Tumor regression following intravenous administration of a tumor-targeted p73 gene delivery system

Dendrimer-based delivery of macromolecules for the treatment of brain tumor

Brain tumor represents the most lethal form of cancer with the highest mortality and morbidity rates irrespective of age and sex. Advancements in macromolecule-based therapy (such as nucleic acids and peptides) have shown promising roles in the treatment of brain tumor where the phenomenon of severe toxicities due to the conventional chemotherapeutic agents can be circumvented. Despite its preclinical progress, successful targeting of these macromolecules across the blood-brain barrier without altering their physical and chemical characteristics is of great challenge. With the advent of nanotechnology, nowadays targeted delivery of therapeutics is being explored extensively and these macromolecules, including peptides and nucleic acids, have shown initial success in the treatment, where dendrimer has shown its potential for optimal delivery. Dendrimers are being favored as a mode of drug delivery due to their nano-spherical size and structure, high solubilization potential, multivalent surface, and high loading capacity, where biomolecule resembling characteristics of dendritic 3D structures has shown effective delivery of various therapeutic agents to the brain. Armed with targeting ligands to these dendrimers further expedite the transportation of these multifunctional shuttles specifically to the glioblastoma cells. Thus, a focus has been made in this review on therapeutic applications of dendrimer platforms in brain tumor treatment. The future development of dendrimers as a potential platform for nucleic acid and peptide delivery and its promising clinical application could provide effective and target-specific treatment against brain tumors.

Emergence of cationic polyamine dendrimersomes: design, stimuli sensitivity and potential biomedical applications

For decades, self-assembled lipid vesicles have been widely used in clinics as nanoscale delivery systems for various biomedical applications, including treatment of various diseases. Due to their core-shell architecture and versatile nature, they have been successfully used as carriers for the delivery of a wide range of therapeutic cargos, including drugs and nucleic acids, in cancer treatment. Recently, surface-modified polyamine dendrimer-based vesicles, or dendrimersomes, have emerged as promising alternatives to lipid vesicles for various biomedical applications, due to their ease of synthesis, non-immunogenicity, stability in circulation and lower size polydispersity. This mini-review provides an overview of the recent advances resulting from the use of biomimetic hydrophobically-modified polyamine-based dendrimersomes towards biomedical applications, focusing mainly on the two most widely used polyamine dendrimers, namely polyamidoamine (PAMAM) and poly(propylene imine) (PPI) dendrimers.

Dendrimers as Non-Viral Vectors in Gene-Directed Enzyme Prodrug Therapy

Gene-directed enzyme prodrug therapy (GDEPT) has been intensively studied as a promising new strategy of prodrug delivery, with its main advantages being represented by an enhanced efficacy and a reduced off-target toxicity of the active drug. In recent years, numerous therapeutic systems based on GDEPT strategy have entered clinical trials. In order to deliver the desired gene at a specific site of action, this therapeutic approach uses vectors divided in two major categories, viral vectors and non-viral vectors, with the latter being represented by chemical delivery agents. There is considerable interest in the development of non-viral vectors due to their decreased immunogenicity, higher specificity, ease of synthesis and greater flexibility for subsequent modulations. Dendrimers used as delivery vehicles offer many advantages, such as: nanoscale size, precise molecular weight, increased solubility, high load capacity, high bioavailability and low immunogenicity. The aim of the present work was to provide a comprehensive overview of the recent advances regarding the use of dendrimers as non-viral carriers in the GDEPT therapy.

Octadecyl chain-bearing PEGylated poly(propyleneimine)-based dendrimersomes: physicochemical studies, redox-responsiveness, DNA condensation, cytotoxicity and gene delivery to cancer cells

Stimuli-responsive nanocarriers have become increasingly important for nucleic acid and drug delivery in cancer therapy. Here, we report the synthesis, characterization and evaluation of disulphide-linked, octadecyl (C18 alkyl) chain-bearing PEGylated generation 3-diaminobutyric polypropylenimine dendrimer-based vesicles (or dendrimersomes) for gene delivery. The lipid-bearing PEGylated dendrimer was successfully synthesized through in situ two-step reaction. It was able to spontaneously self-assemble into stable, cationic, nanosized vesicles, with low critical aggregation concentration value, and also showed redox-responsiveness in presence of a glutathione concentration similar to that of the cytosolic reducing environment. In addition, it was able to condense more than 70% of DNA at dendrimer: DNA weight ratios of 5 : 1 and higher. This dendriplex resulted in an enhanced cellular uptake of DNA at dendrimer: DNA weight ratios of 10 : 1 and 20 : 1, by up to 16-fold and by up to 28-fold compared with naked DNA in PC-3 and DU145 prostate cancer cell lines respectively. At a dendrimer: DNA weight ratio of 20 : 1, it led to an increase in gene expression in PC-3 and DU145 cells, compared with DAB dendriplex. These octadecyl chain-bearing, PEGylated dendrimer-based vesicles are therefore promising redox-sensitive drug and gene delivery systems for potential applications in combination cancer therapy.

Camptothecin-based dendrimersomes for gene delivery and redox-responsive drug delivery to cancer cells

Combination therapy involving chemotherapeutic drugs and genes is emerging as a promising strategy to provide a synergistic therapeutic effect, to overcome drug resistance while reducing the severe side effects associated with conventional chemotherapeutic drugs. However, the lack of nanomedicines able to simultaneously carry anti-cancer drugs and nucleic acids limits the application of this therapeutic strategy. To overcome this issue, we proposed to synthesize a pro-drug dendrimer by conjugating the PEGylated, positively charged generation 3-diaminobutyric polypropylenimine dendrimer to the anti-cancer drug camptothecin with a redox-sensitive disulphide linkage, and evaluate its efficacy to co-deliver the complexed DNA and camptothecin to cancer cells. This PEGylated pro-drug dendrimer was found to spontaneously self-assemble into cationic (∼3-5 mV) vesicles at pH 7.4, at a critical aggregation concentration of about 200 μg mL-1. These vesicles (dendrimersomes) became smaller (150-200 nm) with increasing dendrimer concentration and remained stable over 7 days. They were able to release about 70% of the conjugated camptothecin in presence of 50 mM glutathione (equivalent to the intracellular environment of tumor tissue). They could also condense more than 85% of the DNA at dendrimer : DNA weight ratios of 5 : 1 and higher. DNA condensation occurred instantly and was found to be stable for at least 24 h. This led to an enhanced cellular uptake of DNA (by up to 1.6-fold) and increased gene transfection (by up to 2.4-fold) in prostate cancer cells in comparison with the unmodified dendrimer. These novel dendrimersomes are therefore promising for single carrier-based combination cancer therapy.

Development of transferrin-bearing vesicles encapsulating aspirin for cancer therapy

Originally developed for the treatment of inflammatory disorders, the non-steroidal anti-inflammatory drug aspirin was shown to have a preventive effect against cancer in the past decades. Most importantly, recent studies suggested that it might also provide a therapeutic benefit in the treatment of cancer in vitro. However, this drug failed to specifically reach tumors at a therapeutic concentration following intravenous administration, thus resulting in lack of efficacy on tumors. In this work, we demonstrated that aspirin could be formulated in transferrin-bearing vesicles and that this tumor-targeted formulation could lead to an increase in the anti-proliferative efficacy of the drug in three cancer cell lines in vitro. The in vitro therapeutic efficacy of aspirin was significantly improved when formulated in transferrin-bearing vesicles, by about 2-fold compared to that of drug solution. These results are promising and support the optimization of this delivery system to further improve its potential as a therapeutic tool in combination with other anti-cancer therapies.

Redox-sensitive, cholesterol-bearing PEGylated poly(propylene imine)-based dendrimersomes for drug and gene delivery to cancer cells

Stimuli-responsive nanocarriers have attracted increased attention as materials that can facilitate drug and gene delivery in cancer therapy. The present study reports the development of redox-sensitive dendrimersomes comprising disulfide-linked cholesterol-bearing PEGylated dendrimers, which can be used as drug and gene delivery systems. Two disulfide-linked cholesterol-bearing PEGylated generation 3 diaminobutyric polypropylenimine dendrimers have been successfully synthesized via an in situ two-step reaction. They were able to spontaneously self-assemble into stable, cationic, nanosized vesicles (or dendrimersomes) with lower critical aggregation concentration values for high-cholesterol-bearing vesicles. These dendrimersomes were able to entrap both hydrophilic and hydrophobic dyes, and they also showed a redox-responsive sustained release of the entrapped guests in the presence of a glutathione concentration similar to that of a cytosolic reducing environment. The high-cholesterol-bearing dendrimersomes were found to have a higher melting enthalpy, increased adsorption tendency on mica surface, entrapping ability for a larger amount of hydrophobic drugs, and increased resistance to redox-responsive environments in comparison with their low-cholesterol counterpart. In addition, both dendrimersomes were able to condense more than 85% of the DNA at all the tested ratios for the low-cholesterol vesicles, and at dendrimer : DNA weight ratios of 1 : 1 and higher for the high-cholesterol vesicles. These vesicles resulted in an enhanced cellular uptake of DNA, by up to 15-fold when compared with naked DNA with low-cholesterol vesicles. As a result, they increased the gene transfection on the PC-3 prostate cancer cell line, with the highest transfection being obtained with low-cholesterol vesicle complexes at a dendrimer : DNA weight ratio of 5 : 1 and high-cholesterol vesicle complexes at a dendrimer : DNA weight ratio of 10 : 1. These transfection levels were about 5-fold higher than those observed when treated with naked DNA. These cholesterol-bearing PEGylated dendrimer-based vesicles are, therefore, promising as redox-sensitive drugs and gene delivery systems for potential applications in combination cancer therapies.

PEGylation of polypropylenimine dendrimers: effects on cytotoxicity, DNA condensation, gene delivery and expression in cancer cells

Diaminobutyric polypropylenimine (DAB) dendrimers have been shown to be highly efficient non-viral gene delivery systems for cancer therapy. However, their cytotoxicity currently limits their applications. To overcome this issue, PEGylation of DAB dendrimer, using various PEG molecular weights and dendrimer generations, has been attempted to decrease the cytotoxicity and enhance the DNA condensation, size and zeta potential, cellular uptake and transfection efficacy of these dendriplexes. Among all the PEGylated dendrimers synthesized, generation 3- and generation 4-DAB conjugated to low molecular weight PEG (2 kDa) at a dendrimer: DNA ratio of 20:1 and 10:1 resulted in an increase in gene expression on almost all tested cancer cells lines (by up to 3.2-fold compared to unmodified dendrimer in A431 cells). The highest level of β-galactosidase gene expression (10.07 × 10^-3 ± 0.09 × 10^-3 U/mL) was obtained following treatment of B16F10-Luc cells with G4-dendrimer PEGylated with PEG2K at a dendrimer: DNA ratio of 20:1. These delivery systems significantly decreased cytotoxicity on B16F10-Luc cells, by more than 3.4-fold compared to unmodified dendrimer. PEGylated generations 3- and 4-DAB dendrimers are therefore promising gene delivery systems for cancer therapy, combining low cytotoxicity and high transfection efficacy.

Nanomedicine in the application of uveal melanoma

Rapid advances in nanomedicine have significantly changed many aspects of nanoparticle application to the eye including areas of diagnosis, imaging and more importantly drug delivery. The nanoparticle-based drug delivery systems has provided a solution to various drug solubility-related problems in ophthalmology treatment. Nanostructured compounds could be used to achieve local ocular delivery with minimal unwanted systematic side effects produced by taking advantage of the phagocyte system. In addition, the in vivo control release by nanomaterials encapsulated drugs provides prolong exposure of the compound in the body. Furthermore, certain nanoparticles can overcome important body barriers including the blood-retinal barrier as well as the corneal-retinal barrier of the eye for effective delivery of the drug. In summary, the nanotechnology based drug delivery system may serve as an important tool for uveal melanoma treatment.

Dendritic Polymers for Theranostics

Dendritic polymers are highly branched polymers with controllable structures, which possess a large population of terminal functional groups, low solution or melt viscosity, and good solubility. Their size, degree of branching and functionality can be adjusted and controlled through the synthetic procedures. These tunable structures correspond to application-related properties, such as biodegradability, biocompatibility, stimuli-responsiveness and self-assembly ability, which are the key points for theranostic applications, including chemotherapeutic theranostics, biotherapeutic theranostics, phototherapeutic theranostics, radiotherapeutic theranostics and combined therapeutic theranostics. Up to now, significant progress has been made for the dendritic polymers in solving some of the fundamental and technical questions toward their theranostic applications. In this review, we briefly summarize how to control the structures of dendritic polymers, the theranostics-related properties derived from their structures and their theranostics-related applications.

Applications of dendrimers for brain delivery and cancer therapy

Dendrimers are emerging as potential nonviral vectors for the efficient delivery of drugs and nucleic acids to the brain and cancer cells. These polymers are highly branched, 3D macromolecules with modifiable surface functionalities and available internal cavities that make them attractive as delivery systems for drug and gene delivery applications. This article highlights the recent therapeutic advances resulting from the use of dendrimers for brain targeting and cancer treatment.

Tumor regression following intravenous administration of lactoferrin- and lactoferricin-bearing dendriplexes

The possibility of using gene therapy for the treatment of cancer is limited by the lack of safe, intravenously administered delivery systems able to selectively deliver therapeutic genes to tumors. In this study, we investigated if the conjugation of the polypropylenimine dendrimer to lactoferrin and lactoferricin, whose receptors are overexpressed on cancer cells, could result in a selective gene delivery to tumors and a subsequently enhanced therapeutic efficacy. The conjugation of lactoferrin and lactoferricin to the dendrimer significantly increased the gene expression in the tumor while decreasing the non-specific gene expression in the liver. Consequently, the intravenous administration of the targeted dendriplexes encoding TNFα led to the complete suppression of 60% of A431 tumors and up to 50% of B16-F10 tumors over one month. The treatment was well tolerated by the animals. These results suggest that these novel lactoferrin- and lactoferricin-bearing dendrimers are promising gene delivery systems for cancer therapy.

From the Clinical Editor

Specific targeting of cancer cells should enhance the delivery of chemotherapeutic agents. This is especially true for gene delivery. In this article, the authors utilized a dendrimer-based system and conjugated this with lactoferrin and lactoferricin to deliver anti-tumor genes. The positive findings in animal studies should provide the basis for further clinical studies.

Triazine-modified dendrimer for efficient TRAIL gene therapy in osteosarcoma

Osteosarcoma is a high-grade malignant bone tumor that usually develops in the teenagers. Despite improvement in therapy, the five-year survival rate is poor for patients not responding to treatment or with metastases. Tumor necrosis factor (TNF) related apoptosis inducing ligand (TRAIL) gene therapy is a new strategy in the treatment of cancers, however, the lack of efficient and low toxic vectors remains the major obstacle in TRAIL gene therapy. In this study, a triazine-modified dendrimer G5-DAT66 was synthesized and used as a vector for TRAIL gene therapy in vitro and in vivo. The material shows much higher transfection efficacy on osteosarcoma MG-63 cell line than commercial transfection reagents such as Lipofectamine 2000 and SuperFect. It effectively induces apoptosis in MG-63 cells and three-dimensional MG-63 cell cultures when delivering a TRAIL plasmid. In vivo studies further prove that G5-DAT66 efficiently transfects TRAIL plasmid in tumors and inhibits tumor growth in osteosarcoma-bearing mice. These results suggest that triazine-modified dendrimer has promising potential for TRAIL gene therapy in osteosarcoma.

Recent advances in targeted nanoparticles drug delivery to melanoma

Melanoma is one of the most aggressive skin cancers, notorious for its high multidrug resistance and low survival rate. Conventional therapies (e.g., dacarbazine, interferon-alpha-2b and interleukin-2) are limited by low response rate and demonstrate no overall survival benefit. Novel targeted therapies (e.g., vemurafenib, dabrafenib and trametinib) have higher initial response rate and clear impact on the overall survival, but relapse usually occurs within 6 to 9 months. Although immunotherapy (e.g., ipilimumab, pembrolizumab and nivolumab) can achieve long-term and durable response, rate of adverse events is extremely high. With the development of nanotechnology, the applications of nanocarriers are widely expected to change the landscape of melanoma therapy for foreseeable future. In this review, we will relate recent advances in the application of multifunctional nanocarriers for targeted drug delivery to melanoma, in melanoma nanotheranostics and combination therapy, and nanopharmaceutical associated melanoma clinical trials, followed by challenges and perspectives. From the clinical editor: The team of authors describes the current treatment regimes of malignant melanoma emphasizing the importance of achieving a better efficacy and the need to develop a better understanding of melanoma tumorigenesis.

Therapeutic efficacy of intravenously administered transferrin-conjugated dendriplexes on prostate carcinomas

AIM

Improved treatments for prostate cancer are critically needed in order to overcome metastasis and lethal recurrence. Intravenously administered gene therapy would be an attractive anticancer treatment strategy; however, the lack of suitable carrier systems able to selectively deliver therapeutic genes to tumors has so far limited this investigation. Given that transferrin receptors are overexpressed on prostate cancer cells, the purpose of this study is to determine whether transferrin-conjugated dendriplexes encoding TNF-α, TNF-related apoptosis-inducing ligand and IL-12 would suppress the growth of prostate cancer cell lines in vitro and in vivo.

MATERIALS & METHODS

Transferrin-conjugated dendriplexes encoding TNF-α, TNF-related apoptosis-inducing ligand and IL-12 were intravenously administered to mice bearing subcutaneous PC-3 and DU145 tumors.

RESULTS

The administration of the transferrin-conjugated generation 3 diaminobutyric polypropylenimine dendriplex encoding TNF-a resulted in tumor suppression for 60% of PC-3 and 50% of DU145 prostate tumors.

CONCLUSION

These dendriplexes hold great potential as a novel approach for prostate cancer therapy.

Gene therapy and imaging in preclinical and clinical oncology: recent developments in therapy and theranostics

In the case of disseminated cancer, current treatment options reach their limit. Gene theranostics emerge as an innovative route in the treatment and diagnosis of cancer and might pave the way towards development of an efficacious treatment of currently incurable cancer. Various gene vectors have been developed to realize tumor-specific nucleic acid delivery and are considered crucial for the successful application of cancer gene therapy. By adding reporter genes and imaging agents, these systems gain an additional diagnostic function, thereby advancing the theranostic paradigm into cancer gene therapy. Numerous preclinical studies have demonstrated the feasibility of combined tumor gene therapy and diagnostic imaging, and clinical trials in human and veterinary oncology have been executed with partly encouraging results.

Transferrin-bearing polypropylenimine dendrimer for targeted gene delivery to the brain

The possibility of using genes as medicines to treat brain diseases is currently limited by the lack of safe and efficacious delivery systems able to cross the blood-brain barrier, thus resulting in a failure to reach the brain after intravenous administration. On the basis that iron can effectively reach the brain by using transferrin receptors for crossing the blood-brain barrier, we propose to investigate if a transferrin-bearing generation 3-polypropylenimine dendrimer would allow the transport of plasmid DNA to the brain after intravenous administration. In vitro, the conjugation of transferrin to the polypropylenimine dendrimer increased the DNA uptake by bEnd.3 murine brain endothelioma cells overexpressing transferrin receptors, by about 1.4-fold and 2.3-fold compared to that observed with the non-targeted dendriplex and naked DNA. This DNA uptake appeared to be optimal following 2h incubation with the treatment. In vivo, the intravenous injection of transferrin-bearing dendriplex more than doubled the gene expression in the brain compared to the unmodified dendriplex, while decreasing the non-specific gene expression in the lung. Gene expression was at least 3-fold higher in the brain than in any tested peripheral organs and was at its highest 24h following the injection of the treatments. These results suggest that transferrin-bearing polypropylenimine dendrimer is a highly promising gene delivery system to the brain.

Transferrin and the transferrin receptor for the targeted delivery of therapeutic agents to the brain and cancer cells

The potential use of many promising novel drugs is limited by their inability to specifically reach their site of action after intravenous administration, without secondary effects on healthy tissues. In order to remediate this problem, the protein transferrin (Tf) has been extensively studied as a targeting molecule for the transport of drug and gene delivery systems to the brain and cancer cells. A wide range of delivery approaches have been developed to target the Tf receptor and they have already improved the specific delivery of Tf-bearing therapeutic agents to their site of action. This review provides a summary of the numerous delivery strategies used to target the Tf receptor and focuses on recent therapeutic advances.

Role of wild type p53 and double suicide genes in interventional therapy of liver cancer in rabbits

PURPOSE

To investigate the feasibility of interventional lipiodol embolism and multigene therapy in combination with focal chemotherapy in the treatment of VX2 liver cancer in rabbits.

METHODS

Forty five rabbits with cancer larger than 2cm in diameter were randomly divided into five groups (n=9 per group). In Group 1, animals were treated with 0.9% sodium chloride. In Group 2, animals received lipiodol embolism. In Group 3, animals received lipiodol embolism and p53 gene therapy. In Group 4, animals received lipiodol embolism and TK/CD gene therapy. In Group 5, animals received lipiodol embolism and p53 and TK/CD gene therapy. Ultrasonography and CT were performed before and at ten days after interventional therapy.

RESULTS

The VX2 model of liver cancer was successfully established in rabbits and interventional therapy smoothly performed. At ten days after interventional therapy, significant difference in the tumor volume was noted among five groups (p<0.05) and different treatments could inhibit the cancer growth. The inhibition of cancer growth was the most evident in the Group 5. Factorial analysis revealed gene therapy with p53 or TK/CD and lipiodol embolism independently exert significantly inhibitory effect on cancer growth. In addition, the suppression on tumor growth rate was the most obvious in the Group 5.

CONCLUSIONS

Combination of gene therapy with lipiodol embolism can effectively inhibit the cancer growth and prolong the survival time. These findings demonstrate the effectiveness of multigene therapy in combination with lipiodol embolism in the treatment of liver cancer.

Antitumor activity of the tea polyphenol epigallocatechin-3-gallate encapsulated in targeted vesicles after intravenous administration

AIM

The therapeutic potential of epigallocatechin-3-gallate (EGCG), a green tea polyphenol with anticancer properties, is limited by its inability to specifically reach tumors following intravenous administration. The purpose of this study was to determine whether a tumor-targeted vesicular formulation of EGCG would suppress the growth of A431 epidermoid carcinoma and B16-F10 melanoma in vitro and in vivo.

MATERIALS & METHODS

Transferrin-bearing vesicles encapsulating EGCG were administered intravenously to mice bearing subcutaneous A431 and B16-F10 tumors.

RESULTS

The intravenous administration of EGCG encapsulated in transferrin-bearing vesicles resulted in tumor suppression in 40% of A431 and B16-F10 tumors. Animal survival was improved by more than 20 days compared with controls.

CONCLUSION

Encapsulation of EGCG in transferrin-bearing vesicles is a promising therapeutic strategy.