Link between viral infection and colorectal cancer. Can viruses increase risk for colon cancer? Can a vaccine reduce colon cancer risk? Leading colorectal cancer genetics expert discusses colon cancer diagnosis and treatment. Much research has focused on genetic mutations leading to colorectal cancer development. Dr. Anton Titov, MD. We have just discussed the role of inflammation in cancer development. Inflammation increases the risks for gastrointestinal cancers. There is another important risk factor for cancer. It is infection. You and your colleagues have investigated potential role of viral infections in colorectal cancer development. What is currently known about the potential role of viruses in colorectal cancer development? What are the controversies and unanswered questions? Dr. C. Richard Boland, MD. There is no question that Helicobacter pylori infection in the stomach is involved with a lot of stomach cancer. So we were wondering if there was something similar to that infection in the colon that was causing colon cancer. And in the mid-1990s we hypothesized that JC virus might be an infectious agent which contributes to colon cancer formation. JC virus is a polyoma virus. Maybe JC virus infection would explain differences in colon cancer from one population to another. We used very sensitive PCR-based techniques and found JC virus in most large bowels that we examined. Then some other laboratories tried to reproduce these results, but they could not reproduce them. But other laboratories reproduced our results about JC virus and were able to confirm our data too. All findings were very similar. T antigen is the transforming factor of JC virus. We found that T antigen was expressed in colon tissues – so JC Virus was a very likely culprit. Because JC virus encodes incredibly potent transforming genes that turn cells into cancers. The T antigen binds DNA and breaks it, and inactivates p53 and the retinoblastoma proteins. T antigen of JC virus is one of the most useful laboratory probes to create cancer. Dr. C. Richard Boland, MD. To make a long story short, we’ve gone through about 20 years of doing experimentation, and when we finally had much better techniques to quantify JC virus in colon cancers and in a normal colon, it just didn’t seem to be present in enough of the colons. I am now not so certain that JC virus really plays an active role in colon cancer. The problem is that most people have antibodies to JC virus – we have all been exposed to it. So it seemed like it was a plausible contributing factor to colon cancer. We looked at differences in the immune response to T antigen of JC virus among people who had colon cancers and who did not. There was not a substantial difference. So JC virus and colon cancer link was an idea that we had for a while. But it’s really not an idea that I am very enthusiastic about now. Because the data have not supported what I thought the role for JC virus in colon cancer was in the very beginning. But it’s a very interesting hypothesis. Because if you could identify certain viral infection in cancer, you can invent a vaccine against that cancer. That was the idea from the very beginning. We’d love to come up with just the perfect vaccine to get rid of some kind of cancer. Like getting rid of smoking. Dr. Anton Titov, MD.
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