The International Agency for Research on Cancer in Lyon, France, has classified 11 different pathogens as carcinogenic agents and estimates that 1 in 10 cancers is linked to viruses. To further analyze these data, more than 1300 researchers at the German Cancer Research Center (DKFZ) conducted a comprehensive bioinformatic analysis of the sequencing data of more than 2600 tumor genomes from 38 different types of cancer.

The DKFZ discovered traces of a total of 23 different virus types in 356 patients with cancer. The most common drivers of tumor initiation and growth were found, including the genome of Epstein-Barr viruses (EBV) and hepatitis B virus (HBV).

Researchers found human papillomaviruses (HPV), most commonly HPV16, in cervical carcinomas (19 of 20 cancer cases) and head and neck tumors (18 of 57 cancer cases).

In addition, the researchers were able to rule out a connection to the cancers as “highly unlikely” for some of the virus types detected. In a few cases, the team found other known cancer-causing viruses, such as a retrovirus in kidney carcinoma. Other pathogens were occasionally found in the tumors of the tissue type that they normally infect, such as cytomegaloviruses in gastric cancer.

Despite using a thorough bioinformatic analysis, the researchers have not found any completely unknown viruses.

In some of the tumors associated with HPV and EBV, the research team observed that the characteristic driver mutations that the cancer cells normally depend on for growth were missing.

Cellular defense against viruses were identified as another key mechanism that leads to mutations in the DNA of infected cells. Since the cell uses its APOBEC proteins to attack the DNA of dangerous viruses, this leads to mutations of the cell’s own genome. This can result in the development of cervical cancer and head and neck tumors following an infection, such as HPV.

"When analyzing the whole cancer genome, we discovered traces of viruses in considerably more tumors than in earlier studies that were based on investigating the RNA only,” said principal investigator Peter Lichter in a prepared statement. “Nevertheless, we were not able to confirm the common speculation that other, as yet unknown viruses are associated with cancer. However, in many cases we now have a clearer idea of how the pathogens cause malignant mutations in cells."

REFERENCE

Viruses and cancer- systematic overview published. DKFZ. https://www.dkfz.de/en/presse/pressemitteilungen/2020/dkfz-pm-20-07-Viruses-and-cancer-systematic-overview-published.php. Published February 5, 2020. Accessed February 11, 2020.
 


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