Abstract
Glioblastoma persists as a uniformly deadly diagnosis for patients and effective therapeutic options are gravely needed. Recently, targeted gene therapy approaches are reemerging as attractive experimental clinical agents. Our ligand-directed hybrid virus of adeno-associated virus and phage (AAVP) is a targeted gene delivery vector that has been used in several formulations displaying targeting ligand peptides to deliver clinically applicable transgenes. Here we compared different constructs side-by-side in a tumor model, an orthotopic model of xenograft human glioblastoma cells stereotactically implanted in immunodeficient mice. We have used divergent therapeutic strategies for two AAVP constructs, both displaying a double-cyclic RGD4C motif ligand specific for alpha V integrins expressed in tumor vascular endothelium, but carrying different genes of interest for the treatment of intracranial xenografted tumors. One construct delivered tumor necrosis factor (TNF), a purely cytotoxic gene for antitumor activity (RGD4C-AAVP-TNF); in the other construct, we delivered Herpes simplex virus thymidine kinase (HSVtk) for in tandem molecular-genetic imaging and targeted therapy (RGD4C-AAVP-HSVtk) utilizing ganciclovir (GCV) for a suicide gene therapy. Both AAVP constructs demonstrated antitumor activity, with damage to the tumor-associated neovasculature and induction of cell death evident after treatment. In addition, the ability to monitor transgene expression with a radiolabeled HSVtk substrate pre and post GCV treatment demonstrated the theranostic potential of RGD4C-AAVP-HSVtk. We conclude that targeted AAVP constructs delivering either cytotoxic TNF or theranostic HSVtk followed by suicide gene therapy with GCV have comparable preclinical efficacy, at least in this standard experimental model. The results presented here provide a blueprint for future studies of targeted gene delivery against human glioblastomas and other brain tumors.
Highlights
We have previously shown the ligand-directed delivery of a tumor necrosis factor (TNF) transgene to tumors in the setting of human melanoma xenografts [7, 8], a transgenic model of pancreatic neuroendocrine tumors [9], and even in spontaneous native tumors in pet dogs [10] consistently produced antitumor effects without evidence of off-target side effects, a major concern of nontargeted systemic TNF therapy, which is known for severe toxicity [11]
Since integrin subunit αv is highly expressed both in tumor cells and in angiogenic vasculature in glioblastomas [16,17,18], here we evaluate two parallel strategies for ligand-directed therapy with a cytotoxic agent (TNF) versus a theranostic (HSVtk) gene delivery followed by suicide gene therapy with GCV in the same orthotopic mouse model of human glioblastoma with RGD4C-directed associated virus and phage (AAVP) vectors
We first set out to evaluate the translational potential of RGD4C-AAVP-TNF in an experimental orthotopic preclinical model of human glioblastoma cells stereotactically implanted in immunodeficient mice
Summary
Glioblastomas are lethal intracranial tumors of the central nervous system characterized by high morbidity and mortality due to their high tumor cell proliferation rate and University, Detroit, MI, USA. AAVP has been engineered to contain a Herpes simplex virus-1 thymidine kinase (HSVtk) transgene, which serves as both a reporter for clinically applicable positron emission tomography (PET) imaging with HSVtk-specific radiolabeled nucleoside analogs, such as [18F]-FEAU, and/or a suicide gene therapy strategy when combined with ganciclovir (GCV). This theranostic convergence of molecular-genetic imaging and targeted therapy has shown promise in preclinical models of several solid tumor types [6, 12,13,14,15]. By administering a radiolabeled HSVtk substrate, these tumors could be imaged horizontally during the course of the study to evaluate transgene expression over time, a transgenespecific tool potentially useful for timing GCV and for evaluating tumor response, a feature not currently available with the cytotoxic TNF vector
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
