February 24, 2006

Virus May Cause Prostate Cancer, Study Hints

NEW YORK (Reuters Health) - A newly identified virus, tentatively called XMRV, seems to be associated with the development of prostate cancer in genetically susceptible men, researchers report.

XMRV is closely related to a virus that causes leukemia in mice and is a "newly identified infectious agent in humans," Dr. Eric Klein of the Cleveland Clinic said in a statement.

"While more research is needed to confirm our findings, this could be the first evidence that a virus is linked to prostate cancer," he added.

Damage to an antiviral protein called RNaseL, may increase susceptibility to prostate cancer, Klein and colleagues note. Such dysfunction may occur when a gene called HPC1, which produces RNaseL, is mutated and stops functioning normally. Men with these genetic alterations are more prone to prostate cancer.

Klein's group explored the possibility that a viral infection might contribute to prostate cancer in men with HPC1 mutations that impair function of RNaseL.

They used a DNA ViroChip containing the genetic sequences of nearly 5,000 viruses to screen prostate tumor samples from 86 men who had their prostates removed. They compared the incidence of viral infection between men who had two mutated copies of HPC1 gene and men with one or no mutated copies of this gene.

Klein and colleagues found XMRV in 45 percent of the 20 men with two mutated copies of the HPC1 gene but in only 1.5 percent of the 66 other men.

XMRV could be sexually transmitted. It's possible that infection leads to chronic inflammation of the prostate leading ultimately to cancer, the researchers theorize, analogous to the way human papillomavirus (HPV) can trigger cervical cancer.

The researchers are planning a comprehensive "epidemiological" study to look at the association between sexual history, personal and family medical history, viral infection, and prostate cancer.

If the XMRV virus does cause prostate cancer, it could be a therapeutic target for drugs or a vaccine.

The findings were presented Friday morning in San Francisco at the 2006 Prostate Cancer Symposium, co-sponsored by the American Society of Clinical Oncology, the American Society for Therapeutic Radiology and Oncology, the Prostate Cancer Foundation, and the Society of Urologic Oncology.