A new study shows how viruses such as herpes can trigger a natural "brake" in the immune system to protect themselves. One herpes virus with this ability can trigger a cancer called 'Kaposi's sarcoma' in susceptible individuals.
The discovery could lead to a new generation of treatments that would prevent viruses from exploiting microRNAs – small chunks of genetic material that regulate gene activity. Scientists estimate a third of genes may be regulated by microRNAs.
Study author Dr Dimitrios Lagos, from the Cancer Research UK Viral Oncology Laboratory at University College London, said: "The viruses we tested have evolved with humans for millions of years and use a variety of biological tricks to establish life-long and mostly harmless infections.
"We discovered that it is likely that other viruses – which can cause diseases including cancer – exploit the tiny molecules present in everyone's DNA, called microRNAs, to turn cells into a viral 'hotel' which they can check into to cause infection and spread."
The scientists, who are funded by Cancer Research UK and the Medical Research Council at the UCL Cancer Institute, believe the discovery could lead to the development of new treatments that could prevent the spread of viruses which in some cases can cause cancer by switching off the microRNAs.
Lead author Chris Boshoff, Professor of Cancer Medicine at University College London, said: "We are investigating micro-RNAs as future therapeutic targets, and targeting cellular microRNAs could be a potential way to prevent or treat cancer-causing infection from viruses.
"The link between viruses and cancer is well known – in fact around 20 per cent of cancers worldwide are caused by viruses. But it wasn't known how viruses used microRNA to help them establish infection.
"Now we understand more about how viruses can take hold of the cell and suppress the immune system. If we can create treatments that can specifically target these microRNA then we can switch them off – perhaps for a short period of time."
Dr Lesley Walker, director of cancer information at Cancer Research UK, said the research was "intriguing", before adding: "This unravels an ancient molecular mystery – and provides a hot new therapeutic target to prevent cancer-causing infection from viruses.
"Infectious viruses and human DNA have been around for so long that a relationship has developed and viruses can cheekily use the bits of our DNA that we often think of as rubbish for their own benefit. Now we know how they are using our DNA we can research ways to put the brakes on it."
The research is published in the journal Nature Cell Biology.