Scientists have discovered a way to kill cervical cancer cells - without harming the surrounding healthy cells.

Researchers hoped to find out if they could restore the body's defence system against cancer - but instead they were able to destroy all cancer cells

It is hoped the discovery could lead to the successful treatment of cancers caused by viral infection without any harmful side effects.

Cervical cancer kills around 1,250 women in the UK each year.

The researchers have managed to put the brakes on the uncontrolled growth of cervical cancer cells

Thomas Lober, Cancer Research UK

Most cases are caused by human papillomavirus which attacks two tumour suppressors, proteins p53 and RB.

In normal cells, the RB protein controls cell division and p53 kills damaged cells which may become cancerous.

But when these proteins are attacked by the virus, they can no longer do the job they are supposed to.

Cancer cells can then proliferate without control.

'Silencing' genes

The researchers, based at the University of York used a technique called RNA interference.

DNA contains genetic information and RNA carries that genetic information to cells.

Scientists have discovered they can "interrupt" selected messenger RNA going to a specific target.

Researchers looked at two genes linked to the virus - HPV E6 and HPV E7.

They wanted to see if they could "silence" them, and prevent the virus attacking the proteins.

It was found that by silencing HPV E6, the growth of cancer cells was slowed, and some even died.

When HPV E7 was silenced , all the cancer cells died.

The cancer cells died by a regulated process known as 'apoptosis', in which cells can be removed without any side effects.

The researchers found that, crucially, the anti-viral treatment does not affect healthy cells, which carry on growing and behaving normally.

'Encouraging'

Professor Jo Milner, who led the research, said: "Our work has identified a novel agent with major therapeutic potential for the treatment and, possibly, also the prevention of human cervical cancer.

"Despite their cancerous growth over the years, our work demonstrates that the cells' normal control systems have remained intact.

"As soon as we silenced the viral genes, the cancer cells 'committed suicide'.

"The successful elimination of the cancer cells, without adverse effects on normal cells, is absolutely remarkable."

She told BBC News Online: "The next step is to expand our work in the laboratory and begin clinical trials.

"This is not a biological intervention, it's a genetic intervention."

Professor Milner said the research could lead to work on a therapeutic drug within three to five years.

"This technique could also be used in relation to other cancers such as some leukaemias caused by viruses and some lymphomas."

The research was funded by Yorkshire Cancer Research, and is published in the journal Oncogene.

Thomas Lober, science information officer for Cancer Research UK said: "These findings are encouraging, and a step towards a highly specific treatment for cervical cancer.

"The researchers have managed to put the brakes on the uncontrolled growth of cervical cancer cells grown in the lab."