Identification of TIM3 2'-fluoro oligonucleotide aptamer by HT-SELEX for cancer immunotherapy

RNA-encapsulating lipid nanoparticles in cancer immunotherapy: From pre-clinical studies to clinical trials

Nanoparticle-based delivery systems such as RNA-encapsulating lipid nanoparticles (RNA LNPs) have dramatically advanced in function and capacity over the last few decades. RNA LNPs boast of a diverse array of external and core configurations that enhance targeted delivery and prolong circulatory retention, advancing therapeutic outcomes. Particularly within the realm of cancer immunotherapies, RNA LNPs are increasingly gaining prominence. Pre-clinical in vitro and in vivo studies have laid a robust foundation for new and ongoing clinical trials that are actively enrolling patients for RNA LNP cancer immunotherapy. This review explores RNA LNPs, starting from their core composition to their external membrane formulation, set against a backdrop of recent clinical breakthroughs. We further elucidate the LNP delivery avenues, broach the prevailing challenges, and contemplate the future perspectives of RNA LNP-mediated immunotherapy.

Aptamers combined with immune checkpoints for cancer detection and targeted therapy: A review

In recent years, remarkable strides have been made in the field of immunotherapy, which has emerged as a standard treatment for many cancers. As a kind of immunotherapy drug, monoclonal antibodies employed in immune checkpoint therapy have proven beneficial for patients with diverse cancer types. However, owing to the extensive heterogeneity of clinical responses and the complexity and variability of the immune system and tumor microenvironment (TME), accurately predicting its efficacy remains a challenge. Recent advances in aptamers provide a promising approach for monitoring alterations within the immune system and TME, thereby facilitating targeted immunotherapy, particularly focused on immune checkpoint blockade, with enhanced antitumor efficiency. Aptamers have been widely used in tumor cell detection, biosensors, drug discovery, and biomarker screening due to their high specificity and high affinity with their targets. This review aims to comprehensively examine the research status and progress of aptamers in cancer diagnosis and immunotherapy, with a specific emphasis on those related to immune checkpoints. Additionally, we will discuss the future research directions and potential therapeutic targets for aptamer-based immune checkpoint therapy, aiming to provide a theoretical basis for targeting immunotherapy molecules and blocking tumor immune escape.

Immune checkpoint inhibitors and cancer immunotherapy by aptamers: an overview

Efforts in cancer immunotherapy aim to counteract evasion mechanisms and stimulate the immune system to recognise and attack cancer cells effectively. Combination therapies that target multiple aspects of immune evasion are being investigated to enhance the overall efficacy of cancer immunotherapy. PD-1 (Programmed Cell Death Protein 1), CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4), LAG-3 (Lymphocyte-Activation Gene 3), and TIM-3 (T Cell Immunoglobulin and Mucin Domain-Containing Protein3) are all immune checkpoint receptors that play crucial roles in regulating the immune response and maintaining self-tolerance often exploited by cancer cells to evade immune surveillance. Antibodies targeted against immune checkpoint inhibitors such as anti-PD-1 antibodies (e.g., pembrolizumab, nivolumab), anti-CTLA-4 antibodies (e.g., Ipilimumab), and experimental drugs targeting LAG-3 and TIM-3, aim to block these interactions and unleash the immune system's ability to recognise and destroy cancer cells. The US FDA has approved different categories of immune checkpoint inhibitors that have been utilised successfully in some patients with metastatic melanoma, renal cell carcinoma, head and neck cancers, and non-small lung cancer. Although several immune checkpoint inhibitor antibodies have been developed, they exhibited immune-related adverse effects, resulting in hypophysitis, diabetes, and neurological issues. These adverse effects of antibodies can be reduced by developing aptamer against the target. Aptamers offer several advantages over traditional antibodies, such as improved specificity, reduced immunogenicity, and flexible design for reduced adverse effects that specifically target and block protein-protein or receptor-ligand interactions involved in immune checkpoint pathways. The current study aims to review the function of particular immune checkpoint inhibitors along with developed aptamer-mediated antitumor cytotoxicity in cancer treatment.

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.

Aptamer-Based Immunotheranostic Strategies

The escape from immune surveillance is a hallmark of cancer progression. The classic immune checkpoint molecules PD-1, PD-L1, CTLA-4, LAG-3, TIM-3 novel ones are part of a sophisticated system of up- and downmodulation of the immune system, which is unregulated in cancer. In recent years, there have been remarkable advances in the development of targeting strategies, focused principally on immunotherapies aiming at blocking those molecules involved in the evasion of the immune system. However, there are still challenges to predicting their efficacy due to the wide heterogeneity of clinical responses. Thus, there is a need to develop new strategies, and theranostics has much to contribute in this field. Besides that, aptamers have emerged as promising molecules with the potential to generate a huge impact in the immunotheranostic field. They are single-stranded oligonucleotides with a unique self-folding tridimensional structure, with high affinity and specificity for the target. In particular, their small size and physicochemical characteristics make them a versatile tool for designing theranostic strategies. Here, we review the progress in theranostic strategies based on aptamers against immune checkpoints, and highlight the potential of those approaches.

Immune Checkpoint Inhibitors for Vaccine Improvements: Current Status and New Approaches

In recent years, the use of immune checkpoint inhibitors (ICIs) in combination with approved or experimental vaccines has proven to be a promising approach to improve vaccine immunogenicity and efficacy. This strategy seeks to overcome the immunosuppressive mechanisms associated with the vaccine response, thereby achieving increased immunogenicity and efficacy. Most of the information on the use of ICIs combined with vaccines derives from studies on certain anti-tumor vaccines combined with monoclonal antibodies (mAbs) against either cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), or programmed death-ligand 1 (PD-L1). However, over the past few years, emerging strategies to use new-generation ICIs as molecular adjuvants are paving the way for future advances in vaccine research. Here, we review the current state and future directions of the use of ICIs in experimental and clinical settings, including mAbs and alternative new approaches using antisense oligonucleotides (ASOs), small non-coding RNAs, aptamers, peptides, and other small molecules for improving vaccine efficacy. The scope of this review mainly includes the use of ICIs in therapeutic antitumor vaccines, although recent research on anti-infective vaccines will also be addressed.

Cancer immunomodulation using bispecific aptamers

Evasion of immune destruction is a major hallmark of cancer. Recent US Food and Drug Administration (FDA) approvals of various immunomodulating therapies underline the important role that reprogramming the immune system can play in combating this disease. However, a wide range of side effects still limit the therapeutic potential of immunomodulators, suggesting a need for more precise reagents with negligible off-target and on-target/off-tumor effects. Aptamers are single-chained oligonucleotides that bind their targets with high specificity and affinity owing to their three-dimensional (3D) structures, and they are one potential way to address this need. In particular, bispecific aptamers (bsApts) have been shown to induce artificial immune synapses that promote T cell activation and subsequent tumor cell lysis in various in vitro and in vivo pre-clinical models. We discuss these advances here, along with gaps in bsApt biology at both the cellular and resident tissue levels that should be addressed to accelerate their translation into the clinic. The broad application, minimal production cost, and relative lack of immunogenicity of bsApts give them some ideal qualities for manipulating the immune system. Building upon lessons from other novel therapies, bsApts could soon provide clinicians with an immunomodulating toolbox that is not only potent and efficacious but exercises a wide therapeutic index.

New Checkpoint Inhibitors on the Road: Targeting TIM-3 in Solid Tumors

PURPOSE OF REVIEW

Even though checkpoint inhibitors have become a recent milestone for the treatment of many different tumor types, eventually, most part of patients will develop resistance mechanisms and their disease will progress. New generations of checkpoint inhibitors, as the ones directed to TIM-3, are on research.

RECENT FINDINGS

TIM-3 expression has been associated with more advanced stages and shorter survival in several tumor types, due to its association with T-cell dysfunction, and has become an interesting target to explore. Early phase clinical trials with different anti-TIM-3 monoclonal antibodies have shown a safe toxicity profile, as cobolimab, LY3321367, or sabatolimab; however, the general antitumor activity remains to be determined and further investigations are needed. TIM-3 is implicated in resistance to immunotherapy due to its role in T cell exhaustion. However, the TIM-3 pathway is highly complex in terms of non-canonical signaling, broad expression by different immune cells and multiple ligands. Different anti-TIM-3 inhibitors are currently on research, either as monotherapy or in combination with other immunotherapies or chemotherapy, aiming to overcome resistance.

RNA-mediated immunotherapy regulating tumor immune microenvironment: next wave of cancer therapeutics

Accumulating research suggests that the tumor immune microenvironment (TIME) plays an essential role in regulation of tumor growth and metastasis. The cellular and molecular nature of the TIME influences cancer progression and metastasis by altering the ratio of immune- suppressive versus cytotoxic responses in the vicinity of the tumor. Targeting or activating the TIME components show a promising therapeutic avenue to combat cancer. The success of immunotherapy is both astounding and unsatisfactory in the clinic. Advancements in RNA-based technology have improved understanding of the complexity and diversity of the TIME and its effects on therapy. TIME-related RNA or RNA regulators could be promising targets for anticancer immunotherapy. In this review, we discuss the available RNA-based cancer immunotherapies targeting the TIME. More importantly, we summarize the potential of various RNA-based therapeutics clinically available for cancer treatment. RNA-dependent targeting of the TIME, as monotherapy or combined with other evolving therapeutics, might be beneficial for cancer patients’ treatment in the near future.

The Potential of Aptamer-Mediated Liquid Biopsy for Early Detection of Cancer

The early detection of cancer favors a greater chance of curative treatment and long-term survival. Exciting new technologies have been developed that can help to catch the disease early. Liquid biopsy is a promising non-invasive tool to detect cancer, even at an early stage, as well as to continuously monitor disease progression and treatment efficacy. Various methods have been implemented to isolate and purify bio-analytes in liquid biopsy specimens. Aptamers are short oligonucleotides consisting of either DNA or RNA that are capable of binding to target molecules with high specificity. Due to their unique properties, they are considered promising recognition ligands for the early detection of cancer by liquid biopsy. A variety of circulating targets have been isolated with high affinity and specificity by facile modification and affinity regulation of the aptamers. In this review, we discuss recent progress in aptamer-mediated liquid biopsy for cancer detection, its associated challenges, and its future potential for clinical applications.

Productive screening of single aptamers with ddPCR

Antibodies have now been widely used for clinical treatment of a number of tumors. However, there are serious problems associated with antibody therapy, such as potential interactions of antibodies with the immune system as well as long production cycles. Recently, aptamers have been found to function similar to antibodies in terms of affinity and specificity to certain proteins and are attracting much attention for their low immunogenicity, easy chemical synthesis, and efficient penetration into tissues due to their small size. However, how to access high affinity and selectivity aptamers efficiently for further analysis is still open to be resolved. Herein, an aptamer discovery method that combines the continuous flow ddPCR technology with cytometer sorting of beads is reported, such that we have obtained DNA aptamers binding specifically to PD-1 with an affinity of over 60-fold higher than that for the best-reported method.

Potential therapeutic targets in the tumor microenvironment of hepatocellular carcinoma: reversing the protumor effect of tumor-associated macrophages

In hepatocellular carcinoma patients, due to the microenvironmental specificity of liver, the tumor microenvironment exhibits high immunosuppression and drug resistance, resulting in excessive or insufficient responses to immunotherapy. The dynamic interactions between tumor cells and immune modulators in the TME significantly impact the occurrence and development of tumors, efficacy, and drug resistance, which can create a much more positive response to immunotherapy. Moreover, with the wide application of single-cell sequencing technology in the TME, increasing evidence shows an interaction network among cells. Sequencing results suggest that specific tumor-associated macrophages are a hub node, connecting different cell populations in the cell interaction network, and can could regulate tumor generation and antitumor immunity. This review focused on therapeutic targets that could be targeted to remodel the tumor microenvironment and reprogram the tumor-associated macrophage phenotype in hepatocellular carcinoma patients, thereby improving immunotherapeutic efficacy.

Targeting TIM-3 in solid tumors: innovations in the preclinical and translational realm and therapeutic potential

INTRODUCTION

Immune checkpoint inhibitors (ICIs) have shown a great therapeutic efficacy in cancer patients. However, a significant proportion of cancer patients remain unresponsive or show limited response. T cell immunoglobulin and mucin-domain containing protein-3 (TIM-3) is a co-inhibitory receptor expressed on various cell types and is involved in the attenuation of immune responses. TIM-3 and its ligands are highly expressed in various solid malignancies and some studies have reported its association with worse disease outcomes. Thus, targeting TIM-3 could be a promising therapeutic approach to treat cancer patients.

AREAS COVERED

This review describes the role of TIM-3 and its ligands in regulating anti-tumor immunity and their contribution to cancer progression. Moreover, this review focuses on the preclinical models and translational data from important studies published in PubMed till October 2020, which demonstrate the therapeutic benefits of targeting TIM-3 signaling.

EXPERT OPINION

Despite the promising data obtained from targeting TIM-3 in preclinical models, precise mechanisms underlying the anti-tumor effects of TIM-3 inhibition are not fully elucidated. Therefore, mechanistic studies are required to provide better insights into the anti-tumor effects of targeting TIM-3, and clinical data are necessary to determine the safety profiles and therapeutic efficacy of TIM-3 inhibition in cancer patients.

Aptamers, the Nucleic Acid Antibodies, in Cancer Therapy

The arrival of the monoclonal antibody (mAb) technology in the 1970s brought with it the hope of conquering cancers to the medical community. However, mAbs, on the whole, did not achieve the expected wonder in cancer therapy although they do have demonstrated successfulness in the treatment of a few types of cancers. In 1990, another technology of making biomolecules capable of specific binding appeared. This technique, systematic evolution of ligands by exponential enrichment (SELEX), can make aptamers, single-stranded DNAs or RNAs that bind targets with high specificity and affinity. Aptamers have some advantages over mAbs in therapeutic uses particularly because they have little or no immunogenicity, which means the feasibility of repeated use and fewer side effects. In this review, the general properties of the aptamer, the advantages and limitations of aptamers, the principle and procedure of aptamer production with SELEX, particularly the undergoing studies in aptamers for cancer therapy, and selected anticancer aptamers that have entered clinical trials or are under active investigations are summarized.

TIMs, TAMs, and PS- antibody targeting: implications for cancer immunotherapy

Immunotherapy for cancer is making impressive strides at improving survival of a subset of cancer patients. To increase the breadth of patients that benefit from immunotherapy, new strategies that combat the immunosuppressive microenvironment of tumors are needed. Phosphatidylserine (PS) signaling is exploited by tumors to enhance tumor immune evasion and thus strategies to inhibit PS-mediated immune suppression have potential to increase the efficacy of immunotherapy. PS is a membrane lipid that flips to the outer surface of the cell membrane during apoptosis and/or cell stress. Externalized PS can drive efferocytosis or engage PS receptors (PSRs) to promote local immune suppression. In the tumor microenvironment (TME) PS-mediated immune suppression is often termed apoptotic mimicry. Monoclonal antibodies (mAbs) targeting PS or PSRs have been developed and are in preclinical and clinical testing. The TIM (T-cell/transmembrane, immunoglobulin, and mucin) and TAM (Tyro3, AXL, and MerTK) family of receptors are PSRs that have been shown to drive PS-mediated immune suppression in tumors. This review will highlight the development of mAbs targeting PS, TIM-3 and the TAM receptors.

Aptamers: A Review of Their Chemical Properties and Modifications for Therapeutic Application

Aptamers are short, single-stranded oligonucleotides that bind to specific target molecules. The shape-forming feature of single-stranded oligonucleotides provides high affinity and excellent specificity toward targets. Hence, aptamers can be used as analogs of antibodies. In December 2004, the US Food and Drug Administration approved the first aptamer-based therapeutic, pegaptanib (Macugen), targeting vascular endothelial growth factor, for the treatment of age-related macular degeneration. Since then, however, no aptamer medication for public health has appeared. During these relatively silent years, many trials and improvements of aptamer therapeutics have been performed, opening multiple novel directions for the therapeutic application of aptamers. This review summarizes the basic characteristics of aptamers and the chemical modifications available for aptamer therapeutics.

Aptamer-iRNAs as Therapeutics for Cancer Treatment

Aptamers are single-stranded oligonucleotides (ssDNA or ssRNA) that bind and recognize their targets with high affinity and specificity due to their complex tertiary structure. Aptamers are selected by a method called SELEX (Systematic Evolution of Ligands by EXponential enrichment). This method has allowed the selection of aptamers to different types of molecules. Since then, many aptamers have been described for the potential treatment of several diseases including cancer. It has been described over the last few years that aptamers represent a very useful tool as therapeutics, especially for cancer therapy. Aptamers, thanks to their intrinsic oligonucleotide nature, present inherent advantages over other molecules, such as cell-based products. Owing to their higher tissue penetrability, safer profile, and targeting capacity, aptamers are likely to become a novel platform for the delivery of many different types of therapeutic cargos. Here we focus the review on interfering RNAs (iRNAs) as aptamer-based targeting delivered agents. We have gathered the most reliable information on aptamers as targeting and carrier agents for the specific delivery of siRNAs, shRNA, microRNAs, and antisense oligonucleotides (ASOs) published in the last few years in the context of cancer therapy.

Tim-3 expression and its role in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common tumors in the world, and its mortality is still on the rise. Limited treatments and low chemotherapy sensitivity of HCC make new therapeutic strategies urgently needed. With the rise of immune checkpoint blockade, anti-CTLA-4 antibodies and anti-PD-1 antibodies have shown therapeutic effects in various tumors. T cell immunoglobulin mucin-3 (Tim-3), a newly discovered immune checkpoint molecule, plays a major role in the development of HCC. Tim-3 can be used to evaluate the prognosis and therapeutic effects in HCC, and Tim-3 intervention has shown anti-tumor effects in preclinical experiments. This review summarizes findings regarding Tim-3 and HCC in recent years and discusses the rationale of Tim-3 as a therapeutic target for HCC.

Aptamer-based targeted therapy

Precision medicine holds great promise to harness genetic and epigenetic cues for targeted treatment of a variety of diseases, ranging from many types of cancers, neurodegenerative diseases, to cardiovascular diseases. The proteomic profiles resulting from the unique genetic and epigenetic signatures represent a class of relatively well accessible molecular targets for both interrogation (e.g., diagnosis, prognosis) and intervention (e.g., targeted therapy) of these diseases. Aptamers are promising for such applications by specific binding with cognate disease biomarkers. Nucleic acid aptamers are a class of DNA or RNA with unique three-dimensional conformations that allow them to specifically bind with target molecules. Aptamers can be relatively easily screened, reproducibly manufactured, programmably designed, and chemically modified for various biomedical applications, including targeted therapy. Aptamers can be chemically modified to resist enzymatic degradation or optimize their pharmacological behaviors, which ensured their chemical integrity and bioavailability under physiological conditions. In this review, we will focus on recent progress and discuss the challenges and opportunities in the research areas of aptamer-based targeted therapy in the forms of aptamer therapeutics and aptamer-drug conjugates (ApDCs).

TIM-3 is a potential prognostic marker for patients with solid tumors: A systematic review and meta-analysis

Accumulated studies have demonstrated the important role of T cell immunoglobulin- and mucin-domain-containing molecule-3 (TIM-3) in various solid tumors and indicated its correlation with patients’ survival. To further verify the prognostic significance of TIM-3 in cancer patients and its correlation with tumor, we performed this meta-analysis including seven studies searched from PubMed, Web of Science, and Embase till July 2016. A total of 869 patients were used to analyze the association between TIM-3 expression and patients’ overall survival (OS). The pooled results showed that higher expression of TIM-3 was significantly correlated to shorter OS (7 studies, HR=1.89; 95% CI: 1.38-2.57; P< 0.001). In addition, higher TIM-3 expression was associated with advanced tumor stage (3 studies, III/IV vs. I/II, RR=2.02; 95% CI: 1.45–2.81; P< 0.001). In conclusion, our study highlights the role of TIM-3 as a potential prognostic marker and a promising therapeutic target in solid tumors.

Aptamer Therapeutics in Cancer: Current and Future

Aptamer-related technologies represent a revolutionary advancement in the capacity to rapidly develop new classes of targeting ligands. Structurally distinct RNA and DNA oligonucleotides, aptamers mimic small, protein-binding molecules and exhibit high binding affinity and selectivity. Although their molecular weight is relatively small—approximately one-tenth that of monoclonal antibodies—their complex tertiary folded structures create sufficient recognition surface area for tight interaction with target molecules. Additionally, unlike antibodies, aptamers can be readily chemically synthesized and modified. In addition, aptamers’ long storage period and low immunogenicity are favorable properties for clinical utility. Due to their flexibility of chemical modification, aptamers are conjugated to other chemical entities including chemotherapeutic agents, siRNA, nanoparticles, and solid phase surfaces for therapeutic and diagnostic applications. However, as relatively small sized oligonucleotides, aptamers present several challenges for successful clinical translation. Their short plasma half-lives due to nuclease degradation and rapid renal excretion necessitate further structural modification of aptamers for clinical application. Since the US Food and Drug Administration (FDA) approval of the first aptamer drug, Macugen^® (pegaptanib), which treats wet-age-related macular degeneration, several aptamer therapeutics for oncology have followed and shown promise in pre-clinical models as well as clinical trials. This review discusses the advantages and challenges of aptamers and introduces therapeutic aptamers under investigation and in clinical trials for cancer treatments.

Genetic polymorphisms of immune checkpoint proteins PD-1 and TIM-3 are associated with survival of patients with hepatitis B virus-related hepatocellular carcinoma

Programmed cell death protein 1 (PD-1) and T-cell immunoglobulin domain and mucin domain containing molecule 3 (TIM-3) are involved in hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). This study examined the associations of PD1 and TIM3 polymorphisms with the overall survival (OS) of a prospective cohort of 258 HBV-related HCC patients. Results showed that PD1 +8669 G allele-containing genotypes or TIM3 −1516 genotype GG were significantly associated with longer OS (P < 0.001 and P = 0.001, respectively). In multivariate analysis, PD1 +8669 G allele-containing genotypes and TIM3 −1516 genotype GG were independently associated with longer OS (hazard ratio (HR), 1.835; 95% confidence interval (CI), 1.342–2.509; P < 0.001 and HR, 2.070; 95%CI, 1.428–3.002; P < 0.001, respectively). PD1 +8669 G allele-containing genotypes were significantly associated with longer OS in patients receiving surgical (resection or radiofrequency) treatment, transcatheter arterial chemoembolization (TACE) or supportive and symptomatic treatment. TIM3 −1516 genotype GG was significantly associated with longer OS in TACE patients. In multivariate analysis, PD1 +8669 G allele-containing genotypes were independently associated with longer OS in each treatment population. TIM3 −1516 genotype GG was independently associated with longer OS in patients receiving surgical treatment or TACE. These findings suggest that PD1 +8669 A/G and TIM3 −1516 G/T polymorphisms may affect the prognosis of HBV-related HCC and may be new predictors of prognosis for HCC patients.

Aptamer: A potential oligonucleotide nanomedicine in the diagnosis and treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers with a high mortality rate. Late diagnosis and poor prognosis are still a major drawback since curative therapies such as liver resection and liver transplantation are effective only for an early stage HCC. Development of novel molecular targeting therapies against HCC may provide new options that will improve the efficiency of the diagnosis and the success of the therapy, thus ameliorating the life expectancy of the patients. The aptamer is an oligonucleotide nanomedicine that has high binding affinity and specificity to small and large target molecules in the intracellular and extracellular environment with agonist or antagonist function. Currently, several aptamers for diagnostic and therapeutic purposes are under development to recognize different molecules of HCC. In in vitro models, the aptamer has been shown to be able to reduce the growth of HCC cells and increase the sensitivity to conventional chemotherapies. In in vivo mouse models, aptamer could induce cell apoptosis with antitumor activity. Overall data had shown that aptamer has limited toxicity and might be safe in clinical application. This review summarizes recent information of aptamer as a potential oligonucleotide nanomedicine tool, in diagnostics, targeted therapy, and as drug delivery nano-vehicles.

Identification of LAG3 high affinity aptamers by HT-SELEX and Conserved Motif Accumulation (CMA)

LAG3 receptor belongs to a family of immune-checkpoints expressed in T lymphocytes and other cells of the immune system. It plays an important role as a rheostat of the immune response. Focus on this receptor as a potential therapeutic target in cancer immunotherapy has been underscored after the success of other immune-checkpoint blockade strategies in clinical trials. LAG3 showcases the interest in the field of autoimmunity as several studies show that LAG3-targeting antibodies can also be used for the treatment of autoimmune diseases. In this work we describe the identification of a high-affinity LAG3 aptamer by High Throughput Sequencing SELEX in combination with a study of potential conserved binding modes according to sequence conservation by using 2D-structure prediction and 3D-RNA modeling using Rosetta. The aptamer with the highest accumulation of these conserved sequence motifs displays the highest affinity to LAG3 recombinant soluble proteins and binds to LAG3-expressing lymphocytes. The aptamer described herein has the potential to be used as a therapeutic agent, as it enhances the threshold of T-cell activation. Nonetheless, in future applications, it could also be engineered for treatment of autoimmune diseases by target depletion of LAG3-effector T lymphocytes.

Emerging cancer-specific therapeutic aptamers

PURPOSE OF REVIEW

We will describe recently discovered smart aptamers with tumor specificity, with an emphasis on targeted delivery of novel therapeutic molecules, cancer-specific biomarkers, and immunotherapy.

RECENT FINDINGS

The development of cancer-specific aptamers has facilitated targeted delivery of potent therapeutic molecules to cancer cells without harming nontumoral cells. This specificity also makes it possible to discover novel cancer biomarkers. Furthermore, alternative immune-checkpoint blockade aptamers have been developed for combinational immunotherapy.

SUMMARY

Aptamers selected against cancer cells show cancer specificity, which has great potential for targeting. First, functionalizing targeted aptamers with therapeutic molecule payloads (e.g., small activating RNAs, antimitotic drugs, therapeutic antibodies, and peptides) facilitates successful delivery into cancer cells. This approach greatly improves the therapeutic index by minimizing side-effects in nontumoral cells. Second, cancer-specific proteins have been identified as cancer biomarkers through in-vitro and in-vivo selection, aptamer pull-down assays, and mass spectrometry. These newly discovered biomarkers improve therapeutic intervention and diagnostic specificity. In addition, the development of alternative immune-checkpoint blockade aptamers is suggested for use in combinational immunotherapeutic with current immune blockade regimens, to reduce the resistance and exhaustion of T cells in clinical trials. VIDEO ABSTRACT: http://links.lww.com/COON/A21.

A TIM-3 Oligonucleotide Aptamer Enhances T Cell Functions and Potentiates Tumor Immunity in Mice

T cell immunoglobulin-3 (TIM-3) is a negative regulator of interferon-γ (IFN-γ) secreting CD4⁺ T cells and CD8⁺ T cytotoxic cells. Recent studies have highlighted the role of TIM-3 as an important mediator of CD8⁺ T cell exhaustion in the setting of chronic viral infections and cancer. In murine tumor models, antibody blockade of TIM-3 with anti-TIM-3 antibodies as monotherapy has no or minimal antitumor activity, suggesting that TIM-3 signaling exerts an accessory or amplifying effect in keeping immune responses in check. Using a combined bead and cell-based systemic evolution of ligands by exponential enrichment (SELEX) protocol, we have isolated nuclease-resistant oligonucleotide aptamer ligands that bind to cell-associated TIM-3 with high affinity and specificity. A trimeric form of the TIM-3 aptamer blocked the interaction of TIM-3 with Galectin-9, reduced cell death, and enhanced survival, proliferation, and cytokine secretion in vitro. In tumor-bearing mice, the aptamer delayed tumor growth as monotherapy and synergized with PD-1 antibody in prolonging the survival of the tumor-bearing mice. Both in vitro and in vivo, the trimeric aptamer displayed superior activity compared to the currently used RMT3-23 monoclonal antibody. This study suggests that multi-valent aptamers could represent an alternative platform to generate potent ligands to manipulate the function of TIM-3 and other immune modulatory receptors.

T-cell immunoglobulin mucin 3 blockade drives an antitumor immune response in head and neck cancer

T‐cell immunoglobulin mucin 3 (TIM3) contributes to immune suppression during progression of many cancers, but the precise role of TIM3 in head and neck squamous cell carcinoma (HNSCC) is not clearly understood. In this study, we report that TIM3 expression was significantly up‐regulated in patients with HNSCC and associated with lymph node metastasis. Additionally, TIM3 expression was increased in patients with recurrent HNSCC and patients with preradiotherapy or prechemotherapy. We also characterized CD8⁺ T cells and CD11b⁺CD33⁺ myeloid‐derived suppressor cells (MDSCs) in human HNSCC, and found that their expression was positively correlated with TIM3 expression. To determine the underlying mechanism of TIM3 in immune response during HNSCC progression, we utilized the Tgfbr1/Pten 2cKO HNSCC mouse model with TIM3 overexpression. Treatment with anti‐TIM3 monoclonal antibody effectively suppressed tumor growth through restoring effector T‐cell function by targeting CD4⁺TIM3⁺ cells and CD8⁺TIM3⁺ cells and decreasing MDSCs. Our findings demonstrate TIM3 expression in patients with HNSCC and suggest anti‐TIM3 immunotherapy as a novel therapeutic approach for effective treatment of HNSCC.

Co-expression of TIM-3 and CEACAM1 promotes T cell exhaustion in colorectal cancer patients

T-cell immunoglobulin domain and mucin domain-3(TIM-3) is an activation induced inhibitory molecule involved in immune tolerance and is recently reported to induce T cell exhaustion which is mediated by carcinoembryonic antigen cell adhesion molecule 1(CEACAM1), another well-known molecule expressed on activated T cells and involved in T cell inhibition. To investigate the expression of TIM-3 and CEACAM1 on circulating CD8⁺ T cells and tumor infiltrating lymphocytes (TILs), 65 diagnosed colorectal cancer (CRC) patients and 38 healthy controls were enrolled in this study and the results showed that TIM-3 and CEACAM1 were both highly expressed on circulating CD8⁺ T cells in CRC patients and elevated on TILs compared with paraneoplastic T cells. Furthermore, TIM-3⁺CEACAM1⁺ CD8⁺ T cells represented the most dysfunctional population with the least IFN-γ production. In addition, the expressions of TIM-3 and CEACAM1 were correlated with advanced stage and could be independent risk factors for CRC. We for the first time to our knowledge suggested that co-expression of TIM-3 and CEACAM1 can mediate T cell exhaustion and may be potential biomarkers for CRC prediction, highlighting the possibility of being immunotherapy targets.

Aptamers for CD Antigens: From Cell Profiling to Activity Modulation

Nucleic acid-based aptamers are considered to be a promising alternative to antibodies because of their strong and specific binding to diverse targets, fast and inexpensive chemical synthesis, and easy labeling with a fluorescent dye or therapeutic agent. Cluster of differentiation (CD) proteins are among the most popular antigens for aptamers on the cell surface. These anti-CD aptamers could be used in cell biology and biomedicine, from simple cell phenotyping by flow cytometry or fluorescent microscopy to diagnosis and treatment of HIV/AIDS to cancer and immune therapies. The unique feature of aptamers is that they can act simultaneously as an agonist and antagonist of CD receptors depending on a degree of aptamer oligomerization. Aptamers can also deliver small interfering RNA to silence vital genes in CD-positive cells. In this review, we summarize nucleic acid sequences of anti-CD aptamers and their use, which have been validated in multiple studies.

Immune checkpoint proteins PD-1 and TIM-3 are both highly expressed in liver tissues and correlate with their gene polymorphisms in patients with HBV-related hepatocellular carcinoma

Immune checkpoint proteins programmed death-1 (PD-1) and T-cell immunoglobulin domain and mucin domain containing molecule-3 (TIM-3) expression and their gene polymorphisms have separately been shown to be associated with hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC). This study simultaneously examined PD-1 and TIM-3 expression in liver tissues and PD1 and TIM3 polymorphisms and analyzed their correlations in 171 patients with HBV-related HCC and 34 patients with HBV-related cirrhosis.PD-1 and TIM-3 expression in liver tissues were examined by immunohistochemistry and the genotypes of PD1 rs10204525 and TIM3 rs10053538 polymorphisms were determined using genomic DNA extracted from peripheral blood as template.Both PD-1 and TIM-3 expressions in liver infiltrating lymphocytes of HCC tumor tissues were significantly higher than those in tumor adjacent tissues or cirrhotic tissues. The elevated PD-1 and TIM-3 expressions were significantly associated with higher tumor grades. The levels between PD-1 and TIM-3 expression in tumor tissues and tumor adjacent tissues had a significant positive intercorrelation. The expressions of PD-1 and TIM-3 in tumor tissues, tumor adjacent tissues, and cirrhotic tissues were significantly associated with PD1 and TIM3 polymorphisms, with genotype AA of PD1 rs10204525 and genotypes GT+TT of TIM3 rs10053538 being associated with significantly increased PD-1 and TIM-3 expression, respectively.These findings support the potential to improve the efficiency of immune checkpoint-targeted therapy and reduce resistance to the therapy by blocking both PD-1 and TIM-3 and suggest the potential to apply the genotype determination of PD1 rs10204525 and TIM3 rs10053538 as biomarkers of immune checkpoint-directed therapies.

Aptamers: A New Technological Platform in Cancer Immunotherapy

The renaissance of cancer immunotherapy is, nowadays, a reality. In the near future, it will be very likely among the first-line treatments for cancer patients. There are several different approaches to modulate the immune system to fight against tumor maladies but, so far, monoclonal antibodies may currently be the most successful immuno-tools used to that end. The number of ongoing clinical trials with monoclonal antibodies has been increasing exponentially over the last few years upon the Food and Drug Administration (FDA) approval of the first immune-checkpoint blockade antibodies. In spite of the proved antitumor effect of these reagents, the unleashing of the immune system to fight cancer cells has a cost, namely auto-inflammatory toxicity. Additionally, only a small fraction of all patients treated with immune-checkpoint antibodies have a clinical benefit. Taking into account all this, it is urgent new therapeutic reagents are developed with a contained toxicity that could facilitate the combination of different immune-modulating pathways to broaden the antitumor effect in most cancer patients. Based on preclinical data, oligonucleotide aptamers could fulfill this need. Aptamers have not only been successfully used as antagonists of immune-checkpoint receptors, but also as agonists of immunostimulatory receptors in cancer immunotherapy. The simplicity of aptamers to be engineered for the specific delivery of different types of cargos to tumor cells and immune cells so as to harvest an efficient antitumor immune response gives aptamers a significant advantage over antibodies. In this review all of the recent applications of aptamers in cancer immunotherapy will be described.

Cellular Delivery of RNA Nanoparticles

RNA nanostructures can be programmed to exhibit defined sizes, shapes and stoichiometries from naturally occurring or de novo designed RNA motifs. These constructs can be used as scaffolds to attach functional moieties, such as ligand binding motifs or gene expression regulators, for nanobiology applications. This review is focused on four areas of importance to RNA nanotechnology: the types of RNAs of particular interest for nanobiology, the assembly of RNA nanoconstructs, the challenges of cellular delivery of RNAs in vivo, and the delivery carriers that aid in the matter. The available strategies for the design of nucleic acid nanostructures, as well as for formulation of their carriers, make RNA nanotechnology an important tool in both basic research and applied biomedical science.

Aptamers: A Feasible Technology in Cancer Immunotherapy

Aptamers are single-chained RNA or DNA oligonucleotides (ODNs) with three-dimensional folding structures which allow them to bind to their targets with high specificity. Aptamers normally show affinities comparable to or higher than that of antibodies. They are chemically synthesized and therefore less expensive to manufacture and produce. A variety of aptamers described to date have been shown to be reliable in modulating immune responses against cancer by either blocking or activating immune receptors. Some of them have been conjugated to other molecules to target the immune system and reduce off-target side effects. Despite the success of first-line treatments against cancer, the elevated number of relapsing cases and the tremendous side effects shown by the commonly used agents hinder conventional treatments against cancer. The advantages provided by aptamers could enhance the therapeutic index of a given strategy and therefore enhance the antitumor effect. Here we recapitulate the provided benefits of aptamers with immunomodulatory activity described to date in cancer therapy and the benefits that aptamer-based immunotherapy could provide either alone or combined with first-line treatments in cancer therapy.