Green tea polyphenols thwart prostate cancer development at multiple levels

December 01, 2004

PHILADELPHIA - The polyphenols present in green tea help prevent the spread of prostate cancer by targeting molecular pathways that shut down the proliferation and spread of tumor cells, as well as inhibiting the growth of tumor nurturing blood vessels, according to research published in the December 1 issue of Cancer Research.

A team of researchers from the University of Wisconsin, Madison, Wis., and Case Western Reserve University, Cleveland, Ohio, documented the role of green tea polyphenols (GTP) in modulating the insulin-like growth factor-1 (IGF-1)-driven molecular pathway in prostate tumor cells in a mouse model for human prostate cancer.

"Consumption of GTP led to reduced levels of IGF-1," said Hasan Mukhtar, Ph.D., Department of Dermatology at the University of Wisconsin, the senior author of the paper.

"GTP also led to increased levels of one of the binding proteins for IGF-1, the insulin growth factor binding protein-3. These observations bear significance in light of studies that indicate increased levels of IGF-1 are associated with increased risk of several cancers, such as prostate, breast, lung and colon."

GTP modulation of cell growth via the IGF-1 axis coincides with limited production or phosphorylation of key cell survival proteins, including PI3K, Akt and Erk1/2, the research indicated. The PI3K molecular pathway in cells, which includes Akt and Erk1/2, works to promote cell survival, rather than programmed cell death, also known as apoptosis.

GTP also caused reduced expression of proteins known to be associated with the metastatic spread of cancer cells. GTP inhibited the levels of urokinase plasminogen activator as well as matrix metalloproteinases 2 and 9, cellular molecules linked to the metastasis.

The green tea polyphenols contributed to minimizing tumor development by governing the amount of vascular endothelial growth factor (VEGF) in the serum of the prostate cancer mouse model. The reduction of VEGF may result from GTP-induced suppression of IGF-1 levels. VEGF functions to recruit and develop new blood vessels that carry nutrients to developing tumors. By reducing the amount of VEGF, GTP works to minimize nutrients flowing to and supporting tumor growth.

Mukhtar's colleagues contributing to the study included Vaqar Mustafa Adhami, Imtiaz Ahmad Siddiqui, and Nihal Ahmad from the University of Wisconsin; and Sanjay Gupta from Case Western Reserve University.
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Founded in 1907, the American Association for Cancer Research is a professional society of more than 24,000 laboratory, translational, and clinical scientists engaged in all areas of cancer research in the United States and in more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. AACR's Annual Meetings attract more than 15,000 participants who share new and significant discoveries in the cancer field. Specialty meetings, held throughout the year, focus on the latest developments in all areas of cancer research.

American Association for Cancer Research

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