Engineered Viruses Could Kill Cancer

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The last thing you need is a dangerous viral infection — unless you have cancer.

Cancer cells divide like mad, crowding out their neighbors and causing tumors, the complications from which eventually kill. But the vigor has a price: cancer cells aren't as good at fighting off viral infections, and theoretically a virus could kill cancer cells without harming the patient.

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A great article in The New York Times by Rachel Nuwer describes medical efforts to commandeer viruses in the fight against cancer.

Those efforts date to 1951 when a 4-year-old child with leukemia caught chicken pox. The cancer went into remission. Unfortunately the moment the chicken pox went away, the leukemia came back and the child died.

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There were some attempts to use this phenomenon to benefit patients. Those early efforts ended in failure and by the 1960s the research focus shifted to other treatments.

But a lot has happened since then. Medical science has made strides in understanding the genetics and mechanisms of viruses and cancer both, and it may be that soon, tailored viruses could cure some cancers.

Dr. Robert Martuza, chief neurosurgeon at the Massachusetts General Hospital and professor of neuroscience at Harvard Medical School, started looking at herpes simplex virus, or HSV-1, as a cancer fighting tool back in 1991. Dr. Martuza took out a few genes from the virus and injected it into mice with brain cancer. Although the cancer went into remission most of the mice died of encephalitis.

Meanwhile, in 1990, Bernard Roizman, a virologist at the University of Chicago, found a gene in the herpes virus that when removed, makes it unable to get past the defenses of healthy cells — but not cancer. That slowed the growth of cancer cells, though it didn't kill them.

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Six years later, Dr. Ian Mohr, a virologist at New York University, found a way of altering the virus that Roizman engineered. The virus evades the immune system and is better at killing cancer cells.

Herpes isn't the only virus being recruited for anti-cancer duty. Vaccinia was the virus used to protect against smallpox and it's now being tested against liver cancer. Thus far the results are promising, extending survival times in one group of patients. Others are bring used against melanoma, bladder cancer and head and neck cancers.

That doesn't mean it's time to break out the champagne. As the liver cancer trial shows, improving survival isn't the same as a cure, and every cancer is different. A magic bullet that works on every type is unlikely. Gary Hayward, a virologist at the Johns Hopkins Herpesvirus Research Program, told the New York Times that progress is likely to be incremental — much as it has been for decades.

At the same time, another tool against cancer is always welcome, and it's another step in making cancer a survivable disease.

Credit: Wikimedia Commons / Centers for Disease Control