Green Tea, Glycine May Slow Tumor Growth
Nov. 2, 2001 -- You've probably read that green tea appears to protect
against cancer. You may even know that its anti-cancer properties are
attributed to an abundance of chemicals called polyphenols. But new
research may explain, for the first time, how those chemicals fight
tumors at a molecular level.
Using prostate cancer cell lines, researchers from H. Lee Moffitt Cancer
Center in Tampa, Fla., found that polyphenols in green tea, and black
and red teas for that matter, target a protein known to protect cancer
cells from death.
The research, along with several other studies evaluating the anti-tumor
properties of food components, was presented this week at an
international conference in Miami Beach, Fla.
The amino acid glycine was found to reduce breast tumor growth in rats.
Apparently, it blocks the growth of new blood vessels that feed tumors.
Glycine is manufactured in the body, but is also commercially available
as a dietary supplement.
"These are very preliminary studies, but they are quite interesting,"
American Association for Cancer Research (AACR) President Waun Ki Hong,
MD, tells WebMD. He says that human studies are needed to verify the
findings, but this may represent an important contribution to the
research. AACR co-sponsored the annual meeting along with the National
Cancer Institute and the European Organization for Research and
Treatment of Cancer.
In the green tea research, Aslamuzzaman Kazi, PhD, and colleagues found
that polyphenols reduced the level of Bcl-XL protein in prostate cancer
cell lines. Bcl-XL has been shown to protect cancer cells from death --
known scientifically as apoptosis
"The higher the concentration [of polyphenols] the more apoptosis," Kazi
tells WebMD. "Epidemiological studies have shown that tea has anticancer
activities. We wanted to try to understand the molecular mechanism of
this action."
Studies in humans have, in fact, been inconclusive regarding the role of
tea in preventing or slowing cancers. While some have shown a clear
protective benefit, others have not. The most recent large study,
published last March in The New England Journal of Medicine, found that
drinking green tea did not lower the risk of developing stomach cancer
in a group of Japanese subjects.
In the glycine study, researcher Zishan Haroon, MD, PhD, and colleagues
at Duke University Medical Center, found high levels of glycine reduced
breast tumor growth rates by 15% in rats by blocking the growth of new
tumor-feeding blood vessels. The special diet also reduced wound-healing
by 30%, which, Haroon tells WebMD, explains glycine's effect on tumors.
"Tumors and wounds have one very important thing in common -- they both
produce new blood vessels through the same mechanism, known as
angiogenesis," he says. If you can block one response, you can block the
other, he says.
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