Anticancer molecule AS1411 exhibits low nanomolar antiviral activity against HIV-1

Molecular Complementarity of Proteomimetic Materials for Target-Specific Recognition and Recognition-Mediated Complex Functions

As biomolecules essential for sustaining life, proteins are generated from long chains of 20 different α-amino acids that are folded into unique 3D structures. In particular, many proteins have molecular recognition functions owing to their binding pockets, which have complementary shapes, charges, and polarities for specific targets, making these biopolymers unique and highly valuable for biomedical and biocatalytic applications. Based on the understanding of protein structures and microenvironments, molecular complementarity can be exhibited by synthesizable and modifiable materials. This has prompted researchers to explore the proteomimetic potentials of a diverse range of materials, including biologically available peptides and oligonucleotides, synthetic supramolecules, inorganic molecules, and related coordination networks. To fully resemble a protein, proteomimetic materials perform the molecular recognition to mediate complex molecular functions, such as allosteric regulation, signal transduction, enzymatic reactions, and stimuli-responsive motions; this can also expand the landscape of their potential bio-applications. This review focuses on the recognitive aspects of proteomimetic designs derived for individual materials and their conformations. Recent progress provides insights to help guide the development of advanced protein mimicry with material heterogeneity, design modularity, and tailored functionality. The perspectives and challenges of current proteomimetic designs and tools are also discussed in relation to future applications.

Properties and Potential Antiproliferative Activity of Thrombin-Binding Aptamer (TBA) Derivatives with One or Two Additional G-Tetrads

In this paper, we study the biological properties of two TBA analogs containing one and two extra G-tetrads, namely TBAG3 and TBAG4, respectively, and two further derivatives in which one of the small loops at the bottom (TBAG41S) or the large loop at the top (TBAG4GS) of the TBAG4 structure has been completely modified by replacing all loop residues with abasic site mimics. The therapeutical development of the TBA was hindered by its low thermodynamic and nuclease stability, while its potential as an anticancer/antiproliferative molecule is also affected by the anticoagulant activity, being a side effect in this case. In order to obtain suitable TBA analogs and to explore the involvement of specific aptamer regions in biological activity, the antiproliferative capability against DU 145 and MDAMB 231 cancer cell lines (MTT), the anticoagulant properties (PT), the biological degradability (nuclease stability assay) and nucleolin (NCL) binding ability (SPR) of the above described TBA derivatives have been tested. Interestingly, none of the TBA analogs exhibits an anticoagulant activity, while all of them show antiproliferative properties to the same extent. Furthermore, TBAG4 displays extraordinary nuclease stability and promising antiproliferative properties against breast cancer cells binding NCL efficiently. These results expand the range of G4-structures targeting NCL and the possibility of developing novel anticancer and antiviral drugs.

Progress in cancer drug delivery based on AS1411 oriented nanomaterials

Targeted cancer therapy has become one of the most important medical methods because of the spreading and metastatic nature of cancer. Based on the introduction of AS1411 and its four-chain structure, this paper reviews the research progress in cancer detection and drug delivery systems by modifying AS1411 aptamers based on graphene, mesoporous silica, silver and gold. The application of AS1411 in cancer treatment and drug delivery and the use of AS1411 as a targeting agent for the detection of cancer markers such as nucleoli were summarized from three aspects of active targeting, passive targeting and targeted nucleic acid apharmers. Although AS1411 has been withdrawn from clinical trials, the research surrounding its structural optimization is still very popular. Further progress has been made in the modification of nanoparticles loaded with TCM extracts by AS1411.

Four-Layered Intramolecular Parallel G-Quadruplex with Non-Nucleotide Loops: An Ultra-Stable Self-Folded DNA Nano-Scaffold

A four-stranded scaffold of nucleic acids termed G-quadruplex (G4) has found growing applications in nano- and biotechnology. Propeller loops are a hallmark of the most stable intramolecular parallel-stranded G4s. To date, propeller loops have been observed to span only a maximum of three G-tetrad layers. Going beyond that would allow creation of more stable scaffolds useful for building robust nanodevices. Here we investigate the formation of propeller loops spanning more than three layers. We show that native nucleotide sequences are incompatible toward this goal, and we report on synthetic non-nucleotide linkers that form a propeller loop across four layers. With the established linkers, we constructed a four-layered intramolecular parallel-stranded G4, which exhibited ultrahigh thermal stability. Control on loop design would augment the toolbox toward engineering of G4-based nanoscaffolds for diverse applications.

Aptamer-Based Antibacterial and Antiviral Therapy against Infectious Diseases

Nucleic acid aptamers are single-stranded DNA or RNA molecules selected in vitro that can bind to a broad range of targets with high affinity and specificity. As promising alternatives to conventional anti-infective agents, aptamers have gradually revealed their potential in the combat against infectious diseases. This article provides an overview on the state-of-art of aptamer-based antibacterial and antiviral therapeutic strategies. Diverse aptamers targeting pathogen-related components or whole pathogenic cells are summarized according to the species of microorganisms. These aptamers exhibited remarkable in vitro and/or in vivo inhibitory effect for pathogenic invasion, enzymatic activities, or viral replication, even for some highly drug-resistant strains and biofilms. Aptamer-mediated drug delivery and controlled drug release strategies are also included herein. Critical technical barriers of therapeutic aptamers are briefly discussed, followed by some future perspectives for their implementation into clinical utility.

Aptamers in Virology-A Consolidated Review of the Most Recent Advancements in Diagnosis and Therapy

The use of short oligonucleotide or peptide molecules as target-specific aptamers has recently garnered substantial attention in the field of the detection and treatment of viral infections. Based on their high affinity and high specificity to desired targets, their use is on the rise to replace antibodies for the detection of viruses and viral antigens. Furthermore, aptamers inhibit intracellular viral transcription and translation, in addition to restricting viral entry into host cells. This has opened up a plethora of new targets for the research and development of novel vaccines against viruses. Here, we discuss the advances made in aptamer technology for viral diagnosis and therapy in the past decade.

Quinolinonyl Non-Diketo Acid Derivatives as Inhibitors of HIV-1 Ribonuclease H and Polymerase Functions of Reverse Transcriptase

Novel anti-HIV agents are still needed to overcome resistance issues, in particular inhibitors acting against novel viral targets. The ribonuclease H (RNase H) function of the reverse transcriptase (RT) represents a validated and promising target, and no inhibitor has reached the clinical pipeline yet. Here, we present rationally designed non-diketo acid selective RNase H inhibitors (RHIs) based on the quinolinone scaffold starting from former dual integrase (IN)/RNase H quinolinonyl diketo acids. Several derivatives were synthesized and tested against RNase H and viral replication and found active at micromolar concentrations. Docking studies within the RNase H catalytic site, coupled with site-directed mutagenesis, and Mg²⁺ titration experiments demonstrated that our compounds coordinate the Mg²⁺ cofactor and interact with amino acids of the RNase H domain that are highly conserved among naïve and treatment-experienced patients. In general, the new inhibitors influenced also the polymerase activity of RT but were selective against RNase H vs the IN enzyme.

Co-delivery of doxorubicin and aptamer against Forkhead box M1 using chitosan-gold nanoparticles coated with nucleolin aptamer for synergistic treatment of cancer cells

Herein, a nanotherapeutic delivery method was presented for co-delivery of doxorubicin (DOX) and aptamer against Forkhead box M1 (FOXM1 Apt) to cancer cells. Firstly, the vehicle composed of chitosan (CS)-Gold nanoparticles (AuNPs) conjugate was prepared. Nucleolin aptamer (AS1411) and FOXM1 Apt were loaded onto the CS-AuNPs and formed Aptamers (Apts)-CS-AuNPs. Subsequently, DOX was added to the Apts-CS-AuNPs to obtain the DOX-Apts-CS-AuNPs complex for synergistic treatment of tumor. The data of flow cytometry analysis and fluorescence imaging displayed that the complex was effectively internalized into target cells (A549 and 4T1 cells, nucleolin+) but not into CHO cells as nontarget cells. The results of the MTT assay showed that the complex significantly increased cell mortality in 4T1 and A549 cells compared to CHO cells treated with the complex. The in vivo studies demonstrated that the DOX-Apts-CS-AuNPs complex exhibited more tumor inhibitory effect and less distribution in other organs compared to free DOX.

Synthesis of new riboflavin modified ODNs: Effect of riboflavin moiety on the G-quadruplex arrangement and stability

In the panorama of modified G-quadruplexes (G4s) with interesting proprieties, here, it has been reported the synthesis of new modified d(TGGGAG) sequences forming G-quadruplexes, with the insertion of a riboflavin unit (Rf, vitamin B₂). Exploiting the flavin similarity with the hydrogen bond pattern of guanine and aiming at mimic a typical nucleoside scaffold, the synthesis of the riboflavin building block 3 it has been efficiently carried out. The effect of insertion of riboflavin mimic nucleoside on the G-quadruplex properties has been here, for the first time investigated. A biophysical characterization of Rf-modified sequences (A-D) has been carried out by circular dichroism (CD), fluorescence spectroscopy, differential scanning calorimetry (DSC) and native gel electrophoresis. CD and electrophoresis data have suggested that Rf-modified sequences are able to form parallel tetramolecular G4 structures similar to that of the unmodified sequence. Analysis of the DSC thermograms has revealed that all modified G-quadruplexes have a higher thermal stability compared with the natural sequence, particularly the stabilisation is higher when the Rf residue is introduced at the 3'-end. Further, DSC analysis has revealed that the Rf residues introduced at the 3'-end are able to form additional stabilising interactions, energetically almost comparable to the enthalpic contribution of a G-tetrad. Fluorescence measurement are consistent with this result showing that the Rf residues introduced at 3'-end are able to form stacking interactions with the adjacent bases within the G-quadruplex structure. The whole of data suggested that the introduction of Rf unit can stabilize G-quadruplex structures and can be a promising candidate for future theranostic applications.

Intra-locked G-quadruplex structures formed by irregular DNA G-rich motifs

G-rich DNA sequences with tracts of three or more continuous guanines (G≥3) are known to have high propensity to adopt stable G-quadruplex (G4) structures. Bioinformatic analyses suggest high prevalence of G-rich sequences with short G-tracts (G≤2) in the human genome. However, due to limited structural studies, the folding principles of such sequences remain largely unexplored and hence poorly understood. Here, we present the solution NMR structure of a sequence named AT26 consisting of irregularly spaced G2 tracts and two isolated single guanines. The structure is a four-layered G4 featuring two bi-layered blocks, locked between themselves in an unprecedented fashion making it a stable scaffold. In addition to edgewise and propeller-type loops, AT26 also harbors two V-shaped loops: a 2-nt V-shaped loop spanning two G-tetrad layers and a 0-nt V-shaped loop spanning three G-tetrad layers, which are named as VS- and VR-loop respectively, based on their distinct structural features. The intra-lock motif can be a basis for extending the G-tetrad core and a very stable intra-locked G4 can be formed by a sequence with G-tracts of various lengths including several G2 tracts. Findings from this study will aid in understanding the folding of G4 topologies from sequences containing irregularly spaced multiple short G-tracts.

G-Quadruplex-Forming Aptamers-Characteristics, Applications, and Perspectives

G-quadruplexes constitute a unique class of nucleic acid structures formed by G-rich oligonucleotides of DNA- or RNA-type. Depending on their chemical nature, loops length, and localization in the sequence or structure molecularity, G-quadruplexes are highly polymorphic structures showing various folding topologies. They may be formed in the human genome where they are believed to play a pivotal role in the regulation of multiple biological processes such as replication, transcription, and translation. Thus, natural G-quadruplex structures became prospective targets for disease treatment. The fast development of systematic evolution of ligands by exponential enrichment (SELEX) technologies provided a number of G-rich aptamers revealing the potential of G-quadruplex structures as a promising molecular tool targeted toward various biologically important ligands. Because of their high stability, increased cellular uptake, ease of chemical modification, minor production costs, and convenient storage, G-rich aptamers became interesting therapeutic and diagnostic alternatives to antibodies. In this review, we describe the recent advances in the development of G-quadruplex based aptamers by focusing on the therapeutic and diagnostic potential of this exceptional class of nucleic acid structures.

A Minimal Sequence for Left-Handed G-Quadruplex Formation

Recently, we observed the first example of a left-handed G-quadruplex structure formed by natural DNA, named Z-G4. We analysed the Z-G4 structure and inspected its primary 28-nt sequence in order to identify motifs that convey the unique left-handed twist. Using circular dichroism spectroscopy, NMR spectroscopy, and X-ray crystallography, we revealed a minimal sequence motif of 12 nt (GTGGTGGTGGTG) for formation of the left-handed DNA G-quadruplex, which is found to be highly abundant in the human genome. A systematic analysis of thymine loop mutations revealed a moderate sequence tolerance, which would further broaden the space of sequences prone to left-handed G-quadruplex formation.

Exploring the conformational behaviour and aggregation properties of lipid-conjugated AS1411 aptamers

AS1411 is a nucleolin-binding aptamer which attracted great interest as active targeting ligand for the selective delivery of therapeutic agents to tumour cells. In this work we selected three AS1411 derivatives 5'-conjugated with lipophilic tails and studied their properties in view of their application in liposomial formulations and/or lipid coated-nanoparticles for targeted therapies. The conformational behaviour of these AS1411 analogs has been investigated in comparison with the unmodified aptamer by CD, UV, PAGE, SEC-HPLC, DLS and thioflavin T (ThT) fluorescence assays to get insight in their secondary structure and aggregation properties. This study has been performed in pseudo-physiological buffers mimicking the extra- and intracellular environments, and at different concentrations in the μM range, paying special attention to the effects of the lipophilic tail on the overall aptamer conformation. The 5'-lipidated AS1411 derivatives proved to fold into stable, parallel unimolecular G-quadruplex structures, forming large aggregates, mainly micelles, at conc. >10 μM. Preliminary bioscreenings on selected cancer cells showed that these derivatives are less cytotoxic than AS1411, but maintain a similar biological behaviour. This study demonstrated that lipophilic tails dramatically favour the formation of AS1411 aggregates, however not impairing the formation and thermal stability of its peculiar G4 motifs.

G-Quadruplex Identification in the Genome of Protozoan Parasites Points to Naphthalene Diimide Ligands as New Antiparasitic Agents

G-quadruplexes (G4) are DNA secondary structures that take part in the regulation of gene expression. Putative G4 forming sequences (PQS) have been reported in mammals, yeast, bacteria, and viruses. Here, we present PQS searches on the genomes of T. brucei, L. major, and P. falciparum. We found telomeric sequences and new PQS motifs. Biophysical experiments showed that EBR1, a 29 nucleotide long highly repeated PQS in T. brucei, forms a stable G4 structure. G4 ligands based on carbohydrate conjugated naphthalene diimides (carb-NDIs) that bind G4’s including hTel could bind EBR1 with selectivity versus dsDNA. These ligands showed important antiparasitic activity. IC₅₀ values were in the nanomolar range against T. brucei with high selectivity against MRC-5 human cells. Confocal microscopy confirmed these ligands localize in the nucleus and kinetoplast of T. brucei suggesting they can reach their potential G4 targets. Cytotoxicity and zebrafish toxicity studies revealed sugar conjugation reduces intrinsic toxicity of NDIs.

G-quadruplex structure of an anti-proliferative DNA sequence

AGRO100 (also known as AS1411) is a G-rich oligonucleotide that has long been established as a potent anti-cancer aptamer. However, the structure of AGRO100 remained unresolved, due to the co-existence of multiple different G-quadruplex conformations. We identified a DNA sequence named AT11, derived from AGRO100, which formed a single major G-quadruplex conformation and exhibited a similar anti-proliferative activity as AGRO100. The solution structure of AT11 revealed a four-layer G-quadruplex comprising of two propeller-type parallel-stranded subunits connected through a central linker. The stacking between the two subunits occurs at the 3΄-end of the first block and the 5΄-end of the second block. The structure of the anti-proliferative DNA sequence AT11 will allow greater understanding on the G-quadruplex folding principles and aid in structural optimization of anti-proliferative oligonucleotides.

The cellular protein nucleolin preferentially binds long-looped G-quadruplex nucleic acids

BACKGROUND

G-quadruplexes (G4s) are four-stranded nucleic acid structures that form in G-rich sequences. Nucleolin (NCL) is a cellular protein reported for its functions upon G4 recognition, such as induction of neurodegenerative diseases, tumor and virus mechanisms activation. We here aimed at defining NCL/G4 binding determinants.

METHODS

Electrophoresis mobility shift assay was used to detect NCL/G4 binding; circular dichroism to assess G4 folding, topology and stability; dimethylsulfate footprinting to detect G bases involved in G4 folding.

RESULTS

The purified full-length human NCL was initially tested on telomeric G4 target sequences to allow for modulation of loop, conformation, length, G-tract number, stability. G4s in promoter regions with more complex sequences were next employed. We found that NCL binding to G4s heavily relies on G4 loop length, independently of the conformation and oligonucleotide/loop sequence. Low stability G4s are preferred. When alternative G4 conformations are possible, those with longer loops are preferred upon binding to NCL, even if G-tracts need to be spared from G4 folding.

CONCLUSIONS

Our data provide insight into how G4s and the associated proteins may control the ON/OFF molecular switch to several pathological processes, including neurodegeneration, tumor and virus activation. Understanding these regulatory determinants is the first step towards the development of targeted therapies.

GENERAL SIGNIFICANCE

The indication that NCL binding preferentially stimulates and induces folding of G4s containing long loops suggests NCL ability to modify the overall structure and steric hindrance of the involved nucleic acid regions. This protein-induced modification of the G4 structure may represent a cellular mechanosensor mechanism to molecular signaling and disease pathogenesis. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.

G-quadruplex oligonucleotide AS1411 as a cancer-targeting agent: Uses and mechanisms

BACKGROUND

AS1411 is a 26-mer G-rich DNA oligonucleotide that forms a variety of G-quadruplex structures. It was identified based on its cancer-selective antiproliferative activity and subsequently determined to be an aptamer to nucleolin, a multifunctional protein that preferentially binds quadruplex nucleic acids and which is present at high levels on the surface of cancer cells. AS1411 has exceptionally efficient cellular internalization compared to non-quadruplex DNA sequences.

SCOPE OF REVIEW

Recent developments related to AS1411 will be examined, with a focus on its use for targeted delivery of therapeutic and imaging agents.

MAJOR CONCLUSIONS

Numerous research groups have used AS1411 as a targeting agent to deliver nanoparticles, oligonucleotides, and small molecules into cancer cells. Studies in animal models have demonstrated that AS1411-linked materials can accumulate selectively in tumors following systemic administration. The mechanism underlying the cancer-targeting ability of AS1411 is not completely understood, but recent studies suggest a model that involves: (1) initial uptake by macropinocytosis, a form of endocytosis prevalent in cancer cells; (2) stimulation of macropinocytosis by a nucleolin-dependent mechanism resulting in further uptake; and (3) disruption of nucleolin-mediated trafficking and efflux leading to cargoes becoming trapped inside cancer cells.

SIGNIFICANCE

Human trials have indicated that AS1411 is safe and can induce durable remissions in a few patients, but new strategies are needed to maximize its clinical impact. A better understanding of the mechanisms by which AS1411 targets and kills cancer cells may hasten the development of promising technologies using AS1411-linked nanoparticles or conjugates for cancer-targeted therapy and imaging. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.

G-quadruplex-based aptamers against protein targets in therapy and diagnostics

Nucleic acid aptamers are single-stranded DNA or RNA molecules identified to recognize with high affinity specific targets including proteins, small molecules, ions, whole cells and even entire organisms, such as viruses or bacteria. They can be identified from combinatorial libraries of DNA or RNA oligonucleotides by SELEX technology, an in vitro iterative selection procedure consisting of binding (capture), partitioning and amplification steps. Remarkably, many of the aptamers selected against biologically relevant protein targets are G-rich sequences that can fold into stable G-quadruplex (G4) structures. Aiming at disseminating novel inspiring ideas within the scientific community in the field of G4-structures, the emphasis of this review is placed on: 1) recent advancements in SELEX technology for the efficient and rapid identification of new candidate aptamers (introduction of microfluidic systems and next generation sequencing); 2) recurrence of G4 structures in aptamers selected by SELEX against biologically relevant protein targets; 3) discovery of several G4-forming motifs in important regulatory regions of the human or viral genome bound by endogenous proteins, which per se can result into potential aptamers; 4) an updated overview of G4-based aptamers with therapeutic potential and 5) a discussion on the most attractive G4-based aptamers for diagnostic applications. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.

A novel chemotherapy drug-free delivery system composed of three therapeutic aptamers for the treatment of prostate and breast cancers in vitro and in vivo

In this study, a novel chemotherapy drug-free DNA nanocomplex composed of three therapeutic aptamers (IDA, AS1411 and apMNK2F) was designed for treatment of cancer cells. For MTT assay, PC-3 and 4T1 cells (target cells) and CHO cells (nontarget cells) were treated with apMNK2F-AS1411-IDA complex (DNA nanocomplex), as well as AS1411, IDA and apMNK2F alone. Internalization of apMNK2F-AS1411-IDA complex was analyzed by fluorescence imaging and flow cytometry analysis. In the last step, the presented DNA nanocomplex was applied for prohibition of tumor growth in vivo. The results of internalization assay verified that the developed apMNK2F-AS1411-IDA complex was remarkably internalized into PC-3 and 4T1 cells, but not into CHO cells. The results of internalization assay was confirmed by MTT assay. apMNK2F-AS1411-IDA complex was more cytotoxic in PC-3 and 4T1 cells (target) and less cytotoxic in CHO cells (nontarget). Also, the DNA nanocomplex could effectively suppress the growth of tumors in vivo.

Structure, Properties, and Biological Relevance of the DNA and RNA G-Quadruplexes: Overview 50 Years after Their Discovery

G-quadruplexes (G4s), which are known to have important roles in regulation of key biological processes in both normal and pathological cells, are the most actively studied non-canonical structures of nucleic acids. In this review, we summarize the results of studies published in recent years that change significantly scientific views on various aspects of our understanding of quadruplexes. Modern notions on the polymorphism of DNA quadruplexes, on factors affecting thermodynamics and kinetics of G4 folding–unfolding, on structural organization of multiquadruplex systems, and on conformational features of RNA G4s and hybrid DNA–RNA G4s are discussed. Here we report the data on location of G4 sequence motifs in the genomes of eukaryotes, bacteria, and viruses, characterize G4-specific small-molecule ligands and proteins, as well as the mechanisms of their interactions with quadruplexes. New information on the structure and stability of G4s in telomeric DNA and oncogene promoters is discussed as well as proof being provided on the occurrence of G-quadruplexes in cells. Prominence is given to novel experimental techniques (single molecule manipulations, optical and magnetic tweezers, original chemical approaches, G4 detection in situ, in-cell NMR spectroscopy) that facilitate breakthroughs in the investigation of the structure and functions of G-quadruplexes.

The G-quadruplex-forming aptamer AS1411 potently inhibits HIV-1 attachment to the host cell

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The G-quadruplex-forming aptamer AS1411 strongly inhibits HIV-1 infection.

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AS1411 is non-toxic to the host cell at antiviral concentrations.

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AS1411 blocks viral attachment to the host cell.

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AS1411 binds cell-surface-expressed nucleolin, a putative HIV-1 co-receptor.

AS1411 is a G-rich aptamer that forms a stable G-quadruplex structure and displays antineoplastic properties both in vitro and in vivo. This oligonucleotide has undergone phase 2 clinical trials. The major molecular target of AS1411 is nucleolin (NCL), a multifunctional nucleolar protein also present in the cell membrane where it selectively mediates the binding and uptake of AS1411. Cell-surface NCL has been recognised as a low-affinity co-receptor for human immunodeficiency virus type 1 (HIV-1) anchorage on target cells. Here we assessed the anti-HIV-1 properties and underlying mechanism of action of AS1411. The antiviral activity of AS1411 was determined towards different HIV-1 strains, host cells and at various times post-infection. Acutely, persistently and latently infected cells were tested, including HIV-1-infected peripheral blood mononuclear cells from a healthy donor. Mechanistic studies to exclude modes of action other than virus binding via NCL were performed. AS1411 efficiently inhibited HIV-1 attachment/entry into the host cell. The aptamer displayed antiviral activity in the absence of cytotoxicity at the tested doses, therefore displaying a wide therapeutic window and favourable selectivity indexes. These findings, besides validating cell-surface-expressed NCL as an antiviral target, open the way for the possible use of AS1411 as a new potent and promisingly safe anti-HIV-1 agent.

Delivery, Effect on Cell Viability, and Plasticity of Modified Aptamer Constructs

AS1411 is a g-quadruplex-forming aptamer capable of selectively entering cancer cells by nucleolin receptor-mediated uptake. In this study, we investigated the cell internalization properties and plasticity of AS1411 carrying different locked nucleic acid-containing cargo oligonucleotides (ONs) for delivery into A549 and U2OS cells. We found that internalization efficiency is highly governed by ON cargo chemistry and composition since the inherent antitumor properties of AS1411 were lost when attached to a nontoxic ON, noTox. However, a toxic ON, Tox, demonstrated potent cytotoxicity after aptamer-mediated uptake in A549 cells. We also examined the effect of unlocked nucleic acid (UNA) modifications in the loop region of the aptamer, and how the cargo ONs and UNA incorporation affect the secondary structure of AS1411, in the presence or absence of two novel ellipticine derivatives. These findings add new insights to the design and future applications of aptamer-guided delivery of ON cargo to cancer cells.