GENE-THERAPY AGAINST AN EXPERIMENTAL GLIOMA USING ADENOASSOCIATED VIRUS VECTORS

The efficacy of gene therapy for glioma was examined using adeno-assoc iated virus (AAV)-based vectors to deliver genes to experimental tumor s in mice. Stereotactic injection of 2 x 10(5) U-251SP human glioma ce lls into the brains of nude mice produced tumors of 19.06 +/- 1.79 mm( 2) 17 days after injection. Employing a high titer preparation of AAV vector containing the gene for beta-galactosidase (AAV-lacZ), dose-dep endent transduction of U-251SP cells was seen in vitro. When 1.6 x 10( 10) AAV-lacZ particles were directly injected into tumors in vivo, 30- 40% of the cells along the needle track expressed beta-galactosidase. Transduction of U-251SP cells in vitro with an AAV vector containing a bicistronic gene encoding both herpes simplex thymidine kinase and hu man interleukin-2 (AAV-tk-IRES-IL2) rendered them sensitive to the cyt ocidal effects of ganciclovir (GCV) and IL-2 was produced in a dose-de pendent manner. Cocultures of AAV-tk-IRES-IL2 transduced cells and non transduced cells proved highly sensitive to GCV indicating the contrib ution of the bystander effect. Stereotactic delivery of 6 x 10(10) AAV -tk-IRES-IL2 particles into day 7 tumors in nude mice followed by admi nistration of GCV for 6 days, resulted in a 35-fold reduction in the m ean volume of tumors compared with controls. Normal brains did not suf fer from any toxic effect of the administration of AAV-tk-IRES-IL2 and GCV. These results indicate that high titer AAV vector treatment may be safe and effective for in vivo gene therapy of human brain tumors.