Scientists find viral trigger for cancer

Some viruses learned to protect themselves by exploiting a natural "brake" on the immune system, research has shown.

The process is complex and involves "microRNAs" – small chunks of genetic material that help regulate gene activity.

One of their roles is to dampen immune responses so they do not run out of control, leading to harmful inflammation.

The new study by British scientists has shown some viruses can boost microRNA activity to suppress the immune reaction against them.

One herpes virus with this ability can trigger a cancer called Kaposi's sarcoma in susceptible individuals.

Another is the herpes simplex virus, which causes cold sores.

Scientists estimate almost a third of genes might be regulated by microRNAs.

Study leader Dr Dimitris 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 research was reported in the journal Nature Cell Biology.