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Efficient and selective gene transfer into primary human brain tumors by using single-chain antibody-targeted
Victor W van Beusechem1, Jacques Grill, D C Jeroen Mastenbroek
1Division of Gene Therapy, Department of Medical Oncology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands. vw.van_beusechem.oncol@med.vu.nl
Abstract:
The application of adenoviral vectors in cancer gene therapy is hampered by low receptor expression on tumor cells and high receptor expression on normal epithelial cells. Targeting adenoviral vectors toward tumor cells may improve cancer gene therapy procedures by providing augmented tumor transduction and decreased toxicity to normal tissues. Targeting requires both the complete abolition of native tropism and the addition of a new specific binding ligand onto the viral capsid. Here we accomplished this by using doubly ablated adenoviral vectors, lacking coxsackievirus-adenovirus receptor and alpha(v) integrin binding capacities, together with bispecific single-chain antibodies targeted toward human epidermal growth factor receptor (EGFR) or the epithelial cell adhesion molecule. These vectors efficiently and selectively targeted both alternative receptors on the surface of human cancer cells. Targeted doubly ablated adenoviral vectors were also very efficient and specific with primary human tumor specimens. With primary glioma cell cultures, EGFR targeting augmented the median gene transfer efficiency of doubly ablated adenoviral vectors 123-fold. Moreover, EGFR-targeted doubly ablated vectors were selective for human brain tumors versus the surrounding normal brain tissue. They transduced organotypic glioma and meningioma spheroids with efficiencies similar to those of native adenoviral vectors, while exhibiting greater-than-10-fold-reduced background levels on normal brain explants from the same patients. As a result, EGFR-targeted doubly ablated adenoviral vectors had a 5- to 38-fold-improved tumor-to-normal brain targeting index compared to native vectors. Hence, single-chain targeted doubly ablated adenoviral vectors are promising tools for cancer gene therapy. They should provide an improved therapeutic index with efficient tumor transduction and effective protection of normal tissue.
Insights
Targeted adenoviral vectors enhance cancer gene therapy by selectively delivering genes to tumors, improving efficacy and reducing side effects on healthy tissues.
Area of Science:
- Oncology
- Gene Therapy
- Virology
Background:
- Adenoviral vectors face challenges in cancer gene therapy due to variable receptor expression on tumor and normal cells.
- Targeting adenoviral vectors can improve tumor transduction and decrease normal tissue toxicity.
Purpose of the Study:
- To develop doubly ablated adenoviral vectors with enhanced tumor-specific targeting for cancer gene therapy.
- To evaluate the efficacy and specificity of these targeted vectors against human cancer cells and tissues.
Main Methods:
- Engineered doubly ablated adenoviral vectors lacking native tropism.
- Incorporated bispecific single-chain antibodies targeting EGFR or epithelial cell adhesion molecule.
- Tested vector targeting and gene transfer efficiency on human cancer cell lines, primary tumor specimens, and organotypic brain tumor models.
Main Results:
- Targeted vectors efficiently and selectively bound to human cancer cells expressing EGFR or epithelial cell adhesion molecule.
- EGFR-targeted vectors increased gene transfer efficiency by 123-fold in glioma cells.
- Vectors demonstrated selectivity for brain tumors over normal brain tissue, with a 5- to 38-fold improved targeting index.
Conclusions:
- Doubly ablated adenoviral vectors targeted with single-chain antibodies show promise for cancer gene therapy.
- These targeted vectors offer efficient tumor transduction and protection of normal tissues, improving the therapeutic index.
