The latest news from the ASCO prostate cancer symposium is that the disease may be caused by a virus. Essentially the cancer may result from chronic inflammation, perhaps as a response to infection via a virus. To see the press release click here.
The findings are particularly poignant for me because my own father died 5 years ago after a brave fight against the disease. I also have several friends whose own Dads are going through the same thing, which is always very sad. While the current news won’t help any of them, it does give hope for the future that other fathers, brothers, uncles and friends could potentially be screened and diagnosed at a much earlier stage, when the chance of surgical cure is significantly higher. Much in the same way that identification of the HPV has led to the virtual eradication of cervical cancer in the western world, so the latest news may lead to a dramatic impact on prostate cancer over the next 10 years, if the findings hold up.
The virus, called XMRV, was found 30 times more frequently in men with prostate cancer who had a particular genetic mutation than in men without this mutation. What’s interesting is that the XMRV virus is similar to a virus that causes leukemia in mice and could be the first evidence that a virus is linked to prostate cancer. According to the researchers at the Cleveland Clinic, damage to a protein that fights viruses, called RNaseL, may increase susceptibility to prostate cancer. Dysfunction may occur when a gene called HPC1 – the gene that produces the RNaseL protein – is mutated and stops functioning normally. As we saw in a previous post, genetic mutations lead to aberrant cell growth because the apoptotic switch is off. Men with this genetic alteration are thought to be more susceptible to prostate cancer.
Researchers from UCSF used a tool called a DNA ViroChip containing the genetic sequences of nearly 1,000 viruses to screen prostate tumor samples from 86 men who had their prostates surgically removed. They then compared the incidence of viral infection between men who had two mutated copies of the HPC1 gene and men with one or no copies of this altered gene. The XMRV virus was found in 45% of the 20 men with two mutated copies of the HPC1 gene, compared with only 1.5% of the 66 men with one copy or no copies of this mutated gene. Interestingly, the same DNA chip process was used to identify the SARS virus 3 years ago, so the concept has a sound basis. It also validates the use of the virus chip to discover previously unknown viruses, and to learn more about viral causes of disease. The power resides in its ability to simultaneously screen for all viruses, without preconceptions or bias. In the case of these prostate tissues, it is unlikely that anyone would have suspected such a virus to be linked to the disease.
In the past, data from other studies have suggested that some prostate cancers could be caused by infection, but no one has shown a link, until now. An epidemiological study is being planned to look at the association between sexual history, personal and family medical history, viral infection, and prostate cancer.
If the XMRV virus does indeed cause prostate cancer, it could potentially become a therapeutic target for drugs or a vaccine. Wow! Stuff like this often ends up in the ASCO plenary sessions as a major finding in the battle against cancer. Watch this space…