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.
DeRisi observed that "it may be that men who are so-called RNASEL-mutant are just more susceptible to viruses in general, and this susceptibility has little to do with their cancer. Nevertheless, the fact that this virus is found in tumor tissue and that it is a new virus and the first of its kind ever documented in humans is an intriguing finding that demands to be followed up. This initial finding raises many questions. For example, what is the route of transmission? How is the virus passed from person to person? And are people the natural reservoir of this virus, or is it some other organism?"
DeRisi and Ganem said they are planning studies to explore whether XMRV is restricted to prostate cancers or whether it is more widespread in the body and in other segments of the human population. To answer such questions, the researchers are developing a blood test that can be used in epidemiological studies.