Novel and potent inhibitors of fatty acid synthase derived from catechins and their inhibition on MCF-7 cells

Fatty acid synthase (FAS) is a potential target for cancer, but potent inhibitors against FAS are scarce. In this study, we found that activities of catechins on inhibiting FAS increased greatly by heating them in acid. The enhancement was positively correlated to H⁺ concentration. The inhibitory activities of the final products from different catechins were similar, all of which were less than 1 μg/mL. The product from ( ? )-epigallocatechin gallate (EGCG) was stable at room temperature, and its inhibitory kinetics and reacting sites on FAS were obviously different from the known FAS inhibitors. It also affected the viability of MCF-7 cells more obviously than EGCG. A putative route of the reaction progress was proposed and the effective inhibitors were deduced to be oligomers of 2-hydroxy-3-(3′, 4′, 5′-trihydroxyphenyl) propenoic acid by analysis of their spectra. The work affords new and potent FAS inhibitors that would be promising candidates for the treatment of cancer.     

Evaluation of the inhibitory activities of aceraceous plants on fatty acid synthase

Fatty acid synthase (FAS) is a very significant lipogenic enzyme participating in energy metabolism in vivo and has been reported as a potential new therapeutic target for cancer treatment. The extracts from sixteen Aceraceae were prepared to assay their inhibitory activities against duck liver FAS and their correlated antitumor bioactivity. Their inhibition of FAS was composed of a reversible fast-binding inhibition, by which 0.41 microg/mL of the A. campestre extract inhibits 50% FAS activity, and an irreversible slow-binding inhibition with inactivation rate constants, k(obs), ranging between 1.5 x 10(-3) and 10.6 x 10(-3) min(-1). Three Aceraceae extracts were selected from their smaller IC50 values to study different type of inhibitions against the three substrates in the FAS overall reaction. As compared with other reported FAS inhibitors including EGCG with regard to inhibition constant and IC50 value, the extracts appeared to be more efficient inhibitors, and exhibited a considerable inhibition against the growth of five types of cancer cells (China patent application number 200610088901.6), which may be related to the inhibition of lipogenesis in these cells.     

Matrix metalloproteinase inhibition by green tea catechins

We have investigated the effects of different biologically active components from natural products, including green tea polyphenols (GTP), resveratrol, genistein and organosulfur compounds from garlic, on matrix metalloproteinase (MMP)-2, MMP-9 and MMP-12 activities. GTP caused the strongest inhibition of the three enzymes, as measured by fluorescence assays using gelatin or elastin as substrates. The inhibition of MMP-2 and MMP-9 caused by GTP was confirmed by gelatin zymography and was observed for MMPs associated with both various rat tissues and human brain tumors (glioblastoma and pituitary tumors). The activities of MMPs were also measured in the presence of various catechins isolated from green tea including (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate(ECG), (-)-epigallocatechin (EGC), (-)-epicatechin (EC) and (+)-catechin (C). The most potent inhibitors of these activities, as measured by fluorescence and by gelatin or casein zymography, were EGCG and ECG. GTP and the different catechins had no effect on pancreatic elastase, suggesting that the effects of these molecules on MMP activities are specific. Furthermore, in vitro activation of proMMP-2 secreted from the glioblastomas cell line U-87 by the lectin concanavalin A was completely inhibited by GTP and specifically by EGCG. These results indicate that catechins from green tea inhibit MMP activities and proMMP-2 activation.     

Analysis of the mechanism of inhibition of human matrix metalloproteinase 7 (MMP-7) activity by green tea catechins

Green tea catechins inhibit human matrix metalloproteinase 7 (MMP-7) activity non-competitively, and the galloyl group is essential for potent inhibition (Oneda et al., J. Biochem., 133, 571-576 (2003)). In this study, we analyzed the mechanism of this inhibition. In the hydrolysis of (7-methoxycoumarin-4-yl)acetyl-L-Pro-L-Leu-Gly-L-Leu-[N(3)-(2,4-dinitrophenyl)-L-2,3-diaminopropionyl]-L-Ala-L-Arg-NH(2), the inhibitory effects of (-)-epigallocatechin-3-gallate (EGCG), (-)-gallocatechin-3-gallate (GCG), (-)-epicatechin-3-gallate (ECG), and (-)-catechin-3-gallate (CG) increased with increasing pH levels from 7.0 to 8.5. The inhibitory effects of EGCG and GCG were more potent than those of ECG and CG, and increased with increasing CaCl(2) concentrations from 10 to 50 mM. The fluorescence of EGCG and GCG decreased with increasing CaCl(2) concentrations and with the addition of MMP-7, while those of ECG and CG did not. Our results suggest that these differences result from that in the B ring, EGCG and GCG have phenol hydroxyl groups at the 3', 4', and 5' positions, while ECG and CG have them at the 3' and 4' positions.     

Distinct effects of tea catechins on 6-hydroxydopamine-induced apoptosis in PC12 cells.

Green tea polyphenols have aroused considerable attention in recent years for preventing oxidative stress related diseases including cancer, cardiovascular disease, and degenerative disease. Neurodegenerative diseases are cellular redox status dysfunction related diseases. The present study investigated the different effects of the five main components of green tea polyphenols on 6-hydroxydopamine (6-OHDA)-induced apoptosis in PC12 cells, the in vitro model of Parkinson's disease (PD). When the cells were treated with five catechins respectively for 30 min before exposure to 6-OHDA, (-)-epigallocatechins gallate (EGCG) and (-)-epicatechin gallate (ECG) in 50-200 microM had obvious concentration-dependent protective effects on cell viability, while (-)-epicatechin (EC), (+)-catechin ((+)-C), and (-)-epigallocatechin (EGC) had almost no protective effects. The five catechins also showed the same pattern described above of the different effects against 6-OHDA-induced cell apoptotic characteristics as analyzed by cell viability, fluorescence microscopy, flow cytometry, and DNA fragment electrophoresis methods. The present results indicated that 200 microM EGCG or ECG led to significant inhibition against typical apoptotic characteristics of PC12 cells, while other catechins had little protective effect against 6-OHDA-induced cell death. Therefore, the classified protective effects of the five catechins were in the order ECG> or = EGCG>EC> or = (+)-C>EGC. The antiapoptotic activities appear to be structurally related to the 3-gallate group of green tea polyphenols. The present data indicate that EGCG and ECG might be potent neuroprotective agents for PD.     

Evaluation of the inhibitory activities of aceraceous plants on fatty acid synthase

Fatty acid synthase (FAS) is a very significant lipogenic enzyme participating in energy metabolism in vivo and has been reported as a potential new therapeutic target for cancer treatment. The extracts from sixteen Aceraceae were prepared to assay their inhibitory activities against duck liver FAS and their correlated antitumor bioactivity. Their inhibition of FAS was composed of a reversible fast-binding inhibition, by which 0.41 μg/mL of the A. campestre extract inhibits 50% FAS activity, and an irreversible slow-binding inhibition with inactivation rate constants, k_obs, ranging between 1.5 × 10^{? 3} and 10.6 × 10^{? 3} min^{? 1}. Three Aceraceae extracts were selected from their smaller IC₅₀ values to study different type of inhibitions against the three substrates in the FAS overall reaction. As compared with other reported FAS inhibitors including EGCG with regard to inhibition constant and IC₅₀ value, the extracts appeared to be more efficient inhibitors, and exhibited a considerable inhibition against the growth of five types of cancer cells (China patent application number 200610088901.6), which may be related to the inhibition of lipogenesis in these cells.     

Green tea polyphenols as inhibitors of ribonuclease A

Ribonucleases (RNases), which are essential for cleavage of RNA, may be cytotoxic due to undesired cleavage of RNA in the cell. The quest for small molecule inhibitors of members of the ribonuclease superfamily has become indispensable with a growing number exhibiting unusual biological properties. Thus, inhibitors of RNases may serve as potential drug candidates. Green tea catechins (GTC), particularly its major constituent (-)-epigallocatechin-3-gallate (EGCG), have reported potential against cell proliferation and angiogenesis induced by several growth factors including angiogenin, a member of the RNase superfamily. This study reports the inhibition of bovine pancreatic ribonuclease A (RNase A) by EGCG and GTC. This has been checked qualitatively by an agarose gel based assay. Enzyme kinetic studies with cytidine 2',3' cyclic monophosphate as the substrate have also been conducted. Results indicate substantial inhibitory activity of a noncompetitive nature with an inhibition constant of approximately 80 microM for EGCG and approximately 100 microM for GTC measured in gallic acid equivalents.     

Fatty acid synthase inhibitors from the hulls of Nephelium lappaceum L

Natural products inhibiting fatty acid synthase (FAS) are appearing as potential therapeutic agents to treat cancer and obesity. The bioassay-guided chemical investigation of the hulls of Nephelium lappaceum L. resulted in the isolation of ten compounds (1–10) mainly including flavonoids and oleane-type triterpene oligoglycosides, in which all of the compounds were isolated from this plant for the first time. Additionally, compounds 8 and 9 were new hederagenin derivatives and were elucidated as hederagenin 3-O-(2,3-di-O-acetyl-α-l-arabinofuranosyl)-(1→3)-[α-l-rhamnopyranosyl(1→2)]-β-l-arabinopyranoside and hederagenin 3-O-(3-O-acetyl-α-l-arabinofuranosyl)-(1→3)-[α-l-rhamnopyranosyl-(1→2)]-β-l-arabinopyranoside, respectively. All these isolates were evaluated for inhibitory activities of FAS, which showed these isolates had inhibitory activity against FAS with IC₅₀ values ranging from 6.69 to 204.40 μM, comparable to the known FAS inhibitor EGCG (IC₅₀ = 51.97 μM). The study indicates that the hulls of Nephelium lappaceum L. could be considered as potential sources of promising FAS inhibitors and the oleane-type triterpene oligoglycosides could be considered as another type of natural FAS inhibitors.     

棕色棉与白色棉缩合单宁单体儿茶素动态变化的比较

以棕色棉ANL-1’和白色棉‘泗棉3号’为材料,利用HPLc检测棉纤维发育过程中儿茶素的动态变化,结果表明：棉种皮中的儿茶素含量高于棉纤维中的,各种儿茶素单体（EGC、C、EC、EGCG、GCG、ECG、cG）的含量在花后30d迅速下降,其中在白色棉纤维中的下降幅度最大;棕色棉和白色棉发育期棉纤维中儿茶素存在很大差异,如棕色棉纤维中有Ec、CG,但在白色棉纤维中却没有发现。初步推断棕色棉与白色棉纤维中缩合单宁结构有较大不同,可能导致棉纤维颜色发生差异。     

Inhibition of melanoma growth and metastasis by combination with (-)-epigallocatechin-3-gallate and dacarbazine in mice.

(-)-Epigallocatechin-3-gallate (EGCG), a major polyphenol in green tea, was shown to have cancer chemopreventive activity. In this study, we examined the antimetastatic effects of EGCG or the combination of EGCG and dacarbazine on B16-F3m melanoma cells in vitro and in vivo. First, the antimetastatic potentials of five green tea catechins were examined by soft agar colony formation assay, and the results show that EGCG was more effective than the other catechins in inhibiting soft agar colony formation. Second, EGCG dose-dependently inhibited B16-F3m cell migration and invasion by in vitro Transwell assay. Third, EGCG significantly inhibited the spread of B16-F3m cells on fibronectin, laminin, collagen, and Matrigel in a dose-dependent manner. In addition, EGCG significantly inhibited the tyrosine phosphorylation of focal adhesion kinase (FAK) and the activity of matrix metalloproteinase-9 (MMP-9). In animal experiments, EGCG alone reduced lung metastases in mice bearing B16-F3m melanomas. However, a combination of EGCG and dacarbazine was more effective than EGCG alone in reducing the number of pulmonary metastases and primary tumor growths, and increased the survival rate of melanoma-bearing mice. These results demonstrate that combination treatment with EGCG and dacarbazine strongly inhibits melanoma growth and metastasis, and the action mechanisms of EGCG are associated with the inhibition of cell spreading, cell-extracellular matrix and cell-cell interactions, MMP-9 and FAK activities.     

Effects of pH and metal ions on antioxidative activities of catechins

The Effects of pH on antioxidative activities of catechol, pyrogallol, and four catechins, and effects of metal ions (Al3+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Fe3+, K+, Mg2+, Mn2+, Na+, and Zn2+) on antioxidative activities of (-)-epigallocatechin gallate (EGCG) were studied by an oxygen electrode method. The antioxidative activities of catechins were high and constant at pH 6-12, but decreased in acidic and strong alkaline solutions. Copper(II) ion the most strongly increased the antioxidative activity of EGCG among these metal ions examined, but iron(II) ion largely inhibited the antioxidative activity of EGCG. These effects are discussed considering the formation of metal complexes with catechins and the change in oxidation potentials.     

ESR study on the structure-antioxidant activity relationship of tea catechins and their epimers

The purpose of this study is to examine the relationship between the free radical scavenging activities and the chemical structures of tea catechins ((-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC) and (-)-epicatechin (EC)) and their corresponding epimers ((-)-gallocatechin gallate (GCG), (-)-gallocatechin (GC) and (+)-catechin ((+)-C)). With electron spin resonance (ESR) we investigated their scavenging effects on superoxide anions (O-.2) generated in the irradiated riboflavin system, singlet oxygen(1O2) generated in the photoradiation-hemoporphyrin system, the free radicals generated from 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH) and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical. The results showed that the scavenging effects of galloylated catechins (EGCG and GCG) on the four free radicals were stronger than those of nongalloylated catechins (EGC, GC, EC, (+)-C), and the scavenging effects of EGC and GC were stronger than those of EC and (+)-C. Thus, it is suggested that the presence of the gallate group at the 3 position plays the most important role in their free radical-scavenging abilities and an additional insertion of the hydroxyl group at the 5' position in the B ring also contributes to their scavenging activities. Moreover, the corresponding phenoxyl radicals formed after the reaction with O-.2 were trapped by DMPO and the ESR spectra of DMPO/phenoxyl radical adducts were observed (aN=15.6 G and aHbeta=21.5 G). No significant differences were found between the scavenging effects of the catechins and their epimers when their concentrations were high. However, significant differences were observed at relatively low concentrations, and the lower their concentrations, the higher the differences. The scavenging abilities of GCG, GC and (+)-C were stronger than those of their corresponding epimers (EGCG, EGC and EC). The differences between their sterical structures played a more important role in their abilities to scavenge large free radicals, such as the free radicals generated from AAPH and the DPPH radical, than to scavenge small free radicals, such as O-.2 and 1O2, especially in the case with EGCG and GCG with more bulky steric hindrance.     

Low concentration of condensed tannins from catechu significantly inhibits fatty acid synthase and growth of MCF-7 cells

Tannins exist widely in plants, but because they precipitate proteins, scientists frequently ignore them in search of bioactive components. Catechu, a traditional astringent, is rich in tannins. In this study, we found that condensed tannins from catechu potently inhibited animal fatty acid synthase (FAS). Among them, trimeric condensed tannin showed the most potent inhibition with IC₅₀ of 0.47 μg/ml and it also exhibited strong time-dependent inhibition. Its inhibitory kinetics and reacting sites on FAS were obviously different from the known inhibitors of FAS. Furthermore, condensed tannins were found to suppress the growth of MCF-7 breast cancer cells, and the effect was related to their activity of FAS inhibition. The inhibition of both FAS activity and MCF-7 growth was exhibited by low concentrations of condensed tannins without FAS being precipitated. These results suggest tannins would be a valuable resource of bioactive substances.     

Complex effects of different green tea catechins on human platelets

Epigallocatechin gallate (EGCG), a major component of green tea, has been previously shown to inhibit platelet aggregation. The effects of other green tea catechins on platelet function are not known. Pre-incubation with EGCG concentration-dependently inhibited thrombin-induced aggregation and phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinases-1/2. In contrast EGCG stimulated tyrosine phosphorylation of platelet proteins, including Syk and SLP-76 but inhibited phosphorylation of focal adhesion kinase. Other catechins did not inhibit platelet aggregation. Interestingly, when EGCG was added to stirred platelets, a tyrosine kinase-dependent stimulation of platelet aggregation was observed. The two other catechins containing a galloyl group in the 3' position (catechin gallate, epicatechin gallate) also stimulated platelet aggregation, while catechins without a galloyl group (catechin, epicatechin) or the catechin with a galloyl group in the 2' position (epigallocatechin) did not.     

Antiproliferative plant and synthetic polyphenolics are specific inhibitors of vertebrate inositol-1,4,5-trisphosphate 3-kinases and inositol polyphosphate multikinase

Inositol-1,4,5-trisphosphate 3-kinases (IP3K) A, B, and C as well as inositol polyphosphate multikinase (IPMK) catalyze the first step in the formation of the higher phosphorylated inositols InsP5 and InsP6 by metabolizing Ins(1,4,5)P3 to Ins(1,3,4,5)P4. In order to clarify the special role of these InsP3 phosphorylating enzymes and of subsequent anabolic inositol phosphate reactions, a search was conducted for potent enzyme inhibitors starting with a fully active IP3K-A catalytic domain. Seven polyphenolic compounds could be identified as potent inhibitors with IC50 < 200 nM (IC50 given): ellagic acid (36 nM), gossypol (58 nM), (-)-epicatechin-3-gallate (94 nM), (-)-epigallocatechin-3-gallate (EGCG, 120 nM), aurintricarboxylic acid (ATA, 150 nM), hypericin (170 nM), and quercetin (180 nM). All inhibitors displayed a mixed-type inhibition with respect to ATP and a non-competitive inhibition with respect to Ins(1,4,5)P3. Examination of these inhibitors toward IP3K-A, -B, and -C and IPMK from mammals revealed that ATA potently inhibits all kinases while the other inhibitors do not markedly affect IPMK but differentially inhibit IP3K isoforms. We identified chlorogenic acid as a specific IPMK inhibitor whereas the flavonoids myricetin, 3',4',7,8-tetrahydroxyflavone and EGCG inhibit preferentially IP3K-A and IP3K-C. Mutagenesis studies revealed that both the calmodulin binding and the ATP [corrected] binding domain in IP3K are involved in inhibitor binding. Their absence in IPMK and the presence of a unique insertion in IPMK were found to be important for selectivity differences from IP3K. The fact that all identified IP3K and IPMK inhibitors have been reported as antiproliferative agents and that IP3Ks or IPMK often are the best binding targets deserves further investigation concerning their antitumor potential.     

Metabolism of green tea catechins by the human small intestine

Numerous studies have shown that green tea polyphenols can be degraded in the colon, and there is abundant knowledge about the metabolites of these substances that appear in urine and plasma after green tea ingestion. However, there is very little information on the extent and nature of intestinal degradation of green tea catechins in humans. Therefore, the aim of this study was to examine in detail the microbial metabolism and chemical stability of these polyphenols in the small intestine using a well-established ex vivo model. For this purpose, fresh ileostomy fluids from two probands were incubated for 24 h under anaerobic conditions with (+)-catechin (C), (-)-epicatechin (EC), (-)-epicatechin 3-O-gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatchin 3-O-gallate (EGCG) and gallic acid (GA). After lyophilisation and extraction, metabolites were separated, identified and quantified by high performance liquid chromatography-photodiode array detection (HPLC-DAD) and HPLC-ESI-tandem mass spectrometry. Two metabolites of EC and C (3', 4', 5'-trihydroxyphenyl-γ-valerolactone and 3', 4'-dihydroxyphenyl-γ-valerolactone) were identified. In addition, 3', 4', 5'-trihydroxyphenyl-γ-valerolactone was detected as a metabolite of EGC, and (after 24-h incubation) pyrogallol as a degradation product of GA. Cleavage of the GA esters of EGCG and ECG was also observed, with variations dependent on the sources (probands) of the ileal fluids, which differed substantially microbiotically. The results provide new information about the degradation of green tea catechins in the gastrointestinal tract, notably that microbiota-dependent liberation of GA esters may occur before these compounds reach the colon.     

Tea catechins inhibit cholesterol oxidation accompanying oxidation of low density lipoprotein in vitro

Endogenous oxidized cholesterols are potent atherogenic agents. Therefore, the antioxidative effects of green tea catechins (GTC) against cholesterol oxidation were examined in an in vitro lipoprotein oxidation system. The antioxidative potency of GTC against copper catalyzed LDL oxidation was in the decreasing order (-)-epigalocatechin gallate (EGCG)=(-)-epicatechin gallate (ECG)>(-)-epicatechin (EC)=(+)-catechin (C)>(-)-epigallocatechin (EGC). Reflecting these activities, both EGCG (74%) and ECG (70%) inhibited the formation of oxidized cholesterol, as well as the decrease of linoleic and arachidonic acids, in copper catalyzed LDL oxidation. The formation of oxidized cholesterol in 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH)-mediated oxidation of rat plasma was also inhibited when the rats were given diets containing 0.5% ECG or EGCG. In addition, EGCG and ECG highly inhibited oxygen consumption and formation of conjugated dienes in AAPH-mediated linoleic acid peroxidative reaction. These two species of catechin also markedly lowered the generation of hydroxyl radical and superoxide anion. Thus, GTC, especially ECG and EGCG, seem to inhibit cholesterol oxidation in LDL by combination of interference with PUFA oxidation, the reduction and scavenging of copper ion, hydroxyl radical generated from peroxidation of PUFA and superoxide anion.     

The impact of the 67kDa laminin receptor on both cell-surface binding and anti-allergic action of tea catechins

Here, we investigated the structure-activity relationship of major green tea catechins and their corresponding epimers on cell-surface binding and inhibitory effect on histamine release. Galloylated catechins; (−)-epigallocatechin-3-O-gallate (EGCG), (−)-gallocatechin-3-O-gallate (GCG), (−)-epicatechin-3-O-gallate (ECG), and (−)-catechin-3-O-gallate (CG) showed the cell-surface binding to the human basophilic KU812 cells by surface plasmon resonance analysis, but their non-galloylated forms did not. Binding activities of pyrogallol-type catechins (EGCG and GCG) were higher than those of catechol-type catechins (ECG and CG). These patterns were also observed in their inhibitory effects on histamine release. Previously, we have reported that biological activities of EGCG are mediated through the binding to the cell-surface 67 kDa laminin receptor (67LR). Downregulation of 67LR expression caused a reduction of both activities of galloylated catechins. These results suggest that both the galloyl moiety and the B-ring hydroxylation pattern contribute to the exertion of biological activities of tea catechins and their 67LR-dependencies.     

Catechin conjugated with fatty acid inhibits DNA polymerase and angiogenesis

Catechins in green tea have anticancer and antiangiogenesis activities, with epigallocatechin-3-gallate (EGCG) being the most potent antiangiogenic tea catechin. This study examined whether chemical modification of catechin enhanced anticancer and antiangiogenic effects. Catechin, conjugated with fatty acid (acyl-catechin), strongly inhibited DNA polymerase, HL-60 cancer cell growth, and angiogenesis. Catechin conjugated with stearic acid [(2R,3S)-3',4',5,7-tetrahydroxyflavan-3-yl octadecanoate; catechin-C18] was the strongest inhibitor in DNA polymerase alpha and beta and angiogenesis assays. Catechin-C18 also suppressed human endothelial cell (HUVEC) tube formation on the reconstituted basement membrane, suggesting that it affected not only DNA polymerases but also signal transduction pathways in HUVECs. These data indicate that acyl-catechins target both DNA polymerases and angiogenesis as anticancer agents. These results suggest that acylation of catechin is an effective chemical modification to improve the anticancer activity of catechin.     

Epigenetic and genetic mechanisms contribute to telomerase inhibition by EGCG

The ends of human chromosomes are protected from the degradation associated with cell division by 15-20 kb long segments of hexameric repeats of 5'-TTAGGG-3' termed telomeres. In normal cells telomeres lose up to 300 bp of DNA per cell division that ultimately leads to senescence; however, most cancer cells bypass this lifespan restriction through the expression of telomerase. hTERT, the catalytic subunit essential for the proper function of telomerase, has been shown to be expressed in approximately 90% of all cancers. In this study we investigated the hTERT inhibiting effects of (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol found in green tea catechins, in MCF-7 breast cancers cells and HL60 promyelocytic leukemia cells. Exposure to EGCG reduced cellular proliferation and induced apoptosis in both MCF-7 and HL60 cells in vitro, although hTERT mRNA expression was decreased only in MCF-7 cells when treated with EGCG. Furthermore, down-regulation of hTERT gene expression in MCF-7 cells appeared to be largely due to epigenetic alterations. Treatment of MCF-7 cells with EGCG resulted in a time-dependent decrease in hTERT promoter methylation and ablated histone H3 Lys9 acetylation. In conjunction with demethylation, further analysis showed an increase in hTERT repressor E2F-1 binding at the promoter. From these findings, we propose that EGCG is effective in causing cell death in both MCF-7 and HL60 cancer cell lines and may work through different pathways involving both anti-oxidant effects and epigenetic modulation.