New research strengthens a possible link between a recently identified human retrovirus and prostate cancer—though a causal connection is far from certain. Scientists at the University of Utah in Salt Lake found evidence of the xenotropic murine leukemia virus–related virus, XMRV, in 27% of 334 prostate cancer biopsies. XMRV was associated with the aggressive form of the disease (Proc. Natl. Acad. Sci. USA doi:10.1073/pnas.0906922106; 2009).

Researchers say that this discovery might have implications for prevention and treatment. “If further connections are found, then preventing viral infection would be a first step,” says lead author on the new paper Ila Singh of the University of Utah. She adds that a vaccine for XMRV could be developed, and antiretroviral drugs could be tested to treat infection.

XMRV is a member of the gamma retrovirus family, known to produce cancer in animals, but not in humans (Proc. Natl. Acad. Sci. USA 104, 1449–1450; 2007). It was first identified two years ago by Robert Silverman of the Cleveland Clinic in Ohio and his colleagues at the University of San Francisco in California (PLoS Pathog. 2, e25; 2006).

“The new finding of XMRV in malignant epithelial cells suggests it may be involved in prostate cancer development, and not just a passenger virus, although that remains to be proven,” says Silverman, who was not involved in the new study.

If a causal connection is found in future research, XMRV might serve as a useful marker to identify cases that would benefit from treatment, as opposed to those that grow very slowly and play no part in morbidity or mortality, says Singh.

Others recently found another infectious disease connection to prostate cancer. In a study of 673 subjects, scientists at the Harvard University School of Public Health found that men that had been infected with the sexually transmitted pathogen Trichomonas vaginalis had a more than twofold higher risk of aggressive prostate cancer (J. Natl. Cancer Inst. doi:10.1093/jnci/djp306; 2009).