London - Viruses may cause up to 40 percent of cancers including brain tumours and leukaemia, scientists claim.
If they are proved correct in further tests, it could pave the way for vaccinations against several types of cancer and therapies to cure them.
The claim follows research which has discovered viruses in types of cancer which were never thought to have been linked with infection. More than 300,000 people a year are diagnosed with cancer in the UK, of whom half will die from the disease.
It has been known for decades that viruses cause some types of cancer but it was thought to be only 10 to 20 percent of cases. The best known are the hepatitis B and C bugs, which can cause liver cancer, and the human papilloma virus (HPV) which can cause cervical cancer.
Last week scientists at the Karolinska Institute in Sweden found a viral link with medulloblastoma, the most common form of childhood brain tumour.
It follows the discovery two years ago that merkel cell carcinoma, an aggressive skin cancer, often follows infection by the polyomavirus which is common among animals and can spread to humans.
It is also claimed that prostate cancers could be caused by viruses.
Nobel Prize winner Harald Zur Hausen, who jointly discovered the link between cervical cancer and HPV in the 1980s, said he expected more discoveries to follow and suggested that viruses could be involved in cancer of the skin, breast, gut and lungs.
But scientists warn it could take a long time and huge investment before vaccines are developed.
Alan Rickinson, professor of cancer studies at Birmingham University, said: “If we can understand how these viruses work we could prevent people from contracting them and even create therapies that use the patient’s own immune system to destroy infected or cancerous cells.”
The process still confounds experts because viruses work by invading cells and making them produce more viruses. But this process then kills the cell which should mean it cannot become cancerous.
One theory is that cancer-causing viruses can remain hidden in cells for years, preventing the cell from repairing mutations. - Daily Mail