Stem cell-based therapy for malignant glioma

Stem cells have been extensively investigated as tumour-tropic vectors for gene delivery to solid tumours. In this review, we discuss the potential for using stem cells as cellular vector systems in gene therapy for malignant gliomas, with a focus on neural stem cells, and multipotent mesenchymal stromal cells. Tumour cell-derived substances and factors associated with tumour-induced inflammation and tumour neovascularisation can specifically attract stem cells to invasive gliomas. Injected stem cells engineered to produce anti-tumour substances have shown strong therapeutic effects in experimental glioma models. However, the potential caveats include the immunosuppressive functions of multipotent mesenchymal stromal cells, the contribution of stem cells to the pro-tumourigenic stroma, and the malignant transformation of implanted stem cells. In addition, it is not yet known which stem cell types and therapeutic genes will be most effective for the treatment of glioma patients. Here, we highlight the possibilities and problems for translating promising experimental findings in glioma models into the clinic.