In the late 1800s, doctors began to notice that some cancer patients went into temporary remission after catching viruses. This was the first discovery of “oncolytic viruses,” which can attack cancer cells and reproduce inside them without harming healthy cells. These viruses take advantage of the fact that cancer cells lack a natural immune response.
Oncolytic virus therapy is now being used to treat head and neck cancer in China, and to treat melanoma in the European Union. Now, scientists in the United States are turning to Ebola, one of the world’s deadliest viruses, to try to fight glioblastoma, the deadliest of brain cancers.
The Problem
Glioblastoma, the type of cancer that struck U.S. Senators Edward M. Kennedy and John McCain, is the most aggressive type of brain tumor: fewer than 7 percent of diagnosed patients will survive longer than five years. “It’s been maybe 10 years since we have had some kind of progress in treating glioblastoma,” says Patricia Garcez, a professor of anatomy at Brazil’s Federal University of Rio de Janeiro.
The Solution
Ebola could be a perfect candidate for attacking brain tumors, says Anthony Van den Pol, a Yale University neurosurgery professor who co-authored an intriguing study published in the Journal of Virology in February. That’s because the virus’s outer layer, composed of molecules called glycoproteins, also contains a mucus-like substance that doesn’t infect and kill nerve cells.
It might sound dangerous to search for cures using Ebola, but scientists circumvented the risk by inserting one Ebola gene into another virus.
It might sound dangerous to search for cures using Ebola, which ravaged West Africa in an epidemic between 2014 and 2016, infecting 28,600 people and killing 11,325. But scientists circumvented the risk by using what’s known as a “chimeric” virus: they took one of Ebola’s genes, a glycoprotein, and inserted it into another virus.
The Yale team implanted a human glioblastoma into the brains of mice and injected those mice with the altered virus. These newly-infected mice lived longer than other mice with brain tumors, leading scientists to hope the same approach might work in humans.
The Challenge
More research is necessary to see if Yale’s discovery leads to an effective treatment. Garcez notes that the Yale team used mice with mutations in their immune cells that enabled the tumors to grow. The therapy has yet to be tested in mice with uncompromised immune cells.
Also, scientists don’t know whether the virus would be able to cross the blood-brain barrier to target cancerous brain cells in humans, continues Garcez.
Another big challenge is cost. To put a vaccine to use in humans, researchers would need to conduct a clinical trial, which could cost anywhere from $500,000 to $1 million. The U.S. National Institutes of Health, which funded the initial Yale research, usually assume that a pharmaceutical company will bear that cost. But so far, no company has stepped up, so Yale’s researchers have applied for more federal funding.
The Big Picture
Other researchers in the field say the idea has potential. “It might be really promising for patients that have had no other options, for whom surgery has failed and chemotherapy and radiation too,” says Garcez. In her own lab in Brazil, Garcez is investigating the Zika virus and its own potential to fight glioblastoma. In the long run, some of the world’s most dreaded viruses might become some of science’s greatest allies.
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