Mutated Cold Virus Kills Cancer Tumors, Study Says
A mutated version of an ordinary cold virus turns into a cancer killer when injected into tumors, according to research with laboratory mice. The therapy is now being used experimentally in human patients.
In a study published Friday in the journal Science, researchers report that a genetically engineered version of adenovirus, one of a number of viruses that cause the common cold, is able to attack and destroy human cancer cells that lack a gene called P53. About half of all human cancers involve a defective or missing P53 gene.
“The mutated virus takes over and turns the [cancer] cell into a factory to make more virus,” said Frank McCormick, a researcher at Onyx Pharmaceuticals in Richmond, Calif. “After a day or two, the cell is killed and it releases a whole bunch of new virus, which then infect neighboring cancer cells.”
About 60% of human tumors grown in laboratory mice melted away after being injected with the mutated adenovirus, said McCormick, lead author of the study.
But the altered virus’ true cancer-fighting ability will not be known until human trials are done, said Dr. Bert Vogelstein, a Johns Hopkins University researcher who first discovered that an altered or missing P53 gene can lead to cancer.
A normal P53 gene suppresses cancer by detecting flawed DNA when a cell is dividing. If the DNA is abnormal, P53 either stops the division or kills the cell.
A normal adenovirus causes mild upper respiratory infections by invading a cell and making a protein that inactivates P53. That enables the virus to take over and eventually kill the cell, releasing into the bloodstream the new viral particles. The altered adenovirus, developed at UCLA, is unable to make the protein that blocks the action of P53.
The alteration’s effect, McCormick said, is that the virus is unable to replicate efficiently in normal cells, which have P53, but thrives in cancer cells that lack the gene. As a result, he said, an altered virus uses cancer cells to make more virus and then kills the cells, freeing new viral particles to attack other cancer cells.
Early human trials of the altered adenovirus are under way now in San Antonio and Glasgow, Scotland.
