Oncolytic adenovirus: Preclinical and clinical studies in patients with human malignant gliomas

Oncolytic adenoviruses are emerging as a promising alternative therapy for glioma patients and are currently being tested in clinic. In this review, we summarize our experience with gene-based therapy targeting RB pathway in gliomas. Our study has evolved from the development of RB-expressing adenoviral vectors to the characterization of the oncolytic effects on gliomas of the replication competent adenoviruses Delta-24, Delta-24-RGD and ICOVIR. We also review the successful combination of the viruses with chemotherapies that are routinely used in glioma patients, the efficacy of Delta-24-RGD against brain tumor stem cells, the newly described adenovirus-induced autophagy and the potential for the systemic delivery of the oncolytic viruses with human mesenchymal stem cells. Finally, we comment on the preclinical and clinical studies of p53 expressing adenoviral vector and the lessons learned from the experience of Onyx-015, the first oncolytic adenovirus tested in clinical setting.