CD133, CD15/SSEA-1, CD34 or side populations do not resume tumor-initiating properties of long-term cultured cancer stem cells from human malignant glio-neuronal tumors

Tumor initiating cells (TICs) provide a new paradigm for developing original therapeutic strategies. We screened for TICs in 47 human adult brain malignant tumors. Cells forming floating spheres in culture, and endowed with all of the features expected from tumor cells with stem-like properties were obtained from glioblastomas, medulloblastoma but not oligodendrogliomas. A long-term self-renewal capacity was particularly observed for cells of malignant glio-neuronal tumors (MGNTs). Cell sorting, karyotyping and proteomic analysis demonstrated cell stability throughout prolonged passages. Xenografts of fewer than 500 cells in Nude mouse brains induced a progressively growing tumor. CD133, CD15/LeX/Ssea-1, CD34 expressions, or exclusion of Hoechst dye occurred in subsets of cells forming spheres, but was not predictive of their capacity to form secondary spheres or tumors, or to resist high doses of temozolomide. Our results further highlight the specificity of a subset of high-grade gliomas, MGNT. TICs derived from these tumors represent a new tool to screen for innovative therapies.