The Spiegelmer NOX-A12, a novel CXCL12 inhibitor, interferes with chronic lymphocytic leukemia cell motility and causes chemosensitization. Blood. 2014;123:1032-1039. [PMID: 24277076 DOI: 10.1182/blood-2013-03-493924]

The clinical potential of l-oligonucleotides: challenges and opportunities

Chemically modified nucleotides are central to the development of biostable research tools and oligonucleotide therapeutics. In this context, l-oligonucleotides, the synthetic enantiomer of native d-nucleic acids, hold great promise. As enantiomers, l-oligonucleotides share the same physical and chemical properties as their native counterparts, yet their inverted l-(deoxy)ribose sugars afford them orthogonality towards the stereospecific environment of biology. Notably, l-oligonucleotides are highly resistant to degradation by cellular nucleases, providing them with superior biostability. As a result, l-oligonucleotides are being increasingly utilized for the development of diverse biomedical technologies, including molecular imaging tools, diagnostic biosensors, and aptamer-based therapeutics. Herein, we present recent such examples that highlight the clinical potential of l-oligonucleotides. Additionally, we provide our perspective on the remaining challenges and practical considerations currently associated with the use of l-oligonucleotides and explore potential solutions that will lead to the broader adoption of l-oligonucleotides in clinical applications.

A Dual-Function LipoAraN-E5 Coloaded with N4-Myristyloxycarbonyl-1-β-d-arabinofuranosylcytosine (AraN) and a CXCR4 Antagonistic Peptide (E5) for Blocking the Dissemination of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a hematological malignancy with a high recurrence rate. The interaction of chemokine receptor 4/chemokine ligand 12 (CXCR4/CXCL12) mediates homing and adhesion of AML cells in bone marrow, leading to minimal residual disease in patients, which brings a hidden danger for future AML recurrence. Ara-C is a nonselective chemotherapeutic agent against AML. Due to its short half-life and severe side effects, a lipid-like Ara-C derivative (AraN) was synthesized and a dual-function LipoAraN-E5 (135 nm, encapsulation efficiency 99%) was developed, which coloaded AraN and E5, a peptide of the CXCR4 antagonist. LipoAraN-E5 effectively improved the uptake, enhanced the inhibition of leukemia cell proliferation, migration, and adhesion to stromal cells in bone marrow, and mobilized the leukemia cells from bone marrow to peripheral blood via interfering with the CXCR4/CXCL12 axis. LipoAraN-E5 prolonged the plasma half-life of AraN (8.31 vs 0.56 h) and was highly enriched in peripheral blood (3.67 vs 0.05 μmol/g at 8 h) and bone marrow (379 vs 148 μmol/g at 24 h). LipoAraN-E5 effectively prevented the infiltration of leukemia cells in peripheral blood, bone marrow, spleen, and liver, prolonged the mice survival, and showed outstanding antineoplastic efficacy with negligible toxicity, which were attributed to the ingenious design of AraN, the use of a liposomal delivery carrier, and the introduction of E5. Our work revealed that LipoAraN-E5 may be a promising nanocandidate against AML.

Recent Advances and Prospects of Nucleic Acid Therapeutics for Anti-Cancer Therapy

Nucleic acid therapeutics are promising alternatives to conventional anti-cancer therapy, such as chemotherapy and radiation therapy. While conventional therapies have limitations, such as high side effects, low specificity, and drug resistance, nucleic acid therapeutics work at the gene level to eliminate the cause of the disease. Nucleic acid therapeutics treat diseases in various forms and using different mechanisms, including plasmid DNA (pDNA), small interfering RNA (siRNA), anti-microRNA (anti-miR), microRNA mimics (miRNA mimic), messenger RNA (mRNA), aptamer, catalytic nucleic acid (CNA), and CRISPR cas9 guide RNA (gRNA). In addition, nucleic acids have many advantages as nanomaterials, such as high biocompatibility, design flexibility, low immunogenicity, small size, relatively low price, and easy functionalization. Nucleic acid therapeutics can have a high therapeutic effect by being used in combination with various nucleic acid nanostructures, inorganic nanoparticles, lipid nanoparticles (LNPs), etc. to overcome low physiological stability and cell internalization efficiency. The field of nucleic acid therapeutics has advanced remarkably in recent decades, and as more and more nucleic acid therapeutics have been approved, they have already demonstrated their potential to treat diseases, including cancer. This review paper introduces the current status and recent advances in nucleic acid therapy for anti-cancer treatment and discusses the tasks and prospects ahead.

Disulfide bond replacement with non-reducible side chain to tail macrolactamization for the development of potent and selective CXCR4 peptide antagonists endowed with flanking binding sites

The present study describes a small library of peptides derived from a potent and selective CXCR4 antagonist (3), wherein the native disulfide bond is replaced using a side-chain to tail macrolactamization technique to vary ring size and amino acid composition. The peptides were preliminary assessed for their ability to interfere with the interaction between the receptor and anti-CXCR4 PE-conjugated antibody clone 12G5. Two promising candidates (13 and 17) were identified and further evaluated in a125I-CXCL12 competition binding assay, exhibiting IC50 in the low-nanomolar range. Furthermore, both candidates displayed high selectivity towards CXCR4 with respect to the cognate receptor CXCR7, ability to block CXCL12-dependent cancer cell migration, and receptor internalization, albeit at a higher concentration compared to 3. Molecular modeling studies on 13 and 17 produced a theoretical model that may serve as a guide for future modifications, aiding in the development of analogs with improved affinity. Finally, the study provides valuable insights into developing therapeutic agents targeting CXCR4-mediated processes, demonstrating the adaptability of our lead peptide 3 to alternative cyclization approaches and offering prospects for comprehensive investigations into the receptor region's interaction with its C-terminal region.

Investigational CXCR4 inhibitors in early phase development for the treatment of hematological malignancies

INTRODUCTION

CXCR4/CXCL12 axis regulates cell proliferation, survival, and differentiation, as well as the homing and mobilization of hematopoietic stem cells (HSCs) from bone marrow niches to the peripheral blood. Furthermore, CXCR4 and CXCL12 are key mediators of cross-talk between hematological malignancies and their microenvironments. CXCR4 overexpression drives disease progression, boosts tumor cell survival, and promotes chemoresistance, leading to poor prognosis.

AREAS COVERED

In light of these discoveries, scientific investigations, and clinical trials have underscored the therapeutic promise found in small-molecule antagonists like plerixafor, peptides/peptidomimetics, such as BKT140, monoclonal antibodies like PF-06747143 and ulocuplumab, as well as microRNAs. Their efficacy is evident in reducing tumor burden, inducing apoptosis and sensitizing malignant cells to conventional chemotherapies. This overview delves into the pathogenic role of the CXC4/CXCL12 axis in hematological neoplasms and examines the clinical application of key CXCR4 antagonists.

EXPERT OPINION

The information collectively emphasizes the potential of CXCR4 antagonists as a therapeutic strategy for hematologic malignancies, showcasing advancements in preclinical and clinical studies. As these therapeutic strategies progress through clinical trials, their potential to reshape the prognosis of hematologic malignancies will become increasingly apparent.

Non-dialyzable uremic toxins and renal tubular cell damage in CKD patients: a systems biology approach

BACKGROUND

Chronic kidney disease presents global health challenges, with hemodialysis as a common treatment. However, non-dialyzable uremic toxins demand further investigation for new therapeutic approaches. Renal tubular cells require scrutiny due to their vulnerability to uremic toxins.

METHODS

In this study, a systems biology approach utilized transcriptomics data from healthy renal tubular cells exposed to healthy and post-dialysis uremic plasma.

RESULTS

Differential gene expression analysis identified 983 up-regulated genes, including 70 essential proteins in the protein-protein interaction network. Modularity-based clustering revealed six clusters of essential proteins associated with 11 pathological pathways activated in response to non-dialyzable uremic toxins.

CONCLUSIONS

Notably, WNT1/11, AGT, FGF4/17/22, LMX1B, GATA4, and CXCL12 emerged as promising targets for further exploration in renal tubular pathology related to non-dialyzable uremic toxins. Understanding the molecular players and pathways linked to renal tubular dysfunction opens avenues for novel therapeutic interventions and improved clinical management of chronic kidney disease and its complications.

Targeting cytokine and chemokine signaling pathways for cancer therapy

Cytokines are critical in regulating immune responses and cellular behavior, playing dual roles in both normal physiology and the pathology of diseases such as cancer. These molecules, including interleukins, interferons, tumor necrosis factors, chemokines, and growth factors like TGF-β, VEGF, and EGF, can promote or inhibit tumor growth, influence the tumor microenvironment, and impact the efficacy of cancer treatments. Recent advances in targeting these pathways have shown promising therapeutic potential, offering new strategies to modulate the immune system, inhibit tumor progression, and overcome resistance to conventional therapies. In this review, we summarized the current understanding and therapeutic implications of targeting cytokine and chemokine signaling pathways in cancer. By exploring the roles of these molecules in tumor biology and the immune response, we highlighted the development of novel therapeutic agents aimed at modulating these pathways to combat cancer. The review elaborated on the dual nature of cytokines as both promoters and suppressors of tumorigenesis, depending on the context, and discussed the challenges and opportunities this presents for therapeutic intervention. We also examined the latest advancements in targeted therapies, including monoclonal antibodies, bispecific antibodies, receptor inhibitors, fusion proteins, engineered cytokine variants, and their impact on tumor growth, metastasis, and the tumor microenvironment. Additionally, we evaluated the potential of combining these targeted therapies with other treatment modalities to overcome resistance and improve patient outcomes. Besides, we also focused on the ongoing research and clinical trials that are pivotal in advancing our understanding and application of cytokine- and chemokine-targeted therapies for cancer patients.

Cell-SELEX and application research of a DNA aptamer against esophageal squamous cell carcinoma (ESCC) cell line TE-1

Esophageal cancer is a common cancer with high morbidity and mortality that severely threatens the safety and quality of human life. The strong metastatic nature of esophageal cancer enables it to metastasize more quickly and covertly, making it difficult for current diagnostic and treatment methods to achieve efficient early screening, as well as timely and effective treatment. As a promising solution, nucleic acid aptamers, a kind of special single-stranded DNA or RNA oligonucleotide selected by the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technology, can specifically bind with different molecular targets. In this paper, random DNA single-stranded oligonucleotides were used as the initial library. Using TE-1 cells and HEEC cells as targets, specific binding sequences were selected by 15 rounds of the cell-SELEX method, and the aptamer sequence that binds to TE-1 cells with the most specificity was obtained and named Te4. The Te4 aptamer was further validated for binding specificity, binding affinity, type of target, in vitro cytotoxicity when conjugated with DOX(Te4-DOX), and in vivo distribution. Results of in vitro validation showed that Te4 has outstanding binding specificity with a Kd value of 51.16 ± 5.52 nM, and the target type of Te4 was preliminarily identified as a membrane protein. Furthermore, the cytotoxicity experiment showed that Te4-DOX has specific cytotoxicity towards cultured TE-1 cells. Finally, the results of the in vivo distribution experiment showed that the Te4 aptamer is able to specifically target tumor regions in nude mice, showing great potential to be applied in future diagnosis and targeted therapy of esophageal cancer.

Therapeutic Applications of Aptamers

Affinity reagents, or target-binding molecules, are quite versatile and are major workhorses in molecular biology and medicine. Antibodies are the most famous and frequently used type and they have been used for a wide range of applications, including laboratory techniques, diagnostics, and therapeutics. However, antibodies are not the only available affinity reagents and they do have significant drawbacks, including laborious and costly production. Aptamers are one potential alternative that have a variety of unique advantages. They are single stranded DNA or RNA molecules that can be selected for binding to many targets including proteins, carbohydrates, and small molecules-for which antibodies typically have low affinity. There are also a variety of cost-effective methods for producing and modifying nucleic acids in vitro without cells, whereas antibodies typically require cells or even whole animals. While there are also significant drawbacks to using aptamers in therapeutic applications, including low in vivo stability, aptamers have had success in clinical trials for treating a variety of diseases and two aptamer-based drugs have gained FDA approval. Aptamer development is still ongoing, which could lead to additional applications of aptamer therapeutics, including antitoxins, and combinatorial approaches with nanoparticles and other nucleic acid therapeutics that could improve efficacy.

L-RNA aptamer-based CXCL12 inhibition combined with radiotherapy in newly-diagnosed glioblastoma: dose escalation of the phase I/II GLORIA trial

The chemokine CXCL12 promotes glioblastoma (GBM) recurrence after radiotherapy (RT) by facilitating vasculogenesis. Here we report outcomes of the dose-escalation part of GLORIA (NCT04121455), a phase I/II trial combining RT and the CXCL12-neutralizing aptamer olaptesed pegol (NOX-A12; 200/400/600 mg per week) in patients with incompletely resected, newly-diagnosed GBM lacking MGMT methylation. The primary endpoint was safety, secondary endpoints included maximum tolerable dose (MTD), recommended phase II dose (RP2D), NOX-A12 plasma levels, topography of recurrence, tumor vascularization, neurologic assessment in neuro-oncology (NANO), quality of life (QOL), median progression-free survival (PFS), 6-months PFS and overall survival (OS). Treatment was safe with no dose-limiting toxicities or treatment-related deaths. The MTD has not been reached and, thus, 600 mg per week of NOX-A12 was established as RP2D for the ongoing expansion part of the trial. With increasing NOX-A12 dose levels, a corresponding increase of NOX-A12 plasma levels was observed. Of ten patients enrolled, nine showed radiographic responses, four reached partial remission. All but one patient (90%) showed at best response reduced perfusion values in terms of relative cerebral blood volume (rCBV). The median PFS was 174 (range 58-260) days, 6-month PFS was 40.0% and the median OS 389 (144-562) days. In a post-hoc exploratory analysis of tumor tissue, higher frequency of CXCL12+ endothelial and glioma cells was significantly associated with longer PFS under NOX-A12. Our data imply safety of NOX-A12 and its efficacy signal warrants further investigation.

The Application of Aptamer and Research Progress in Liver Disease

Aptamers, as a kind of small-molecule nucleic acid, have attracted much attention since their discovery. Compared with biological reagents such as antibodies, aptamers have the advantages of small molecular weight, low immunogenicity, low cost, and easy modification. At present, aptamers are mainly used in disease biomarker discovery, disease diagnosis, treatment, and targeted drug delivery vectors. In the process of screening and optimizing aptamers, it is found that there are still many problems need to be solved such as the design of the library, optimization of screening conditions, the truncation of screened aptamer, and the stability and toxicity of the aptamer. In recent years, the incidence of liver-related diseases is increasing year by year and the treatment measures are relatively lacking, which has attracted the people's attention in the application of aptamers in liver diseases. This article mainly summarizes the research status of aptamers in disease diagnosis and treatment, especially focusing on the application of aptamers in liver diseases, showing the crucial significance of aptamers in the diagnosis and treatment of liver diseases, and the use of Discovery Studio software to find the binding target and sequence of aptamers, and explore their possible interaction sites.

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.

Aptamer-based therapy for fighting biofilm-associated infections

Biofilms are key players in the pathogenesis of most of chronic infections associated with host tissue or fluids and indwelling medical devices. These chronic infections are hard to be treated due to the increased biofilms tolerance towards antibiotics in comparison to planktonic (or free living) cells. Despite the advanced understanding of their formation and physiology, biofilms continue to be a challenge and there is no standardized therapeutic approach in clinical practice to eradicate them. Aptamers offer distinctive properties, including excellent affinity, selectivity, stability, making them valuable tools for therapeutic purposes. This review explores the flexibility and designability of aptamers as antibiofilm drugs but, importantly, as targeting tools for diverse drug and delivery systems. It highlights specific examples of application of aptamers in biofilms of diverse species according to different modes of action including inhibition of motility and adhesion, blocking of quorum sensing molecules, and dispersal of biofilm-cells to planktonic state. Moreover, it discusses the limitations and challenges that impaired an increased success of the use of aptamers on biofilm management, as well as the opportunities related to aptamers modifications that can significantly expand their applicability on the biofilm field.

Deciphering the Synthetic and Refolding Strategy of a Cysteine-Rich Domain in the Tumor Necrosis Factor Receptor (TNF-R) for Racemic Crystallography Analysis and d-Peptide Ligand Discovery

Many cell-surface receptors are promising targets for chemical synthesis because of their critical roles in disease development. This synthetic approach enables investigations by racemic protein crystallography and ligand discovery by mirror-image methodologies. However, due to their complex nature, the chemical synthesis of a receptor can be a significant challenge. Here, we describe the chemical synthesis and folding of a central, cysteine-rich domain of the cell-surface receptor tumor necrosis factor 1 which is integral to binding of the cytokine TNF-α, namely, TNFR-1 CRD2. Racemic protein crystallography at 1.4 Å confirmed that the native binding conformation was preserved, and TNFR-1 CRD2 maintained its capacity to bind to TNF-α (KD ≈ 7 nM). Encouraged by this discovery, we carried out mirror-image phage display using the enantiomeric receptor mimic and identified a d-peptide ligand for TNFR-1 CRD2 (KD = 1 μM). This work demonstrated that cysteine-rich domains, including the central domains, can be chemically synthesized and used as mimics for investigations.

Stromal bone marrow fibroblasts and mesenchymal stem cells support acute myeloid leukaemia cells and promote therapy resistance

The bone marrow (BM) is the primary site of adult haematopoiesis, where stromal elements (e.g. fibroblasts and mesenchymal stem cells [MSCs]) work in concert to support blood cell development. However, the establishment of an abnormal clone can lead to a blood malignancy, such as acute myeloid leukaemia (AML). Despite our increased understanding of the pathophysiology of the disease, patient survival remains suboptimal, mainly driven by the development of therapy resistance. In this review, we highlight the importance of bone marrow fibroblasts and MSCs in health and acute myeloid leukaemia and their impact on patient prognosis. We discuss how stromal elements reduce the killing effects of therapies via a combination of contact-dependent (e.g. integrins) and contact-independent (i.e. secreted factors) mechanisms, accompanied by the establishment of an immunosuppressive microenvironment. Importantly, we underline the challenges of therapeutically targeting the bone marrow stroma to improve acute myeloid leukaemia patient outcomes, due to the inherent heterogeneity of stromal cell populations. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

Advances in targeted therapy for pancreatic cancer

Pancreatic cancer (PC) represents a group of malignant tumours originating from pancreatic duct epithelial cells and acinar cells, and the 5-year survival rate of PC patients is only approximately 12%. Molecular targeted drugs are specific drugs designed to target and block oncogenes, and they have become promising strategies for the treatment of PC. Compared to traditional chemotherapy drugs, molecular targeted drugs have greater targeting precision, and they have significant therapeutic effects and minimal side effects. This article reviews several molecular targeted drugs that are currently in the experimental stage for the treatment of PC; these include antibody-drug conjugates (ADCs), aptamer-drug conjugates (ApDCs) and peptide-drug conjugates (PDCs). ADCs can specifically recognize cell surface antigens and reduce systemic exposure and toxicity of chemotherapy drugs. By delivering nucleic acid drugs to target cells, the targeting RNA of ApDCs can inhibit the expression or translation of mutated genes, thereby inhibiting tumour development. Moreover, PDCs can effectively penetrate tumour cells, and the peptide groups in PDCs preferentially target tumour cells with minimal side effects. In the targeted therapy of PC, molecular targeted drugs have very broad prospects, which provides new hope for the clinical treatment of PC patients and is worth further research.

CXC chemokine receptor 4 (CXCR4) blockade in cancer treatment

CXC chemokine receptor type 4 (CXCR4) is a member of the G protein-coupled receptors (GPCRs) superfamily and is specific for CXC chemokine ligand 12 (CXCL12, also known as SDF-1), which makes CXCL12/CXCR4 axis. CXCR4 interacts with its ligand, triggering downstream signaling pathways that influence cell proliferation chemotaxis, migration, and gene expression. The interaction also regulates physiological processes, including hematopoiesis, organogenesis, and tissue repair. Multiple evidence revealed that CXCL12/CXCR4 axis is implicated in several pathways involved in carcinogenesis and plays a key role in tumor growth, survival, angiogenesis, metastasis, and therapeutic resistance. Several CXCR4-targeting compounds have been discovered and used for preclinical and clinical cancer therapy, most of which have shown promising anti-tumor activity. In this review, we summarized the physiological signaling of the CXCL12/CXCR4 axis and described the role of this axis in tumor progression, and focused on the potential therapeutic options and strategies to block CXCR4.

Complexation of drug and hapten-conjugated aptamer with universal hapten antibody for pancreatic cancer treatment

Owing to a lack of reliable markers and therapeutic targets, pancreatic ductal adenocarcinoma (PDAC) remains the most lethal malignant tumor despite numerous therapeutic advances. In this study, we utilized cell-SELEX to isolate a DNA aptamer recognizing the natural conformation of the target on the cell surface. PAp7T8, an aptamer optimized by size and chemical modification, exhibited specific targeting to pancreatic cancer cells and orthotopic xenograft pancreatic tumors. To confer therapeutic functions to the aptamer, we adopted a drug-conjugated oligobody (DOligobody) strategy. Monomethyl auristatin E was used as a cytotoxic drug, digoxigenin acted as a hapten, and the humanized anti-digoxigenin antibody served as a universal carrier of the aptamer. The resulting PAp7T8-DOligobody showed extended in vivo half-life and markedly inhibited tumor growth in an orthotopic pancreatic cancer xenograft model without causing significant toxicity. Therefore, PAp7T8-DOligobody represents a promising novel therapeutic delivery platform for PDAC.

Exploring the Potential of Aptamers in Targeting Neuroinflammation and Neurodegenerative Disorders: Opportunities and Challenges

Neuroinflammation is the precursor for several neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Targeting neuroinflammation has emerged as a promising strategy to address a wide range of CNS pathologies. These NDDs still present significant challenges in terms of limited and ineffective diagnosis and treatment options, driving the need to explore innovative and novel therapeutic alternatives. Aptamers are single-stranded nucleic acids that offer the potential for addressing these challenges through diagnostic and therapeutic applications. In this review, we summarize diagnostic and therapeutic aptamers for inflammatory biomolecules, as well as the inflammatory cells in NDDs. We also discussed the potential of short nucleotides for Aptamer-Based Targeted Brain Delivery through their unique features and modifications, as well as their ability to penetrate the blood-brain barrier. Moreover, the unprecedented opportunities and substantial challenges of using aptamers as therapeutic agents, such as drug efficacy, safety considerations, and pharmacokinetics, are also discussed. Taken together, this review assesses the potential of aptamers as a pioneering approach for target delivery to the CNS and the treatment of neuroinflammation and NDDs.

CXCL12-CXCR4/CXCR7 Axis in Cancer: from Mechanisms to Clinical Applications

Cancer is a multi-step disease caused by the accumulation of genetic mutations and/or epigenetic changes, and is the biggest challenge around the world. Cytokines, including chemokines, exhibit expression changes and disorders in all human cancers. These cytokine abnormalities can disrupt homeostasis and immune function, and make outstanding contributions to various stages of cancer development such as invasion, metastasis, and angiogenesis. Chemokines are a superfamily of small molecule chemoattractive cytokines that mediate a variety of cellular functions. Importantly, the interactions of chemokine members CXCL12 and its receptors CXCR4 and CXCR7 have a broad impact on tumor cell proliferation, survival, angiogenesis, metastasis, and tumor microenvironment, and thus participate in the onset and development of many cancers including leukemia, breast cancer, lung cancer, prostate cancer and multiple myeloma. Therefore, this review aims to summarize the latest research progress and future challenges regarding the role of CXCL12-CXCR4/CXCR7 signaling axis in cancer, and highlights the potential of CXCL12-CXCR4/CXCR7 as a biomarker or therapeutic target for cancer, providing essential strategies for the development of novel targeted cancer therapies.

Emerging Progress of RNA-Based Antitumor Therapeutics

RNA-based therapeutics (e.g., mRNAs, siRNAs, microRNAs, ASOs, and saRNAs) have considerable potential for tumor treatment. The development and optimization of RNA modifications and delivery systems enable the stable and efficient delivery of RNA cargos in vivo to elicit an antitumor response. Targeted RNA-based therapeutics with multiple specificities and high efficacies are now available. In this review, we discuss progress in RNA-based antitumor therapeutics, including mRNAs, siRNAs, miRNAs, ASOs, saRNAs, RNA aptamers, and CRISPR-based gene editing. We focus on the immunogenicity, stability, translation efficiency, and delivery of RNA drugs, and summarize their optimization and the development of delivery systems. In addition, we describe the mechanisms by which RNA-based therapeutics induce antitumor responses. Furthermore, we review the merits and limitations of RNA cargos and their therapeutic potential for cancers.

Physical biomarkers for human hematopoietic stem and progenitor cells

Adhesion of hematopoietic stem and progenitor cells (HSPCs) to the bone marrow niche plays critical roles in the maintenance of the most primitive HSPCs. The interactions of HSPC-niche interactions are clinically relevant in acute myeloid leukemia (AML), because (i) leukemia-initiating cells adhered to the marrow niche are protected from the cytotoxic effect by chemotherapy and (ii) mobilization of HSPCs from healthy donors' bone marrow is crucial for the effective stem cell transplantation. However, although many clinical agents have been developed for the HSPC mobilization, the effects caused by the extrinsic molecular cues were traditionally evaluated based on phenomenological observations. This review highlights the recent interdisciplinary challenges of hematologists, biophysicists and cell biologists towards the design of defined in vitro niche models and the development of physical biomarkers for quantitative indexing of differential effects of clinical agents on human HSPCs.

Aptamers in cancer therapy: problems and new breakthroughs

Aptamers, a class of oligonucleotides that can bind with molecular targets with high affinity and specificity, have been widely applied in research fields including biosensing, imaging, diagnosing, and therapy of diseases. However, compared with the rapid development in the research fields, the clinical application of aptamers is progressing at a much slower speed, especially in the therapy of cancer. Obstructions including nuclease degradation, renal clearance, a complex selection process, and potential side effects have inhibited the clinical transformation of aptamer-conjugated drugs. To overcome these problems, taking certain measures to improve the biocompatibility and stability of aptamer-conjugated drugs in vivo is necessary. In this review, the obstructions mentioned above are thoroughly discussed and the methods to overcome these problems are introduced in detail. Furthermore, landmark research works and the most recent studies on aptamer-conjugated drugs for cancer therapy are also listed as examples, and the future directions of research for aptamer clinical transformation are discussed.

The Research Advances of Aptamers in Hematologic Malignancies

Currently, research for hematological malignancies is very intensive, with many breakthroughs. Among them, aptamer-based targeted therapies could be counted. Aptamer is a targeting tool with many unique advantages (easy synthesis, low toxicity, easy modification, low immunogenicity, nano size, long stability, etc.), therefore many experts screened corresponding aptamers in various hematological malignancies for diagnosis and treatment. In this review, we try to summarize and provide the recent progress of aptamer research in the diagnosis and treatment of hematologic malignancies. Until now, 29 aptamer studies were reported in hematologic malignancies, of which 12 aptamers were tested in vivo and the remaining 17 aptamers were only tested in vitro. In this case, 11 aptamers were combined with chemotherapeutic drugs for the treatment of hematologic malignancies, 4 aptamers were used in combination with nanomaterials for the diagnosis and treatment of hematologic malignancies, and some studies used aptamers for the targeted transportation of siRNA and miRNA for targeted therapeutic effects. Their research provides multiple approaches to achieve more targeted goals. These findings show promising and encouraging future for both hematological malignancies basic and clinical trials research.

Aptamers Enhance Oncolytic Viruses' Antitumor Efficacy

Oncolytic viruses are highly promising for cancer treatment because they target and lyse tumor cells. These genetically engineered vectors introduce therapeutic or immunostimulatory genes into the tumor. However, viral therapy is not always safe and effective. Several problems are related to oncolytic viruses' targeted delivery to the tumor and immune system neutralization in the bloodstream. Cryoprotection and preventing viral particles from aggregating during storage are other critical issues. Aptamers, short RNA, or DNA oligonucleotides may help to crawl through this bottleneck. They are not immunogenic, are easily synthesized, can be chemically modified, and are not very demanding in storage conditions. It is possible to select an aptamer that specifically binds to any target cell, oncolytic virus, or molecule using the SELEX technology. This review comprehensively highlights the most important research and methodological approaches related to oncolytic viruses and nucleic acid aptamers. Here, we also analyze possible future research directions for combining these two methodologies to improve the effectiveness of cancer virotherapy.

Cimigenol depresses acute myeloid leukemia cells protected by breaking bone marrow stromal cells via CXCR4/SDF‑1α

The purpose of the present study was to evaluate cimigenol (Cim) treatment effects to cell proliferation by breaking bone marrow stromal cells (BMSCs) through C-X-C chemokine receptor type 4 (CXCR4)/stromal cell-derived factor-1α (SDF-1α) pathway. MV-4-11 and U937 cell lines were used. The present study was divided into two parts. First, the cell lines were divided into normal control (NC), BMSC (cells co-cultured with BMSCs), BMSC + DMSO, BMSC + Low (treated with 5 mg/ml Cim), BMSC + Middle (treated with 10 mg/ml Cim), BMSC + High (treated with 20 mg/ml Cim). In the second step, the cell lines were divided into NC, BMSC, BMSC + BL8040 (treated with BL8040 which inhibits CXCR4), BMSC + Cim and BMSC + Cim + BL8040. EdU positive cell numbers were measured by EdU assay and apoptosis rate by flow cytometry and TUNEL assay. Relative gene and protein expression was measured by reverse transcription-quantitative PCR and western blotting assay. BMSCs were able to protect proliferation of cancer cells and decreased cell apoptosis compared with the NC group (P<0.001, respectively). With Cim supplement, the cell proliferation was decreased with cell apoptosis increasing compared with NC group (P<0.001 respectively). However, the anti-tumor effects of Cim were not significantly different from the BL8040 treated groups (P<0.001, respectively). In conclusion Cim decreased acute myeloid leukemia cells protected by BMSCs through the CXCR4/SDF-1α pathway.

The prospect of tumor microenvironment-modulating therapeutical strategies

Multiple mechanisms promote tumor prosperity, which does not only depend on cell-autonomous, inherent abnormal characteristics of the malignant cells that facilitate rapid cell division and tumor expansion. The neoplastic tissue is embedded in a supportive and dynamic tumor microenvironment (TME) that nurtures and protects the malignant cells, maintaining and perpetuating malignant cell expansion. The TME consists of different elements, such as atypical vasculature, various innate and adaptive immune cells with immunosuppressive or pro-inflammatory properties, altered extracellular matrix (ECM), activated stromal cells, and a wide range of secreted/stroma-tethered bioactive molecules that contribute to malignancy, directly or indirectly. In this review, we describe the various TME components and provide examples of anti-cancer therapies and novel drugs under development that aim to target these components rather than the intrinsic processes within the malignant cells. Combinatory TME-modulating therapeutic strategies may be required to overcome the resistance to current treatment options and prevent tumor recurrence.

Discovery of Chemokine CXCL12 Inhibitors by Tandem Application of Virtual Screening and NMR Spectrometry

The CXC chemokine ligand CXCL12 and its receptor CXCR4 play critical roles in stem-cell homing, infectious diseases, and cancer, which led the CXCL12/CXCR4 signaling axis to attract much attention in drug discovery. CXCR4 is regarded as the primary target while CXCL12 is considered too small to be a druggable target. In this paper, we employed virtual screening approaches and ligand-based NMR screening methods from a SPECS library and in-house natural products to discover new CXCR12 inhibitors. Four natural triterpene saponins were confirmed, and the triterpene sapogenin was identified as the main binding epitope by saturation transfer difference-nuclear magnetic resonance and molecular docking studies. The pentacyclic triterpene scaffold and its elucidated structure-activity relationships provide a new and valuable research direction for the development of novel CXCL12 inhibitors.

Aptamer-Based Probes for Cancer Diagnostics and Treatment

Aptamers are single-stranded DNA or RNA oligomers that have the ability to generate unique and diverse tertiary structures that bind to cognate molecules with high specificity. In recent years, aptamer researches have witnessed a huge surge, owing to its unique properties, such as high specificity and binding affinity, low immunogenicity and toxicity, and simplicity of synthesis with negligible batch-to-batch variation. Aptamers may bind to targets, such as various cancer biomarkers, making them applicable for a wide range of cancer diagnosis and treatment. In cancer diagnostic applications, aptamers are used as molecular probes instead of antibodies. They have the potential to detect various cancer-associated biomarkers. For cancer therapeutic purposes, aptamers can serve as therapeutic or delivery agents. The chemical stabilization and modification strategies for aptamers may expand their serum half-life and shelf life. However, aptamer-based probes for cancer diagnosis and therapy still face several challenges for successful clinical translation. A deeper understanding of nucleic acid chemistry, tissue distribution, and pharmacokinetics is required in the development of aptamer-based probes. This review summarizes their application in cancer diagnostics and treatments based on different localization of target biomarkers, as well as current challenges and future prospects.

Aptamers, a New Therapeutic Opportunity for the Treatment of Multiple Myeloma

Multiple Myeloma (MM) remains an incurable disease due to high relapse rates and fast development of drug resistances. The introduction of monoclonal antibodies (mAb) has caused a paradigm shift in MM treatment, paving the way for targeted approaches with increased efficacy and reduced toxicities. Nevertheless, antibody-based therapies face several difficulties such as high immunogenicity, high production costs and limited conjugation capacity, which we believe could be overcome by the introduction of nucleic acid aptamers. Similar to antibodies, aptamers can bind to their targets with great affinity and specificity. However, their chemical nature reduces their immunogenicity and production costs, while it enables their conjugation to a wide variety of cargoes for their use as delivery agents. In this review, we summarize several aptamers that have been tested against MM specific targets with promising results, establishing the rationale for the further development of aptamer-based strategies against MM. In this direction, we believe that the study of novel plasma cell surface markers, the development of intracellular aptamers and further research on aptamers as building blocks for complex nanomedicines will lead to the generation of next-generation targeted approaches that will undoubtedly contribute to improve the management and life quality of MM patients.

Programmed Aptamer Screening, Characterization, and Rapid Detection for α-Conotoxin MI

Conotoxins (CTXs) are a variety of mixed polypeptide toxins, among which α-conotoxin MI (CTX-MI) is the most toxic. Serious toxic symptoms, a lack of counteracting drugs, and cumbersome detection processes have made CTX-MI a hidden danger for humans. One of the obstacles to resolving this problem is the absence of specific recognition elements. Aptamers have shown great advantages in the fields of molecule detection, drug development, etc. In this study, we screened and characterized aptamers for CTX-MI through a programmed process. MBMI-01c, the isolated aptamer, showed great affinity, with an affinity constant (K_D) of 0.524 μM, and it formed an antiparallel G-quadruplet (GQ) structure for the specific recognition of CTX-MI. Additionally, an aptasensor based on the biolayer interferometry (BLI) platform was developed and displayed high precision, specificity, and repeatability with a limit of detection (LOD) of 0.26 μM. This aptasensor provides a potential tool for the rapid detection of CTX-MI in 10 min. The aptamer can be further developed for the enrichment, detoxification, and biological studies of CTX-MI. Additionally, the programmed process is applicable to screening and characterizing aptamers for other CTXs.

Nonbiodegradable Spiegelmer-Driven Colorimetric Biosensor for Bisphenol A Detection

Spiegelmers are enantiomers of natural D-oligonucleotides that bind to targets with distinct structures such as aptamers. The high susceptibility of natural D-form aptamers to nucleases greatly hinders their application in biological environments. Here, a nonbiodegradable spiegelmer-based platform for the sensitive detection of bisphenol A (BPA) was developed. Due to the symmetric molecule of BPA, the D-form aptamer can be directly converted into mirror forms via chemical synthesis. Aptamer-target interactions that involve chemically synthesized spiegelmers were characterized by biolayer interferometry, and their stabilities were tested in various biological fluids by exposure to nucleases. We demonstrate for the first time the use of a nuclease-resistant spiegelmer in a simple, label-free gold nanoparticle-based colorimetric assay to detect BPA in a highly sensitive and selective manner. The aptasensor exhibits an LOD of 0.057 ng/mL and dynamic range of 10⁵ (100 pg/mL to 10 mg/mL). With sensing capacity and biological stability, the developed aptasensor shows great potential to utilize in in-field applications such as water quality monitoring.

Aptamers as Theragnostic Tools in Prostate Cancer

Despite of the capacity that several drugs have for specific inhibition of the androgen receptor (AR), in most cases, PCa progresses to an androgen-independent stage. In this context, the development of new targeted therapies for prostate cancer (PCa) has remained as a challenge. To overcome this issue, new tools, based on nucleic acids technology, have been developed. Aptamers are small oligonucleotides with a three-dimensional structure capable of interacting with practically any desired target, even large targets such as mammalian cells or viruses. Recently, aptamers have been studied for treatment and detection of many diseases including cancer. In PCa, numerous works have reported their use in the development of new approaches in diagnostics and treatment strategies. Aptamers have been joined with drugs or other specific molecules such as silencing RNAs (aptamer–siRNA chimeras) to specifically reduce the expression of oncogenes in PCa cells. Even though these studies have shown good results in the early stages, more research is still needed to demonstrate the clinical value of aptamers in PCa. The aim of this review was to compile the existing scientific literature regarding the use of aptamers in PCa in both diagnosis and treatment studies. Since Prostate-Specific Membrane Antigen (PSMA) aptamers are the most studied type of aptamers in this field, special emphasis was given to these aptamers.

Endothelial‐immune crosstalk contributes to vasculopathy in nonalcoholic fatty liver disease

The top cause of mortality in patients with nonalcoholic fatty liver disease (NAFLD) is cardiovascular complications. However, mechanisms of NAFLD‐associated vasculopathy remain understudied. Here, we show that blood outgrowth endothelial cells (BOECs) from NAFLD subjects exhibit global transcriptional upregulation of chemokines and human leukocyte antigens. In mouse models of diet‐induced NAFLD, we confirm heightened endothelial expressions of CXCL12 in the aortas and the liver vasculatures, and increased retention of infiltrated leukocytes within the vessel walls. To elucidate endothelial‐immune crosstalk, we performed immunoprofiling by single‐cell analysis, uncovering T cell intensification in NAFLD patients. Functionally, treatment with a CXCL12‐neutralizing antibody is effective at moderating the enhanced chemotactic effect of NAFLD BOECs in recruiting CD8⁺ T lymphocytes. Interference with the CXCL12‐CXCR4 axis using a CXCR4 antagonist also averts the impact of immune cell transendothelial migration and restores endothelial barrier integrity. Clinically, we detect threefold more circulating damaged endothelial cells in NAFLD patients than in healthy controls. Our work provides insight into the modulation of interactions with effector immune cells to mitigate endothelial injury in NAFLD.

DNA aptamer S11e recognizes fibrosarcoma and acts as a tumor suppressor

Fibrosarcoma is a serious malignant mesenchymal tumor with strong invasiveness, high recurrence, and poor prognosis. Currently, surgical resection is the main treatment for fibrosarcoma. However, due to the lack of specific biomarkers, the inability to accurately diagnose fibrosarcoma can lead to sub-optimal surgical outcomes and decreased survival. Here, we seek to address this translational barrier and we show that DNA aptamer S11e was able to recognize fibrosarcoma cells (HT1080) but not human embryonic lung fibroblast cells with Kd values in the nanomolar range. In addition, we found that S11e discerned tumors in HT1080 xenograft mouse models and tumor tissues from fibrosarcoma patients. Furthermore, we demonstrated that S11e internalized into HT1080 cells independent of the lysosome pathway and located in mitochondria. Moreover, we revealed that S11e promoted the apoptosis of HT1080 cells and inhibited HT1080 cell migration. Finally, we investigated the biologically functional cellular target of S11e using a mass spectrometry approach, and identified that Diablo/SMAC protein is a cellular binding protein of S11e, by interacting to which S11e inhibited HT1080 cell migration and invasion. Taken together, these results provide the evidence that S11e may be useful for early diagnosis, targeted therapy, and prognostication of fibrosarcoma.

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S11e specifically targets fibroscarcoma cells and could be a novel tool for the early diagnosis and therapy of fibrosarcoma.

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S11e can be internalized into HT1080 fibrosarcoma cells and located in mitochondria, which induces the apoptosis of the cells.

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S11e inhibits fibrosarcoma cell proliferation and migration via binding to Diablo/SMAC protein in mitochondria.

Cell-specific aptamers as potential drugs in therapeutic applications: A review of current progress

Cell-specific aptamers are a promising emerging player in the field of disease therapy. This paper reviews the multidimensional research progress made in terms of their classification, modification, and application. Based on the target location of cell-specific aptamers, it is defined and classified cell-specific aptamers into three groups including aptamers for cell surface markers, aptamers for intracellular components, and aptamers for extracellular components. Moreover, the modification methods of aptamers to achieve improved stability and affinity are concluded. In addition, recent advances in the application of cell-specific aptamers are discussed, mainly focusing on the increasing research attraction of cell state improving helpers and cell recruitment mediators in the improvement of cellular microenvironments to achieve successful disease therapy. This review also highlights 11 types of clinical aptamer drugs. Finally, the challenges and future directions of potential clinical applications are presented. In summary, we believe that cell-specific aptamers are promising drugs in disease therapy.

Colorectal Cancer: The Contribution of CXCL12 and Its Receptors CXCR4 and CXCR7

Colorectal cancer is one of the most common cancers, and diagnosis at late metastatic stages is the main cause of death related to this cancer. This progression to metastasis is complex and involves different molecules such as the chemokine CXCL12 and its two receptors CXCR4 and CXCR7. The high expression of receptors in CRC is often associated with a poor prognosis and aggressiveness of the tumor. The interaction of CXCL12 and its receptors activates signaling pathways that induce chemotaxis, proliferation, migration, and cell invasion. To this end, receptor inhibitors were developed, and their use in preclinical and clinical studies is ongoing. This review provides an overview of studies involving CXCR4 and CXCR7 in CRC with an update on their targeting in anti-cancer therapies.

Selection, Characterization, and Optimization of DNA Aptamers against Challenging Marine Biotoxin Gymnodimine-A for Biosensing Application

Gymnodimines (GYMs), belonging to cyclic imines (CIs), are characterized as fast-acting toxins, and may pose potential risks to human health and the aquaculture industry through the contamination of sea food. The existing detection methods of GYMs have certain defects in practice, such as ethical problems or the requirement of complicated equipment. As novel molecular recognition elements, aptamers have been applied in many areas, including the detection of marine biotoxins. However, GYMs are liposoluble molecules with low molecular weight and limited numbers of chemical groups, which are considered as "challenging" targets for aptamers selection. In this study, Capture-SELEX was used as the main strategy in screening aptamers targeting gymnodimine-A (GYM-A), and an aptamer named G48nop, with the highest KD value of 95.30 nM, was successfully obtained by screening and optimization. G48nop showed high specificity towards GYM-A. Based on this, a novel aptasensor based on biolayer interferometry (BLI) technology was established in detecting GYM-A. This aptasensor showed a detection range from 55 to 1400 nM (linear range from 55 to 875 nM) and a limit of detection (LOD) of 6.21 nM. Spiking experiments in real samples indicated the recovery rate of this aptasensor, ranging from 96.65% to 109.67%. This is the first study to report an aptamer with high affinity and specificity for the challenging marine biotoxin GYM-A, and the new established aptasensor may be used as a reliable and efficient tool for the detection and monitoring of GYMs in the future.

Aptamers: Potential Diagnostic and Therapeutic Agents for Blood Diseases

Aptamers are RNA/DNA oligonucleotide molecules that specifically bind to a targeted complementary molecule. As potential recognition elements with promising diagnostic and therapeutic applications, aptamers, such as monoclonal antibodies, could provide many treatment and diagnostic options for blood diseases. Aptamers present several superior features over antibodies, including a simple in vitro selection and production, ease of modification and conjugation, high stability, and low immunogenicity. Emerging as promising alternatives to antibodies, aptamers could overcome the present limitations of monoclonal antibody therapy to provide novel diagnostic, therapeutic, and preventive treatments for blood diseases. Researchers in several biomedical areas, such as biomarker detection, diagnosis, imaging, and targeted therapy, have widely investigated aptamers, and several aptamers have been developed over the past two decades. One of these is the pegaptanib sodium injection, an aptamer-based therapeutic that functions as an anti-angiogenic medicine, and it is the first aptamer approved by the U.S. Food and Drug Administration (FDA) for therapeutic use. Several other aptamers are now in clinical trials. In this review, we highlight the current state of aptamers in the clinical trial program and introduce some promising aptamers currently in pre-clinical development for blood diseases.

Elevated CXCL12 in the plasma membrane of locally advanced rectal cancer after neoadjuvant chemoradiotherapy: a potential prognostic marker

Background: Neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer (LARC) has been shown to improve sphincter preservation and local pelvic control, but the efficacy of nCRT plateaus due to metastasis. CXC chemokine ligand 12 (CXCL12) has a critical impact on cancer development and metastasis.

Methods: By investigating public databases containing LARC patient data, CXCL12, CXCR4 and FAPα expression was analyzed via the Tumor Immune Estimation Resource (TIMER) and GSEA. Immunohistochemistry was applied to a total of 121 surgically resected specimens consisting of 61 LARCs after nCRT and 60 LARCs with no nCRT and 16 cases with endoscopic resection of high-grade colorectal adenoma.

Results: By investigating public databases containing LARC patient data, CXCL12 expression is correlated with poor prognosis, immune cell infiltration, epithelial- mesenchymal transition, and angiogenesis in LARC. Furthermore, radiation selectively induced CXCL12, CXCR4 and FAPα expression in tumor tissues. Immunohistochemistry results showed that the levels of CXCL12, CXCR4, and FAPα in LARC cells after nCRT were higher than in LARC cells untreated with nCRT (p < 0.001 for each). Elevated levels of CXCL12 in the plasma membrane of LARC cells after nCRT demonstrated an association with the period of freedom from recurrence (FFR) in univariate and multivariate survival analyses (p = 0.005 and p = 0.031, respectively).

Conclusions: The expression of CXCL12 may influence the survival and invasive properties of LARC cells during nCRT and promote cancer recurrence. We suggest that CXCL12 expression in the plasma membrane of radioresistant LARC cells may be a predictive factor of recurrence and a viable therapeutic strategy to control radioresistant LARC recurrence.

CXCL12 in Pancreatic Cancer: Its Function and Potential as a Therapeutic Drug Target

Simple Summary

Pancreatic cancer is a challenging disease to treat effectively. Fibroblasts associated with pancreatic cancer contribute to disease progression by secreting factors that enhance tumor cell survival and help tumor cells avoid detection by the immune system. This overview focuses on a chemokine, CXCL12, produced by cancer-associated fibroblasts and how CXCL12 signaling enhances pancreatic cancer progression by contributing to various hallmarks of cancer including, but not limited to, tumor growth and evasion of immune response. These pro-oncogenic functions of CXCL12 make it an attractive target in pancreatic cancer. We discuss the different approaches in development to therapeutically target CXCL12 and finally propose a novel approach, the use of the farnesyl transferase inhibitor tipifarnib to inhibit CXCL12 expression in pancreatic fibroblasts.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a disease with limited therapeutic options and dismal long-term survival. The unique tumor environment of PDAC, consisting of desmoplastic stroma, immune suppressive cells, and activated fibroblasts, contributes to its resistance to therapy. Activated fibroblasts (cancer-associated fibroblasts and pancreatic stellate cells) secrete chemokines and growth factors that support PDAC growth, spread, chemoresistance, and immune evasion. In this review, we focus on one such chemokine, CXCL12, secreted by the cancer-associated fibroblasts and discuss its contribution to several of the classical hallmarks of PDAC and other tumors. We review the various therapeutic approaches in development to target CXCL12 signaling in PDAC. Finally, we propose an unconventional use of tipifarnib, a farnesyl transferase inhibitor, to inhibit CXCL12 production in PDAC.

Aptamer Applications in Neuroscience

Being the predominant cause of disability, neurological diseases have received much attention from the global health community. Over a billion people suffer from one of the following neurological disorders: dementia, epilepsy, stroke, migraine, meningitis, Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, Huntington's disease, prion disease, or brain tumors. The diagnosis and treatment options are limited for many of these diseases. Aptamers, being small and non-immunogenic nucleic acid molecules that are easy to chemically modify, offer potential diagnostic and theragnostic applications to meet these needs. This review covers pioneering studies in applying aptamers, which shows promise for future diagnostics and treatments of neurological disorders that pose increasingly dire worldwide health challenges.

Trisubstituted 1,3,5-Triazines: The First Ligands of the sY12-Binding Pocket on Chemokine CXCL12

CXCL12, a CXC-type chemokine, binds its receptor CXCR4, and the resulting signaling cascade is essential during development and subsequently in immune function. Pathologically, the CXCL12–CXCR4 signaling axis is involved in many cancers and inflammatory diseases and thus has sparked continued interest in the development of therapeutics. Small molecules targeting CXCR4 have had mixed results in clinical trials. Alternatively, small molecules targeting the chemokine instead of the receptor provide a largely unexplored space for therapeutic development. Here we report that trisubstituted 1,3,5-triazines are competent ligands for the sY12-binding pocket of CXCL12. The initial hit was optimized to be more synthetically tractable. Fifty unique triazines were synthesized, and the structure–activity relationship was probed. Using computational modeling, we suggest key structural interactions that are responsible for ligand–chemokine binding. The lipophilic ligand efficiency was improved, resulting in more soluble, drug-like molecules with chemical handles for future development and structural studies.

Oligonucleotide aptamers: Recent advances in their screening, molecular conformation and therapeutic applications

Aptamers are single stranded oligonucleotides with specific recognition and binding ability to target molecules, which can be obtained by Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Aptamers have the advantages of low molecular weight, low immunogenicity, easy modification and high stability. They play promising role in promoting food safety, monitoring the environment and basic research, especially in clinical diagnosis and therapeutic drugs. To date, great achievements regarding the selection, modifications and application of aptamers have been made. However, since it is still a challenge to obtain aptamers with high affinity in a more effective way, few aptamer-based products have already successfully entered into clinical use. This review aims to provide a thorough overview of the latest advances in this rapidly developing field, focusing on aptamer screening methods for different targets, the structure of the interaction between aptamers and target substances, and the challenges and potential of current therapeutic aptamers.

Combined inhibition of CXCL12 and PD-1 in MSS colorectal and pancreatic cancer: modulation of the microenvironment and clinical effects

BACKGROUND

Immunotherapy in microsatellite stable colorectal or pancreatic cancer has not shown promising results. It has been hypothesized that targeting immunosuppressive molecules like SDF1-alpha/CXCL12 could contribute to immunotherapy and animal models showed promising results on T cell activation and migration in combination with immune checkpoint inhibition.

METHODS

Here, we describe the successful application of anti-CXCL12 (NOX-A12) in patients with advanced stage pretreated metastatic colorectal and pancreatic cancer (OPERA trial). The treatment consisted of 2 weeks of anti-CXCL12 monotherapy with NOX-A12 followed by combination therapy with pembrolizumab (n=20 patients) until progression or intolerable toxicity had occurred.

RESULTS

The treatment was safe and well tolerated with 83.8% grade I/II, 15.5% grade III and 0.7% grade V adverse events. Of note, for a majority of patients, time on trial treatment was prolonged compared with their last standard treatment preceding trial participation. Systematic serial biopsies revealed distinct patterns of modulation. Tissue and clinical responses were associated with Th1-like tissue reactivity upon CXCL12 inhibition. A downregulation of a cytokine cassette of interleukin (IL)-2/IL-16/CXCL-10 was associated with tumor resistance and furthermore linked to a rare, CXCL12-associated CD14+CD15+promonocytic population. T cells showed aggregation and directed movement towards the tumor cells in responding tissues. Serum analyses detected homogeneous immunomodulatory patterns in all patients, regardless of tissue responses.

CONCLUSIONS

We demonstrate that the combination of CXCL12 inhibition and checkpoint inhibition is safe and grants further exploration of synergistic combinatorial strategies.

Identification and Engineering of Aptamers for Theranostic Application in Human Health and Disorders

An aptamer is a short sequence of synthetic oligonucleotides which bind to their cognate target, specifically while maintaining similar or higher sensitivity compared to an antibody. The in-vitro selection of an aptamer, applying a conjoining approach of chemistry and molecular biology, is referred as Systematic Evolution of Ligands by Exponential enrichment (SELEX). These initial products of SELEX are further modified chemically in an attempt to make them stable in biofluid, avoiding nuclease digestion and renal clearance. While the modification is incorporated, enough care should be taken to maintain its sensitivity and specificity. These modifications and several improvisations have widened the window frame of aptamer applications that are currently not only restricted to in-vitro systems, but have also been used in molecular imaging for disease pathology and treatment. In the food industry, it has been used as sensor for detection of different diseases and fungal infections. In this review, we have discussed a brief history of its journey, along with applications where its role as a therapeutic plus diagnostic (theranostic) tool has been demonstrated. We have also highlighted the potential aptamer-mediated strategies for molecular targeting of COVID-19. Finally, the review focused on its future prospective in immunotherapy, as well as in identification of novel biomarkers in stem cells and also in single cell proteomics (scProteomics) to study intra or inter-tumor heterogeneity at the protein level. Small size, chemical synthesis, low batch variation, cost effectiveness, long shelf life and low immunogenicity provide advantages to the aptamer over the antibody. These physical and chemical properties of aptamers render them as a strong biomedical tool for theranostic purposes over the existing ones. The significance of aptamers in human health was the key finding of this review.

The Role of Post-Translational Modifications of Chemokines by CD26 in Cancer

Chemokines are a large family of small chemotactic cytokines that fulfill a central function in cancer. Both tumor-promoting and -impeding roles have been ascribed to chemokines, which they exert in a direct or indirect manner. An important post-translational modification that regulates chemokine activity is the NH₂-terminal truncation by peptidases. CD26 is a dipeptidyl peptidase (DPPIV), which typically clips a NH₂-terminal dipeptide from the chemokine. With a certain degree of selectivity in terms of chemokine substrate, CD26 only recognizes chemokines with a penultimate proline or alanine. Chemokines can be protected against CD26 recognition by specific amino acid residues within the chemokine structure, by oligomerization or by binding to cellular glycosaminoglycans (GAGs). Upon truncation, the binding affinity for receptors and GAGs is altered, which influences chemokine function. The consequences of CD26-mediated clipping vary, as unchanged, enhanced, and reduced activities are reported. In tumors, CD26 most likely has the most profound effect on CXCL12 and the interferon (IFN)-inducible CXCR3 ligands, which are converted into receptor antagonists upon truncation. Depending on the tumor type, expression of CD26 is upregulated or downregulated and often results in the preferential generation of the chemokine isoform most favorable for tumor progression. Considering the tight relationship between chemokine sequence and chemokine binding specificity, molecules with the appropriate characteristics can be chemically engineered to provide innovative therapeutic strategies in a cancer setting.

Aptamers: Cutting edge of cancer therapies

The development of an aptamer-based therapeutic has rapidly progressed following the first two reports in the 1990s, underscoring the advantages of aptamer drugs associated with their unique binding properties. In 2004, the US Food and Drug Administration (FDA) approved the first therapeutic aptamer for the treatment of neovascular age-related macular degeneration, Macugen developed by NeXstar. Since then, eleven aptamers have successfully entered clinical trials for various therapeutic indications. Despite some of the pre-clinical and clinical successes of aptamers as therapeutics, no aptamer has been approved by the FDA for the treatment of cancer. This review highlights the most recent and cutting-edge approaches in the development of aptamers for the treatment of cancer types most refractory to conventional therapies. Herein, we will review (1) the development of aptamers to enhance anti-cancer immunity and as delivery tools for inducing the expression of immunogenic neoantigens; (2) the development of the most promising therapeutic aptamers designed to target the hard-to-treat cancers such as brain tumors; and (3) the development of "carrier" aptamers able to target and penetrate tumors and metastasis, delivering RNA therapeutics to the cytosol and nucleus.