An estimated 60,000 Americans will be diagnosed with melanoma this year. Another 8,000 people will die from the disease, according to the American Cancer Society. To fight that dreaded disease, for 20 years researchers have unsuccessfully tried to find a good carrier to transport therapeutic genes through the bloodstream without causing harmful side effects. The latest discovery indicates that the cure for cancer may come from the most unlikely source, another one of the world's biggest killers--AIDS.

A study by a team of scientists at the University of California, Los Angeles has revealed that the AIDS virus HIV can be modified to target melanoma, or skin cancer, cells in mice.

It turns out that the same thing that makes HIV incurable--its ability to effectively seek out and destroy T-cells in the immune system--can be exploited to do the same to cancer cells.

Reprogramming the virus into a cancer-seeking missile is a two-part process. First, scientists strip HIV of the viral pieces that cause AIDS, rendering it impotent. Then they combine it with sindbis, another virus that usually infects birds and insects. The HIV hybrid will then target P-glycoproteins, molecules that sit on the surface of cancer cells.

"P-glycoproteins cause big problems by making the cell resistant to chemotherapy," said Irvin Chen, PhD, who led the study. "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."

By attaching to P-glycoproteins, the HIV carrier acts like a Trojan horse and allows therapeutic drugs into the cancer cells undetected.

Researchers also coated the virus with luciferase, the protein that makes fireflies glow. After injecting it into a vein in the tails of lab mice, they watched with an optical camera as the carrier migrated through the bloodstream right to the melanoma cells, which had by then migrated to the lungs. For the next step, UCLA will enhance the carrier's precision so that it will be able to identify the exact location of the cancer cells to kill them.

The UCLA study may improve HIV's reputation. While it still kills 3.1 million people worldwide every year, scientists may soon be able to use it to cure not only cancer, but other acquired and genetic diseases involving mutation of cells, according to UCLA biologist Elizabeth Withers-Ward.

"It's taking a virus with a very negative potential and turning parts of it into a very positive thing," she said. "There are endless possibilities of how this might be used."

But using HIV to kill cancer makes some people nervous. Many worry that it might backfire and leave someone with both cancer and AIDS. However, Chen says that kind of mishap is not likely.

"People might wonder if it's scary to use HIV as a therapy," he said. "But in actuality we have completely removed 80 percent of the virus. So really it's just a carrier."

In the past, failed gene therapy has ruined the careers of respected scientists and cost at least one human life. In 1999, Jesse Gelsinger, age 18, died in less than a week after being treated with gene therapy for his rare liver disease at University of Pennsylvania. His death led to an investigation by the FDA and the closure of the gene therapy program at the university.

So while a potential cure for cancer may be tempting to rush, more tests will be needed before this technology could be tried in humans.

"One of the problems with gene therapy has been whenever people get a new approach they immediately go into patients," Chen said. "Our approach has been tests in cell culture, then in mice. We're not planning any clinical trials until this is fully refined."

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Posted 03-21-2005 5:17 PM by Doug Casey