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Green Tea Fights Cancer ~ [Issue 1199-5]  Wellness Weekly
 Nov 30, 1999 15:23 PST 

For years, many people, especially in Asia, have thought green tea to
be a health-supporting beverage. New evidence shows certain compounds
contained in green tea may actually fight cancer. Two researchers,
Dorothy Morre and D. James Morre, found that a natural compound in
green tea by the name of EGCg inhibits an enzyme required for cancer
cell growth. They also discovered it can kill cultured cancer cells
with no ill effects on healthy cells.

Dorothy Morre is a Professor of Foods and Nutrition at Purdue
University, where James is a Dow Distinguished Professor of Medicinal
Chemistry and Molecular Pharmacology. The study they co-authored
provides the first scientific evidence helping to explain how EGCg
works. Presented at the 38th annual meeting of the American Society
for Cell Biology in San Francisco, their findings suggest that
drinking more than four cups of green tea per day could provide
enough of the active compound to slow and prevent the growth of cancer cells.

Green tea differs from black tea in the way the leaves are processed
after harvesting. Black tea leaves are "withered" indoors and allowed
to oxidize. Green tea leaves are not oxidized, but are steamed and
parched, preserving important substances.

Previously, scientists had noted a lower overall risk of cancer among
people who drank more than four cups of green tea per day, but they
lacked a good explanation. This milestone independent study shows how
green tea interacts with an enzyme on the surface of many types of
cancer cells, including breast, prostate, colon cancers and
neuroblastomas. This enzyme, quinol oxidase (also called NOX), helps
facilitate several functions on cell surfaces and is required for
growth in both normal and cancerous cells. According to the
researchers, normal cells express NOX only when they are dividing in
response to growth hormone signals. On the other hand, cancer cells
have the ability to express NOX activity constantly. This overactive
form of NOX (known as tNOX, for "tumor-associated" NOX), has long
been considered vital for the growth of cancer cells. Similarly,
drugs which inhibit tNOX activity are known to block tumor cell
growth in cultures.

Studying cultured cells and isolated membranes of cells, the Morres
found that black tea could inhibit tNOX activity at dilutions of one
part tea to 100 parts of water. Green tea infusions, however, were
between 10 and 100 times more potent. Because of the active compound
at these levels, the couple reasoned, drinking several cups of green
tea per day might inhibit the growth of cancer cells in the body.

To determine what the active compound was, they tested several
polyphenolic compounds found in tea, including epigallocatechin
gallate, or EGCg, a primary component of green tea linked to
anti-cancer effects. Their studies found that EGCg did not inhibit
the NOX activity of healthy cells, but could inhibit the tNOX
activity of cancer cells, even at low doses such as those equivalent
to drinking several cups of green tea per day. They showed that
cancer cells in the presence of EGCg failed to grow after division
and, as a result, simply died. The researchers admit further study is
needed to understand how tNOX works in cancer cell growth, but it is
enlightening to learn that when tNOX is inhibited, cancer cells eventually die.
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