Hobbled Virus Kills Cancer Cells

Scientists have altered a common respiratory virus to destroy cancer cells while leaving healthy ones unscathed, says a Report in tomorrow's issue of Science. The next step--a clinical trial in human cancer patients--is already under way.

The cancer killer is a genetically altered lung pathogen and a member of the adenovirus family. Biochemist Frank McCormick and his colleagues at ONYX Pharmaceuticals in Richmond, California, found that the altered virus is unable to reproduce in normal cells, but it thrives in cancer cells lacking the p53 gene that suppresses tumor growth. The p53 gene, which leaves cells vulnerable to the virus when it is defective, is one whose loss or inactivation is linked to the development of 50% of all human cancers. As a result, the virus might be widely applicable in cancer therapy, especially because loss of p53 also helps make cancers resistant to conventional chemotherapeutic drugs. The altered virus killed human tumors implanted in mice without harming normal cells.

``What I like is how clever it is,'' says Richard Klausner, director of the National Cancer Institute. ``It's been a long-held fantasy to find an [anti-cancer] virus.'' Still, he warns that ``not every [new cancer treatment] that's clever and targeted [to tumor cells] will wind up being useful.''

The ONYX team is testing the safety of the virus in people with head or neck cancers who have not responded to conventional therapies. The trials should be finished in 1997. So far, the virus, which is injected directly into the patients' tumors, appears safe. But it's too early to tell whether the virus has the same ability to kill tumors in humans that it has in mice.