1. ¹Brain Tumor Center, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
2. ²Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA

Correspondence: Marta M. Alonso, Department of Neuro-Oncology, Box 1002, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030, USA. E-mail: mmalonso@mdanderson.org

The last two authors contributed equally to this work.

Received 16 July 2007; Accepted 29 November 2007; Published online 5 February 2008.

Abstract

Novel therapies are clearly needed for the treatment of gliomas, and strategies that involve combining oncolytic vectors with chemotherapy hold out significant hope for a more effective treatment of this malignancy. Whether chemotherapy acts directly on tumor cells by inducing cell arrest or cell death, or indirectly by blocking tumor angiogenesis, the resulting delay in tumor growth may provide the oncolytic virus with a wider window of opportunity to overcome the challenge imposed by the growth kinetics of the tumor. In this study we sought to determine whether the oncolytic adenovirus Delta-24-RGD, in combination with everolimus (RAD001), would result in an enhanced anti-glioma effect in vivo. Viability assays showed that Delta-24-RGD antitumoral activity is synergistically enhanced by combination with RAD001. Interestingly, combination treatment of Delta-24-RGD with RAD001 induced autophagy in vitro. We showed that Delta-24-RGD improved survival of tumor-bearing animals in a dose-dependent manner. A significant finding was that RAD001 enhanced the anti-glioma effect of Delta-24-RGD and resulted in the long-term survival of 80% of the experimental animals. Immunostaining of the treated tumors showed upregulation of Atg5, thereby indicating the therapeutic induction of autophagy. This is the first report showing that Delta-24-RGD plus RAD001 causes autophagic cell death, and dramatically increases long-term survival rates of glioma-bearing animals.