Image caption Cancer vaccines make the immune system target tumours

A new approach to developing cancer vaccines has been used to treat prostate tumours, an international team of scientists has said.

DNA from healthy cells was used to create a vaccine which cured 80% of mice, Nature Medicine reports.

The researchers believe the principle could be applied to other cancers and have begun studies on melanoma.

Cancer Research UK said it was a significant development, but human trials would be needed.

Cancer vaccines are not new. Unlike traditional vaccines which protect against infection, these work by making the immune system attack tumours already in the body.

Specifically they target markers on the surface of cancerous cells, known as antigens.

Professor Alan Melcher, of the University of Leeds, said: "The biggest challenge in immunology is developing antigens that can target the tumour without causing harm elsewhere."

Mobilising defences

Researchers in Leeds and at the Mayo Clinic, in the US, broke up chunks of DNA from healthy prostate cells and inserted them into a virus.

This is an interesting and significant study which could really broaden out the field of immunotherapy research Professor Peter Johnson, Cancer Research UK

The mice were then repeatedly infected with the virus.

The prostate DNA made the virus produce a wide range of prostate antigens, so when the immune system battled the virus it learned to attack the cancerous prostate cells.

Crucially, healthy prostate cells and other parts of the body were not affected.

In the lab, a course of nine injections with the virus cured 80% of mice with prostate tumours.

Professor Melcher said human trials were years rather than months away.

"We have reason to be quite excited. It's not out-of-the-blue research, but based on immunotherpay and virus treatments which are looking very promising and that is what is really exciting," he added

Doctors recently claimed that the drug Ipilimumab, which stimulates the immune system to fight cancer, could increase life expectancy.

Researchers say using healthy DNA is a "proof of principle" which could have implications for vaccines for other cancers. They are trialing the same technique in mice with skin cancer.

Professor Peter Johnson, Cancer Research UK's chief clinician, said: "This is an interesting and significant study which could really broaden out the field of immunotherapy research.

"Although the vaccine didn't trigger the immune system to overreact and cause serious side effects in mice, it will need to be further developed and tested in humans before we can tell whether this technique could one day be used to treat cancer patients."

Dr Kate Holmes, research manager at the Prostate Cancer Charity, said the study provided "new hope".

"Although we are hopeful that the results of this study could help to form the basis of a new cancer vaccine in future, it is important to remember that the researchers have only investigated the potential of their vaccine in mice.

"Further research looking at its effect in men is needed. We look forward to the outcome."