(Agencies)
Updated: 2007-10-06 09:12

British scientists who have genetically engineered a virus that normally causes heavy colds so that it attacks cancer believe it could yield a new way to fight the disease.

A reporter sits in front a projected image showing virus infected cells inspected under a microscope during a news conference in Hong Kong, in this March 27, 2003 file photo. [Agencies]

Cancer researchers think engineered viruses will have advantages over many existing types of chemotherapy because they will be more targeted to attacking tumors and so cause fewer side effects. At the moment, most chemotherapies harm both cancerous and non-cancerous cells, leading to hair loss and nausea.

The modified adenovirus exploits what Lawrence Young, who is leading the research project at the University of Birmingham, calls the cancer cell's "Achilles heel".

"It's a little molecular switch (on the cell's surface)," he said. "If you switch it on it does two things -- it induces the cells to die, but it also provokes the body's immune response to destroy the cancer. So it is a double whammy."

The team is not sure why the switch is there or why it has the killing effect, but experiments on rodents suggest that the genetically modified virus is effective at starting the death of the cancer.

"Because viruses have evolved to deliver genes to cells we can manipulate them so they don't do anything harmful to you, but can actually deliver manipulated genes and proteins to cancer cells," he said.

The team, which presented its work at the National Cancer Research Institute Conference in Birmingham on Wednesday, hopes to begin trials on patients in 18 months' time.

The switch -- a molecule called CD40 -- is present on other non-cancerous cells in the immune system, but when the virus binds to it there, it does not have the same effect. Initial safety trials in humans will probably involve 10 liver cancer patients and 10 ovarian cancer patients, but CD40 is also present on lung cancer, skin cancer, bladder cancer and cervical cancer cells.

There are few effective treatments for liver cancer, and in ovarian cancer the tumor cells frequently acquire genetic changes that make them immune to chemotherapy drugs. Another advantage of the virus approach is that it can partially reverse this effect as well, so it may be most effective in combination with chemotherapy drugs.