Dec. 2, 2001
     Prostate Cancer

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Anti-cancer mechanism of green tea identified

TAMPA, Fla., Dec. 2, 2001 (Cancer Digest) -- Researchers have identified a possible mechanism by which green team may protect against prostate and other cancers.

Working with prostate cancer cells in mice, the research team led by Dr. Aslamuzzaman Kazi at the Moffit Cancer Center at the University of Florida showed that the applying the active ingredient in tea called, green tea polyphenols (GTP) to the cells in different concentrations had a proportional effect on a protein called Bcl-XL.

"The higher the concentration, the better the response," said Aslamuzzaman Kazi in a press release. "Meaning more apoptosis, or programmed cell death occurred as a result of lower levels of Bcl-XL, which protects cancers cells from programmed cell death or apoptosis. At all concentrations, response was apparent within three hours."

Although the Moffitt team used purified compounds from green tea, black tea contains nearly identical polyphenols that also have demonstrated protective effects against cancer. Research in previous mice studies has shown that an amount of GTP equal to two or three cups of tea per day in humans is effective in cancer prevention.

A Japanese study of breast cancer patients found that women who drank more than five cups of green tea daily had a lower recurrence rate and longer disease-free survival than women who drank fewer than four cups daily. Until the current study, however, just how the tea might provide this protective effect was unknown.

"Because Bcl-XL is overexpressed (overproduced) in many cancers, it could be a key target in all cancers and explain why GTP is able to prevent human cancers in mouse models," said Dr. Ping Dou, associate professor of oncology, biochemistry, and molecular biology at Moffitt.

Dou and Kazi caution that their findings are a long way from clinical application. Next, they want to identify the direct target of tea polyphenols in human cancer cells.

"Our data suggests that at least one enzyme may modify Bcl-XL and that it is the actual target of tea," Dou explained. "We also want to see if that target is present in all human cancers."

Until the effects of GTP are fully known, there are no known health hazards from drinking tea, the world's most widely consumed beverage.