Could a virus cause prostate cancer?

http://latimesblogs.latimes.com/booster_shots/2009/09/could-a-virus-cause-prostate

Could a virus cause prostate cancer?
September 7, 2009 | 12:40 pm

Utah researchers have found a mouse cancer virus in many human patients
with prostate cancer, suggesting that the virus may play a role in the
onset of the disease and in the development of more aggressive forms. If
their findings can be validated, it might provide a way to distinguish
fast-growing tumors that require therapy from the slow-growing forms that
can be safely ignored for many years.

Viruses are known to cause a variety of human cancers. Hepatitis viruses,
for example, cause liver cancer, while human papilloma virus causes
cervical cancer in women and anal and penile cancer in men. The mouse
mammary tumor virus has been found in many human breast cancers, but
researchers are not sure what role, if any, it plays in development of the
disease.

Dr. Ila R. Singh of the University of Utah and her colleagues have been
studying a mouse virus called xenotropic murine leukemia virus-related
virus, or XMRV. They, as well as researchers from UC San Francisco, had
previously reported finding the virus in some human prostate cancers, but
had not looked for it in normal prostate tissues.

In the new study, they looked for the virus in 200 human prostate cancers
and in 100 samples of healthy prostate tissue. They reported today in the
Proceedings of the National Academy of Sciences that they found the virus
in 27% of the cancerous tissues, but in only 6% of the healthy tissues.
The virus was most likely to be present in tumors that are considered more
aggressive on the Gleason scale of malignancy.

A sequence analysis of the virus showed that it is a gammaretrovirus, one
of a family of viruses that are known to cause leukemias and other cancers
in animals, but that have not yet been shown to do so in humans. The
gammaretroviruses insert their genetic information into the DNA of cells
they infect. When this insertion occurs in the wrong position, it can
induce the host cell to begin replicating out of control, producing a
tumor.

The researchers found that XMRV replicates easily in cultured human
prostate tissue, but not in other types of human tissues. But they have
not shown that the virus causes tumors to grow. There are also many other
unanswered questions, such as whether the virus infects women, whether it
is sexually transmitted, and how prevalent it is in the human population.

If the virus could be linked to prostate tumors, it might open the door to
new treatments and to prevention. A vaccine against the virus might
prevent many cases of prostate cancer, just as the human papilloma virus
vaccines prevent cervical cancer. The need for new approaches to prostate
cancer is clear: It is second only to skin cancer as the most common form
of cancer in males, affecting more than 190,000 American men each year and
killing 27,000. Any improvement would be gratefully accepted.

-- Thomas H. Maugh II


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