Apoptin Gene Delivery by the Functionalized Polyamidoamine Dendrimer Derivatives Induces Cell Death of U87-MG Glioblastoma Cells

Angiopep-2 Grafted PAMAM Dendrimers for the Targeted Delivery of Temozolomide: In Vitro and In Vivo Effects of PEGylation in the Management of Glioblastoma Multiforme

The present study was aimed to synthesize, characterize, and evaluate the angiopep-2 grafted PAMAM dendrimers (Den, G 3.0 NH₂) with and without PEGylation for the targeted and better delivery approach of temozolomide (TMZ) for the management of glioblastoma multiforme (GBM). Den-ANG and Den-PEG₂-ANG conjugates were synthesized and characterized by ¹H NMR spectroscopy. The PEGylated (TMZ@Den-PEG₂-ANG) and non-PEGylated (TMZ@Den-ANG) drug loaded formulations were prepared and characterized for particle size, zeta potential, entrapment efficiency, and drug loading. An in vitro release study at physiological (pH 7.4) and acidic pH (pH 5.0) was performed. Preliminary toxicity studies were performed through hemolytic assay in human RBCs. MTT assay, cell uptake, and cell cycle analysis were performed to evaluate the in vitro efficacy against GBM cell lines (U87MG). Finally, the formulations were evaluated in vivo in a Sprague-Dawley rat model for pharmacokinetics and organ distribution analysis. The ¹H NMR spectra confirmed the conjugation of angiopep-2 to both PAMAM and PEGylated PAMAM dendrimers, as the characteristic chemical shifts were observed in the range of 2.1 to 3.9 ppm. AFM results revealed that the surface of Den-ANG and Den-PEG₂-ANG conjugates were rough. The particle size and zeta potential of TMZ@Den-ANG were observed to be 229.0 ± 17.8 nm and 9.06 ± 0.4 mV, respectively, whereas the same for TMZ@Den-PEG₂-ANG were found to be 249.6 ± 12.9 nm and 10.9 ± 0.6 mV, respectively. The entrapment efficiency of TMZ@Den-ANG and TMZ@Den-PEG₂-ANG were calculated to be 63.27 ± 5.1% and 71.48 ± 4.3%, respectively. Moreover, TMZ@Den-PEG₂-ANG showed a better drug release profile with a controlled and sustained pattern at PBS pH 5.0 than at pH 7.4. The ex vivo hemolytic study revealed that TMZ@Den-PEG₂-ANG was biocompatible in nature as it showed 2.78 ± 0.1% hemolysis compared to 4.12 ± 0.2% hemolysis displayed by TMZ@Den-ANG. The outcomes of the MTT assay inferred that TMZ@Den-PEG₂-ANG possessed maximum cytotoxic effects against U87MG cells with IC₅₀ values of 106.62 ± 11.43 μM (24 h) and 85.90 ± 9.12 μM (48 h). In the case of TMZ@Den-PEG₂-ANG, the IC₅₀ values were reduced by 2.23-fold (24 h) and 1.36-fold (48 h) in comparison to pure TMZ. The cytotoxicity findings were further confirmed by significantly higher cellular uptake of TMZ@Den-PEG₂-ANG. Cell cycle analysis of the formulations suggested that the PEGylated formulation halts the cell cycle at G2/M phase with S-phase inhibition. In the in vivo studies, the half-life (t_1/2) values of TMZ@Den-ANG and TMZ@Den-PEG₂-ANG were enhanced by 2.22 and 2.76 times, respectively, than the pure TMZ. After 4 h of administration, the brain uptake values of TMZ@Den-ANG and TMZ@Den-PEG₂-ANG were found to be 2.55 and 3.35 times, respectively, higher than that of pure TMZ. The outcomes of various in vitro and ex vivo experiments promoted the use of PEGylated nanocarriers for the management of GBM. Angiopep-2 grafted PEGylated PAMAM dendrimers can be potential and promising drug carriers for the targeted delivery of antiglioma drugs directly to the brain.

Functionalized PAMAM constructed nanosystems for biomacromolecule delivery

Polyamidoamines (PAMAMs) are a class of dendrimer with monodispersity and controlled topology, which can deliver biologically active macromolecules (e.g., genes and proteins) to specific regions with high efficiency and minimum side effects. In detail, PAMAMs can be functionalized easily by core modification or surface amendment to encapsulate a wide range of biomacromolecules. Besides, self-assembled, cross-linked and hybrid PAMAMs with customized therapeutic purposes are developed as delivery vehicles, which makes PAMAMs promising for biomacromolecule therapy. In this review, we comprehensively summarize the application of PAMAMs in biomacromolecule delivery from the synthesis of functionalized PAMAM carriers to the development of PAMAM-based drug delivery systems. The underlying strategies for PAMAM functionalization and assembly are first systematically discussed, and then the current applications of PAMAMs for biomacromolecule delivery are reviewed. Finally, a brief perspective on the further applications of PAMAMs concludes, aiming to provide insights into developing PAMAM-based biomacromolecule delivery systems.

A Review on Increasing the Targeting of PAMAM as Carriers in Glioma Therapy

Glioma is an invasive brain cancer, and it is difficult to achieve desired therapeutic effects due to the high postoperative recurrence rate and limited efficacy of drug therapy hindered by the biological barrier of brain tissue. Nanodrug delivery systems are of great interest, and many efforts have been made to utilize them for glioma treatment. Polyamidoamine (PAMAM), a starburst dendrimer, provides malleable molecular size, functionalized molecular structure and penetrable brain barrier characteristics. Therefore, PAMAM-based nanodrug delivery systems (PAMAM DDS) are preferred for glioma treatment research. In this review, experimental studies on PAMAM DDS for glioma therapy were focused on and summarized. Emphasis was given to three major topics: methods of drug loading, linkers between drug/ligand and PAMAM and ligands of modified PAMAM. A strategy for well-designed PAMAM DDS for glioma treatment was proposed. Purposefully understanding the physicochemical and structural characteristics of drugs is necessary for selecting drug loading methods and achieving high drug loading capacity. Additionally, functional ligands contribute to achieving the brain targeting, brain penetration and low toxicity of PAMAM DDS. Furthermore, a brilliant linker facilitates multidrug combination and multifunctional PAMAM DDS. PAMAM DDS show excellent promise as drug vehicles and will be further studied for product development and safety evaluation.

Surface Engineered Dendrimers: A Potential Nanocarrier for the Effective Management of Glioblastoma Multiforme

Gliomas are the most prevailing intracranial tumors, which account for approximately 36% of the primary brain tumors of glial cells. Glioblastoma multiforme (GBM) possesses a higher degree of malignancy among different gliomas. The blood-brain barrier (BBB) protects the brain against infections and toxic substances by preventing foreign molecules or unwanted cells from entering the brain parenchyma. Nano-carriers such as liposomes, nanoparticles, dendrimers, etc. boost the brain permeability of various anticancer drugs or other drugs. The favorable properties like small size, better solubility, and the modifiable surface of dendrimers have proven their broad applicability in the better management of GBM. However, in vitro and in vivo toxicities caused by dendrimers have been a significant concern. The presence of multiple functionalities on the surface of dendrimers enables the grafting of target ligand and/or therapeutic moieties. Surface engineering improves certain properties like targeting efficiency, pharmacokinetic profile, therapeutic effect, and toxicity reduction. This review will be focused on the role of different surface-modified dendrimers in the effective management of GBM.

Nanoparticle designs for delivery of nucleic acid therapeutics as brain cancer therapies

Glioblastoma (GBM) is an aggressive central nervous system cancer with a dismal prognosis. The standard of care involves surgical resection followed by radiotherapy and chemotherapy, but five-year survival is only 5.6% despite these measures. Novel therapeutic approaches, such as immunotherapies, targeted therapies, and gene therapies, have been explored to attempt to extend survival for patients. Nanoparticles have been receiving increasing attention as promising vehicles for non-viral nucleic acid delivery in the context of GBM, though delivery is often limited by low blood-brain barrier permeability, particle instability, and low trafficking to target brain structures and cells. In this review, nanoparticle design considerations and new advances to overcome nucleic acid delivery challenges to treat brain cancer are summarized and discussed.

The Effectiveness of Nanoparticles on Gene Therapy for Glioblastoma Cells Apoptosis: A Systematic Review

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and fatal type of glioma. Nanoparticles (NPs) are used in new approaches for the delivery of gene therapy in the treatment of GBM.

INTRODUCTION

The purpose of this article was to review the efficacy of NPs as the targeted carriers in the gene therapy aimed at apoptosis in GBM.

METHODS

The appropriate keywords such as nanoparticle, glioblastoma, gene therapy, apoptosis, and related words were used to search from PubMed, ISI Web of Science, and Scopus for relevant publications up to September 4, 2020, with no language restrictions. The present systematic review was performed based on PRISMA protocol and reviewed the articles evaluating the effects of nanoparticles, carriers of various gene therapies essentials, on GBM cells apoptosis in vitro and in vivo. The selected articles were considered using specific scores on the quality of the articles. Data extraction and quality evaluation were performed by two reviewers.

RESULTS

Of 101 articles retrieved, forty-two met the inclusion criteria and were, therefore, subjected to the final deduction. The most widely used NP in GBM gene therapy studies is polyamidoamine (PAMAM). The most common gene therapy approach for apoptosis in GBM is using siRNAs.

CONCLUSION

In conclusion, these studies validated that NPs could be a practical choice to enhance the efficiency and specific delivery in gene therapies for GBM cell apoptosis. However, the choice of NP type and gene therapy mechanism affect the GBM cell apoptotic efficiency.

Recent Advances in Preclinical Research Using PAMAM Dendrimers for Cancer Gene Therapy

Carriers of genetic material are divided into vectors of viral and non-viral origin. Viral carriers are already successfully used in experimental gene therapies, but despite advantages such as their high transfection efficiency and the wide knowledge of their practical potential, the remaining disadvantages, namely, their low capacity and complex manufacturing process, based on biological systems, are major limitations prior to their broad implementation in the clinical setting. The application of non-viral carriers in gene therapy is one of the available approaches. Poly(amidoamine) (PAMAM) dendrimers are repetitively branched, three-dimensional molecules, made of amide and amine subunits, possessing unique physiochemical properties. Surface and internal modifications improve their physicochemical properties, enabling the increase in cellular specificity and transfection efficiency and a reduction in cytotoxicity toward healthy cells. During the last 10 years of research on PAMAM dendrimers, three modification strategies have commonly been used: (1) surface modification with functional groups; (2) hybrid vector formation; (3) creation of supramolecular self-assemblies. This review describes and summarizes recent studies exploring the development of PAMAM dendrimers in anticancer gene therapies, evaluating the advantages and disadvantages of the modification approaches and the nanomedicine regulatory issues preventing their translation into the clinical setting, and highlighting important areas for further development and possible steps that seem promising in terms of development of PAMAM as a carrier of genetic material.

Nanoparticles in Combating Cancer: Opportunities and Limitations. A Brief Review

Nanomedicine is a good alternative to traditional methods of cancer treatment but does not solve all the limitations of oncology. Nanoparticles used in anticancer therapy can work as carriers of drugs, nucleic acids, imaging agents or they can sensitize cells to radiation. The present review focuses on the application of nanoparticles to treating cancer, as well as on its problems and limitations. Using nanoparticles as drug carriers, significant improvement in the efficiency of transport of compounds and their targeting directly to the tumour has been achieved; it also reduces the side effects of chemotherapeutic drugs on the body. However, nanoparticles do not significantly improve the effectiveness of the chemotherapeutic agent itself. Most nanodrugs can reduce the toxicity of chemotherapy, but do not significantly affect the effectiveness of treatment. Nanodrugs should be developed that can be effective as an anti-metastatic treatment, e.g. by enhancing the ability of nanoparticles to transport chemotherapeutic loads to sentinel lymph nodes using the immune system and developing chemotherapy in specific metastatic areas. Gene therapy, however, is the most modern method of treating cancer, the cause of cancer being tackled by altering genetic material. Other applications of nanoparticles for radiotherapy and diagnostics are discussed.

Apoptin as a Tumor-Specific Therapeutic Agent: Current Perspective on Mechanism of Action and Delivery Systems

Cancer remains one of the leading causes of death worldwide in humans and animals. Conventional treatment regimens often fail to produce the desired outcome due to disturbances in cell physiology that arise during the process of transformation. Additionally, development of treatment regimens with no or minimum side-effects is one of the thrust areas of modern cancer research. Oncolytic viral gene therapy employs certain viral genes which on ectopic expression find and selectively destroy malignant cells, thereby achieving tumor cell death without harming the normal cells in the neighborhood. Apoptin, encoded by Chicken Infectious Anemia Virus' VP3 gene, is a proline-rich protein capable of inducing apoptosis in cancer cells in a selective manner. In normal cells, the filamentous Apoptin becomes aggregated toward the cell margins, but is eventually degraded by proteasomes without harming the cells. In malignant cells, after activation by phosphorylation by a cancer cell-specific kinase whose identity is disputed, Apoptin accumulates in the nucleus, undergoes aggregation to form multimers, and prevents the dividing cancer cells from repairing their DNA lesions, thereby forcing them to undergo apoptosis. In this review, we discuss the present knowledge about the structure of Apoptin protein, elaborate on its mechanism of action, and summarize various strategies that have been used to deliver it as an anticancer drug in various cancer models.

Polyplexes for gene and nucleic acid delivery: Progress and bottlenecks

Gene and nucleic acid delivery constitute a huge biological challenge and several attempts have been made by research laboratories to address this issue. Cationic polymers and cationic lipids (positively charged carriers) can be utilized for the transport of these biomolecules. Polyplexes (PPs) are interpolyelectrolyte complexes which are spontaneously formed through the electrostatic condensation between nucleic acid and a cationic polymer. PPs are capable of high-density payload condensation leading to cell internalization and subsequent protection from enzymatic degradation. Most cationic polymers can cross extracellular barriers, but it is more challenging to overcome intracellular barriers (efficient disassembly and endosomal escape). In this review, the use of PPs for gene and nucleic acid delivery is discussed.

Generation Dependent Effects and Entrance to Mitochondria of Hybrid Dendrimers on Normal and Cancer Neuronal Cells In Vitro

Dendrimers as drug carriers can be utilized for drugs and siRNA delivery in central nervous system (CNS) disorders, including various types of cancers, such as neuroblastomas and gliomas. They have also been considered as drugs per se, for example as anti-Alzheimer's disease (AD), anti-cancer, anti-prion or anti-inflammatory agents. Since the influence of carbosilane-viologen-phosphorus dendrimers (SMT1 and SMT2) on the basic cellular processes of nerve cells had not been investigated, we examined the impact of two generations of these hybrid macromolecules on two murine cell lines-cancer cell line N2a (mouse neuroblastoma) and normal immortalized cell line mHippoE-18 (embryonic mouse hippocampal cell line). We examined alterations in cellular responses including the activity of mitochondrial dehydrogenases, the generation of reactive oxygen species (ROS), changes in mitochondrial membrane potential, and morphological modifications and fractions of apoptotic and dead cells. Our results show that both dendrimers at low concentrations affected the cancer cell line more than the normal one. Also, generation-dependent effects were found: the highest generation induced greater cytotoxic effects and morphological modifications. The most promising is that the changes in mitochondrial membrane potential and transmission electron microscopy (TEM) images indicate that dendrimer SMT1 can reach mitochondria. Thus, SMT1 and SMT2 seem to have potential as nanocarriers to mitochondria or anti-cancer drugs per se in CNS disorders.

Polymeric Nanoparticles in Gene Therapy: New Avenues of Design and Optimization for Delivery Applications

The field of polymeric nanoparticles is quickly expanding and playing a pivotal role in a wide spectrum of areas ranging from electronics, photonics, conducting materials, and sensors to medicine, pollution control, and environmental technology. Among the applications of polymers in medicine, gene therapy has emerged as one of the most advanced, with the capability to tackle disorders from the modern era. However, there are several barriers associated with the delivery of genes in the living system that need to be mitigated by polymer engineering. One of the most crucial challenges is the effectiveness of the delivery vehicle or vector. In last few decades, non-viral delivery systems have gained attention because of their low toxicity, potential for targeted delivery, long-term stability, lack of immunogenicity, and relatively low production cost. In 1987, Felgner et al. used the cationic lipid based non-viral gene delivery system for the very first time. This breakthrough opened the opportunity for other non-viral vectors, such as polymers. Cationic polymers have emerged as promising candidates for non-viral gene delivery systems because of their facile synthesis and flexible properties. These polymers can be conjugated with genetic material via electrostatic attraction at physiological pH, thereby facilitating gene delivery. Many factors influence the gene transfection efficiency of cationic polymers, including their structure, molecular weight, and surface charge. Outstanding representatives of polymers that have emerged over the last decade to be used in gene therapy are synthetic polymers such as poly(l-lysine), poly(l-ornithine), linear and branched polyethyleneimine, diethylaminoethyl-dextran, poly(amidoamine) dendrimers, and poly(dimethylaminoethyl methacrylate). Natural polymers, such as chitosan, dextran, gelatin, pullulan, and synthetic analogs, with sophisticated features like guanidinylated bio-reducible polymers were also explored. This review outlines the introduction of polymers in medicine, discusses the methods of polymer synthesis, addressing top down and bottom up techniques. Evaluation of functionalization strategies for therapeutic and formulation stability are also highlighted. The overview of the properties, challenges, and functionalization approaches and, finally, the applications of the polymeric delivery systems in gene therapy marks this review as a unique one-stop summary of developments in this field.

Antitumor effects of a recombinant baculovirus displaying anti-HER2 scFv expressing Apoptin in HER2 positive SK-BR-3 breast cancer cells

Aim: Since HER2 targeted therapies have shown clinical benefit in breast cancer, in the present study recombinant baculovirus (BV) displaying anti-HER2 single-chain variable domain fragment (scFv) expressing Apoptin was generated. Methods: The binding specificity and surface display of anti-HER2 scFv were evaluated using enzyme-linked immunosorbent assay (ELISA) and electron microscopy, respectively. The targeting properties and cytotoxic effect on breast cancer cells determined by fluorescence microscopy and MTT assays. Results: The results demonstrated that recombinant BV could specifically bind to HER2-overexpressing SK-BR-3 cells but not to the HER2 negative MCF-7 cells and reduced the viability of SK-BR-3 cells by expressing Apoptin. Conclusion: These results suggest that the antitumor effect of Apoptin in combination with HER2 targeting of this recombinant BV makes it a promising vector in targeted cancer therapy.

Polyplexes of Functional PAMAM Dendrimer/Apoptin Gene Induce Apoptosis of Human Primary Glioma Cells In Vitro

Highly efficient and safe gene delivery has become an important aspect of neuronal gene therapy. We evaluated the ability of polyamidoamine (PAMAM) dendrimer grafted with phenylalanine, histidine, and arginine (PAMAM-FHR), a nonviral gene delivery vector, to deliver a therapeutic, tumor cell-specific killer gene, apoptin, into the human primary glioma cell line GBL-14 and human dermal fibroblasts. We performed a transfection assay using plasmids of luciferase and enhanced green fluorescent protein (EGFP) and assessed cell viability. Both cell lines were treated with complexes of PAMAM-FHR and apoptin after which their intracellular uptake and localization were examined by fluorescence-activated cell sorting (FACS)analysis and confocal laser scanning microscopy. Confocal microscopy showed that the PAMAM-FHR escaped from the endo-lysosome into the cytosol. Cell cycle phase distribution analysis, annexin V staining, and a tetramethylrhodamine ethyl ester (TMRE) assay established that apoptin triggered apoptosis in the GBL-14 cell line but not in normal fibroblasts. These results indicated that the PAMAM-FHR/apoptin complex is an effective gene vehicle for cancer therapy in vitro.

Electrostatically assembled dendrimer complex with a high-affinity protein binder for targeted gene delivery

Although a variety of non-viral gene delivery systems have been developed, they still suffer from low efficiency and specificity. Herein, we present the assembly of a dendrimer complex comprising a DNA cargo and a targeting moiety as a new format for targeted gene delivery. A PAMAM dendrimer modified with histidine and arginine (HR-dendrimer) was used to enhance the endosomal escape and transfection efficiency. An EGFR-specific repebody, composed of leucine-rich repeat (LRR) modules, was employed as a targeting moiety. A polyanionic peptide was genetically fused to the repebody, followed by incubation with an HR-dendrimer and a DNA cargo to assemble the dendrimer complex through an electrostatic interaction. The resulting dendrimer complex was shown to deliver a DNA cargo with high efficiency in a receptor-specific manner. An analysis using a confocal microscope confirmed the internalization of the dendrimer complex and subsequent dissociation of a DNA cargo from the complex. The present approach can be broadly used in a targeted gene delivery in many areas.

rApoptin induces apoptosis in human breast cancer cells via phosphorylation of Nur77 and Akt

Breast cancer is the leading cause of cancer incidence and cancer-related mortality among women and is becoming a major public health problem around the world. The current study aims to investigate the possible role and mechanism of recombinant Apoptin (rApoptin), a potential anticancer candidate that minimally impacts normal cells, in the breast cancer cell proliferation and apoptosis in vitro and in vivo. We found that rApoptin could effectively inhibit the proliferation and apoptosis in MCF-7 and MDA-MB-231 cells in vitro, which was further confirmed by flow cytometry analysis. Apoptin partially inhibited MCF-7 cell xenograft tumor development in vivo. Furthermore, we found via western blot that rApoptin-induced apoptosis in MCF-7 and MDA-MB-231 cells was associated with the phosphorylation of Nur77 (p-Nur77) and Akt (p-Akt). In addition, compared with the control groups, rApoptin-treated tissues showed significantly higher expression of Bax and Cyt c while Bcl-2 expression was decreased by rApoptin treatment. Together, our results are the first to demonstrate that rApoptin was able to effectively induce breast cancer cell apoptosis both in vitro and in vivo and that this activity could be regulated by the phosphorylation of Nur77 and Akt and the mitochondrial pathway. Our findings highlight the potential application of rApoptin as a breast cancer treatment.

Legionella Pneumophila and Dendrimers-Mediated Antisense Therapy

Finding novel and effective antibiotics for treatment of Legionella disease is a challenging field. Treatment with antibiotics usually cures Legionella infection; however, if the resultant disease is not timely recognized and treated properly, it leads to poor prognosis and high case fatality rate. Legionella pneumophila DrrA protein (Defects in Rab1 recruitment protein A)/also known as SidM affects host cell vesicular trafficking through modification of the activity of cellular small guanosine triphosphatase )GTPase( Rab (Ras-related in brain) function which facilitates intracellular bacterial replication within a supporter vacuole. Also, Legionella pneumophila LepA and LepB (Legionella effector protein A and B) proteins suppress host-cell Rab1 protein's function resulting in the cell lysis and release of bacteria that subsequently infect neighbour cells. Legionella readily develops resistant to antibiotics and, therefore, new drugs with different modes of action and therapeutic strategic approaches are urgently required among antimicrobial drug therapies;gene therapy is a novel approach for Legionnaires disease treatment. On the contrary to the conventional treatment approaches that target bacterial proteins, new treatment interventions target DNA (Deoxyribonucleic acid), RNA (Ribonucleic acid) species, and different protein families or macromolecular complexes of these components. The above approaches can overcome the problems in therapy of Legionella infections caused by antibiotics resistance pathogens. Targeting Legionella genes involved in manipulating cellular vesicular trafficking using a dendrimer-mediated antisense therapy is a promising approach to inhibit bacterial replication within the target cells.