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New technique kills cancer virus without harming healthy cells

September 03, 2002

Major breakthrough could lead to successful treatment of viral cancers, without side-effects.

Yorkshire Cancer Research funded researchers at the University of York have made a major cancer breakthrough. Using a new technique called RNA interference, they have successfully killed human cervical cancer cells grown in culture without causing damage to healthy cells.

The discovery could have major implications, potentially leading to the successful treatment of cancers caused by viral infection without any harmful side effects.

The research, carried out by Professor Jo Milner and Dr Ming Jiang, is the first of its kind to use RNA interference to attack cancerous cells. The impact of the technique - the total elimination of all cancerous cells - was unexpected.

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

Human cervical cancer, caused by viral infection, is the second most common form of cancer in women worldwide and kills around 1,250 women in the UK alone each year. Cervical cancer develops when the virus attacks the body`s two front lines of defence - its two tumour suppressors, the proteins p53 and RB.

In normal cells RB controls cell division, whilst p53 has the ability to kill damaged cells that might become cancerous. The virus attacks both these proteins and takes over the reins of cells growth, driving continual out-of-control cell proliferation.

Dr Jiang and Professor Milner wanted to know if the use of RNA interference - never before used on mammalian cells - could knock out viral genes in the infected cells and restore the body`s normal defence mechanism.

The silencing of one viral gene - HPV E6 - caused the growth of the tumour cells to slow and some cells died. Remarkably, when the second viral gene was silenced (HPV E7 gene), all the cancer cells died.

Using RNA interference, the infected cells died by a regulated process known as ‘apoptosis`, which enables cells to be removed without inflammatory side-effects.

It was important, however, to establish that normal healthy cells remained unaffected. In control experiments, researchers found that the anti-viral treatment had no effect on the normal growth and behaviour of non-infected human cells. The successful elimination of cancer cells without adverse effects on normal cells was described by Professor Jo Milner as "absolutely remarkable".

"These cancer cells were not engineered in the laboratory. They were derived from a human tumour many years ago. Despite growing as cancer cells for years (due to the viral infection) our work demonstrates that the cells` normal control systems have remained intact. As soon as we silenced the viral genes, the infected cancer cells ‘committed suicide`."

Elaine King, Chief Executive of Yorkshire Cancer Research, the charity which funded the research said: "This really is encouraging news and proves once again that the research we fund in Yorkshire really is world class. The hard work and dedication of Yorkshire Cancer Research funded scientists is unwavering and it is this on-going research process that brings about these breakthroughs. While such breakthroughs, by their nature, don`t happen every day, it is crucial that we continue to fund research, for which we continue to rely on the generosity of the people of Yorkshire."

"I would like to offer my sincere congratulations to Professor Milner, Dr Jiang and their team at York and my thanks to our supporters who have made it all possible."

Professor Milner and Dr Jiang are now working on other types of tumours to see if the technique is as effective. Meanwhile, researchers in the United States have found that RNA interference is showing promising results in protecting cells from infection with the HIV virus, signalling that many types of human viral infection could be cured in the future by drugs based on the technique.

York, University of