XMRV Found in Prostate Cancer Again, But More Study Is Needed

Zosia Chustecka

October 14, 2010

October 14, 2010 — Another study has found xenotropic murine leukemia virus–related virus (XMRV) in American patients with prostate cancer, but experts are calling for more research into the association between this virus and human disease.

The latest study, published online October 11 in the Journal of Infectious Diseases, is the fourth from the United States to find XMRV in prostate cancer patients. In this case, graduate student Bryan Danielson and colleagues from Baylor College of Medicine, in Houston, Texas, detected the virus in tissue samples from 32 of 144 (22%) prostate cancer patients.

The virus was found in both normal and tumor tissue, which suggests that XMRV infection "may precede and possibly participate in the process of tumorigenesis," the researchers note.

However, 2 previous studies from Germany did not detect XMRV in prostate cancer patients, they point out. "It is possible that XMRV is mostly absent from the European population," they speculate, although they add that different detection techniques could explain the conflicting findings.

"Our data support a hypothesis that XMRV is endemic to North America," they conclude. "However, further investigation into the association of XMTV with prostate cancer and other human disease is needed."

This call for more research into XMRV is taken up in an accompanying editorial, which emphasizes the need for better tests and comments on 2 other studies published at the same time. Both were negative, finding no virus in American patients with chronic fatigue syndrome or infection with HIV or hepatitis C virus, as already reported by Medscape Medical News. However, previous studies have found XMRV in patients with chronic fatigue syndrome, leading to suggestions that such patients should be discouraged from donating blood.

First International Workshop

The need for more research was the overriding sentiment expressed recently at the 1st International Workshop on XMRV, held at the National Institutes of Health (NIH) in Bethesda, Maryland, on September 7 and 8.

At the meeting, researchers presented both positive and negative studies, according to a report in the National Cancer Institute's NCI Cancer Bulletin. In contrast to the findings from the new study, which were also presented at the meeting, another American study, reported by Karen Sfanos, PhD, from Johns Hopkins University, in Baltimore, Maryland, found no virus in more than 800 prostate cancer cases, despite using 2 different detection methods.

Although the virus is detectable in some patients with prostate cancer and chronic fatigue syndrome, there is currently no evidence that it causes disease, the meeting heard. In fact, NIH director Francis Collins, MD, PhD, urged researchers to adopt a healthy skepticism, and emphasized that an association between a virus and a disease is not the same as proving causation.

"People should be questioning the data," Dr. Collins said. "That's what we are taught to do as scientists."

Among the reasons discussed for the conflicting results, the need for reliable and reproducible assays was highlighted as "absolutely essential" by Donald Blair, PhD, from the NCI Division of Cancer Biology.

"The meeting focused people's attention on the need to collaborate and get to the bottom of why results differ, and to understand the biological implications of these differences," Dr. Blair told the NCI Cancer Bulletin.

The researchers have disclosed no relevant financial relationships.

J infect Dis. Published online October 11, 2010. Abstract, Abstract

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