Figure 6.

CD133-/CD271+ cells exhibit tumor-initiating cell capacity in vivo and MB subpopulations can reestablish phenotypic heterogeneity following reculture as tumor spheres. (A) Scatterplot depicting time between injections of unsorted or sorted MB tumor sphere subpopulations and signs of tumor formation including appearance of a domed head caused by hydrocephalus. *P < .05. (B) Semiquantitative scoring of Daoy MB tumor samples, based on a scale of 0 to 3, where 0 = no malignant cells, 1 = rare clusters of malignant cells confined to the subarachnoid space, 2 = malignant cells in subarachnoid compartment and invasion along perivascular spaces, 3 = features in 2 plus tumor nodules growing in other areas of the brain or cerebellum. (C–H) Infiltration of malignant MB cells from unsorted tumor spheres (C, F), CD133-/CD271+ cells (D, G), and CD133-/CD271- cells (E, H). Arrows in the upper panels depict highly infiltrative MB cells and formation of smaller clusters of MB cells throughout the brain. The arrows in the lower panel denote intense perivascular infiltration. Scale bars, 500 µm (upper panels), 100 µm(lower panels). (I–L) Parental Daoy MB tumor spheres (I) were sorted on the basis of CD133/CD271 expression. Three subpopulations were sorted and recultured as tumor spheres for 6 days (J–L). Cultures derived from sorted subpopulations were then evaluated for CD133/CD271 expression. Error bars, SEM.