In Vivo Reversal of P-Glycoprotein-Mediated Drug Resistance in a Breast Cancer Xenograft and in Leukemia Models Using a Novel, Potent, and Nontoxic Epicatechin EC31.

The modulation of P-glycoprotein (P-gp, ABCB1) can reverse multidrug resistance (MDR) and potentiate the efficacy of anticancer drugs. Tea polyphenols, such as epigallocatechin gallate (EGCG), have low P-gp-modulating activity, with an EC50 over 10 µM. In this study, we optimized a series of tea polyphenol derivatives and demonstrated that epicatechin EC31 was a potent and nontoxic P-gp inhibitor. Its EC50 for reversing paclitaxel, doxorubicin, and vincristine resistance in three P-gp-overexpressing cell lines ranged from 37 to 249 nM. Mechanistic studies revealed that EC31 restored intracellular drug accumulation by inhibiting P-gp-mediated drug efflux. It did not downregulate the plasma membrane P-gp level nor inhibit P-gp ATPase. It was not a transport substrate of P-gp. A pharmacokinetic study revealed that the intraperitoneal administration of 30 mg/kg of EC31 could achieve a plasma concentration above its in vitro EC50 (94 nM) for more than 18 h. It did not affect the pharmacokinetic profile of coadministered paclitaxel. In the xenograft model of the P-gp-overexpressing LCC6MDR cell line, EC31 reversed P-gp-mediated paclitaxel resistance and inhibited tumor growth by 27.4 to 36.1% (p < 0.001). Moreover, it also increased the intratumor paclitaxel level in the LCC6MDR xenograft by 6 fold (p < 0.001). In both murine leukemia P388ADR and human leukemia K562/P-gp mice models, the cotreatment of EC31 and doxorubicin significantly prolonged the survival of the mice (p < 0.001 and p < 0.01) as compared to the doxorubicin alone group, respectively. Our results suggested that EC31 was a promising candidate for further investigation on combination therapy for treating P-gp-overexpressing cancers.

An In-Silico, In-Vitro and In-Vivo Combined Approach to Identify NMNATs as Potential Protein Targets of ProEGCG for Treatment of Endometriosis.

Endometriosis is defined as endometrial tissues found outside the uterine cavity. ProEGCG is a prodrug of Epigallocatechin gallate (EGCG), a potent polyphenol found in green tea. It inhibits the development of endometriotic lesions of mouse model in vivo, with higher efficacy and more remarkable anti-oxidative ability than EGCG. Our study aims to identify the molecular binding targets and pharmacological actions of ProEGCG in treating endometriosis. Protein target interaction study is essential to fully characterize the mechanism of actions, related therapeutic effects, and side effects. We employed a combined approach, starting with an in silico reverse screening of protein targets and molecular docking, followed by in vitro cellular thermal shift assay (CESTA) to assess the stability of protein-small molecule complexes. Then microarray and immunostaining of endometriotic lesions in mice in vivo confirmed the molecular interaction of the selected targets after treatment. Our study identified enzymes nicotinamide nucleotide adenylyltransferase (NMNAT)1 and NMNAT3 as protein targets of ProEGCG in silico and in vitro and were overexpressed after ProEGCG treatment in vivo. These findings suggested that participation in nicotinate and nicotinamide metabolism potentially regulated the redox status of endometriosis via its antioxidative capacities through binding to the potential therapeutic targets of ProEGCG.

Dibenzoate esters of cis-tetralin-2,3-diol as analogs of (-)-epigallocatechin gallate: synthesis and crystal structure of anticancer drug candidates.

(-)-Epigallocatechin gallate (EGCG), the main component of green tea extract, displays multiple biological activities. However, it cannot be used as a drug due to its low cellular absorption, instability and metabolic degradation. Therefore, there is a need to provide analogs that can overcome the limitations of EGCG. In this work, six synthetic analogs of EGCG sharing a common tetralindiol dibenzoate core were synthesized and fully characterized by 1H NMR, 13C NMR, HRMS and IR spectroscopies, and X-ray crystallography. These are (2R,3S)-1,2,3,4-tetrahydronaphthalene-2,3-diyl bis[3,4,5-tris(benzyloxy)benzoate], C66H56O10, and the analogous esters bis(3,4,5-trimethoxybenzoate), C30H32O10, bis(3,4,5-trifluorobenzoate), C24H14F6O4, bis[4-(benzyloxy)benzoate], C38H32O6, bis(4-methoxybenzoate), C26H24O6, and bis(2,4,6-trifluorobenzoate), C24H14F6O4. Structural analysis revealed that the molecular shapes of these dibenzoate esters of tetralindiol are significantly different from that of previously reported dimandelate esters or monobenzoate esters, as the acid moieties extend far from the bicyclic system without folding back over the tetralin fragment. Compounds with small fluorine substituents take a V-shape, whereas larger methoxy and benzyloxy groups determine the formation of an L-shape or a cavity. Intermolecular interactions are dominated by π-π stacking and C-H...π interactions involving the arene rings in the benzoate fragment and the arene ring in the tetrahydronaphthalene moiety. All six crystal structures are determined in centrosymmetric space groups (either P-1, P21/n, C2/c or I2/a).

Therapeutic potential of a novel prodrug of green tea extract in induction of apoptosis via ERK/JNK and Akt signaling pathway in human endometrial cancer.

BACKGROUND: Previous studies have shown a major green tea polyphenol (-)-epigallocatechin-3-gallate ((-)-EGCG) as a powerful anti-cancer agent. However, its poor bioavailability and requirement of a high dosage to manifest activity have restricted its clinical application. Recently, our team synthesized a peracetate-protected derivative of EGCG, which can act as a prodrug of (-)-EGCG (ProEGCG) with enhanced stability and improved bioavailability in vitro and in vivo. Herein, we tested the therapeutic efficacy of this novel ProEGCG, in comparison to EGCG, toward human endometrial cancer (EC). METHODS: In this study, the effects of ProEGCG and EGCG treatments on cell growth, cell survival and modulation of intracellular signaling pathways in RL95-2 and AN3 CA EC cells were compared. The antiproliferative effect was evaluated by cell viability assay. Apoptosis was measured by annexin/propidium iodide staining. Expression of mitogen-activated protein kinases, markers of proliferation and apoptosis were measured by immunoblot analysis. In addition, the effects of ProEGCG and EGCG on tumor growth, vessel formation and gene expression profiles on xenograft models of the EC cells were investigated. RESULTS: We found that treatment with ProEGCG, but not EGCG, inhibited, in a time- and dose-dependent manner, the proliferation and increased apoptosis of EC cells. Treatment with low-dose ProEGCG significantly enhanced phosphorylation of JNK and p38 MAPK and inhibited phosphorylation of Akt and ERK which are critical mediators of apoptosis. ProEGCG, but not EGCG, elicited a significant decrease in the growth of the EC xenografts, promoted apoptotic activity of tumour cells in the EC xenografts, and decreased microvessel formation, by differentially suppressing anti-apoptotic molecules, NOD1 and NAIP. Notably, no obvious adverse effects were detected. CONCLUSIONS: Taken together, ProEGCG at a low dose exhibited anticancer activity in EC cells through its anti-proliferative, pro-apoptotic and anti-tumor actions on endometrial cancer in vitro and in vivo. In contrast, a low dose of EGCG did not bring about similar effects. Importantly, our data demonstrated the efficacy and safety of ProEGCG which manifests the potential of a novel anticancer agent for the management of endometrial cancer.

Bioisosteric investigation of ebselen: Synthesis and in vitro characterization of 1,2-benzisothiazol-3(2H)-one derivatives as potent New Delhi metallo-ß-lactamase inhibitors.

Carbapenem-resistant Enterobacteriaceae (CRE) producing New Delhi metallo-ß-lactamase (NDM-1) cause untreatable bacterial infections, posing a significant threat to human health. In the present study, by employing the concept of bioisosteric replacement of the selenium moiety of ebselen, we have designed, synthesized and characterized a small compound library of 2-substituted 1,2-benzisothiazol-3(2H)-one derivatives and related compounds for evaluating their cytotoxicity and synergistic activity in combination with meropenem against the E. coli Tg1 (NDM-1) strain. The most promising compound 3a demonstrated potent synergistic activity against a panel of clinically isolated NDM-1 positive CRE strains with FICI as low as 0.09. Moreover, its IC50 value and inhibition mechanism were also confirmed by using the enzyme inhibition assay and the ESI-MS analysis respectively. Importantly, compound 3a has acceptable toxicity and is not a PAINS. Because of its structural simplicity and potent synergistic activity in combination with meropenem, we propose that compound 3a may be a promising meropenem adjuvant and a new series of such compounds may worth further investigations.

Targeting the DNA Repair Endonuclease ERCC1-XPF with Green Tea Polyphenol Epigallocatechin-3-Gallate (EGCG) and Its Prodrug to Enhance Cisplatin Efficacy in Human Cancer Cells.

The 5'-3' structure-specific endonuclease ERCC1/XPF (Excision Repair Cross-Complementation Group 1/Xeroderma Pigmentosum group F) plays critical roles in the repair of cisplatin-induced DNA damage. As such, it has been identified as a potential pharmacological target for enhancing clinical response to platinum-based chemotherapy. The goal of this study was to follow up on our previous identification of the compound NSC143099 as a potent inhibitor of ERCC1/XPF activity by performing an in silico screen to identify structural analogues that could inhibit ERCC1/XPF activity in vitro and in vivo. Using a fluorescence-based DNA-endonuclease incision assay, we identified the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) as a potent inhibitor of ERCC1/XPF activity with an IC50 (half maximal inhibitory concentration) in the nanomolar range in biochemical assays. Using DNA repair assays and clonogenic survival assays, we show that EGCG can inhibit DNA repair and enhance cisplatin sensitivity in human cancer cells. Finally, we show that a prodrug of EGCG, Pro-EGCG (EGCG octaacetate), can enhance response to platinum-based chemotherapy in vivo. Together these data support a novel target of EGCG in cancer cells, namely ERCC1/XPF. Our studies also corroborate previous observations that EGCG enhances sensitivity to cisplatin in multiple cancer types. Thus, EGCG or its prodrug makes an ideal candidate for further pharmacological development with the goal of enhancing cisplatin response in human tumors.

Investigation of synergistic antimicrobial effects of the drug combinations of meropenem and 1,2-benzisoselenazol-3(2H)-one derivatives on carbapenem-resistant Enterobacteriaceae producing NDM-1.

The worldwide prevalence of NDM-1-producing bacteria has drastically undermined the clinical efficacy of the last line antibiotic of carbapenems, prompting a need to devise effective strategy to preserve their clinical value. Our previous studies have shown that ebselen can restore the efficacy of meropenem against a laboratory strain that produces NDM-1. Here we report the construction of a focused compound library of 1,2-benzisoselenazol-3(2H)-one derivatives which comprise a total of forty-six candidate compounds. The structure-activity relationship of these compounds and their potential to serve as an adjuvant to enhance the antimicrobial efficacy of meropenem against a collection of clinical NDM-1-producing carbapenem-resistant Enterobacteriaceae isolates was examined. Drug combination assays indicated that these derivatives exhibited synergistic antimicrobial activity when used along with meropenem, effectively restoring the activity of carbapenems against the resistant strains tested in a Galleria mellonella larvae in vivo infection model. The mode of inhibition of one compound, namely 11_a38, which was depicted when tested on the purified NDM-1 enzyme, indicated that it could covalently bind to the enzyme and displaced one zinc ion from the active site. Overall, this study provides a novel 1,2-benzisoselenazol-3(2H)-one scaffold that exhibits strong synergistic antimicrobial activity with carbapenems, and low cytotoxicity. The prospect of application of such compounds as carbapenem adjuvants warrants further evaluation.

Perspectives on the recent developments with green tea polyphenols in drug discovery.

INTRODUCTION: Increasing evidence has expanded the role of green tea from a traditional beverage to a source of pharmacologically active molecules with diverse health benefits. However, conclusive clinical results are needed to better elucidate the cancer-preventive and therapeutic effects of green tea polyphenols (GTPs). Areas covered: The authors describe GTPs' chemical compositions and metabolic biotransformations, and their recent developments in drug discovery, focusing on their cancer chemopreventive and therapeutic effects. They then review the recent development of GTP-loaded nanoparticles and GTP prodrugs. Expert opinion: GTPs possess potent anticarcinogenic activities through interfering with the initiation, development and progression phases of cancer. There are several challenges (e.g. poor bioavailability) in developing GTPs as therapeutic agents. Use of nanoparticle-based delivery systems has provided unique advantages over purified GTPs. However, there is still a need to determine the actual magnitude and pharmacological mechanisms of GTPs encapsulated in nanoparticles, in order to address newly emerging safety issues associated with the potential 'local overdose' effect. The use of Pro- epigallocatechin gallate (Pro-EGCG) as a prodrug appears to offer improved in vitro stability as well as better in vivo bioavailability and efficacies in a number of animal studies, suggesting its potential as a therapeutic agent for further study and development.

A prodrug of green tea polyphenol (-)-epigallocatechin-3-gallate (Pro-EGCG) serves as a novel angiogenesis inhibitor in endometrial cancer.

Anti-angiogenesis effect of a prodrug of green tea polyphenol (-)-epigallocatechin-3-gallate (Pro-EGCG) in malignant tumors is not well studied. Here, we investigated how the treatment with Pro-EGCG inhibited tumor angiogenesis in endometrial cancer. Tumor xenografts of human endometrial cancer were established and subjected to microarray analysis after Pro-EGCG treatment. First, we showed Pro-EGCG inhibited tumor angiogenesis in xenograft models through down-regulation of vascular endothelial growth factor A (VEGFA) and hypoxia inducible factor 1 alpha (HIF1α) in tumor cells and chemokine (C-X-C motif) ligand 12 (CXCL12) in host stroma by immunohistochemical staining. Next, we investigated how HIF1α/VEGFA was down-regulated and how the reduction of CXCL12 inhibited tumor angiogenesis. We found that VEGFA secretion from endometrial cancer cells was decreased by Pro-EGCG treatment through inhibiting PI3K/AKT/mTOR/HIF1α pathway. Furthermore, the down-regulation of CXCL12 in stromal cells by Pro-EGCG treatment restricted migration and differentiation of macrophages thereby inhibited infiltration of VEGFA-expressing tumor-associated macrophages (TAMs). Taken together, we demonstrated that treatment with Pro-EGCG not only decreases cancer cell-secreted VEGFA but also inhibits TAM-secreted VEGFA in endometrial cancer. These findings demonstrate that Pro-EGCG is a novel angiogenesis inhibitor for endometrial cancer.

Biological and Mechanistic Characterization of Novel Prodrugs of Green Tea Polyphenol Epigallocatechin Gallate Analogs in Human Leiomyoma Cell Lines.

Uterine fibroids (leiomyomas) are very common benign tumors grown on the smooth muscle layer of the uterus, present in up to 75% of reproductive-age women and causing significant morbidity in a subset of this population. Although the etiology and biology of uterine fibroids are unclear, strong evidence supports that cell proliferation, angiogenesis and fibrosis are involved in their formation and growth. Currently the only cure for uterine fibroids is hysterectomy; the available alternative therapies have limitations. Thus, there is an urgent need for developing a novel strategy for treating this condition. The green tea polyphenol epigallocatechin gallate (EGCG) inhibits the growth of uterine leiomyoma cells in vitro and in vivo, and the use of a green tea extract (containing 45% EGCG) has demonstrated clinical activity without side effects in women with symptomatic uterine fibroids. However, EGCG has a number of shortcomings, including low stability, poor bioavailability, and high metabolic transformations under physiological conditions, presenting challenges for its development as a therapeutic agent. We developed a prodrug of EGCG (Pro-EGCG or 1) which shows increased stability, bioavailability and biological activity in vivo as compared to EGCG. We also synthesized prodrugs of EGCG analogs, compounds 2a and 4a, in order to potentially reduce their susceptibility to methylation/inhibition by catechol-O-methyltransferase. Here, we determined the effect of EGCG, Pro-EGCG, and 2a and 4a on cultured human uterine leiomyoma cells, and found that 2a and 4a have potent antiproliferative, antiangiogenic, and antifibrotic activities. J. Cell. Biochem. 117: 2357-2369, 2016. © 2016 Wiley Periodicals, Inc.

Identification of a new class of FtsZ inhibitors by structure-based design and in vitro screening.

The Filamenting temperature-sensitive mutant Z (FtsZ), an essential GTPase in bacterial cell division, is highly conserved among Gram-positive and Gram-negative bacteria and thus considered an attractive target to treat antibiotic-resistant bacterial infections. In this study, a new class of FtsZ inhibitors bearing the pyrimidine-quinuclidine scaffold was identified from structure-based virtual screening of natural product libraries. Iterative rounds of in silico studies and biological evaluation established the preliminary structure-activity relationships of the new compounds. Potent FtsZ inhibitors with low micromolar IC50 and antibacterial activity against S. aureus and E. coli were found. These findings support the use of virtual screening and structure-based design for the rational development of new antibacterial agents with innovative mechanisms of action.

Prodrug of green tea epigallocatechin-3-gallate (Pro-EGCG) as a potent anti-angiogenesis agent for endometriosis in mice.

Green tea epigallocatechin-3-gallate (EGCG) can inhibit angiogenesis and development of an experimental endometriosis model in mice, but it suffers from poor bioavailability. A prodrug of EGCG (pro-EGCG, EGCG octaacetate) is utilized to enhance the stability and bioavailability of EGCG in vivo. In this study, the potential of pro-EGCG as a potent anti-angiogenesis agent for endometriosis in mice was investigated. Homologous endometrium was subcutaneously transplanted into mice to receive either saline, vitamin E, EGCG or pro-EGCG treatment for 4 weeks. The growth of the endometrial implants were monitored by IVIS(®) non-invasive in vivo imaging during the interventions. Angiogenesis of the endometriotic lesions was determined by Cellvizio(®) in vivo imaging and SCANCO(®) Microfil microtomography. The bioavailability, anti-oxidation and anti-angiogenesis capacities of the treatments were measured in plasma and lesions. The implants with adjacent outer subcutaneous and inner abdominal muscle layers were collected for histological, microvessel and apoptosis examinations. The result showed that EGCG and pro-EGCG significantly decreased the growth of endometrial implants from the 2nd week to the 4th week of intervention. EGCG and pro-EGCG significantly reduced the lesion size and weight, inhibited functional and structural microvessels in the lesions, and enhanced lesion apoptosis at the end of interventions. The inhibition by pro-EGCG in all the angiogenesis parameters was significantly greater than that by EGCG, and pro-EGCG also had better bioavailability and greater anti-oxidation and anti-angiogenesis capacities than EGCG. Ovarian follicles and uterine endometrial glands were not affected by either EGCG or pro-EGCG. Vitamin E had no effect on endometriosis. In conclusion, pro-EGCG significantly inhibited the development, growth and angiogenesis of experimental endometriosis in mice with high efficacy, bioavailability, anti-oxidation and anti-angiogenesis capacities. Pro-EGCG could be a potent anti-angiogenesis agent for endometriosis.

Recent advances on tea polyphenols.

Over the past decade many scientific and medical studies have focused on green tea for its long-purported health benefits. There is convincing evidence that tea is a cup of life. It has multiple preventive and therapeutic effects. This review thus focuses on the recent advances of tea polyphenols and their applications in the prevention and treatment of human cancers. Of the various polyphenols in tea, (-)-Epigallocatechin-3-gallate (EGCG) is the most abundant, and active compound studied in tea research. EGCG inhibits several molecular targets to inhibit cancer initiation and modulates several essential survival pathways to block cancer progression. Herein, we describe the various mechanisms of action of EGCG and also discuss previous and current ongoing clinical trials of EGCG and green tea polyphenols in different cancer types.

EGCG, green tea polyphenols and their synthetic analogs and prodrugs for human cancer prevention and treatment.

Cancer-preventive effects of tea polyphenols, especially epigallocatechin-3-gallate (EGCG), have been demonstrated by epidemiological, preclinical, and clinical studies. Green tea polyphenols such as EGCG have the potential to affect multiple biological pathways, including gene expression, growth factor-mediated pathways, the mitogen-activated protein kinase-dependent pathway, and the ubiquitin/proteasome degradation pathway. Therefore, identification of the molecular targets of EGCG should greatly facilitate a better understanding of the mechanisms underlying its anticancer and cancer-preventive activities. Performing structure-activity relationship (SAR) studies could also greatly enhance the discovery of novel tea polyphenol analogs as potential anticancer and cancer-preventive agents. In this chapter, we review the relevant literature as it relates to the effects of natural and synthetic green tea polyphenols and EGCG analogs on human cancer cells and their potential molecular targets as well as their antitumor effects. We also discuss the implications of green tea polyphenols in cancer prevention.

Evaluation of curcumin acetates and amino acid conjugates as proteasome inhibitors.

Curcumin (diferuloylmethane) is the main active ingredient of turmeric, a traditional herbal medicine and food of south Asia. Curcumin has been found to have a wide range of biological activities, including antioxidant, anti-inflammatory, chemopreventive and chemotherapeutic activities. Curcumin is currently being tested in clinical trials for treatment of various types of cancers, including multiple myeloma, pancreatic cancer and colon cancer. Although no toxicity associated with curcumin (even at very high doses) has been observed, the effects of curcumin in other solid tumors have been modest, primarily due to poor water solubility and poor bioavailability in tissues remote from the gastrointestinal tract. Therefore, there is a need for the discovery of curcumin analogs with better water solubility or greater bioavailability for the treatment of solid tumors such as prostate cancer. In this study, curcumin acetates and amino acid conjugates of curcumin were studied in terms of their proteasome inhibitory and antiproliferative effects against several human cancer cell lines. It was found that the water soluble amino acid conjugates of curcumin showed a potent antiproliferative effect and are potent proteasome inhibitors. Docking studies of the curcumin amino acid conjugates for proteasome inhibition were carried out to explain their biological activities. It is suggested that they may serve as the water soluble analogs of curcumin.

Inhibition of catechol-Omicron-methyltransferase activity in human breast cancer cells enhances the biological effect of the green tea polyphenol (-)-EGCG.

Tea is one of the most popular beverages in the world and has been studied extensively as a health-promoting beverage that may act to prevent a number of chronic diseases and cancers. (-)-Epigallocatechin gallate [(-)-EGCG], a major component in green tea, is unstable under physiological conditions and methylation of (-)-EGCG by catechol-Omicron-methyltransferase (COMT) is a modification that reduces the biological activity of (-)-EGCG. In the current study, we hypothesized that suppression of COMT activity in human breast cancer cells could increase the proteasome-inhibitory potency of (-)-EGCG and therefore enhance its tumor cell growth-inhibitory activity. We first determined the COMT genotype and basal levels of COMT activity in various human breast cancer cell lines. Furthermore, when breast cancer MDA-MB-231 cells containing high COMT activity were tested, the diminished COMT activity apparently increased the effectiveness of (-)-EGCG via augmented proteasome inhibition and apoptosis induction. This study supplements the previous findings that methylated (-)-EGCG is less bioactive and supports the notion that COMT inhibition may increase the anti-cancer properties of tea polyphenols and the combination may serve as a novel approach or supplemental treatment for breast cancer chemotherapy.

Celastrol and an EGCG pro-drug exhibit potent chemosensitizing activity in human leukemia cells.

Chemotherapy remains the staple of treatment for many types of leukemia. Despite the positive impact on extending overall survival in patients with hematological malignancies, new treatment strategies are needed to reduce the nonspecific toxicity and improve the efficacy of treatment. Celastrol, derived from the 'Thunder God Vine' and Pro-EGCG, a pre-drug version of green tea polyphenol EGCG have shown potent biological activity in vitro and in vivo. Whether these natural products augment the efficacy of conventional chemotherapy in the treatment of leukemia cells has yet to be demonstrated. Here we demonstrate that these natural products could sensitize the effect of chemotherapy in both K-562 and Jurkat T human leukemia cells. Accordingly, this potent biological activity was associated with increased levels of leukemia cell killing, caspase 3 activation, and poly(ADP-ribose) polymerase cleavage. Furthermore, the higher levels of apoptotic indices were associated with decreased levels of Bcr-Abl oncoprotein in K-562 cells. Taken together, our findings present a compelling rationale for the development of combination strategies using natural products in the treatment of hematological malignancies.

Proteasome inhibition in human breast cancer cells with high catechol-O-methyltransferase activity by green tea polyphenol EGCG analogs.

A pro-drug 8 of a synthetic analog 7 is more active in its antiproliferative activity against human breast cancer MDA-MB-231 cells possessing high catechol-O-methyltransferase (COMT) activity than the pro-drugs of EGCG and the analog 5. The higher activity of 8 is attributed to it not being a substrate of COMT.

Effect of a prodrug of the green tea polyphenol (-)-epigallocatechin-3-gallate on the growth of androgen-independent prostate cancer in vivo.

Epigallocatechin-3-gallate (EGCG) is the major and most potent polyphenol compound of green tea that has been shown to have anticancer effects against various types of cancers. In this study, in addition to the EGCG compound, a synthetic derivative, the peracetate of EGCG (EGCG-P), was used to investigate the inhibitory effects on growth of androgen-independent prostate cancer in vivo. The advantage of EGCG-P is that it may act as a prodrug, leading to higher bioavailability than EGCG itself. The aim of our study was to compare the differences between EGCG and EGCG-P on their inhibitory effect on androgen-independent prostate cancer, CWR22R, xenograft model in nude mice. The mice were administrated daily with solvent dimethyl sulfoxide, EGCG, and EGCG-P separately through intraperitoneal injection for 20 days. Tumor volume and body weight of nude mice were recorded daily. Serum prostate-specific antigen (PSA) levels were also measured before and after the treatment. The effects of both EGCG and EGCG-P on tumor cell proliferation were assessed by immunohistochemical (IHC) method using antibodies against Ki-67 and proliferating cell nuclear antigen. The apoptotic effect was evaluated by IHC against B-cell non-Hodgkin lymphoma-2 and terminal deoxynucleotidyl transferase dUTP nick-end labeling assay by in situ apoptosis detection kit. Moreover, the potential suppression of angiogenesis by EGCG and EGCG-P on prostate cancer was examined by IHC against CD31. Our results revealed that treatment of EGCG and EGCG-P compounds suppressed the growth of CWR22R xenografts without causing any detectable side effects in nude mice. The suppression of growth of the tumor was correlated with the decrease of serum PSA level together with the reduction in tumor angiogenesis and an increase in apoptosis on prostate cancer cells. The results showed that treatment of EGCG and EGCG-P inhibited tumor growth and angiogenesis while promoting apoptosis of the prostate cancer cells in vivo. Our results suggest that EGCG-P may be a more stable and useful compound for increasing the therapeutic anticancer effects in androgen-independent prostate cancer.

A para-amino substituent on the D-ring of green tea polyphenol epigallocatechin-3-gallate as a novel proteasome inhibitor and cancer cell apoptosis inducer.

Analogs of (-)-EGCG containing a para-amino group on the D-ring in place of the hydroxyl groups have been synthesized and their proteasome inhibitory activities were studied. We found that, the O-acetylated (-)-EGCG analogs possessing a p-NH(2) or p-NHBoc (Boc; tert-butoxycarbonyl) D-ring (5 and 7) act as novel tumor cellular proteasome inhibitors and apoptosis inducers with potency similar to natural (-)-EGCG and similar to (-)-EGCG peracetate. These data suggest that the acetylated amino-GTP analogs have the potential to be developed into novel anticancer agents.