Gene therapy for brain tumors: the fundamentals

BACKGROUND: Over the past two decades, significant advances have been made in the fields of virology and molecular biology, and in understanding the genetic alterations present in brain tumors. The knowledge gained has been exploited for use in gene therapy. OBJECTIVE: The purpose of this article is to present an introduction to the field of brain tumor gene therapy for the practicing clinician. RESULTS: A variety of gene therapy strategies have now been used in the laboratory and in clinical trials for brain tumors. They can be divided into five categories: 1) gene-directed enzyme prodrug ("suicide gene") therapy (GDEPT); 2) gene therapy designed to boost the activity of the immune system against cancer cells; 3) oncolytic virus therapy; 4) transfer of potentially therapeutic genes--such as tumor suppressor genes--into cancer cells; and 5) antisense therapy. GDEPT is the strategy that has been most extensively studied. CONCLUSIONS: To date, gene therapy has been found to be reasonably safe and concerns related to adverse events such as insertional mutagenesis have not been realized. Although patients have not been cured, the development of this therapy could still be considered to be at an early stage. Current research is addressing factors that could be limiting the successful clinical application of gene therapy, which remains an intriguing experimental option for patients with malignant brain tumors.