Cancer is simply uncontrolled growth of cells, like this image of cancerous cells in a cervix.

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Vesicular Stomatitis Virus

With some types of cancer, surgery can be a dangerous proposition. Not least among these is brain cancer. The fragility of the organ itself and the risk and difficulty getting to tumors in inner regions of the brain can make surgery impossible. Chemotherapy and blasting the infected area with radiation may be the only choices in treating brain cancer. These treatments generally prolong the life of a brain cancer patient for a few months.

Some researchers have had a stroke of brilliance: Why not fight fire with fire?

Cancer is, essentially, simply uncontrolled growth of cells. Cells are affected by viruses. Could a virus seek out cancerous cells? The answer, as Yale researchers discovered, is yes. The Yale researchers, led by Dr. Anthony van den Pol, used an existing virus related to rabies, the vesicular stomatitis virus -- as a weapon against cancerous cells.

In laboratory tests, Yale researchers used mice infected with brain cancer and grafted non-cancerous human brain tissue to the mice's brains. The cancerous cells were tagged with fluorescent proteins, as was the virus they injected into the mice's tails. This gave researchers a clear view of the process; the virus attacked the cancerous cells, killing the tumor within three days [source: Society for Neuroscience].

The Yale studies also showed another important aspect. As it worked its way through the brains of the mice, the virus killed only cancerous cells and left non-cancerous cells of the mice's own tissue as well as that grafted from human specimens intact.

Van den Pol and his group believe that the virus was able to reach the tumors located deep within the brains of the mice through leaky blood vessels in the tumors. This is especially significant, because of the blood-brain barrier, which prevents even normal human antibodies from reaching the brain. The vesicular stomatitis virus, on the other hand, was able to pass through this barrier.

To achieve optimum results from a viral treatment, the immune system must ostensibly be suppressed. After all, to a natural antibody, a virus is a virus, even when it's meant to perform a beneficial function. This leads to the question, what happens when the virus is done with its work killing tumors? It's possible that the virus has an appetite for cancerous cells, but will turn to healthy tissue in the absence of a cancerous alternative.

Determining that is the next step, says van den Pol.

Another team of researchers in Los Angeles have also concluded that viruses can be useful in battling brain cancer. These researchers are taking a different approach -- boosting the body's natural immune system. Read about this treatment on the next page.