1. ¹Department of Clinical Pharmacology, University of Oxford, Oxford, UK
2. ²Hybrid Systems Ltd, Cherwell Innovation Centre, Oxfordshire, UK
3. ³Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
4. ⁴Cancer and Metastasis Department, Institut de Recerca Oncologica, Hospital Duran y Reynals, Ciutat Sanitaria Bellvitge, Barcelona, Spain

Correspondence: Dr M Stevenson, Department of Clinical Pharmacology, University of Oxford, Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, UK. E-mail: mark.stevenson@clinpharm.ox.ac.uk

Received 7 July 2006; Revised 30 September 2006; Accepted 18 November 2006; Published online 19 January 2007.

Abstract

Effective gene therapy for disseminated metastatic cancer is currently impossible because of poor delivery of vector to target sites. Modification of viral vectors to target advanced cancer has long been a challenge. In this study, we aimed to redirect adenovirus tropism to infect prostate cancer cells via 61 integrins, whose expression is upregulated during prostate cancer progression. To ablate normal mechanisms of infection and provide a framework for attachment of targeting ligands, viruses were non-genetically modified with pHPMA-ONp polymer. Addition of polymer-coated virus to prostate cells showed significantly reduced transgene expression compared with unmodified virus. To restore infectivity, an 6-integrin binding peptide (-SIKVAV-) derived from laminin was incorporated onto the surface of the polymer-coated viruses. Photon correlation spectroscopic analysis revealed a small increase in the mean diameter of the particles following retargeting. Addition of -SIKVAV- peptide restored virus infectivity of PC-3 cells in a ligand concentration-dependent manner that was significantly improved following removal of unincorporated polymer and peptide. Competition assays using cells preincubated with Ad5 fiber protein or free -SIKVAV- peptide confirmed that entry of retargeted viruses was mediated via the incorporated ligand. Application of retargeted viruses to a panel of human cell lines revealed varying levels of transduction efficiency. Flow cytometric analysis of cells using anti-6 integrin and anti-1 integrin antibodies demonstrated that for prostate cells, greater transduction efficiency correlated with higher levels of expression of both integrin subunits. Furthermore with the exception of LNCaP cells, increased 61 integrin expression correlated with advanced disease. Intravenous administration of retargeted viruses to tumor-bearing mice resulted in slower plasma clearance and greatly reduced liver tropism, and hence toxicity compared with unmodified virus, while maintaining reporter gene expression in the tumor. The data suggest that YESIKVAVS-retargeted viruses have potential for systemic delivery for the treatment of metastatic disease.