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vesicular stomatitis virus

Virus versus Cancer

When people think of the Rabies virus they will either think of rabid animals or a more recent The Office episode from America. One particular member of the Rhabdoviridae family of viruses is vesicular stomatitis virus, and it affects insects and mammals, including cattle. 

But would you be surprised to learn that vesicular stomatitis virus (VSV) is also being used to treat cancer?

Anthony Van den Pol, lead researcher and professor of neurosurgery and neurobiology at Yale, along with his colleagues, has been searching for a virus that will target brain cancer. What he has found is that VSV effectively kills off brain tumors in mice, and leaves healthy cells intact. What’s really great about this is that VSV is able to self-replicate.

“A metastasizing tumor is fairly mobile, and a surgeon’s knife can’t get out all of the cells,” says Van den Pol. “A virus might be able to do that, because as a virus kills a tumor cell, it could also replicate, and you could end up with a therapy that’s self-amplifying.”

This is not the first study to look at viruses as a potential ally in the fight against cancer. Researchers at the famed Mayo Clinic are engineering a measles virus that could one day combat multiple myeloma (a cancer of the bone marrow), and another group is looking at herpes and polio-related viruses as another attack against brain cancer.

Van den Pol has been trying for six years, and over that period of time he and his colleagues have continuously seen VSV come out “at the top of the heap” in test after test. Their most recent discovery has been published in a recent issue of the Journal of Neuroscience.

The study used color trackers to indicate what took place within the brains of the mice. The team transplanted glioblastoma--the most common and aggressive form of human brain cancer--into the brains of the mice. However prior to transplantation, the researchers genetically engineered the tumor cells to be seen as a red marker. Conversely, a green marker was placed in the VSV cells, so that when viewed under laser microscopy scans they would be able to monitor what did what to whom.

Within only a few days, the researchers saw that the green virus cells had made their way to the brain and infiltrated the red tumor cells, causing the cells to start to turn green, swell up, and eventually pop like a balloon.

“It’s like a balloon,” says Van den Pol. “If you keep blowing air into it, it explodes. The carcass is still there, but it’s no longer a balloon. And these are basically dead cells, unable to divide anymore or survive as intact cells.”

While this is indeed a massive breakthrough, there are a few caveats that must first be worked out. First of all is that no one is sure what the VSV virus will do to the brain over the long term. So far the mice have been sacrificed soon after the virus has worked its way in to the tumors so long term effects are uncertain. In addition, the mice used are immuno-compromised mice. In other words, they have a very weakened systemic immune system so that the human tumor cells can be introduced.

“What usually happens with most of these tests is, you have a nice animal model where the virus spreads through the tumor,” says Samuel Rabkin, associate virologist in the department of neurosurgery at Massachusetts General Hospital. “In more-realistic models, the host may have a response to the virus that limits the effect.”

Needless to say, a fantastic breakthrough that may one day rid the world of a massive killer.