XMRV, or xenotropic murine leukemia virus-related virus, is a recently discovered virus known to infect a small percentage of the population. Although it is not associated with any particular illness, several studies have suggested that there may be a link between XMRV and chronic fatigue syndrome, as well as a link between XMRV and prostate cancer. Neither of these links have been confirmed or accepted by the majority of medical researchers - yet - but it is now possible to state that an XMRV infection may increase the risk of prostate cancer.
In 2006, viral RNA researchers at the Cleveland Clinic and at the University of California, San Francisco, jointly discovered a new gammaretrovirus which they named XMRV. Since 2009, new research into the virus has involved potential links between XMRV and chronic fatigue syndrome. The original researchers, however - as well as some who have followed in their footsteps - were first intrigued by the connection between XMRV and prostate cancer, and only afterwards began to explore the potential connections to chronic fatigue syndrome.
Prostate cancer is the most common type of cancer among men: each year, about 200,000 Americans are diagnosed with prostate cancer, and a little over one-tenth of those men die. This type of tumour begins in the prostate gland and then spreads throughout the body, typically relatively slowly but ultimately causing death. When discovered early, prostate cancer is highly treatable, but previous research into causes and risk factors has been frustratingly inconclusive.
At the same time, however, medical researchers have long known that some viruses cause genetic mutations in targeted cells which then can lead to cancer - which is where XMRV comes in. Other virus connections are already well-established: for instance, it is now well-understood that certain forms of human papillomavirus (HPV), the virus that causes genital warts, can also cause mutations in the female reproductive system leading to cervical cancer. The discoverers of XMRV hoped that they could establish a similar link between XMRV and prostate cancer, in men.
The first studies of the link between XMRV and prostate cancer, according to the National Cancer Institute, did yield some intriguing results. It turned out that, in 300 test subjects, 27% of prostate cancer victims were also known to be infected with XMRV, and that the virus particles in those individuals were present within biopsied samples of the tumours. An Emory University study in Urology, published in spring 2010, added further support to the belief that XMRV played at least some role in predisposing some men to developing prostate cancer.
At the same time, for the moment the link between XMRV and prostate cancer is theoretical and contested, rather than proven. As the National Cancer Institute also notes, follow-up studies in Ireland and Germany also analyzed tumours and failed to find the connection first pointed to in America. More cold water was thrown on the theory as a result of the fact that, at least for the moment, infection with XMRV does not appear to correlate with a particular genetic defect which the original researchers believed it might cause, in a gene called the RNASEL gene (which plays a role in the body's anti-viral immune system). Further studies should establish whether or not there is a link between XMRV and prostate cancer, and, if so, the nature of that link.
For the moment, however, unfortunately there is little that men in the general public can do one way or the other. There are no common tests for XMRV, its prevalence in the general population is unknown, its method of transmission is also unknown (although it may be spread through saliva and respiratory secretions, and possibly also through sexual contact), and there has been little research into treating it, although antiretroviral medications (the same class used to combat HIV) appear effective.
- Sources and More Information -
National Cancer Institute. "XMRV: Questions and Answers."
Science Daily. "Correlation Between XMRV and Prostate Cancer."