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

Tetsuya Yamamoto, Hari Digumarthi, Zina Aranbayeva, John Wataha, Jill Lewis, Regina L W Messer, Haiyan Qin, Douglas Dickinson, Tokio Osaki, George S. Schuster, Stephen Hsu

Research output: Contribution to journalReview articlepeer-review

30 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)318-325
Number of pages8
JournalToxicology and Applied Pharmacology
Issue number3
StatePublished - Nov 1 2007


  • EGCG
  • JNK
  • MAPK
  • Oral carcinoma
  • p57/KlP2

ASJC Scopus subject areas

  • Toxicology
  • Pharmacology


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