Over the past few years, our awareness of the Zika virus has grown, but only because of headlines that describe how devastating it can be. Fortunately, scientists have recently found a useful purpose for the pandemic bug: brain cancer treatment.
Researchers out of the Washington University School of Medicine (St Louis) and University of California San Diego found that this particular virus is able to target and destroy the stem cells that drive growth of glioblastoma, a common—and deadly—type of brain tumor.
Every year, about 12,000 people in the United States alone receive a diagnosis for glioblastoma.
According to Michael Diamond, of Washington University School of Medicine, “Our study is a first step towards the development of safe and effective strains of Zika virus that could become important tools in neuro-oncology and the treatment of glioblastoma.”
The study co-lead goes on to say, “However, public health concerns will need to be addressed through pre-clinical testing and evaluations of the strains’ ability to disseminate or revert to more virulent forms.”
This research, of course, is still in its early stages, but has wonderful long term implications. Treatments for this type of brain tumor have not been very consistent and most people who are diagnosed with glioblastoma will die within two years.
That is because the stem cells that power the tumors are not easy to kill and they are good at hiding from the body’s natural immune system; and the treatments we do have tend to be ineffective.
Study co-lead Milan Chheda comments, “It is so frustrating to treat a patient as aggressively as we know how, only to see his or her tumor recur a few months later.”
Also from Washington University School of Medicine, Chheda goes on to say, “We wondered whether nature could provide a weapon to target the cells most likely responsible for this return.”
Jeremy Rich, from the University of California San Diego and the Cleveland Clinic Lerner Research Institute, also co-authored the study. He comments, “This effort represents the creative synthesis of three research groups with complementary expertise to attack a deadly cancer by harnessing the cause of another disease. Adults with Zika may suffer less damage from their infection, suggesting that this approach could be used with acceptable toxicity.”
The results of this study were published in The Journal of Experimental Medicine.
The standard treatment is aggressive – surgery, followed by chemotherapy and radiation – yet most tumors recur within six months. A small population of cells, known as glioblastoma stem cells, often survives the onslaught and continues to divide, producing new tumor cells to replace the ones killed by the cancer drugs.
In their neurological origins and near-limitless ability to create new cells, glioblastoma stem cells reminded postdoctoral researcher Zhe Zhu, PhD, of neuroprogenitor cells, which generate cells for the growing brain. Zika virus specifically targets and kills neuroprogenitor cells.
In collaboration with co-senior authors Diamond and Milan G. Chheda, MD, of Washington University School of Medicine, and Jeremy N. Rich, MD, of UC San Diego, Zhu tested whether the virus could kill stem cells in glioblastomas removed from patients at diagnosis. They infected tumors with one of two strains of Zika virus. Both strains spread through the tumors, infecting and killing the cancer stem cells while largely avoiding other tumor cells.
The findings suggest that Zika infection and chemotherapy-radiation treatment have complementary effects. The standard treatment kills the bulk of the tumor cells but often leaves the stem cells intact to regenerate the tumor. Zika virus attacks the stem cells but bypasses the greater part of the tumor.
“We see Zika one day being used in combination with current therapies to eradicate the whole tumor,” said Chheda, an assistant professor of medicine and of neurology.
To find out whether the virus could help treat cancer in a living animal, the researchers injected either Zika virus or saltwater (a placebo) directly into the brain tumors of 18 and 15 mice, respectively. Tumors were significantly smaller in the Zika-treated mice two weeks after injection, and those mice survived significantly longer than the ones given saltwater.
If Zika were used in people, it would have to be injected into the brain, most likely during surgery to remove the primary tumor. If introduced through another part of the body, the person’s immune system would sweep it away before it could reach the brain.