ET-67 SUICIDE GENE THERAPY FOR GLIOMA USING MULTILINEAGE-DEFFERENTIATING STRESS ENDURING (MUSE) CELLS

INTRODUCTION: We have been investigating cell-based glioma gene therapy using various kinds of stem cells transduced with the herpes simplex virus thymidine kinase gene (HSVtk). In our previous study, we used SSEA3/CD105 double-positive multilineage-differentiating stress-enduring (Muse) cells transduced with HSVtk (Muse-tk cells) as the vehicle for HSVtk/ganciclovir (GCV) gene therapy. We demonstrated a potent in vitro tumoricidal bystander effect for various glioma cells. In the present study, we examined the in vivo bystander effect between U87 human glioma cells and human Muse-tk cells. METHODS: Muse-tk cells were obtained by lentiviral transduction of HSVtk in human Muse cells. U87 cells transduced with the luciferase gene were used for the brain tumor model, in which tumor volume could be measured using a bioluminescence imaging system (IVIS 200). Nude mice were intracranially co-implanted at Muse-tk:U87 cell ratios of 1:4, 1:8, and 1:16 (U87 cell number: 1 105); GCV was intraperitoneally administered (100 mg/kg/day) for 10 days. RESULTS: Luminescence intensity progressively increased in the control mice implanted with U87 alone with or without GCV treatment, and in those implanted with Muse-tk and U87 but not treated with GCV. All control mice died because of the tumor by Day 51 post tumor implantation (no difference among the control groups). In contrast, no luminescence was observed in the mice implanted with Muse-tk and U87 (Muse-tk:U87 cell ratios of 1:4 and 1:8) from Day 14 onward. Almost all mice survived longer than 100 days and no mouse died as a result of the tumor. CONCLUSIONS: There was a potent in vivo bystander effect between human glioma and Muse-tk cells. The results of the present study suggest that HSVtk/GCV gene therapy using Muse-tk is a promising treatment strategy for malignant glioma.