Bioreducible polyethylenimine-delivered siRNA targeting human telomerase reverse transcriptase inhibits HepG2 cell growth in vitro and in vivo

Telomerase: a nexus between cancer nanotherapy and circadian rhythm

Cancer represents a complex disease category defined by the unregulated proliferation and dissemination of anomalous cells within the human body. According to the GLOBOCAN 2020 report, the year 2020 witnessed the diagnosis of approximately 19.3 million new cases of cancer and 10.0 million individuals succumbed to the disease. A typical cell eventually becomes cancerous because of a long-term buildup of genetic instability and replicative immortality. Telomerase is a crucial regulator of cancer progression as it induces replicative immortality. In cancer cells, telomerase inhibits apoptosis by elongating the length of the telomeric region, which usually protects the genome from shortening. Many nanoparticles are documented as being available for detecting the presence of telomerase, and many were used as delivery systems to transport drugs. Furthermore, telomere homeostasis is regulated by the circadian time-keeping machinery, leading to 24-hour rhythms in telomerase activity and TERT mRNA expression in mammals. This review provides a comprehensive discussion of various kinds of nanoparticles used in telomerase detection, inhibition, and multiple drug-related pathways, as well as enlightens an imperative association between circadian rhythm and telomerase activity from the perspective of nanoparticle-based anticancer therapeutics.

PEI-based functional materials: Fabrication techniques, properties, and biomedical applications

Cationic polymers have recently attracted considerable interest as research breakthroughs for various industrial and biomedical applications. They are particularly interesting due to their highly positive charges, acceptable physicochemical properties, and ability to undergo further modifications, making them attractive candidates for biomedical applications. Polyethyleneimines (PEIs), as the most extensively utilized polymers, are one of the valuable and prominent classes of polycations. Owing to their flexible polymeric chains, broad molecular weight (MW) distribution, and repetitive structural units, their customization for functional composites is more feasible. The specific beneficial attributes of PEIs could be introduced by purposeful functionalization or modification, long service life, biocompatibility, and distinct geometry. Therefore, PEIs have significant potential in biotechnology, medicine, and bioscience. In this review, we present the advances in PEI-based nanomaterials, their transfection efficiency, and their toxicity over the past few years. Furthermore, the potential and suitability of PEIs for various applications are highlighted and discussed in detail. This review aims to inspire readers to investigate innovative approaches for the design and development of next-generation PEI-based nanomaterials possessing cutting-edge functionalities and appealing characteristics.

Virtual screening and drug repositioning of FDA-approved drugs from the ZINC database to identify the potential hTERT inhibitors

The length of the telomeres is maintained with the help of the enzyme telomerase constituting of two components, namely, a core reverse transcriptase protein (hTERT) and RNA (hTR). It serves as a significant and universal cancer target. In silico approaches play a crucial role in accelerating drug development processes, especially cancer drug repurposing is an attractive approach. The current study is aimed at the repurposing of FDA-approved drugs for their potential role as hTERT inhibitors. Accordingly, a library of 2,915 sets of FDA-approved drugs was generated from the ZINC database in order to screen for novel hTERT inhibitors; later on, these were subjected to molecular docking analysis. The top two hits, ZINC03784182 and ZINC01530694, were shortlisted for molecular dynamic simulation studies at 100 ns based on their binding scores. The RMSD, RMSF, Rg, SASA, and interaction energies were calculated for a 100-ns simulation period. The hit compounds were also analyzed for antitumor activity, and the results revealed promising cytotoxic activities of these compounds. The study has revealed the potential application of these drugs as antitumor agents that can be useful in treating cancer and can serve as lead compounds for further in vivo, in vitro, and clinical studies.

Stimulus-responsive drug/gene delivery system based on polyethylenimine cyclodextrin nanoparticles for potential cancer therapy

Combination therapy through simultaneous delivery of anti-cancer drugs and genes with nano-assembled structure has been proved to be a simple and effective approach for treating breast cancer. In this study, redox-sensitive folate-appended-polyethylenimine-β-cyclodextrin (roFPC) host-guest supramolecular nanoparticles (HGSNPs) were developed as a targeted co-delivery system of doxorubicin (Dox) and Human telomerase reverse transcriptase-small interfering RNA) hTERT siRNA) for potential cancer therapy. The nanotherapeutic system was prepared by loading adamantane-conjugated doxorubicin (Ad-Dox) into roFPC through the supramolecular assembly, followed by electrostatically-driven self-assembly between hTERT siRNA and roFPC/Ad-Dox. The roFPC' host-guest structures allow pH-dependent intracellular drug release in a sustained manner, as well as simultaneous and effective gene transfection. This co-delivery vector displayed combined anti-tumor properties of the Dox-enhanced gene transfection, good water-solubility, and biocompatibility, possesses considerably enhanced hemocompatibility, and especially targets folate receptor-positive cells only at low N/P levels to prompt effective cell apoptosis for cancer treatment.

Integrating disulfides into a polyethylenimine gene carrier selectively boosts significant transfection activity in lung tissue enabling robust IL-12 gene therapy against metastatic lung cancers

Bioreducible polyethylenimines (SSPEIs) are promising non-viral carriers for cancer gene therapy. However, the availability of significant gene transfection activity by SSPEIs remains a challenge. Herein, an essential step was taken to ascertain whether or not the disulfide bonds of SSPEIs play a critical role in promoting significant gene transfection activity in different tissues. Initially, a disulfide-linked linear polyethylenimine (denoted as SSLPEI) consisting of one 5.0 kDa LPEI main chain and three disulfide-linked 5.7 kDa LPEI grafts was designed and prepared to possess similar molecular weight with commercialized 25 kDa LPEI as a positive control. The SSLPEI could induce superior in vitro transfection activity in different cells to the LPEI control as well as low cytotoxicity. Notably, such enhanced in vitro transfection effect by the SSLPEI was more marked in type-II alveolar epithelial cells compared to different cancer cells. In a Balb/c nude mouse model bearing SKOV-3 tumor, the SSLPEI caused parallel level of transgene expression with the LPEI control in the tumor but significantly higher level in the mouse lung. Furthermore, the SSLPEI and LPEI groups afforded an identical antitumor efficacy against the SKOV-3 tumor via intravenous delivery of a shRNA for silencing VEGF expression in the tumor. However, via intravenous delivery of an interleukin-12 (IL-12) gene into metastatic lung cancers in a C57BL/6 mouse model, the SSLPEI group exerted markedly higher IL-12 expression level in the mouse lung and peripheral blood as compared to the LPEI group, thereby boosting IL-12 immunotherapy against the lung metastasis with longer medium survival time. The results of this work elicit that the disulfide bonds of SSPEIs play a pivotal role in enhancing gene transfection activity selectively in the lung tissue rather than solid tumor, enabling high translational potential of SSPEIs for non-viral gene therapy against metastatic lung cancers.

piRNA-30473 contributes to tumorigenesis and poor prognosis by regulating m6A RNA methylation in DLBCL

The initiation and progression of diffuse large B-cell lymphoma (DLBCL) is governed by genetic and epigenetic aberrations. As the most abundant eukaryotic messenger RNA (mRNA) modification, N6-methyladenosine (m6A) is known to influence various fundamental bioprocesses by regulating the target gene; however, the function of m6A modifications in DLBCL is unclear. PIWI-interacting RNAs (piRNAs) have been indicated to be epigenetic effectors in cancer. Here, we show that high expression of piRNA-30473 supports the aggressive phenotype of DLBCL, and piRNA-30473 depletion decreases proliferation and induces cell cycle arrest in DLBCL cells. In xenograft DLBCL models, piRNA-30473 inhibition reduces tumor growth. Moreover, piRNA-30473 is significantly associated with overall survival in a univariate analysis and is statistically significant after adjusting for the National Comprehensive Cancer Network-International Prognostic Index in the multivariate analysis. Additional studies demonstrate that piRNA-30473 exerts its oncogenic role through a mechanism involving the upregulation of WTAP, an m6A mRNA methylase, and thus enhances the global m6A level. Integrating transcriptome and m6A-sequencing analyses reveals that WTAP increases the expression of its critical target gene, hexokinase 2 (HK2), by enhancing the HK2 m6A level, thereby promoting the progression of DLBCL. Together, the piRNA-30473/WTAP/HK2 axis contributes to tumorigenesis by regulating m6A RNA methylation in DLBCL. Furthermore, by comprehensively analyzing our clinical data and data sets, we discover that the m6A regulatory genes piRNA-30473 and WTAP improve survival prediction in DLBCL patients. Our study highlights the functional importance of the m6A modification in DLBCL and might assist in the development of a prognostic stratification and therapeutic approach for DLBCL.

Nanoparticle-mediated convection-enhanced delivery of a DNA intercalator to gliomas circumvents temozolomide resistance

In patients with glioblastoma, resistance to the chemotherapeutic temozolomide (TMZ) limits any survival benefits conferred by the drug. Here we show that the convection-enhanced delivery of nanoparticles containing disulfide bonds (which are cleaved in the reductive environment of the tumour) and encapsulating an oxaliplatin prodrug and a cationic DNA intercalator inhibit the growth of TMZ-resistant cells from patient-derived xenografts, and hinder the progression of TMZ-resistant human glioblastoma tumours in mice without causing any detectable toxicity. Genome-wide RNA profiling and metabolomic analyses of a glioma cell line treated with the cationic intercalator or with TMZ showed substantial differences in the signalling and metabolic pathways altered by each drug. Our findings suggest that the combination of anticancer drugs with distinct mechanisms of action with selective drug release and convection-enhanced delivery may represent a translational strategy for the treatment of TMZ-resistant gliomas.

A tumor-activatable peptide supramolecular nanoplatform for the delivery of dual-gene targeted siRNAs for drug-resistant cancer treatment

Combinatorial short interference RNA (siRNA) technology for the silencing of multiple genes is expected to provide an effective therapeutic approach for cancer with complex genetic mutation and dysregulation. Herein we present a tumor-activatable supramolecular nanoplatform for the delivery of siRNAs to target telomerase and telomeres for paclitaxel-resistant non-small-cell lung cancer (A549/PTX) treatment. Two different sequences of siRNA are incorporated in a single nanoparticle, which is obtained by self-assembly from a peptide dendrimer. The siRNA stability is improved by the nanoparticle in the presence of serum compared to free siRNA, and these siRNAs are protected from RNA enzyme degradation. In the tumor extracellular acid environment, the PEG corona of the nanoparticle is removed to promote the internalization of siRNAs into tumor cells. The disulfide linkages between the nanoparticle and siRNAs are cleared in the reductive environment of the tumor cells, and the siRNAs are released in the cytoplasm. In vitro experiments show that the gene expression of hTERT and TRF2 at the mRNA and protein levels of A549/PTX tumor cells is down-regulated, which results in cooperative restraining proliferation and invasion of A549/PTX tumor cells. For the tumor cell-targeting function of the MUC1 aptamer and the EPR effect, sufficient tumor accumulation of nanoparticles was observed. Meanwhile, a shift of negative surface charge of nanoparticles to positive charge in the tumor extracellular microenvironment enhances deep penetration of siRNA-incorporating nanoparticles into tumor tissues. In vivo animal studies support that successful down-regulation of hTERT and TRF2 gene expression achieves effective inhibition of the growth and neovascularization of drug-resistant tumor cells. This work has provided a new avenue for drug-resistant cancer treatment by designing and synthesizing a tumor-activatable nanoplatform to achieve the delivery of dual-gene targeted combinatorial siRNAs.

Disulfide Bridging Strategies in Viral and Nonviral Platforms for Nucleic Acid Delivery

Self-assembled nanostructures that are sensitive to environmental stimuli are promising nanomaterials for drug delivery. In this class, disulfide-containing redox-sensitive strategies have gained enormous attention because of their wide applicability and simplicity of nanoparticle design. In the context of nucleic acid delivery, numerous disulfide-based materials have been designed by relying on covalent or noncovalent interactions. In this review, we highlight major advances in the design of disulfide-containing materials for nucleic acid encapsulation, including covalent nucleic acid conjugates, viral vectors or virus-like particles, dendrimers, peptides, polymers, lipids, hydrogels, inorganic nanoparticles, and nucleic acid nanostructures. Our discussion will focus on the context of the design of materials and their impact on addressing the current shortcomings in the intracellular delivery of nucleic acids.

Silencing of BCSG1 with specific siRNA via nanocarriers for breast cancer treatment

Breast cancer is the most common cancer diagnosed in women worldwide. The current treatments for breast cancer, including surgery, radiotherapy and chemotherapy aim to destroy cancer cells, whereas they also cause damage to normal tissues and cells. Thus, an effective, safe and specific breast cancer treatment is urgently needed. The breast cancer-specific gene 1 (BCSG1) has been shown to be specific for the development of breast cancer and is a target for breast cancer diagnosis and treatment. It is expected to silence the expression of BCSG1 at the gene level for the purpose of treating breast cancer. The effect of RNAi technology on silencing target genes is comparable to gene knockout and has been widely used in animal experiments and plant genetic research. In the field of cancer therapy, numerous investigators have used siRNAs to specifically inhibit target genes, demonstrating that siRNAs can treat cancers at the molecular level. However, the delivery of siRNAs into humans needs to overcome multiple physiological barriers, limiting the clinical applications of siRNAs. This review focuses on the application of BCSG1 gene, siRNAs in cancer treatments, and the nanocarrier delivery system of siRNAs. The potential application and research value of BCSG1-specific siRNA in the treatment of breast cancer are discussed.

Recent advances of nanomedicines for liver cancer therapy

This review highlights recent advancements in nanomedicines for liver cancer therapy.

Current Transport Systems and Clinical Applications for Small Interfering RNA (siRNA) Drugs

Small interfering RNAs (siRNAs) are an attractive new agent with potential as a therapeutic tool because of its ability to inhibit specific genes for many conditions, including viral infections and cancers. However, despite this potential, many challenges remain, including off-target effects, difficulties with delivery, immune responses, and toxicity. Traditional genetic vectors do not guarantee that siRNAs will silence genes in vivo. Rational design strategies, such as chemical modification, viral vectors, and non-viral vectors, including cationic liposomes, polymers, nanocarriers, and bioconjugated siRNAs, provide important opportunities to overcome these challenges. We summarize the results of research into vector delivery of siRNAs as a therapeutic agent from their design to clinical trials in ophthalmic diseases, cancers, respiratory diseases, and liver virus infections. Finally, we discuss the current state of siRNA delivery methods and the need for greater understanding of the requirements.

Thiol redox-sensitive cationic polymers for dual delivery of drug and gene

Recently greater emphasis has been given to combination therapy for generating synergistic effects of treating cancer. Recent studies on thiol-sensitive nanocarriers for the delivery of drug or gene have shown promising results. In this review, we will examine the rationale and advantage in using nanocarriers for the combined delivery of different anticancer drugs and biologics. Here, we also discuss the role of nanocarriers, particularly redox-sensitive polymers in evading or inhibiting the efflux pump in cancer and how they modulate the sensitivity of cancer cells. The review aims to provide a good understanding of the new pattern of cancer treatment and key concerns for designing nanomedicine of synergistic combinations for cancer therapy.

Complex of TNF-α and Modified Fe3O4 Nanoparticles Suppresses Tumor Growth by Magnetic Induction Hyperthermia

BACKGROUND

Magnetic nanoparticles are increasingly applied in clinical area for drug delivery, also in magnetic induction hyperthermia (MIH), and so on. The present research would prepare appropriately modified superparamagnetic iron oxide nanoparticles (SPIONs) to conduct MIH and transfect the anticancer cytokine TNF-α into cells.

MATERIALS AND METHODS

The SPIONs were surface-modified by 3-aminopropyltriethoxysilane (APTS) and/or protamine sulfate (PRO). The combined MIH using SPIONs and gene therapy were applied to treat Hep G2 cells and tumor model transplanted in nude mice.

RESULTS

The PRO-SPIONs (the surfaces were sequentially modified by APTS and PRO) showed high transfection efficiency for TNF-α gene with no obvious cytotoxicity. It also exhibited great temperature rising performance under alternating current magnetic field. The combined MIH and gene therapy using PRO-SPIONs/TNF-α complex could reduce cell variability of Hep G2 cells and tumor size transplanted in nude mice.

CONCLUSIONS

The PRO-SPIONs efficiently transfect the TNF-α gene into Hep G2 cells. Cells expressed more TNF-α when they were exposed to alternating current magnetic field only once. Combined MIH and gene therapy for treatment in vivo exhibited better effects than MIH or gene therapy alone. The combined MIH and gene therapy is promising in liver cancer treatment.

Gold nanorod-assembled ZnGa2O4:Cr nanofibers for LED-amplified gene silencing in cancer cells

Nanoparticles are now commonly used as non-viral gene vectors for RNA interference (RNAi) in cancer therapy but suffer from low targeting efficiency in situ. Meanwhile, localized drug delivery systems do not offer the effective capability for intracellular gene transportation. We describe here the design and synthesis of a localized therapeutic system, consisting of gold nanorods (Au NRs) loaded with hTERT siRNA assembled on the surface of ZnGa2O4:Cr (ZGOC) nanofibers. This composite system offers the potential for a LED-induced mild photothermal effect which enhances the phagocytosis of Au NRs carrying siRNA and the subsequent release of siRNA in the cytoplasm. Both phenomena amplify the gene silencing effect and consequently offer the potential for a superior therapeutic outcome.

Telomerase reverse transcriptase suppression inhibits cell proliferation and promotes cell apoptosis in hepatocellular cancer

We aimed to investigate the role of telomerase reverse transcriptase (TERT) in hepatocellular cancer (HCC) cells. R software was used for differential expressed gene analysis. Western blot and quantitative real time polymerase chain reaction (qRT-PCR), respectively, were used to detect protein expression and mRNA level of TERT in tumor cell lines. Real-time quantitative telomeric repeat amplification protocol assay, MTT assay, colony formation assay, and flow cytometry (FCM) assay were used to analyze the telomerase activity, viability, proliferation, cell cycle progression and apoptosis of HCC cells. The proliferation ratio of HCC cells transfected with TERT-siRNA was significantly decreased compared with control group. Plate clone results suggested that the number of colonies also decreased in TERT-siRNA group. FCM results showed that more cells were arrested in G0/G1 phase and apoptosis rate increased in TERT-siRNA group compared with control group. TERT suppression inhibited cell proliferation but promoted cell cycle arrest and cell apoptosis. © 2018 IUBMB Life, 70(7):642-648, 2018.

hTERT gene knockdown enhances response to radio- and chemotherapy in head and neck cancer cell lines through a DNA damage pathway modification

The aim of the study was to analyze the effect of hTERT gene knockdown in HNSCC cells by using novel in vitro models of head and neck cancer (HNSCC), as well as improving its personalized therapy. To obtain the most efficient knockdown siRNA, shRNA-bearing lentiviral vectors were used. The efficiency of hTERT silencing was verified with qPCR, Western blot, and immunofluorescence staining. Subsequently, the type of cell death and DNA repair mechanism induction after hTERT knockdown was assessed with the same methods, followed by flow cytometry. The effect of a combined treatment with hTERT gene knockdown on Double-Strand Breaks levels was also evaluated by flow cytometry. Results showed that the designed siRNAs and shRNAs were effective in hTERT knockdown in HNSCC cells. Depending on a cell line, hTERT knockdown led to a cell cycle arrest either in phase G1 or phase S/G2. Induction of apoptosis after hTERT downregulation with siRNA was observed. Additionally, hTERT targeting with lentiviruses, followed by cytostatics administration, led to induction of apoptosis. Interestingly, an increase in Double-Strand Breaks accompanied by activation of the main DNA repair mechanism, NER, was also observed. Altogether, we conclude that hTERT knockdown significantly contributes to the efficacy of HNSCC treatment.

Anti-hTERT siRNA-Loaded Nanoparticles Block the Growth of Anaplastic Thyroid Cancer Xenograft

The high frequency of hTERT-promoting mutations and the increased expression of hTERT mRNA in anaplastic thyroid cancer (ATC) make TERT a suitable molecular target for the treatment of this lethal neoplasm. In this study, we encapsulated an anti-hTERT oligonucleotide in biocompatible nanoparticles and analyzed the effects of this novel pharmaceutical preparation in preclinical models of ATC. Biocompatible nanoparticles were obtained in an acidified aqueous solution containing chitosan, anti-hTERT oligoRNAs, and poloxamer 188 as a stabilizer. The effects of these anti-hTERT nanoparticles (Na-siTERT) were tested in vitro on ATC cell lines (CAL-62 and 8505C) and in vivo on xenograft tumors obtained by flank injection of CAL-62 cells into SCID mice. The Na-siTERT reduced the viability and migration of CAL-62 and 8505C cells after 48-hour incubation. Intravenous administration (every 48 hours for 13 days) of this encapsulated drug in mice hosting a xenograft thyroid cancer determined a great reduction in the growth of the neoplasm (about 50% vs. untreated animals or mice receiving empty nanoparticles), and decreased levels of Ki67 associated with lower hTERT expression. Moreover, the treatment resulted in minimal invasion of nearby tissues and reduced the vascularity of the xenograft tumor. No signs of toxicity appeared following this treatment. Telomere length was not modified by the Na-siTERT, indicating that the inhibitory effects of neoplasm growth were independent from the enzymatic telomerase function. These findings demonstrate the potential suitability of this anti-TERT nanoparticle formulation as a novel tool for ATC treatment. Mol Cancer Ther; 17(6); 1187-95. ©2018 AACR.

Targeting death receptors for drug-resistant cancer therapy: Codelivery of pTRAIL and monensin using dual-targeting and stimuli-responsive self-assembling nanocomposites

Chemoresistance remains a formidable hurdle against cancer therapy. Seeking for novel therapy strategies is an urgent need for those who no longer benefit from chemotherapy. Chemoresistance is usually associated with the dysfunction of intrinsic apoptosis. Targeting extrinsic apoptosis via TRAIL signaling and the death receptors could be a potential solution to treat chemoresistant cancer. A highly biocompatible nano system for codelivery of the TRAIL DNA and the death receptor sensitizer monensin was developed, in which low-molecular-weight PEI (LMW-PEI) was crosslinked by the sulfhydryl cyclodextrin via disulfide bonds, and then bound with DNA, thus forming the bioreducible polyplex cores. In addition, the cyclodextrin also functioned as a carrier for the hydrophobic monensin via host-guest inclusion. Poly-γ-glutamic acid (γ-PGA) was used to modify the polyplex core via charge interaction. The γ-PGA corona can specifically bind with the tumor-associated gamma-glutamyl transpeptidase (GGT) overexpressed on the tumor cells, and achieve tumor-targeting delivery. Moreover, the tumor-homing peptide RGD-modified γ-PGA was also prepared as the surface coating materials for further improving gene delivery efficiency. This gene delivery system was characterized by the dual ligand-targeting, dual stimuli-responsive features. The ligands of RGD and γ-PGA can target the tumor-associated receptors (i.e., integrin and GGT). The conformation of γ-PGA is pH-sensitive, and the tumor acidic micro environments could trigger the detachment of surface-coating γ-PGA. The disulfide crosslinking LMW-PEI is redox-sensitive, and its fast disassembling in the tumor cells could favor the efficient gene delivery. The anti-tumor efficacy was demonstrated both in vitro and in vivo. Moreover, MYC-mediated synthetic lethality could be an important mechanism for overcoming the drug resistance. An important finding of our studies is the demonstration of the in vivo treatment efficacy of TRAIL/monensin, thus providing a potential novel therapeutic strategy for overcoming drug-resistant cancer.

Silencing of hTERT blocks growth and migration of anaplastic thyroid cancer cells

Mutations in the hTERT promoter responsible for constitutive telomerase activity are the most frequent genetic alteration detected in anaplastic thyroid cancer (ATC), and proposed as diagnostic and prognostic biomarker in these tumours. In this study we analyzed hTERT expression in a series of human ATCs and investigated the effects of small-interfering RNA-mediated silencing of hTERT on viability and migration and invasive properties of three human ATC cell lines. Expression of hTERT mRNA resulted increased in 8/10 ATCs compared to normal thyroid tissues. Silencing of hTERT in CAL-62, 8505C and SW1736 cells did not modify telomere length but determined a significant decrease (about 50%) of cell proliferation in all cell lines and a great reduction (about 50%) of migration and invasion capacity. These finding demonstrate that hTERT may be considered as a molecular target for ATC treatment.

Polymers for siRNA Delivery: A Critical Assessment of Current Technology Prospects for Clinical Application

The number of polymer-based vectors for siRNA delivery in clinical trials lags behind other delivery strategies; however, the molecular architectures and chemical compositions available to polymers make them attractive candidates for further exploration. Polymer vectors are extensively investigated in academic laboratories worldwide with fundamental progress having recently been made in the areas of high-throughput screening, synthetic methods, cellular internalization, endosomal escape and computational prediction and analysis. This review assesses recent advances within the field and highlights relevant developments from within the complementary fields of nanotechnology and protein chemistry with the intent to propose future work that addresses key gaps within the current body of knowledge, potentially advancing the development of the next generation of polymeric vectors.

Delivery strategies and potential targets for siRNA in major cancer types

Small interfering RNA (siRNA) has gained attention as a potential therapeutic reagent due to its ability to inhibit specific genes in many genetic diseases. For many years, studies of siRNA have progressively advanced toward novel treatment strategies against cancer. Cancer is caused by various mutations in hundreds of genes including both proto-oncogenes and tumor suppressor genes. In order to develop siRNAs as therapeutic agents for cancer treatment, delivery strategies for siRNA must be carefully designed and potential gene targets carefully selected for optimal anti-cancer effects. In this review, various modifications and delivery strategies for siRNA delivery are discussed. In addition, we present current thinking on target gene selection in major tumor types.

Multi-functionalized carbon dots as theranostic nanoagent for gene delivery in lung cancer therapy

Theranostics, an integrated therapeutic and diagnostic system, can simultaneously monitor the real-time response of therapy. Different imaging modalities can combine with a variety of therapeutic moieties in theranostic nanoagents. In this study, a multi-functionalized, integrated theranostic nanoagent based on folate-conjugated reducible polyethylenimine passivated carbon dots (fc-rPEI-Cdots) is developed and characterized. These nanoagents emit visible blue photoluminescence under 360 nm excitation and can encapsulate multiple siRNAs (EGFR and cyclin B1) followed by releasing them in intracellular reductive environment. In vitro cell culture study demonstrates that fc-rPEI-Cdots is a highly biocompatible material and a good siRNA gene delivery carrier for targeted lung cancer treatment. Moreover, fc-rPEI-Cdots/pooled siRNAs can be selectively accumulated in lung cancer cells through receptor mediated endocytosis, resulting in better gene silencing and anti-cancer effect. Combining bioimaging of carbon dots, stimulus responsive property, gene silencing strategy, and active targeting motif, this multi-functionalized, integrated theranostic nanoagent may provide a useful tool and platform to benefit clinicians adjusting therapeutic strategy and administered drug dosage in real time response by monitoring the effect and tracking the development of carcinomatous tissues in diagnostic and therapeutic aspects.

Multifunctional cationic polyurethanes designed for non-viral cancer gene therapy

Nano-polyplexes from bioreducible cationic polymers have a massive promise for cancer gene therapy. However, the feasibility of cationic polyurethanes for non-viral gene therapy is so far not well studied. In this work, a linear cationic polyurethane containing disulfide bonds, urethane linkages and protonable tertiary amino groups was successfully generated by stepwise polycondensation reaction between 2,2'-dithiodiethanol bis(p-nitrophenyl carbonate) and 1,4-bis(3-aminopropyl)piperazine (BAP). We confirmed that the cationic polyurethane (denoted as PUBAP) displayed superior gene delivery properties to its cationic polyamide analogue, thus causing higher in vitro transfection efficiency in MCF-7 and SKOV-3 cells. Besides, further folate-PEGylation and hydrophobic deoxycholic acid (DCA) conjugation to amino-containing PUBAP can be conducted to afford multifunctional polyurethane gene delivery system. After optimization, folate-decorated nano-polyplexes from the PUBAP conjugated with 8 folate-PEG chains and 12 DCA residues exhibited superb colloidal stability under physiological conditions, and performed rapid uptake via folate receptor-mediated endocytosis, efficient intracellular gene release and nucleus translocation into SKOV-3 cells in vitro and in vivo. Importantly, PUBAP based polyplexes possess low cytotoxicity as a result of PUBAP biodegradability. Therefore, marked growth inhibition of SKOV-3 tumor xenografted in Balb/c nude mice was achieved with negligible side effects on the mouse health after intravenous administration of PUBAP based polyplexes with a therapeutic plasmid encoding for TNF-related apoptosis-inducing ligand. This work provides a new insight into biomedical application of bio-responsive polyurethanes for cancer therapy.

STATEMENT OF SIGNIFICANCE

In this study, we have confirmed that disulfide-based cationic polyurethane presents a new non-viral vector for gene transfer and cancer gene therapy. The significance of this work includes: (1) design and synthesis of a group of novel disulfide-based cationic polyurethane by non-isocyanate chemistry; (2) comparative study of transfection activity between cationic polyurethanes and cationic polyamides; (3) feasibility of bioreducible cationic polyurethanes for in vivo cancer gene therapy.

DOTAP functionalizing single-walled carbon nanotubes as non-viral vectors for efficient intracellular siRNA delivery

CONTEXT

Functionalized single-walled carbon nanotubes (SWNT) with 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) were used as novel and more convenient carriers of small interfering RNA (siRNA).

OBJECTIVE

To utilize the unique capability of SWNT to be easily modified by functional groups and readily internalized by mammalian cells to bind, condense, stabilize siRNA and enhance its transfection efficiency.

METHODS

After SWNT were non-covalently functionalized by cationic DOTAP (SWNT-DOTAP), siRNA interacted with SWNT-DOTAP via static electricity (SWNT-DOTAP/siRNA). Subsequently, the size, zeta potential and morphology of SWNT-DOTAP/siRNA were analyzed. The optimal compression ratio and stability of siRNA were assessed by agarose gel electrophoresis. Furthermore, in prostate carcinoma PC-3 cells, RT-PCR, flow cytometry and sulforhodamine B assays were used to evaluate the silencing activity, transfection efficiency and cell proliferation, respectively.

RESULTS AND DISCUSSION

The characteristics of SWNT-DOTAP, i.e. an average size of 194.49 nm, a zeta potential of 45.16 mV and lower cytotoxicity than Lipofectamine 2000, indicated that this vector was suitable for siRNA delivery. Moreover, after interaction with SWNT-DOTAP, siRNA of human telomerase reverse transcriptase was bound, condensed and stabilized. In PC-3 cells, SWNT-DOTAP/siRNA exhibited 82.6% silencing activity and 92% transfection efficiency. Furthermore, the complexes inhibited cell proliferation by 42.1%.

CONCLUSION

SWNT-DOTAP may be a promising siRNA delivery vector for gene-based therapeutic applications in cancer.

A family of cationic polyamides for in vitro and in vivo gene transfection

The purpose of this study is to develop biodegradable cationic polyamides for non-viral gene delivery and elucidate their structural effects on gene transfection activity. To this end, a group of novel cationic polyamides were synthesized by polycondensation reaction between different di-p-nitrophenyl esters and tertiary amine-containing primary diamines. These linear polyamides have flexible alkylene group (ethylene or propylene), protonable amino group and bioreducible disulfide linkage in the polyamide main chain. The alkylene group and disulfide linkage in these polyamides have a distinct effect on their gene delivery properties including buffering capacity, gene binding ability and intracellular gene release profile. Those cationic polyamides containing disulfide linkage and 1,4-bis(3-aminopropyl)piperazine (BAP) residue exhibited high buffering capacity (endosomal escape ability), high gene binding ability, and intracellular gene release ability, thus inducing fast gene nucleus translocation and robust gene transfection in vitro against different cell lines and rat bone marrow mesenchymal stem cells. Moreover, the transfection efficiencies in vitro were comparable or higher than those of 25 kDa branched polyethylenimine and Lipofectamine 2000 transfection agent as positive controls. These cationic polyamides and their polyplexes were of low cytotoxicity when an optimal transfection efficacy was achieved. In vivo transfection tests showed that bioreducible BAP-based polyamides were applicable for intravenous gene delivery in a mouse model, leading to higher level of transgene expression in the liver as compared to 22 kDa linear polyethylenimine as a positive control. These cationic polyamides provide a useful platform to elucidate the relationship between chemical functionalities and gene transfection activity.

Redox-Sensitive Polymer/SPIO Nanocomplexes for Efficient Magnetofection and MR Imaging of Human Cancer Cells

Magnetofection has received increasing attention for its great potential on gene therapy. To promote its clinical therapeutic applications, development of safe and effective magnetic nanocarriers is in high demand. Herein, we present a redox-sensitive polymer/metal nanocomplex system (PSPIO) for efficient magnetofection and magnet resonance imaging (MRI) on cancer cells. PSPIO was prepared by modifying SPIO with redox-sensitive polyethylenimine (SSPEI) via a ligand exchange process. PSPIO could efficiently condense plasmid DNA (pDNA) into nanoparticles, which exhibited several favorable properties for gene delivery, including protection of nucleic acids from enzymatic degradation, stable colloids in serum, and redox-responsive pDNA release. As a potential MR imaging agent, PSPIO displayed good magnetization (28.3 emu/g) and dose-dependent T2-weighted imaging contrast (R2 = 291.1 s(-1) mM(-1)) in vitro. The use of redox-sensitive SSPEI polymer contributed to much lower cytotoxicity of PSPIO compared to nondegradable bPEI25k. In vitro transfection efficiency of PSPIO was significantly enhanced under an external magnetic field. In the presence of serum, PSPIO exhibited higher transgene expression than SSPEI or bPEI25k polymer on mouse glioma (ALTS1C1) or human prostate cancer (PC3) cell lines. Taken together, it is demonstrated that PSPIO possess great potential for cancer gene therapy and molecular imaging.

The overexpression and nuclear translocation of Trx-1 during hypoxia confers on HepG2 cells resistance to DDP, and GL-V9 reverses the resistance by suppressing the Trx-1/Ref-1 axis

Microenvironmental hypoxia gives many tumor cells the capacity for drug resistance. Thioredoxin family members play critical roles in the regulation of cellular redox homeostasis in a stressed environment. In this study, we established a hypoxia-drug resistance (hypoxia-DR) model using HepG2 cells and discovered that the overexpression and nuclear translocation of thioredoxin-1 (Trx-1) are closely associated with this resistance through the regulation of the metabolism by the oxidative stress response to glycolysis. Intranuclear Trx-1 enhances the DNA-binding activity of HIF-1α via its interaction with and reducing action on Ref-1, resulting in increased expression of glycolysis-related proteins (PDHK1, HKII, and LDHA), glucose uptake, and lactate generation under hypoxia. Meanwhile, we found that GL-V9, a newly synthesized flavonoid derivative, shows an ability to reverse the hypoxia-DR and has low toxicity both in vivo and in vitro. GL-V9 could inhibit the expression and nuclear translocation of Trx-1 and then suppress HIF-1α DNA-binding activity by inhibiting the Trx-1/Ref-1 axis. As a result, glycolysis is weakened and oxidative phosphorylation is enhanced. Thus, GL-V9 leads to an increment in intracellular ROS generation and consequently intensified apoptosis induced by DDP.

Complexation of bioreducible cationic polymers with gold nanoparticles for improving stability in serum and application on nonviral gene delivery

Widespread applications of conventional polymeric gene carriers are greatly hampered by their inefficient transfection performance under serum-containing environment. Aiming to overcome this limitation, we propose a bioreducible polyethylenimine-gold nanocomplex system (SSPEI-Au NC), which can be prepared by a simple layer-by-layer (LBL) assembly procedure. SSPEI-Au NC contains sequentially deposited layers of bioreducible polyethylenimine (SSPEI) and poly(γ-glutamic acid) (γ-PGA) for efficient binding and delivery of plasmid DNA (pDNA). SSPEI-Au NC was characterized for various physicochemical properties, including: UV-vis spectra, TEM imaging, hydrodynamic size, and pDNA binding ability. The SSPEI-Au NC were efficiently uptaken by mammalian cells as observed using dark-field microscopy. Comparing to nondegradable PEI25k, the bioreducible SSPEI-Au NC exhibited superior transfection capability under serum-containing condition while causing lower cytotoxicity on mammalian cell lines. The effect of serum on SSPEI-Au NC dispersity was studied using UV-vis spectrometry and the results suggest that serum-assisted colloidal stability of SSPEI-Au NC contributed to its serum-resistant transfection.

Mutations in IDH1, IDH2, and in the TERT promoter define clinically distinct subgroups of adult malignant gliomas

Frequent mutations in isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) and the promoter of telomerase reverse transcriptase (TERT) represent two significant discoveries in glioma genomics. Understanding the degree to which these two mutations co-occur or occur exclusively of one another in glioma subtypes presents a unique opportunity to guide glioma classification and prognosis. We analyzed the relationship between overall survival (OS) and the presence of IDH1/2 and TERT promoter mutations in a panel of 473 adult gliomas. We hypothesized and show that genetic signatures capable of distinguishing among several types of gliomas could be established providing clinically relevant information that can serve as an adjunct to histopathological diagnosis. We found that mutations in the TERT promoter occurred in 74.2% of glioblastomas (GBM), but occurred in a minority of Grade II-III astrocytomas (18.2%). In contrast, IDH1/2 mutations were observed in 78.4% of Grade II-III astrocytomas, but were uncommon in primary GBM. In oligodendrogliomas, TERT promoter and IDH1/2 mutations co-occurred in 79% of cases. Patients whose Grade III-IV gliomas exhibit TERT promoter mutations alone predominately have primary GBMs associated with poor median OS (11.5 months). Patients whose Grade III-IV gliomas exhibit IDH1/2 mutations alone predominately have astrocytic morphologies and exhibit a median OS of 57 months while patients whose tumors exhibit both TERT promoter and IDH1/2 mutations predominately exhibit oligodendroglial morphologies and exhibit median OS of 125 months. Analyzing gliomas based on their genetic signatures allows for the stratification of these patients into distinct cohorts, with unique prognosis and survival.

In vitro and in vivo gene transfection using biodegradable and low cytotoxic nanomicelles based on dendritic block copolymers

Dendritic PCL-b-PDMAEMA copolymers have been used as non-viral vectors for gene transfection and exhibited high transfection efficiencies and low cytotoxicity.

Bioapplications of hyperbranched polymers

The recent research progress in biological and biomedical applications of hyperbranched polymers has been summarized in this review.

Synthesis and therapeutic applications of biocompatible or biodegradable hyperbranched polymers

The recent progress in the synthesis, modifications and therapeutic applications of biocompatible or biodegradable hyperbranched polymers has been reviewed.

Silencing of the hTERT gene by shRNA inhibits colon cancer SW480 cell growth in vitro and in vivo

Human telomerase reverse transcriptase (hTERT) is the key enzyme responsible for synthesizing and maintaining the telomeres on the ends of chromosomes, and it is essential for cell proliferation. This has made hTERT a focus of oncology research and an attractive target for anticancer drug development. In this study, we designed a small interfering RNA (siRNA) targeting the catalytic subunit of hTERT and tested its effects on the growth of telomerase-positive human colon carcinoma SW480 cells in vitro, as well as on the tumorigenicity of these cells in nude mice. Transient and stable transfection of hTERT siRNA into colon cancer SW480 cells suppressed hTERT expression, reduced telomerase activity and inhibited cell growth and proliferation. Knocking down hTERT expression in SW480 tumors xenografted into nude mice significantly slowed tumor growth and promoted tumor cell apoptosis. Our results suggest that hTERT is involved in carcinogenesis of human colon carcinoma, and they highlight the therapeutic potential of a hTERT knock-down approach.

Silencing of TERT decreases levels of miR-1, miR-21, miR-29a and miR-208a in cardiomyocytes

To test the hypothesis that telomerase reverse transcriptase (TERT) as an RNA-dependent RNA polymerase could be involved in the amplification of microRNA (miRNA), we have determined the levels of immature and mature miRNA in cultured neonatal rat cardiomyocytes, during the silencing of TERT by siRNA. The silencing of the TERT gene led to the reduction of both telomerase activity and the TERT mRNA expression when compared with scrambled RNA. TERT gene silencing resulted in the decrement of three studied mature miRNAs levels: miRNA-21, miRNA-29a and miRNA-208a when compared with scrambled RNA; but miRNA-1, it was not changed significantly. At the same time, levels of immature miRNA-1 and miRNA-208a were not changed, although the levels of immature miRNA-29a and pri-miRNA-1 were decreased. The data obtained allow us to permit that TERT is a genome-independent source of mature miRNA, and the changes in telomerase activity can significantly influence the level of miRNA in cardiomyocytes.

Theranostic nanoparticles based on bioreducible polyethylenimine-coated iron oxide for reduction-responsive gene delivery and magnetic resonance imaging

Theranostic nanoparticles based on superparamagnetic iron oxide (SPIO) have a great promise for tumor diagnosis and gene therapy. However, the availability of theranostic nanoparticles with efficient gene transfection and minimal toxicity remains a big challenge. In this study, we construct an intelligent SPIO-based nanoparticle comprising a SPIO inner core and a disulfide-containing polyethylenimine (SSPEI) outer layer, which is referred to as a SSPEI-SPIO nanoparticle, for redox-triggered gene release in response to an intracellular reducing environment. We reveal that SSPEI-SPIO nanoparticles are capable of binding genes to form nano-complexes and mediating a facilitated gene release in the presence of dithiothreitol (5–20 mM), thereby leading to high transfection efficiency against different cancer cells. The SSPEI-SPIO nanoparticles are also able to deliver small interfering RNA (siRNA) for the silencing of human telomerase reverse transcriptase genes in HepG2 cells, causing their apoptosis and growth inhibition. Further, the nanoparticles are applicable as T2-negative contrast agents for magnetic resonance (MR) imaging of a tumor xenografted in a nude mouse. Importantly, SSPEI-SPIO nanoparticles have relatively low cytotoxicity in vitro at a high concentration of 100 μg/mL. The results of this study demonstrate the utility of a disulfide-containing cationic polymer-decorated SPIO nanoparticle as highly potent and low-toxic theranostic nano-system for specific nucleic acid delivery inside cancer cells.

Bioreducible polycations in nucleic acid delivery: past, present, and future trends

Polycations that are degradable by reduction of disulfide bonds are developed for applications in delivery of nucleic acids. This Feature Article surveys methods of synthesis of bioreducible polycations and discusses current understanding of the mechanism of action of bioreducible polyplexes. Emphasis is placed on the relationship between the biological redox environment and toxicity, trafficking, transfection activity, and in vivo behavior of bioreducible polycations and polyplexes.

Mannosylated bioreducible nanoparticle-mediated macrophage-specific TNF-α RNA interference for IBD therapy

The application of RNA interference (RNAi) for inflammatory bowel disease (IBD) therapy has been limited by the lack of non-cytotoxic, efficient and targetable small interfering RNA (siRNA) carriers. TNF-α is the major pro-inflammatory cytokine mainly secreted by macrophages during IBD. Here, a mannosylated bioreducible cationic polymer (PPM) was synthesized and further spontaneously assembled nanoparticles (NPs) assisted by sodium triphosphate (TPP). The TPP-PPM/siRNA NPs exhibited high uniformity (polydispersity index = 0.004), a small particle size (211-275 nm), excellent bioreducibility, and enhanced cellular uptake. Additionally, the generated NPs had negative cytotoxicity compared to control NPs fabricated by branched polyethylenimine (bPEI, 25 kDa) or Oligofectamine (OF) and siRNA. In vitro gene silencing experiments revealed that TPP-PPM/TNF-α siRNA NPs with a weight ratio of 40:1 showed the most efficient inhibition of the expression and secretion of TNF-α (approximately 69.9%, which was comparable to the 71.4% obtained using OF/siRNA NPs), and its RNAi efficiency was highly inhibited in the presence of mannose (20 mm). Finally, TPP-PPM/siRNA NPs showed potential therapeutic effects on colitis tissues, remarkably reducing TNF-α level. Collectively, these results suggest that non-toxic TPP-PPM/siRNA NPs can be exploited as efficient, macrophage-targeted carriers for IBD therapy.