Nonviral delivery vehicles for use in short hairpin RNA-based cancer therapies

Lipid-based nucleic acid therapeutics with in vivo efficacy

Synthetic vectors for therapeutic nucleic acid delivery are currently competing significantly with their viral counter parts due to their reduced immunogenicity, large payload capacity, and ease of manufacture under GMP-compliant norms. The approval of Onpattro, a lipid-based siRNA therapeutic, and the proven clinical success of two lipid-based COVID-19 vaccines from Pfizer-BioNTech, and Moderna heralded the specific advantages of lipid-based systems among all other synthetic nucleic acid carriers. Lipid-based systems with diverse payloads-plasmid DNA (pDNA), antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA (miRNA), small activating RNA (saRNA), and messenger RNA (mRNA)-are now becoming a mature technology, with growing impact in the clinic. Research over four decades identified the key factors determining the therapeutic success of these multi-component systems. Here, we discuss the main nucleic acid-based technologies, presenting their mechanism of action, delivery barriers facing them, the structural properties of the payload as well as the component lipids that regulate physicochemical properties, pharmacokinetics and biodistribution, efficacy, and toxicity of the resultant nanoparticles. We further detail on the formulation parameters, evolution of the manufacturing techniques that generate reproducible and scalable outputs, and key manufacturing aspects that enable control over physicochemical properties of the resultant particles. Preclinical applications of some of these formulations that were successfully translated from in vitro studies to animal models are subsequently discussed. Finally, clinical success and failure of these systems starting from 1993 to present are highlighted, in a holistic literature review focused on lipid-based nucleic acid delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Recent developments in targeting genes and pathways by RNAi-based approaches in colorectal cancer

A wide spectrum of genetic and epigenetic variations together with environmental factors has made colorectal cancer (CRC), which involves the colon and rectum, a challenging and heterogeneous cancer. CRC cannot be effectively overcomed by common conventional therapies including surgery, chemotherapy, targeted therapy, and hormone replacement which highlights the need for a rational design of novel anticancer therapy. Accumulating evidence indicates that RNA interference (RNAi) could be an important avenue to generate great therapeutic efficacy for CRC by targeting genes that are responsible for the viability, cell cycle, proliferation, apoptosis, differentiation, metastasis, and invasion of CRC cells. In this review, we underline the documented benefits of small interfering RNAs and short hairpin RNAs to target genes and signaling pathways related to CRC tumorigenesis. We address the synergistic effects of RNAi-mediated gene knockdown and inhibitors/chemotherapy agents to increase the sensitivity of CRC cells to common therapies. Finally, this review points new delivery systems/materials for improving the cellular uptake efficiency and reducing off-target effects of RNAi.

Combinatorial therapeutic approaches with RNAi and anticancer drugs using nanodrug delivery systems

RNA interference (RNAi) is emerging as a powerful approach in cancer treatment. siRNA is an important RNAi tool that can be designed to specifically silence the expression of genes involved in drug resistance and chemotherapeutic inactivity. Combining siRNA and other therapeutic agents can overcome the multidrug resistance (MDR) phenomenon by simultaneously silencing genes and enhancing chemotherapeutic activity. Moreover, the therapeutic efficiency of anticancer drugs can be significantly improved by additive or synergistic effects induced by siRNA and combined therapies. Co-delivery of these diverse anticancer agents, however, requires specially designed nanocarriers. This review highlights the recent trends in siRNA/anticancer drug co-delivery systems under the major categories of liposomes/lipid, polymeric and inorganic nanoplatforms. The objective is to discuss the strategies for nanocarrier-based co-delivery systems using siRNA/anticancer drug combinations, emphasizing various siRNA targets that help overcome MDR and enhance therapeutic efficiency.

Inhaled gene delivery: a formulation and delivery approach

INTRODUCTION

Gene therapy is a potential alternative to treat a number of diseases. Different hurdles are associated with aerosol gene delivery due to the susceptibility of plasmid DNA (pDNA) structure to be degraded during the aerosolization process. Different strategies have been investigated in order to protect and efficiently deliver pDNA to the lungs using non-viral vectors. To date, no successful therapy involving non-viral vectors has been marketed, highlighting the need for further investigation in this field. Areas covered: This review is focused on the formulation and delivery of DNA to the lungs, using non-viral vectors. Aerosol gene formulations are divided according to the current delivery systems for the lung: nebulizers, dry powder inhalers and pressurized metered dose inhalers; highlighting its benefits, challenges and potential application. Expert opinion: Successful aerosol delivery is achieved when the supercoiled DNA structure is protected during aerosolization. A formulation strategy or compounds that can protect, stabilize and efficiently transfect DNA into the cells is desired in order to produce an effective, low-cost and safe formulation. Nebulizers and dry powder inhalers are the most promising approaches to be used for aerosol delivery, due to the lower shear forces involved. In this context it is also important to highlight the importance of considering the 'pDNA-formulation-device system' as an integral part of the formulation development for a successful nucleic acid delivery.

MicroRNAs as therapeutic targets in human cancers

MicroRNAs (miRNAs) are evolutionarily conserved, small, regulatory RNAs that negatively regulate gene expression. Extensive research in the last decade has implicated miRNAs as master regulators of cellular processes with essential role in cancer initiation, progression, and metastasis, making them promising therapeutic tools for cancer management. In this article, we will briefly review the structure, biogenesis, functions, and mechanism of action of these miRNAs, followed by a detailed analysis of the therapeutic potential of these miRNAs. We will focus on the strategies presently used for miRNA therapy; discuss their use and drawbacks; and the challenges and future directions for the development of miRNA-based therapy for human cancers.

Ewing's Sarcoma: Development of RNA Interference-Based Therapy for Advanced Disease

Ewing's sarcoma tumors are associated with chromosomal translocation between the EWS gene and the ETS transcription factor gene. These unique target sequences provide opportunity for RNA interference(i)-based therapy. A summary of RNAi mechanism and therapeutically designed products including siRNA, shRNA and bi-shRNA are described. Comparison is made between each of these approaches. Systemic RNAi-based therapy, however, requires protected delivery to the Ewing's sarcoma tumor site for activity. Delivery systems which have been most effective in preclinical and clinical testing are reviewed, followed by preclinical assessment of various silencing strategies with demonstration of effectiveness to EWS/FLI-1 target sequences. It is concluded that RNAi-based therapeutics may have testable and achievable activity in management of Ewing's sarcoma.

shRNA-mediated gene knockdown in skeletal muscle

RNA interference appears as a promising tool for therapeutic gene silencing to block protein expression. A long-lived silencing is obtained through the in situ expression of shRNA. A safe approach is to use a physical method such as in vivo electropulsation with plate electrodes. This is presently validated in muscles by the in vivo coelectrotransfer of plasmids specifically coding for expression and silencing of a fluorescent protein. No long-lived tissue damage is observed by the proper choice of the electric pulsing parameters and the amount of injected plasmids. Using a noninvasive fluorescence imaging assay, electrodelivery in mouse muscles is observed to induce complete silencing over more than 2 months in a specific way. The proper choices of the plasmids (sequence, promoter, and relative amounts) appear as key parameters in the successful long-term silencing.

Personalized cancer approach: using RNA interference technology

Normal cellular survival is dependent on the cooperative expression of genes' signaling through a broad array of DNA patterns. Cancer, however, has an Achilles' heel. Its altered cellular survival is dependent on a limited subset of signals through mutated DNA, possibly as few as three. Identification and control of these signals through the use of RNA interference (RNAi) technology may provide a unique clinical opportunity for the management of cancer that employs genomic-proteomic profiling to provide a molecular characterization of the cancer, leading to targeted therapy customized to an individual cancer signal. Such an approach has been described as "personalized therapy." The present review identifies unique developing technology that employs RNAi as a method to target, and therefore block, signaling from mutated DNA and describes a clinical pathway toward its development in cancer therapy.

A new liposome-based gene delivery system targeting lung epithelial cells using endothelin antagonist

We formulated a new gene delivery system based on targeted liposomes. The efficacy of the delivery system was demonstrated in in vitro and in vivo models. The targeting moiety consists of a high-affinity 7-amino-acid peptide, covalently and evenly conjugated to the liposome surface. The targeting peptide acts as an endothelin antagonist, and accelerates liposome binding and internalization. It is devoid of other biological activity. Liposomes with high phosphatidyl serine (PS) were specially formulated to help their fusion with the endosomal membrane at low pH and enable release of the liposome payload into the cytoplasm. A DNA payload, pre-compressed by protamine, was encapsulated into the liposomes, which directed the plasmid into the cell's nucleus. Upon exposure to epithelial cells, binding of the liposomes occurred within 5-10 min, followed by facilitated internalization of the complex. Endosomal escape was complete within 30 min, followed by DNA accumulation in the nucleus 2h post-transfection. A549 lung epithelial cells transfected with plasmid encoding for GFP encapsulated in targeted liposomes expressed significantly more protein than those transfected with plasmid complexed with Lipofectamine. The intra-tracheal instillation of plasmid encoding for GFP encapsulated in targeted liposomes into rat lungs resulted in the expression of GFP in bronchioles and alveoli within 5 days. These results suggest that this delivery system has great potential in targeting genes to lungs.

See, reach, treat: ultrasound-triggered image-guided drug delivery

The integration of therapeutic interventions with diagnostic imaging has been recognized as one of the next technological developments that will have a major impact on medical treatments. Therapeutic applications using ultrasound, for example thermal ablation, hyperthermia or ultrasound-induced drug delivery, are examples for image-guided interventions that are currently being investigated. While thermal ablation using magnetic resonance-guided high-intensity focused ultrasound is entering the clinic, ultrasound-mediated drug delivery is still in a research phase, but holds promise to enable new applications in localized treatments. The use of ultrasound for the delivery of drugs has been demonstrated, particularly in the field of cardiology and oncology for a variety of therapeutics ranging from small-molecule drugs to biologics and nucleic acids exploiting temperature- or pressure-mediated delivery schemes.

Development of microRNA-145 for therapeutic application in breast cancer

MicroRNAs, small non-coding RNAs, are key regulators of tumorigenesis and cancer metastasis through inhibition of gene expression. Therefore, there is increasing interest in developing anti-cancer therapies using microRNAs. In this study, we determined the therapeutic potency of microRNA-145(miR-145) against breast cancer. We found a reverse-correlation between the expression of miR-145 and its target genes, such as fascin-1, c-myc, SMAD2/3 and IGF-1R in breast cancer cell lines and breast cancer patient tissues. Transfected miR-145 mimicking double-stranded oligonucleotides was directly reduced cell proliferation and motility via interaction with 3'UTR of target gene and also indirectly regulates Wnt signaling. An inhibitor of miR-145 nullified this decreasing effect of miR-145 on cell proliferation and motility. We prepared an adenoviral constructed miR-145(Ad-miR-145) and subjected it to breast cancer cells in vitro and orthotopic breast cancer mice in vivo. Ad-miR-145 suppressed cell growth and motility in both the in vitro and in vivo systems. Furthermore, a treatment combining Ad-miR-145 with 5-FU significantly showed anti-tumor effects, compared to treating alone. In conclusion, this study demonstrated that miR-145 suppresses tumor growth by inhibition of multiple tumor survival effectors, and more we suppose that miR-145 is potentially useful in the therapy of breast cancers.

MicroRNAs, cancer and cancer stem cells

MicroRNAs regulate self-renewal, differentiation, and division of cells via post-transcriptional gene silencing. Aberrant microRNA levels, specifically an overall downregulation, are present in many cancers, as compared to their normal tissue counterparts. Therefore, a potential therapeutic use of microRNAs is to correct these aberrant transcript levels involved in the signaling pathways of cancer. This review focuses on the current knowledge of microRNAs and their involvement with cancer cells and cancer stem cells. The methods currently being used to develop miRNA-based cancer therapeutics are examined, and the limitations halting further progress are also discussed.

Potential use of RNA interference in cancer therapy

RNA interference (RNAi) is an evolutionary conserved mechanism for specific gene silencing. This mechanism has great potential for use in targeted cancer therapy. Understanding the RNAi mechanism has led to the development of several novel RNAi-based therapeutic approaches currently in the early phases of clinical trials. It remains difficult to effectively deliver the nucleic acids required in vivo to initiate RNAi, and intense effort is under way in developing effective and targeted systemic delivery systems for RNAi. Description of in vivo delivery systems is not the focus of this review. In this review, we cover the rationale for pursuing personalised cancer therapy with RNAi, briefly review the mechanism of each major RNAi therapeutic technique, summarise and sample recent results with animal models applying RNAi for cancer, and provide an update on current clinical trials with RNAi-based therapeutic agents for cancer therapy. RNAi-based cancer therapy is still in its infancy, and there are numerous obstacles and issues that need to be resolved before its application in personalised therapy focusing on patient-cancer-specific targets can become standard cancer treatment, either alone or in combination with other treatments.

RNAi as a new therapeutic strategy against HCV

Hepatitis C virus is a major cause of liver associated diseases all over the world. Irrespective of the significant advances in the current therapy, drugs and vaccines are restricted with many factors such as toxicity, complexity, cost and resistance. New technologies particularly RNA interference (RNAi) mediated by small interfering RNA (siRNA) have become more and more interesting and effective therapeutic entities to silence pathogenic gene products associated with disease, including cancer, viral infections and autoimmune disorders. RNAi works at a posttranscriptional level by targeting mRNA as a mean for inhibiting the synthesis of the encoded protein. Several reports have indicated the efficiency and specificity of synthetic and vector based siRNAs inhibiting HCV replication. In the present review, we focused on the recent development in the potential use and issues regarding siRNA as a therapy for HCV.

RNA inhibition, microRNAs, and new therapeutic agents for cancer treatment

Over the past few years, molecular oncology research has revealed that abnormalities in both protein-coding genes (PCGs) and noncoding RNAs (ncRNAs) can be identified in tumors and that the interplay between PCGs and ncRNAs is causally involved in the initiation, progression, and metastases of human cancers. MicroRNAs (miRNAs), which are among the most studied ncRNAs, are small 19- to 25-nucleotide genes involved in the regulation of PCGs and other ncRNAs. With the recent findings of miRNAs' involvement in cancer, RNA inhibition can be used to treat cancer patients in two ways: (1) by using RNA or DNA molecules as therapeutic drugs against messenger RNA of genes involved in the pathogenesis of cancers and (2) by directly targeting ncRNAs that participate in cancer pathogenesis. In this review, we focus on the possible use of miRNAs or compounds interacting with miRNAs as new therapeutic agents in cancer patients.

siRNA vs. shRNA: similarities and differences

RNA interference (RNAi) is a natural process through which expression of a targeted gene can be knocked down with high specificity and selectivity. Using available technology and bioinformatics investigators will soon be able to identify relevant bio molecular tumor network hubs as potential key targets for knockdown approaches. Methods of mediating the RNAi effect involve small interfering RNA (siRNA), short hairpin RNA (shRNA) and bi-functional shRNA. The simplicity of siRNA manufacturing and transient nature of the effect per dose are optimally suited for certain medical disorders (i.e. viral injections). However, using the endogenous processing machinery, optimized shRNA constructs allow for high potency and sustainable effects using low copy numbers resulting in less off-target effects, particularly if embedded in a miRNA scaffold. Bi-functional design may further enhance potency and safety of RNAi-based therapeutics. Remaining challenges include tumor selective delivery vehicles and more complete evaluation of the scope and scale of off-target effects. This review will compare siRNA, shRNA and bi-functional shRNA.

Use of liposomes as drug delivery vehicles for treatment of melanoma

Melanoma is a progressive disease that claims many lives each year due to lack of therapeutics effective for the long-term treatment of patients. Currently, the best treatment option is early detection followed by surgical removal. Better melanoma therapies that are effectively delivered to tumors with minimal toxicity for patients are urgently needed. Nanotechnologies provide one approach to encapsulate therapeutic agents leading to improvements in circulation time, enhanced tumor uptake, avoidance of the reticulo-endothelial system, and minimization of toxicity. Liposomes in particular are a promising nanotechnology that can be used for more effective delivery of therapeutic agents to treat melanoma. Liposomes delivering chemotherapies, siRNA, asODNs, DNA, and radioactive particles are just some of the promising new nanotechnology based therapies under development for the treatment of melanoma that are discussed in this review.

Progress and prospects: the design and production of plasmid vectors

Plasmid DNA (pDNA) expression vectors are fundamental to all forms of non-viral gene transfer. In this review, we discuss principles of pDNA design and production including the impact of bacterially derived sequences on transgene expression and minicircle approaches to minimize their effects. The impact of inclusion of DNA elements such as scaffold matrix attachment regions (S/MARs), transcription factor (TF)-binding sites and tissue-specific promoters are described. The benefits of eliminating CG dinucleotides (CpGs) from the pDNA are also considered.

Targeting hypoxia-inducible factor-1alpha with Tf-PEI-shRNA complex via transferrin receptor-mediated endocytosis inhibits melanoma growth

Malignant melanoma (MM) is a major public health problem. The development of effective, systemic therapies for MM is highly desired. We showed here that the transferrin receptor (TfR) was a suitable surface marker for targeting of gene therapy in MM and that the hypoxia-inducible factor-1alpha (HIF-1alpha) was an attractive therapeutic molecular target in MM. We observed that inhibition of HIF-1alpha blocked cell proliferation and induced cell apoptosis in vitro. We then showed that a transferrin-polyethylenimine-HIF-1alpha-short-hairpin RNA (Tf-PEI-HIF-1alpha-shRNA) complex could target MM specifically and efficiently both in vivo and in vitro, exploiting the high expression of the TfR in MM. The systemic delivery of sequence-specific small-interfering RNA (siRNA) against HIF-1alpha by the Tf- PEI-HIF-1alpha-shRNA complex dramatically inhibited tumor growth in the A375 MM xenograft model. The underlying concept of transfecting a HIF-1alpha shRNA expression vector complexed with Tf-PEI to block HIF-1alpha holds promise as a clinical approach to gene therapy for MM.

Manipulation of PKC isozymes by RNA interference and inducible expression of PKC constructs

Protein kinase C (PKC), a family of serine/threonine kinases, plays an important role in apoptosis. Several members of the PKC family act as substrates for caspases. In addition, PKCs can also regulate caspase activation and cell death by apoptosis. The cleavage of PKCs separates the regulatory domain from the catalytic domain. The full-length, the catalytic domain, and the regulatory domain of PKC family members may have distinct function in apoptosis. Delineating the role of protein kinase C (PKC) isozymes in apoptosis has been challenging because of the lack of selective inhibitors of PKC isozymes and difficulty in generating stable cell lines expressing pro-apoptotic PKC isozymes. In this chapter, we describe the use of RNA interference (siRNA) technology and tetracycline-inducible expression of PKC isozymes to study their function in apoptosis.

Maintaining the silence: reflections on long-term RNAi

Since the demonstration of RNA interference (RNAi) in mammalian cells, considerable research and financial effort has gone towards implementing RNAi as a viable therapeutic platform. RNAi is, without doubt, the most promising strategy for the treatment of human genetic disorders. Because many of the targets proposed for RNAi therapy require chronic treatment, researchers agree that the emphasis must now be placed on the safe and long-term application of RNAi drugs to reap the benefits at last.

Ethical perspectives on RNA interference therapeutics

RNA interference is a mechanism for controlling normal gene expression which has recently begun to be employed as a potential therapeutic agent for a wide range of disorders, including cancer, infectious diseases and metabolic disorders. Clinical trials with RNA interference have begun. However, challenges such as off-target effects, toxicity and safe delivery methods have to be overcome before RNA interference can be considered as a conventional drug. So, if RNA interference is to be used therapeutically, we should perform a risk-benefit analysis. It is ethically relevant to perform a risk-benefit analysis since ethical obligations about not inflicting harm and promoting good are generally accepted. But the ethical issues in RNA interference therapeutics not only include a risk-benefit analysis, but also considerations about respecting the autonomy of the patient and considerations about justice with regard to the inclusion criteria for participation in clinical trials and health care allocation. RNA interference is considered a new and promising therapeutic approach, but the ethical issues of this method have not been greatly discussed, so this article analyses these issues using the bioethical theory of principles of the American bioethicists, Tom L. Beauchamp and James F. Childress.

Long-lasting In vivo Gene Silencing by Electrotransfer of shRNA Expressing Plasmid

RNA interference appears as a promising tool for therapeutic gene silencing. A key limit is the delivery of the siRNA. A safe approach is to use a physical method such as in vivo electropulsation with contact electrodes. Getting a long lived silencing can be better approached by using the in situ expression of shRNA. This is presently obtained by using co-electrotransfer of specific plasmids coding for expression and silencing of a fluorescent protein. Using a non invasive fluorescence imaging assay, electrodelivery in mouse muscles is observed to induce complete silencing over more than two months in a specific way. The proper choices of the plasmids (sequence and relative amounts) and of the electric pulsing conditions appear as key parameters in the successful silencing.

Nonviral delivery of synthetic siRNAs in vivo

Sequence-specific gene silencing using small interfering RNA (siRNA) is a Nobel prize-winning technology that is now being evaluated in clinical trials as a potentially novel therapeutic strategy. This article provides an overview of the major pharmaceutical challenges facing siRNA therapeutics, focusing on the delivery strategies for synthetic siRNA duplexes in vivo, as this remains one of the most important issues to be resolved. This article also highlights the importance of understanding the genocompatibility/toxicogenomics of siRNA delivery reagents in terms of their impact on gene-silencing activity and specificity. Collectively, this information is essential for the selection of optimally acting siRNA delivery system combinations for the many proposed applications of RNA interference.