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.
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