Genetically-Engineered Cold Virus Kills Cancer Cells

A genetically altered version of a common cold virus, or adenovirus, was recently constructed that may be able to destroy cancer cells in humans. The design of the cancer-fighting virus involves a protein produced by the p53 gene in cells. The p53 protein prevents tumor growth by not allowing cells with damaged or foreign DNA to reproduce. Indeed, in many cancer cells, p53 has been damaged and does not produce the tumor-suppressing protein. In recent experiments, scientists observed that p53 also orders the death of cells that have been infected with the adenovirus. However, the adenovirus is able to make a protein that binds to p53, thereby preventing its normal functioning. The virus then replicates within the cell, kills the cell, and moves on to infect other cells.

With this knowledge, researchers realized that if they could engineer an adenovirus that was unable to make the anti-p53 protein, a cell with p53 protein would be able to prevent the replication of the virus. But in a cell without p53, like a cancer cell, the adenovirus would grow unchecked and kill the cell. In experiments on human tumors that were grown in mice that lacked immune systems, the altered adenovirus was injected and caused some of the tumors to disappear completely.

Researchers hope that the genetically-engineered adenovirus will be able to fight head and neck tumors on human in tests currently underway. One of the problems may be the immune system, which destroys cells with the adenovirus, and may destroy cancer cells with the altered adenovirus before it has a chance to spread to other cancer cells. Also, it is unclear whether the virus will infect tumors that are deep or otherwise inaccessible, as only direct injections into tumors have been tested.

"Will a Twist of Viral Fate Lead to a New Cancer Treatment" Science, October 18, 1996

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