Fig. 2. Sorted populations of EGFRvIII^High or EGFRvIII^Low GBM cells give rise to identical mixed tumors in vivo.

(A) Tumor cells from GBM39 xenografts sorted for EGFRvIII expression and injected into mice are equally tumorigenic (n = 4 mice per group). The white line indicates 1 inch. (B) FACS analysis of sorted cells reveals that enriched populations of EGFRvIII^High and EGFRvIII^Low tumor cells re-establish mixed populations within 2 weeks. (C) Analysis of xenograft models deriving from sorted EGFRvIII^High and EGFRvIII^Low tumor cell populations from (A) that give rise to tumors with an EGFRvIII^High/EGFRvIII^Low tumor cell composition similar to that of initial, untreated GBM39 tumors. Values are mean ± SEM. (D and E) GBM39 tumor cells sorted for EGFRvIII expression and plated at a single cell per well and stained for EGFRvIII (red) and 4′,6-diamidino-2-phenylindole (DAPI) (blue) give rise to heterogeneous colonies. (F) Identical EGFRvIII^High/EGFRvIII^Low composition from tumor cells sorted in (D) and plated at 2 to 5 cells per well. Values are mean ± SEM from n = 5 independent cultures.