Glioblastoma, the aggressive and hard to treat brain cancer that Sen. John McCain (R-Ariz.) announced he was diagnosed with in July, is the target of new research using a surprising treatment: Zika virus.

About 12,000 people are diagnosed with glioblastomas each year in the United States. Current treatment focuses on surgery, radiation and chemotherapy. 

But now, researchers think Zika virus ― which threatens the health of a fetus and can cause severe birth defects ― could be an appropriate treatment for glioblastoma because they see similar pathways in the way brain tumor cells and healthy stem cells in fetuses grow and divide.

Because Zika targets fetus stem cells, researchers hypothesized that it might also be able to target glioblastoma cells, according to findings published on Sept. 5 in the Journal of Experimental Medicine. 

The abundance of neuroprogenitor stem cells in a human fetus partly explains why Zika virus can be so damaging to a fetal brain, while adults, who don’t have many neuroprogenitor cells, typically only experience mild symptoms ― like fever and joint pain ― when they’re exposed to Zika.

“We have guarded optimism about this treatment,” said Dr. Michael Diamond, study author and professor of medicine, molecular microbiology, pathology and immunology at Washington University School of Medicine in St. Louis.

To test their theory, researchers at the Washington University School of Medicine and the University of California San Diego School of Medicine injected either Zika virus or a saltwater placebo into the brain tumors of mice. After two weeks, the mice that were given the Zika injection had smaller tumors than those given the placebo.  

The researchers also experimented with injecting a mutated form of Zika virus into mice, and found that the weaker mutant version still replicated and killed tumor stem cells. The weaker mutant virus should also be easier for the body’s healthy cells to defeat.

Despite the promising research findings, testing in humans, much less availability as a cancer treatment, remains a long way off. If all goes well, the researchers hope to begin human trials in 18 months.

“We envision tests in humans, and eventually adding this to existing conventional therapy (surgery, radiation, and chemotherapy) to kill the otherwise resistant stem cell component of the tumor,” Diamond said.

“But we need to further test safety and we need to first prove this works in human glioblastomas when transplanted into mice.”

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