Inhibition of PI3K/AKT and MEK/ERK pathways act synergistically to enhance antiangiogenic effects of EGCG through activation of FOXO transcription factor

Sharmila Shankar , Qinghe Chen and Rakesh K Srivastava

Department of Biochemistry, University of Texas Health Science Center at Tyler, Tyler, Texas, 75708-3154, USA

author email corresponding author email

Journal of Molecular Signaling 2008, 3:7doi:10.1186/1750-2187-3-7


Published:	20 March 2008

Abstract

Background

We have recently shown that epigallocatechin-3-gallate (EGCG), a polyphenolic compound from green tea, inhibits angiogenesis. However, the molecular mechanisms by which EGCG inhibits angiogenesis have never been investigated. In this study, we examined the interaction of PI3K/AKT and MEK/ERK pathways on the regulation of FOXO transcription factors, which ultimately control the antiangiogenic effects of EGCG.

Results

Inhibition of PI3K/AKT and MEK/ERK pathways interact synergistically to inhibit migration and capillary tube formation of HUVEC cells and further enhanced the antiangiogenic effects of EGCG. Inhibition of AKT and MEK kinases synergistically induced FOXO transcriptional activity, which was further enhanced in the presence of EGCG. Phosphorylation deficient mutants of FOXO induced FOXO transcriptional activity, inhibited HUVEC cell migration and capillary tube formation. Inhibition of FOXO phosphorylation also enhanced antiangiogenic effects of EGCG through transcriptional activation of FOXO.

Conclusion

Inhibition of PI3K/AKT and MEK/ERK pathways act synergistically to regulate antiangiogenic effects of EGCG through activation of FOXO transcription factors. The activation of FOXO transcription factors through inhibition of these two pathways may have physiological significance in management of diabetic retinopathy, rheumatoid arthritis, psoriasis, cardiovascular diseases, and cancer.