Fyn is a novel target of (-)-epigallocatechin gallate in the inhibition of JB6 Cl41 cell transformation.
The cancer preventive action of (-)-epigallocatechin gallate (EGCG), found in green tea, is strongly supported by epidemiology and laboratory research data. However, the mechanism by which EGCG inhibits carcinogenesis and cell transformation is not clear. In this study, we report that EGCG suppressed epidermal growth factor (EGF)-induced cell transformation in JB6 cells. We also found that EGCG inhibited EGF-induced Fyn kinase activity and phosphorylation in vitro and in vivo. Fyn was implicated in the process because EGF-induced JB6 cell transformation was inhibited by small interfering RNA (siRNA)-Fyn-JB6 cells. With an in vitro protein-binding assay, we found that EGCG directly bound with the GST-Fyn-SH2 domain but not the GST-Fyn-SH3 domain. The K(d) value for EGCG binding to the Fyn SH2 domain was 0.367 +/- 0.122 microM and B(max) was 1.35 +/- 0.128 nmol/mg. Compared with control JB6 Cl41 cells, EGF-induced phosphorylation of p38 MAP kinase (p38 MAPK) (Thr180/Tyr182), ATF-2 (Thr71) and signal transducer and activator of transcription 1 (STAT1) (Thr727) was decreased in siRNA-Fyn-JB6 cells. EGCG could inhibit the phosphorylation of p38 MAPK, ATF-2, and STAT1. The DNA binding ability of AP-1, STAT1, and ATF-2 was also decreased in siRNA-Fyn-JB6 cells. Overall, these results demonstrated that EGCG interacted with Fyn and inhibited Fyn kinase activity and thereby regulated EGF-induced cell transformation. Inhibition of Fyn kinase activity is a novel and important mechanism that may be involved in EGCG-induced inhibition of cell transformation.
He
Zhiwei
Z
Hormel Institute, The University of Minnesota, Austin, Minnesota 55912, USA.
Tang
Faqing
F
Ermakova
Svetlana
S
Li
Ming
M
Zhao
Qing
Q
Cho
Yong-Yeon
YY
Ma
Wei-Ya
WY
Choi
Hong-Seok
HS
Bode
Ann M
AM
Yang
Chung S
CS
Dong
Zigang
Z
D051698:Activating Transcription Factor 2 / Q000037:antagonists & inhibitors; D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D050882:CREB-Binding Protein / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000633:toxicity; D005982:Glutathione Transferase / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
D051698:Activating Transcription Factor 2; D048868:Adaptor Proteins, Signal Transducing; D000975:Antioxidants; C497106:Atf2 protein, mouse; C491468:Fyb protein, mouse; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D018808:Transcription Factor AP-1; D004815:Epidermal Growth Factor; D002392:Catechin; C045651:epigallocatechin gallate; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse; D005982:Glutathione Transferase; D048051:p38 Mitogen-Activated Protein Kinases