EGCG-targeted p57/KIP2 reduces tumorigenicity of oral carcinoma cells: role of c-Jun N-terminal kinase.

Abstract

The green tea polyphenol epigallocatechin-3-gallate (EGCG) regulates gene expression differentially in tumor and normal cells. In normal human primary epidermal keratinocytes (NHEK), one of the key mediators of EGCG action is p57/KIP2, a cyclin-dependent kinase (CDK) inhibitor. EGCG potently induces p57 in NHEK, but not in epithelial cancer cells. In humans, reduced expression of p57 often is associated with advanced tumors, and tumor cells with inactivated p57 undergo apoptosis when exposed to EGCG. The mechanism of p57 induction by EGCG is not well understood. Here, we show that in NHEK, EGCG-induces p57 via the p38 mitogen-activated protein kinase (MAPK) signaling pathway. In p57-negative tumor cells, JNK signaling mediates EGCG-induced apoptosis, and exogenous expression of p57 suppresses EGCG-induced apoptosis via inhibition of c-Jun N-terminal kinase (JNK). We also found that restoration of p57 expression in tumor cells significantly reduced tumorigenicity in athymic mice. These results suggest that p57 expression may be an useful indicator for the clinical course of cancers, and could be potentially useful as a target for cancer therapies.

• Authors: Tetsuya Yamamoto, Hari Digumarthi, Zina Aranbayeva, John Wataha, Jill Lewis, Regina Messer, Haiyan Qin, Douglas Dickinson, Tokio Osaki, George S Schuster, Stephen Hsu
• Journal: Toxicology and applied pharmacology (Toxicol Appl Pharmacol) Vol. 224 Issue 3 Pg. 318-25 (Nov 01 2007) ISSN: 0041-008X [Print] United States
• PMID: 17196232 (Publication Type: Journal Article)

Chemical References

• Anthracenes
• Cyclin-Dependent Kinase Inhibitor p57
• Enzyme Inhibitors
• Imidazoles
• Pyridines
• bcl-2-Associated X Protein
• pyrazolanthrone
• Catechin
• Cytochromes c
• epigallocatechin gallate
• JNK Mitogen-Activated Protein Kinases
• p38 Mitogen-Activated Protein Kinases
• SB 203580

Topics

• Animals
• Anthracenes (pharmacology)
• Apoptosis (drug effects, physiology)
• Blotting, Western
• Catechin (analogs & derivatives, pharmacology, therapeutic use)
• Cell Line
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Cyclin-Dependent Kinase Inhibitor p57 (genetics, metabolism)
• Cytochromes c (metabolism)
• Disease-Free Survival
• Enzyme Inhibitors (pharmacology)
• Female
• Humans
• Imidazoles (pharmacology)
• JNK Mitogen-Activated Protein Kinases (antagonists & inhibitors, metabolism)
• Mice
• Mice, Nude
• Mouth Neoplasms (enzymology, metabolism, pathology, prevention & control)
• Phosphorylation (drug effects)
• Pyridines (pharmacology)
• Signal Transduction (drug effects, physiology)
• Transfection
• Xenograft Model Antitumor Assays
• bcl-2-Associated X Protein (metabolism)
• p38 Mitogen-Activated Protein Kinases (antagonists & inhibitors, metabolism)