Virus could be cause of some prostate cancers
Published Monday, September 7, 2009 10:05PM EDT
A type of virus that causes cancer in animals has been found in human prostate cancer cells, reports a new study. It's a finding that could one day lead to new diagnostic tests, treatments and even a vaccine.
The researchers, based at the University of Utah and Columbia University medical schools, say this is the first time the virus -- XMRV (Xenotropic murine leukemia virus-related virus) -- has been found in malignant cells in humans.
"We found that XMRV was present in 27 per cent of prostate cancers we examined and that it was associated with more aggressive tumours," senior study author Dr. Ila R. Singh, an associate professor of pathology at the University of Utah, said in a statement.
"We still don't know that this virus causes cancer in people, but that is an important question we're going to investigate."
The findings are published in the online edition of the Proceedings of the National Academy of Sciences.
Prostate cancer is the most common form of cancer among Canadian men outside of non-melanoma skin cancer, according to the Canadian Cancer Society. The agency estimates that more than 25,000 men will be diagnosed with the disease in 2009, and 4,400 will die from it.
While cases of prostate cancer have been on the rise in Canada since 1980, death rates have increased much more slowly and began to decline in the mid-1990s.
Previous research has determined that viruses cause cancer of the cervix, connective tissue (known as sarcomas), the immune system (lymphoma) and other organs.
"Viruses are known to cause other human cancers For example, human papilloma virus causes cervical cancer in women (and) hepatitis B and C cause liver cancer," Singh said.
For the study, Singh and her colleagues analyzed more than 200 human prostate cancers and compared them to more than 100 non-cancerous prostate tissue samples.
Proteins from the virus were found almost exclusively in the malignant cells, which suggests a link between being infected with the virus and developing tumours.
And because the researchers found that a genetic mutation does not enhance susceptibility to XMRV infection, then the public at large may be at risk of contracting the virus, rather than just a small number of people who carry the mutation.
The study also confirmed previous research that XMRV is a gammaretrovirus, a simple retrovirus that is known to cause cancer in animals but has not yet been found to cause cancer in humans.
Retroviruses insert a copy of their DNA intro the chromosomes of cells they infect, which can occur next to a gene that regulates cell growth. This can cause cells to grow so rapidly, they eventually develop into cancer.
The researchers say their study has led to more questions than answers. What is still unclear is whether the virus infects women, if it is sexually transmitted, how prevalent it is in society and whether it causes cancers elsewhere in the body.
"We have many questions right now," Singh said, "and we believe this merits further investigation."