We further demonstrated that sorted cells from tumors transduced either by lentiviral LCMV-GP or VSV-G pseudotyped lentiviral vectors had the ability to form spheroids upon culturing in neural basal medium supplemented with EGF and bFGF. Spheroids from both sorted cell populations expressed the neural stem cell markers nestin and SOX2 and showed the ability to express the differentiation markers GFAP and b-tubulinIII under serum conditions. These properties have been described for neural progenitor cells [40] as well as for cancer stem-like cells in human glioblastoma [26] . Thus, the cell populations transduced by LCMV or VSV pseudotyped lentiviral vectors showed features of cancer stem-like cells which might be an important target for therapy.