Glioblastoma Multiforme stem cells are highly sensitive to some human non-pathogenic enteroviruses

Glioblastoma multiforme (GBM) is the most severe and still incurable form of brain tumors. Following surgical removal of the tumor, subsequent chemotherapy and radiation therapy, a relapse of the disease inevitably occurs, which is resistant to further treatment. The cause of relapse is tumor stem cells that can penetrate deep from the resectable tumor and display a high resistance to radio- and chemotherapy. Oncolytic viruses can be a promising alternative for the treatment of GBM. We used a set of four nonpathogenic human enteroviruses (Sabin live vaccine strain of Poliovirus Type 1, Echovirus 12, Coxsackievirus A7, Coxsackievirus B5) to test the sensitivity of GBM cells obtained from five patients. The presence of stem cells in the cell population was evaluated by the formation of neurospheres in a specialized serumfree medium. Neurospheres are enriched with the GBM-initiating stem cells, while the GBM cell cultures maintained in the presence of fetal bovine serum form monolayers of attached differentiated cells that contain little or no stem cells. We compared the sensitivity to viruses of differentiated GBM cells and the corresponding neurosphere cultures. The monolayer cultures of GBM have demonstrated generally high but variable sensitivity to the enteroviruses. Each of the cell cultures tested was highly sensitive to at least four enterovirus strains. The same strains that demonstrated good replication in monolayer cultures were also active in spheroid cultures originated from the same patient suggesting that the viruses can efficiently kill GBM stem cells. Based on the results of the study, it can be concluded that the potential use of oncolytic enteroviruses for glioblastoma therapy is promisin