TUESDAY, Feb. 10 (HealthDay News) -- The DNA of cancer-related viruses may actually change to disguise themselves from the immune system, a new study has found.

An international team of scientists studied the entire genomes of three common viruses -- Epstein-Barr, the human papilloma virus (HPV) and hepatitis B. Each of these pathogens can progress into cancer -- for example, HPV is strongly linked to cervical tumors, and hepatitis B has been tied to liver cancer. About 15 percent of all cancer cases worldwide are linked to a viral infection.

The researchers found that the genomes were generally similar between people who had the virus but no symptoms, those with the disease caused by the virus, and those who developed the virus-related cancer. However, the epigenome -- a layer of biochemical reactions that turns genes on and off -- appeared much different, with the virus increasingly experiencing methylation in patients who had developed cancer.

According to the researchers, methylation (an enzyme-mediated modification to DNA) may prove to be a type of camouflage to help the virus elude the body's natural defense system.

The findings were published online in Genome Research.

"This a very exciting result that can explain why some of these viruses can survive for such prolonged times in our body," senior author Manel Esteller, of the Bellvitge Institute for Biomedical Research (IDIBELL) in Barcelona, said in a news release issued by the journal.

DNA methylation could possible serve as a disease biomarker or as a route to attack the viruses and their associated diseases, Esteller said.

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