St. Louis researchers have used a strain of the Zika virus to shrink highly lethal brain tumors in mice.
The study, run by Washington University and the University of California San Diego, used 33 lab mice with glioblastoma, an aggressive form of brain cancer. Mice injected with a strain of the Zika virus lived longer and were measured to have smaller tumors than the control group, which was injected with saltwater.
Zika, which is transmitted by mosquitoes and can cause severe birth defects in humans, has been particularly devastating in several South American countries and the Caribbean. But it has an unlikely connection with glioblastoma, said Dr. Michael Diamond, a viral immunologist at Washington University in St. Louis. The stem cells that Zika targets in the brain of a developing fetus are the same types of stem cells that make glioblastoma so hard to treat.
“Even if you can remove a glioblastoma, it comes back. It’s very hard to eradicate with conventional therapy — these cancer stem cells,” Diamond said. “We opened [the mice] up, and the tumor was markedly reduced or gone in many of the animals.”
About 18,000 people in the United States are diagnosed with glioblastoma every year. This year, that number included Republican U.S. Sen. John McCain of Arizona. Ten percent of patients live for more than five years after their diagnosis.
When a post-doctoral researcher first suggested the idea of using Zika to treat glioblastoma, Diamond admits that he was hesitant. The use of viruses in cancer therapies — called oncolytic therapy — is still an emerging field. The first drug approved by the U.S. Food and Drug Administration to treat melanoma with a strain derived from the herpes virus did not improve overall survival in patients who participated in clinical trials. Several others are being studied.
“Using viruses that target the brain, to do this had some element of risk. However, there were a couple things that were on our side,” Diamond said. “We thought we might be able to not only harness it, but control it as well.”
The researchers have a long way to go. The Zika virus would need to be engineered to ensure it doesn’t spread or change after it eliminates the cancer. Then, mice would have to be induced to grow human glioblastoma tumors for further trials.
“The idea for therapy, if it gets this far, is that we would actually inject it at the time the tumor is removed, in the brain directly… to mop up the stem cells,” Diamond said. “[Those] are the real problem for recurrence, and what actually kills you.”
The study appears Tuesday in The Journal of Experimental Medicine.
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