Highly stable polyglutamate derivatives/siRNA polyplex efficiently down-relegate survivin expression and augment the efficacy of cisplatin

The Small RNA Landscape in NSCLC: Current Therapeutic Applications and Progresses

Non-small-cell lung cancer (NSCLC) is the second most diagnosed type of malignancy and the first cause of cancer death worldwide. Despite recent advances, the treatment of choice for NSCLC patients remains to be chemotherapy, often showing very limited effectiveness with the frequent occurrence of drug-resistant phenotype and the lack of selectivity for tumor cells. Therefore, new effective and targeted therapeutics are needed. In this context, short RNA-based therapeutics, including Antisense Oligonucleotides (ASOs), microRNAs (miRNAs), short interfering (siRNA) and aptamers, represent a promising class of molecules. ASOs, miRNAs and siRNAs act by targeting and inhibiting specific mRNAs, thus showing an improved specificity compared to traditional anti-cancer drugs. Nucleic acid aptamers target and inhibit specific cancer-associated proteins, such as "nucleic acid antibodies". Aptamers are also able of receptor-mediated cell internalization, and therefore, they can be used as carriers of secondary agents giving the possibility of producing very highly specific and effective therapeutics. This review provides an overview of the proposed applications of small RNAs for NSCLC treatment, highlighting their advantageous features and recent advancements in the field.

Current Advancements in Self-assembling Nanocarriers-Based siRNA Delivery for Cancer Therapy

Different therapeutic practices for treating cancers have significantly evolved to compensate and/or overcome the failures in conventional methodologies. The demonstrated potentiality in completely inhibiting the tumors and in preventing cancer relapse has made nucleic acids therapy (NAT)/gene therapy as an attractive practice. This has been made possible because NAT-based cancer treatments are highly focused on the fundamental mechanisms - i.e., silencing the expression of oncogenic genes responsible for producing abnormal proteins (via messenger RNAs (mRNAs)). However, the future clinical translation of NAT is majorly dependent upon the effective delivery of the exogenous nucleic acids (especially RNAs - e.g., short interfering RNAs (siRNAs) - herein called biological drugs). Moreover, nano-based vehicles (i.e., nanocarriers) are involved in delivering them to prevent degradation and undesired bioaccumulation while enhancing the stability of siRNAs. Herein, we have initially discussed about three major types of self-assembling nanocarriers (liposomes, polymeric nanoparticles and exosomes). Later, we have majorly reviewed recent developments in non-targeted/targeted nanocarriers for delivery of biological drugs (individual/dual) to silence the most important genes/mRNAs accountable for inducing protein abnormality. These proteins include polo-like kinase 1 (PLK1), survivin, vascular endothelial growth factor (VEGF), B-cell lymphoma/leukaemia-2 (Bcl-2) and multi-drug resistance (MDR). Besides, the consequent therapeutic effects on cancer growth, invasion and/or metastasis have also been discussed. Finally, we have comprehensively reviewed the improvements achieved in the cutting-edge cancer therapeutics while delivering siRNAs in combination with clinically approved chemotherapeutic drugs.

Therapeutic Potential of Glutamine Pathway in Lung Cancer

Cancer cells tend to obtain the substances needed for their development depending on altering metabolic characteristics. Among the reorganized metabolic pathways, Glutamine pathway, reprogrammed to be involved in the physiological process including energy supply, biosynthesis and redox homeostasis, occupies an irreplaceable role in tumor cells and has become a hot topic in recent years. Lung cancer currently maintains a high morbidity and mortality rate among all types of tumors and has been a health challenge that researchers have longed to overcome. Therefore, this study aimed to clarify the essential role of glutamine pathway played in the metabolism of lung cancer and its potential therapeutic value in the interventions of lung cancer.

Employing siRNA tool and its delivery platforms in suppressing cisplatin resistance: Approaching to a new era of cancer chemotherapy

Although chemotherapy is a first option in treatment of cancer patients, drug resistance has led to its failure, requiring strategies to overcome it. Cancer cells are capable of switching among molecular pathways to ensure their proliferation and metastasis, leading to their resistance to chemotherapy. The molecular pathways and mechanisms that are responsible for cancer progression and growth, can be negatively affected for providing chemosensitivity. Small interfering RNA (siRNA) is a powerful tool extensively applied in cancer therapy in both pre-clinical (in vitro and in vivo) and clinical studies because of its potential in suppressing tumor-promoting factors. As such oncogene pathways account for cisplatin (CP) resistance, their targeting by siRNA plays an important role in reversing chemoresistance. In the present review, application of siRNA for suppressing CP resistance is discussed. The first priority of using siRNA is sensitizing cancer cells to CP-mediated apoptosis via down-regulating survivin, ATG7, Bcl-2, Bcl-xl, and XIAP. The cancer stem cell properties and related molecular pathways including ID1, Oct-4 and nanog are inhibited by siRNA in CP sensitivity. Cell cycle arrest and enhanced accumulation of CP in cancer cells can be obtained using siRNA. In overcoming siRNA challenges such as off-targeting feature and degradation, carriers including nanoparticles and biological carriers have been applied. These carriers are important in enhancing cellular accumulation of siRNA, elevating gene silencing efficacy and reversing CP resistance.

RNA-based therapies: A cog in the wheel of lung cancer defense

Lung cancer (LC) is a heterogeneous disease consisting mainly of two subtypes, non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), and remains the leading cause of death worldwide. Despite recent advances in therapies, the overall 5-year survival rate of LC remains less than 20%. The efficacy of current therapeutic approaches is compromised by inherent or acquired drug-resistance and severe off-target effects. Therefore, the identification and development of innovative and effective therapeutic approaches are critically desired for LC. The development of RNA-mediated gene inhibition technologies was a turning point in the field of RNA biology. The critical regulatory role of different RNAs in multiple cancer pathways makes them a rich source of targets and innovative tools for developing anticancer therapies. The identification of antisense sequences, short interfering RNAs (siRNAs), microRNAs (miRNAs or miRs), anti-miRs, and mRNA-based platforms holds great promise in preclinical and early clinical evaluation against LC. In the last decade, RNA-based therapies have substantially expanded and tested in clinical trials for multiple malignancies, including LC. This article describes the current understanding of various aspects of RNA-based therapeutics, including modern platforms, modifications, and combinations with chemo-/immunotherapies that have translational potential for LC therapies.

The pH-triggered polyglutamate brush co-delivery of MDR1 and survivin-targeting siRNAs efficiently overcomes multi-drug resistance of NSCLC

Multi-drug resistance (MDR) is one of the major challenges in the successful chemotherapy of non-small cell lung cancer (NSCLC). Although RNA interference (RNAi) has been widely used to silence resistance-related genes, the effect remains unsatisfactory. In this study, we attempted to overcome MDR of NSCLC by simultaneously interfering with two RNAs that have different functions. A new pH-triggered polyglutamate brush polymer dimethylmaleic anhydride-poly(ethyleneglycol) monomethyl ether-b-polyglutamate-g-spermine (DMA-mPEG-b-PG-g-spermine, DPPGS) was designed and synthesized. The DPPGS/small interfering RNA (siRNA) complex nanoparticles (DPPGSN) were prepared. The results demonstrated that DPPGSN could be transformed from a negatively charged form into a positively charged form in the slightly acidic tumor extracellular environment. The siRNA targeting MDR1 mRNA (siMDR1) and siRNA targeting survivin mRNA (siSurvivin) could be efficiently co-delivered by DPPGS to simultaneously interfere with two genes (p < 0.01). Furthermore, DPPGS co-delivery of siMDR1 and siSurvivin lowered the IC₅₀ value of cisplatin (DDP) in A549/DDP (p < 0.01) cells and increased the apoptosis rate of the cells (p < 0.01). Therefore, co-delivery of siMDR1 and siSurvivin using DPPGS would be a promising approach for overcoming MDR of NSCLC.

Poly(L-Glutamic Acid)-Based Brush Copolymers: Fabrication, Self-assembly, and Evaluation as Efficient Nanocarriers for Cationic Protein Drug Delivery

Protein drugs were considered to be the first choice to treat many human diseases, but their clinical application was usually limited by their short half-life and lack of validated targeted therapy. Here, a series of folate-functionalized poly(ethylene glycol)-b-(poly(2-aminoethyl-L-glutamate)-g-poly(L-glutamic acid))s (FA-PEG-b-(PELG-g-PLGA)s) were designed as tumor-targeted carriers for cationic protein delivery. Compared with traditional copolymers consisting of PEG and linear charged hydrophilic blocks, FA-PEG-b-(PELG-g-PLGA) with brush-like polyelectrolyte segments were beneficial to improving their electrostatic interactions with loading protein molecules, thus increasing drug-loading stability and protecting encapsulated proteins from degradation. The designed polymer brushes could efficiently encapsulate cytochrome C (CytC), a cationic model protein, to form polyion complex (PIC) micelles with an average particle size of approximately 200 nm. An in vitro drug release study showed that the drug-loading stability of the formed PIC micelles was largely improved. The functionalization of the block copolymer carriers with a targeting folate group enhanced the tumor cell growth inhibition and total apoptotic rates induced by CytC. Our results shed light on the unique advantages of brush-like polymer carriers in delivering cationic proteins, and the poly(L-glutamic acid)-based linear-brush diblock copolymers could be applied as a versatile delivery platform for molecular targeting in cancer therapy.

Effectiveness of Small Interfering RNA Delivery via Arginine-Rich Polyethylenimine-Based Polyplex in Metastatic and Doxorubicin-Resistant Breast Cancer Cells

Poor cellular uptake, rapid degradation in the presence of serum, and inefficient transfection are some of the major barriers in achieving therapeutic efficacy of naked small interfering RNAs (siRNAs). We investigated the efficacy of the polyplex formulated using our synthesized polymer, polyethylene glycol (PEG)-modified l-arginine oligo(-alkylaminosiloxane) that is grafted with poly(ethyleneimine) (PEI) for siRNA delivery. We hypothesized that the polyplex formulated using the polymer with a balanced composition of PEI for siRNA condensation and its protection, PEG for polyplex stability and to minimize the PEI-associated toxicity, and with arginine facilitating cellular uptake would overcome the aforementioned issues with siRNA delivery. We tested our hypothesis using antiluciferase siRNA in luciferase-expressing metastatic breast cancer cells (MDA-MB-231-Luc-D3H2LN) and anti-ABCB1 siRNA against an efflux membrane protein, ABCB1, in doxorubicin (DOX)-resistant breast cancer cells (MCF-7/Adr). The results demonstrated that the polyplex at an optimal nucleotide/polymer ratio is stable in the presence of excess polyanions, has no cellular toxicity, and protects siRNA from RNase degradation. Transfection of MDA-MB-231-Luc-D3H2LN cells with antiluciferase siRNA polyplex showed almost complete knockdown of luciferase expression. In MCF-7/Adr cells, transfection with anti-ABCB1 siRNA effectively downregulated its target efflux protein, ABCB1; increased cellular uptake of DOX; and enhanced its cytotoxic effect. However, the cotreatment did not completely overcome drug resistance, suggesting that further optimization is needed and/or a mechanism(s) other than the efflux protein ABCB1 may be involved in drug resistance. In conclusion, our polyplex is effective for siRNA delivery and can be explored for different therapeutic applications.

One-pot construction of a twice-condensed pDNA polyplex system for peripheral nerve crush injury therapy

Non-viral vector gene delivery is generally limited by its potential toxicity problems, poor transfection abilities, serum stability, or relatively complex construction processes of modified polyplexes. Thus, we develop an efficient and stable polyplex system through convenient construction methods. Here, polyethyleneimine (PEI) 1.8 kDa and glutaraldehyde (GA) are used to construct a novel twice-condensed pDNA polyplex system using a one-pot construction method, including pH-responsive C[double bond, length as m-dash]N linkages by which different PEI molecules on one single polyplex can link with each other. In this system, smaller particle sizes, higher zeta potentials and better serum stabilities are achieved without PEGylation or other chemical modifications using lyophobic segments, but via pH-responsive linkages that ensure the escape of nucleic acids. This polyplex system is used to deliver the pDNA of vascular endothelial growth factor (VEGF) whose half-life period in vivo is only around 30 minutes. Compared with polyplexes prepared using PEI 25 kDa, cells and rats treated with twice-condensed VEGF pDNA polyplexes express significantly more VEGF or myelin basic protein (MBP), and this new polyplex system showed fewer adverse effects in vitro and in vivo. In addition, revascularization and neurogenesis are also discovered in the rat sciatic nerve crush injury model.

Glutamine addiction activates polyglutamine-based nanocarriers delivering therapeutic siRNAs to orthotopic lung tumor mediated by glutamine transporter SLC1A5

Many human cancer cells exhibit an oncogenetic-driven addiction to glutamine (Gln) as rapidly proliferating cancer cells consume Gln at a dramatically increased rate compared to normal cells. Tumor cells, therefore, compete with host cells for Gln, which causes Gln to flux from normal tissues to the tumor. We have developed and characterized a Gln macromolecular analog polyglutamine (PGS) for the delivery of gene regulators, such as siRNAs, in our previous works. Here, we hypothesize that PGS can utilize the Gln transporter SLC1A5 to specifically deliver therapeutic compounds to Gln-addicted cancer cells. Compared to human lung fibroblast HLF cells, cisplatin-resistant human lung adenocarcinoma A549/DDP cells significantly overexpress SLC1A5, which has a high binding affinity to PGS, as confirmed through molecular docking analysis. Due to the differences in Gln metabolism between malignant and normal cells, PGS/siRNA complexes were remarkably increased in cancer cells, especially when cells were deprived of Gln, which mirrors the conditions that are commonly found in a tumor microenvironment. Furthermore, we identified that chemical and genetic inhibition of Gln transporter SLC1A5 reduced the cellular internalization of PGS/siRNA complexes, suggesting a critical role for SLC1A5 in PGS uptake in cells. In turn, PGS upregulated SLC1A5 expression. Increased uptake of PGS complexes profoundly decreased intracellular Gln levels. Decreased Gln caused a moderate reduction in cell growth. To restore drug sensitivity and further enhance anti-tumor effects, the hybrid siRNAs anti-Survivin and anti-MDR1 (siSM), as model therapeutics, were administered through the PGS delivery system, which resulted in knockdown of Survivin and MDR1 and further sensitized cancer cells to the drug cisplatin (DDP). Since PGS complexes administered i.v. mostly accumulated in the lung parenchyma, a lung orthotopic tumor model was established to evaluate their inhibitory effects on tumors in the lungs. PGS/siSM comparably decreased the rate of tumor growth, while concurrent administration of PGS/siSM and DDP enhanced this effect and insignificantly improved life span. Consistent with our hypothesis, this study demonstrated that PGS mimicked Gln in the SLC1A5 pathway and selectively ferried therapeutics to Gln-addicted cancer cells. Our findings identified a new lung cancer targeting strategy based on Gln metabolism and can be used as a drug/gene delivery system.

A Glutamine-Rich Carrier Efficiently Delivers Anti-CD47 siRNA Driven by a "Glutamine Trap" To Inhibit Lung Cancer Cell Growth

It is not efficient enough using the current approaches for tumor-selective drug delivery based on the EPR effect and ligand-receptor interactions, and they have largely failed to translate into the clinic. Therefore, it is urgent to explore an enhanced strategy for effective delivery of anticancer agents. Clinically, many cancers require large amounts of glutamine for their continued growth and survival, resulting in circulating glutamine extraction by the tumor being much greater than that for any organs, behaving as a "glutamine trap". In the present study, we sought to elucidate whether the glutamine-trap effect could be exploited to deliver therapeutic agents to selectively kill cancer cells. Here, a macromolecular glutamine analogue, glutamine-functionalized branched polyethylenimine (GPI), was constructed as the carrier to deliver anti-CD47 siRNA for the blockage of CD47 "don't eat me" signals on cancer cells. The GPI/siRNA glutamine-rich polyplexes exhibited remarkably high levels of cellular uptake by glutamine-dependent lung cancer cells, wild-type A549 cells (A549^WT), and its cisplatin-resistant cells (A549^DDP), specifically under glutamine-depleted conditions. It was noted that the glutamine transporter ASCT2 was highly expressed both on A549^WT and A549^DDP but with almost no expression in normal human lung fibroblasts cells. Inhibition of ASCT2 significantly prevented the internalization of GPI polyplexes. These findings raised the intriguing possibility that the glutamine-rich GPI polyplexes utilize the ASCT2 pathway to selectively facilitate their cellular uptake by cancer cells. GPI further delivered anti-CD47 siRNA efficiently both in vitro and in vivo to downregulate the intratumoral mRNA and protein expression levels of CD47. CD47 functions as a "don't eat me" signal and binds to the immunoreceptor SIRPα inducing evasion of phagocytic clearance. GPI/anti-CD47 siRNA polyplexes achieved significant antitumor activities both on A549^WT and A549^DDP tumor-bearing nude mice. Notably, it had no adverse effect on CD47-expressing red blood cells and platelets, likely because of selective delivery. Therefore, the glutamine-rich carrier GPI driven by the glutamine-trap effect provides a promising new strategy for designing anticancer drug delivery systems.

A review on core-shell structured unimolecular nanoparticles for biomedical applications

Polymeric unimolecular nanoparticles (NPs) exhibiting a core-shell structure and formed by a single multi-arm molecule containing only covalent bonds have attracted increasing attention for numerous biomedical applications. This unique single-molecular architecture provides the unimolecular NP with superior stability both in vitro and in vivo, a high drug loading capacity, as well as versatile surface chemistry, thereby making it a desirable nanoplatform for therapeutic and diagnostic applications. In this review, we surveyed the architecture of various types of polymeric unimolecular NPs, including water-dispersible unimolecular micelles and water-soluble unimolecular NPs used for the delivery of hydrophobic and hydrophilic agents, respectively, as well as their diverse biomedical applications. Future opportunities and challenges of unimolecular NPs were also briefly discussed.

GABAB receptor ligand-directed trimethyl chitosan/tripolyphosphate nanoparticles and their pMDI formulation for survivin siRNA pulmonary delivery

The effect of gene silencing by survivin siRNA (siSurvivin) on the proliferation and apoptosis of lung tumor has been attracted more interest. GABA_B receptor ligand-directed nanoparticles consisting of baclofen functionalized trimethyl chitosan (Bac-TMC) as polymeric carriers, tripolyphosphate (TPP) as ionic crosslinker, and siSurvivin as therapeutic genes, were designed to enhance the survivin gene silencing. GABA_B receptor agonist baclofen (Bac) was initially introduced into TMC as a novel ligand. This Bac-TMC/TPP nanoparticles increased the uptake of survivin siRNA through the interaction with GABA_B receptor, further resulted in efficient cell apoptosis and gene silencing. For siRNA-loaded nanoparticles pulmonary delivery, mannitol was utilized for it delivery into pressurized metered dose inhalers (pMDI). The fine particle fractions of this formulation was (45.39±2.99)% indicating the appropriate deep lung deposition. These results revealed that this pMDI formulation containing Bac-TMC/TPP nanoparticles would be a promising siRNA delivery system for lung cancer treatment.

Targeted si-RNA with liposomes and exosomes (extracellular vesicles): How to unlock the potential

The concept of RNA interference therapeutics has been initiated 18 years ago, and the main bottleneck for translation of the technology into therapeutic products remains the delivery of functional RNA molecules into the cell cytoplasm. In the present review article after an introduction about the theoretical basis of RNAi therapy and the main challenges encountered for its realization, an overview of the different types of delivery systems or carriers, used as potential systems to overcome RNAi delivery issues, will be provided. Characteristic examples or results obtained with the most promising systems will be discussed. Focus will be given mostly on the applications of liposomes or other types of lipid carriers, such as exosomes, towards improved delivery of RNAi to therapeutic targets. Finally the approach of integrating the advantages of these two vesicular systems, liposomes and exosomes, as a potential solution to realize RNAi therapy, will be proposed.

Design, synthesis and evaluation of VEGF-siRNA/CRS as a novel vector for gene delivery

Small interfering RNA (siRNA) delivery is a prospective method in gene therapy, but it has application limitations such as negative charge, water solubility and high molecular weight. In this study, a safe and efficient nano-vector, CRS, was designed and synthesized to facilitate siRNA delivery. Physical and chemical properties of VEGF-siRNA/CRS were characterized by methods including scanning electron microscopy (SEM), transmission electron microscopy, zeta potential (ζ) measurement, drug-releasing rate measurement, gel electrophoresis and confocal microscopy. The biological activities were evaluated using cell viability assay, gene-silencing efficacy assay in vitro, real-time polymerase chain reaction, enzyme-linked immunosorbent assay (ELISA) and antitumor tests in vivo. The mean nanoparticle size of VEGF-siRNA/CRS was 121.4±0.3 nm with positive ζ potential of 7.69±4.47 mV. The release rate of VEGF-siRNA from VEGF-siRNA/CRS was 82.50% sustained for 48 h in Tris-ethylenediaminetetraacetic acid buffer (pH 8.0). Real-time polymerase chain reaction was used to analyze the efficiency of the transfection, and the result showed that VEGF mRNA expression had been knocked down by 82.36%. The expression of VEGF protein was also recorded to be downregulated to 14.83% using ELISA. The results of cytotoxicity measured by Cell Counting Kit-8 assay showed that VEGF-siRNA/CRS had significant inhibitory effect on HeLa cells. The results of antitumor assays indicated that VEGF-siRNA/CRS exhibited tumor cell growth inhibition in vivo. The results demonstrated that VEGF-siRNA could be delivered and transported by the designed carrier, while siRNA could be released constantly and led to an increasing gene-silencing effect against VEGF gene. In conclusion, VEGF-siRNA/CRS is a promising carrier for siRNA delivery, and further studies are warranted.