The viral connection to several forms of cancer has for the first time been found in prostate cancer, a discovery that could lead to better diagnostic tests, vaccines and therapy for the second-most common form of the disease in men.

According to findings by researchers at the University of Utah and Columbia University, published in Friday's edition of the online journal Proceedings of the National Academy of Sciences, a type of virus known to cause leukemia and sarcomas in animals has been found for the first time in malignant human prostate cancer cells.

If further investigation proves the virus — Xenotropic murine leukemia virus-related virus — causes prostate cancer in males, it would aid in developing diagnostic tests, vaccines and therapies for treating the cancer.

Prostate cancer is diagnosed in 200,000 American men each year. It is the second-most common form of the disease, next to skin cancer.

About a third of the men diagnosed will have slow-moving tumors that many will choose to live with rather than treat, according to recent research published by the U., Harvard University and other medical schools here and in England.

The most serious, aggressively developing tumors were implicated in the U. research.

"(The virus) was present in 27 percent of prostate cancers we examined, and it was associated with more aggressive tumors," said Dr. Ila R. Singh, associate professor of pathology at the U. and the study's senior author. "We still don't know that this virus causes cancer in people, but that is an important question we're going to investigate."

In another important finding of the study, Singh and her colleagues also showed that susceptibility to infection is not enhanced by a genetic mutation, as was previously reported. If that were correct, only the 10 percent of the population who carry the mutated gene would be at risk for infection with virus. But Singh found no connection between the virus and the mutation, meaning the risk for infection may extend to the population at large.

While the study answers important questions about the virus, it also raises a number of other questions, such as whether the virus infects women, is sexually transmitted, how prevalent it is in the general population, and whether it causes cancers in tissues other than the prostate.

Viruses have been shown to cause cancer of the cervix, connective tissues (sarcomas), immune system (lymphoma) and other organs. If the retrovirus is shown to cause prostate cancer, this could have important implications for preventing viral transmission and for developing vaccines to prevent infection in people.

"We have many questions right now," Singh said, "and we believe this merits further investigation."