Viruses in the treatment of brain tumors.

The grave outlook for malignant glioma patients in spite of improvements to current modalities has ushered in new approaches to therapy. Viruses have emerged on the scene and gained attention for their ability to play essentially two roles: first, as vectors for therapeutic gene delivery and second, as engineered infectious agents capable of selectively lysing tumor cells. To date, clinical brain tumor trials using viruses for gene delivery have employed retroviral or adenoviral vectors to introduce ganciclovir susceptibility to tumors in the form of the HSV1-TK gene. Clinical oncolytic studies, on the other hand, have evaluated a conditionally replicating HSV as an antineoplastic agent. Despite some promise afforded by these trials, further studies are warranted; the investigation of additional viruses to play these roles is inevitable and is now precedented.