Virus-Armed Immune Cells Versus Cancer

Scientists say they're closer to perfecting a double-barreled "smart bomb" approach that one day might kill off stubborn cancers without damaging surrounding tissue.

The technique -- which uses targeted viruses hidden in immune cells to destroy tumors -- has only succeeded in mice so far, and it's not known if it will work in humans.

Still, the treatment has the potential to be an "exciting advance," said Clodagh O'Shea, a cancer research specialist at the University of California, San Francisco who's familiar with the federally funded study.

Scientists know that some viruses hone in on cancer cells, and they know that the immune system often swings into action whenever it detects a tumor. Blending these two potential weapons, researchers at Stanford University have taken immune cells, "supercharged" them with a cancer-killing virus, and sent them on a mission to destroy tumors.

Reporting in the March 24 issue of Science , the study's authors say the approach appeared to kill off tumors in mice infected with human ovarian cancer cells.

Research has already shown that it's safe to treat humans separately with either the immune cells or the virus, said study co-author Christopher H. Contag, an associate professor of microbiology and immunology. The question now is whether they'll work when combined together.

"The chances are pretty good that they'll be safe and well-tolerated by patients," Contag said, "but we don't know what will happen in humans."

There are potential problems: The virus, known as vaccinia, could make people sick, although Contag said patients could be treated for that illness. Vaccinia is currently a component of the smallpox vaccine because it is related to smallpox but is much milder.

Also, it will be important to make sure that enough virus gets to a tumor to kill off the proper number of cancer cells, Contag said.

O'Shea, the cancer research specialist, said the strategy in the study is "novel and creative." According to him, being able to "hide" the virus in an immune cell is promising, because it could help the virus survive the trip through a patient's blood system.

However, he added that both the immune cells and the vaccinia virus are "highly experimental" treatments for cancer.

More information

Learn more about vaccinia, the virus used in this experimental cancer treatment, from the U.S. Centers for Disease Control and Prevention .