By David Ljunggren

OTTAWA (Reuters) - Canadian researchers said on Wednesday that they had made a potentially significant breakthrough in the fight against cancer by discovering that tumour cells could be killed by injecting them with a rare virus.

Dr John Bell of the University of Ottawa said his team had found many common cancers were destroyed by Vesicular Stomatitis Virus (VSV), which is not infectious in humans.

``We're excited. We think this is an important step forward,'' he told Reuters in an interview. In laboratory tests the new treatment killed cells from melanomas and leukaemia as well as lung, breast and prostate cancers.

Bell said 15 years of research into tumours had shown that many cancer cells suffered from a genetic flaw that made them vulnerable to VSV, which has been under study for the last 50 years or so.

``Knowing what this (genetic) defect was and knowing the properties of the virus, we thought this would be a good fit. So we then tested the virus and sure enough it was very effective,'' said Bell.

More tests will now be carried out on laboratory animals and if all goes well the first clinical trials on human beings could start in about 18 months.

``Dr Bell's findings are potentially very important. We look forward to seeing the results of the preclinical studies to evaluate the possible efficacy of this virus as a cancer therapy,'' said Robert Phillips, head of Canada's National Cancer Institute.

Cancer is the second biggest killer in most developed countries after heart disease. In 1997 the World Health Organisation said 10 million people were diagnosed a year with the disease and six million died.

``There are other people out there in Canada, the United States and Europe who are working on viruses as well and we think probably their viruses are working the same way that ours is and they haven't appreciated it yet,'' said Bell.

The team experimented on human melanoma cells which had been transplanted on to mice, and also worked on other kinds of human cancer cells grown in laboratories. The findings will be published in the July 1 edition of Nature Medicine magazine.

The one possible cloud on the horizon is how human patients react to the large amounts of VSV that Bell's team said would have to be administered for the treatment to be effective.

``We have to do some more work to convince ourselves this wouldn't be toxic to humans. We don't think it will be but we have to be absolutely sure,'' he said. ``Right now, everything we have suggests to us that normal humans would not be affected by the virus, since mice are not but human tumours are. That's why we're fairly optimistic.''

Another problem is making enough pharmaceutical-grade VSV for the trials and the University of Ottawa has signed a deal with Maryland-based Pro-Virus Inc. to ensure a steady supply. ''Whether it's the virus or the defect or the combination we've discovered we think this will have important implications in developing new therapies,'' Bell said. ``I don't think we're trying to get anyone's hopes up. I think the people out there dealing with cancer every day need to have something to be optimistic about. In their battle they need to have something on the horizon.''

　　(From Yahoo)