For many men, the urinary tract is home to a organism called the human BK virus. Usually, the virus lives quietly in the kidneys without causing problems. But in people with a depressed immune system the virus can cause serious kidney disease and new research by scientists at the University of Michigan Medical School suggests that this common virus also may play a role in prostate cancer. Their research appears in the journal Oncogene. A research team led by Michael J. Imperiale have found DNA and proteins from the BK virus in prostate tissue with abnormal cell changes. Called atrophic lesions, these changes can be the first step in a series of progressive cell changes leading to prostate cancer.
"Other studies have detected DNA from the BK virus in prostate cancer cells, but this study is the first to pinpoint the location of viral protein expression to one precursor stage in the development of prostate cancer," Imperiale says.
"The development of cancer is a multi-step process," Imperiale adds. "Expression of BK viral protein may be just one step among several genetic and environmental factors. We are not saying that BK virus causes prostate cancer, but our results do suggest that the virus plays a role in the transition from normal to uncontrolled growth of prostate cells."
BK is a human virus in the polyomavirus family. It was first discovered in kidney transplant patients who take immunosuppressive drugs to prevent their body from rejecting a new kidney. Scientists have found BK virus in several types of human cancer and it has been shown to cause kidney tumors in laboratory mice. While the virus has received scientific study for its role in kidney disease, only a handful of scientists are studying a possible connection to cancer.
"Atrophic lesions comprise a spectrum of architectural and cytological differences in the appearance of epithelial cells lining the glands in the prostate," says Rajal B. Shah, co-author of the study. "Several recent studies have demonstrated that they potentially represent the first stage in a series of progressive cell changes, which can lead to prostate cancer."
Imperiale's working hypothesis is that the BK virus infects epithelial cells in the prostate and transforms them into atrophic lesions through TAg expression. This produces an area of uncontrolled cell growth, which � if circumstances are right � can eventually develop into prostate cancer. It's possible that prostate cancer may have something in common with cervical cancer, which is caused by a different virus � the human papillomavirus.
"Papillomavirus makes proteins with the same function as T antigen," Imperiale says. "It's a logical possibility that a similar mechanism occurs in at least some cases of prostate cancer, but much additional research will be needed before we can know for sure."
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