Histological analysis of BT1 and BT1-derived tumors in nude mice. BT1 neurospheres (1 × 10e5) were stereotactically injected into the left hemisphere of nude mice (Charles River Italia, Calco, Italy; n = 3) or subcutaneously (n = 3). Nude mice were also injected with 1 × 10e5 BT1 adherent cells into the brain (n = 3) or subcutaneously (n = 3). Cells from BT2 were injected with similar procedures into nude mice. Control mice (n = 3) were injected with 1 × 10e5 neural stem/progenitor cells obtained from C57BL6J mice with previously described methods . Fig 1A-B shows the GFAP staining in brown of coronal sections of the tumor derived from neurospheres (1A) or from adherent cells (1B). The right part on the figures correspond to the left hemisphere, were cells were injected. Fig. 1C-E show H-E staining of the primary tumor with features of a glioblastoma multiforme (1C) and of a tumor in mouse brain derived from neurospheres, showing an area with a prevailing aspect of oligodendroglioma (1D) or adherent cells, exhibiting anaplastic changes (1E). Fig. 1F-H show nestin staining of the primary tumor (1F) and of a tumor in mouse brain derived from neurospheres (1G) or adherent cells (1H).