Common virus can kill cancer tumors

Scientists have wiped out tumors in mice using a common virus that apparently tricks cancer cells into self-destructing.

It is too early to know if the approach might work in humans. Many treatments that look promising in mice prove disappointing when they are tested on people.

However, the research sheds light on something scientists have noticed for years: Some viruses harm cancer cells but leave normal, healthy cells unscathed.

The research involves a virus that is believed to be harmless to humans, and a gene called p53 that normally suppresses tumors. In most cancer patients, the p53 gene is defective. The virus apparently zeroes in on that flaw.

Peter Beard, a professor of virology at the Swiss Institute for Experimental Cancer Research in Epalinges, said his team found that the explanation involves an unusual hairpin-like portion of the virus' DNA.

When a cancer cell encounters the virus, it apparently interprets the hairpin structure as damage to its own DNA. The cell tries to rid itself of the damage and ends up self-destructing.

As part of their research, the Swiss team injected human colon cancer cells into a group of laboratory mice, followed by the virus two days later. Only two of the 12 rodents later formed tumors.

In mice with existing colon cancer tumors, injections of the virus eliminated tumors in six of the 10 rodents.

The findings were reported in Thursday's issue of the journal Nature.

Beard said his team hopes to pinpoint the precise feature on the hairpin structure that sends cancer cells to their death.

If they can do that, he said, it may be possible to specially engineer the virus or even develop a drug mimicking its effects.

Cancer researcher Arnold J. Levine, co-discoverer of the p53 gene in 1979 and president of Rockefeller University in New York, said research's main contribution is explaining why certain viruses can damage cancer cells while sparing normal cells.