Gene therapy works for cancer, radiation in mice

WASHINGTON, June 4 (Reuters) Gene therapy experiments suppressed hard-to-treat ovarian cancer in mice and also protected them against the effects of toxic radiation, scientists reported.

It is much easier to treat mice artificially inoculated with tumors than it is to treat people, but the researchers say their approaches suggest promise for the troubled field of gene therapy.

The ovarian cancer study suggests a new route for treating a deadly cancer that kills 16,000 women a year in the United States alone. Most ovarian cancer patients live four years or less after they are diagnosed.

''Current treatments for ovarian cancer are fairly harsh.

(Gene therapy) ... represents a potent, non-toxic alternative for treating this deadly disease,'' Dr. David Bartlett at the University of Pittsburgh Medical School said in a statement yesterday.

Speaking at a meeting of the American Society of Gene Therapy in Baltimore, Bartlett and colleagues said they injected mice with ovarian cancer cells.

They treated some of the mice immediately with a virus genetically engineered to carry cytosine deaminase, a so-called suicide gene that helps cancerous cells self-destruct.

Some other mice were treated with the gene therapy 30 or 60 days later, while a third group was given no treatment.

Tumors did not grew in the mice that were treated immediately with gene therapy, and those treated a month or two later had tumors that grew only very slowly.

The untreated mice either died or had to be euthanized because of their quick cancer progression.

A second team of experts from the Mayo Clinic College of Medicine in Minnesota and Insituto Nazionale Tumori in Milan, Italy, used a genetically engineered measles virus to destroy ovarian cancer tumor cells in a lab dish.

It would be years before such approaches could be widely used in humans.

Some gene therapy approaches have helped patients. But one 18-year-old volunteer died in a gene therapy experiment in 1999 and two French boys cured of a rare immune disease by gene therapy developed leukemia later that was caused by the treatment.

So doctors now proceed cautiously with gene therapy, although there have been some successes such as a Sanofi-Aventis experiment in which gene therapy apparently helped new arteries grow in patients with severely decreased blood flow to the legs.

A second University of Pittsburgh team used gene therapy to deliver a compound called manganese superoxide dismutase-plasmid liposome (MnSOD-PL) to mice, and then exposed them to radiation.

The compound is known to protect cells from the effects of radiation. Dr Joel Greenberger, a cancer specialist who led the study, has been trying to find effective ways to get the compound into vulnerable cells in the body.

Untreated mice irradiated at higher doses lost weight and died fairly rapidly due to bone marrow damage. But mice treated with the gene therapy lost no weight, had little bone-marrow damage, and lived longer, the researchers told the meeting.

Greenberger hopes the approach might work in case of a ''dirty bomb'' or other radiological attack.

''This treatment is probably most effective when it is administered before exposure to radiation, as would be the case for first responders entering a radioactive environment,'' Greenberger said in a statement.

''However, we have shown that it does have post-exposure, or mitigation, properties when we've administered it as a supplement to bone marrow transplantation. So, it also may be effective for treating people who have already been exposed to a radioactive event,'' he said.

REUTERS SY RN0907