Fig. 4.

Embryonic stem cell (ESC)-derived astrocytes conditionally expressing TRAIL induce apoptosis in human malignant glioma xenografts in vivo. (A and B) Apoptosis occurred in vivo after ESC-mediated gene delivery: fluorescent microphotographs of A172 malignant glioma xenografts in experimental (A) and control (B) animals after TUNEL labeling. Numerous TUNEL-positive cells are seen in the experimental animal (arrows) and not in the controls. (C) Superimposed microphotograph of TUNEL-positive cells (green, arrows) and ESC-derived astrocytes (red). The lack of overlap shows that apoptosis occurred only in tumor cells. Scale bar, 50 μm.