Cancer hope from green tea extract
A chemical extracted from green tea could help scientists to
develop new drugs to fight cancer. Tests by UK and Spanish
researchers showed polyphenol EGCG taken from green tea leaves
inhibits cancer cell growth.
The effect was seen even at low concentrations, equivalent to
drinking two or three cups of green tea a day.
However, the study, published in Cancer Research, also found high
concentrations of the chemical may increase the risk of birth
defects.
Previous research has suggested that drinking green tea helps to
cut the risk of certain forms of cancer.
The latest study found that EGCG binds to a key enzyme -
dihydrofolate reductase (DHFR) - that is targeted by established
anti-cancer drugs.
This stops the enzyme from triggering the manufacture of new DNA in
tumour cells.
It appears to work in the same way as the cancer drug methotrexate
- but in practice would probably have fewer side effects.
Drug development
Professor Roger Thorneley, from the John Innes Centre in Norwich,
conducted the research with team from the University of Murcia in
Spain.
He said: "This is a very exciting discovery. For the first time we
have a clear scientific explanation of why EGCG inhibits the growth
of cancer cells at concentrations which are found in the blood of
people who drink two or three cups of green tea a day.
"We have identified the enzyme in tumour cells that EGCG targets
and understand how it stops this enzyme from making DNA.
"This means we may be able to develop new anti-cancer drugs based
on the structure of the EGCG molecule."
Fellow researcher Dr Jose Neptuno Rodriguez-Lopez said: "We decided
to look at EGCG because we recognised that its structure is very
similar to that of the successful anti-cancer drug
methotrexate.
"We discovered that EGCG can kill cancer cells in the same way as
methotrexate.
"However, because EGCG binds to the target enzyme less tightly than
methotrexate, it should have decreased side effects on healthy
cells."
Fewer side effects
Dr Rodriguez-Lopez said the researchers were now using EGCG as the
starting point to design and develop effective new anti-cancer
drugs that kill tumour cells but inflict less damage on healthy
cells.
Previous studies have also linked high levels of green tea
consumption around the time of conception and during pregnancy with
an increased incidence of neural tube defects such as spina
bifida.
These defects are associated with a lack of the key nutrient folic
acid.
The scientists said EGCG in green tea would be expected to cause a
significant drop in folic acid levels.
