A harmless version of a major killer, the HIV virus, is being used to hunt down malignant melanoma cancer cells in mice, researchers say.

Scientists at the University of California, Los Angeles AIDS Institute used a version of HIV lacking key components that cause AIDS. This disabled form of the virus was able to spread through the body and infect cells, but without causing disease, they explained.

Next, the researchers stripped off HIV’s viral coat and reprogrammed the virus to recognize and attach to P-glycoproteins, molecules located on the surface of many cancer cells.

“P-glycoproteins cause big problems by making the cell resistant to chemotherapy,” institute director Irvin S.Y. Chen said in a prepared statement. “They act like soccer goalies and punt therapeutic drugs out of the cancer cell. This prevents the drug from taking effect and allows the tumor to continue growing unchecked.”

The researchers also loaded the altered HIV with a fluorescent protein, the same protein that makes fireflies glow. Using a special optical camera, they used this fluorescence to track the virus’ movements after injection into the mice.

“The virus traveled through the animal’s bloodstream and homed straight to the cancer cells in the lungs, where the melanoma had migrated,” Chen said.

The study appears in the Feb. 13 online edition of the journal Nature Medicine.

“For the past 20 years, gene therapy has been hampered by the lack of a good carrier for therapeutic genes that can travel through the blood and aim itself at a precise location, thereby minimizing harmful side effects,” Chen said. “Our approach proves that it is possible to develop an effective carrier and reprogram it to target specific cells in the body.”

He cautioned, however, that much more research is required before this approach can be tested as a gene therapy method in humans.