Zika, notorious for ravaging the brains of babies, could be useful in treating a particularly deadly brain cancer.

The virus kills glioblastoma stem cells, say researchers at UC San Diego and Washington University in St. Louis. They tested in human cell cultures and a mouse model of the disease

Moreover, Zika largely spared mature brain cells, the researchers say in a study published Tuesday in the Journal of Experimental Medicine.

People with glioblastoma rarely survive more than two years, although survival rates vary according to age and how aggressive the tumor is.

Study authors suggest a tamed version of the virus could be used along with other treatment to improve survival rates.

U.S. Senator John McCain was recently diagnosed with glioblastoma. The disease killed U.S. Senator Ted Kennedy, singer-actress Ethel Merman and retired baseball player Gary Carter.

Glioblastomas are treated with surgery, followed by radiation and chemotherapy. However, it is impossible to remove all the cancer without also removing healthy tissue and risking brain damage. So the cancer nearly always comes back.

Cancer stem cells cause the recurring tumors. These cells bear strong genetic resemblances to normal stem cells, and can proliferate greatly. Just one cell can regrow an entire tumor.

Glioblastoma stem cells also resist chemotherapy and radiation. But because they are stem cells, they are vulnerable to Zika. The virus causes an abnormally small head, or microcephaly, by destroying immature neural cells.

The study authors say a modified Zika virus could be applied after surgery, penetrating to the remaining cancer cells and killing them. One author, Jeremy Rich, M.D., is a renowned brain cancer specialist who recently joined UC San Diego from Cleveland Clinic. The first author, Zhe Zhu, also researches at UCSD.

Brain cancer specialists not involved with the study said by email it is scientifically sound, but there is a long way to go before it could be used in patients.

The science in this study is good considering the limitations of test tube and mice models, said Keith Black, M.D., chair of neurosurgery at Cedars-Sinai Medical Center in Los Angeles. What we don't know is how these results will translate to humans, given how different the complex human tumors are compared to simplistic mice models.

Before a Zika-based therapy can be tested in people, toxicity studies need to be completed in animals, along with regulatory approvals from the U.S. Food and Drug Administration and the institutes where the trial is to be conducted, Black said.

The approach has precedent in viral therapy by San Diegos Tocagen to treat glioblastoma, said Faith Barnett, M.D., a neurosurgeon with Scripps Green Hospital in La Jolla. Tocagens therapy is already being tested on glioblastoma patients. It uses poliovirus and retroviruses, a class of virus that includes HIV.

Whether Zika virus is a better vector needs to be determined, Barnett said. Clearly, we need creative approaches to improve current cancer therapies.

Unlike Zika, Tocagens viruses dont directly attack the brain cancer cells. Instead, they deliver a gene to the cancer that primes it for destruction when exposed to a drug precursor or prodrug.

The prodrug is converted into a toxic drug inside the cancer cells through an enzyme the gene codes for. Normal cells dont get the gene, and so are unaffected by the prodrug.

Go online to http://tocagen.com/patients for more information on Tocagens clinical trials.

For further reading

McCain completes round of radiation, chemo for brain cancer

UC San Diego hires renowned brain cancer expert Jeremy Rich

Blocking a tumor suppressor gene actually slows down one kind of glioblastoma

Survival time increases for those with deadly brain cancer: Study

Cancer genes hide outside chromosomes

Mom delays cancer care to protect baby she says saved her

Gary Carter to treat brain tumor with chemotherapy

Glioblastoma Anti-Angiogenesis Resistance Mechanism Found by Salk Researchers

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Zika kills brain cancer cells, may find use as therapy - The San Diego Union-Tribune