EGCG inhibits activation of the insulin-like growth factor (IGF)/IGF-1 receptor axis in human hepatocellular carcinoma cells

Abstract The receptor tyrosine kinase (RTK) insulin like growth factor-1 (IGF-1)/IGF-1 receptor (IGF-1R) axis plays an important role in the development of hepatocellular carcinoma (HCC). EGCG inhibits activation of the various types of RTKs and that this is associated with inhibition of multiple do...

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Published in:Cancer letters 2008-04, Vol.262 (1), p.10-18
Main Authors: Shimizu, Masahito, Shirakami, Yohei, Sakai, Hiroyasu, Tatebe, Hideharu, Nakagawa, Takayuki, Hara, Yukihiko, Weinstein, I. Bernard, Moriwaki, Hisataka
Format: Article
Language:English
Subjects:
Carcinoma, Hepatocellular - metabolism
Catechin - analogs & derivatives
Catechin - pharmacology
Cell growth
Cell Line, Tumor
Cell Proliferation - drug effects
Colorectal cancer
EGCG
Hematology, Oncology and Palliative Medicine
Hepatocellular carcinoma
Hepatocytes - metabolism
Humans
IGF-1
IGF-1R
IGF-2
Kinases
Liver cancer
Liver Neoplasms - metabolism
Medical research
Phosphorylation
Receptor, IGF Type 1 - metabolism
Signal Transduction - drug effects
Studies
Tea
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Summary:Abstract The receptor tyrosine kinase (RTK) insulin like growth factor-1 (IGF-1)/IGF-1 receptor (IGF-1R) axis plays an important role in the development of hepatocellular carcinoma (HCC). EGCG inhibits activation of the various types of RTKs and that this is associated with inhibition of multiple downstream signaling pathways. In this study we examined the effects of EGCG on activity of the IGF/IGF-1R axis in HepG2 human HCC cells which express constitutive activation of this axis. The level of phosphorylated ( i.e . activated) form of the IGF-1R protein (p-IGF-1R) was increased in a series of human HCC cell lines when compared with the Hc normal human hepatocytes. EGCG preferentially inhibited growth of HepG2 cells when compared with Hc cells. Treatment of HepG2 cells with EGCG induced apoptosis and caused a decrease in the p-IGF-1R protein and its downstream signaling molecules including the p-ERK, p-Akt, p-Stat-3, and p-GSK-3β proteins, both in the absence or presence of ligand stimulation. EGCG also decreased the levels of both IGF-1 and IGF-2 proteins and mRNAs, but increased the levels of the IGFBP-3 protein. These findings suggest that EGCG can overcome the stimulatory effects of IGFs on the IGF-1R dependent signaling pathway, thus expanding the roles of EGCG as an inhibitor of critical RTKs involved in HCC cell proliferation. These results provide further evidence that EGCG may be useful in the chemoprevention or treatment of liver cancer.
ISSN:0304-3835
1872-7980
DOI:10.1016/j.canlet.2007.11.026