(-)-Epigallocatechin-3-gallate inhibits Hsp90 function by impairing Hsp90 association with cochaperones in pancreatic cancer cell line Mia Paca-2.
(-)-Epigallocatechin-3-gallate [(-)-EGCG], the most abundant polyphenolic catechin in green tea, showed chemoprevention and anticancer activities. (-)-EGCG was reported to bind to the C-terminal domain of heat shock protein 90 (Hsp90). The purpose of this study is to investigate (-)-EGCG as a novel Hsp90 inhibitor to impair Hsp90 superchaperone complex for simultaneous downregulation of oncogenic proteins in pancreatic cancer cells. MTS assay showed that (-)-EGCG exhibited antiproliferative activity against pancreatic cancer cell line Mia Paca-2 in vitro with IC50 below 50 muM. (-)-EGCG increased caspase-3 activity up to 3-fold in a time- and concentration-dependent manner. Western blotting analysis demonstrated that (-)-EGCG induced downregulation of oncogenic Hsp90 client proteins by approximately 70-95%, including Akt, Cdk4, Raf-1, Her-2, and pERK. Co-immunoprecipitation showed that (-)-EGCG decreased the association of cochaperones p23 and Hsc70 with Hsp90 by more than 50%, while it had little effect on the ATP binding to Hsp90. Proteolytic fingerprinting assay confirmed direct binding between (-)-EGCG and the Hsp90 C-terminal domain. These data suggest that the binding of (-)-EGCG to Hsp90 impairs the association of Hsp90 with its cochaperones, thereby inducing degradation of Hsp90 client proteins, resulting antiproliferating effects in pancreatic cancer cells.
Li
Yanyan
Y
Department of Food Science and Technology, The Ohio State University, Columbus, Ohio 43210, USA.
Zhang
Tao
T
Jiang
Yiqun
Y
Lee
Hsiu-Fang
HF
Schwartz
Steven J
SJ
Sun
Duxin
D
D000255:Adenosine Triphosphate / Q000378:metabolism; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050883:HSC70 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology
D016588:Anticarcinogenic Agents; D050883:HSC70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D000255:Adenosine Triphosphate; D002392:Catechin; C045651:epigallocatechin gallate