An oncolytic virus infected and killed both brain cancer stem cells and differentiated compartments of the common and deadly malignant brain tumor, glioblastoma multiforme (GBM), when combined with the immunosuppressant drug rapamycin.
Because oncolytic virotherapy has the potential to target multiple compartments within GBM, this form of treatment may be able to work around some of the barriers facing conventional therapies, explained Peter A. Forsyth, MD, and fellow investigators in Neuro-Oncology (2013;15:904-920). Forsyth, of the H. Lee Moffitt Cancer Center & Research Institute in Tampa, Florida, worked with a team to test the oncolytic potential of myxoma virus alone and in combination with rapamycin using human brain tumor–initiating cells (BTICs).
Laboratory cultures and animal models revealed that brain cancer stem cells were susceptible to myxoma virus. This was true even in cell lines resistant to temozolomide, an agent that can improve survival among persons with GBM. In mice, the virus replicated within the BTICs and significantly prolonged survival.
The addition of rapamycin to myxoma virus improved antitumor activity, including in mice with advanced BTIC tumors.
The study results suggest that myxoma virus in combination with rapamycin infects and kills both the BTICs and the differentiated compartments of GBM, and, although not curative, may be an effective treatment for GBM even in patients resistant to temozolomide.