From Nature:
Researchers have found evidence that two common viruses may be lurking behind some cases of lung cancer: human papilloma virus (HPV), already recognized as a cause of cervical cancer, and the measles virus. The results, which will be presented today at the European Lung Cancer Conference in Geneva, Switzerland, are preliminary: while viruses have been found associated with lung tumours, there is no direct evidence that the viruses are actually causing the cancer. But the notion that a virus could contribute to some cases of the disease is a plausible one, says Denise Galloway, a virologist at the Fred Hutchinson Cancer Research Center in Seattle, Washington, who was not affiliated with the new studies.
As much as 20% of the world’s cancers have been linked to infections. In addition to the connection between HPVs and cervical cancer, chronic infections by hepatitis-B and -C viruses contribute to liver cancer, and the bacterium Helicobacter pylori has been associated with stomach cancer. In February, researchers reported viral genome sequences found in an aggressive form of skin cancer called Merkel cell carcinoma, although it remains to be seen precisely how the virus contributes to skin cancer, if at all. And some have proposed that a virus similar to the ‘mouse mammary tumor virus’ — which causes breast cancer in mice — could also be associated with breast cancer in humans.
More here.