Sook Hee Ku

Targeted Nanotheranostics for Future Personalized Medicine: Recent Progress in Cancer Therapy

Recently, many theranostic nanomaterials have been developed by integrating therapeutic and diagnostic agents in a single regimen. Real-time visualization of nano drug carrier biodistributions, drug release processes and therapeutic responses can provide critical information needed for dynamically optimizing treatment operations in a personalized manner in real time. This review highlights recent progresses in the development of multifunctional nanoparticles possessing both therapeutic and imaging functionalities for cancer therapy. The advantages of using nanoparticle platforms are discussed. Examples demonstrating various combinations of imaging and therapeutic modalities are highlighted.

Chemical and structural modifications of RNAi therapeutics

Small interfering RNA (siRNA), a 21-23nt double-stranded RNA responsible for post-transcriptional gene silencing, has attracted great interests as promising genomic drugs, due to its strong ability to silence target genes in a sequence-specific manner. Despite high silencing efficiency and on-target specificity, the clinical translation of siRNA has been hindered by its inherent features: poor intracellular delivery, limited blood stability, unpredictable immune responses and unwanted off-targeting effects. To overcome these hindrances, researchers have made various advances to modify siRNA itself and to improve its delivery. In this review paper, first we briefly discuss the innate properties and delivery barriers of siRNA. Then, we describe recent progress in (1) chemically and structurally modified siRNAs to solve their intrinsic problems and (2) siRNA delivery formulations including siRNA conjugates, polymerized siRNA, and nucleic acid-based nanoparticles to improve in vivo delivery.

Tumor-targeting multifunctional nanoparticles for siRNA delivery: recent advances in cancer therapy.

RNA interference (RNAi) is a naturally occurring regulatory process that controls posttranscriptional gene expression. Small interfering RNA (siRNA), a common form of RNAi-based therapeutics, offers new opportunities for cancer therapy via silencing specific genes, which are associated to cancer progress. However, clinical applications of RNAi-based therapy are still limited due to the easy degradation of siRNA during body circulation and the difficulty in the delivery of siRNA to desired tissues and cells. Thus, there have been many efforts to develop efficient siRNA delivery systems, which protect siRNA from serum nucleases and deliver siRNA to the intracellular region of target cells. Here, the recent advances in siRNA nanocarriers, which possess tumor-targeting ability are reviewed; various nanoparticle systems and their antitumor effects are summarized. The development of multifunctional nanocarriers for theranostics or combinatorial therapy is also discussed.

Co-delivery of VEGF and Bcl-2 dual-targeted siRNA polymer using a single nanoparticle for synergistic anti-cancer effects in vivo

Cancer is a multifactorial disease which involves complex genetic mutation and dysregulation. Combinatorial RNAi technology and concurrent multiple gene silencing are expected to provide advanced strategies for effective cancer therapy, but a safe and effective carrier system is a prerequisite to successful siRNA delivery in vivo. We previously developed an effective tumor-targeting siRNA delivery system for in vivo application. In response to the success of this development, herein we present a dual-gene targeted siRNA and its delivery system, to achieve synergistic effects in cancer therapy. Two different sequences of siRNA were chemically modified to be randomly copolymerized in a single backbone of siRNA polymer (Dual-poly-siRNA), and the resulting Dual-poly-siRNA was incorporated into tumor-homing glycol chitosan nanoparticles. Based on the stability in serum and delivery in a tumor-targeted manner, intravenously administered Dual-poly-siRNA carrying glycol chitosan nanoparticles (Dual-NP) demonstrated successful dual-gene silencing in tumors. Notably, co-delivery of VEGF and Bcl-2 targeting siRNA led to more effective cancer therapy for convenient application.

Tumor-targeting glycol chitosan nanoparticles as a platform delivery carrier in cancer diagnosis and therapy.

A natural based polymer, chitosan has received widespread attention in drug delivery systems due to its valuable physicochemical and biological characteristics. In particular, hydrophobic moiety-conjugated glycol chitosan can form amphiphilic self-assembled glycol chitosan nanoparticles (GCNPs) and simultaneously encapsulate hydrophobic drug molecules inside their hydrophobic core. This GCNP-based drug delivery systems exhibit excellent tumor-homing efficacy, attributed to the long blood circulation and the enhanced permeability and retention effect; this tumor-targeting drug delivery results in improved therapeutic efficiency. In this review, we describe the requisite properties of GCNPs for cancer therapy as well as imaging for diagnosis, such as their basic characteristics, in vitro delivery efficiency and in vivo tumor-targeting ability.

RAGE siRNA-mediated gene silencing provides cardioprotection against ventricular arrhythmias in acute ischemia and reperfusion.

Expression of receptor for advanced glycation end-products (RAGE) is suggested to play a crucial role in mediating cardiac ischemia/reperfusion (IR) injury, and the blockade of RAGE signaling has been considered as a potential therapeutic strategy for the treatment of IR-induced cardiac damage. In this study, we primarily investigated the effects of RAGE suppression particularly on IR-induced ventricular arrhythmia. To inhibit the IR-induced upregulation of RAGE, siRNA targeting RAGE (siRAGE) was delivered to myocardium by using deoxycholic acid-modified polyethylenimine (PEI-DA) as a non-viral gene carrier. The resultant PEI-DA/siRAGE nanocomplexes successfully silenced the expression of RAGE and attenuated the inflammation and apoptosis in the ischemic-reperfused myocardium. According to our results, the electrophysiological properties (e.g., action potential propagation, action potential duration, and conduction velocity), disrupted by IR injury, were restored to normal level and the induction of ventricular tachycardia was abolished by RAGE silencing. We further found that RAGE suppression led to the activation of Wnt signaling, followed by the expression of gap junction protein, connexin43. Thus it could be concluded that successful siRAGE delivery is protective against IR-induced ventricular arrhythmia.

Deoxycholic acid-modified polyethylenimine based nanocarriers for RAGE siRNA therapy in acute myocardial infarction.

The activation of receptor for advanced glycation end products (RAGE) signaling is mainly associated with myocardial ischemia/reperfusion injury. Thus the blockade of RAGE-ligands axis can be considered as a potential therapeutic strategy to protect myocardial infarction after ischemia/reperfusion injury. Herein, we strengthened the cardioprotective effect with combinatorial treatment of soluble RAGE (sRAGE) and RAGE siRNA (siRAGE) causing more effective suppression of RAGE-mediated signaling transduction. For pharmacological blockade of RAGE, sRAGE, the extracellular ligand binding domain of RAGE, acts as a pharmacological ligand decoy and inhibits the interaction between RAGE and its ligands. For genetic deletion of RAGE, siRAGE suppresses the expression of RAGE by participating in RNA interference mechanism. Therefore, we combined these two RAGE blockade/deletion strategies and investigated the therapeutic effects on rat ischemic and reperfused myocardium. According to our results, based on RAGE expression level analysis and infarct size/fibrosis measurement, co-treatment of sRAGE and siRAGE exhibited synergic cardioprotective effects; thus the newly designed regimen can be considered as a promising candidate for the treatment of myocardial infarction.

Simultaneous regulation of apoptotic gene silencing and angiogenic gene expression for myocardial infarction therapy: Single-carrier delivery of SHP-1 siRNA and VEGF-expressing pDNA

Gene therapy is aimed at selectively knocking up or knocking down the target genes involved in the development of diseases. In many human diseases, dysregulation of disease-associated genes is occurred concurrently: some genes are abnormally turned up and some are turned down. In the field of non-viral gene therapy, plasmid DNA (pDNA) and small interfering RNA (siRNA) are suggested as representative regulation tools for activating and silencing the expression of genes of interest, representatively. Herein, we simultaneously loaded both siRNA (Src homology region 2 domain-containing tyrosine phosphatase-1 siRNA, siSHP-1) for anti-apoptosis and pDNA (hypoxia-inducible vascular endothelial growth factor expression vector, pHI-VEGF) for angiogenesis in a single polymeric nanocarrier and used to synergistically attenuate ischemia-reperfusion (IR)-induced myocardial infarction, which is mainly caused by dysregulating of cardiac apoptosis and angiogenesis. For dual-modality cardiac gene delivery, siSHP-1 and pHI-VEGF were sequentially incorporated into a stable nanocomplex by using deoxycholic acid-modified polyethylenimine (DA-PEI). The resulting DA-PEI/siSHP-1/pHI-VEGF complexes exhibited the high structural stability against polyanion competition and the improved resistance to digestion by nucleases. The cardiac administration of DA-PEI/siSHP-1/pHI-VEGF reduced cardiomyocyte apoptosis and enhanced cardiac microvessel formation, thereby reducing infarct size in rat ischemia-reperfusion model. The simultaneous anti-apoptotic and angiogenic gene therapies synergized the cardioprotective effects of each strategy; thus our dual-modal single-carrier gene delivery system can be considered as a promising candidate for treating ischemic heart diseases.

Cross-linked iron oxide nanoparticles for therapeutic engineering and in vivo monitoring of mesenchymal stem cells in cerebral ischemia model.

Poly(ethylene glycol)-coated cross-linked iron oxide nanoparticles (PCIONs) are developed for therapeutic engineering of mesenchymal stem cells (MSCs) and their monitoring via magnetic resonance (MR) imaging at a time. PCIONs successfully combine with plasmid DNA (pDNA) via ionic interaction. Accordingly, PCION/pDNA complexes mediate superior translocations of vascular endothelial growth factor (VEGF) pDNA into intracellular regions of MSCs under external magnetic field, which significantly elevate production of VEGF from MSCs. Genetically engineered MSCs are also clearly visualized via MR imaging after administration to rat cerebrovascular ischemia models, which enable tracking of MSCs migration from injected sites to injured ischemic area.

Enhanced Cytoplasmic Delivery of RAGE siRNA Using Bioreducible Polyethylenimine-based Nanocarriers for Myocardial Gene Therapy

This study aims to develop bioreducible polyethylenimine (rPEI)/siRNA polyplexes with high stability, high transfection efficiency, and low cytotoxicity for efficient cytoplasmic siRNA delivery. rPEI successfully incorporated siRNA into stable and compact nanocomplexes, and the disulfide linkages in rPEI/siRNA were cleaved under reductive environments, resulting in efficient intracellular translocation and siRNA release. In this study, receptor for advanced glycation end-products (RAGE) was selected as a therapeutic target gene because it is associated with inflammatory responses in ischemia/reperfusion injury. rPEI/siRAGE exhibited high target gene silencing and low cytotoxicity in cardiomyocytes, and the treatment of rPEI/siRAGE reduced the myocardial infarction size.