(-)-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.
Department of Food Science and Technology, The Ohio State University, Columbus, Ohio 43210, USA.
Yanyan
Y
Li
Tao
T
Zhang
Yiqun
Y
Jiang
Hsiu-Fang
HF
Lee
Steven J
SJ
Schwartz
Duxin
D
Sun
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