Back in the early '90s, when Antonio Chiocca, MD, PhD, first read a paper on using viruses to fight cancer, he didn't think it was too practical. In fact, that was my first reaction, too. The first tools developed through this new approach currently are being tested in clinical trials at major cancer research centers.
Cancer cells are different from normal cells.
Today, scientists are taking advantage of these differences to use viruses to attack cancer, while leaving normal cells alone. For example, normal cells have a p53 gene, which recognizes when it's time for that cell to die. We've taken an adenovirus, which is responsible for the common cold. We've weakened it genetically, so it won't grow in normal cells. This form of the virus, called ONYX-015, only grows in cancer cells that don't have p53 functioning.