Radiosensitization of cancer stem cells in glioblastoma by the simultaneous inhibition of parallel DNA damage response pathways

Glioblastoma is the most common primary brain cancer in adults, the standard treatment for which is surgical resection followed by radiotherapy and chemotherapy with temozolomide (an alkylating agent) (1). Glioblastoma cells extensively exhibit genetic and phenotypic intra-tumor heterogeneity, and the subclones of tumor cells have higher regenerative/stem cell activity than the other parts of glioblastoma tumor (2). Previous workers have shown that glioblastoma stem-like cells exhibit higher resistance to chemo- and radiotherapy than the differentiated bulk tumor cells (3-5). Therefore, analysis of the stem-like cells is essential to overcome the therapeutic resistance of glioblastoma.