Adenovirally mediated gene transfer into experimental solid brain tumors and leptomeningeal cancer cells

Among the appealing features of adenoviruses as vectors for transfer of genes into the central nervous system (CNS) are that they are not neurotoxic, they can accommodate the insertion of several large genes, they are not associated with the hazards of insertional mutagenesis, and they can be concentrated to a high-titer preparation. The authors evaluated the feasibility of using adenovirally mediated gene transfer into cultured human glioma cells and in rat models of solid brain tumors and meningeal cancer. Replication-deficient adenoviral vector particles carrying a nuclear- localizing lacZ gene were injected into established 9L cerebral gliomas in Fischer rats. In addition, the adenoviral vector was injected into the subarachnoid space, either simultaneously with intrathecal tumor inoculation or after establishing leptomeningeal cancer. The brains and spinal cords were removed at various intervals for histochemical evaluation for β- galactosidase activity using X-Gal staining. Additional rats received a stereotactic intracerebral injection of the vector into normal brain. No clinical abnormalities were observed in the injected rats. Injection of the adenoviral vector into normal brain resulted in diffuse transduction of astrocytes, microglia, neurons, and endothelial cells at the injection site. Injection of a high-concentration vector preparation into cerebral gliomas resulted in effective tumor transduction. Intrathecal injection of the vector in rats with meningeal cancer resulted in transduction of the infiltrating tumor in the subarachnoid space when injections were given simultaneously with, or 7 days after, tumor inoculation. Transduction rates of both solid and leptomeningeal tumors correlated with the number of injected particles. These results suggest that adenoviral vectors can efficiently transduce solid brain tumors and that the vectors survive in the cerebrospinal fluid for a sufficient period of time to allow leptomeningeal tumor transduction. Adenoviral vector should be evaluated for its potential use in therapeutic gene transfer approaches in malignancies of the CNS.