The Zika virus struck fear into the hearts of parents and would-be parents, last year. Moms who were infected during pregnancy often gave birth to babies with serious birth defects, including small brains. A number of the problems linked to the disease came from how the virus impacted the developing nervous system. But someday, Zika might also gain renown as a medical therapy — to treat deadly brain cancers.
That‘s the finding of a new study. In it, researchers infected human cells and mice with the virus. And in both, the virus killed certain stem cells — ones that would have gone on to become an aggressive type of brain tumor. This deadly cancer is known as a glioblastoma (GLEE-oh-blas-TOE-mah). Even more exciting, the germ left healthy brain cells unharmed.
Jeremy Rich is a scientist who focuses on regenerative medicine at the University of California, San Diego. His team shared its new findings online September 5 in the Journal of Experimental Medicine.
Previous studies had shown that Zika kills the cells in the developing brain that can mature into nerve cells — also known as neurons. Neuroscientists thought maybe this explained the brain problems seen in many babies whose mothers who had been infected with Zika during pregnancy.
There are similarities between those cells that will become neurons and the cells that can turn into glioblastomas. Knowing this, Rich’s team suspected Zika might target the cells that can morph into the very deadly brain-cancer cells.
In the United States, some 12,000 people are expected to be diagnosed with glioblastoma this year. One of them was U.S. Senator John McCain. Doctors diagnosed his cancer this past July. The bad news: Even with treatment, most patients live only about a year after a gliobastoma diagnosis.
Rich and his colleagues have now tested their Zika treatment in the lab. They infected human stem cells that will go on to become glioblastomas. This treatment halted the cells’ growth, the scientists report. The virus also infected some full-blown glioblastoma cells, but not as many. The good news: The virus did not infect normal brain tissues.
Mice, too, can develop glioblastomas. And Rich’s team treated some mice with the cancer and then watched what happened to their disease. Compared to uninfected mice, tumors in the Zika-treated animals either shrank or grew more slowly. Zika-infected mice lived longer, too. In one trial, almost half of the mice survived more than six weeks with their brain cancer after being treated with Zika. In comparison, the cancers in mice who had not been uninfected with the virus died within two weeks of the start of the trial.
Using a virus to knock out cancer isn’t a new idea. Some tumors, including glioblastomas, are being treated with a modified poliovirus. Such trials are experimental. The U.S. government has also approved a modified herpes virus to treat melanoma, a deadly skin.
Andrew Zloza is a cancer specialist at the Rutgers Cancer Institute of New Jersey in New Brunswick. Cancer-fighting viruses seem to work in two ways, he says. First, they infect and kill tumor cells. Then, as the dying cells split open, previously hidden tumor fragments become visible to the immune system. The body recognizes those fragments and launches a fight against them.
“Right now we don’t know what kind of viruses are best” for fighting cancer, Zloza says. But Zika, he notes, is now another candidate.
Further tests are needed to find out if the virus is safe and effective in people. Since Zika’s effects are more harmful in developing brains, a Zika-based cancer therapy might be safe only in adults. And genes in the virus would need to be modified to make the germ safer and less likely to spread.
Rich and his colleagues are now running tests in mice to see if combining Zika with traditional cancer treatments, such as chemotherapy drugs, would be more effective than either treatment alone. Because Zika targets the cells that generate tumor cells, it might also prevent tumors from coming back.
aggressive (n. aggressiveness) Quick to fight or argue, or forceful in making efforts to succeed or win.
cancer Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
chemotherapy A chemical treatment that’s most often used to kill cancer cells in the body. Chemotherapy can have many unpleasant side effects as it kills not only cancer cells but many healthy cells as well.
colleague Someone who works with another; a co-worker or team member.
gene (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.
germ Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
glioblastoma A type of relatively common and aggressive brain tumor. It is a form of astrocytoma, a cancer named for the star-shaped cells that it affects. Until recently, few people with the disease survived even five years after diagnosis. No one knows what causes the disease and there is no cure. Treating it is challenging.
immune system The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.
infect To spread a disease from one organism to another. This usually involves introducing some sort of disease-causing germ to an individual.
mature (verb) To develop toward — or into — a more complex and full-grown form of some individual, be it a plant, animal or microbe. (adj.) Connoting an adult individual or full-grown and fully developed (non-juvenile) form of something.
melanoma A type of cancer that starts in pigment-making cells called melanocytes, usually in the skin.
nerve A long, delicate fiber that transmits signals across the body of an animal. An animal’s backbone contains many nerves, some of which control the movement of its legs or fins, and some of which convey sensations such as hot, cold or pain.
nervous system The network of nerve cells and fibers that transmits signals between parts of the body.
neuron An impulse-conducting cell. Such cells are found in the brain, spinal column and nervous system.
neuroscientist Someone who studies the structure or function of the brain and other parts of the nervous system.
stem cell A “blank slate” cell that can give rise to other types of cells in the body. Stem cells play an important role in tissue regeneration and repair.
therapy (adj. therapeutic) Treatment intended to relieve or heal a disorder.
tissue Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
tumor A mass of cells characterized by atypical and often uncontrolled growth. Benign tumors will not spread; they just grow and cause problems if they press against or tighten around healthy tissue. Malignant tumors will ultimately shed cells that can seed the body with new tumors. Malignant tumors are also known as cancers.
virus Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.
Zika A viral disease that can be transmitted to humans via mosquitoes. About 20 percent of infected people get sick. Symptoms include a slight fever, rash and pinkeye and usually fade quickly. A growing body of evidence suggests that the virus could also cause a devastating birth defect — microcephaly. Evidence suggests it may also cause neurological conditions such as Guillain-Barré syndrome.
Journal: Z. Zhu et al. Zika virus has oncolytic activity against glioblastoma stem cells. Journal of Experimental Medicine. Published online September 5, 2017. doi: 10.1084/jem.20171093.
Blog: National Institutes of Health. Glioblastoma—Unraveling the Threads: A Q&A with Drs. Mark Gilbert and Terri Armstrong of the NIH Neuro-Oncology Branch. August 3, 2017.