By JAMES GALLAGHER - BBC HEALTH
Added: Thu, 09 Feb 2012 22:44:15 UTC
Destructive plaques found in the brains of Alzheimer's patients have been rapidly cleared by researchers testing a cancer drug on mice.
The US study, published in the journal Science, reported the plaques were broken down at "unprecedented" speed.
Tests also showed an improvement in some brain function.
Sections of Alzheimer's, left, and healthy brain tissue showing brain shrinkage with the condition
Specialists said the results were promising, but warned that successful drugs in mice often failed to work in people.
The exact cause of Alzheimer's remains unknown, but one of the leading theories involves the formation of clumps of a protein called beta-amyloid. These damage and kill brain cells, eventually resulting in memory problems and the inability to think clearly.
Clearing protein plaques is a major focus of Alzheimer's research and drugs are already being tested in human clinical trials.
In the body, the role of removing beta-amyloid falls to apolipoprotein E - or ApoE. However, people have different versions of the protein. Having the ApoE4 genetic variant is one of the biggest risk factors for developing the disease.
Helping hand Scientists at the Case Western Reserve University in Ohio were investigating ways of boosting levels of ApoE, which in theory should reduce levels of beta-amyloid.
They tested bexarotene, which has been approved for use to treat cancers in the skin, on mice with an illness similar to Alzheimer's.
After one dose in young mice, the levels of beta-amyloid in the brain were "rapidly lowered" within six hours and a 25% reduction was sustained for 70 hours.
In older mice with established amyloid plaques, seven days of treatment halved the number of plaques in the brain.
The study said there were improvements in brain function after treatment, in nest building, maze performance and remembering electrical shocks.
Researchers Paige Cramer said: "This is an unprecedented finding. Previously, the best existing treatment for Alzheimer's disease in mice required several months to reduce plaque in the brain."