RNAi-based nanomedicines for targeted personalized therapy

Multifunctional polymeric micelles for delivery of drugs and siRNA

Polymeric micelles, self-assembling nano-constructs of amphiphilic copolymers with a core-shell structure have been used as versatile carriers for delivery of drugs as well as nucleic acids. They have gained immense popularity owing to a host of favorable properties including their capacity to effectively solubilize a variety of poorly soluble pharmaceutical agents, biocompatibility, longevity, high stability in vitro and in vivo and the ability to accumulate in pathological areas with compromised vasculature. Moreover, additional functions can be imparted to these micelles by engineering their surface with various ligands and cell-penetrating moieties to allow for specific targeting and intracellular accumulation, respectively, to load them with contrast agents to confer imaging capabilities, and incorporating stimuli-sensitive groups that allow drug release in response to small changes in the environment. Recently, there has been an increasing trend toward designing polymeric micelles which integrate a number of the above functions into a single carrier to give rise to “smart,” multifunctional polymeric micelles. Such multifunctional micelles can be envisaged as key to improving the efficacy of current treatments which have seen a steady increase not only in hydrophobic small molecules, but also in biologics including therapeutic genes, antibodies and small interfering RNA (siRNA). The purpose of this review is to highlight recent advances in the development of multifunctional polymeric micelles specifically for delivery of drugs and siRNA. In spite of the tremendous potential of siRNA, its translation into clinics has been a significant challenge because of physiological barriers to its effective delivery and the lack of safe, effective and clinically suitable vehicles. To that end, we also discuss the potential and suitability of multifunctional polymeric micelles, including lipid-based micelles, as promising vehicles for both siRNA and drugs.

Design and in vitro evaluation of layer by layer siRNA nanovectors targeting breast tumor initiating cells

Efficient therapeutics and early detection has helped to increase breast cancer survival rates over the years. However, the recurrence of breast cancer remains to be a problem and this may be due to the presence of a small population of cells, called tumor initiating cells (TICs). Breast TICs are resistant to drugs, difficult to detect, and exhibit high self-renewal capabilities. In this study, layer by layer (LBL) small interfering RNA (siRNA) nanovectors (SNVs) were designed to target breast TICs. SNVs were fabricated using alternating layers of poly-L-lysine and siRNA molecules on gold (Au) nanoparticle (NP) surfaces. The stability, cell uptake, and release profile for SNVs were examined. In addition, SNVs reduced TIC-related STAT3 expression levels, CD44⁺/CD24⁻/EpCAM⁺ surface marker levels and the number of mammospheres formed compared to the standard transfection agent. The data from this study show, for the first time, that SNVs in LBL assembly effectively delivers STAT3 siRNA and inhibit the growth of breast TICs in vitro.

miR-Synth: a computational resource for the design of multi-site multi-target synthetic miRNAs

RNAi is a powerful tool for the regulation of gene expression. It is widely and successfully employed in functional studies and is now emerging as a promising therapeutic approach. Several RNAi-based clinical trials suggest encouraging results in the treatment of a variety of diseases, including cancer. Here we present miR-Synth, a computational resource for the design of synthetic microRNAs able to target multiple genes in multiple sites. The proposed strategy constitutes a valid alternative to the use of siRNA, allowing the employment of a fewer number of molecules for the inhibition of multiple targets. This may represent a great advantage in designing therapies for diseases caused by crucial cellular pathways altered by multiple dysregulated genes. The system has been successfully validated on two of the most prominent genes associated to lung cancer, c-MET and Epidermal Growth Factor Receptor (EGFR). (See http://microrna.osumc.edu/mir-synth).

Intracellular microenvironment responsive polymers: a multiple-stage transport platform for high-performance gene delivery

A new strategy for promoting endoplasmic gene delivery and nucleus uptake is proposed by developing intracellular microenvironment responsive biocompatible polymers. This delivery system can efficiently load and self-assemble nucleic acids into nano-structured polyplexes at a neutral pH, release smaller imidazole-gene complexes from the polymer backbones at intracellular endosomal pH, transport nucleic acids into nucleus through intracellular environment responsive multiple-stage gene delivery, thus leading to a high cell transfection efficiency.

Harnessing RNAi nanomedicine for precision therapy

Utilizing RNA interference as an innovative therapeutic strategy has an immense likelihood to generate novel concepts in precision medicine. Several clinical trials are on the way with some positive initial results. Yet, targeting of RNAi payloads such as small interfering RNAs (siRNAs), microRNA (miR) mimetic or anti-miR (antagomirs) into specific cell types remains a challenge. Major attempts are done for developing nano-sized carriers that could overcome systemic, local and cellular barriers. This progress report will focus on the recent advances in the RNAi world, detailing strategies of systemic passive tissue targeting and active cellular targeting, which is often considered as the holy grail of drug delivery.

Harnessing RNAi nanomedicine for precision therapy

Utilizing RNA interference as an innovative therapeutic strategy has an immense likelihood to generate novel concepts in precision medicine. Several clinical trials are on the way with some positive initial results. Yet, targeting of RNAi payloads such as small interfering RNAs (siRNAs), microRNA (miR) mimetic or anti-miR (antagomirs) into specific cell types remains a challenge. Major attempts are done for developing nano-sized carriers that could overcome systemic, local and cellular barriers. This progress report will focus on the recent advances in the RNAi world, detailing strategies of systemic passive tissue targeting and active cellular targeting, which is often considered as the holy grail of drug delivery.

One-step sonochemical preparation of redox-responsive nanocapsules for glutathione mediated RNA release

A simple and reproducible sonochemical method is described to achieve redox-responsive nanocapsules based on intracellular glutathione levels for enhanced and sustained RNA delivery.

Lipid-based nanoparticles in the systemic delivery of siRNA

RNAi therapeutics are believed to be the future of personalized medicine and have shown promise in early clinical trials. However, many physiological barriers exist in the systemic delivery of siRNAs to the cytoplasm of targeted cells to perform their function. To overcome these barriers, many siRNA delivery systems have been developed. Among these, lipid-based nanoparticles have great potential owing to their biocompatibility and low toxicity in comparison with inorganic nanoparticles and viral systems. This review discusses the hurdles of systemic siRNA delivery and highlights the recent progress made in lipid-based nanoparticles, which are categorized based on their key lipid components, including cationic lipid, lipoprotein, lipidoid, neutral lipid and anionic lipid-based nanoparticles. It is expected that these lipid nanoparticle-based siRNA delivery systems will have an enabling role for personalized cancer medicine, where siRNA delivery will join forces with genetic profiling of individual patients to achieve the best treatment outcome.

Design of siRNA Therapeutics from the Molecular Scale

While protein-based therapeutics is well-established in the market, development of nucleic acid therapeutics has lagged. Short interfering RNAs (siRNAs) represent an exciting new direction for the pharmaceutical industry. These small, chemically synthesized RNAs can knock down the expression of target genes through the use of a native eukaryotic pathway called RNA interference (RNAi). Though siRNAs are routinely used in research studies of eukaryotic biological processes, transitioning the technology to the clinic has proven challenging. Early efforts to design an siRNA therapeutic have demonstrated the difficulties in generating a highly-active siRNA with good specificity and a delivery vehicle that can protect the siRNA as it is transported to a specific tissue. In this review article, we discuss design considerations for siRNA therapeutics, identifying criteria for choosing therapeutic targets, producing highly-active siRNA sequences, and designing an optimized delivery vehicle. Taken together, these design considerations provide logical guidelines for generating novel siRNA therapeutics.

Advances in Lipid Nanoparticles for siRNA Delivery

Technological advances in both siRNA (small interfering RNA) and whole genome sequencing have demonstrated great potential in translating genetic information into siRNA-based drugs to halt the synthesis of most disease-causing proteins. Despite its powerful promises as a drug, siRNA requires a sophisticated delivery vehicle because of its rapid degradation in the circulation, inefficient accumulation in target tissues and inability to cross cell membranes to access the cytoplasm where it functions. Lipid nanoparticle (LNP) containing ionizable amino lipids is the leading delivery technology for siRNA, with five products in clinical trials and more in the pipeline. Here, we focus on the technological advances behind these potent systems for siRNA-mediated gene silencing.

Can RNAi-mediated hsp90α knockdown in combination with 17-AAG be a therapy for glioma?

Heat shock protein 90 promotes tumor progression and survival and has emerged as a vital therapeutic target. Previously we reported that the combinatorial treatment of 17AAG/sihsp90α significantly downregulated Hsp90α mRNA and protein levels in Glioblastoma Multiforme (GBM). Here we investigated the ability of cell penetrating peptide (Tat_48–60 CPP)-mediated siRNA-induced hsp90α knockdown as a single agent and in combination with 17-allylamino-17-demethoxygeldanamycin (17-AAG) to induce tumor growth inhibition in GBM and whether it possessed therapeutic implications. GBM and non-tumorigenic cells exposed to siRNA and/or 17-AAG were subsequently assessed by qRT-PCR, immunofluorescence, FACS analysis, quantitative Akt, LDH leakage and cell viability assays. PAGE was performed for serum stability assessment. A combination of siRNA/17-AAG treatment significantly induced Hsp90α gene and protein knockdown by 95% and 98%, respectively, concomitant to 84% Akt kinase activity attenuation, induced cell cycle arrest and tumor-specific cytotoxicity by 88%. Efficient complex formation between CPP and siRNA exhibited improved serum stability of the siRNA with minimal intrinsic toxicity in vitro. The preliminary in vivo results showed that combination therapy induced hsp90α knockdown and attenuated Akt kinase activity in intracranial glioblastoma mouse models. The results imply that RNAi-mediated hsp90α knockdown increases 17-AAG treatment efficacy in GBM. In addition, the cytotoxic response observed was the consequence of downregulation of hsp90α gene expression, reduced Akt kinase activity and S-G2/M cell cycle arrest. These results are novel and highlight the ability of Tat to efficiently deliver siRNA in GBM and suggest that the dual inhibition of Hsp90 has therapeutic potentials.

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17-AAG–siRNA dual treatment exhibits significant anti-cancer activity in GBM.

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Combination therapy induced Hsp90α gene/protein knockdown causing Akt inactivation.

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Hsp90α inhibition causes S-G2/M cell cycle arrest and GBM-specific cytotoxicity.

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Efficient siRNA/CPP interaction improves serum stability of siRNA.

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RNAi-mediated hsp90α knockdown increases GBM sensitivity to 17-AAG.

eIF3c: a potential therapeutic target for cancer

Cancer cells are rapidly evolving due to their unstable genome, which contributes to the development of new cancer clones with different gene expression profile (GEP). Manipulating the expression of the genes vital for the progression of the disease is essential to overcome its heterogeneity. However, targeting overexpressed genes, retrieved from GEP analysis, would be efficient for a specific kind of a malignancy. Alternatively, manipulating the expression of genes that are part of a fundamental mechanism in the cell would be effective against a wide range of malignancies. To test this hypothesis we characterized, using RNAi approaches, the therapeutic potential of the housekeeping eIF3c gene in five different cancer cell lines NCI-ADR/RES (NAR), HeLa, MCF7, HCT116 and B16F10. eIF3c is one of the core subunit of the eukaryote translation initiation factor (eIF) 3 complex, which has a crucial role in the translation initiation process. In this study, we demonstrated that eIF3c is vital to translation initiation in vivo, as its downregulation decreases the global protein synthesis and causes a polysome run-off. In addition, reducing the expression of eIF3c mediates G0/G1 or G2/M arrest in a tissue dependent manner, which leads to a reduction in cell proliferation and eventually to cell death. Moreover, we demonstrated the efficiency of the hyaluronan (HA)-coated lipid-based nanoparticles (LNPs) platform to deliver eIF3c-siRNAs to mouse melanoma cells. Taking together, our results emphasize the importance of seeking ubiquitously expressed housekeeping genes such as eIF3c rather than tumor associated overexpressed genes as therapeutic targets for the heterogeneous malignancies.

Harnessing nanomedicine for mucosal theranostics--a silver bullet at last?

Inflammatory bowel disease (IBD) has been extensively studied in the last four decades both in animal models and humans. The treatment options remain disappointing, nonspecific, and associated with multiple systemic adverse effects. In this Perspective, we highlight issues related to emerging nanotechnologies designed particularly for treatment and disease management of IBD and discuss potential therapeutic target options with novel molecular imaging modalities.

Dendrimers for siRNA Delivery

Since the discovery of the “starburst polymer”, later renamed as dendrimer, this class of polymers has gained considerable attention for numerous biomedical applications, due mainly to the unique characteristics of this macromolecule, including its monodispersity, uniformity, and the presence of numerous functionalizable terminal groups. In recent years, dendrimers have been studied extensively for their potential application as carriers for nucleic acid therapeutics, which utilize the cationic charge of the dendrimers for effective dendrimer-nucleic acid condensation. siRNA is considered a promising, versatile tool among various RNAi-based therapeutics, which can effectively regulate gene expression if delivered successfully inside the cells. This review reports on the advancements in the development of dendrimers as siRNA carriers.