Is the cure for cancer a 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.

While the Yale researchers have turned to a virus to act as an agent of destruction for tumors within the brain, scientists at Cedars-Sinai Medical Center in Los Angeles are taking a different tack. The team is using them to make the body's immune system more effective.

The Cedars-Sinai group used a virus stripped of its harmful properties, essentially turning it into a transport vehicle for two proteins. The injected virus carries these proteins to the tumor. One of these proteins identifies the location of the cancer. These cells serve as antigen-presenters -- they're the burglar alarm for your body's immune system.

The other protein -- a type of herpes simplex -- acts as a time bomb. When it's combined with the drug gancyclovir, the herpes destroys cancerous cells.

As the herpes protein kills the tumors, the dendrites clean up the mess. Discovering antigens, these cells alert the immune system. The immune system then begins to annihilate the tumors [source: Cedars-Sinai Medical Center]. The immune cells can't do their jobs unless they are aware that there's a problem in the brain, due to the blood-brain barrier. The Cedars-Sinai researchers may have figured out how to let them know.

The Cedars-Sinai group focused their efforts on glioblastoma multiforme (GBM), a deadly and common form of brain cancer. Patients have generally a year or less to live after they develop GBM, and traditional methods of treatment can be ineffective [source: Neurological Society of India]. GBM easily metastasizes -- meaning the cancer spreads beyond the original location of the disease. This makes the cancer much harder to treat since the area has spread and removing all of the tumors surgically increases in difficulty.

But using viruses as protein deliverers has shown promise in testing on lab rats. Rats with GBM have shown a survival rate of 70 percent, without any significant unwanted effects [source: Cedars-Sinai]. There's also an added bonus: The therapy appears to have a residual effect, successfully defending against later tumor attacks.

Meanwhile, in Cincinnati, cancer researchers at Cincinnati Children's Hospital have also caught the viral treatment "bug." These scientists are also using a type of herpes simplex, but their version includes a companion gene. When it's introduced, this gene instructs human proteins to restrict uncontrolled cell growth. This viral therapy is called rQT3.

The injected virus goes after the cancerous cells, just as the virus in the Yale study. But the gene attached to the virus signals the protein TIMP3, which works mainly to reduce the construction of blood vessels within the tumor, which support its growth by feeding it. The therapy essentially attacks the tumor and fends off any reinforcements that may help it bounce back.

All of these therapies have shown promise in labs, and the Cedars-Sinai study was planned to begin testing on humans in 2008. It's ironic, though, that what we've for so long considered our enemy -- viruses -- may prove to be our most valuable ally in the fight against cancer.

For more information on cancer and other related topics, visit the next page.