Current advances in adenovirus nanocomplexes: more specificity and less immunogenicity

Recent progress in tannic acid based approaches as a natural polyphenolic biomaterial for cancer therapy: A review

Significant advancements have been noticed in cancer therapy for decades. Despite this, there are still many critical challenges ahead, including multidrug resistance, drug instability, and side effects. To overcome obstacles of these problems, various types of materials in biomedical research have been explored. Chief among them, the applications of natural compounds have grown rapidly due to their superb biological activities. Natural compounds, especially polyphenolic compounds, play a positive and great role in cancer therapy. Tannic acid (TA), one of the most famous polyphenols, has attracted widespread attention in the field of cancer treatment with unique structural, physicochemical, pharmaceutical, anticancer, antiviral, antioxidant and other strong biological features. This review concentrated on the basic structure along with the important role of TA in tuning oncological signal pathways firstly, and then focused on the use of TA in chemotherapy and preparation of delivery systems including nanoparticles and hydrogels for cancer therapy. Besides, the application of TA/Fe3+ complex coating in photothermal therapy, chemodynamic therapy, combined therapy and theranostics is discussed.

Immunotherapy by mesenchymal stromal cell delivery of oncolytic viruses for treating metastatic tumors

Oncolytic viruses (OVs) have emerged as a very promising anti-cancer therapeutic strategy in the past decades. However, despite their pre-clinical promise, many OV clinical evaluations for cancer therapy have highlighted the continued need for their improved delivery and targeting. Mesenchymal stromal cells (MSCs) have emerged as excellent candidate vehicles for the delivery of OVs due to their tumor-homing properties and low immunogenicity. MSCs can enhance OV delivery by protecting viruses from rapid clearance following administration and also by more efficiently targeting tumor sites, consequently augmenting the therapeutic potential of OVs. MSCs can function as “biological factories,” enabling OV amplification within these cells to promote tumor lysis following MSC-OV arrival at the tumor site. MSC-OVs can promote enhanced safety profiles and therapeutic effects relative to OVs alone. In this review we explore the general characteristics of MSCs as delivery tools for cancer therapeutic agents. Furthermore, we discuss the potential of OVs as immune therapeutics and highlight some of the promising applications stemming from combining MSCs to achieve enhanced delivery and anti-tumor effectiveness of OVs at different pre-clinical and clinical stages. We further provide potential pitfalls of the MSC-OV platform and the strategies under development for enhancing the efficacy of these emerging therapeutics.

Development of a New Hyaluronic Acid Based Redox-Responsive Nanohydrogel for the Encapsulation of Oncolytic Viruses for Cancer Immunotherapy

Oncolytic viruses (OVs) are emerging as promising and potential anti-cancer therapeutic agents, not only able to kill cancer cells directly by selective intracellular viral replication, but also to promote an immune response against tumor. Unfortunately, the bioavailability under systemic administration of OVs is limited because of undesired inactivation caused by host immune system and neutralizing antibodies in the bloodstream. To address this issue, a novel hyaluronic acid based redox responsive nanohydrogel was developed in this study as delivery system for OVs, with the aim to protect the OVs following systemic administration. The nanohydrogel was formulated by water in oil (W/O) nanoemulsion method and cross-linked by disulfide bonds derived from the thiol groups of synthesized thiolated hyaluronic acid. One DNA OV Ad[I/PPT-E1A] and one RNA OV Rigvir^® ECHO-7 were encapsulated into the developed nanohydrogel, respectively, in view of their potential of immunovirotherapy to treat cancers. The nanohydrogels showed particle size of approximately 300–400 nm and negative zeta potential of around −13 mV by dynamic light scattering (DLS). A uniform spherical shape of the nanohydrogel was observed under the scanning electron microscope (SEM) and transmission electron microscope (TEM), especially, the successfully loading of OV into nanohydrogel was revealed by TEM. The crosslinking between the hyaluronic acid chains was confirmed by the appearance of new peak assigned to disulfide bond in Raman spectrum. Furthermore, the redox responsive ability of the nanohydrogel was determined by incubating the nanohydrogel into phosphate buffered saline (PBS) pH 7.4 with 10 μM or 10 mM glutathione at 37 °C which stimulate the normal physiological environment (extracellular) or reductive environment (intracellular or tumoral). The relative turbidity of the sample was real time monitored by DLS which indicated that the nanohydrogel could rapidly degrade within 10 h in the reductive environment due to the cleavage of disulfide bonds, while maintaining the stability in the normal physiological environment after 5 days. Additionally, in vitro cytotoxicity assays demonstrated a good oncolytic activity of OVs-loaded nanohydrogel against the specific cancer cell lines. Overall, the results indicated that the developed nanohydrogel is a delivery system appropriate for viral drugs, due to its hydrophilic and porous nature, and also thanks to its capacity to maintain the stability and activity of encapsulated viruses. Thus, nanohydrogel can be considered as a promising candidate carrier for systemic administration of oncolytic immunovirotherapy.

Oncolytic Adenovirus CD55-Smad4 Suppresses Cell Proliferation, Metastasis, and Tumor Stemness in Colorectal Cancer by Regulating Wnt/β-Catenin Signaling Pathway

During the past few decades, colorectal cancer (CRC) incidence and mortality have significantly increased, and CRC has become the leading cause of cancer-related death worldwide. Thus, exploring novel effective therapies for CRC is imperative. In this study, we investigated the effect of oncolytic adenovirus CD55-Smad4 on CRC cell growth. Cell viability assay, animal experiments, flow cytometric analysis, cell migration, and invasion assays, and Western blotting were used to detect the proliferation, apoptosis, migration, and invasion of CRC cells. The oncolytic adenovirus CD55-Smad4 was successfully constructed and effectively suppressed CRC cell proliferation in vivo and in vitro. Notably, CD55-Smad4 activated the caspase signaling pathway, inducing the apoptosis of CRC cells. Additionally, the generated oncolytic adenovirus significantly suppressed migration and invasion of CRC cells by overexpressing Smad4 and inhibiting Wnt/β-catenin/epithelial-mesenchymal transition (EMT) signaling pathway. Moreover, CRC cells treated with CD55-Smad4 formed less and smaller spheroid colonies in serum-free culture than cells in control groups, suggesting that CD55-Smad4 suppressed the stemness of CRC cells by inhibiting the Wnt/β-catenin pathway. Together, the results of this study provide valuable information for the development of a novel strategy for cancer-targeting gene-virotherapy and provide a deeper understanding of the critical significance of Smad4 in gene therapy of CRC.

Pectin-Tannic Acid Nano-Complexes Promote the Delivery and Bioactivity of Drugs in Pancreatic Cancer Cells

Pancreatic cancer (PanCa) is a lethal disease. Conventional chemotherapies for PanCa offer severe systemic toxicities. Thus, the development of a successful nanomedicine-based therapeutic regimen with augmented therapeutic efficacy is highly sought. Naturally occurring pectin and modified pectin-based drug delivery systems exhibit remarkable self-targeting ability via galactose residues to various cancer cells. Herein, we developed and used an innovative approach of highly stable nanocomplexes based on modified pectin and tannic acid (MPT-NCs). The nanocomplex formation was enabled by strong intermolecular interactions between pectin and tannic acid under very mild conditions. These nanocomplexes were characterized by particle size and morphology (DLS, TEM, and SEM), FT-IR spectroscopy, and zeta potential measurements. Additionally, MPT-NCs were capable of encapsulating anticancer drugs (5-fluorouracil, gemcitabine, and irinotecan) through tannic acid binding. The in vitro bioactivity of these drug MPT-NCs were evaluated in pancreatic cancer adenocarcinoma (PDAC) cell lines (HPAF-II and PANC-1). A dose-dependent internalization of nanocomplexes was evident from microscopy and flow cytometry analysis. Both proliferation and colony formation assays indicated the anticancer potential of pectin drug nanocomplexes against PDAC cells compared to that of free drug treatments. Together, the pectin-based nanocomplexes could be a reliable and efficient drug delivery strategy for cancer therapy.

Exploring the functions of polymers in adenovirus-mediated gene delivery: Evading immune response and redirecting tropism

Adenovirus (Ad) is a promising viral carrier in gene therapy because of its unique attribution. However, clinical applications of Ad vectors are currently restricted by their immunogenicity and broad native tropism. To address these obstacles, a variety of nonimmunogenic polymers are utilized to modify Ad vectors chemically or physically. In this review, we systemically discuss the functions of polymers in Ad-mediated gene delivery from two aspects: evading the host immune responses to Ads and redirecting Ad tropism. With polyethylene glycol (PEG) first in order, a variety of polymers have been developed to shield the surface of Ad vectors and well accomplished to evade the host immune response, block CAR-dependant cellular uptake, and reduce accumulation in the liver. In addition, shielding Ad vectors with targeted polymers (including targeting ligand-conjugated polymers and bio-responsive polymers) can also efficiently retarget Ad vectors to tumor tissues and reduce their distribution in nontargeted tissues. With its potential to evade the immune response and retarget Ad vectors, modification with polymers has been generally regarded as a promising strategy to facilitate the clinical applications of Ad vectors for virotherapy. STATEMENT OF SIGNIFICANCE: There is no doubt that Adenovirus (Ads) are attractive vectors for gene therapy, with high sophistication and effectiveness in overcoming both extra- and intracellular barriers, which cannot be exceeded by any other nonviral gene vectors. Unfortunately, their clinical applications are still restricted by some critical hurdles, including immunogenicity and native broad tropism. Therefore, a variety of elegant strategies have been developed from various angles to address these hurdles. Among these various strategies, coating Ads with nonimmunogenic polymers has attracted much attention. In this review, we systemically discuss the functions of polymers in Ad-mediated gene delivery from two aspects: evading the host immune responses to Ads and redirecting Ad tropism. In addition, the key factors in Ad modification with polymers have been highlighted and summarized to provide guiding theory for the design of more effective and safer polymer-Ad hybrid gene vectors.

Optimization and physicochemical characterization of a cationic lipid-phosphatidylcholine mixed emulsion formulated as a highly efficient vehicle that facilitates adenoviral gene transfer

Cationic lipid-based nanoparticles enhance viral gene transfer by forming electrostatic complexes with adenoviral vectors. We recently demonstrated the superior complexation capabilities of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) emulsion compared with a liposomal counterpart but the cytotoxicity of DOTAP emulsions remained a challenge. The present study is aimed at formulating an emulsion capable of acting as a highly effective viral gene transfer vehicle with reduced cytotoxicity and to physicochemically characterize the structures of virus-emulsion complexes in comparison with virus-liposome complexes when the only difference between emulsions and liposomes was the presence or absence of inner oil core. The emulsion formulation was performed by 1) reducing the content of DOTAP while increasing the content of zwitterionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 2) optimizing the oil content. The complexation capability of formulated DOTAP:DMPC mixed emulsions was similar to those of emulsions containing DOTAP alone while displaying significantly lower cytotoxicity. The complexation capabilities of the DOTAP:DMPC mixed emulsion were serum-compatible and were monitored in a variety of cell types, whereas its liposomal counterpart was totally ineffective. Characterization by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and dynamic light scattering studies indicated that the optimized emulsions spontaneously surrounded the virus particles to generate emulsions that encapsulated the viral particles, whereas viral particles merely attached to the surfaces of the counterpart liposomes to form multiviral aggregates. Overall, these studies demonstrated that optimized DOTAP:DMPC mixed emulsions are potentially useful for adenoviral gene delivery due to less cytotoxicity and the unique ability to encapsulate the viral particle, highlighting the importance of nanoparticle formulation.

Aminoclay as a highly effective cationic vehicle for enhancing adenovirus-mediated gene transfer through nanobiohybrid complex formation

Electrostatic complexation of adenovirus (Ad) with cationic lipids or polymers has been shown to be an effective means for overcoming the limitations of adenoviral vectors and enhancing gene-transfer efficacy. However, such complexation causes cytotoxicity, limiting the use of this strategy. The present study explored the potential of 3-aminopropyl functionalized magnesium phyllosilicate (aminoclay) as a cationic vehicle for improving Ad-mediated gene transfer without inducing cytotoxicity. Aminoclay complexation produced a dose-dependent increase in Ad-mediated transgene expression in both Ad infection-sensitive and -refractory cells, thereby greatly lowering the Ad dose required for transgene expression. Unlike the case for cationic lipids (Lipofectamine) or polymers (Polybrene), the enhancement effect of aminoclay was not accompanied by significant cytotoxicity regardless of cell lines and it was not observed for nonviral plasmid vectors. Physical characterization studies revealed that nanobiohybrid complexes formed between aminoclay and Ad particles through electrostatic interactions, creating aggregates of Ad particles whose surface was shielded with aminoclay nanosheet oligomers. It appears that aminoclay complexation changes the surface charge of Ad particles from a negative to a highly positive value and thus increases Ad binding to cellular membranes, thereby providing an additional cellular entry mechanism, namely caveolae-dependent endocytosis. Aminoclay-Ad nanobiohybrids may serve as a next-generation efficient, versatile and biocompatible gene-delivery carrier.

STATEMENT OF SIGNIFICANCE

Electrostatic complexation of adenovirus with cationic materials has been shown to be an effective means for enhancing gene-transfer efficacy in vitro. However, such complexation causes cytotoxicity, limiting the use of this strategy. The present study explored the potential of a synthesized organoclay 3-aminopropyl functionalized magnesium phyllosilicate (aminoclay) as a cationic vehicle for improving Ad-mediated gene transfer. Our data indicate that nanobiohybrid complexes form between aminoclay and Ad particles through electrostatic interactions, thereby greatly enhancing Ad-mediated gene transfer. Unlike the case for either cationic lipids or cationic polymers, the enhancement effect of aminoclay was not accompanied by significant cytotoxicity regardless of cell lines. Our findings in this work highlight that aminoclay-Ad nanobiohybrids may serve as a next-generation efficient and biocompatible gene-delivery carrier.

Evolving lessons on nanomaterial-coated viral vectors for local and systemic gene therapy

Viral vectors are promising gene carriers for cancer therapy. However, virus-mediated gene therapies have demonstrated insufficient therapeutic efficacy in clinical trials due to rapid dissemination to nontarget tissues and to the immunogenicity of viral vectors, resulting in poor retention at the disease locus and induction of adverse inflammatory responses in patients. Further, the limited tropism of viral vectors prevents efficient gene delivery to target tissues. In this regard, modification of the viral surface with nanomaterials is a promising strategy to augment vector accumulation at the target tissue, circumvent the host immune response, and avoid nonspecific interactions with the reticuloendothelial system or serum complement. In the present review, we discuss various chemical modification strategies to enhance the therapeutic efficacy of viral vectors delivered either locally or systemically. We conclude by highlighting the salient features of various nanomaterial-coated viral vectors and their prospects and directions for future research.

Antitumor effect and safety profile of systemically delivered oncolytic adenovirus complexed with EGFR-targeted PAMAM-based dendrimer in orthotopic lung tumor model

Adenovirus (Ad)-mediated cancer gene therapy has been proposed as a promising alternative to conventional therapy for cancer. However, success of systemically administered naked Ad has been limited due to the immunogenicity of Ad and the induction of hepatotoxicity caused by Ad's native tropism. In this study, we synthesized an epidermal growth factor receptor (EGFR)-specific therapeutic antibody (ErbB)-conjugated and PEGylated poly(amidoamine) (PAMAM) dendrimer (PPE) for complexation with Ad. Transduction of Ad was inhibited by complexation with PEGylated PAMAM (PP) dendrimer due to steric hindrance. However, PPE-complexed Ad selectively internalized into EGFR-positive cells with greater efficacy than either naked Ad or Ad complexed with PP. Systemically administered PPE-complexed oncolytic Ad elicited significantly reduced immunogenicity, nonspecific liver sequestration, and hepatotoxicity than naked Ad. Furthermore, PPE-complexed oncolytic Ad demonstrated prolonged blood retention time, enhanced intratumoral accumulation of Ad, and potent therapeutic efficacy in EGFR-positive orthotopic lung tumors in comparison with naked Ad. We conclude that ErbB-conjugated and PEGylated PAMAM dendrimer can efficiently mask Ad's capsid and retarget oncolytic Ad to be efficiently internalized into EGFR-positive tumor while attenuating toxicity induced by systemic administration of naked oncolytic Ad.

Enhanced anti-tumor efficacy and safety profile of tumor microenvironment-responsive oncolytic adenovirus nanocomplex by systemic administration

Oncolytic adenovirus (Ad) holds great promise as a potential gene therapy for cancer. However, intravenously administered Ad may encounter difficulties due to unfavorable host responses, non-specific interactions, and the heterogeneity of the tumor cell population. As an approach to combine the advantages of oncolytic Ad and synthetic polymers and to address the associated difficulties, Ad was physically complexed with a pH-sensitive block copolymer, methoxy poly(ethylene glycol)-b-poly(l-histidine) (mPEG-b-pHis). The in vitro transduction efficiency at an acidic extracellular pH was remarkably enhanced in cancer cells when treated with the Ad expressing green fluorescent protein (GFP) coated with mPEG-b-pHis (c-dE1/GFP) as compared to that of naked Ad (n-dE1/GFP). Time-lapse total internal reflection fluorescence microscopic imaging revealed a significantly enhanced cellular uptake rate of c-dE1/GFP at acidic tumor pH when compared with that at neutral pH or naked cognate Ad (n-dE1/GFP). In addition, c-dE1/GFP remained relatively stable in human serum-containing media, and considerably reduced both the innate and adaptive immune response against Ad. Moreover, the therapeutic efficacy and survival benefit of mPEG-b-pHis-complexed oncolytic Ad (c-H5mT/Luc) by systemic treatment was significantly enhanced compared to that with naked oncolytic Ad (n-H5mT/Luc) in both coxsackie and adenovirus receptor-positive and -negative tumors. Whole-body bioluminescence imaging showed 7.3-fold higher luciferase expression at the tumor site and 23.0-fold less luciferase expression in liver tissue for c-H5mT/Luc relative to that for naked oncolytic Ad (n-H5mT/Luc). Considering the heterogeneity of tumor tissue, these results are important for guiding the development of more potent and specific treatment of devastating metastatic cancers using this viral system.

STATEMENT OF SIGNIFICANCE

Although adenoviral systems have shown considerable promise and undergone extensive evaluation attempts to specifically target Ad vectors to cancer cells have met limited success. This shortcoming is due to the strong immune response stimulated by Ad and the hepatotoxicity of the viral particles. To overcome restricted vector issues, we generated Ad/mPEG-b-pHis for tumor microenvironment-targeting hybrid vector systems, an oncolytic Ad coated with a pH-responsive polymer, mPEG-b-pHis. The Ad/mPEG-b-pHis exhibited pH-dependent transduction efficiency and cancer-cell killing effects. Moreover, systemic administration of oncolytic Ad/mPEG-b-pHis led to marked suppression of tumor growth and tumor-specific viral replication. Ad successfully avoided the innate and adaptive immune responses and liver accumulation with the help of mPEG-b-pHis on its surface.

Potent antitumor effect of neurotensin receptor-targeted oncolytic adenovirus co-expressing decorin and Wnt antagonist in an orthotopic pancreatic tumor model

Pancreatic cancer is highly aggressive, malignant, and notoriously difficult to cure using conventional cancer therapies. These conventional therapies have significant limitations due to excessive extracellular matrix (ECM) of pancreatic cancer and poor cancer specificity. The excess ECM prevents infiltration of drugs into the inner layer of the solid tumor. Therefore, novel treatment modalities that can specifically target the tumor and degrade the ECM are required for effective therapy. In the present study, we used ECM-degrading and Wnt signal-disrupting oncolytic adenovirus (oAd/DCN/LRP) to achieve a desirable therapeutic outcome against pancreatic cancer. In addition, to overcome the limitations in systemic delivery of oncolytic Ad (oAd) and to specifically target pancreatic cancer, neurotensin peptide (NT)-conjugated polyethylene glycol (PEG) was chemically crosslinked to the surface of Ad, generating a systemically injectable hybrid system, oAd/DCN/LRP-PEG-NT. We tested the targeting and therapeutic efficacy of oAd/DCN/LRP-PEG-NT toward neurotensin receptor 1 (NTR)-overexpressing pancreatic cancer cells, both in vitro and in vivo. The oAd/DCN/LRP-PEG-NT elicited increased NTR-selective cancer cell killing and transduction efficiency when compared with a cognate control lacking NT (oAd/DCN/LRP-PEG). Furthermore, systemic administration of oAd/DCN/LRP-PEG-NT significantly decreased induction of innate and adaptive immune responses against Ad, and blood retention time was markedly prolonged by PEGylation. Moreover, NTR-targeting oAd elicited greater in vivo tumor growth suppression when compared with naked oAd and 9.5 × 10(6)-fold increased tumor-to-liver ratio. This significantly enhanced antitumor effect of oAd/DCN/LRP-PEG-NT was mediated by active viral replication and viral spreading, which was facilitated by ECM degradation and inhibition of Wnt signaling-related factors (Wnt, β-catenin, and/or vimentin) in the tumor tissues. Taken together, these results demonstrate that oAd/DCN/LRP-PEG-NT has strong therapeutic potential for systemic treatment of NTR-overexpressing pancreatic cancer due to its NTR-targeting ability, enhanced therapeutic efficacy, and safety.

Dual tumor targeting with pH-sensitive and bioreducible polymer-complexed oncolytic adenovirus

Oncolytic adenoviruses (Ads) have shown great promise in cancer gene therapy but their efficacy has been compromised by potent immunological, biochemical, and specific tumor-targeting limitations. To take full advantage of the innate cancer-specific killing potency of oncolytic Ads but also exploit the subtleties of the tumor microenvironment, we have generated a pH-sensitive and bio-reducible polymer (PPCBA)-coated oncolytic Ad. Ad-PPCBA complexes showed higher cellular uptake at pH 6.0 than pH 7.4 in both high and low coxsackie and adenovirus receptor-(CAR)-expressing cells, thereby demonstrating Ad-PPCBA's ability to target the low pH hypoxic tumor microenvironment and overcome CAR dependence for target cell uptake. Endocytic mechanism studies indicated that Ad-PPCBA internalization is mediated by macropinocytosis instead of the CAR-dependent endocytic pathway that internalizes naked Ad. VEGF-specific shRNA-expressing oncolytic Ad complexed with PPCBA (RdB/shVEGF-PPCBA) elicited much more potent suppression of U87 human brain cancer cell VEGF gene expression in vitro, and human breast cancer MCF7 cell/Matrigel plug vascularization in a mouse model, when cancer cells had been previously infected at pH 6.0 versus pH 7.4. Moreover, intratumorally and intravenously injected RdB/shVEGF-PPCBA nanocomplexes elicited significantly higher therapeutic efficacy than naked virus in U87-tumor mouse xenograft models, reducing IL-6, ALT, and AST serum levels. These data demonstrated PPCBA's biocompatibility and capability to shield the Ad surface to prevent innate immune response against Ad after both intratumoral and systemic administration. Taken together, these results demonstrate that smart, tumor-specific, oncolytic Ad-PPCBA complexes can be exploited to treat both primary and metastatic tumors.

Antitumor effects of a dual cancer-specific oncolytic adenovirus on colorectal cancer in vitro and in vivo

The efficacy and specificity of treatment are major challenges for cancer gene therapy. Oncolytic virotherapy is an attractive drug delivery platform for cancer gene therapy. In the present study, the dual-specific antitumor oncolytic adenovirus, Ad-Apoptin-hTERT-E1a, was used to infect SW1116 human colorectal carcinoma (CRC) cell lines and CT26 mouse-CRC-cell bearing BALB/c mouse models for testing antitumor effects in vitro and in vivo. The in vitro assays revealed that infection with Ad-Apoptin-hTERT-E1a induced a significant cytotoxic effect on the CRC cell line, SW1116; however, the normal human cell line, GES, was only slightly inhibited by the recombinant adenovirus. Acridine orange and ethidium bromide staining and an annexin V assay indicated that infection of SW1116 cells with Ad-Apoptin-hTERT-E1a resulted in a significant induction of apoptosis. Furthermore, western blotting and flow cytometry revealed a decrease in the mitochondrial membrane potential (MMP), the release of cytochrome c and the activation of caspase 3, 6 and 7 in Ad-Apoptin-hTERT-E1a-infected SW1116 cells. In the animal models, Ad-Apoptin-hTERT-E1a was shown to significantly inhibit tumor growth and extend the survival times of the animals. Therefore, the experimental results indicated that Ad-Apoptin-hTERT-E1a has potential for application in tumor gene therapy.

Hybrid Nanomaterial Complexes for Advanced Phage-guided Gene Delivery

Developing nanomaterials that are effective, safe, and selective for gene transfer applications is challenging. Bacteriophages (phage), viruses that infect bacteria only, have shown promise for targeted gene transfer applications. Unfortunately, limited progress has been achieved in improving their potential to overcome mammalian cellular barriers. We hypothesized that chemical modification of the bacteriophage capsid could be applied to improve targeted gene delivery by phage vectors into mammalian cells. Here, we introduce a novel hybrid system consisting of two classes of nanomaterial systems, cationic polymers and M13 bacteriophage virus particles genetically engineered to display a tumor-targeting ligand and carry a transgene cassette. We demonstrate that the phage complex with cationic polymers generates positively charged phage and large aggregates that show enhanced cell surface attachment, buffering capacity, and improved transgene expression while retaining cell type specificity. Moreover, phage/polymer complexes carrying a therapeutic gene achieve greater cancer cell killing than phage alone. This new class of hybrid nanomaterial platform can advance targeted gene delivery applications by bacteriophage.

Efficient lung orthotopic tumor-growth suppression of oncolytic adenovirus complexed with RGD-targeted bioreducible polymer

Oncolytic adenoviruses (Ad) have been developed for the eradication of tumors. Although they hold much promise as a cancer therapy, they have a short blood circulation time and high liver toxicity. An effective strategy to overcome these problems has been complexing Ad with shielding materials. However, the therapeutic efficacy of the Ad complexes has also been an issue because passive accumulation does not allow for sufficient delivery of Ad to the cancer cells. To enhance the therapeutic efficacy of the polymer-coated Ads, the attachment of a targeting moiety to polymer-coated Ad vectors is inescapable. Our lab has previously reported the potential use of Arg-Gly-Asp (RGD)-targeted bioreducible polymers with a polyethylene glycol (PEG) linker for delivering oncolytic Ads. We have shown the enhanced in vitro transduction efficiency and increased cancer-killing effect with producing progeny oncolytic Ad particles. In addition, we have shown significant tumor-growth inhibition of the polymer-shielded Ad in an in vivo lung orthotopic tumor model. The shielding effect of the Ad surface with the polymers allowed evasion of host immune responses and reduction of liver toxicity. This data demonstrates that the RGD-conjugated bioreducible polymer for delivering the oncolytic Ad vectors could be utilized for cancer therapy via systemic administration.

Utilizing adenovirus vectors for gene delivery in cancer

INTRODUCTION

Adenovirus (Ad) is a promising candidate vector for cancer gene therapy because of its unique characteristics, which include efficient infection, high loading capacity and lack of insertional mutagenesis. However, systemic administration of Ad is hampered by the host's immune response, hepatocytoxicity, short half-life of the vector and low accumulation at the target site. For these reasons, clinical applications of Ad are currently restricted.

AREAS COVERED

In this review, we focus on recent developments in Ad nanocomplex systems that improve the transduction and targeting efficacy of Ad vectors in cancer gene therapy. We discuss the development of different Ad delivery systems, including surface modification of Ad, smart Ad/nanohybrid systems and hydrogels for sustained release of Ad.

EXPERT OPINION

The fusion of bioengineering and biopharmaceutical technologies can provide solutions to the obstacles encountered during systemic delivery of Ads. The in vivo transgene expression efficiency of Ad nanocomplex systems is typically high, and animal tumor models demonstrate that systemic administration of these Ad complexes can arrest tumor growth. However, further optimization of these smart Ad nanocomplex systems is needed to increase their effectiveness and safety for clinical application in cancer gene therapy.

Enhanced antitumor immunotherapeutic effect of B-cell-based vaccine transduced with modified adenoviral vector containing type 35 fiber structures

For successful clinical tumor immunotherapy outcomes, strong immune responses against tumor antigens must be generated. Cell-based vaccines compromise one strategy with which to induce appropriate strong immune responses. Previously, we established a natural killer T-cell (NKT) ligand-loaded, adenoviral vector-transduced B-cell-based anticancer cellular vaccine. To enhance tumor antigen delivery to B cells, we established a modified adenoviral vector (Ad-k35) that encoded a truncated form of the breast cancer antigen Her2/neu (Ad-k35HM) in which fiber structure was substituted with adenovirus serotype 35. We observed increased tumor antigen expression with Ad-k35HM in both human and murine B cells. In addition, an Ad-k35HM-transduced B-cell vaccine elicited strong antigen-specific cellular and humoral immune responses that were further enhanced with the additional loading of soluble NKT ligand KBC009. An Ad-k35HM-transduced, KBC009-loaded B-cell vaccine efficiently suppressed the in vivo growth of established tumors in a mouse model. Moreover, the vaccine elicited human leukocyte antigen (HLA)-A2 epitope-specific cytotoxic T-cell responses in B6.Cg (CB)-Tg (HLA-A/H2-D) 2Enge/Jat mice. These findings indicated that the Ad-k35 could be appropriate for the preclinical and clinical development of B-cell-based anticancer immunotherapies.

Gene delivery via the hybrid vector of recombinant adeno-associated virus and polyethylenimine

The aim of this study was to investigate the cellular delivery mechanism of the hybrid vector comprising the recombinant adeno-associated virus (rAAV) and polyethylenimine (PEI). The rAAV vector, rAAV-rIns1-hInsM2-ΔEGFP, was fluorescently labeled with Cy3, a cyanine dye, and complexed with PEI. The interaction of the hybrid vector with the Huh7 hepatoma cells was monitored by confocal microscopy. Complexation of rAAV with PEI enhanced the transduction efficiency, which was decreased by pretreatment of the cells with sodium chlorate, an inhibitor of glycosaminoglycan sulfation, suggesting the roles of heparan sulfate proteoglycans (HSPG) in the uptake of the hybrid vector by the cells. Examination by flow cytometry and confocal microscopy demonstrated an enhanced interaction between the cells and the virus when complexed with PEI. Pretreatment with wortmannin or cytochalasin B significantly reduced the virus uptake by the cells, suggesting the involvement of phosphatidylinositol 3-kinase (PI3K) signaling and phagocytosis in the interaction between the cells and the hybrid vectors. Treatment of cells with the antioxidants, including l-ascorbic acid, δ-tocotrienol, or N-acetylcysteine (NAC), impaired the rAAV-PEI-mediated transduction. Results obtained in this study illustrated the involvement of PI3K/Akt signaling and the ROS production in gene delivery via the rAAV-PEI hybrid vector.

Systemic image-guided liver cancer radiovirotherapy using dendrimer-coated adenovirus encoding the sodium iodide symporter as theranostic gene

Currently, major limitations for the clinical application of adenovirus-mediated gene therapy are high prevalence of neutralizing antibodies, widespread expression of the coxsackie-adenovirus receptor (CAR), and adenovirus sequestration by the liver. In the current study, we used the sodium iodide symporter (NIS) as a theranostic gene to investigate whether coating of adenovirus with synthetic dendrimers could be useful to overcome these hurdles in order to develop adenoviral vectors for combination of systemic oncolytic virotherapy and NIS-mediated radiotherapy.

METHODS

We coated replication-deficient (Ad5-CMV/NIS) (CMV is cytomegalovirus) and replication-selective (Ad5-E1/AFP-E3/NIS) adenovirus serotype 5 carrying the hNIS gene with poly(amidoamine) dendrimers generation 5 (PAMAM-G5) in order to investigate transduction efficacy and altered tropism of these coated virus particles by (123)I scintigraphy and to evaluate their therapeutic potential for systemic radiovirotherapy in a liver cancer xenograft mouse model.

RESULTS

After dendrimer coating, Ad5-CMV/NIS demonstrated partial protection from neutralizing antibodies and enhanced transduction efficacy in CAR-negative cells in vitro. In vivo (123)I scintigraphy of nude mice revealed significantly reduced levels of hepatic transgene expression after intravenous injection of dendrimer-coated Ad5-CMV/NIS (dcAd5-CMV/NIS). Evasion from liver accumulation resulted in significantly reduced liver toxicity and increased transduction efficiency of dcAd5-CMV/NIS in hepatoma xenografts. After PAMAM-G5 coating of the replication-selective Ad5-E1/AFP-E3/NIS, a significantly enhanced oncolytic effect was observed after intravenous application (virotherapy) that was further increased by additional treatment with a therapeutic dose of (131)I (radiovirotherapy) and was associated with markedly improved survival.

CONCLUSION

These results demonstrate efficient liver detargeting and tumor retargeting of adenoviral vectors after coating with synthetic dendrimers, thereby representing a promising innovative strategy for systemic NIS gene therapy. Moreover, our study-based on the function of NIS as a theranostic gene allowing the noninvasive imaging of NIS expression by (123)I scintigraphy-provides detailed characterization of in vivo vector biodistribution and localization, level, and duration of transgene expression, essential prerequisites for exact planning and monitoring of clinical gene therapy trials that aim to individualize the NIS gene therapy concept.

Therapeutic efficacy of a systemically delivered oncolytic adenovirus - biodegradable polymer complex

Despite great efforts to develop a more effective oncolytic adenovirus (Ad) for eradicating tumors, in vivo application via systemic administration is strictly limited to local injection due to host immune responses by Ad surface proteins and liver accumulation by the inherent nature of the Ad. In the last decade, numerous techniques using synthetic polymers have widely emerged to shield the exterior of therapeutic Ad vectors for systemic delivery. We developed a cationic polymer linked with polyethylene glycol for systemically delivering oncolytic Ad. The increased transduction efficiency and oncolytic effect of the Ad vectors physically coated with the polymer were evaluated, showing the optimal size (130 nm) of the Ad/polymer complex for systemic administration and prolonged stability of the Ad/polymer complex. Marked tumor growth suppression of the oncolytic Ad delivered by the polymer through systemic injection was observed in HT1080 and A549 xenograft models. The masking effect of the Ad surface by the polymer elicited evasion of innate adaptive immune responses and the tumor-to-liver ratio of the complex was significantly elevated 1229-fold greater than that of a naked Ad. These results demonstrate that the potential system of oncolytic Ad complexed with the biodegradable polymer may be useful for developing therapeutic vector systems via systemic delivery.

Adeno-associated virus serotype 9 administered systemically after reperfusion preferentially targets cardiomyocytes in the infarct border zone with pharmacodynamics suitable for the attenuation of left ventricular remodeling

BACKGROUND

Adeno-associated virus serotype 9 (AAV9) vectors provide efficient and uniform gene expression to normal myocardium following systemic administration, with kinetics that approach steady-state within 2-3 weeks. However, as a result of the delayed onset of gene expression, AAV vectors have not previously been administered intravenously after reperfusion for post-infarct gene therapy applications. The present study evaluated the therapeutic potential of post-myocardial infarction gene delivery using intravenous AAV9.

METHODS

AAV9 vectors expressing firefly luciferase, enhanced green fluorescent protein (eGFP) or extracellular superoxide dismutase genes from the cardiac troponin-T (cTnT) promoter (AcTnTLuc, AcTnTeGFP, AcTnTEcSOD) were employed. AcTnTLuc was administered intravenously at 10 min and at 1, 2 and 3 days post-ischemia/reperfusion (IR), and the kinetics of luciferase expression were assessed with bioluminescence imaging. AcTnTeGFP was used to evaluate the distribution of eGFP expression. High-resolution echocardiography was used to evaluate the effects of AcTnTEcSOD on left ventricular (LV) remodeling when injected 10 min post-IR.

RESULTS

Compared to sham animals, luciferase expression at 2 days after vector administration was elevated by four-, 24-, 210- and 213-fold in groups injected at 10 min, 1 day, 2 days and 3 days post-IR, respectively. The expression of cTnT-driven eGFP was strongest in cardiomyocytes bordering the infarct zone. In the efficacy study of EcSOD, post-infarct LV end-systolic and end-diastolic volumes at days 14 and 28 were significantly smaller in the EcSOD group compared to the control.

CONCLUSIONS

Systemic administration of AAV9 vectors after IR both elevates and accelerates gene expression that preferentially targets cardiomyocytes in the border zone with pharmacodynamics suitable for the attenuation of LV remodeling.

Polymer-based delivery of glucagon-like Peptide-1 for the treatment of diabetes

The incretin hormones, glucagon-like peptide-1 (GLP-1) and its receptor agonist (exendin-4), are well known for glucose homeostasis, insulinotropic effect, and effects on weight loss and food intake. However, due to the rapid degradation of GLP-1 by dipeptidylpeptidase-IV (DPP-IV) enzyme and renal elimination of exendin-4, their clinical applications have been restricted. Although exendin-4 has longer half-life than GLP-1, it still requires frequent injections to maintain efficacy for the treatment of diabetes. In recent decades, various polymeric delivery systems have been developed for the delivery of GLP-1 and exendin-4 genes or peptides for their long-term action and the extra production in ectopic tissues. Herein, we discuss the modification of the expression cassettes and peptides for long-term production and secretion of the native peptides. In addition, the characteristics of nonviral or viral system used for a delivery of a modified GLP-1 or exendin-4 are described. Furthermore, recent efforts to improve the biological half-life of GLP-1 or exendin-4 peptide via chemical conjugation with various smart polymers via chemical conjugation compared with native peptide are discussed.

Linearized oncolytic adenoviral plasmid DNA delivered by bioreducible polymers

As an effort to overcome limits of adenovirus (Ad) as a systemic delivery vector for cancer therapy, we developed a novel system using oncolytic Ad plasmid DNA with two bioreducible polymers: arginine-grafted bioreducible poly(disulfide amine)polymer (ABP) and PEG5k-conjugated ABP (ABP5k) in expectation of oncolytic effect caused by progeny viral production followed by replication. The linearized Ad DNAs for active viral replication polyplexed with each polymer were able to replicate only in human cancer cells and produce progeny viruses. The non-immunogenic polymers delivering the DNAs markedly elicited to evade the innate and adaptive immune response. The biodistribution ratio of the polyplexes administered systemically was approximately 99% decreased in liver when compared with naked Ad. Moreover, tumor-to-liver ratio of the Ad DNA delivered by ABP or ABP5k was significantly elevated at 229- or 419-fold greater than that of naked Ad, respectively. The ABP5k improved the chance of the DNA to localize within tumor versus liver with 1.8-fold increased ratio. In conclusion, the innovative and simple system for delivering oncolytic Ad plasmid DNA with the bioreducible polymers, skipping time-consuming steps such as generation and characterization of oncolytic Ad vectors, can be utilized as an alternative approach for cancer therapy.

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.

Active targeting of RGD-conjugated bioreducible polymer for delivery of oncolytic adenovirus expressing shRNA against IL-8 mRNA

Even though oncolytic adenovirus (Ad) has been highlighted in the field of cancer gene therapy, transductional targeting and immune privilege still remain difficult challenges. The recent reports have noted the increasing tendency of adenoviral surface shielding with polymer to overcome the limits of its practical application. We previously reported the potential of the biodegradable polymer, poly(CBA-DAH) (CD) as a promising candidate for efficient gene delivery. To endow the selective-targeting moiety of tumor vasculature to CD, cRGDfC well-known as a ligand for cell-surface integrins on tumor endothelium was conjugated to CD using hetero-bifunctional cross-linker SM (PEG)(n). The cytopathic effects of oncolytic Ad coated with the polymers were much more enhanced dose-dependently when compared with that of naked Ad in cancer cells selectively. Above all, the most potent oncolytic effect was assessed with the treatment of Ad/CD-PEG(500)-RGD in all cancer cells. The enhanced cytopathic effect of Ad/RGD-conjugated polymer was specifically inhibited by blocking antibodies to integrins, but not by blocking antibody to CAR. HT1080 cells treated with Ad/CD-PEG(500)-RGD showed strong induction of apoptosis and suppression of IL-8 and VEGF expression as well. These results suggest that RGD-conjugated bioreducible polymer might be used to deliver oncolytic Ad safely and efficiently for tumor therapy.