According to the AFP, glioblastoma is a highly lethal brain cancer that frequently recurs in proximity to the original resection cavity. The scientists studied the use of oncolytic virus therapy against glioblastoma with Zika virus (ZIKV), a flavivirus that induces cell death and differentiation of neural precursor cells in the developing fetus. ZIKV preferentially infected and killed glioblastoma stem cells (GSCs) relative to differentiated tumor progeny or normal neuronal cells. The effects against GSCs were not a general property of neurotropic flaviviruses, as West Nile virus indiscriminately killed both tumor and normal neural cells. ZIKV potently depleted patient-derived GSCs grown in culture and in organoids. Moreover, mice with glioblastoma survived substantially longer and at greater rates when the tumor was inoculated with a mouse-adapted strain of ZIKV. The results suggested that ZIKV was an oncolytic virus that can preferentially target GSCs; thus, genetically modified strains that further optimize safety could have therapeutic efficacy for adult glioblastoma patients.
While Zika was known for causing birth defects like microcephaly and brain damage, it turned out that the virus might be also served as a useful purpose -- fighting brain cancer. In recent studies, researches were showed that Zika could actually take on a hard-to-treated type of brain cancers. Standard forms of therapy could be done well against the majority of the tumor cells, but left behind the stem cells that generated the tumors, allowing them to keep creating more tumors once the originals were removed. But Zika actually worked the opposite -- it targeted the stem cells and skipped over the other tumor cells. So, in theory these different treatments would work quite well when used together.
However, what made the Zika so problematic for fetuses? The virus entered into the developing central nervous system and killed neuro progenitor cells, which became various types of brain cells later. The researchers noticed that the glioblastoma stem cells behaved like neuro progenitor cells, which were turned towards Zika as a potential therapeutic. In the experiments, Zika virus was able to kill stem cells and removed glioblastomas of patients. After injected tumors in mouse brains, the tumors were shrunk. Otherwise, the virus would not infect non-cancerous brain cells and mutated versions of Zika by controlling themselves weaker against the body's immune system. They could still kill glioblastoma cells, though not quite as well as the original strains. The researchers have not used it in human studies because the virus worked differently in mice and human. Furthermore, as Zika was not a major risk to the public, the studies believed that it could be a promising treatment for brain cancer in the future.
Reference
Z Zhu, MJ Gorman, LD McKenzie, et al. Zika virus has oncolytic activity against glioblastoma stem cells. J Exp Med., 2017, 214. 10.1084