Tiny magnets used in anti-cancer gene therapy

LONDON (Reuters) - Tiny magnets have been used to deliver anti-cancer gene therapy in mice in a development that could make the treatment much more effective, scientists said on Thursday.

The idea behind gene therapy is to replace faulty genes. But the approach has had mixed success because of the difficulty of getting genes to the right part of the body.

One option has been to use viruses to carry genes but this risks triggering an immune system reaction.

Now British researchers think they may have cracked the problem.

By inserting magnetic nanoparticles into monocytes -- a type of white blood cell -- and injecting them into the bloodstream, they have been able to guide them around the body using an external magnet.

Using this technique, many more cells armed with anti-cancer genes reached and invaded malignant tumors, Claire Lewis of the University of Sheffield and colleagues reported in the journal Gene Therapy.

"The use of nanoparticles to enhance the uptake of therapeutically armed cells by tumors could herald a new era in gene therapy -- one in which delivery of the gene therapy vector to the diseased site is much more effective," Lewis said.

The new approach could also be used to deliver therapeutic genes to treat other conditions like arthritic joints or heart disease, she believes.

Clinical trials on humans, however, are still some way off.

Tests so far have involved treating tumors just under the skin of mice. The real goal is to attack tumors deep inside the body, which are normally the most serious.

"We're going to have to extend existing magnetic resonance, or MRI, technology to create a magnetic gradient over a deep tissue like the liver," Lewis said in a telephone interview.

Her team is also looking at the ability of magnetic targeting to deliver a variety of different cancer-fighting genes, including ones which could stop the spread of tumors to other parts of the body.

Gene therapy has been much hyped over the years as a treatment for cancer and other diseases where DNA is known to play a central role but scientists have run into a series of technical and safety problems.

In one trial in 1999 a patient died and in other cases children have developed leukemia as a result of such treatment.

"We would hope that this will be safer because we are using a natural mechanism in the body and patients' own white blood cells to deliver the gene therapy," Lewis said. "We're simply amplifying that with this magnetic approach."