Uptake of adenoviral vectors via fibroblast growth factor receptors involves intracellular pathways that differ from the targeting ligand

Adeno-Associated Viral Vectors in the Treatment of Epilepsy

Epilepsy is a brain disorder characterized by a persistent predisposition to epileptic seizures. With various etiologies of epilepsy, a significant proportion of patients develop pharmacoresistance to antiepileptic drugs, which necessitates the search for new therapeutic methods, in particular, using gene therapy. This review discusses the use of adeno-associated viral (AAV) vectors in gene therapy for epilepsy, emphasizing their advantages, such as high efficiency of neuronal tissue transduction and low immunogenicity/cytotoxicity. AAV vectors provide the possibility of personalized therapy due to the diversity of serotypes and genomic constructs, which allows for increasing the specificity and effectiveness of treatment. Promising orientations include the modulation of the expression of neuropeptides, ion channels, transcription, and neurotrophic factors, as well as the use of antisense oligonucleotides to regulate seizure activity, which can reduce the severity of epileptic disorders. This review summarizes the current advances in the use of AAV vectors for the treatment of epilepsy of various etiologies, demonstrating the significant potential of AAV vectors for the development of personalized and more effective approaches to reducing seizure activity and improving patient prognosis.

Screening a chemically defined extracellular matrix mimetic substrate library to identify substrates that enhance substrate-mediated transfection

Nonviral gene delivery, though limited by inefficiency, has extensive utility in cell therapy, tissue engineering, and diagnostics. Substrate-mediated gene delivery (SMD) increases efficiency and allows transfection at a cell-biomaterial interface, by immobilizing and concentrating nucleic acid complexes on a surface. Efficient SMD generally requires substrates to be coated with serum or other protein coatings to mediate nucleic acid complex immobilization, as well as cell adhesion and growth; however, this strategy limits reproducibility and may be difficult to translate for clinical applications. As an alternative, we screened a chemically defined combinatorial library of 20 different extracellular matrix mimetic substrates containing combinations of (1) different sulfated polysaccharides that are essential extracellular matrix glycosaminoglycans (GAGs), with (2) mimetic peptides derived from adhesion proteins, growth factors, and cell-penetrating domains, for use as SMD coatings. We identified optimal substrates for DNA lipoplex and polyplex SMD transfection of fibroblasts and human mesenchymal stem cells. Optimal extracellular matrix mimetic substrates varied between cell type, donor source, and transfection reagent, but typically contained Heparin GAG and an adhesion peptide. Multiple substrates significantly increased transgene expression (i.e. 2- to 20-fold) over standard protein coatings. Considering previous research of similar ligands, we hypothesize extracellular matrix mimetic substrates modulate cell adhesion, proliferation, and survival, as well as plasmid internalization and trafficking. Our results demonstrate the utility of screening combinatorial extracellular matrix mimetic substrates for optimal SMD transfection towards application- and patient-specific technologies.

Impact statement

Substrate-mediated gene delivery (SMD) approaches have potential for modification of cells in applications where a cell-material interface exists. Conventional SMD uses ill-defined serum or protein coatings to facilitate immobilization of nucleic acid complexes, cell attachment, and subsequent transfection, which limits reproducibility and clinical utility. As an alternative, we screened a defined library of extracellular matrix mimetic substrates containing combinations of different glycosaminoglycans and bioactive peptides to identify optimal substrates for SMD transfection of fibroblasts and human mesenchymal stem cells. This strategy could be utilized to develop substrates for specific SMD applications in which variability exists between different cell types and patient samples.

Assessment of Specificity of an Adenovirus Targeted to HER3/4

Gene therapy with viral vectors, such as adenovirus (Ad), targeted to the human epidermal growth factor receptors 3 and 4 (HER3/4) are potentially useful for cancer therapy. Testing the expression of a reporter gene from these viruses in target cells is essential to determine functionality of the targeted virus. A competition assay with a relevant ligand (heregulin, HRG) can provide convincing evidence that blocking binding to the HER3/4 receptor results in decreased reporter gene expression. Labeling individual viruses with a fluorescent molecule allows examination of the targeted virus in specific steps in the infection. Virus internalization into cell lines can be determined using antibody-labeled receptors, and the virus colocalization with receptors can also be visualized. Characterization of a targeted virus in this fashion is important to demonstrate that the targeting of the virus functions in an expected manner, and provides support for larger-scale testing of the virus. Information acquired in these experiments may also be useful to inform and improve on the design of future targeted viruses.

Basic fibroblast growth factor-binding peptide as a novel targeting ligand of drug carrier to tumor cells

Drug systems targeting tumor cells using basic fibroblast growth factor (bFGF) have been widely reported. In this study, the peptide KRTGQYKLC (bFGFp), containing cysteine at the carboxyl termination of the bFGF-derived peptide, was applied as a novel ligand targeting tumor cells. bFGFp was conjugated with bovine serum albumin (BSA) and liposomes. The peptide was shown to inhibit the binding of bFGF to FGF receptor-1 (FGFR1). Interestingly, the binding study using surface plasmon resonance (SPR) assay revealed that the bFGFp-BSA was not bound to FGFR1, but was selectively bound to bFGF. Furthermore, the SPR assay showed that bFGFp-BSA is capable of binding to FGFR1 following the pretreatment with bFGF. The confocal microscopy study indicated that the uptake of bFGFp-BSA by NIH3T3 cells, which highly express FGFRs, was significantly enhanced by pretreatment with bFGF. Then, PEGylated liposomes containing bFGFp (bFGFp-liposome) were prepared by conjugating maleimide-PEG-PE with bFGFp. Following the pretreatment of bFGF, the uptake of bFGFp-liposomes by NIH3T3 cells was significantly enhanced. These results suggest that bFGFp-BSA and bFGFp-liposomes are taken by NIH3T3 cells via binding with bFGF. In addition, both bFGFp-BSA and bFGFp-liposomes had no effect on the proliferation of NIH3T3 cells. This strategy can be used as a novel system for targeting tumors highly expressing FGFRs without a proliferation effect.

PEGylated adenovirus for targeted gene therapy

Bifunctional polyethylene glycol (PEG) molecules provide a novel approach to retargeting viral vectors without the need to genetically modify the vector. Modification of the surface of adenovirus with heterofunctional PEG allows further modification of the capsid with ligands. In addition, heterofunctional PEG modification ablates the normal tropism of the virus and reduces transduction of non-target tissues in vivo. Moreover, the addition of PEG chains to the surface of the virus shields antigen-binding sites, significantly reducing the susceptibility of the virus to antibody neutralization. Finally, T cell subsets from mice exposed to the PEGylated vector demonstrate a marked decrease in Th1 and Th2 responses, suggesting that PEG modification may help reduce the immune response to the vector.

Targeting the CYP2B1/Cyclophosphamide Suicide System to Fibroblast Growth Factor Receptors Results in a Potent Antitumoral Response in Pancreatic Cancer Models

The CYP2B1/cyclophosphamide (CPA) suicide gene therapy approach has been shown to be highly promising in clinical trials for the treatment of pancreatic cancer. However, delivering the therapeutic gene to a sufficient number of tumor cells able to trigger a complete response remains a challenge. Target-specific delivery of adenovirus to fibroblast growth factor receptors (FGFRs) has been obtained in a variety of tumor models and has been shown to highly increase transduction efficiency. In the present paper we have tested the therapeutic outcome of retargeting the adenoviral vector, Ad-CYP2B1, to FGFRs, using an FGF2-Fab' conjugate, in pancreatic cancer models. First, we show a heterogeneous subcellular distribution of overexpressed FGFR-1 in pancreatic cancer cells. Higher transduction efficiency was observed in five of the six cell lines studied after FGF2-AdGFPLuc infection. Interestingly, an association between FGFR-1 membrane cell expression and viral entry was found. Moreover, tumors injected with FGF2-AdGFPLuc showed enhanced and persistent transgene expression. Importantly, we demonstrate the relevant enhanced cytotoxic effect of the FGF2-Ad-CYP2B]/CPA system in four of the six cell lines studied. Moreover, retargeting Ad-CYP2B1/CPA to FGFRs resulted in a potent antitumoral effect and in an increased survival rate, in two human pancreatic xenograft models. Thus, our results indicate that redirecting adenoviruses to FGFRs highly increases the potency of the suicide system CYP2B1/CPA. Consequently, it may constitute a promising approach to the treatment of patients with pancreatic tumors, in which a high proportion of FGF receptors precisely localize to the plasma membrane.

FGF Receptor-mediated Gene Delivery using Ligands Coupled to Polyethylenimine

To obtain new nonviral vectors with high gene delivery efficiency and special cell targeting ability, an attractive strategy is to link ligands to polyethylenimine (PEI). Fibroblast growth factor receptors (FGFRs) are highly expressed on a variety of human cancer cells and are potential targets for cancer gene therapy. In this study, the peptides NH2-Met-Gln-Leu-Pro-Leu-Ala-ThrGly-Gly-Gly-Cys-COOH (MC11) which have been proved to combine specially with the FGFR on cell membrane are coupled to PEI using N-Succinimidyl-3-(2-pyridyldithio) propionate (SPDP) as a linker with different molar ratios (1 : 0.3, 1 : 0.75, 1 : 1.5, and 1 : 3.0) and the new polymer PEI-MC11 is verified by a series of physicochemical methods including 1H-NMR and FTIR. The agarose gel electrophoresis assay, particle size test, zeta potential test, and electron microscope observation show that PEI-MC11 can efficiently condense plasmid DNA into nanoparticles with about 200 nm in diameter and with positive surface charge at the suitable N/P ratio. The MTT assay suggests the decreased toxicity of the polymers. The results of the gene delivery efficiency in vitro show that PEI-MC11/pDNA polyplexes have significantly greater transgene activity than PEI/pDNA in COS-7 and HepG2 cells which express FGFR positively, while no such effect is observed in PC3 cells which have negative FGFR. The enhanced gene delivery efficiency of PEI-MC11 can be blocked by the co-culture of free peptides MC11 before the gene delivery procedure. The synthesized nonviral vector based on PEI with the targeting peptides MC11 for binding FGFR has improved efficiency of gene delivery and targeting specificity in FGFR positive cells. It may have potential application in cancer gene therapy.

Retargeting of adenoviral vector using basic fibroblast growth factor ligand for malignant glioma gene therapy

Object. Adenovirus vector (AdV)—mediated gene delivery has been recently demonstrated in clinical trials as a novel potential treatment for malignant gliomas. Combined coxsackievirus B and adenovirus receptor (CAR) has been shown to function as an attachment receptor for multiple adenovirus serotypes, whereas the vitronectin integrins (αvβ3 and αvβ5) are involved in AdV internalization. In resected glioma specimens, the authors demonstrated that malignant gliomas have varying levels of CAR, αvβ3, and αvβ5 expression.

Methods. A correlation between CAR expression and the transduction efficiency of AdV carrying the green fluorescent protein in various human glioblastoma multiforme (GBM) cell lines and GBM primary cell lines was observed. To increase transgene activity in in vitro glioma cells with low or deficient levels of CAR, the authors used basic fibroblast growth factor (FGF2) as a targeting ligand to redirect adenoviral infection through its cognate receptor, FGF receptor 1 (FGFR1), which was expressed at high levels by all glioma cells. These findings were confirmed by in vivo study data demonstrating enhanced transduction efficiency of FGF2-retargeted AdV in CAR-negative intracranial gliomas compared with AdV alone, without evidence of increased angiogenesis.

Conclusions. Altogether, the results demonstrated that AdV-mediated gene transfer using the FGF2/FGFR system is effective in gliomas with low or deficient levels of CAR and suggested that FGF2-retargeting of AdV may be a promising approach in glioma gene therapy.

Bone induction by AdBMP-2/collagen implants

BACKGROUND

Demineralized bone matrix and recombinant human bone morphogenetic protein-2 or 7 (BMP-2 or BMP-7)-containing collagenous matrix have been shown to induce new bone formation in orthotopic and heterotopic sites. We examined the ability of subcutaneous implants of collagen combined with adenoviral vector containing the BMP-2 gene (AdBMP-2) to induce bone formation in rats. We also evaluated whether targeting the AdBMP-2 vector through an alternative receptor pathway, fibroblast growth factor (FGF), would increase the vector's potency.

METHODS

In a time-course study, rat subcutaneous sites were implanted with (1) AdBMP-2 in rat-bone-derived collagen or (2) rat-bone-derived collagen alone. Samples were collected three, seven, fourteen, or thirty-five days after treatment. In a dose-response study, bone induction by AdBMP-2 in collagen (AdBMP-2/collagen) or by AdBMP-2 and FGF2 Fab' anti-adenovirus knob protein antibody in collagen (FGF2-AdBMP-2/collagen) was tested at fourteen days. Viral vector doses of 1 x 10(9) PN (viral particle number), 3 x 10(9) PN, 1 x10(10) PN, 3 x 10(10) PN, or 1 x 10(11) PN per implant were used. Equal amounts of collagen (25 mg) were used to formulate all implants. Explanted tissues were evaluated histologically to determine bone formation, specific activity of alkaline phosphatase, and calcium content.

RESULTS

AdBMP-2/collagen implants induced robust bone formation. New bone was formed by the fourteenth day after implantation. In contrast, little or no bone was induced by the implant containing collagen alone. FGF2-AdBMP-2/collagen implants stimulated significantly more bone formation (p < 0.05) than did AdBMP-2/collagen implants, regardless of the dose of viral particles.

CONCLUSIONS

Local delivery of AdBMP-2 in a collagen matrix rapidly induces bone formation, and targeting the virus through FGF receptors enhances the osteogenic potential of AdBMP-2.

Gene Transfer Mediated by Native versus Fibroblast Growth Factor–Retargeted Adenoviral Vectors into Lung Cancer Cells

We compared native Adenoviral (Ad) vectors to a basic Fibroblast Growth Factor-retargeted Adenovirus (FGF2-Ad) for gene delivery into a diverse panel of lung cancer cells in vitro and xenografts in vivo. Cells were first evaluated for vector-specific receptor expression. Marked variations of surface coxsackie-adenovirus receptor (CAR), but relatively similar levels of alpha v integrin and FGF receptor expression were evident. Transduction efficiency by Ad directly correlated (R = 0.77, 95% CI 0.28-0.94, P = 0.0085) with CAR, but not with alpha v integrin expression. Transduction efficiency by FGF2-Ad did not correlate with the measured FGF receptor expression. Blocking studies indicated that gene transfer by FGF2-Ad occurred by a CAR-independent pathway, and could be inhibited by free FGF in a dose-dependent manner. Ad-antiserum inhibited FGF2-Ad gene transfer, suggesting that the Ad-component was needed for post-entry DNA-delivery. Soluble heparin sulfate proteoglycans (HSPG) or alpha v integrin blockers marginally decreased FGF2-Ad transduction. Both Ad and FGF2-Ad equally transduced CAR-positive non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) cells. By contrast, FGF2-Ad had a distinct transduction advantage in CAR-deficient NSCLC cells. This improvement in transduction of CAR-deficient cells by FGF2-Ad persisted in vivo. These data justify the need for an improved FGF2-Ad vector for clinical use in CAR-deficient lung cancer.

A genetically retargeted adenoviral vector enhances viral transduction in esophageal carcinoma cell lines and primary cultured esophageal resection specimens

OBJECTIVE

To evaluate if an integrin-retargeted adenoviral vector could establish a more efficient and tumor-specific gene transfer in esophageal carcinoma cells.

SUMMARY BACKGROUND DATA

Although preclinical data indicated that adenoviral gene therapy could be a promising novel treatment modality for various malignancies, clinical results are often disappointing. An important problem is the decreased tumoral expression of the Coxsackie and adenovirus receptor (CAR), which mediates adenoviral entry. Retargeting the adenoviral vector to other cellular receptors, by inserting an arginine-glycine-aspartate (RGD) tripeptide in the fiber knob, might overcome this problem.

METHODS

Four esophageal carcinoma cell lines and 10 fresh surgical resection specimens were cultured. All were infected with the native adenovirus (Ad) and the retargeted adenovirus (AdRGD), encoding for the reporter genes luciferase or Green Fluorescent Protein to analyze gene transfer efficiency.

RESULTS

In all cell lines, an increase in viral expression per cell and an increase in the percentage of transduced cells were seen with the retargeted adenovirus. Also, in the primary cultures of carcinoma cells, a more efficient gene transfer was seen when the retargeted vector was used. This phenomenon was less pronounced in normal cells, indicating that the RGD virus transduces tumor cells more efficiently than normal cells.

CONCLUSIONS

This study demonstrates that an RGD retargeted adenovirus infects human esophageal carcinoma cells with enhanced efficiency, while in normal esophageal cells this effect is less pronounced. Therefore, this retargeted vector is expected to have a better performance in vivo, when compared with nonretargeted vectors used for cancer gene therapy so far.

Efficient and selective gene transfer into primary human brain tumors by using single-chain antibody-targeted adenoviral vectors with native tropism abolished

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.

Prostate cancer gene therapy and the role of radiation

Even though prostate cancer is detected earlier than in the pre-PSA era, prostate cancer is the second leading cause of cancer mortality in the American male. Prostate cancer therapy is not ideal, especially for high-risk localized and metastatic cancer; therefore, investigators have sought new therapeutic modalities such as angiogenesis inhibitors, inhibitors of the cell signaling pathway, vaccines, and gene therapy. Gene therapy has emerged as potential therapy for both localized and systemic prostate cancer. Gene therapy has been shown to work supra-additively with radiation in controlling prostate cancer in vivo. With further technological advances in radiation therapy, gene therapy, and the understanding of prostate cancer biology, gene therapy will potentially have an important role in prostate cancer therapy.

Cancer gene therapy: fringe or cutting edge?

Direct targeting of cancer cells with gene therapy has the potential to treat cancer on the basis of its molecular characteristics. But although laboratory results have been extremely encouraging, many practical obstacles need to be overcome before gene therapy can fulfil its goals in the clinic. These issues are not trivial, but seem less formidable than the challenge of killing cancers selectively and rationally--a challenge that has been successfully addressed.