Differential role of αvβ3 and αvβ5 integrins in internalization and transduction efficacies of wild type and RGD4C fiber-modified adenoviruses

Targeted treatment of chondrosarcoma with a bacteriophage-based particle delivering a secreted tumor necrosis factor-related apoptosis-inducing ligand

Chondrosarcoma (CS) is a malignant cartilage-forming bone tumor that is inherently resistant to chemotherapy and radiotherapy, leaving surgery as the only treatment option. We have designed a tumor-targeted bacteriophage (phage)-derived particle (PDP), for targeted systemic delivery of cytokine-encoding transgenes to solid tumors. Phage has no intrinsic tropism for mammalian cells; therefore, it was engineered to display a double cyclic RGD4C ligand on the capsid to target tumors. To induce cancer cell death, we constructed a transgene cassette expressing a secreted form of the cytokine tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL). We detected high expression of αvβ3 and αvβ5 integrin receptors of the RGD4C ligand, and of the TRAIL receptor-2 in human CS cells (SW1353), but not in primary normal chondrocytes. The RGD4C.PDP-Luc particle carrying a luciferase reporter gene, Luc, effectively and selectively mediated gene delivery to SW1353 cells, but not primary chondrocytes. Transduction of SW1353 cells with RGD4C.PDP-sTRAIL encoding a human sTRAIL, resulted in the expression of TRAIL and subsequent cell death without harming the normal chondrocytes. Intravenous administration of RGD4C.PDP-sTRAIL to mice with established human CS resulted in a decrease in tumor size and tumor viability. Altogether, RGD4C.PDP-sTRAIL can be used to target systemic treatment of CS with the sTRAIL.

Human Adenovirus Type 26 Infection Mediated by αvβ3 Integrin Is Caveolin-1-Dependent

Human adenovirus type 26 (HAdV26) has been recognized as a promising platform for vaccine vector development, and very recently vaccine against COVID-19 based on HAdV26 was authorized for emergency use. Nevertheless, basic biology of this virus, namely, pathway which HAdV26 uses to enter the cell, is still insufficiently known. We have shown here that HAdV26 infection of human epithelial cells expressing low amount of αvβ3 integrin involves clathrin and is caveolin-1-independent, while HAdV26 infection of cells with high amount of αvβ3 integrin does not involve clathrin but is caveolin-1-dependent. Thus, this study demonstrates that caveolin-1 is limiting factor in αvβ3 integrin-mediated HAdV26 infection. Regardless of αvβ3 integrin expression, HAdV26 infection involves dynamin-2. Our data provide for the first-time description of HAdV26 cell entry pathway, hence increase our knowledge of HAdV26 infection. Knowing that functionality of adenovirus vector is influenced by its cell entry pathway and intracellular trafficking, our results will contribute to better understanding of HAdV26 immunogenicity and antigen presentation when used as vaccine vector.

IMPORTANCE In order to fulfill its role as a vector, adenovirus needs to successfully deliver its DNA genome to the host nucleus, a process highly influenced by adenovirus intracellular translocation. Thus, cell entry pathway and intracellular trafficking determine functionality of human adenovirus-based vectors. Endocytosis of HAdV26, currently extensively studied as a vaccine vector, has not been described so far. We present here that HAdV26 infection of human epithelial cells with high expression of αvβ3 integrin, one of the putative HAdV26 receptors, is caveolin-1- and partially dynamin-2-dependent. Since caveolin containing domains provide a unique environment for specific signaling events and participate in inflammatory signaling one can imagine that directing HAdV26 cell entry toward caveolin-1-mediate pathway might play role in immunogenicity of this virus. Therefore, our results contribute to better understanding of HAdV26 infection pathway, hence, can be helpful in explaining induction of immune response and antigen presentation by HAdV26-based vaccine vector.

The Revolving Door of Adenovirus Cell Entry: Not All Pathways Are Equal

Adenoviruses represent exceptional candidates for wide-ranging therapeutic applications, from vectors for gene therapy to oncolytics for cancer treatments. The first ever commercial gene therapy medicine was based on a recombinant adenovirus vector, while most recently, adenoviral vectors have proven critical as vaccine platforms in effectively controlling the global coronavirus pandemic. Here, we discuss factors involved in adenovirus cell binding, entry, and trafficking; how they influence efficiency of adenovirus-based vectors; and how they can be manipulated to enhance efficacy of genetically modified adenoviral variants. We focus particularly on endocytosis and how different adenovirus serotypes employ different endocytic pathways to gain cell entry, and thus, have different intracellular trafficking pathways that subsequently trigger different host antiviral responses. In the context of gene therapy, the final goal of the adenovirus vector is to efficiently deliver therapeutic transgenes into the target cell nucleus, thus allowing its functional expression. Aberrant or inefficient endocytosis can impede this goal, therefore, it should be considered when designing and constructing adenovirus-based vectors.

Bacteriophage-mediated therapy of chondrosarcoma by selective delivery of the tumor necrosis factor alpha (TNFα) gene

Chondrosarcoma is a cartilage-forming bone tumor, well known for intrinsic resistance to chemotherapy and radiotherapy. We have designed a targeted chondrosarcoma gene therapy using a bacteriophage (phage) particle to deliver therapeutic genes. Phage has no tropism for mammalian cells, allowing engineered phage to be targeted to specific cell surface receptors in cancer. We modified the phage capsid to display the RGD4C ligand on the pIII minor coat proteins to specifically bind to αvβ3 or αvβ5 integrin receptors. The endosomal escape peptide, H5WYG, was also displayed on recombinant pVIII major coat proteins to enhance gene delivery. Finally, a human tumor necrosis factor alpha (TNFα) therapeutic transgene expression cassette was incorporated into the phage genome. First, we found that human chondrosarcoma cells (SW1353) have high expression of αvβ3, αvβ5 integrin receptors, and both TNFα receptors. Targeted particle encoding a luciferase reporter gene efficiently and selectively mediated gene delivery to these cells. When SW1353 cells were treated with the targeted particle encoding a TNFα transgene, significant cell killing was evident and was associated with high expression of TNFα and apoptosis-related genes. In vivo, mice with established human chondrosarcoma showed suppression of tumors upon repetitive intravenous administrations of the targeted phage. These data show that our phage-based particle is a promising, selective, and efficient tool for targeted chondrosarcoma therapy.

A tropism-transformed Oncolytic Adenovirus with Dual Capsid Modifications for enhanced Glioblastoma Therapy

Glioblastoma, the most common human brain tumor, is highly invasive and difficult to cure using conventional cancer therapies. As an alternative, adenovirus-mediated virotherapies represent a popular and maturing technology. However, the cell surface coxsackievirus and adenovirus receptor (CAR)-dependent infection mechanism limits the infectivity and oncolytic effects of Adenovirus type 5. To address this limitation, in this study we aimed to develop a novel oncolytic adenovirus for enhanced infectivity and therapeutic efficacy toward glioblastoma. We developed a novel genetically modified oncolytic adenovirus vector with dual capsid modifications to facilitate infection and specific cytotoxicity toward glioma cells. Modification of the adenoviral capsid proteins involved the incorporation of a synthetic leucine zipper-like dimerization domain into the capsid protein IX (pIX) of human adenovirus serotype 5 (Ad5) and the exchange of the fiber knob from Ad37. The virus infection mechanism and anti-tumor efficacy of modified vectors were evaluated in both in vitro (cell) and in vivo (mouse) models. Ad37-knob exchange efficiently promoted the virus infection and replication-induced glioma cell lysis by oncolytic Ad5. We also found that gene therapy mediated by the dual-modified oncolytic Ad5 vector coupled with the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) exhibited significantly enhanced anti-tumor efficacy in vitro and in vivo. This genetically modified oncolytic adenovirus provides a promising vector for future use in glioblastoma gene-viral-based therapies.

Integrin Crosstalk Contributes to the Complexity of Signalling and Unpredictable Cancer Cell Fates

Integrins are heterodimeric cell surface receptors composed of α and β subunits that control adhesion, proliferation and gene expression. The integrin heterodimer binding to ligand reorganises the cytoskeletal networks and triggers multiple signalling pathways that can cause changes in cell cycle, proliferation, differentiation, survival and motility. In addition, integrins have been identified as targets for many different diseases, including cancer. Integrin crosstalk is a mechanism by which a change in the expression of a certain integrin subunit or the activation of an integrin heterodimer may interfere with the expression and/or activation of other integrin subunit(s) in the very same cell. Here, we review the evidence for integrin crosstalk in a range of cellular systems, with a particular emphasis on cancer. We describe the molecular mechanisms of integrin crosstalk, the effects of cell fate determination, and the contribution of crosstalk to therapeutic outcomes. Our intention is to raise awareness of integrin crosstalk events such that the contribution of the phenomenon can be taken into account when researching the biological or pathophysiological roles of integrins.

Capsid-Incorporation Strategy To Display Antigens for an Alternative Adenoviral Vector Vaccine Approach

The adenovirus (Ad) is widely used as a vaccine because of its ability to induce a cellular and humoral immune response. In addition, human clinical trials have validated the safety and efficacy of Ad as a vaccine vector. The traditional approach for employing the adenovirus as vaccine is to configure the antigen genes into the expression cassette of the Ad genome. An alternative method for inducing an immune response is the "capsid-incorporation" strategy. This strategy is based upon the incorporation of proteins or peptides into the capsid proteins. This review will focus on the established uses of this approach as well as highlighting the new developments regarding the capsid-incorporation strategy.

Tropism and transduction of oncolytic adenovirus 5 vectors in cancer therapy: Focus on fiber chimerism and mosaicism, hexon and pIX

The cellular internalization (infection of cells) of adenovirus 5 (Ad5) is mediated by the initial attachment of the globular knob domain of the capsid fiber protein to the cell surface coxsackievirus and adenovirus receptor (CAR), then followed by the interaction of the virus penton base proteins with cellular integrins. In tumors, there is a substantial intra- and intertumoral variability in CAR expression. The CAR-negative cells generally exhibit very low infectability. Since the fiber knob is a primary mediator of Ad5 binding to the cell surface, improved infectivity of Ad5-based vectors as oncolytic agents may be achieved via genetic modifications of this domain. The strategies to modify or broaden tropism and increase transduction efficiency of Ad5-based vectors include: 1) an incorporation of a targeting peptide into the fiber knob domain (the HI loop and/or C-terminus); 2) fiber knob serotype switching, or pseudotyping, by constructing chimeric fibers consisting of the knob domain derived from an alternate serotype (e.g., Ad5/3 or Ad5/35 chimeras), which binds to receptor(s) other than CAR (e.g., desmoglein 2/DSG2 and/or CD46); 3) "fiber complex mosaicism", an approach of combining serotype chimerism with peptide ligand(s) incorporation (e.g., Ad5/3-RGD); 4) "dual fiber mosaicism" by expressing two separate fibers with distinct receptor-binding capabilities on the same viral particle (e.g., Ad5-5/3 or Ad5-5/σ1); 5) fiber xenotyping by replacing the knob and shaft domains of wild-type Ad5 fiber protein with fibritin trimerization domain of T4 bacteriophage or σ1 attachment protein of reovirus. Other genetic approaches to increase the CAR-independent transduction efficiency include insertion of a targeting peptide into the hypervariable region of the capsid protein hexon or fusion to the C-terminus of pIX. Finally, we consider a yet unsolved molecular mechanism of liver targeting by Ad5-based vectors (CAR-, integrin-, fiber shaft KKTK motif-, and hepatic heparan sulfate glycosaminoglycans-independent, but fiber-, hexon- and blood factor X-dependent).

Quantum dot labelling of adenovirus allows highly sensitive single cell flow and imaging cytometry

A quantum dot method for highly efficient labelling of single adenoviral particles is developed. The technique has no impact on viral fitness and allows the imaging and tracking of virus binding and internalisation events using a variety of techniques including imaging cytometry and confocal microscopy. The method is applied to characterise the tropism of different adenoviral vectors.

Increased adenovirus Type 5 mediated transgene expression due to RhoB down-regulation

Adenovirus type 5 (Ad5) is a non-enveloped DNA virus frequently used as a gene transfer vector. Efficient Ad5 cell entry depends on the availability of its primary receptor, coxsackie and adenovirus receptor, which is responsible for attachment, and integrins, secondary receptors responsible for adenovirus internalization via clathrin-mediated endocytosis. However, efficacious adenovirus-mediated transgene expression also depends on successful trafficking of Ad5 particles to the nucleus of the target cell. It has been shown that changes occurring in tumor cells during development of resistance to anticancer drugs can be beneficial for adenovirus mediated transgene expression. In this study, using an in vitro model consisting of a parental cell line, human laryngeal carcinoma HEp2 cells, and a cisplatin-resistant clone CK2, we investigated the cause of increased Ad5-mediated transgene expression in CK2 as compared to HEp2 cells. We show that the primary cause of increased Ad5-mediated transgene expression in CK2 cells is not modulation of receptors on the cell surface or change in Ad5wt attachment and/or internalization, but is rather the consequence of decreased RhoB expression. We propose that RhoB plays an important role in Ad5 post-internalization events and more particularly in Ad5 intracellular trafficking. To the best of our knowledge, this is the first study showing changed Ad5 trafficking pattern between cells expressing different amount of RhoB, indicating the role of RhoB in Ad5 intracellular trafficking.

The disulfide bond of an RGD4C motif inserted within the Hi loop of the adenovirus type 5 fiber protein is critical for retargeting to αv -integrins

BACKGROUND

The α(v) -integrin binding motif RGD4C (CDCRGDCFC) has been used extensively to circumvent inefficient adenovirus type 5 (Ad5) transduction of cells expressing low levels of the coxsackie and adenovirus receptor. However, until now, it has been unclear whether disulfide bonds in the RGD4C motif influence the retargeting potential of RGD4C-modified Ad5.

METHODS

Replication deficient Ad5 bearing wild-type fiber (Ad5wt) or RGD4G, RGD4C and RGD2C2G insertions within the HI loop of the fiber protein (Ad5RGD4G, Ad5RGD4C and Ad5RGD2C2G, respectively) were used to transduce a panel of cancer cell lines, with or without previous treatment of these Ad5s with the reducing agent dithiothreitol (DTT). In parallel, native and DTT-treated fiber proteins isolated from purified Ad5RGD4C were compared by mass spectrometry.

RESULTS

Ad5RGD4C transduced all studied cell lines much more efficiently than Ad5wt, whereas Ad5RGD4G transduced cells only slightly more efficiently than Ad5wt. DTT treatment had no effect on cell transduction by wild-type Ad5wt and Ad5RGD4G but abolished the increased transduction efficacy of Ad5RGD4C in a dose-dependent manner. The mass spectra of native and DTT-reduced tryptic digests of the Ad5RGD4C fiber protein are consistent with the presence of a C(547) -C(549) linkage in the C(547) DC(549) RGDC(553) FC(555) motif. Finally, the high transduction efficacy of Ad5RGD4C is conserved in Ad5RGD2C2G.

CONCLUSIONS

We provide genetic and biochemical data strongly suggesting that cysteines C(547) and C(549) from the C(547) DC(549) RGDC(553) FC(555) motif inserted in the HI loop of the Ad5 fiber form a single disulfide bond, with this disulfide bond being crucial for Ad5RGD4C retargeting to av-integrins.

Adenovirus gene transfer to amelogenesis imperfecta ameloblast-like cells

To explore gene therapy strategies for amelogenesis imperfecta (AI), a human ameloblast-like cell population was established from third molars of an AI-affected patient. These cells were characterized by expression of cytokeratin 14, major enamel proteins and alkaline phosphatase staining. Suboptimal transduction of the ameloblast-like cells by an adenovirus type 5 (Ad5) vector was consistent with lower levels of the coxsackie-and-adenovirus receptor (CAR) on those cells relative to CAR-positive A549 cells. To overcome CAR -deficiency, we evaluated capsid-modified Ad5 vectors with various genetic capsid modifications including “pK7” and/or “RGD” motif-containing short peptides incorporated in the capsid protein fiber as well as fiber chimera with the Ad serotype 3 (Ad3) fiber “knob” domain. All fiber modifications provided an augmented transduction of AI-ameloblasts, revealed following vector dose normalization in A549 cells with a superior effect (up to 404-fold) of pK7/RGD double modification. This robust infectivity enhancement occurred through vector binding to both α_vβ3/α_vβ5 integrins and heparan sulfate proteoglycans (HSPGs) highly expressed by AI-ameloblasts as revealed by gene transfer blocking experiments. This work thus not only pioneers establishment of human AI ameloblast-like cell population as a model for in vitro studies but also reveals an optimal infectivity-enhancement strategy for a potential Ad5 vector-mediated gene therapy for AI.

Increased expression of the coxsackie and adenovirus receptor downregulates αvβ3 and αvβ5 integrin expression and reduces cell adhesion and migration

AIMS

Coxsackie and adenovirus receptor (CAR) is a tumor suppressor and a primary receptor for adenovirus type 5 (Ad5). Our study aims to examine the influence of forced expression of CAR in rhabdomyosarcoma cells (RD) on expression levels of integrins implicated in Ad5 entry, and the effect of CAR on cell-extracellular matrix adhesion and migration.

MAIN METHODS

CAR expressing clones were established from RD cells by stable transfection. Flow cytometry was used to evaluate the expression of CAR and integrins. Adhesion was measured in plates previously coated with vitronectin or fibronectin. Boyden chambers were used to investigate migration. Transfection of cells with siRNA was used to achieve integrin silencing. Ad5-mediated transgene expression was measured by β-gal staining.

KEY FINDINGS

Increased expression of CAR in RD cells reduces the expression of αvβ3 and αvβ5 integrins. Cells overexpressing CAR exhibit significantly reduced adhesion to vitronectin and fibronectin, and reduced cell migration. Specifically silencing αvβ3 integrin in RD cells reduced cell migration indicating that reduced migration could be the consequence of αvβ3 integrin downregulation. This study also demonstrates the negative effect of reduced levels of αvβ3 and αvβ5 integrins on Ad5-mediated transgene expression with Ad5 retargeted to αv integrins.

SIGNIFICANCE

The pharmacological upregulation of CAR aimed to increase Ad5-mediated transgene expression may actually downregulate αvβ3 and αvβ5 integrins and thus alter Ad5-mediated gene transfer. The mechanism of decreased cell migration, a prerequisite for metastasis and invasion, due to increased CAR expression may be explained by reduced αvβ3 integrin expression.

An adenovirus traffic update: from receptor engagement to the nuclear pore

Adenoviruses have a bipolar nature: they are ubiquitous pathogens that occasionally cause life-threatening diseases or they can be engineered into powerful gene transfer vectors. The goal of this article is to summarize the most recent advances in adenovirus receptor engagement, internalization, endosomal maturation, endosomal escape and trafficking to the nuclear pore. A better understanding of this initial part of the adenovirus lifecycle may identify new mechanistic-based treatments for adenovirus-induced diseases and help in the engineering of more efficient vectors.

Tumor-stroma interactions reduce the efficacy of adenoviral therapy through the HGF-MET pathway

Many preclinical studies have shown the potential of adenovirus-based cancer gene therapy. However, successful translation of these promising results into the clinic has not yet been achieved. Pancreatic ductal adenocarcinoma (PDAC) is characterized by abundant desmoplastic stroma, and tumor-stromal cell interactions play a critical role in tumor progression. Therefore, we hypothesized that tumor-stroma interactions reduce the efficacy of adenoviral therapy. We investigated the effect of fibroblasts on adenovirus-based gene therapy using SUIT-2 and PANC-1 pancreatic cancer cells cultured with or without fibroblast-conditioned culture supernatant then infected with Ad-LacZ. After 48 h, the cells were stained for β-galactosidase. The results showed that the number of β-galactosidase-positive cells was significantly reduced after culture with fibroblast-conditioned supernatant (P < 0.05). Because the hepatocyte growth factor (HGF)/MET pathway plays an important role in tumor-stroma interactions we next investigated the involvement of this pathway in tumor-stroma interactions leading to the decreased efficacy of adenoviral therapy. SUIT-2 cells were cultured with or without SU11274 (a MET inhibitor) and/or fibroblast-conditioned culture supernatant, then infected with Ad-GFP. After 48 h, GFP-positive cells were counted. The number of GFP-positive cells in cultures containing fibroblast-conditioned supernatant plus SU11274 was significantly greater than in cultures without SU11274. In conclusion, our results suggest that stromal cells in PDAC reduce the efficacy of adenoviral therapy through a mechanism involving the HGF/MET pathway. Control of such tumor-stroma interactions may lead to improvements in adenoviral gene therapy for PDAC.

Pancreatic cancer: gene therapy approaches and gene delivery systems

IMPORTANCE OF THE FIELD

Due to the absence of early diagnosis, the highly invasive and metastatic features and the lack of effective therapeutic modalities, the prognosis of patients with pancreatic cancer is poor. Gene therapy is currently regarded as a potential and promising therapeutic modality for pancreatic cancer.

AREAS COVERED IN THIS REVIEW

This article summarizes an update of gene therapy approaches and reviews the latest progress in gene delivery systems that have been tested on pancreatic cancer.

WHAT THE READER WILL GAIN

The treatment effectiveness of gene combination therapy is better than that of the regulation of single-gene or single gene therapy approaches. Naked DNA is limited because of degradation by intracellular and extracellular nucleases. Virus vectors show high transfection efficiency but are limited due to immunogenicity, inflammatory response and potential carcinogenicity. Non-viral vectors, such as cationic polymers or inorganic nanoparticles, show an important feature that they can be easily modified, and the progress of materials science will provide more and better non-viral vectors, accordingly improving the efficiency and safety of gene therapy, which will make them the most promising vectors for pancreatic cancer.

Up-regulation of integrin beta3 in radioresistant pancreatic cancer impairs adenovirus-mediated gene therapy

Adenovirus-mediated gene therapy is a promising approach for the treatment of pancreatic cancer. We previously reported that radiation enhanced adenovirus-mediated gene expression in pancreatic cancer, suggesting that adenoviral gene therapy might be more effective in radioresistant pancreatic cancer cells. In the present study, we compared the transduction efficiency of adenovirus-delivered genes in radiosensitive and radioresistant cells, and investigated the underlying mechanisms. We used an adenovirus expressing the hepatocyte growth factor antagonist, NK4 (Ad-NK4), as a representative gene therapy. We established two radioresistant human pancreatic cancer cell lines using fractionated irradiation. Radiosensitive and radioresistant pancreatic cancer cells were infected with Ad-NK4, and NK4 levels in the cells were measured. In order to investigate the mechanisms responsible for the differences in the transduction efficiency between these cells, we measured expression of the genes mediating adenovirus infection and endocytosis. The results revealed that NK4 levels in radioresistant cells were significantly lower (P < 0.01) than those in radiosensitive cells, although there were no significant differences in adenovirus uptake between radiosensitive cells and radioresistant cells. Integrin beta3 was up-regulated and the Coxsackie virus and adenovirus receptor was down-regulated in radioresistant cells, and inhibition of integrin beta3 promoted adenovirus gene transfer. These results suggest that inhibition of integrin beta3 in radioresistant pancreatic cancer cells could enhance adenovirus-mediated gene therapy.

Adenovirus receptors and their implications in gene delivery

Adenoviruses (Ads) have gained popularity as gene delivery vectors for therapeutic and prophylactic applications. Ad entry into host cells involves specific interactions between cell surface receptors and viral capsid proteins. Several cell surface molecules have been identified as receptors for Ad attachment and entry. Tissue tropism of Ad vectors is greatly influenced by their receptor usage. A variety of strategies have been investigated to modify Ad vector tropism by manipulating the receptor-interacting moieties. Many such strategies are aimed at targeting and/or detargeting of Ad vectors. In this review, we discuss the various cell surface molecules that are implicated as receptors for virus attachment and internalization. Special emphasis is given to Ad types that are utilized as gene delivery vectors. Various strategies to modify Ad tropism using the knowledge of Ad receptors are also discussed.