Green Tea

The Professors' Posts

Green Tea

TERRY HAMBLIN

Somebody asked my opinion on green tea.

I expect everyone is aware of the study from the Mayo clinic that a green tea extract induces apoptosis of CLL cells in the test tube. Apoptosis is a special programme that is set in motion to kill CLL cells. It is sometimes called programmed cell death. In fact most chemotherapy works by invoking apoptosis.

I am keeping an open mind on green tea.

What I know is that killing CLL cells in a test tube is much easier than killing them in the body. There are a number of mechanisms that resist apoptosis in the body.

Eventually there will be clinical trials on green tea extracts and then we will know; until then it is guesswork. There have been a lot of substances that looked good in the test tube but were hopeless in patients.

TERRY HAMBLIN

There is an editorial on Green Tea in today's (18 September 2004) LANCET.
Volume 364 pages 1021-2

It is the main constituent, epigallocatechin-3-gallate, or EGCG, that has
the effect on CLL cells. I don't know of any information that caffeine is
necessary to release of activate it, but one needs to be sure that the
decaffeination process does not inadvertantly remove the EGCG.

The benefit is supposed to be because in order to stay alive CLL cells need
to secrete and bind to a chemical called vascular endothelial growth factor
(VEGF). Addition of EGCG to CLL cells in the test tube inhibits VEGF receptor
phosphorylation and prevents apoptosis (programmed cell death).

In other words CLL cells make VEGF which then binds to a receptor on the CLL
cell. EGCG prevents this binding or at least the response to the binding,
which is necessary to send the signal to keep the cell alive. The quantities af
EGCG achieved in the test tube can be attained by drinking 2-4 cups of green
tea a day.

Green tea's reputation in cancer came because it inhibits VEGF mediated
signaling that is necessary for a cancer to develop a blood supply. Although this
is vital for other forms of solid tumors, it is not needed for CLL. There is
epidemiological evidence (evidence taken from big surveys of peoples
lifestyle habits) that green tea drinkers have a lower incidence of some types of
cancer including cancer of the esophagus (gullet).

As yet there are no clinical studies of green tea in CLL, but I know there
are hundreds of CLLers on the LIST who are taking Green tea. It would be very
useful to us all if anybody taking green tea were to report its effects - good
or bad. It is just as important to know if it has no effect on your white
count as if it lowers it.

Since I have been reading the contributions i have become much more aware of
how common both fatigue and neuropathy are in CLL.

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