Compound In Green Tea Research Articles

Bioaccessibility of green tea polyphenols incorporated into an edible agar film during simulated human digestion

Simple edible films can be manufactured to meet not only their primary protective purpose but can be easily manipulated to meet sensory expectations and to contain compounds which enhance the protective properties or even have the potential to deliver health benefits. However, the use of such edible films not only to protect the food but as a vehicle to deliver health benefits has not been investigated. In this paper we study agar films containing an aqueous extract of green tea, rich in polyphenol compounds, and the bioaccessibility of these compounds during simulated digestion in the upper gastro-intestinal tract using a dynamic gastric model (DGM) and a static duodenal model. It is concluded that the recovery of the tea compounds added to the agar film mainly occurs in the stomach (50–80%) and that little or no additional recovery is observed in the duodenum. Furthermore, the green tea compounds recovered show both reducing power and radical scavenging ability, but not antimicrobial activity. The bioaccessibility of the green tea flavonols is reduced in the presence of gelatin used to simulate the presence of protein in the stomach, but it is not clear if this is due to reduced release or sequestration of released compounds by the gelatin.

Characterization of tea catechins-loaded nanoparticles prepared from chitosan and an edible polypeptide

Tea catechins, the major polyphenolic compounds in green tea are potent antioxidant with numerous attributed health benefits. However, oral administration of the oxidation-sensitive compounds is limited by the harsh environment of the gastrointestinal tract (GIT) and become an important challenge. In this study, self-assembled nanoparticles composed of chitosan (CS) and an edible polypeptide, poly(γ-glutamic acid) (γ-PGA) were prepared for the delivery of tea catechins. The tea catechins-loaded nanoparticles were pH-responsive and demonstrated different tea catechins release profiles in simulated gastrointestinal tract (GI tract) media. Sustained free radical (DPPH and ABTS+) scavenging assays showed that the antioxidant activity of tea catechins was retained by the nanoparticles. The nanoparticles with a positive surface charge could transiently open the tight junctions between Caco-2 cells and thus increased the paracellular transport of tea catechins. These results demonstrate that CS/γ-PGA nanoparticles can be effective as a carrier for oral delivery of tea catechins with effective antioxidant activity.

Prostanoid EP1 receptor as the target of (−)-epigallocatechin-3-gallate in suppressing hepatocellular carcinoma cells in vitro

To investigate the effects of (-)-epigallocatechin-3-gallate (EGCG), an active compound in green tea, on prostaglandin E(2) (PGE(2))-induced proliferation and migration, and the expression of prostanoid EP(1) receptors in hepatocellular carcinoma (HCC) cells. HCC cell line HepG2, human hepatoma cell lines MHCC-97L, MHCC-97H and human hepatocyte cell line L02 were used. Cell viability was analyzed using MTT assay. PGE(2) production was determined with immunoassay. Wound healing assay and transwell filter assay were employed to assess the extent of HCC cell migration. The expression of EP(1) receptor and Gq protein were examined using Western blot assay. PGE(2) (4-40000 nmol/L) or the EP(1) receptor agonist ONO-DI-004 (400-4000 nmol/L) increased the viability and migration of HepG2 cells in concentration-dependent manners. EGCG (100 μg/mL) significantly inhibited the viability and migration of HepG2 cells induced by PGE(2) or ONO-DI-004. HepG2 cells secreted an abundant amount of PGE(2) into the medium, and EGCG (100 μg/mL) significantly inhibited the PGE(2)production and EP(1) receptor expression in HepG2 cells. EGCG (100 μg/mL) also inhibited the viability of MHCC-97L cells, but not that of MHCC-97H cells. Both EGCG (100 μg/mL) and EP(1) receptor antagonist ONO-8711 inhibited PGE(2) 4 μmol/L and ONO-DI-004 400 nmol/L-induced growth and migration of HepG2 cells. Both EGCG (100 μg/mL) and ONO-8711 210 nmol/L inhibited PGE(2)- and ONO-DI-004-induced EP(1) expression. EGCG and ONO-8711 had synergistic effects in inhibiting EP(1) receptor expression. PGE(2), ONO-DI-004, ONO-8711, and EGCG had no effects on Gq expression in HepG2 cells, respectively. These findings suggest that the anti-HCC effects of EGCG might be mediated, at least partially, through the suppressing EP(1) receptor expression and PGE(2) production.

Impact of Brewing Conditions on the Antioxidant Capacity of Green Tea

The polyphenolic compounds in green tea, have well established antioxidant activity, which may be responsible for the health benefits of drinking green tea described in research literature.ObjectiveTo measure the impact of infusion conditions on the oxygen radical absorbance capacity (ORAC) of several green teas.MethodsA fluorescence‐based ORAC assay was developed and validated. Infusion conditions were varied systematically; including temperature, duration, source, variety, brewing environment, and preparation method. Antioxidant capacity results were calculated in units of mM Trolox/g tea based on standard Trolox equivalents. We also describe a new measure of total inherent antioxidant potential (TI‐ORAC), defined as the area under the ORAC curve over a standard number of infusions.ResultsBrewing time, and tea source, had a significant impact on single infusion ORAC values, while time between brews and temperature had minimal impact on ORAC. TI‐ORAC varied considerably across varieties of green tea; and between two environments.ConclusionsInfusion conditions impact the ORAC of green tea, which may impact its health benefits. TI‐ORAC may be a novel assay to consider in continued research of tea and other natural products. This research was supported by grant number 5T32 AT00815‐03 from the National Center for Complementary and Alternative Medicine.

Structural Properties of EGCG-Induced, Nontoxic Alzheimer's Disease Aβ Oligomers

The green tea compound epigallocatechin-3-gallate (EGCG) inhibits Alzheimer's disease β-amyloid peptide (Aβ) neurotoxicity. Solution-state NMR allows probing initial EGCG–Aβ interactions. We show that EGCG-induced Aβ oligomers adopt a well-defined structure and are amenable for magic angle spinning solid-state NMR investigations. We find that EGCG interferes with the aromatic hydrophobic core of Aβ. The C-terminal part of the Aβ peptide (residues 22–39) adopts a β-sheet conformation, whereas the N-terminus (residues 1–20) is unstructured. The characteristic salt bridge involving residues D23 and K28 is present in the structure of these oligomeric Aβ aggregates as well. The structural analysis of small-molecule-induced amyloid aggregates will open new perspectives for Alzheimer's disease drug development.

Abstract A40: Epigenetic modification of human colon cancer by the green tea polyphenol EGCG

Abstract Silencing of regulatory genes through hypermethylation of CpG islands is an important mechanism in tumorigenesis of numerous cancers. We have previously shown that Retinoid X Receptor alpha (RXRα) is silenced in tumors of the colon cancer AOM-APC/min+ mouse model. Upon treatment with green tea, RXRα expression was restored and intestinal tumorigenesis was inhibited. We examined human colonic tumor microarrays by immunohistochemcial staining and found a marked decrease in RXR expression in tumor tissue compared to normal matched tissues, inversely β-Catenin levels increased. To determine how RXRα loss is reversed in human cancers by green tea, we treated HT-29 (methylation insensitive) and HCT116 (methylation sensitive) human colon cancer cell lines with different concentrations of Epigallocatechin gallate (EGCG - major polyphenolic compound in green tea). We found by western blotting nuclear protein fractions that EGCG can restore RXRα levels in HCT116 cells in a dose dependant manner. Using these same lysates, we probed for presence of the most common DNA Methyltransferases (DNMTs) and Histone Deacetylases (HDACs). We found that expression of DNMTs as well as HDACs was inhibited in a dose dependent manner following treatment with EGCG. Additionally we examined by real time PCR, the message levels of DNMTs in cells treated with EGCG to determine if they correlate with the observed downregulation in protein expression. We can conclude that the silencing of RXRα may be due in part to by repressing effects of EGCG on DNMT as well as HDAC activity. Our results here show that EGCG, a common dietary compound, can modulate the reversal of gene-silencing involved colon carcinogenesis and maybe a possible avenue for colon cancer therapy and demonstrates be one potential mechanism of cancer chemoprevention in green tea that outlines a new epigenetic pathway. Citation Information: Cancer Prev Res 2011;4(10 Suppl):A40.

Abstract A39: EGCG, a green tea polyphenol, can reverse methylation related silencing of genes in human colon carcinomas

Abstract Silencing of regulatory genes through hypermethylation of CpG islands is an important mechanism in tumorigenesis. In colon cancer, RXRα, an important dimerization partner with other nuclear transcription factors, is silenced through this mechanism. Previous studies from our laboratory have shown that ApcMin/+ mice treated with the carcinogen azoxymethane (AOM) will develop colonic tumors but when treated with green tea a reduction in tumor numbers was found. We found that colon tumors had lower expression of RXR protein but expression levels were restored by treatment with green tea. We also found that the degree of promoter methylation of the RXR gene was reduced. To translate these findings to human colon cancer we treated CpG Island Methylator Phenotype sensitive and insensitive (CIMP+ & CIMP-) human colon cancer cell lines with epigallocatechin gallate (EGCG - major polyphenolic compound in green tea). We hypothesized that CIMP+ cell lines which epigenetically silence key regulatory genes would demonstrate silencing of RXRα and that EGCG would restore its expression. To test this we used the following human colon cancer cell lines: HCT116, SW48, HCT15 - CIMP+; HT29, SW480, SW620 - CIMP- and IEC-6 - normal control. We found EGCG to restore RXR activity levels in the CIMP+ lines, in a dose dependent manner (0, 50, 100 & 150 μM EGCG was tested for 48 and 72 hour durations). EGCG also reduced RXRα promoter methylation in one CpG island from a CIMP+ cell line compared to a CIMP-line. We found that EGCG produced methylation changes in several other colon cancer related genes but did not cause a decrease in global methylation. Numerous epidemiological reports have shown the benefits of green tea consumption in reducing colon cancer risk but to date no studies have shown that some of the risk reduction may be related to the epigenetic regulation of key genes by constituent tea polyphenols. Our results here show that EGCG, a common tea polyphenolic compound, can modulate the reversal of gene-silencing involved colon carcinogenesis and maybe a possible avenue for colon cancer treatment. Supported by USPHS grant CA96694 from the National Cancer Institute. Citation Information: Cancer Prev Res 2011;4(10 Suppl):A39.

Catechin hydrate inhibits proliferation and mediates apoptosis of SiHa human cervical cancer cells

Catechin hydrate (CH), one of the chemical compounds in green tea, has been shown to inhibit tumor growth. Green tea possesses anticancer potential and is one of the most commonly used herbal medicines worldwide. In this study, we sought to characterize the DNA damage and downstream genes targeted by CH extracts using SiHa human cervical cancer cells. The efficacy of CH in killing cervical cancer cells in vitro was investigated in this study to determine whether CH possesses anticancer potential and could be developed as a therapeutic agent for cervical cancer upon further investigation. To scientifically validate the anticancer activities of CH on cervical cancer, CH was tested for its cytotoxic and growth-inhibition properties, specifically the induction of apoptosis in SiHa cervical cancer cells. CH showed a 50% inhibition of SiHa human cervical cancer cells at a concentration of 196.07μg/mL at 24h. CH induced the several folds increase of caspase-3, -8, and -9 after 24h and 48h; the increase of these genes may be involved in the induction of apoptosis. The analysis of apoptosis by DeadEnd terminal transferase-mediated dUTP-digoxigenin-end labeling (TUNEL) assay was used to further confirm that CH induced apoptosis. The results suggested that CH has the potential to benefit cervical cancer prevention. This is the first report that shows the possible mechanism of the anti-proliferative effects of CH in the prevention of cervical cancer in cell culture models. CH, either in its original form or in combination with other anticancer drugs, could potentially be an alternative medicine for cervical cancer. Further study may increase our understanding of the mechanism by which CH has an effect on cervical cancer therapy.

Inhibition of sonic hedgehog pathway and pluripotency maintaining factors regulate human pancreatic cancer stem cell characteristics

Activation of the sonic hedgehog (SHh) pathway is required for the growth of numerous tissues and organs and recent evidence indicates that this pathway is often recruited to stimulate growth of cancer stem cells (CSCs) and to orchestrate the reprogramming of cancer cells via epithelial mesenchymal transition (EMT). The objectives of this study were to examine the molecular mechanisms by which (-)-epigallocatechin-3-gallate (EGCG), an active compound in green tea, inhibits self-renewal capacity of pancreatic CSCs and synergizes with quercetin, a major polyphenol and flavonoid commonly detected in many fruits and vegetables. Our data demonstrated that EGCG inhibited the expression of pluripotency maintaining transcription factors (Nanog, c-Myc and Oct-4) and self-renewal capacity of pancreatic CSCs. Inhibition of Nanog by shRNA enhanced the inhibitory effects of EGCG on self-renewal capacity of CSCs. EGCG inhibited cell proliferation and induced apoptosis by inhibiting the expression of Bcl-2 and XIAP and activating caspase-3. Interestingly, EGCG also inhibited the components of SHh pathway (smoothened, patched, Gli1 and Gli2) and Gli transcriptional activity. Furthermore, EGCG inhibited EMT by inhibiting the expression of Snail, Slug and ZEB1, and TCF/LEF transcriptional activity, which correlated with significantly reduced CSC's migration and invasion, suggesting the blockade of signaling involved in early metastasis. Furthermore, combination of quercetin with EGCG had synergistic inhibitory effects on self-renewal capacity of CSCs through attenuation of TCF/LEF and Gli activities. Since aberrant SHh signaling occurs in pancreatic tumorigenesis, therapeutics that target SHh pathway may improve the outcomes of patients with pancreatic cancer by targeting CSCs.

Removal of caffeine from green tea by microwave-enhanced vacuum ice water extraction

In order to selectively remove caffeine from green tea, a microwave-enhanced vacuum ice water extraction (MVIE) method was proposed. The effects of MVIE variables including extraction time, microwave power, and solvent to solid radio on the removal yield of caffeine and the loss of total phenolics (TP) from green tea were investigated. The optimized conditions were as follows: solvent (mL) to solid (g) ratio was 10:1, microwave extraction time was 6min, microwave power was 350W and 2.5h of vacuum ice water extraction. The removal yield of caffeine by MVIE was 87.6%, which was significantly higher than that by hot water extraction, indicating a significant improvement of removal efficiency. Moreover, the loss of TP of green tea in the proposed method was much lower than that in the hot water extraction. After decaffeination by MVIE, the removal yield of TP tea was 36.2%, and the content of TP in green tea was still higher than 170mgg−1. Therefore, the proposed microwave-enhanced vacuum ice water extraction was selective, more efficient for the removal of caffeine. The main phenolic compounds of green tea were also determined, and the results indicated that the contents of several catechins were almost not changed in MVIE. This study suggests that MVIE is a new and good alternative for the removal of caffeine from green tea, with a great potential for industrial application.

Abstract 4627: Potent chemotherapeutic activity of green tea polyphenols, blueberry anthocyanidin mixture and cisplatin: Synergistic effects

Abstract A significant progress has been made in the prognosis of several cancers (e.g., breast and prostate cancers). However, the prognosis of lung cancer remains grim. Furthermore, up to 50% of stage I/II non-small-cell lung cancer (NSCLC) patients develop recurrence/metastasis within five years of their treatments. It is eminent that natural compounds or food-based bioactives with minimal toxicity be identified for their use in neo-adjuvant chemotherapy and/or after the primary cancer treatment for enhanced efficacy. Green tea and berries are drawing increased attention due to their potential anti-cancer effects. The active compounds in green tea and berries are polyphenols, e.g., epigallocatechin gallate (EGCG) and anthocyanidins (e.g. delphinidin, cyanidin, peonidin, petunidin, malvidin in blueberry), respectively. We previously demonstrated synergistic antiproliferative activity from these Anths against H1299 lung cancer cells both in vitro and in vivo (Kausar et al. AACR 51: 1884, 2010). In this study we investigated the combined effect of EGCG and the blueberry anthocyanidins (EGCG-Anths) alone and in combination with a common chemotherapeutic drug, cisplatin on lung cancer H1299 cell using MTT assay. The antiproliferative activity of EGCG-Anths (6 μM), measured as IC50, was found to be 2- and 4-fold lower compared with Anths (12 μM) and EGCG (21 μM) alone, respectively. The IC50 of cisplatin was found to be ≈50 μM. However, when combined with the EGCG-Anths (10 μM each), the IC50 of cisplatin was significantly reduced (<3 μM). Flow cytometric analysis for cell cycle distribution and apoptosis revealed cell cycle arrest and enhanced apotosis induced by the combination mixture. Western blot analysis for the involved molecular targets showed that selected proteins (cyclin D1, B1, Cdc2, p21, PCNA, Bax, Bcl-2, PARP, etc.) associated with cell cycle and apoptosis were more significantly modulated by the combination, EGCG-Anths-cisplatin than with the individual entities. Together, our data suggest that combination of EGCG-Anths alone or in combination with suboptimal doses of cisplatin may be effective in neo-adjuvant chemotherapy or can be used as maintenance drug for the prevention of lung cancer recurrence/metastasis and minimize toxicity issues associated with high dose cisplatin (Supported from KLCRP, T32-ES011564 and Agnes Brown Duggan Endowment). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4627. doi:10.1158/1538-7445.AM2011-4627

Green Tea Polyphenols as Proteasome Inhibitors: Implication in Chemoprevention

Next to water, tea is the most popular beverage in the world. The most abundant and active compound in green tea is (-)-epigallocatechin-3-gallate (EGCG), which is extensively studied for its cancer-preventive and anti-cancer activities as well as its cellular targets. One potential molecular target of EGCG is the proteasome. While molecular docking and structure-activity relationship (SAR) analysis suggests that the ester carbon of EGCG is important for mediating its proteasome-inhibitory activity, EGCG is very unstable under physiological conditions. Therefore, a series of analogs were synthesized aiming to improve stability and bioavailability of EGCG. Among them, peracetate-protected or the prodrug of EGCG was found to have increased bioavailability, stability, and proteasome-inhibitory activities against various human cancer cells and tumors compared to EGCG, suggesting its potential use for cancer prevention and treatment. Epidemiological studies have indicated that green tea consumption is associated with the reduced risk of cancers, especially associated with the reduced risk of late stage of cancers. This risk reduction may be attributed not only to proteasome inhibition, but also to numerous other intracellular molecules targeted by EGCG that are involved in cell cycle regulation, apoptosis, angiogenesis, and metastasis.

Modulation of Ca2+ Signals by Epigallocatechin-3-gallate(EGCG) in Cultured Rat Hippocampal Neurons

Green tea has been receiving considerable attention as a possible neuroprotective agent against neurodegenerative disease. Epigallocatechin-3-gallate (EGCG) is the major compound of green tea. Calcium signaling has profound effects on almost all aspects of neuronal function. Using digital calcium imaging and patch-clamp technique, we determined the effects of EGCG on Ca2+ signals in hippocampal neurons. The results indicated that EGCG caused a dose-dependent increase in intracellular Ca2+ ([Ca2+]i). This [Ca2+]i increase was blocked by depleting intracellular Ca2+ stores with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin and cyclopiazonic acid. Furthermore, EGCG-stimulated increase in [Ca2+]i was abolished following treatment with a PLC inhibitor. However, EGCG inhibited high-voltage activated Ca2+ currents (IHVA) and NMDA-induced inward currents (INMDA). These data suggest that EGCG triggers a cascade of events: it activates phospholipase C (PLC), mobilizes intracellular Ca2+ stores, raises the cytosolic Ca2+ levels, and inhibits the VGCC and NMDA receptors-mediated Ca2+ influx through a process that remains to be determined.

Multistage carcinogenesis process as molecular targets in cancer chemoprevention by epicatechin-3-gallate

The consumption of green tea has long been associated with a reduced risk of cancer development. (-)-Epicatechin-3-gallate (ECG) or (-)-epigallocatechin-3-gallate (EGCG) are the major antioxidative polyphenolic compounds of green tea. They have been shown to exert growth-inhibitory potential of various cancer cells in culture and antitumor activity in vivo models. ECG or EGCG could interact with various molecules like proteins, transcription factors, and enzymes, which block multiple stages of carcinogenesis via regulating intracellular signaling transduction pathways. Moreover, ECG and EGCG possess pharmacological and physiological properties including induction of phase II enzymes, mediation of anti-inflammation response, regulation of cell proliferation and apoptosis effects and prevention of tumor angiogenesis, invasion and metastasis. Numerous review articles have been focused on EGCG, however none have been focused on ECG despite many studies supporting the cancer preventive potential of ECG. To develop ECG as an anticarcinogenic agent, more clear understanding of the cell signaling pathways and the molecular targets responsible for chemopreventive and chemotherapeutic effects are needed. This review summarizes recent research on the ECG-induced cellular signal transduction events which implicate in cancer management.

Herbal therapy use by cancer patients: A literature review on case reports

Complementary and alternative medicine use is common amongst cancer patients. In many surveys, herbal medicines are amongst the most commonly used group of treatments. Herbal remedies are believed by the general public to be safe, cause less side-effects and less likely to cause dependency. The authors performed a literature review to assess which herbal approaches have had associated cancer case reports and determine which of these have been studied in prospective research. Eighteen case reports of patients having apparent antitumour effects from herbal therapy and 21 case reports of toxic effects of herbs used by cancer patients were identified. Clinicaltrials.gov and MEDLINE (via PubMed) were searched for each of the herbal products identified in these reports. Clinical trials in cancer populations were identified for green tea extracts or compounds ( n = 34), phytoestrogens ( n = 27), mistletoe ( n = 8), Ganoderma lucidum ( n = 1), noni ( n = 1) and Silymarin ( n = 1). Daikenchuto, PC-SPES, Nyoshinsan/TJ and Saw palmetto have also been studied prospectively. In conclusion, some of the herbs with promising case report findings have undergone prospective clinical investigations but many others have either not yet been explored or the results have not been reported in English. Unconventional therapies, such as herbs and minerals, used in ancient medical traditions have led to the identification of active anticancer agents. Mechanisms to support prospective research with such approaches are discussed.

Role of (−)-epigallocatechin-3-gallate in cell viability, lipogenesis, and retinol-binding protein 4 expression in adipocytes

(-)-Epigallocatechin-3-gallate (EGCG), a bioactive compound of green tea, is known to combat obesity by reducing the viability and lipid accumulation of adipocytes. In this study, we evaluated the mechanism and clinical relevance on those actions of EGCG. We measured the viability of 3T3-L1 preadipocytes and adipocytes by the 3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide assay. Lipid accumulation was measured by Oil Red O staining. Intracellular accumulation of reactive oxygen species (ROS) was determined using a flow cytometer. Cellular glucose uptake was determined with 2-deoxy-[(3)H]-glucose. The protein levels of peroxisome proliferator-activated receptor (PPAR)-γ and adiponectin in 3T3-L1 adipocytes, as well as the protein level and secretion of plasma retinol-binding protein (RBP4) in human adipocytes, were measured by western blot. EGCG at concentrations higher than 10μM induced ROS generation and decreased the viability and lipid accumulation of adipocytes. It also decreased the expression of PPAR-γ and adiponectin. At concentrations readily achievable in human plasma via green tea intake (≤10μM), EGCG inhibited cellular glucose uptake and enhanced the expression and secretion of RBP4 in adipocytes. Pharmacological doses of EGCG showed cytotoxic effects in preadipocytes and adipocytes. EGCG-mediated glucose uptake inhibition in adipocytes may be clinically relevant and is probably linked to the increase in the expression and secretion of RBP4. Because secreted RBP4 from adipocytes inhibits muscular glucose uptake and enhance hepatic glucose output, the systemic effect of EGCG associated with its effect on RBP4 secretion should be further determined, as it may negatively regulate whole-body insulin sensitivity, contrary to general belief.

Green tea catechins augment the antitumor activity of doxorubicin in an in vivo mouse model for chemoresistant liver cancer

Green tea catechins have been reported to have antitumor activity. The objective of this study was to examine the effect of catechins on the antitumor efficacy of doxorubicin (DOX) in a murine model for chemoresistant hepatocellular carcinoma (HCC). Epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) are the most abundant polyphenolic compounds in green tea. Here, we show that ECG or EGCG at higher doses had a slight inhibitory effect on cell proliferation in the resistant human HCC cell line BEL-7404/DOX in vitro and in vivo, whereas the administration of DOX with these compounds at lower doses significantly inhibited HCC cell proliferation in vitro and hepatoma growth in a xenograft mouse model, compared with treatment with either agent alone at the same dose. Furthermore, the administration of DOX in combination with ECG or EGCG markedly enhanced intracellular DOX accumulation, which implies that the catechins inhibited P-glycoprotein (P-gp) efflux pump activity. Consistent with these results, the intracellular retention of rhodamine 123, a P-gp substrate, was increased and the level of P-gp was decreased in cells concurrently treated with DOX and ECG or EGCG. EGCG increased topo II expression, but did not alter GST protein levels in tumor xenografts. The expression of MDR1 and HIF-1alpha mRNA was obviously reduced, whereas MRP1 and LRP expression was not changed significantly. These data suggest that tea catechins at non-toxic doses can augment DOX-induced cell killing and sensitize chemoresistant HCC cells to DOX. The chemosensitizing effect of catechins may occur directly or indirectly by reversal of multidrug resistance, involving the suppression of MDR1 expression, or by enhancement of intracellular DOX accumulation, involving inhibition of P-gp function.

Green tea compound in chemoprevention of cervical cancer.

Human papillomavirus (HPV) infection is closely associated with the development of more than 95% of cervical cancer. Clinical trials using several chemopreventive agents are underway, but results are inconclusive. Most agents used in trials inhibited the growth of cancer cells in vitro, and about half of patients had some degree of clinical responses; however, the therapeutic effect was confounded by high rates of spontaneous regression and relapse. The selection of nontoxic agents especially food, beverage, and natural products that suppress oncogenic HPV, inhibit malignant transformation, and can additionally be used long term may be important for cervical cancer prevention. We evaluated green tea compound (epigallocatechin gallate and polyphenols E) effects on immortalized cervical epithelial and cervical cancer cells. HPV-immortalized cervical epithelial cells, TCL1, and HPV-positive cervical cancer cells, Me180 and HeLa, were used in the study. The effects of green tea compounds on cell growth, apoptosis, cell cycle, and gene expression were examined and characterized. Both epigallocatechin gallate and polyphenols E inhibited immortalized cervical epithelial and cancer cell growth. Apoptosis induction and cell cycle changes were observed in a dose-dependent manner. Western blot analysis of apoptosis-related proteins, p53 and p21, showed dose-dependent increase, whereas p27 was not affected. HPV-E7 protein expression was decreased by green tea compounds. This study provides information on the potential mechanisms of action of green tea compounds in suppression of HPV-related cervical cells, and it will enable us to assess the feasibility of using these agents.

Abstract 3798: Epigallocatechin-3-gallate and atorvastatin induce translocation of eGFP-LC3 in immortalized baby mouse kidney cells suggesting of a link between autophagy and apoptosis

Abstract Epigallocatechin-3-gallate (EGCG), the major polyphenolic compound in green tea, and atorvastatin (ATST), a commonly used cholesterol-lowing medication, have been reported to have cancer preventive activities and to induce cancer cell apoptosis. However, the mechanisms of these activities are still unclear. Here we report that EGCG and ATST could induce cell autophagy, which may be linked to the induction of cell apoptosis. In immortalized baby mouse kidney (iBMK) cells that overexpress eGFP-tagged LC3, EGCG at 3, 6 and 12 μM exhibited a dose-dependent induction of the translocation of eGFP-LC3, an indicator of the formation of autophagosomes, as observed by fluorescent microscopy. ATST at 2 and 4 μM also induced the translocation of eGFP-LC3. Western-blot analysis showed that 25 μM EGCG and 4 μM ATST treatment for 24 h induced the appearance of LC3-II, a higher migrating band, indicating the occurrence of autophagy. Beclin +/− iBMK cells also displayed autophagy upon treatment with 25 μM EGCG for 24h, but to a less extent as compared to Beclin +/+ cells. The induction of the appearance of eGFP-LC3 puncta could not be eliminated by addition of superoxide dismutase plus catalase, enzymes that were used to inhibit the auto-oxidation of EGCG and the production of reactive oxygen species. The results suggest that the induction of autophagy is not caused by EGCG auto-oxidation produced oxidative stress. ATST inhibited the proliferation of iBMK cells in 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, but the inhibition was to a less extent in Beclin +/− cells as compared to Beclin +/+ cells. EGCG and ATST treatment resulted in an increase of cleaved caspase 3, a hallmark of cell apoptosis, and a decrease of anti-apoptotic Bcl-2. Beclin +/+ iBMK cells showed stronger and earlier induction of these apoptotic markers than Beclin +/− cells, indicating that induction of apoptotic marker is correlated to the ability of cells to produce autophagy. EGCG at 25 μM and ATST at 2 μM also induced the appearance of endogenous LC3-II in human colon cancer HCT116 cells. The induction of autophagy may be a key mechanism for EGCG and ATST to inhibit cancer growth and formation (This research is supported by NIH grants CA 120915 and CA 133021). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3798.

Inhibitory action of green tea on non‐heme iron absorption is not reversed by ascorbic acid in intestinal cells

There is persuasive epidemiological evidence that regular consumption of green tea promotes human health. Because the polyphenolic compounds in green tea have a wide range of effects in vivo and vitro, including chelation of iron, it is prudent to test whether the regular intake of green tea impair the utilization of dietary iron. The influence of green tea extract (GTE) on intestinal iron absorption was initially examined in Caco‐2 intestinal cells. Addition of GTE significantly (P < 0.001) decreased transepithelial iron transport in a dose ‐ dependent manner although apical iron uptake was significantly (P < 0.001) increased by GTE. Since ascorbic acid is known to promote non‐heme iron absorption, the possible counteractive effect of ascorbic acid on the inhibitory action of GTE in iron absorption was tested. The addition of ascorbic acid to the GTE treated cells did not significantly change the inhibitory action of GTE on non‐heme iron absorption. Our data suggest that GTE inhibits non‐heme iron absorption by reducing basolateral iron transport rather than by decreasing apical iron import. Furthermore, the inhibitory effects of GTE on non‐heme iron absorption can not be reversed by ascorbic acid.