MADISON, Wis.--Oral infusion of green tea polyphenols has been shown to inhibit development and progression of prostate cancer in transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Evidence has indicated elevated levels of insulin-like growth factor (IGF)-I with concomitant lowering of IGF binding protein (IGFBP)-3 are associated with increased risk for prostate cancer development and progression. In a current study, published in the December issue of Cancer Research (64, 8715-22, 2004) (http://cancerres.aacrjournals.org), scientists examined the role of IGF/IGFBP-3 signaling and its downstream and other associated events during chemoprevention of prostate cancer by green tea polyphenols in TRAMP mice.
Continuous green tea polyphenol delivery (infusion refers to the actual green tea mixture) for 24 weeks resulted in a substantial reduction in IGF-I levels and a significant increase in the levels of IGFBP-3 in the dorso-lateral prostate. This modulation of IGF/IGFBP-3 was found to be associated with an inhibition of protein expression of phosphatidylinositol 3'-kinase, phosphorylated forms of Akt (Thr-308) and extracellular signal-regulated kinase 1/2. Furthermore, green tea polyphenol administration resulted in marked inhibition of markers of angiogenesis and metastasis most notably vascular endothelial growth factor, urokinase plasminogen activator, and matrix metalloproteinases 2 and 9.
The researchers concluded the IGF-I/IGFBP-3 signaling pathway is a prime pathway for green tea polyphenol-mediated inhibition of prostate cancer, limiting the progression of cancer through inhibition of angiogenesis and metastasis.
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