Recently discovered virus linked to aggressive prostate tumors
(6 October 2009: VIDYYA MEDICAL NEWS SERVICE) -- A previously unknown virus was discovered in tumors from men with prostate cancer in 2006, but at the time it was not clear whether the virus played a role in the disease. That question remains unanswered, but a new report shows that the virus, called xenotropic murine leukemia virus-related virus (XMRV), is present in malignant prostate cells and is more commonly found in men with aggressive tumors.
A survey of more than 300 prostate tissue samples showed that the virus was present in 27 percent of the tumor samples and 6 percent of the benign control samples. Reporting their findings last week in the Proceedings of the National Academies of Sciences (PNAS), the researchers also confirmed the initial classification of the virus as a type of gammaretrovirus. These pathogens can cause cancer in animals, but they have not yet been shown to cause cancer in people.
“The most important question now is does this virus cause cancer or not, and there are a few different ways to answer this question,” said lead investigator Dr. Ila Singh of the University of Utah. Her group is looking at prostate cancers to see whether viral DNA is integrated near human genes involved in growth. If so, the viral DNA may have activated the growth-promoting genes improperly and contributed to tumors.
If the viral DNA is positioned next to the same growth-promoting gene in each of a tumor’s cells, indicating the outgrowth of a clone, then the tumor could have originated from a single infected cell and this would be strong evidence of causation, Dr. Singh said.
The researchers are also investigating how the virus might be transmitted from person to person by analyzing seminal and cervical fluids and developing a blood test to check for the virus. If the virus does play a role in cancer, the most productive strategy for combating the problem would be to prevent infection, said Dr. Singh.
XMRV could potentially be a marker for identifying patients with aggressive forms of the disease who require appropriate treatment, she noted. Currently, there is no reliable way at the time of diagnosis to distinguish aggressive tumors from indolent forms of the cancer that may never cause harm.
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