection of a dose level that affects tumor rates. This leads to the theory that determination of optimal GT doses in a human requires knowledge about the gut/oral microbiome in that human.

The Intrinsic Virtues of EGCG, an Extremely Good Cell Guardian, on Prevention and Treatment of Diabesity Complications

The pandemic proportion of diabesity—a combination of obesity and diabetes—sets a worldwide health issue. Experimental and clinical studies have progressively reinforced the pioneering epidemiological observation of an inverse relationship between consumption of polyphenol-rich nutraceutical agents and mortality from cardiovascular and metabolic diseases. With chemical identification of epigallocatechin-3-gallate (EGCG) as the most abundant catechin of green tea, a number of cellular and molecular mechanisms underlying the activities of this unique catechin have been proposed. Favorable effects of EGCG have been initially attributed to its scavenging effects on free radicals, inhibition of ROS-generating mechanisms and upregulation of antioxidant enzymes. Biologic actions of EGCG are concentration-dependent and under certain conditions EGCG may exert pro-oxidant activities, including generation of free radicals. The discovery of 67-kDa laminin as potential EGCG membrane target has broaden the likelihood that EGCG may function not only because of its highly reactive nature, but also via receptor-mediated activation of multiple signaling pathways involved in cell proliferation, angiogenesis and apoptosis. Finally, by acting as epigenetic modulator of DNA methylation and chromatin remodeling, EGCG may alter gene expression and modify miRNA activities. Despite unceasing research providing detailed insights, ECGC composite activities are still not completely understood. This review summarizes the most recent evidence on molecular mechanisms by which EGCG may activate signal transduction pathways, regulate transcription factors or promote epigenetic changes that may contribute to prevent pathologic processes involved in diabesity and its cardiovascular complications.

In Vitro Biological Properties of Solanum sessiliflorum (Dunal), an Amazonian Fruit

Solanum sessiliflorum is an Amazonian fruit (cubiu) that has been domesticated since pre-Colombian era. It is also used in folk medicine to treat some clinical conditions. This investigation chemically characterized and analyzed the in vitro antioxidant and antitumoral effect of a cubiu pulp/seed hydroalcoholic extract. Cubiu extract was chemically characterized by high-performance liquid chromatography with diode array detector (HPLC-DAD), its antioxidant capacity measured by 2.2-diphenyl-1-picrylhydrazyl (DPPH) assay, and the following complementary in vitro protocols were performed: (1) cytoprotective effect of cubiu on human peripheral blood mononuclear cells (PBMCs) exposed to H₂O₂, a genotoxic and procarcinogen molecule; (2) effect of cubiu on low density lipoproteins oxidation; and (3) cytotoxic and antiproliferative effect on breast (MCF-7) and colorectal (HT-29) cancer cell lines. Biochemical and flow cytometry analyses were conducted in these protocols. Cubiu extract presented high concentrations of caffeic and gallic acids, beta-carotene, catechin, quercetin, and rutin, and its antioxidant capacity was confirmed. Cubiu attenuated H₂O₂ cytotoxicity on PBMCs, presented lowering effect on LDL oxidation, and induced mortality and proliferative inhibition of colorectal cancer cells. In cancer cells, cubiu extract at 10 μg/mL showed similar effects to 5-fluorouracil chemo drug reducing its viability and frequency of S-phase, indicating that cells are undergoing mitosis. In summary, despite the limitations of in vitro protocols, our results suggest that cubiu has several biological properties that affect human health.

SS, Kumar K. R, Narayan Sinha S. Method development and validation for rapid identification of epigallocatechin gallate using ultra-high performance liquid chromatography

Although Epigallocatechin gallate (EGCG) is the most available and beneficial catechin found in tea, its auto-oxidation property may lead to toxicity when consumed in large quantities. Thus, there is a need to quantify the EGCG, which enables to study the pharmacological characteristics of the compound. The study aimed to develop and validate a rapid and accurate analytical method for quantitative determination of EGCG. Standard EGCG was used to conduct trials for the optimization of the analytical method using Ultra-High Performance Liquid Chromatography (UHPLC). Tests for validation (specificity, linearity, accuracy, system suitability, method precision, robustness, and ruggedness) were performed. The preliminary trials yielded an analytical method with good peak shape and acceptable system suitability which was further validated. The method was shown to be specific, with a linear correlation coefficient of > 0.9996 and accurate with acceptable recovery rate (99.1% to 100.4%). Acceptable system suitability and method precision were confirmed with a relative standard deviation (less than 2%). Further, robustness and ruggedness experiments also demonstrated the suitability of the present analytical method. The method developed for determination of EGCG was validated as per the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines and thus can be used in routine compliance tests in the laboratory for further studying/characterizing the properties of EGCG.

Alchemilla vulgaris agg. (Lady's mantle) from central Balkan: antioxidant, anticancer and enzyme inhibition properties

The current study was designed to evaluate the phytochemical profile and biological properties (antioxidant, enzyme inhibitory and cytotoxic activity) of methanolic, ethanolic, ethyl-acetate and water extracts of Alchemilla vulgaris from Southeast Serbia (central Balkan) which was traditionally used to alleviate and treat many diseases. Bioactive compounds were characterized by LC-MS/MS technique and biological properties were evaluated using antioxidant, enzyme inhibitory and cytotoxic assays. Twenty-six phenolic compounds were quantified in methanolic, ethanolic, ethyl acetate and water extracts, whereas the highest yields were found in ethyl-acetate (EA) extract (gallic acid, caffeic acid, catchin, quercetin). This extract has also shown the greatest antioxidant, anticancer and inhibitory enzyme activities which were demonstrated for the first time in this study. The obtained results indicated that Alchemilla vulgaris from South Serbia possesses high potential for pharmaceutical applications.

Coffee and tea consumption during pregnancy and risk of childhood acute myeloid leukemia: A Childhood Leukemia International Consortium (CLIC) study

BACKGROUND

Dietary habits during pregnancy have been inconsistently linked to childhood acute myeloid leukemia (AML), given the putative intrauterine onset of the disease as a result of triggering events during the critical period of fetal hematopoiesis. We investigated the potential association of maternal coffee and tea consumption during pregnancy with childhood AML risk, pooling primary data from eight case-control studies participating in the Childhood Leukemia International Consortium.

METHODS

Information on coffee and/or tea consumption was available for 444 cases and 1255 age- and sex-matched controls, on coffee consumption for 318 cases and 971 controls and on tea consumption for 388 cases and 932 controls. Categories for cups of daily coffee/tea consumption were created in order to explore potential dose-response associations. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression.

RESULTS

Associations were found neither in the analysis on coffee or tea nor in the analysis on coffee only consumption (any versus no). A positive association with increasing coffee intake was observed (>1 cup per day; OR: 1.40, 95% CI: 1.03-1.92, increment of one cup per day; OR: 1.18, 95% CI: 1.01-1.39). No associations were observed with tea consumption. Interaction analyses showed non-significant associations between coffee/tea and smoking. Hyperdiploidy was inversely associated with tea consumption, with other cytogenetic markers having no association with coffee/tea.

CONCLUSION

Given the widespread consumption of caffeinated beverages among pregnant women, our finding is of important public health relevance, suggesting adverse effects of maternal coffee consumption during pregnancy in the offspring.

Melatonin and (-)-Epigallocatechin-3-Gallate: Partners in Fighting Cancer

We have demonstrated previously that melatonin attenuates hepatotoxicity triggered by high doses of (−)-epigallocatechin-3-gallate (EGCG) in mice. The current work investigated the influence of melatonin on the oncostatic activity of EGCG in two cancer cell lines, wherein melatonin induced an opposite response of p21. In human tongue cancer TCA8113 cells, melatonin-induced p21 and EGCG-mediated formation of quinoproteins were positively associated with the oncostatic effects of melatonin and EGCG. Melatonin-stimulated an increase in p21 which was correlated with a pronounced nuclear translocation of thioredoxin 1 and thioredoxin reductase 1, both of which are known to induce p21 via promoting p53 trans-activation. Melatonin did not influence the EGCG-mediated increase of quinoprotein formation nor did EGCG impair melatonin-induced p21 up-regulation. Co-treatment with both agents enhanced the cell-killing effect as well as the inhibitory activities against cell migration and colony formation. It is known that p21 also plays a powerful anti-apoptotic role in some cancer cells and confers these cells with a survival advantage, making it a target for therapeutic suppression. In human hepatocellular carcinoma HepG2 cells, melatonin suppressed p21 along with the induction of pro-survival proteins, PI3K and COX-2. However, EGCG prevented against melatonin-induced PI3K and COX-2, and melatonin probably sensitized HepG2 cells to EGCG cytotoxicity via down-regulating p21, Moreover, COX-2 and HO-1 were significantly reduced only by the co-treatment, and melatonin aided EGCG to achieve an increased inhibition on Bcl2 and NFκB. These events occurring in the co-treatment collectively resulted in an enhanced cytotoxicity. In addition, the co-treatment also enhanced the inhibitory activities against cell migration and colony formation. Overall, the results gathered from these two cancer cell lines with a divergent p21 response to melatonin show that the various oncostatic activities of melatonin and EGCG together are more robust than each agent alone, suggesting that they may be useful partners in fighting cancer.

Green tea intake and colorectal cancer risk in Japan: the Takayama study

BACKGROUND

Reportedly, green tea has a preventive effect against colorectal cancer in animal models. Nevertheless, results from epidemiological studies of the association between green tea consumption and colorectal cancer have been inconsistent. We aimed to evaluate colorectal cancer risk in relation to green tea consumption in a population-based prospective cohort study.

METHODS

Subjects were 13 957 men and 16 374 women aged ≥35 years in September 1992. The participants' green tea consumption was elicited by administering a food frequency questionnaire. The colorectal cancer incidence was confirmed through regional population-based cancer registries and histological identification from colonoscopy in two main hospitals in the study area. Colorectal cancer was defined as the sum of code C18 (colon cancer) and codes C19 and C20 (rectal cancer) according to ICD-10.

RESULTS

Up to March 2008, 429 men and 343 women were diagnosed with colorectal cancer. No significant association was found between green tea consumption and colorectal cancer in men and women, respectively. However, for men, compared with the group of 'none or less than once per day' of green tea consumption, the multiple-adjusted relative risks (95% CIs) for colon cancer were 1.32 (0.90, 1.94), 0.76 (0.57, 1.02), and 0.78 (0.49, 1.22), respectively, in the group of 'once per day,' '2-3 times per day', and 'four times per day or more' (trend P = 0.045).

CONCLUSIONS

This study observed no overall significant associations between green tea consumption and colorectal cancer risk, except that there was a weak trend for greater consumption of green tea with decreased risk of male colon cancer.

Differences in chemical composition predictive of in vitro biological activity among commercially important cultivars of genus Camellia

Leaves of plants from the genus Camellia (CAM) are used to make tea; however, there are limited data that compares chemical composition and biological activity of CAM cultivars used to make six tea types. Fourteen CAM cultivars were analyzed by HPLC and UPLC-Q-TOF-MS/MS and biological activity was assessed in a cell growth assay. Tea bioactives and cell growth inhibition varied 2-4 fold. EGCG was the dominant catechin that predicted the magnitude of growth inhibition. However, pure EGCG did not fully account for inhibitory activity suggesting that it may serve as a chemical marker for bioefficacy. As an unbiased characterization of differences in chemical composition among CAM, individual metabolomes were determined and used to generate principle components (PC). PC's from the metabolome were complementary to those from targeted analyses of tea bioactives and were predictive of growth inhibition. This study provides a frame work for identifying CAM cultivars with beneficial traits.

High Consumption of Green Tea Suppresses Urinary Tract Recurrence of Urothelial Cancer via Down-regulation of Human Antigen-R Expression in Never Smokers

BACKGROUND/AIM

Smoking is a risk factor for carcinogenesis and progression of urothelial cancer (UC). Green tea polyphenol inhibits these malignant behaviors and suppresses human antigen R (HuR) expression, which is associated with malignant aggressiveness. This study aimed to clarify the anti-cancer effects of green tea based on the smoking status of UC patients.

PATIENTS AND METHODS

Three hundred and sixty (260 with bladder cancer, BC and 100 with upper tract UC) patients were divided into three groups based on consumption of green tea: low (<1 cup/day, n=119), middle (1-4 cup/day, n=160), and high (>5 cup/day, n=81). HuR immunoreactivity was evaluated immunohistochemically in formalin-fixed specimens.

RESULTS

In never smokers, multivariate analysis showed that the frequency of green tea consumption was a significant predictor (middle: hazard ratio, HR, 0.36, p=0.002; high: HR, 0.20, p=0.003) of urinary tract recurrence. A high consumption of green tea was associated with low rates of urinary tract recurrence and up-grading in UC patients. In BC, high consumption was associated with a lower risk of up-grading (p=0.011) and up-staging (p=0.041) in recurrent cancer. HuR expression in the high-consumption group was lower (p=0.019) than that in other groups. These significant findings were not detected in ever smokers.

CONCLUSION

High consumption of green tea suppressed urinary tract recurrence and the risks of up-grading and up-staging by recurrence in never smokers. Our results suggested that HuR expression played important roles in such mechanisms.

Protective and Restorative Effects of Nutrients and Phytochemicals

Intoroduction:

Dietary intake fundamentally provides reintegration of energy and essential nutrients to human organisms. However, its qualitative and quantitative composition strongly affects individual’s health, possibly being either a preventive or a risk factor. It was shown that nutritional status resulting from long-term exposition to specific diet formulations can outstandingly reduce incidences of most common and most important diseases of the developed world, such as cardiovascular and neoplastic diseases. Diet formulations result from different food combinations which bring specific nutrient molecules. Numerous molecules, mostly but not exclusively from vegetal foods, have been characterized among nutritional components as being particularly responsible for diet capabilities to exert risk reduction. These “bioactive nutrients” are able to produce effects which go beyond basic reintegration tasks, i.e. energetic and/or structural, but are specifically pharmacologically active within pathophysiological pathways related to many diseases, being able to selectively affect processes such as cell proliferation, apoptosis, inflammation, differentiation, angiogenesis, DNA repair and carcinogens activation.

Conclusion:

The present review was aimed to know the molecular mechanisms and pathways of activity of bioactive molecules; which will firstly allow search for optimal food composition and intake, and then use them as possible therapeutical targets and/or diagnostics. Also, the present review discussed the therapeutic effect of both nutrients and phytochemicals.

Effects of green tea on miRNA and microbiome of oral epithelium

Consumption of green tea (GT) extracts or purified catechins has shown the ability to prevent oral and other cancers and inhibit cancer progression in rodent models, but the evidence for this in humans is mixed. Working with humans, we sought to understand the source of variable responses to GT by examining its effects on oral epithelium. Lingual epithelial RNA and lingual and gingival microbiota were measured before and after 4 weeks of exposure in tobacco smokers, whom are at high risk of oral cancer. GT consumption had on average inconsistent effects on miRNA expression in the oral epithelium. Only analysis that examined paired miRNAs, showing changed and coordinated expression with GT exposure, provided evidence for a GT effect on miRNAs, identifying miRNAs co-expressed with two hubs, miR-181a-5p and 301a-3p. An examination of the microbiome on cancer prone lingual mucosa, in contrast, showed clear shifts in the relative abundance of Streptococcus and Staphylococcus, and other genera after GT exposure. These data support the idea that tea consumption can consistently change oral bacteria in humans, which may affect carcinogenesis, but argue that GT effects on oral epithelial miRNA expression in humans vary between individuals.

(-)-Epigallocatechin-3-gallate ameliorates memory impairment and rescues the abnormal synaptic protein levels in the frontal cortex and hippocampus in a mouse model of Alzheimer's disease

(-)-Epigallocatechin-3-gallate (EGCG) is the most abundant polyphenolic extract in green tea and it has attracted increasing attention for its multiple bioactive effects. However, the mechanisms by which EGCG exerts its neuroprotective actions in Alzheimer's disease (AD) are presently lacking. In the present study, a sporadic AD transgenic mouse model known as senescence-accelerated mouse prone 8 (SAMP8) was used to investigate whether oral administration of EGCG could improve recognition and memory function through reduction of amyloid β (Aβ) and tau hyperphosphorylation. We also investigated the effects of chronic EGCG treatment on the synaptic dysfunction in the frontal cortex (FC) and the hippocampus (Hip) of AD mice. The results showed that long-term oral consumption of EGCG at a relatively high dose (15 mg/kg) improved memory function in SAMP8 mice in the Y-maze and Morris water maze. The levels of Aβ1-42 and BACE-1 in FC and Hip were significantly reduced by EGCG treatment. EGCG treatment also prevented the hyperphosphorylation of tau and reversed the decreased synaptic protein marker synaptophysin and postsynaptic density protein 95 in FC and Hip of SAMP8 mice. The present study suggests that long-term oral consumption of EGCG ameliorates impairments in spatial learning and memory and rescues the reduction in synaptic proteins observed in an AD mouse model. Thus, EGCG may represent a novel candidate agent for the treatment of neurodegenerative diseases.

Identification of Intestinal UDP-Glucuronosyltransferase Inhibitors in Green Tea (Camellia sinensis) Using a Biochemometric Approach: Application to Raloxifene as a Test Drug via In Vitro to In Vivo Extrapolation

Green tea (Camellia sinensis) is a popular beverage worldwide, raising concern for adverse interactions when co-consumed with conventional drugs. Like many botanical natural products, green tea contains numerous polyphenolic constituents that undergo extensive glucuronidation. As such, the UDP-glucuronosyltransferases (UGTs), particularly intestinal UGTs, represent potential first-pass targets for green tea-drug interactions. Candidate intestinal UGT inhibitors were identified using a biochemometrics approach, which combines bioassay and chemometric data. Extracts and fractions prepared from four widely consumed teas were screened (20-180 μg/ml) as inhibitors of UGT activity (4-methylumbelliferone glucuronidation) in human intestinal microsomes; all demonstrated concentration-dependent inhibition. A biochemometrics-identified fraction rich in UGT inhibitors from a representative tea was purified further and subjected to second-stage biochemometric analysis. Five catechins were identified as major constituents in the bioactive subfractions and prioritized for further evaluation. Of these catechins, (-)-epicatechin gallate and (-)-epigallocatechin gallate showed concentration-dependent inhibition, with IC₅₀ values (105 and 59 μM, respectively) near or below concentrations measured in a cup (240 ml) of tea (66 and 240 μM, respectively). Using the clinical intestinal UGT substrate raloxifene, the K_i values were ∼1.0 and 2.0 μM, respectively. Using estimated intestinal lumen and enterocyte inhibitor concentrations, a mechanistic static model predicted green tea to increase the raloxifene plasma area under the curve up to 6.1- and 1.3-fold, respectively. Application of this novel approach, which combines biochemometrics with in vitro-in vivo extrapolation, to other natural product-drug combinations will refine these procedures, informing the need for further evaluation via dynamic modeling and clinical testing.

Dietary Copper Reduces the Hepatotoxicity of (-)-Epigallocatechin-3-Gallate in Mice

We developed Cu-deficient, -sufficient and -super nutrition mice models by feeding them with diet containing 1.68, 11.72 or 51.69 mg of Cu/kg for 28 days, respectively. Then, the mice were treated to (−)-epigallocatechin-3-gallate (EGCG, 750 mg/kg BW) by oral in order to assess the acute toxicity of the drug. Following EGCG treatment, the survival rates were 12.5%, 50% and 100% in the Cu-deficient, -sufficient and Cu-super nutrition groups of mice, respectively. Cu level and ceruloplasmin activity in serum were significantly increased with the increase of dietary Cu. However, the Cu supplementation did not produce any obvious impact on serum superoxide dismutase activity. Furthermore, ceruloplasmin, in vitro, significantly promotes EGCG oxidation accompanied with increasing oxidation products and decreasing levels of reactive oxygen species. These results, therefore, suggest that Cu can relieve EGCG hepatotoxicity, possibly by up-regulating ceruloplasmin activity, which can be used to promote EGCG applications.

Epigallocatechin-3-O-gallate alleviates the malignant phenotype in A-431 epidermoid and SK-BR-3 breast cancer cell lines

In this study, we evaluated the effects of epigallocatechin-3-O-gallate (EGCG) in two cancer cell lines, A-431 overexpressing ErbB1 and SK-BR-3, overexpressing ErbB2. EGCG treatment showed dose-dependent collapse of mitochondrial membrane potential (Δψ_m), increase in reactive oxygen species (ROS) production, changes in nuclear morphology and reduced viability. Flow cytometry data indicated that EGCG partially decreases the phosphorylation of several proteins involved in cell proliferation and survival: pErbB1(Y1173, Y1068), pAkt(S473) and pERK(Y204). EGCG affected the clonogenic growth in both cell lines with an EC₅₀ of 2.5 and 5.4 µM for A-431 and SK-BR-3, respectively. Wound scratch assay demonstrated that EGCG inhibited the healing in dose-dependent manner and the effect was correlated with partial reduction in phosphorylation of pFAK(S910). Our data suggest that EGCG administration might reduce the unfavourable traits, particularly associated with ErbB1/EGFR overexpression.

Green tea (Camellia sinensis) and l-theanine: Medicinal values and beneficial applications in humans-A comprehensive review

Green tea (Camellia sinensis) is a famous herb, and its extract has been extensively used in traditional Chinese medicinal system. In this context, several studies have revealed its health benefits and medicinal potentialities for several ailments. With ever increasing scientific knowledge, search for safer, potential and novel type of health-related supplements quest, scientists are re-directing their research interests to explore natural resources i.e. medicinal herbs/plant derived compounds. Green tea consumption has gained a special attention and popularity in the modern era of changing lifestyle. The present review is aimed to extend the current knowledge by highlighting the importance and beneficial applications of green tea in humans for safeguarding various health issues. Herein, we have extensively reviewed, analyzed, and compiled salient information on green tea from the authentic published literature available in PubMed and other scientific databases. Scientific literature evidenced that owing to the bioactive constituents including caffeine, l-theanine, polyphenols/flavonoids and other potent molecules, green tea has many pharmacological and physiological functions. It possesses multi-beneficial applications in treating various disorders of humans. This review also provides in-depth insights on the medicinal values of green tea which will be useful for researchers, medical professionals, veterinarians, nutritionists, pharmacists and pharmaceutical industry. Future research emphasis and promotional avenues are needed to explore its potential therapeutic applications for designing appropriate pharmaceuticals, complementary medicines, and effective drugs as well as popularize and propagate its multidimensional health benefits.

Bioactive compounds as an alternative for drug co-therapy: Overcoming challenges in cardiovascular disease prevention

Different pharmacological interventions have been applied with success to reduce the progression of atherosclerosis. However, many patients are not good responders or must interrupt treatment due to adverse effects. Bioactive compounds such as omega-3 fatty acids (n-3 FA), plant sterol esters (PSE) and phenolic compounds (PHC) are natural molecules with great potential to reduce the atherosclerosis burden by reducing inflammation, LDL cholesterol (LDL-C) and oxidative stress, respectively. Although their physiological effects on biomarkers are much lower than those expected by drugs used for the same purpose, bioactive compounds can easily be incorporated into the daily diet and present no adverse effects. However, little is known about the combination of n-3 FA, PSE, PHC, and drugs in atherosclerosis progression. This review article summarizes potential effects of co-therapies involving n-3 FA, PSE, and PHC combined with major hypolipidemic drugs on atherosclerosis biomarkers and clinical outcomes. Evidence of additive and/or complementary effects regarding drugs action reveals possible roles for bioactive compounds in disease management. Pharmaceutical companies, physicians, and food scientists should be prepared to better understand this type of interaction and its consequences in terms of efficacy and life quality.

Identification of Epigallocatechin-3- Gallate as an Inhibitor of Phosphoglycerate Mutase 1

Targeting metabolic enzymes is believed to provide new therapeutic opportunities for cancer therapy. Phosphoglycerate mutase 1 (PGAM1) is a glycolytic enzyme that importantly coordinates glycolysis, pentose phosphate pathway (PPP) flux and serine biosynthesis in cancer cells and hence gains increasing interest of inhibitor discovery. Only few PGAM1 inhibitors have been reported and the molecular potency remains very limited. In an effort to discover new PGAM1 inhibitors, we carried out a biochemical assay-based screen that was focused on natural products derived small molecule compounds. (-)-Epigallocatechin-3-gallate (EGCG), the major natural catechins of green tea extract, was identified as a PGAM1 inhibitor that was tremendously more potent than known PGAM1 inhibitors. Further studies combining molecular docking and site-specific mutagenesis revealed that EGCG inhibited PGAM1 enzymatic activity in a manner independent of substrate competition. EGCG modulated the intracellular level of 2-phosphoglycerate, impaired glycolysis and PPP and inhibited proliferation of cancer cells. This study suggested EGCG as a chemical scaffold for the discovery of potent PGAM1 inhibitors and gained mechanistic insights to understand the previously appreciated anticancer properties of EGCG.

Potential therapeutic targets of epithelial-mesenchymal transition in melanoma

Melanoma is a cutaneous neoplastic growth of melanocytes with great potential to invade and metastasize, especially when not treated early and effectively. Epithelial-mesenchymal transition (EMT) is the process by which melanocytes lose their epithelial characteristics and acquire mesenchymal phenotypes. Mesenchymal protein expression increases the motility, invasiveness, and metastatic potential of melanoma. Many pathways play a role in promotion of mesenchymal protein expression including RAS/RAF/MEK/ERK, PI3K/AKT/mTOR, Wnt/β-catenin, and several others. Downstream effectors of these pathways induce expression of EMT transcription factors including Snail, Slug, Twist, and Zeb that promote repression of epithelial and induction of mesenchymal character. Emerging research has demonstrated that a variety of small molecule inhibitors as well as phytochemicals can influence the progression of EMT and may even reverse the process, inducing re-expression of epithelial markers. Phytochemicals are of particular interest as supplementary treatment options because of their relatively low toxicities and anti-EMT properties. Modulation of EMT signaling pathways using synthetic small molecules and phytochemicals is a potential therapeutic strategy for reducing the aggressive progression of metastatic melanoma. In this review, we discuss the emerging pathways and transcription factor targets that regulate EMT and evaluate potential synthetic small molecules and naturally occurring compounds that may reduce metastatic melanoma progression.

Anti-Cancer Effects of Green Tea by Either Anti- or Pro- Oxidative Mechanisms

Tea derived from the leaves and buds of Camellia sinensis (Theaceae) is consumed worldwide. Green tea contains various components with specific health-promoting effects, and is believed to exert protective effects against diseases including cancer, diabetes and hepatitis, as well as obesity. Of the various tea components, the polyphenol catechins have been the subject of extensive investigation and among the catechins, (-)-epigallocatechin gallate has the strongest bioactivity in most cases. Our research group has postulated that hepatocyte nuclear factor-4α, sterol regulatory element-binding proteins, and tumor necrosis factor-α are targets of green tea constituents including (-)-epigallocatechin gallate for their anti-diabetes, anti-obesity, and anti-hepatitis effects, respectively. Published papers were reviewed to determine whether the observed changes in these factors can be correlated with anti-cancer effects of green tea. Two major action mechanisms of (-)-epigallocatechin gallate have been proposed; one associated with its anti-oxidative properties and the other with its pro-oxidative activity. When reactive oxygen species are assumed to be involved, our findings that (-)-epigallocatechin gallate down- regulated hepatocyte nuclear factor-4α, sterol regulatory element-binding proteins, and tumor necrosis factor-α may explain the anti-cancer effect of green tea as well. However, further studies are required to elucidate which determinant directs (-)-epigallocatechin gallate action as an anti-oxidant or a pro-oxidant for favorable activity.

Tea Consumption and Risk of Bladder Cancer: A Dose-Response Meta-Analysis

Background and Objective: Controversial results of the association between tea (black tea, green tea, mate, and oolong tea) consumption and risk of bladder cancer were reported among epidemiological studies. Thus, we performed a meta-analysis of observational studies to investigate the association. Methods: We searched the PubMed and Embase for studies of tea consumption and bladder cancer that were published in any language up to March, 2016. Cohort or case-control studies were included in the meta-analysis. All statistical analyses were performed in Stata 12.0 software. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationship between tea consumption and risk of bladder cancer. Results: Totally, 25 case-control studies (15 643 cases and 30 795 controls) and seven prospective cohort studies (1807 cases and 443 076 participants) were included. The meta-analysis showed that tea consumption was not significantly associated with bladder cancer risk (OR = 0.96, 95% CI 0.86-1.06) (in a comparison of highest vs. lowest category). No non-linearity association was observed between tea consumption and bladder cancer risk (P = 0.51 for non-linearity). Specific analysis for black tea, green tea, and mate yielded similar results. The dose-response analysis showed the summary OR for an increment of 1 cup/day of tea consumption was 1.01 (95% CI 0.97-1.05). Conclusion: Results based on current meta-analysis indicated that no significant association was observed between tea consumption and risk of bladder cancer.

Cancer Preventive Activities of Tea Catechins

Catechins are widely occurring in our diet and beverages. The cancer-preventive activities of catechins have been extensively studied. Of these, (-)-epigallocatechin-3-gallate (EGCG), the principal catechin in green tea, has received the most attention. The inhibitory activities of tea catechins against carcinogenesis and cancer cell growth have been demonstrated in a large number of laboratory studies. Many mechanisms for modulating cancer signaling and metabolic pathways have been proposed based on numerous studies in cell lines with EGCG, the most active tea catechin. Nevertheless, it is not known whether many of these mechanisms indeed contribute to the anti-cancer activities in animals and in humans. Human studies have provided some results for the cancer preventive activities of tea catechins; however, the activities are not strong. This article reviews the cancer preventive activities and mechanisms of action of tea catechins involving their redox activities, biochemical properties and binding to key enzymes or signal transduction proteins. These mechanisms lead to suppression of cell proliferation, increased apoptosis and inhibition of angiogenesis. The relevance of the proposed mechanisms for cancer prevention are assessed in the light of the situation in vivo. The potential and possible problems in the application of tea and tea-derived products for cancer prevention are discussed.

The consumption of coffee and black tea and the risk of lung cancer

PURPOSE

Coffee and black tea are among the most consumed beverages worldwide. Although their potential role in lung cancer occurrence has been investigated in several studies, results have been inconclusive. We investigated the associations between intake of coffee and black tea with lung cancer in a population-based case-control study in Montreal, Canada.

METHODS

These analyses included 1130 cases and 1483 controls. Adjusted odds ratios (ORs) were estimated between four metrics of coffee and black tea consumption (frequency, average daily amount, duration, and cumulative amount) and lung cancer, using unconditional logistic regression.

RESULTS

The adjusted ORs (95% confidence intervals) for lung cancer comparing daily to never consumers were 0.73 (0.49-1.10) for coffee and 1.05 (0.85-1.31) for black tea. Analyses of other metrics did not reveal any clear patterns of increasing or decreasing risk with increasing amounts or duration of consumption. There was no strong evidence of OR modification by sex or smoking level. The OR estimates did not materially differ by histological subtype for either of the beverages.

CONCLUSION

Our results do not provide strong support for associations between consumption of coffee and black tea and lung cancer.

Green tea reduces body fat via upregulation of neprilysin

BACKGROUND/OBJECTIVE

Consumption of green tea has become increasingly popular, particularly because of claimed reduction in body weight. We recently reported that animals with pharmacological inhibition (by candoxatril) or genetic absence of the endopeptidase neprilysin (NEP) develop an obese phenotype. We now investigated the effect of green tea extract (in drinking water) on body weight and body composition and the mediating role of NEP.

SUBJECTS/METHODS

To elucidate the role of NEP in mediating the beneficial effects of green tea extract, 'Berlin fat mice' or NEP-deficient mice and their age- and gender-matched wild-type controls received the extract in two different doses (300 or 600 mg kg^-1 body weight per day) in the drinking water.

RESULTS

In 'Berlin fat mice', 51 days of green tea treatment did not only prevent fat accumulation (control: day 0: 30.5% fat, day 51: 33.1%; NS) but also reduced significant body fat (green tea: day 0: 27.8%, day 51: 20.9%, P<0.01) and body weight below the initial levels. Green tea reduced food intake. This was paralleled by a selective increase in peripheral (in kidney 17%, in intestine 92%), but not central NEP expression and activity, leading to downregulation of orexigens (like galanin and neuropeptide Y (NPY)) known to be physiological substrates of NEP. Consequently, in NEP-knockout mice, green tea extract failed to reduce body fat/weight.

CONCLUSIONS

Our data generate experimental proof for the assumed effects of green tea on body weight and the key role for NEP in such process, and thus open a new avenue for the treatment of obesity.

Inhibition of green tea polyphenol EGCG((-)-epigallocatechin-3-gallate) on the proliferation of gastric cancer cells by suppressing canonical wnt/β-catenin signalling pathway

(-)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, could affect carcinogenesis and development of many cancers. However, the effects and underlying mechanisms of EGCG on gastric cancer remain unclear. We found that EGCG significantly inhibited proliferation and increased apoptosis of SGC-7901 cells in vitro. The decreased expressions of p-β-catenin(Ser552), p-GSK3β(S9) and β-catenin target genes were detected in SGC-7901 cells after treated by EGCG. XAV939 and β-catenin plasmid were further used to demonstrate the inhibition of EGCG on canonical Wnt/β-catenin signalling. Moreover, EGCG significantly inhibited gastric tumour growth in vivo by inhibiting Wnt/β-catenin signalling. Taken together, our findings establish that EGCG suppressed gastric cancer cell proliferation and demonstrate that this inhibitory effect is related to canonical Wnt/β-catenin signalling. This study raises a new insight into gastric cancer prevention and therapy, and provides evidence that green tea could be used as a nutraceutical beverage.

A review on the structure-function relationship aspect of polysaccharides from tea materials

Tea (Camellia sinensis) has a long history of medicinal use in the world. The chemical components of tea mainly consist of polyphenols (TPP), proteins, polysaccharides (TPS), chlorophyll, alkaloids, and so on. Great advances have been made in chemical and bioactive studies of catechins and TPP from tea in recent decades. However, the TPS from tea materials have received much less consideration than that of TPP. The number of relevant publications on the TPS from tea leaves and flowers has increased rapidly in recent years. This mini-review summarizes the structure-function relationship of TPS from tea leaves and flowers. The application of purified TPS from tea material as functional or nutritional foods was still little. It will help to develop the function foods with tea TPS and better understand the structure-bioactivity relationship of tea TPS.

Isolation of eugenyl β-primeveroside from Camellia sasanqua and its anticancer activity in PC3 prostate cancer cells

Most studies of tea trees have focused on their ornamental properties, there are fewer published studies on their medical values. The purpose of this study was to compare the chemical constituents and the biological potential of the water extract of leaves in eight species of Camellia including Camellia sinensis. Among eight Camellia species, Camellia sasanqua showed potent anticancer activities in prostate cancer PC3 cells. In addition to catechins, the major component, eugenyl β-primeveroside was detected in C. sasanqua. Eugenyl β-primeveroside blocked the progression of cell cycle at G1 phase by inducing p53 expression and further upregulating p21 expression. Moreover, eugenyl β-primeveroside induced apoptosis in PC3 prostate cancer cells. Our results suggest that C. sasanqua may have anticancer potential.

Inhibitory effect of (-)-epigallocatechin-3-gallate and bleomycin on human pancreatic cancer MiaPaca-2 cell growth

Background

Human pancreatic cancer is currently one of the deadliest cancers with high mortality rate. It has been previously shown that (−)-epigallocatechin-3-gallate (EGCG), the most abundant catechin found in green tea, has showed suppressive effects on human pancreatic cancer cells. Bleomycin, (BLM), an anti-cancer chemotherapeutic drug that induces DNA damage, has antitumor effects by induction of apoptosis in several cancer cell lines and also in pancreatic cancer cells. The present study investigated for the first time, the inhibitory effect of EGCG and BLM on pancreatic cancer cell growth.

Methods

Using the pancreatic cancer cell lines MIA PaCa-2 cells the efficacy and synergism of EGCG and BLM were evaluated by in vitro tests. Inhibition of cell proliferation was determined by MTT assay. Mitochondrial depolarization was performed with JC-1 probe. Viability and apoptosis were determined by Flow Cytometry with annexin V, propidium iodide staining and DNA fragmentation assay.

Results

Cell proliferation assay revealed significant additive inhibitory effects with combination of EGCG and BLM at 72 h in a dose dependent manner. The combination of EGCG and BLM induced cell cycle S-phase arrest and mitochondrial depolarization. Viability, apoptosis and DNA fragmentation assay indicated that the combination of EGCG and bleomycin potentiated apoptosis.

Conclusions

Our results indicate that EGCG and BLM have additive anti-proliferative effects in vitro by induction of apoptosis of MIA PaCa-2 cells. This combination could represent a new strategy with potential advantages for treatment of pancreatic cancer. To date, this is the first report published of the inhibitory effect of EGCG and BLM on human pancreatic cancer MIA Paca-2 cell growth.

EGCG regulates the cross-talk between JWA and topoisomerase IIα in non-small-cell lung cancer (NSCLC) cells

(-)-epigallocatechin-3-gallate (EGCG) is a well-known cancer chemopreventive agent. The potential mechanisms include regulation of multiple molecules. Carcinogenesis in lung cancer is related to the imbalance of tumor suppressor and oncogene. JWA is a structurally novel microtubule-binding protein and is a potential tumor suppressor. DNA topoisomerase IIα is a nuclear enzyme that governs DNA topology and is usually highly expressed in many types of cancer. It serves as a target of anticancer drugs. In the current study, the regulation of JWA and topoisomerase IIα by EGCG, and thereafter the mutual interaction between them was investigated. The results revealed that EGCG up-regulated JWA while decreased topoisomerase IIα expression in both human non-small cell lung cancer (NSCLC) cells and an NSCLC xenograft mice model. There was a negative correlation between JWA and topoisomerase IIα in NSCLC as well as in human NSCLC tissue specimens. Topoisomerase IIα overexpression reduced JWA at the translational level. Meanwhile, JWA-induced topoisomerase IIα degradation was regulated both in the transcriptional and post-translational level. Interestingly, JWA and topoisomerase IIα regulated each other in the cells arrested in G2/M. Furthermore, JWA and topoisomerase IIα synergistically affected NCI-H460 cells invasion. These results may serve a novel mechanism for cancer prevention.

Prospective study of breast cancer in relation to coffee, tea and caffeine in Sweden

Studies of coffee and tea consumption and caffeine intake as risk factors for breast cancer are inconclusive. We assessed coffee and tea consumption, caffeine intake, and possible confounding factors among 42,099 women from the Swedish Women's Lifestyle and Health study, the participants of which were aged 30-49 years at enrollment in 1991-1992. Complete follow-up for breast cancer incidence was performed through 2012 via linkage to national registries. Poisson regression models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs) for breast cancer. During follow-up 1,395 breast cancers were diagnosed. The RR was 0.97 (95% CI 0.94-0.99) for a 1-unit increase in cups of coffee/day, 1.14 (95% CI 1.05-1.24) for a 1-unit increase in cups of tea/day, and 0.97 (95% CI 0.95-1.00) for a 100 mg/day increase in caffeine intake. Although the RR for no consumption (RR = 0.86, 95% CI 0.69-1.08), a group with a relatively small number of women, was not statistically significant, women with higher consumption had a decreased breast cancer risk (3-4 cups/day: RR = 0.87, 95% CI 0.76-1.00; ≥5 cups/day: RR = 0.81, 95% CI 0.70-0.94) compared to women consuming 1-2 cups of coffee/day. Compared to no consumption, women consuming >1 cups tea/day showed an increased breast cancer risk (RR = 1.19, 95% CI 1.00-1.42). Similar patterns of estimates were observed for breast cancer risk overall, during pre- and postmenopausal years, and for ER+ or PR+ breast cancer, but not for ER- and PR- breast cancer. Our findings suggest that coffee consumption and caffeine intake is negatively associated with the risk of overall and ER+/PR- breast cancer, and tea consumption is positively associated with the risk of overall and ER+/PR+ breast cancer.

Randomized clinical trial of brewed green and black tea in men with prostate cancer prior to prostatectomy

BACKGROUND

Preclinical and epidemiologic studies suggest chemopreventive effects of green tea (GT) and black tea (BT) in prostate cancer. In the current study we determined the effect of GT and BT consumption on biomarkers related to prostate cancer development and progression.

METHODS

In this exploratory, open label, phase II trial 113 men diagnosed with prostate cancer were randomized to consume six cups daily of brewed GT, BT or water (control) prior to radical prostatectomy (RP). The primary endpoint was prostate tumor markers of cancer development and progression determined by tissue immunostaining of proliferation (Ki67), apoptosis (Bcl-2, Bax, Tunel), inflammation (nuclear and cytoplasmic nuclear factor kappa B [NFκB]) and oxidation (8-hydroxydeoxy-guanosine [8OHdG]). Secondary endpoints of urinary oxidation, tea polyphenol uptake in prostate tissue, and serum prostate specific antigen (PSA) were evaluated by high performance liquid chromatography and ELISA analysis.

RESULTS

Ninety three patients completed the intervention. There was no significant difference in markers of proliferation, apoptosis and oxidation in RP tissue comparing GT and BT to water control. Nuclear staining of NFκB was significantly decreased in RP tissue of men consuming GT (P = 0.013) but not BT (P = 0.931) compared to water control. Tea polyphenols were detected in prostate tissue from 32 of 34 men consuming GT but not in the other groups. Evidence of a systemic antioxidant effect was observed (reduced urinary 8OHdG) only with GT consumption (P = 0.03). GT, but not BT or water, also led to a small but statistically significant decrease in serum prostate-specific antigen (PSA) levels (P = 0.04).

CONCLUSION

Given the GT-induced changes in NFκB and systemic oxidation, and uptake of GT polyphenols in prostate tissue, future longer-term studies are warranted to further examine the role of GT for prostate cancer prevention and treatment, and possibly for other prostate conditions such as prostatitis.

Epigallocatechin gallate inhibits human tongue carcinoma cells via HK2‑mediated glycolysis

Epigallocatechin gallate (EGCG), one of the major catechins found in green tea, was suggested to play a role as a chemopreventive agent in various human cancer models. In this study, we reported that EGCG has a profound antitumor effect on human tongue carcinoma cells by directly regulating glycolysis. EGCG dose-dependently inhibited anchorage-independent growth and short-term EGCG exposure substantially decreased EGF-induced EGF receptor (EGFR), Akt and ERK1/2 activation, as well as the downregulation of hexokinase 2 (HK2). Furthermore, inhibition of EGCG‑mediated HK2 expression was involved in Akt, but not in ERK1/2 signaling pathway suppression. Overexpression of constitutively activated Akt1 rescued inhibition of EGCG‑induced glycolysis. Moreover, EGCG inhibited HK2 expression on mitochondrial outer membrane and induced apoptosis. In summary, the results suggested that EGCG or a related analogue, may have a role in the management of human tongue carcinoma.

Gene regulation mediated by microRNAs in response to green tea polyphenol EGCG in mouse lung cancer

BACKGROUND

Epigallocatechin-3-gallate (EGCG) has been demonstrated to inhibit cancer in experimental studies through its antioxidant activity and modulations on cellular functions by binding specific proteins. We demonstrated previously that EGCG upregulates the expression of microRNA (i.e. miR-210) by binding HIF-1α, resulting in reduced cell proliferation and anchorage-independent growth. However, the binding affinities of EGCG to HIF-1α and many other targets are higher than the EGCG plasma peak level in experimental animals administered with high dose of EGCG, raising a concern whether the microRNA regulation by HIF-1α is involved in the anti-cancer activity of EGCG in vivo.

RESULTS

We employed functional genomic approaches to elucidate the role of microRNA in the EGCG inhibition of tobacco carcinogen-induced lung tumors in A/J mice. By analysing the microRNA profiles, we found modest changes in the expression levels of 21 microRNAs. By correlating these 21 microRNAs with the mRNA expression profiles using the computation methods, we identified 26 potential targeted genes of the 21 microRNAs. Further exploration using pathway analysis revealed that the most impacted pathways of EGCG treatment are the regulatory networks associated to AKT, NF-κB, MAP kinases, and cell cycle, and the identified miRNA targets are involved in the networks of AKT, MAP kinases and cell cycle regulation

CONCLUSIONS

These results demonstrate that the miRNA-mediated regulation is actively involved in the major aspects of the anti-cancer activity of EGCG in vivo.

WITHDRAWN: Association of TNF-α-308G>A polymorphisms with hepatocellular carcinoma in Han Chinese population: A systematic review and meta-analysis

The Editor and Publisher of "Clinics and Research in Hepatology and Gastroenterology" have decided to withdraw this article because they consider that it has been accepted based upon the positive advice of at least one faked reviewer report. This manipulation of the peer-review process represents a clear violation of the fundamentals of peer review, our publishing policies, and publishing ethics standards. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy. The Publisher apologizes for any inconvenience this may cause.

Green tea polyphenol EGCG suppresses Wnt/β-catenin signaling by promoting GSK-3β- and PP2A-independent β-catenin phosphorylation/degradation

(-)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, has been reported to inhibit the Wnt/β-catenin pathway, which is aberrantly up-regulated in colorectal cancers, but its precise mechanism of action remains unclear. Here, we used a sensitive cell-based system to demonstrate that EGCG suppresses β-catenin response transcription (CRT), activated by Wnt3a-conditioned medium (Wnt3a-CM), by promoting the degradation of intracellular β-catenin. EGCG induced β-catenin N-terminal phosphorylation at the Ser33/37 residues and subsequently promoted its degradation; however, this effect was not observed for oncogenic forms of β-catenin. Pharmacological inhibition or depletion of glycogen synthase kinase-3β (GSK-3β) did not abrogate the EGCG-mediated β-catenin degradation. EGCG did not affect the activity and expression of protein phosphatase 2A (PP2A). Consistently, the phosphorylation and degradation of β-catenin was found in adenomatous polyposis coli (APC) mutated colon cancer cells after EGCG treatment. EGCG repressed the expression of cyclin D1 and c-myc, which are β-catenin/T-cell factor-dependent genes, and inhibited the proliferation of colon cancer cells. Our findings suggest that EGCG exerts its cancer-preventive or anticancer activity against colon cancer cells by promoting the phosphorylation and proteasomal degradation of β-catenin through a mechanism independent of the GSK-3β and PP2A.

Epigenetic effects of green tea polyphenols in cancer

Epigenetics describes heritable alterations of gene expression and chromatin organization without changes in DNA sequence. Both hypermethylation and hypomethylation of DNA can affect gene expression and the multistep process of carcinogenesis. Epigenetic changes are reversible and may be targeted by dietary interventions. Bioactive compounds from green tea (GT) such as (-)-epigallocatechin gallate have been shown to alter DNA methyltransferase activity in studies of esophageal, oral, skin, Tregs, lung, breast and prostate cancer cells, which may contribute to the chemopreventive effect of GT. Three out of four mouse model studies have confirmed the inhibitory effect of (-)-epigallocatechin gallate on DNA methylation. A human study demonstrated that decreased methylation of CDX2 and BMP-2 in gastric carcinoma was associated with higher GT consumption. It is the goal of this review to summarize our current knowledge of the potential of GT to alter epigenetic processes, which may be useful in chemoprevention.

A RXR ligand 6-OH-11-O-hydroxyphenanthrene with antitumour properties enhances (-)-epigallocatechin-3-gallate activity in three human breast carcinoma cell lines

(−)-Epigallocatechin-3-gallate (EGCG) and chemotherapeutic agents cotreatment can improve cytotoxicity against cancer cells. We showed that EGCG and the rexinoid 6-OH-11-O-hydroxyphenanthrene (IIF), given together, were cytotoxic toward MCF-7, MCF-7TAM, and MDA-MB-231, three breast carcinoma cell lines showing different molecular characteristics. Cell growth arrest and apoptosis were greater after EGCG and IIF cotreatment than after individual administration. Cytotoxicity was related to upregulation of 67-kDa laminin receptor (LR67), one of the principal molecular targets of EGCG, and activation of the nuclear retinoic X receptors (RXRs) pathway. Furthermore, the transcription factor Forkhead box O3 (Foxo3a), a protein able to trigger apoptosis through upregulation of genes necessary for cell death, was activated. EGCG and IIF cotreatment produced a significant nuclear import of Foxo3a from the cytoplasm in MCF-7, MCF-7TAM, and MDA-MB-231 cells. In MCF-7TAM cells only, Foxo3a nuclear localization was associated with p473AKT downregulation. For the first time we showed that when EGCG and IIF, two harmless molecules, were given together, they might increase cytotoxicity in three breast carcinoma cell lines, two of them being representative of poorly responsive breast carcinoma types.

Dose-dependent functionality and toxicity of green tea polyphenols in experimental rodents

A large number of physiologically functional foods are comprised of plant polyphenols. Their antioxidative activities have been intensively studied for a long period and proposed to be one of the major mechanisms of action accounting for their health promotional and disease preventive effects. Green tea polyphenols (GTPs) are considered to possess marked anti-oxidative properties and versatile beneficial functions, including anti-inflammation and cancer prevention. On the other hand, some investigators, including us, have uncovered their toxicity at high doses presumably due to pro-oxidative properties. For instance, both experimental animal studies and epidemiological surveys have demonstrated that GTPs may cause hepatotoxicity. We also recently showed that diets containing high doses (0.5-1%) of a GTP deteriorated dextran sodium sulfate (DSS)-induced intestinal inflammation and carcinogenesis. In addition, colitis mode mice fed a 1% GTP exhibited symptoms of nephrotoxicity, as indicated by marked elevation of serum creatinine level. This diet also increased thiobarbituric acid-reactive substances, a reliable marker of oxidative damage, in both kidneys and livers even in normal mice, while the expression levels of antioxidant enzymes and heat shock proteins (HSPs) were diminished in colitis and normal mice. Intriguingly, GTPs at 0.01% and 0.1% showed hepato-protective activities, i.e., they significantly suppressed DSS-increased serum aspartate aminotransferase and alanine aminotransferase levels. Moreover, those diets remarkably restored DSS-down-regulated expressions of heme oxygenase-1 and HSP70 in livers and kidneys. Taken together, while low and medium doses of GTPs are beneficial in colitis model mice, unwanted side-effects occasionally emerge with high doses. This dose-dependent functionality and toxicity of GTPs are in accordance with the concept of hormesis, in which mild, but not severe, stress activates defense systems for adaptation and survival.

EGCG enhances the efficacy of cisplatin by downregulating hsa-miR-98-5p in NSCLC A549 cells

In the current study, the enhanced efficacy of cisplatin caused by (-)-epigallocatechin-3-gallate (EGCG) in nonsmall cell lung cancer (NSCLC) A549 cells was observed. The tumor size was significantly smaller in vivo in the combination of cisplatin and EGCG group, as compared with cisplatin-only group. However, in NCI-H460 cells, another kind of NSCLC cells, the efficacy of cisplatin was antagonized by EGCG. MiRNA microarray showed that hsa-miR-98-5p and hsa-miR-125a-3p were differentially expressed after EGCG treatment in these 2 cell lines. After transfection of hsa-miR-98-5p inhibitor, the survival fraction of both A549 and NCI-H460 cells was decreased upon cisplatin treatment. Meanwhile, as a critical regulator in the cisplatin-induced apoptosis, p53 was elevated by silencing of hsa-miR-98-5p. These results suggested that EGCG inhibited the expression of hsa-miR-98-5p, followed by an increase of p53, thus the efficacy of cisplatin was enhanced. Bioinformatics analysis showed that hsa-miR-125a-3p might have a strong connection with classical MAPK pathway. Taken together, these findings indicate that hsa-miR-98-5p could be a potential target in clinical cisplatin treatment of NSCLC. The combination of EGCG and cisplatin might be an effective therapeutic strategy in treating some type of NSCLC, although the possibility of antagonistic interactions must also be taken into account.