Many beneficial properties have been attributed to (À)Àepi-gallocatechin gallate (EGCG), including chemopreventive, anticarcinogenic, and antioxidant actions. In this study, we investigated the effects of EGCG on the function of glucoseregulated protein 78 (GRP78), which is associated with the multidrug resistance phenotype of many types of cancer cells. Our investigation was directed at elucidating the mechanism of the EGCG and GRP78 interaction and providing evidence about whether EGCG modulates the activity of anticancer drugs through the inhibition of GRP78 function. We found that EGCG directly interacted with GRP78 at the ATP-binding site of protein and regulated its function by competing with ATP binding, resulting in the inhibition of ATPase activity. EGCG binding caused the conversion of GRP78 from its active monomer to the inactive dimer and oligomer forms. Further, we showed that EGCG interfered with the formation of the antiapoptotic GRP78-caspase-7 complex, which resulted in an increased etoposide-induced apoptosis in cancer cells. We also showed that EGCG significantly suppressed the transformed phenotype of breast cancer cells treated with etoposide. Overall, these results strongly suggested that EGCG could prevent the antiapoptotic effect of GRP78, which usually suppresses the caspase-mediated cell death pathways in drugtreated cancer cells, contributing to the development of drug resistance. (Cancer Res 2006; 66(18): 9260-9)

Epigallocatechin gallate (EGCG) is the major active polyphenol in green tea. Protein interaction with EGCG is a critical step in the effects of EGCG on the regulation of various key proteins involved in signal transduction. We have identified a novel molecular target of EGCG using affinity chromatography, two-dimensional electrophoresis, and mass spectrometry for protein identification. Spots of interest were identified as the intermediate filament, vimentin. The identification was confirmed by Western blot analysis using an anti-vimentin antibody. Experiments using a pull-down assay with A number of epidemiological studies have shown that the consumption of green tea may protect against many cancer types, including lung, prostate, and breast (1, 2). The inhibition of tumorigenesis by green or black tea preparations was demonstrated in animal models at various organ sites (3-5). The structures of the four major catechins, (Ϫ)-epigallocatechin gallate (EGCG), 1 (Ϫ)-epigallocatechin (EGC), (Ϫ)-epicatechin gallate (ECG), and (Ϫ)-epicatechin (EC), are shown in Fig. 1. EGCG is the major polyphenol in green tea and may account for 50 -80% of the total catechins in tea (4, 6, 7). The inhibitory activity of EGCG against tumorigenesis has been demonstrated. The mechanisms responsible for these cancer-preventive effects of tea are not very well understood but are being intensively investigated.Searching for the EGCG "receptor" or high affinity proteins that bind to EGCG is the first step to understanding the molecular and biochemical mechanisms of the anticancer effects of tea polyphenols. A few proteins that can directly bind with EGCG have been identified, including plasma proteins: fibronectin, fibrinogen, and histidine-rich glycoprotein (8); also fatty acid synthase (Fas) (9), laminin, and the 67-kDa laminin receptor (10, 11). Plasma proteins may act as carrier proteins for EGCG. Fas might trigger the cascade of Fas-mediated apoptosis, and the fact that EGCG can bind and regulate biological functions of the 67 laminin receptor has possible implications for prion-related diseases. However, the biologic and physiologic significance for the anticancer effects of tea polyphenols is not clear. Identification of new proteins binding with EGCG should help in the design of new strategies to prevent cancer.Mass spectrometry-based proteomic analysis is a powerful tool to identify proteins binding with EGCG. We used the JB6 mouse epidermal cell line, a system that has been used extensively as an in vitro model for tumor promotion studies (12), to identify novel proteins that bind with EGCG. The results indicated that EGCG binds with the intermediate filament (IF) protein, vimentin with high affinity (K d ϭ 3.3 nM). Vimentin, one of the type III IF proteins, is a major component of IFs and is expressed during development in a wide range of cells, including mesenchymal cells and in a variety of cultured cell lines and tumors (13,14). IFs are essential for structure and mechanical integration of the cellular space and a variety o...

Fucoidans were isolated by water extraction and ion-exchange chromatography from brown algae Eclonia cava, Sargassum hornery, and Costaria costata collected near of Korean coasts. The structures of fucoidans were investigated. Fucoidan from E. cava was mixture of sulfated rhamnogalactofucan and galactofucan. Fucoidan from C. costata was a sulfated galactofucan. Fucoidan isolated from S. hornery was separated into three fractions: a homofucan sulfate, a homofucan but without sulfate groups, and a sulfated rhamnofucan. The results clearly showed that fucoidans play an inhibitory role in colony formation in human melanoma and colon cancer cells and may be effective antitumor agents.