Th scientist who started the ball rolling on XMRV:
A new human retrovirus associated with prostate cancer
" . . .the discovery of XMRV as a new retrovirus of humans reinforces the idea that other human diseases may involve infections by viruses (or other infectious agents) either known or previously unknown." A new human retrovirus associated with prostate cancer
XMRV is present in malignant prostatic epithelium and is associated with prostate cancer, especially high-grade tumors
- Robert Schlaberga,
- Daniel J. Choeb,
- Kristy R. Browna,
- Harshwardhan M. Thakerb and
- Ila R. Singha
"Xenotropic murine leukemia virus–related virus (XMRV) was recently discovered in human prostate cancers and is the first gammaretrovirus known to infect humans. While gammaretroviruses have well-characterized oncogenic effects in animals, they have not been shown to cause human cancers. We provide experimental evidence that XMRV is indeed a gammaretrovirus with protein composition and particle ultrastructure highly similar to Moloney murine leukemia virus (MoMLV), another gammaretrovirus. We analyzed 334 consecutive prostate resection specimens, using a quantitative PCR assay and immunohistochemistry (IHC) with an anti-XMRV specific antiserum. We found XMRV DNA in 6% and XMRV protein expression in 23% of prostate cancers. XMRV proteins were expressed primarily in malignant epithelial cells, suggesting that retroviral infection may be directly linked to tumorigenesis. XMRV infection was associated with prostate cancer, especially higher-grade cancers. We found XMRV infection to be independent of a common polymorphism in the RNASEL gene, unlike results previously reported. This finding increases the population at risk for XMRV infection from only those homozygous for the RNASEL variant to all individuals. Our observations provide evidence for an association of XMRV with malignant cells and with more aggressive tumors."
Caution Urged on XMRV Implications
The following text is from a Howard Hughes Medical Institute Press release: Ganem cautioned that any link between XMRV and prostate cancer is tenuous at best. "First, the genetic variant we studied occurs in familial clusters that constitute only a very small sliver of prostate cancers," he said. "And secondly, there are many reasons to believe that the virus might not relate to prostate cancer."
For example, he pointed out, analysis of prostate tissue by Silverman and his colleagues indicated that the virus appears only in a small percentage of connective tissue cells, called stromal cells, rather than in the tumors themselves. "So, one interpretation could be that the infection is entirely incidental to prostate cancer," said Ganem. "The patients with RNASEL mutations may be more likely to get the infection or perhaps less likely to clear it. Clearly XMRV is not a classic oncogenic virus."
Nevertheless, said Ganem, an indirect link to cancer cannot be ruled out, since "in cancer research these days, there is a lot of interest in the stroma as the soil in which cancer arises." He added that the chronic inflammation from infection of stromal tissues may play a role in triggering such cancers. http://www.biologynews.net/archives/2006/04/01/newhumanretrovirusoriginatedin_mice.html
Is XMRV a commensal infection in prostate cancer and chronic fatigue syndrome?
Human RNA "Rumor" Viruses: the Search for Novel Human Retroviruses in Chronic Disease
"Alternatively, XMRV may simply represent a commensal infection that has found a particular niche due to defective RNase L function in these patients."
--Cécile Voisset, Robin A. Weiss, and David J. Griffiths
First Evidence Of Virus In Malignant Prostate Cells: XMRV Retrovirus Linked To More Aggressive Tumors
"In a finding with potentially major implications for identifying a viral cause of prostate cancer, researchers at the University of Utah and Columbia University medical schools have reported that 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." http://www.sciencedaily.com/releases/2009/09/090907162310.htm
"A retrovirus known to cause leukemia and cancerous tumors in animals has for the first time been found in malignant prostate cells -- raising the intriguing question of its role in prostate cancer. The retrovirus -- called Xenotropic murine leukemia virus-related virus, or XMRV -- was found in 27 percent of prostate cancers, compared to 6 percent of benign tissues examined by University of Utah and Columbia University researchers."