In order to track the carrier's journey, the scientists added luciferase ?the protein that makes fireflies glow ?to the AIDS virus. They injected the camouflaged HIV into a vein in the mouse's tail and used a special optical camera to watch the carrier's movement.
"The virus traveled through the animal's bloodstream and homed straight to the cancer cells in the lungs, where the melanoma had migrated," said Chen.
When the researchers held the mouse under the camera, the luciferase illuminated the cancer cells, which glowed through the animal's bones, muscles and fur. The method is non-invasive and does not cause pain or harm to the animal.
Though excited at proving that HIV can be used to target cancer cells, Chen emphasizes that the carrier must be further enhanced for safety and specificity before it can be tested as a gene-therapy method in humans.
"Our next step will be to test whether we can direct therapeutic genes to the precise location where cancer cells reside," Chen said. "This approach offers many potential applications for controlling cancer and other diseases."
"We may be able to boost immune-system surveillance at tumor sites, identify cancer cells' exact location and kill them before they cause damage," he added. "Beyond cancer, it may be possible to correct acquired and genetic diseases where the mutations exert their harmful effects on the body."
Melanoma is a serious form of skin cancer. According to the American Cancer Society, an estimated 59,580 Americans will be diagnosed with melanoma in 2005, and about 7,770 people will die of the disease.