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Green Tea Polyphenol Epigallocatechin Gallate Affects Gene Expression of Breast Cancer Cells Transformed by the Carcinogen 7,12-Dimethylben(a)Anthracene

The incidence of breast cancer is increasing since the 1980s. Up to 10 present of breast cancer cases can be related to genetic factors. Another important risk factor is the contamination of the environment with polycyclic aromatic hydrocarbons. Epidemiological studies have demonstrated that breast cancer rates are linked to carcinogen exposure. Increased levels of polycyclic aromatic hydrocarbons are found in breast cancer tissue. Test with animals have shown that polycyclic aromatic hydrocarbons induce carcinogenesis. Epidemiological studies indicate that green tea consumption protect against breast cancer. The main phytochemical in green tea, which might be responsible for this action, is epigallocatechin gallate. Other phytochemicals in tea which have anti-carcinogenic activity include epicatechin-3-gallate, epigallocatechin and epicatechin.

For this experiment rats were treated with 7,12-dimethylben(a)anthracene (which is a polycyclic aromatic hydrocarbons) which caused mammary tumours in up to 95 percent of the rats. The cDNA microarray test was used to measure the effect of green tea epigallocatechin gallate on gene expression in breast cancer cells. The RNA was analysed from breast cells after treatment with different levels of epigallocatechin gallate. The researchers found that epigallocatechin gallate changed the gene expression of genes involved nuclear and cytoplasmic transport, transformation, redox signalling, and hypoxia and polycyclic aromatic hydrocarbon responses. Some genes were down regulated and others were up regulated. Epigallocatechin gallate down regulated 14 genes including two genes involved in nucleocytoplasmic transport, which is the active transport of proteins and RNA between the nucleus and cytoplasm is cells. Epigallocatechin gallate up regulated 9 genes which have a potential function in tumor biology.

The study concluded that epigallocatechin gallate changed the expression of genes involved in the inhibition of carcinogenesis. The readily availability of epigallocatechin gallate extracts or green tea holds promise for cancer prevention. The ability of epigallocatechin gallate to inhibit carcinogenesis makes it a good template for deriving drugs that are even more effective.

Source: Shangqin Guo, Sanghwa Yang, Chad Taylor and Gail E. Sonenshein. Green Tea Polyphenol Epigallocatechin Gallate Affects Gene Expression of Breast Cancer Cells Transformed by the Carcinogen 7,12-Dimethylben(a)Anthracene. J. Nutr. 135:2978-2986, 2005

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