title: (-)-Epigallocatechin gallate downregulates EGF receptor via phosphorylation at Ser1046/1047 by p38 MAPK in colon cancer cells.
abstract: We previously reported that (-)-epigallocatechin gallate (EGCG) in green tea alters plasma membrane organization and causes internalization of epidermal growth factor receptor (EGFR), resulting in the suppression of colon cancer cell growth. In the present study, we investigated the detailed mechanism underlying EGCG-induced downregulation of EGFR in SW480 colon cancer cells. Prolonged exposure to EGCG caused EGFR degradation. However, EGCG required neither an ubiquitin ligase (c-Cbl) binding to EGFR nor a phosphorylation of EGFR at tyrosine residues, both of which are reportedly necessary for EGFR degradation induced by epidermal growth factor. In addition, EGCG induced phosphorylation of p38 mitogen-activated protein kinase (MAPK), a stress-inducible kinase believed to negatively regulate tumorigenesis, and the inhibition of p38 MAPK by SB203580, a specific p38 MAPK inhibitor, or the gene silencing using p38 MAPK-small interfering RNA (siRNA) suppressed the internalization and subsequent degradation of EGFR induced by EGCG. EGFR underwent a gel mobility shift upon treatment with EGCG and this was canceled by SB203580, indicating that EGCG causes EGFR phosphorylation via p38 MAPK. Moreover, EGCG caused phosphorylation of EGFR at Ser1046/1047, a site that is critical for its downregulation and this was also suppressed by SB203580 or siRNA of p38 MAPK. Taken together, our results strongly suggest that phosphorylation of EGFR at serine 1046/1047 via activation of p38 MAPK plays a pivotal role in EGCG-induced downregulation of EGFR in colon cancer cells.
authors: Department of Gastroenterology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan.
authors: Seiji
authors: S
authors: Adachi
authors: Masahito
authors: M
authors: Shimizu
authors: Yohei
authors: Y
authors: Shirakami
authors: Junichi
authors: J
authors: Yamauchi
authors: Hideo
authors: H
authors: Natsume
authors: Rie
authors: R
authors: Matsushima-Nishiwaki
authors: Satoshi
authors: S
authors: To
authors: I Bernard
authors: IB
authors: Weinstein
authors: Hisataka
authors: H
authors: Moriwaki
authors: Osamu
authors: O
authors: Kozawa
mesh_terms: D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D015536:Down-Regulation; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D010766:Phosphorylation; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D012694:Serine / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology*
chemical_list: D016588:Anticarcinogenic Agents; D007093:Imidazoles; D011725:Pyridines; D012694:Serine; D002392:Catechin; C045651:epigallocatechin gallate; D050721:Proto-Oncogene Proteins c-cbl; D066246:ErbB Receptors; D048051:p38 Mitogen-Activated Protein Kinases; C067419:CBL protein, human; C093642:SB 203580