Figure 5.

Recurrent GBM tumors exhibit increased expression of endothelial cell markers relative to primary tumors in vivo. (a) Schematic representation of experimental design. PDX GBM43 cells were implanted intracranially in the right cerebral hemisphere of athymic nude mice. Five days later, treatment was initiated, with three groups of mice receiving TMZ (2.5 mg) or equimolar DMSO. Mice were given the drug each day for five consecutive days and then were sacrificed three days following therapy. A second TMZ group was allowed to progress until tumor symptoms developed. Tumor cells were then analyzed by FACS. (b) Tumor cells were identified via use of a human-leukocyte antigen conjugated to Pacific Blue (PB). (c) Quantification of FACS analysis for percentage of cells positive for both CD133, a glioma stem cell marker, and CD105 or CD144, markers of intermediate endothelial cells. Note that these populations only reflect human cells. (d) Quantification of FACS analysis for percentage of cells positive for both CD133, a glioma stem cell marker, and CD34 or CD31, markers of mature endothelial cells. (e) Flow cytometry plots showing the expression of CD105 and CD144 in mice with implanted tumors treated with DMSO, mice treated with TMZ and sacrificed after 3 days, and mice treated with TMZ and sacrificed at the endpoint. (f, g). Quantification of flow cytometry showing a significant increase in the expression of immature EC markers CD105 and CD144 in mice treated with TMZ that developed recurrent brain tumors. The means of all mice were compared by one-way ANOVA with multiple comparisons. ^∗ p < .05, ^∗∗ p < .01, and ^∗∗∗ p < .001. N = 5 mice/group.