Fig. 1.

Engineering of embryonic stem cell (ESC)-derived astrocytes and expression of transgenic TRAIL. (A) Schematic representation of integrated expression cassettes. The reverse tetracycline transactivator (rtTA) is integrated into the constitutive ROSA 26 locus on chromosome 6. Cre-mediated recombination of targeting vectors into the homing site on the X chromosome restores resistance to the antibiotic G418 (neomycin [neo]), thereby facilitating efficient isolation of transgenic cells. HPRT, hypoxanthine-guanine phosphoribosyltransferase; TRE, tetracycline-responsive element; ATG, methionine initiation codon; TRAIL, tumor necrosis factor–related apoptosis-inducing ligand. (B) Reverse transcription PCR gel of malignant astrocytoma xenografts after injection of ESC-derived astrocytes conditionally expressing TRAIL. TRAIL was detected in the experimental group after doxycycline induction (+Dox). This was not observed in the control groups (− Dox). Actin was used as internal control.