March 10, 2008 -- Curing a disease by causing another one seems counter-intuitive, but that's just what scientists at Yale University have done.
Specifically, they have modified a virus and injected it into mice with several kinds of inoperable brain cancer. Three days later, the tumors were gone.
The research, which builds on previous attempts to use viruses to treat cancer, could eventually treat otherwise fatal brain tumors in people, as well as other forms of cancer. While a human treatment is still years away and subject to federal approval, a tumor-killing virus could be a last-resort try at saving lives.
"The brain cancers we look at are very nasty," said Anthony Van den Pol, a scientist at Yale University and a study author. "This virus is pretty good at killing all of the tumor cells."
While surgery or other treatments can be used for some brains cancers, many tumors are inoperable. And even in the case of treatable tumors, it takes just a few surviving cells to cause the re-growth of new tumors, years later.
For the new treatment, the researchers used a virus related to rabies called vesicular stomatitis virus (VSV). Endemic to Central America, the virus causes mild, cold-like symptoms in humans and is based on single-stranded RNA instead of the doubled-up DNA.
The virus causes an active infection, rather than a harmless immune reaction as a typical vaccine would. Its infectiousness will likely limit its use as a therapy, the researchers admit.
"The use of a self-replicating virus to treat cancer might be a last-ditch attempt after other treatments haven't worked," said Van den Pol.
The exact mechanism the virus uses to track down and destroy cancer cells is still unknown. Van den Pol suspects the absence of interferon, an antiviral chemical produced by normal cells but not cancer cells, allows the virus to infect and replicate inside tumor cells.
Using viruses to destroy tumors is not a new idea. Researchers at the Mayo Clinic have been working on virus-based cancer treatments for years. Two years ago a team lead by Steven Forsyth at the University of Calgary used VSV against brain tumors and had similar results.
While the Yale researchers focused on the worst kinds of brain tumors, scientists speculate that an adapted virus could attack other kinds of cancer and are hopeful that it will eventually be approved for use in humans.
"You are dealing with 25,000 patients each year who have no hope," said Harald Sontheimer, a neurobiologist at the University of Alabama at Birmingham who was not involved in the research. "Radiation prolongs life some, surgery does somewhat, and chemotherapy is not effective. Any research that takes a new tack is exciting."
The research is published in the Feb. 20, 2008 issue of the Journal of Neuroscience.
The research is published in the Feb. 20, 2008 issue of the Journal of Neuroscience.
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