The 121st Annual Meeting of the American Physiological Society (part of the Experimental Biology 2008 scientific conference) was the site of a presentation by Jain-Wei Gu of the Department Physiology & Biophysics at the University of Mississippi Medical Center in Jackson, who reported that giving mice an antioxidant polyphenol found in green tea helped prevent the growth of breast tumors.
Dr Gu, along with University of Mississippi colleagues Emily Young, Jordan Covington, James Wes Johnson, and Wei Tan, added epigallocatechin-3-gallate (EGCG) from green tea to the drinking water of seven week old female mice for five weeks, while a control group received unenhanced drinking water. During the second week of the study, the animals received injections of mouse breast cancer cells into one of their mammary glands.
At the end of the treatment period, tumor weights, cross section area, intratumor microvessel density (which evaluates angiogenesis, the formation of new blood vessels), and vascular endothelial growth factor (VEGF, found in various cancers) protein levels were measured. Mice that received EGCG had an average of 66 percent smaller tumor cross section areas, 68 percent lower tumor weight, and lower microvessel density and VEGF protein levels in their tumors and plasma than mice that did not receive the polyphenol.
Dr Gu suggested that EGCG works by directly targeting tumor blood vessels via suppression of angiogenesis, as well as targeting tumor cells by helping to prevent their proliferation and migration.
"In this study we have demonstrated that the frequent ingestion of EGCG significantly inhibits breast tumor growth, VEGF expression and tumor angiogenesis in mice," Dr Gu concluded. "We believe our findings will help lead to new therapies for the prevention and treatment of breast cancer in women."
Related Health Concern: Cancer treatment: The Critical Factors
According to the National Cancer Institute, solid tumors cannot grow beyond the size of a pinhead, that is, 1-2 cubic mm, without inducing the formation of new blood vessels to supply the nutritional needs of the tumor. Since rapid vascularization and tumor growth appear to occur concurrently, interrupting the vascular growth cycle is paramount to overcoming the malignancy.
Tumor angiogenesis results from a cascade of molecular and cellular events, usually initiated by the release of angiogenic growth factors. At a critical phase in the growth of a tumor, the tumor sends out signals to nearby endothelial cells to activate new blood vessel growth. The pro-angiogenic growth factors diffuse in the direction of preexisting blood vessels, encouraging development (Folkman 1992 b; Folkman et al. 1992 a).
Various agents are known to activate endothelial cell growth, including angiogenin, estrogen, interleukin-8, fibroblast growth factors (both acidic and basic), prostaglandin E2, tumor necrosis factor, granulocyte colony-stimulating factor, and VEGF. VEGF and basic fibroblast growth factors are expressed by many tumors and appear particularly important to tumor development and angiogenesis (NIH/NCI 1998)
A number of substances from orthodox and natural pharmacology (angiostatin, endostatin, interferons, interleukin-2, curcumin, green tea, lactoferrin, N-acetyl-cysteine (NAC), resveratrol, grape seed-skin extract, retinoic acid (vitamin A), and vitamin D) are antiangiogenic in nature. Endostatin, a fragment of collagen XVIII, and angiostatin, a fragment of plasminogen involved in the coagulation process, have produced remarkable results in animal models.
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