Thymidine kinase-mediated killing of rat brain tumors

Abstract
✓ Gene therapy has many potential applications in central nervous system (CNS) disorders, including the selective killing of tumor cells in the brain. A rat brain tumor model was used to test the herpes simplex virus (HSV)-thymidine kinase (TK) gene for its ability to selectively kill C6 and 9L tumor cells in the brain following systemic administration of the nucleoside analog ganciclovir. The HSV-TK gene was introduced in vitro into tumor cells (C6-TK and 9L-TK), then these modified tumor cells were evaluated for their sensitivity to cell killing by ganciclovir. In a dose-response assay, both C6-TK and 9L-TK cells were 100 times more sensitive to killing by ganciclovir (median lethal dose: C6-TK, 0.1 µg ganciclovir/ml; C6, 5.0 µg ganciclovir/ml) than unmodified wild-type tumor cells or cultured fibroblasts. In vivo studies confirmed the ability of intraperitoneal ganciclovir administration to kill established brain tumors in rats as quantified by both stereological assessment of brain tumor volumes and s...