Incorporation of a laminin-derived peptide (SIKVAV) on polymer-modified adenovirus permits tumor-specific targeting via α6-integrins

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 a6b1 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 a6-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-a6 integrin and anti-b1 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 a6b1 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.

A novel vector for a rapid generation of fiber-mutant adenovirus based on one step ligation and quick screening of positive clones

“…In addition, a peptide SIK-VAV was recently showed to be able to bind to alpha integrin and chemically modified adenoviral vector using SIKVAV peptide could increase gene transfer to alpha integrin positive cells (Stevenson et al, 2007). In the present study, we tested our newly developed system by taking advantage of these small peptides.…”

Circumventing Antivector Immunity: Potential Use of Nonhuman Adenoviral Vectors

“…Moreover, coated HAdV vectors induce lower IL-6 levels in serum because of decreased levels of spleen AdV uptake (De Geest et al, 2005). Furthermore, several groups successfully retargeted coated AdV vectors (Parker et al, 2005;Stevenson et al, 2007;Morrison et al, 2008Morrison et al, , 2009Wang et al, 2010). Although in some studies they presented similar levels of antitumoral efficacy (Morrison et al, 2009) or transgene expression (Parker et al, 2005;Stevenson et al, 2007;Morrison et al, 2008;Wang et al, 2010) to unmodified wild-type HAdV-5, others achieved a greater therapeutic effect with negligible side effects (Eto et al, 2010;Yao et al, 2010).…”

Multi-component Polymeric System for Tumour Cell-Specific Gene Delivery Using a Universal Bungarotoxin Linker

“…It has been demonstrated that modification of adenoviruses with hydrophilic synthetic polymers based on poly(ethylene glycol) (PEG) (7) or N-(2-hydroxypropyl) methacrylamide copolymer (PHPMA) (8,9) significantly prolongs plasma circulation times and ablates non-specific cell entry. In addition, surface modification of the adenovirus capsid with multivalent polymers provides a platform for retargeting with receptor-specific ligands, such as growth factors (10), tumour-specific peptides (11) or folates (12). However, the covalent attachment of targeting ligand to the coating polymer suffers from several limitations.…”