esday, 4 April, 2001, 23:03 GMT 00:03 UK

Pill to 'stop cancer'

Scientists are developing a once-a-week pill they hope will prevent half of all cancers.

The drug - called oltipraz - works by activating the body's natural defence mechanisms to block tumours before they have a chance to form.

It is already undergoing trials in China.

Oltipraz was originally developed to treat schistosomiasis - a disease caused by parasitic worms.

However, New Scientist magazine reports that the drug was found to stimulate the body to make an enzyme called glutathione S-transferase (GST).

GST neutralises substances such as benzene which are known to cause cancer by damaging the genetic material of cells.

Tests in animals have confirmed that GST can prevent cancer.

The China trials are being carried out by toxicologist Dr Thomas Kensler, of Johns Hopkins University in Maryland.

Liver cancer common

In China as many as one in 10 adults die from liver cancer caused mainly by a chemical called aflatoxin, which is found in moulds growing on rice and cereal grains.

Dr Kensler gave oltipraz to volunteers in Qidong once a week for two months.

They excreted over twice as much neutralised aflatoxin in their urine as volunteers given a placebo.

Dr Kensler said: "GST was boosted in these people.

"The carcinogen interacts with GST rather than with their DNA."

Dr Kensler is now analysing the results of a longer study. If the results are good, trials will take place over many years to see if oltipraz really reduces cases of liver cancer.

GST and related enzymes detoxify a broad range of carcinogens, so the approach should protect against other types of cancer too.

Raymond Bergan at Northwestern University in Illinois is now enlisting volunteers for a trial to investigate whether oltipraz can protect smokers against lung cancer.

People smoking more than one pack per day will take either a placebo or an oltipraz pill weekly for three months, to see if the drug can alter the level of carcinogens in their lungs.

Vegetables

Chemicals that boost the production of enzymes such as GST are found naturally in vegetables such as broccoli and brussels sprouts.

Dr Yongping Bao, of the Institute of Food Research in Norwich, predicts that in three years' time we will be able to use chemicals isolated from vegetables in pills or to fortify food.

Dr Roland Wolf, a researcher for the Imperial Cancer Research Fund based at Dundee University, said: "If we can isolate these chemicals, there is the potential for a huge impact on cancer."

Dr Wolf also believes that if DNA can be protected from damaging chemicals it might be possible not only to prevent cancer, but to slow the ageing process.

He said: "In animals, you can keep switching on these enzymes for life, and the only side effect is increased longevity."

Professor Gordon McVie, director general of the Cancer Research Campaign, said: "Oltipraz is in the very earliest stages of testing in people. If it works according to predictions, it could be helpful in preventing cancers known to be caused by certain chemicals.

"The results of this trial will not be known for several years."

-- Anonymous, April 05, 2001