Scientists have found stronger evidence linking prostate cancer with a viral infection.
Back in 2006, researchers announced that they had identified, in cancerous human prostate tissue, traces of a virus called xenotropic murine leukaemia virus-related virus (XMRV), which is a relative of a virus normally found in mice. But because only malignant tissue was scrutinised in this study it wasn't clear whether the agent was genuinely related to the disease, or whether it was a red herring.
Now, writing in PNAS, Columbia University researcher Robert Schlaberg and his colleagues have taken up the baton and examined over 300 prostate specimens, including both cancerous and benign samples. They used sensitive genetic techniques to look for viral DNA in the specimens. Amongst the cancers, 25% tested positive for XMRV compared with just 4% of the control (benign) tissues; and looking under the microscope the team found that the cells testing positive for XMRV in a sample also tended to be the malignant ones. Furthermore, tumours that contained XMRV also tended to be more aggressive, higher grade cancers.
This suggests that the virus might play a role in the devlopment of prostate cancer, although the researchers as yet don't know for sure that the virus is actually causing cancers. It could be that cancer cells, because they grow much more rapidly than normal, are more susceptible to infection by the virus compared with healthy tissue.
Also, the scientists acknowledge that, as yet, there's no clear path for how the virus could be causing cells to become cancerous as the virus itself doesn't contain any genes, known as oncogenes, that are known to cause cells to divide uncontrollably; that said it does contain a number of genes with poorly-understood functions.
More work is therefore required to determine the significance of this agent, but it's mere presence might also serve as a useful marker of prostate cancer, and the association with higher-grade tumours could also provide valuable prognostic information for doctors.