Transgene expression is increased by photochemically mediated transduction of polycation-complexed adenoviruses

Photochemical Internalization for Intracellular Drug Delivery. From Basic Mechanisms to Clinical Research

Photochemical internalisation (PCI) is a unique intervention which involves the release of endocytosed macromolecules into the cytoplasmic matrix. PCI is based on the use of photosensitizers placed in endocytic vesicles that, following light activation, lead to rupture of the endocytic vesicles and the release of the macromolecules into the cytoplasmic matrix. This technology has been shown to improve the biological activity of a number of macromolecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins (RIPs), gene-encoding plasmids, adenovirus and oligonucleotides and certain chemotherapeutics, such as bleomycin. This new intervention has also been found appealing for intracellular delivery of drugs incorporated into nanocarriers and for cancer vaccination. PCI is currently being evaluated in clinical trials. Data from the first-in-human phase I clinical trial as well as an update on the development of the PCI technology towards clinical practice is presented here.

Cystic Fibrosis, Cystic Fibrosis Transmembrane Conductance Regulator and Drugs: Insights from Cellular Trafficking

The eukaryotic cell is organized into membrane-delineated compartments that are characterized by specific cadres of proteins sustaining biochemically distinct cellular processes. The appropriate subcellular localization of proteins is key to proper organelle function and provides a physiological context for cellular processes. Disruption of normal trafficking pathways for proteins is seen in several genetic diseases, where a protein's absence for a specific subcellular compartment leads to organelle disruption, and in the context of an individual, a disruption of normal physiology. Importantly, several drug therapies can also alter protein trafficking, causing unwanted side effects. Thus, a deeper understanding of trafficking pathways needs to be appreciated as novel therapeutic modalities are proposed. Despite the promising efficacy of novel therapeutic agents, the intracellular bioavailability of these compounds has proved to be a potential barrier, leading to failures in treatments for various diseases and disorders. While endocytosis of drug moieties provides an efficient means of getting material into cells, the subsequent release and endosomal escape of materials into the cytosol where they need to act has been a barrier. An understanding of cellular protein/lipid trafficking pathways has opened up strategies for increasing drug bioavailability. Approaches to enhance endosomal exit have greatly increased the cytosolic bioavailability of drugs and will provide a means of investigating previous drugs that may have been shelved due to their low cytosolic concentration.

Asymmetric polyplex-nanocapsules loaded with photosentisizer for light-assisted gene transfer

Inefficient intracellular gene delivery is still a limitation for the clinical translation of gene therapy. Recently, photochemical internalization (PCI) has emerged with the opportunity to overcome endo-lysosomal sequestration in gene delivery, which utilizes photosensitizer (PS) plus light generating reactive oxygen species (ROS) at sub-lethal level to facilitate intracellularly targeted drug delivery. In this work, asymmetric polyplex-nanocapsules were prepared based on the triblock copolymers of PEG-PCL-PEI by using the simple solvent-injection method. Subsequently, the hydrophobic PS was encapsulated in the hydrophobic layer of polyplex-nanocapsules through hydrophobic interaction. The results from agarose gel electrophoresis and fluorescence scanning spectroscopy show that DNA could be condensed effectively and the PS was encapsulated, resulting in the stable polyplex-nanocapsules. The obtained polyplex-nanocapsules were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements with the average size ranging from 200 to 280nm and the negatively charged surface. Importantly, these polyplex-nanocapsules can be uptaken by Hela cells, resulting in improved gene transfection efficiency in comparison with the case without laser treatment due to the assistance of PCI effect. This work demonstrates a promising strategy to build the light-assisted gene delivery system containing PS and transporting genes simultaneously in one platform.

Enhanced Cell Growth Inhibition following PTEN Nonviral Gene Transfer Using Polyethylenimine and Photochemical Internalization in Endometrial Cancer Cells

PTEN is a tumor suppressor gene mapped on chromosome 10q23.3 and encodes a dual specificity phosphatase. PTEN has major implication in PI3 kinase (PI3K) signal transduction pathway and negatively controls PI3 phosphorylation. It has been reported to be implicated in cell cycle progression and cell death control through inhibition of PI3K-Akt signal transduction pathway and in the control of cell migration and spreading through its interaction with focal adhesion kinase. Somatic mutations of PTEN are frequently detected in several cancer types including brain, prostate and endometrium with more than 30% of tumor tissue specimens bearing PTEN mutations and/or deletions. Because of its high frequency of mutations and its important function as tumor suppressor gene, PTEN is a good candidate for gene therapy. Inducible expression of PTEN has been also reported. In cancer cells bearing PTEN abnormalities, the reversion of PTEN function by external gene transfer becomes more and more investigated in cancer treatment research. Several technologies including the photochemical internalization (PCI) and aiming at improving the transfection efficiency have been reported. PCI is an innovative procedure based on light-induced delivery of macromolecules such as DNA, proteins and other therapeutic molecules from endocytic vesicles to the cytosol of target cells. PCI has been reported to enhance the gene delivery potential of viral and nonviral vectors. The present study was designed to evaluate the influence of photochemical internalization on polyethylenimine (PEI)-mediated PTEN gene transfer and its effects on the cellular viability in Ishikawa endometrial cancer cells bearing PTEN abnormalities. PCI was found to significantly (P < 0.01) enhance PTEN mRNA expression (4.2 fold increase). Subsequently, following PEI-mediated PTEN gene transfer, the restoration of the PTEN protein expression was observed. As a consequence, significant cell growth inhibition (44%) was observed in Ishikawa endometrial cells. Using PCI for PEI-mediated PTEN gene transfer was found to further enhance PTEN mRNA and protein expression as well as PTEN-related cell growth inhibition reaching 89%.

Enhancing the therapeutic efficacy of adenovirus in combination with biomaterials

With the reason that systemically administered adenovirus (Ad) is rapidly extinguished by innate/adaptive immune responses and accumulation in liver, in vivo application of the Ad vector is strictly restricted. For achieving to develop successful Ad vector systems for cancer therapy, the chemical or physical modification of Ad vectors with polymers has been generally used as a promising strategy to overcome the obstacles. With polyethylene glycol (PEG) first in order, a variety of polymers have been developed to shield the surface of therapeutic Ad vectors and well accomplished to extend circulation time in blood and reduce liver toxicity. However, although polymer-coated Ads can successfully evacuate from a series of guarding systems in vivo and locate within tumors by enhanced permeability and retention (EPR) effect, the possibility to entering into the target cell is few and far between. To endow targeting moiety to polymer-coated Ad vectors, a diversity of ligands such as tumor-homing peptides, growth factors or antibodies, have been introduced with avoiding unwanted transduction and enhancing therapeutic efficacy. Here, we will describe and classify the characteristics of the published polymers with respect to Ad vectors. Furthermore, we will also compare the properties of variable targeting ligands, which are being utilized for addressing polymer-coated Ad vectors actively.

Photochemical internalization: a new tool for gene and oligonucleotide delivery

Photochemical internalization (PCI) is a novel technology for release of endocytosed macromolecules into the cytosol. The technology is based on the use of photosensitizers located in endocytic vesicles. Upon activation by light such photosensitizers induce a release of macromolecules from their compartmentalization in endocytic vesicles. PCI has been shown to increase the biological activity of a large variety of macromolecules and other molecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins, immunotoxins, plasmids, adenovirus, various oligonucleotides, dendrimer-based delivery of chemotherapeutica and unconjugated chemotherapeutica such as bleomycin and doxorubicin. This review will present the basis for the PCI concept and the most recent significant developments.

Laser-based gene transfection and gene therapy

The plasma membrane of mammalian cells can be transiently permeablized by optical means and exogenous materials or genes can be introduced into the cytoplasm of living cells. Until now, few mechanisms were exploited for the manipulation: laser is directly and tightly focused on the cells for optoinjection, laser-induced stress waves, photochemical internalization, and irradiation of selective cell targeting with light-absorbing particles. During the past few years, extensive progress and numerous breakthroughs have been made in this area of research. This review covers four different laser-assisted transfection techniques and their advantages and disadvantages. Universality towards various cell lines is possibly the main advantage of laser-assisted optoporation in comparison with presently existing methods of cell transfection.

Pulmonary delivery of adenovirus vector formulated with dexamethasone–spermine facilitates homologous vector re-administration

Gene transfer to lung has been hindered by inflammatory and immunological responses activated to the gene-transfer agent or transgene products. In prior work, adenovirus vector delivered to the lung with the cationic glucocorticoid, dexamethasone-spermine (DS) had improved targeting to conducting airway epithelium and reduced cellular infiltration. In this study, the effect of formulation on homologous adenovirus vector re-administration was studied in C57Bl/6 mice. Formulation of an adenovirus vector expressing LacZ with DS/dioleoylphosphatidylethanolamine (DOPE) delivered at day 0 allowed re-administration of adenovirus vector expressing alkaline phosphatase at day 21. Formulation with 3beta [N-(N', N'-dimethylaminoethane) carbamoy] cholesterol (DC-Chol) DC-cholesterol (DC-Chol))/DOPE or dexamethasone in the first dosing at day 0 resulted in moderate alkaline phosphatase expression at day 24. Neutralizing antibodies against adenovirus vector in serum at day 28 were greatly reduced by all three formulations in mice receiving a single dose of adenovirus at day 0. Also, homologous adenovirus vector re-administration at day 14 produced less neutralizing antibody at day 28 when adenovirus was formulated with DS/DOPE at day 0. The use of DS/DOPE at day 0 dramatically reduced CD4 and CD8 T-cell infiltration in mice receiving adenovirus at day 0 followed by vector re-administration at day 14. Transgene-specific T-cell activation was markedly reduced by the DC-Chol/DOPE formulation. Overall, DS/DOPE) facilitated homologous vector re-administration through a combination of liposomal and glucocorticoid mechanisms.

Photochemically enhanced transduction of polymer-complexed adenovirus targeted to the epidermal growth factor receptor

BACKGROUND

The development of methods for specific delivery of genes into target tissues is an important issue for the further progress of gene therapy. Biological and physical targeting techniques may be combined to redirect gene therapy vectors to specific cells and enhance gene transfer.

METHODS

The polymer poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) was conjugated with avidin or poly(ethylene glycol) (PEG) and complexed with adenovirus serotype 5 (Ad5). Targeting of polymer-coated Ad5 to the epidermal growth factor receptor (EGFR) was accomplished by the binding of biotin-EGF to pDMAEMA-avidin. A photochemical treatment procedure using photosensitizer and light was applied to increase transduction with EGFR-targeted viral complexes.

RESULTS

pDMAEMA-avidin efficiently enhanced transduction through unspecific viral uptake into cells, while pDMAEMA-PEG provided charge shielding of the complexes and increased the specificity to EGFR when biotin-EGF ligands were used. Transduction of PEG-containing, EGFR-targeted viral complexes was inhibited by 66% in coxsackie and adenovirus receptor (CAR)-deficient RD cells and by 47% in CAR-expressing DU 145 cells in receptor antibody experiments. The photochemical treatment had a substantial effect on transduction, enhancing the percentage of reporter gene positive cells from 20% to 75% of the total viable RD cell population and from 10% to 70% in DU 145 cells.

CONCLUSION

Photochemical treatment of cells infected with targeted viral vectors exhibiting a neutral surface charge is a potent method for enhancing transgene expression.

Photochemical treatment with endosomally localized photosensitizers enhances the number of adenoviruses in the nucleus

BACKGROUND

In the present study the physical targeting technique photochemical internalization (PCI) has been used in combination with adenovirus. We have previously shown that PCI enhances transgene expression from AdhCMV-lacZ, and the aim of the present study was to further increase the understanding of photochemically mediated adenoviral transduction.

METHODS

Two colorectal carcinoma cell lines, WiDr and HCT116, were pre-incubated with the photosensitizer TPPS(2a) or methylene blue derivates (MBD) followed by infection with adenovirus and light exposure. Transgene expression was measured by flow cytometry. Real-time polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) were used to quantify the level of viral DNA in the nuclei. Real-time PCR was also used to measure the level of beta-galactosidase mRNA in samples infected with AdhCMV-lacZ.

RESULTS

Exposing TPPS(2a)-treated cells to light enhanced the quantity of viral DNA in the nucleus, the mRNA level of the transgene and the transgene expression compared to non-illuminated cells. The increased transgene expression was independent of the promoter used, but dependent on the time of light exposure and the cellular localization of the photosensitizer.

CONCLUSIONS

The enhanced transgene expression observed after photochemical treatment is most likely not a result of one event, but more an interplay between various mechanisms. An increased level of adenoviral DNA in the nucleus and a dependency of endosomal localization of the photosensitizer to obtain enhanced transgene expression suggested that endosomal rupture facilitated the transport of adenoviruses to the nucleus.

Photochemically enhanced adenoviral transduction in a multicellular environment

Photochemical internalization (PCI) enhances adenovirus (Ad) transgene expression in a variety of cell lines in vitro. However, measurements of the photochemical effect on transduction in multicellular environments are lacking. In this study, spheroids of DU 145 prostate cancer cells were used as a model to evaluate Ad serotype 5 (Ad5) transduction in a multicellular environment in response to PCI treatment. Furthermore, the Ad5 was coated with poly(2-methyl-acrylic acid 2-[(2-(dimethylamino)-ethyl)-methyl-amino]-ethyl ester) (pDAMA) to evaluate whether physicochemical properties such as charge and size of viral vectors affect transduction of photochemically treated spheroids. Spheroids incubated with photosensitizer TPPS(2a) (1 microg ml(-1)) and infected with adenovirus contained 3-fold higher percentage of reporter gene expressing cells after exposure to blue light (0.42 J cm(-2)) compared to no light, as analysed by flow cytometry of dissociated spheroids two days after treatment. The cells within the infected spheroids were further divided into three sections corresponding to the interior, intermediate and peripheral layers of the spheroids. This was performed by staining the spheroids with a diffusion-limited dye prior to dissociation. Transduction of cells within photochemically treated and untreated spheroids was heterogeneous, with a radial reduction of transgene expression towards the inner section of the spheroid. The coating of Ad with pDAMA induced up to 2-fold decrease in transduction of cells in the interior section of spheroids compared to uncomplexed Ad, while transduction of the peripheral section remained unchanged. The decrease in transduction could be related to reduced diffusion due to the size of the Ad-pDAMA complexes.

Variable expression of coxsackie-adenovirus receptor in thyroid tumors: implications for adenoviral gene therapy

Adenoviral gene therapy represents a novel approach for the treatment of aggressive thyroid carcinomas. Both coxsackie-adenovirus receptor (CAR) and integrins have been shown to be the major determinants for adenoviral infectivity in many types of cancer cells, yet conflicting results have been reported. In this report we examine these factors mediating adenoviral infection in thyroid cells and to evaluate CAR expression in various types of thyroid cancer. We found that neither expression levels of CAR nor integrins are solely predictive of adenoviral infectivity in thyroid cells. However, the absence of CAR was associated with poor adenoviral infectivity in immortalized rat FRTL-5 cells. Moreover, preincubation with alpha-CAR antibody decreased infectivity in FTC 238 cells, a human thyroid tumor line. These results indicate that CAR does play a role in adenoviral infection of thyroid cells. Immunohistochemical analysis revealed that CAR is expressed at the cell surface in the majority of malignant thyroid tumors. We further show that adenoviral infectivity in some thyroid cancer cells can be improved by poly-L-lysine. Our study warrants a functional method to evaluate adenoviral infectivity should be developed and instituted prior to clinical trials of adenoviral gene therapy in patients with advanced thyroid cancer.

PCI-enhanced adenoviral transduction employs the known uptake mechanism of adenoviral particles

The development of methods for efficient and specific delivery of therapeutic genes into target tissues is an important issue for further development of in vivo gene therapy. In the present study, the physical targeting technique, photochemical internalization (PCI), has been used together with adenovirus. The combination of PCI and adenoviral transduction has previously been shown to be favorable compared to adenovirus used alone, and the aim of this study was to verify the role of the adenoviral receptors and identify the uptake pathway used by adenoviral particles in photochemically treated cells. All examined cell lines showed augmented transduction efficiency after PCI-treatment, with a maximum of 13-fold increase in transgene expression compared to conventionally infected cells. Blocking of CAR induced a complete inhibition of PCI-enhanced transgene expression. However, photochemical treatment managed to enhance the transduction efficiency of the retargeted virus AdRGD-GFP showing also that the virus-CAR interaction is not vital for obtaining a photochemical effect on adenoviral transduction. Blocking the alpha(V)-integrins reduced the gene expression significantly in photochemically treated cells. Subjecting HeLa cells expressing negative mutant-dynamin to light treatment after infection gave no significant increase in gene transfer, while the gene transfer were enhanced seven-fold in cells with wild-type dynamin. Furthermore, chlorpromazine inhibited photochemical transduction in a dose-dependent manner, whereas Filipin III had no effect on the gene transfer. In summary, the data presented imply that adenoviral receptor binding is important and clathrin-mediated endocytosis is the predominant uptake mechanism for adenoviral particles in photochemically treated cells.

Porphyrin-related photosensitizers for cancer imaging and therapeutic applications

A photosensitizer is defined as a chemical entity, which upon absorption of light induces a chemical or physical alteration of another chemical entity. Some photosensitizers are utilized therapeutically such as in photodynamic therapy (PDT) and for diagnosis of cancer (fluorescence diagnosis, FD). PDT is approved for several cancer indications and FD has recently been approved for diagnosis of bladder cancer. The photosensitizers used are in most cases based on the porphyrin structure. These photosensitizers generally accumulate in cancer tissues to a higher extent than in the surrounding tissues and their fluorescing properties may be utilized for cancer detection. The photosensitizers may be chemically synthesized or induced endogenously by an intermediate in heme synthesis, 5-aminolevulinic acid (5-ALA) or 5-ALA esters. The therapeutic effect is based on the formation of reactive oxygen species (ROS) upon activation of the photosensitizer by light. Singlet oxygen is assumed to be the most important ROS for the therapeutic outcome. The fluorescing properties of the photosensitizers can be used to evaluate their intracellular localization and treatment effects. Some photosensitizers localize intracellularly in endocytic vesicles and upon light exposure induce a release of the contents of these vesicles, including externally added macromolecules, into the cytosol. This is the basis for a novel method for macromolecule activation, named photochemical internalization (PCI). PCI has been shown to potentiate the biological activity of a large variety of macromolecules and other molecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins, immunotoxins, gene-encoding plasmids, adenovirus, peptide-nucleic acids and the chemotherapeutic drug bleomycin. The background and present status of PDT, FD and PCI are reviewed.

Effect of polyethylenimine on recombinant adeno-associated virus mediated insulin gene therapy

BACKGROUND

Recombinant adeno-associated virus (rAAV) is becoming a promising vector for gene therapy for type I diabetes. The objective of this study was to investigate the effect of incorporation of polyethylenimine (PEI) on rAAV-mediated insulin gene therapy in vitro and in vivo.

METHODS

Recombinant AAV vector, harboring the furin-mutated human insulin and enhanced green fluorescent protein (EGFP) genes, was constructed. The effect of complexation with PEI on rAAV-mediated gene transfer was examined in Huh7 human hepatoma cells. The transgene expression was also examined in streptozotocin (STZ)-induced diabetic C57BL/6J mice by direct administration of rAAV into the livers of the animals, followed by monitoring changes in body weight and blood glucose levels. Secretion of human insulin was determined by radioimmunoassay (RIA) and immunohistochemical staining in the livers.

RESULTS

Complexation with PEI was shown to enhance rAAV-mediated transgene expression in Huh7 cells, resulting in higher transduction efficiency and enhanced production of immunoreactive human insulin. Heparin competition assay demonstrated that endocytosis of rAAV-PEI was partially inhibited by heparin. The enhancement of rAAV-mediated transgene expression was also demonstrated in the animals, showing lowering of blood glucose and longer duration of normoglycemia. Immunofluorescent staining of the liver sections demonstrated that PEI increased the uptake of rAAV and enhanced insulin secretion. The enhancement of PEI on rAAV-mediated insulin gene therapy was further confirmed by glucose challenge and a 10-h fasting blood glucose test.

CONCLUSIONS

Results obtained in this study demonstrated that incorporation of PEI augmented rAAV-mediated insulin gene transfer and enhanced amelioration of hyperglycemia in the STZ-induced diabetic animals.