It's possible that the most severe forms of prostate cancer are caused by a virus that might be sexually transmitted, according to a new study that will be published in the Proceedings of the National Academy of Sciences this week. Researchers checked for the virus in more than 200 prostate cancer patients and found the virus in 27 percent of the men; those with the most aggressive tumors were most likely to have the virus. While the researchers haven't proved causation, they note that viruses
are known to cause a variety of human cancers. Hepatitis viruses, for example, cause liver cancer, while human papilloma virus causes cervical cancer in women and anal and penile cancer in men [Los Angeles Times].
The virus, known as XMRV, belongs to a family of viruses that has previously been shown to cause leukemia in lab animals. Like the HIV virus, XMRV is a retrovirus,
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