Brussels, 15 Mar 2005
A European Union funded project involving Spanish and UK scientists has established for the first time why drinking green tea can protect the body against certain forms of cancer.
Previous epidemiological studies had already revealed the positive effects of green tea consumption on certain types of cancerous cells. Now scientists from the University of Murcia, Spain, and the John Innes Centre in Norwich, the UK, say they have isolated the substance responsible, offering a potential starting point for a new family of anti-cancer drugs.
The researchers report that in laboratory experiments, a naturally occurring polyphenol (EGCG) isolated from green tea leaves inhibits the growth of cancer cells when present at the low concentrations found in green tea drinkers. However, they warn that the target enzyme with which EGCG binds to inhibit the growth of cancer cells has also been linked to birth defects such as spina bifida.
'This is a very exciting discovery,' said Roger Thorneley, leader of the UK team. '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.'
Jose Neptuno Rodriguez-Lopez, the Spanish team leader, added: '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.
'We are 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,' Dr Rodriguez-Lopez added.
Pharmaceutical companies are keen to develop alternatives to methotrexate and related drugs because of the significant amount of damage they inflict on healthy cells, particularly in the liver and bone marrow. The researchers believe that EGCG is a potential 'lead compound' for the development of such alternatives.
However the team also warned that higher than normal levels of green tea consumption by women trying to conceive and during pregnancy can lead to increased incidence of spina bifida and other birth defects. Such defects are linked to folic acid deficiency, which the researchers believe is due to EGCG significantly decreasing folic acid levels in the body.
The research was supported by funding under the Europe's INTAS programme, an independent association created by the European Community, EU Member States and like minded nations to support scientific cooperation with countries from the newly independent states (NIS) of the former Soviet Union. A research group in Georgia had been studying the medical properties of green tea extracts for some time, and the INTAS programme provided Drs Thorneley and Rodriguez-Lopez with travel funds to visit Georgia and exchange ideas and information.
The patent holder for the discovery, the University of Murcia, has assigned the intellectual property rights associated with the discovery to the UK company Plant Bioscience.