A new approach to treating cancer is under investigation, based on slowing the changes in a cell's DNA which lead to tumours.

US researchers are exploring whether drugs, such as anti-oxidants, might slow the rate at which these cancer-causing mutations arise in a cell's genetic material.

"If we could slow the rate of accumulation of mutations, we could slow the course of the cancer," said Professor Lawrence Loeb of the University of Washington School of Medicine.

Every cell contains genetic information in the form of the molecule DNA.

Human DNA is made up of three billion pieces of information, or nucleotides.

Normally when a cell divides it exactly copies these three billion nucleotides with approximately only one error, or mutation, per cell division.

Mutation rate

Scientists have always believed the rate at which mutations occur when a cell or a virus divides is fixed. But Professor Loeb, speaking in Washington at the annual meeting of the American Association for the Advancement of Science (AAAS), said his group's research suggested it might be possible to alter this mutation rate using new drugs.

He also said new therapies for HIV and Aids might be developed using a different approach - making the HIV virus mutate so fast that it self-destructs.

Such a treatment has two theoretical advantages over existing treatments: it would be effective against all strains of the HIV virus and would be unlikely to lead to drug resistance.

Professor Loeb said his research group has one promising candidate as an anti-HIV therapy that is currently being tested in the laboratory.