Research Explains How Some Viruses Cause Cancer

According to the results of a study published in Genome Research, led by Manel Esteller, director of the Epigenetics and Biology as the results of a study published in Genome Research, led by Manel Esteller, director of the Epigenetics and Cancer Biology Biomedical Research Institute (IDIBELL) and Institute of Oncology (ICO) and ICREA researcher, says that 15% of cancer cases are related to virus. But not all infected people eventually develop a malignant tumor. The malignant process is initiated in cases where the pathogen is able to modify their own genetic material to outwit the body's defenses.
Researchers analyzed more than 500 tissue samples infected by major oncogenic viruses: human papilloma virus, necessary cause for the occurrence of cervical cancer, the hepatitis B virus, related to the occurrence of liver cancer, and Epstein-Barr virus, the cause of some types of lymphoma. They have been collected in three population groups: those infected but not symptomatic, people who have developed an infection or a malignant lesion, and people who have already developed a tumor or cancer associated.

In each of these stages, the genetic material of the virus undergoes important changes in the epigenome. That is, the pattern of chemical signals, a kind of switches, which makes their genes (genome) are expressed or not. Methylation of the disabled, and acetylation activates them. "When the virus enters the body, in the early stages of infection, is expressed in all their genes because it is not methylated. So the immune system can detect and remove it," says Esteller.

But gradually, the virus manages to evade the immune system. As the infection progresses to a premalignant state, the virus are still more methylated, which means that their genes are expressed and leaving, therefore, the immune system it is increasingly costing attack detection and said Esteller. The virus achieves this state by robbing the host cell proteins. The uses to weave a garment with which disguise biochemical immune system. However, it hides your viral load, which is still active. When the malignant tumor appears, the virus has not only fully camouflaged, but the genetic spoliation has also modify the behavior of the cell and turn it into a carcinogen.

What makes these viruses increase their ability to deceive? To get an accurate answer still need more research, but there are indications that on the one hand individual genetic differences influence. And other studies indicate that some environmental exposures facilitate methylation. This is the case of exposure to snuff, to high radiation doses or excesses in the sun, says Esteller. Bad habits not only alter the epigenetics of the virus, but also weaken the immune system and make it easier for viruses to penetrate better into the cell. In fact, when it detects the presence of hepatitis B and C are used drugs that enhance immune system activity. In the case of papilloma virus (HPV), there is still no effective treatment to destroy it, but advises extreme healthy habits so that the immune system to defend itself in the most effective and runs with it, explains Silvia Sanjose, responsible Unit of Infections and Cancer ICO. In women, HPV is a 55% of the tumor-associated infections.

According to both experts, knowing the epigenetics of these viruses will develop treatments that prevent methylation, ie they prevent the virus robs its host cell proteins to trick the immune system. Esteller believes that these alterations may also be present in other viruses responsible for diseases such as influenza and AIDS.

Other research shows that not only inherits the genome, but their pattern of activation, the epigenome. "We believe the epigenome altered by toxic habits could also be inherited," he concludes.