Lidia Rodríguez García [email protected] Bachelor’s degree final project-Biochemistry, Faculty of Biosciences, Universitat Autònoma de Barcelona, June 2014 INTRODUCTION- Oncolytic Virotherapy Cancer is the main cause of death of the world. The main goal of the investigation in cancer field is to find less aggressive and more effective and specific treatments. A century ago, viruses began to have considerable interest as possible agents of tumor destruction since some clinical remissions were seen in cancer patients during naturally acquired virus infections. Viral therapy is based on the ability of certain viruses to replicate selectively and kill cancer cells without causing harm to normal tissues. The initial dose is self-amplified in tumor sites and viral progeny produced within the dying cancer cell is released and infect adjacent and/or distant cancer cells. Tumor selective replication and cell lysis ONCOLYITIC ADENOVIRUS AND STRUCTURE – Are mildly pathogenic in human→ safety profile – Infect quiescent and dividing cells – Cause lysis on the infected cells – Are not integrative – Are genetically stable – Can be easily manipulated Fiber – Can be produced at large scale Hexon Infection of tumor cell Viral dispersion SELECTIVE - REPLICATION Adenoviruses are genetically modified to redirect its tropism and achieve selective replication in tumor cells by using three strategies: 1. Deletion of viral functions that confer tumor selectivity thanks to the phenotypic differences between tumor and normal cells. 2. Control of protein expression under tumor-specific promoters (transcriptional and translational targeting). 3. Modification of the capsid proteins to redirect adenovirus tropism (transductional targeting). ITR E1A promoters E1B 2. 1. Penton base hexon/fiber LIMITATIONS Poor tumor targeting after intravenous administration: • • Reinfection and elimination of cancer cells Interaction with blood cells and complement → neutralization Accumulation in non-target organs → liver and spleen sequestration. Capsid modifications • ITR Deficient intratumoral spread: Stroma barriers and high intersticial pressure →no extravasation. Express matrix degrading enzymes 3. SOME EXAMPLES ONYX-015 replicate specifically in p53-deficient tumors thanks to the lack of E1B-55 kb gene, whose protein binds and inactivates the pro-apoptotic p53 protein (Figure). Its derivate H101, was the first approved and commercialized oncolytic adenovirus (2005). CG0070 is the most promising oncolytic adenovirus of the moment, which replicates in Rb-pathway defective tumor cells and express an immunostimulatory gene to enhance immune response against the tumor. CONCLUSIONS 1. Virotherapy is a good alternative of the currenly used treatments. 2. Adenovirus can now be genetically engineered to redirect its tropism and selectively replicate in tumor cells without causing toxicity in other organs. 3. Replication in cancer cells will amplify the input virus potentially leading to spread of the virus and the amplification of the initial dose in tumor site. 4. Oncolytic adenoviruses can be armed with transgenes which helps in the dissemination through the tumor and with immunostimulatory genes, to generate a systemic immune response against the tumor. 5. Combination with convecional cancer therapies (chemotherapy and radiotherapy) improves the antitumor activity of oncolytic agents. REFERENCES [1] Stephen J Russell, Kah Whye Peng, John C Bell (2012). Oncolytic virotherapy. Nature Biotechnology 30: 1-13. [2] Elizabeth Kelly, Stephen J Russell (2007). History of Oncolytic Viruses: Genesis to Genetic Engineering. Molecular Therapy 15: 651-659 [3] Roland L. Chu, Dawn E. Post, Fadlo R. Khuri, et al. (2004). Use of Replicating Oncolytic Adenoviruses in Combination Therapy for Cancer. Clin Cancer Res,10: 5299-5312. [4] T-C Liu, D Kirn (2008). Gene therapy progress and prospects cancer: oncolytic viruses. Gene Therapy 15: 877-884.