Targeted AAVP-based therapy in a mouse model of human glioblastoma: a comparison of cytotoxic versus suicide gene delivery strategies

Abstract

Glioblastoma persists as a uniformly deadly diagnosis for patients and effective therapeutic options are gravely needed. Recently, targeted gene therapy approaches are re-emerging 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 anti-tumor 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 suicide gene therapy. Both AAVP constructs demonstrated anti-tumor 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.

Design and proof-of-concept for targeted phage-based COVID-19 vaccination strategies with a streamlined cold-free supply chain

“…These results confirm that gene delivery by AAVP and the expression of the S protein in the draining lymph nodes trigger a systemic S protein-specific humoral response. Moreover, the data recapitulate the well-established attribute of AAVP particles in preventing off-target effects, even upon clearance via the reticulum-endothelial system (RES), sparing non-targeted or distal tissues, while a strong promoter drives the expression of the transgene in the transduced cells (20, 23-28). This finding is particularly important for evaluating potential adverse effects in novel, candidate AAVP-based vaccines, since off-site transduction-associated toxicities have been reported in toxicological studies of adenovirus vaccines (48, 49).…”

Development of iRGD-Modified Peptide Carriers for Suicide Gene Therapy of Uterine Leiomyoma

“…HSV-1 TK, but not mammalian TK, effectively phosphorylates these analogues, which leads to their incorporation into DNA, premature replication termination and as a result induces apoptotic cell death [ 11 ]. Importantly, the suicide gene therapy application gives rise to the “bystander effect”, which is that a higher percentage of tumor cell death occurs with a lower percentage of transfected cells [ 12 , 13 , 14 ]. This phenomenon increases the efficacy of the suicide gene therapy.…”

“…For example, αvβ3 integrins are significantly upregulated in uterine leiomyoma cells as compared to normal myometrium that makes this receptors perspective for targeted gene therapy of UL [ 35 ]. Linear RGD and different cyclic RGD-ligands have been developed and actively studied for tumor targeting [ 2 , 14 , 36 , 37 , 38 , 39 ]. Compared to linear RGD sequences, cyclic ones favor in selectivity and stability and are widely used for strong binding to αv-integrins.…”

Doxorubicin Improves Cancer Cell Targeting by Filamentous Phage Gene Delivery Vectors

“…Upon cell entry of the hybrid RGD4C/AAV-phage (RGD4C/AAVP), the AAV transgene cassette is released, resulting in gene expression in tumors from a cytomegalovirus, CMV , promoter [ 5 , 6 ]. We have reported that this vector targets numerous cancer models in vivo upon intravenous delivery [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. A study in pet dogs with spontaneous cancers proved the safety of repeated vector dosing, resulting in complete tumor eradication in a few dogs with aggressive cancers [ 20 ].…”