title: Epigallocatechin-3-gallate inhibits epidermal growth factor receptor signaling pathway. Evidence for direct inhibition of ERK1/2 and AKT kinases.
abstract: Epidermal growth factor receptor (EGFR) activation is absolutely required for cervical cell proliferation. This suggests that EGFR-inhibitory agents may be of therapeutic value. In the present study, we investigated the effects of epigallocatechin-3-gallate (EGCG), a bioactive green tea polyphenol, on EGFR signaling in cervical cells. EGCG inhibits epidermal growth factor-dependent activation of EGFR, and EGFR-dependent activation of the mitogen-activated protein kinases ERK1/2. EGCG also inhibits EGFR-dependent AKT activity. The EGCG-dependent reduction in ERK and AKT activity is associated with reduced phosphorylation of downstream substrates, including p90RSK, FKHR, and BAD. These changes are associated with increased p53, p21(WAF-1), and p27(KIP-1) levels, reduced cyclin E level, and reduced CDK2 kinase activity. Consistent with these findings, flow cytometry and TUNEL (terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling) staining revealed EGCG-dependent G(1) arrest. Moreover, sustained EGCG treatment caused apoptotic cell death. In addition to inhibiting EGFR, cell-free studies demonstrated that EGCG directly inhibits ERK1/2 and AKT, suggesting that EGCG acts simultaneously at multiple levels to inhibit EGF-dependent signaling. Importantly, the EGCG inhibition is selective, as EGCG does not effect the EGFR-dependent activation of JNK. These results suggest that EGCG acts to selectively inhibit multiple EGF-dependent kinases to inhibit cell proliferation.
authors.affiliation: Department of Environmental Health Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Jerome F
authors.initials: JF
authors.lastname: Sah
authors.forename: Sivaprakasam
authors.initials: S
authors.lastname: Balasubramanian
authors.forename: Richard L
authors.initials: RL
authors.lastname: Eckert
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Rorke
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D002455:Cell Division; D045744:Cell Line, Tumor; D019927:Cyclin E / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D005434:Flow Cytometry; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010636:Phenols / Q000494:pharmacology; D010766:Phosphorylation; D059808:Polyphenols; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015398:Signal Transduction; D013662:Tea; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy / Q000201:enzymology; D051025:bcl-Associated Death Protein
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C494819:BAD protein, human; C493956:CDKN1A protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; C085126:FOXO1 protein, human; D005419:Flavonoids; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D010636:Phenols; D059808:Polyphenols; D011518:Proto-Oncogene Proteins; D013662:Tea; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051025:bcl-Associated Death Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; D002392:Catechin; C045651:epigallocatechin gallate; D066246:ErbB Receptors; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases