EpCAM Aptamer-siRNA Chimera Targets and Regress Epithelial Cancer

Targeting pediatric solid tumors in the new era of RNA therapeutics

Despite substantial progress in pediatric cancer treatment, poor prognosis remained for patients with recurrent or metastatic disease, given the limitations of approved targeted treatments and immunotherapies. RNA therapeutics offer significant potential for addressing a broad spectrum of diseases, including cancer. Advances in manufacturing and delivery systems are paving the way for the rapid development of therapeutic RNAs for clinical applications. This review summarizes therapeutic RNA classifications and the mechanisms of action, highlighting their potential in manipulating major cancer-related pathways and biological effects. We also focus on the pre-clinical investigation of RNA molecules with efficient delivery systems for their therapeutic potential targeting pediatric solid tumors.

Targeted delivery of elesclomol using a magnetic mesoporous platform improves prostate cancer treatment both in vitro and in vivo

BACKGROUND

To improve the anticancer properties of elesclomol (ELC), targeted theranostic nanoparticles (NPs; APT-PEG-Au-MMNPs@ELC) were designed to increase the selectivity of the drug delivery system (DDS).

MATERIALS AND METHODS

ELC was synthesized and entrapped in the open porous structure of magnetic mesoporous silica nanoparticles (MMNPs). The pore entrance of MMNPs was then blocked using gold gatekeepers. Finally, the external surfaces of the particles were grafted with functional polyethylene glycol (PEG) and EpCAM aptamer to generate biocompatible and targeted NPs. In the next step, the physicochemical properties of prepared NPs were fully evaluated and their anticancer potential was evaluated both in vitro and in vivo.

RESULTS

The targeted NPs were successfully synthesized with a final size diameter of 81.13 ± 7.41 nm. The results indicated a pH-dependent release pattern, which sustained for 72 h despite an initial rapid release. Upon exposure to APT-PEG-Au-MMNPs@ELC, higher cytotoxicity was observed in human prostate cancer cells (PC-3) as compared with control Chinese hamster ovary (CHO) cells, indicating higher specificity of targeted NPs against EpCAM-positive cancerous cells. Moreover, APT-PEG-Au-MMNPs@ELC could induce apoptosis in PC-3 cells. In vivo results on a PC-3 xenograft tumor model demonstrated that targeted NPs could significantly inhibit tumor growth and diminish severe side effects of ELC, compared to the free drug.

CONCLUSION

Collectively, APT-PEG-Au-MMNPs@ELC could be considered a promising theranostic platform for the targeted delivery of ELC to improve its therapeutic effects in prostate cancer.

Identification of alanine aminotransferase 1 interaction network via iTRAQ-based proteomics in alternating migration, invasion, proliferation and apoptosis of HepG2 cells

OBJECTIVE

To investigate the mechanism of alanine aminotransferase 1 (ALT1) in the progression of HCC, the differentially expressed proteins (DEPs) in the ALT1 interaction network were identified by targeted proteomic analysis.

METHODS

Wound healing and transwell assays were conducted to assess the effect of ALT1 on cellular migration and invasion. Cell Counting Kit-8 (CCK-8), colony formation, and flow cytometry assays were performed to identify alterations in proliferation and apoptosis. After coimmunoprecipitation processing, mass spectrometry with iso-baric tags for relative and absolute quantitation was utilized to explore the protein interactions in ALT1 knockdown HepG2 cells.

RESULTS

The results showed that ALT1 knockdown inhibits the migration, invasion, proliferation of HepG2 cells, and promotes apoptosis. A total of 116 DEPs were identified and the bioinformatics analysis suggested that the ALT1-interacting proteins were primarily associated with cellular and metabolic processes. Knockdown of ALT1 in HepG2 cells reduced the expression of Ki67 and epithelial cell adhesion molecule (EP-CAM), while the expression of apoptosis-stimulating protein 2 of p53 (ASPP2) was increased significantly. Suppression of the ALT1 and EP-CAM expression contributed to alterations in epithelial-mesenchymal transition (EMT) -associated markers and matrix metalloproteinases (MMPs). Additionally, inhibition of ALT1 and Ki67 also decreased the expression of apoptosis and proliferation factors. Furthermore, inhibition of ALT1 and ASPP2 also changed the expression of P53, which may be the signaling pathway by which ALT regulates these biological behaviors.

CONCLUSIONS

This study indicated that the ALT1 protein interaction network is associated with the biological behaviors of HepG2 cells via the p53 signaling pathway.

Advances of Epigenetic Biomarkers and Epigenome Editing for Early Diagnosis in Breast Cancer

Epigenetic modifications are known to regulate cell phenotype during cancer progression, including breast cancer. Unlike genetic alterations, changes in the epigenome are reversible, thus potentially reversed by epi-drugs. Breast cancer, the most common cause of cancer death worldwide in women, encompasses multiple histopathological and molecular subtypes. Several lines of evidence demonstrated distortion of the epigenetic landscape in breast cancer. Interestingly, mammary cells isolated from breast cancer patients and cultured ex vivo maintained the tumorigenic phenotype and exhibited aberrant epigenetic modifications. Recent studies indicated that the therapeutic efficiency for breast cancer regimens has increased over time, resulting in reduced mortality. Future medical treatment for breast cancer patients, however, will likely depend upon a better understanding of epigenetic modifications. The present review aims to outline different epigenetic mechanisms including DNA methylation, histone modifications, and ncRNAs with their impact on breast cancer, as well as to discuss studies highlighting the central role of epigenetic mechanisms in breast cancer pathogenesis. We propose new research areas that may facilitate locus-specific epigenome editing as breast cancer therapeutics.

Selection of DNA Aptamers Recognizing EpCAM-Positive Prostate Cancer by Cell-SELEX for in vitro and in vivo MR Imaging

Background

The sensitive and specific detection of pathogenic cells is important in tumor diagnosis at an early stage. Aptamers are short single-stranded oligonucleotides evolved from systematic evolution of ligands by exponential enrichment (SELEX). It has been proved that aptamers can interact with cognate target molecules with high affinity and specificity and have great potential in the development of medical imaging at molecular level.

Purpose

To select epithelial cell adhesion molecule (EpCAM) specific aptamers targeting prostate cancer and further to conjugate aptamers with GoldMag nanoparticles (a typical iron oxide core/gold shell structure) to construct magnetic molecular probes for medical imaging.

Methods

EpCAM-specific aptamers were selected by Cell-SELEX. The enrichment of specific aptamer candidates was monitored by flow cytometric analysis. Aptamers were further conjugated with GoldMag nanoparticles to construct magnetic molecular probes. The affinity and specificity of aptamer candidates and aptamer-conjugated GoldMag nanoparticles were evaluated. The MR imaging of aptamer-conjugated GoldMag nanoparticles to prostate cancer was further explored in vitro and in vivo.

Results

After 12 rounds of selection, aptamer candidates Eppc6 and Eppc14 could specifically target three types of prostate cancer cells, revealing a high affinity of Eppc6 and Eppc14. Moreover, aptamer-conjugated GoldMag nanoparticles not only exhibited good affinity to different prostate cancer cells but also produced strong T2WI signal intensity reduction distinguished from peritumoral tissue in MRI, indicating that the molecular probes possess both the affinity properties of EpCAM-specific aptamer and the superparamagnetic features of iron oxide.

Conclusion

Our study indicates that aptamer Eppc6 and Eppc14 can recognize prostate cancer cells and tissues. The aptamer-conjugated GoldMag nanoparticles constructed in the study can be used as a molecular imaging agent for detection of PCa in MRI.

Breast Cancer Aptamers: Current Sensing Targets, Available Aptamers, and Their Evaluation for Clinical Use in Diagnostics

Breast cancer is the most commonly occurring cancer in women worldwide, and the rate of diagnosis continues to increase. Early detection and targeted treatment towards histological type is crucial to improving outcomes, but current screening methods leave some patients at risk of late diagnosis. The risk of late diagnosis and progressed disease is of particular concern for young women as current screening methods are not recommended early in life. Aptamers are oligonucleotides that can bind with high specificity to target molecules such as proteins, peptides, and other small molecules. They are relatively cheap to produce and are invariable from batch to batch, making them ideal for use in large-scale clinical or screening programs. The use of aptamers for breast cancer screening, diagnosis, and therapeutics is promising, but comparison of these aptamers and their corresponding biomarkers for use in breast cancer is significantly lacking. Here, we compare the currently available aptamers for breast cancer biomarkers and their respective biomarkers, as well as highlight the electrochemical sensors that are in development.

Circulating tumor-cell-targeting Au-nanocage-mediated bimodal phototherapeutic properties enriched by magnetic nanocores

Metastasis resulting from circulating tumor cells (CTCs) is associated with 90% of all cancer mortality. To disrupt cancer dissemination, therapeutic targeting of CTCs by extracorporeal photodynamic therapy (PDT) has emerged; however, it still remains impractical due to its limited therapeutic window. Herein, we developed a photosensitive and magnetic targeted core-satellite nanomedicine (TCSN) to augment the light-induced damage to the targeted cells. The magnetic nanocore (MNC) with multiple iron oxide nanoparticles stabilized using thiolated polyvinyl alcohol can magnetize the CTCs to achieve magnetic enrichment under a magnetic field. Multiple gold nanocage (AuNC) satellites were conjugated on the MNC to facilitate bimodal photothermal therapy and PDT. Adjusting the thiol content in the MNC allows manipulating the AuNC density on TCSNs, which has been found to demonstrate a density-dependent bimodal phototherapeutic effect under laser irradiation at 808 and 940 nm. Moreover, with the immobilization of anti-epithelial cell adhesion molecule (anti-EpCAM), TCSN exhibited an enhanced affinity toward EpCAM-expressing 4T1 cells. We demonstrate that TCSN-labeled 4T1 cells can be isolated and photo-eradicated in a microfluidic channel with a dynamic flow. Our studies showed that TCSN with the complementary properties of MNC and AuNCs can largely augment the therapeutic window by magnetic enrichment and bimodal phototherapy, serving as an advanced extracorporeal strategy to remove CTCs.

Stick-Based Methods for Aptamer-Mediated siRNA Targeted Delivery

Despite the therapeutic utility of small interfering RNA (siRNA) molecules, the development of a safe and reliable method to selectively target diseased organs and tissues is still a critical need for their translation to the clinic. Here we describe how nucleic acid-based aptamers against cell surface epitopes may be used to address this issue. We discuss the most recent examples and advances in the field of aptamer siRNA delivery and provide a fast and simple protocol for the design and generation of aptamer-siRNA chimeras. The described approach is based on the annealing of the targeting aptamer, and the antisense strand through "stick" complementary sequences elongated at their 3' end, and the subsequent paring with the sense strand. Such a protocol allows a modular non-covalent generation of the constructs and permits an efficient delivery of the siRNA moiety into aptamer target cells.

Internal Oligoguanidinium Transporter: Mercury-Free Scalable Synthesis, Improvement of Cellular Localization, Endosomal Escape, Mitochondrial Localization, and Conjugation with Antisense Morpholino for NANOG Inhibition to Induce Chemosensitization of Taxol in MCF-7 Cells

A nontoxic delivery vehicle is essential for the therapeutic applications of antisense phosphorodiamidate morpholino oligonucleotides (PMOs). Though guanidinium-rich or arginine-rich cellular transporter conjugated Vivo-PMO or PPMO has been developed for in vivo application, however, either their toxicity or stability has become an issue. Previously, we reported nonpeptidic internal guanidinium transporter (IGT) mediated delivery of PMO for gene silencing and got encouraging results. In this paper, we report the synthesis of IGT using a Hg-free method for scale up and N-terminal modification of IGT with a suitable hydrophobic or lipophilic group to improve the cell permeability, endosomal escape, and mitochondrial localization and to reduce toxicity in the MTT assay. For the delivery of PMO, IGT-PMO conjugate was synthesized to target NANOG in cells, a transcription factor required for cancer stem cell proliferation and embryonic development and is involved in many cancers. Our data shows IGT-PMO-facilitated NANOG inhibition, and thereby the prevention of EpCAM-N-Cadherin-Vimentin axis mediated epithelial to mesenchymal transition (EMT) in MCF-7 cells. Moreover, unlike taxol, NANOG inhibition influences the expression of stemness factor c-Myc, Hh-Gli signaling proteins, other cancer related factors, and their respective phenotypes in cancer cells. To the best of our knowledge, this is the first report to illustrate that the IGT-PMO-mediated NANOG inhibition increases the therapeutic potential of taxol and induces G0-G1 arrest in cancer cells to prevent cancer progression. However, it warrants further investigation in other cancer cells and preclinical platforms.

Synthesis of combinatorial Janus nanoparticles based on EpCAM-PEG/PCL for targeted therapy of human colorectal adenocarcinoma

Active targeted nanotechnology-based drug delivery systems have gained significant favor because they have the ability to decrease side effects, improve drug bioavailability, and the potency of anticancer treatment. In this study, functional amphiphilic Janus nanoparticles (JNPs), consisting of hydrophilic and hydrophobic biocompatible polymers as two distinct sides, have been prepared via a robust and simple synthesis method. The surface-active hydrophilic side of this Janus platform is functionalized with an aptamer against epithelial cell adhesion molecule (EpCAM) to deliver Doxorubicin (DOX) for the treatment of metastasis colorectal adenocarcinoma HT29 cells. The Janus morphology of the nanoparticles and their cell penetration behavior are shown in microscopic evaluations. By evaluating the prepared DOX-loaded aptamer-modified JNPs by cell-toxicity assay and confocal microscopy, it was determined that the utilization of an internalization strategy to enhance cell uptake would increase the anticancer effect of the Janus nanocarrier and improve the capacity to deliver the chemotherapeutical drug site-specifically.

Targeting Cancer with Peptide RNAi Nanoplexes

With the recent explosion of genomic information on the root causes of disease, there is an increased interest in nucleic acid therapeutics, including siRNA and gene therapy, all of which require delivery of highly charged nucleic acids from siRNA with a molecular weight of about 1.4 × 10⁴ to plasmids with an approximate molecular weight of 2.0-3.0 × 10⁶. This chapter describes the delivery of shRNA via plasmid or siRNA with a peptide-based carrier. We focus on the histidine-lysine peptide which serves as an example for other peptides and polymeric carrier systems. When the HK peptide and nucleic acids are mixed together and interact with one another through ionic and nonionic interactions, nanoplexes are formed. These nanoplexes, carrying either shRNA or siRNA that target oncogenes, provide promising options for the treatment of cancer. We describe methods of preparation and characterization of these nanoplexes using dynamic light scattering, zeta potential, and gel retardation assays. We also provide protocols for transfection in vitro and in vivo for these nanoplexes.

Nucleic acids delivering nucleic acids

Nucleic acid therapeutics, including siRNAs, miRNAs/antimiRs, gRNAs and ASO, represent innovative and highly promising molecules for the safe treatment of a wide range of pathologies. The efficiency of systemic treatments is impeded by 1) the need to overcome physical and functional barriers in the organism, and 2) to accumulate in the intracellular active site at therapeutic concentrations. Although oligonucleotides either as modified naked molecules or complexed with delivery carriers have revealed to be effectively delivered to the affected target cells, this is restricted to topic treatments or to a few highly vascularized tissues. Therefore, the development of effective strategies for therapeutic nucleic acid selective delivery to target tissues is of primary importance in order to reduce the occurrence of undesired effects on non-target healthy tissues and to permit their translation to clinic. Due to their high affinity for specific ligands, high tissue penetration and chemical flexibility, short single-stranded nucleic acid aptamers are emerging as very attractive carriers for various therapeutic oligonucleotides. Yet, different aptamer-based bioconjugates, able to provide accumulation into target tissues, as well as efficient processing of therapeutic oligonucleotides, have been developed. In this respect, nucleic acid aptamer-mediated delivery strategies represent a powerful approach able to increase the therapeutic efficacy also highly reducing the overall toxicity. In this review, we will summarize recent progress in the field and discuss achieved objectives and optimization of aptamers as delivery carriers of short oligonucleotides.

Targeted siRNA delivery using aptamer-siRNA chimeras and aptamer-conjugated nanoparticles

The sequence-specific gene-silencing ability of small interfering RNA (siRNA) has been exploited as a new therapeutic approach for the treatment of a variety of diseases. However, efficient and safe delivery of siRNA into target cells is still a challenge in the clinical development of siRNA-based therapeutics. Recently, nucleic acid-based aptamers that target cell surface proteins have emerged as a new class of targeting moieties due to their high specificity and avidity. To date, various aptamer-mediated siRNA delivery systems have been developed to enhance the RNA interference (RNAi) efficacy of siRNA via targeted delivery. In this review, we summarize recent advances in developing aptamer-mediated siRNA delivery systems for RNAi therapeutics, mainly aptamer-siRNA chimeras and aptamer-functionalized nanocarriers incorporating siRNA, with a focus on their molecular designs and formulations. In addition, the challenges and engineering strategies of aptamer-mediated siRNA delivery systems for clinical translation are discussed. This article is categorized under: Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Bispecific therapeutic aptamers for targeted therapy of cancer: a review on cellular perspective

Aptamers (Aps), as short single-strand nucleic acids, can bind to their corresponding molecular targets with the high affinity and specificity. In comparison with the monoclonal antibodies (mAbs) and peptides, unique physicochemical and biological characteristics of Aps make them excellent targeting agents for different types of cancer molecular markers (CMMs). Much attention has been paid to the Ap-based multifunctional chimeric and therapeutic systems, which provide promising outcomes in the targeted therapy of various formidable diseases, including malignancies. In the Ap-based chimeric systems, a targeting Ap is conjugated to another therapeutic molecule (e.g., siRNA/miRNA, Ap, toxins, chemotherapeutic agents, DNAzyme/ribozymes) with a capability of binding to a specific cell surface receptor at the desired target site. Having been engineered as multifunctional nanosystems (NSs), Ap-based hybrid scaffolds can be used to concurrently target multiple markers/pathways in cancerous cells, causing drastic inhibitory effects on the growth and the progression of tumor cells. Multi/bispecific Aps composed of two/more Aps provide a versatile tool for the optimal and active targeting of cell surface receptor(s) with markedly high affinity and avidity. Targeting the optimum activity of key receptors and dominant signaling pathways in the activation of immunity, the multi/bispecific Ap-based therapeutics can also be used to enhance the antitumor activity of the immune system. Further, the bispecific systems can be designed to induce cytotoxicity in a heterogeneous population of cancer cells with different CMMs. In this review, we provide some important insights into the construction and applications of the Ap-based chimeric NSs and discuss the multifunctional Ap chimera and their effects on the signaling pathways in cancer.

Current Advances in Aptamers for Cancer Diagnosis and Therapy

Nucleic acid aptamers are single-stranded oligonucleotides that interact with target molecules with high affinity and specificity in unique three-dimensional structures. Aptamers are generally isolated by a simple selection process called systematic evolution of ligands by exponential enrichment (SELEX) and then can be chemically synthesized and modified. Because of their high affinity and specificity, aptamers are promising agents for biomarker discovery, as well as cancer diagnosis and therapy. In this review, we present recent progress and challenges in aptamer and SELEX technology and highlight some representative applications of aptamers in cancer therapy.

Enzyme-free ultrasensitive fluorescence detection of epithelial cell adhesion molecules based on a toehold-aided DNA recycling amplification strategy

Epithelial cell adhesion molecules (EpCAMs) play a significant role in tumorigenesis and tumor development. EpCAMs are considered to be tumor signaling molecules for cancer diagnosis, prognosis and therapy. Herein, an enzyme-free and highly sensitive fluorescent biosensor, with a combined aptamer-based EpCAM recognition and toehold-aided DNA recycling amplification strategy, was developed for sensitive and specific fluorescence detection of EpCAMs. Due to highly specific binding between EpCAMs and corresponding aptamers, strand a, which is released from the complex of aptamer/strand a in the presence of EpCAMs which is bound to the corresponding aptamer, triggered the toehold-mediated strand displacement process. An amplified fluorescent signal was achieved by recycling strand a for ultrasensitive EpCAM detection with a detection limit as low as 0.1 ng mL⁻¹, which was comparable or superior to that of reported immunoassays and biosensor strategies. In addition, high selectivity towards EpCAMs was exhibited when other proteins were selected as control proteins. Finally, this strategy was successfully used for the ultrasensitive fluorescence detection of EpCAMs in human serum samples with satisfactory results. Importantly, the present strategy may be also expanded for the detection of other targets using the corresponding aptamers.

A fluorescent biosensor with a combined aptamer-based EpCAM recognition and toehold-aided DNA recycling amplification strategy was developed.

Targeted Delivery of siRNA Therapeutics to Malignant Tumors

Over the past 20 years, a diverse group of ligands targeting surface biomarkers or receptors has been identified with several investigated to target siRNA to tumors. Many approaches to developing tumor-homing peptides, RNA and DNA aptamers, and single-chain variable fragment antibodies by using phage display, in vitro evolution, and recombinant antibody methods could not have been imagined by researchers in the 1980s. Despite these many scientific advances, there is no reason to expect that the ligand field will not continue to evolve. From development of ligands based on novel or existing biomarkers to linking ligands to drugs and gene and antisense delivery systems, several fields have coalesced to facilitate ligand-directed siRNA therapeutics. In this review, we discuss the major categories of ligand-targeted siRNA therapeutics for tumors, as well as the different strategies to identify new ligands.

Challenging cancer targets for aptamer delivery

The extraordinary boost in the understanding of the genetic and epigenetic mechanisms underlying the development and progression of different types of cancer, is offering an unprecedented hope for the development of precise therapeutics able to interfere or replace the expression of target genes. In the last decade, the design of stable, safe and effective RNA-based therapeutics has been significantly improved increasing the number of molecules now in preclinical or in clinical trials for cancer gene therapy. However, with few exclusions as liver and hematological malignancies which are easy accessible to drugs, the development of effective systemic approaches for the delivery of RNA therapeutics to target cells is still unmet. To be effective, targeting carriers must be able to overcome both functional and physical barriers to safely carry and accumulate the therapeutic through the organism selectively to the tumor site, penetrate the target cancer mass, promote the uptake and localization in the appropriate intracellular compartment ultimately leading to the effective modulation of gene expression. Nucleic acid aptamers are folded single stranded oligonucleotides that bind at high affinity and high specificity their targets (proteins, lipids, small molecules etc), coupling the advantages of binding specificity proper of antibodies to the chemical nature of nucleic acids, sometimes also termed "nucleic acid antibodies". In several cases, aptamers targeting cell surface receptors are recycled into the cell together with the bound receptor enabling to drive conjugated therapeutics to cancer cells in a receptor-dependent manner. Therefore, besides other in vivo delivery strategies, the use of aptamers as precise and effective targeting moieties for anticancer RNA-based therapeutics has rapidly emerged and has been successfully addressed by several laboratories. In this Review, we will focus on the most recent and challenging progresses in the field that highlights the precision and flexibility of aptamer-based chimeras paving the way to the development of safe and effective carriers for cancer gene therapeutics.

Aptamer-Based Therapeutic Approaches to Target Cancer Stem Cells

Cancer stem cells (CSCs) are believed to be a principal cellular source for tumour progression and therapeutic drug resistance as they are capable of self-renewal and can differentiate into cancer cells. Importantly, CSCs acquire the ability to evade the killing effects of cytotoxic agents through changes at the genetic, epigenetic and micro-environment levels. Therefore, therapeutic strategies targeting CSCs hold great potential as an avenue for cancer treatment. Aptamers or "chemical antibodies" are a group of single-stranded nucleic acid (DNA or RNA) oligonucleotides with distinctive properties such as smaller size, lower toxicity and less immunogenicity compared to conventional antibodies. They have been frequently used to deliver therapeutic payloads to cancer cells and have achieved encouraging anti-tumour effects. This review discusses progress in CSC evolution theory and the role of aptamers to target CSCs for cancer treatment. Challenges of aptamer-mediated CSC targeting approaches are also discussed.

Aptamer-siRNA Chimeras: Discovery, Progress, and Future Prospects

Synthetic nucleic acid ligands (aptamers) have emerged as effective delivery tools for many therapeutic oligonucleotide-based drugs, including small interfering RNAs (siRNAs). In this review, we summarize recent progress in the aptamer selection technology that has made possible the identification of cell-specific, cell-internalizing aptamers for the cell-targeted delivery of therapeutic oligonucleotides. In addition, we review the original, proof-of-concept aptamer-siRNA delivery studies and discuss recent advances in aptamer-siRNA conjugate designs for applications ranging from cancer therapy to the development of targeted antivirals. Challenges and prospects of aptamer-targeted siRNA drugs for clinical development are further highlighted.

Therapeutic applications of synthetic nucleic acid aptamers

It is possible to generate oligonucleotide aptamers for a wide variety of target molecules using a process known as Systematic Evolution of Ligands by Exponential Enrichment. Researchers have successfully generated aptamers which recognize specific metal ions, small chemical compounds, peptides, proteins, saccharides, and even whole cells. Aptamers show much promise as future therapeutics and as drug targeting agents. A particularly active area of aptamer research in the past two years was development of aptamer based cancer therapeutics and development of aptamer based cancer drug delivery systems. Aptamers were also used to address inflammatory diseases, infectious diseases, cardiovascular diseases, and eye diseases.

Is Ep-CAM Expression a Diagnostic and Prognostic Biomarker for Colorectal Cancer? A Systematic Meta-Analysis

Background

Cancer stem cell (CSC) epithelial cell adhesion molecule (Ep-CAM) is frequently expressed in colorectal cancer (CRC). However, the clinical significance of Ep-CAM expression in CRC is not clear. This study evaluated whether Ep-CAM provided valuable insight as a molecular biomarker for CRC diagnosis and prognosis and the potential of Ep-CAM as a novel therapeutic target in CRC.

Methods

Publications were selected online using electronic databases. The pooled odds ratios (ORs) or hazard ratios (HRs) with their 95% confidence intervals (95% CIs), and the combined sensitivity, specificity, and area under the curve (AUC) were calculated and summarized.

Results

Eleven eligible articles published in English involving 4561 cases were analyzed in this study. Ep-CAM expression was significantly higher in CRC compared with normal controls, and its overexpression was negatively linked to tumor differentiation, tumor stage, vascular invasion, depth of tumor invasion, lymph node metastasis, distant metastasis, and tumor budding in CRC patients. The loss of Ep-CAM expression positively correlated with these characteristics. Multivariate analysis of loss of Ep-CAM expression correlated with a poor prognosis in disease-free survival (DFS), disease-specific survival (DSS), and overall survival (OS). The pooled sensitivity, specificity and AUC values of Ep-CAM expression in patients with CRC vs. normal controls were 0.93, 0.90, and 0.94, respectively.

Conclusions

The present findings suggest that Ep-CAM expression may be associated with CRC carcinogenesis, while the loss of Ep-CAM expression is correlated with the progression, metastasis, and poor prognosis of CRC. Ep-CAM expression may be a useful biomarker for the clinical diagnosis of CRC.

•

Cancer stem cell (CSC) epithelial cell adhesion molecule (Ep-CAM) expression may correlate with CRC tumorigenesis.

•

Frequent overexpression of Ep-CAM was a favorable factor for CRC progression and metastasis.

•

Loss of Ep-CAM expression correlated with the progression, metastasis, and poor prognosis of patients with CRC.

•

Ep-CAM expression may be a potential marker for the detection of CRC.

Ep-CAM expression was reported in CRC, but no clear direction for the diagnostic and prognostic effects of Ep-CAM expression was documented in patients with CRC. We performed a systematic meta-analysis of the existing evidence to determine the clinical significance of Ep-CAM expression in CRC. The findings indicated that Ep-CAM expression was associated with CRC risk. Frequent overexpression of Ep-CAM correlated with a decreased risk of CRC progression and metastasis, and loss of Ep-CAM expression played an important role in CRC progression, metastasis and prognosis. The detection of Ep-CAM expression may be a promising biomarker in diagnosing CRC.

Recent progresses in biomedical applications of aptamer-functionalized systems

Aptamers, known as "chemical antibodies" are screened via a combinational technology of systematic evolution of ligands by exponential enrichment (SELEX). Due to their specific targeting ability, high binding affinity, low immunogenicity and easy modification, aptamer-functionalized systems have been extensively applied in various fields and exhibit favorable results. However, there is still a long way for them to be commercialized, and few aptamer-functionalized systems have yet successfully entered clinical and industrial use. Thus, it is necessary to overview the recent research progresses of aptamer-functionalized systems for the researchers to improve or design novel and better aptamer-functionalized systems. In this review, we first introduce the recent progresses of aptamer-functionalized systems' applications in biosensing, targeted drug delivery, gene therapy and cancer cell imaging, followed by a discussion of the challenges faced with extensive applications of aptamer-functionalized systems and speculation of the future prospects of them.

Targeting HMGA2 in Retinoblastoma Cells in vitro Using the Aptamer Strategy

High-mobility group A2 (HMGA2) protein regulates retinoblastoma (RB) cancer cell proliferation. Here, a stable phosphorothioate-modified HMGA2 aptamer was used to block HMGA2 protein function in RB cells. HMGA2-aptamer internalisation in RB cells (Y79, Weri Rb1) and non-neoplastic human retinal cells (MIO-M1) were optimised. Aptamer induced dose-dependent cytotoxicity in RB cancer cells (0.25-1.5 µM). Increased expression of TGFβ, SMAD4, CDH1, BAX, CASP 3, PARP mRNA and decreased SNAI1, Bcl2 mRNA levels in aptamer-treated RB cells suggests the activation of TGFβ-SMAD4-mediated apoptotic pathway. Synergistic effect with etoposide was observed in aptamer treated RB cells (p value ≤0.05). No significant toxicity was observed in non-neoplastic retinal cells.

EpCAM aptamer-functionalized mesoporous silica nanoparticles for efficient colon cancer cell-targeted drug delivery

Targeted delivery of anticancer agents by functional nanoparticles is an attractive strategy to increase their therapeutic efficacy while reducing toxicity. In this work, doxorubicin (DOX)-loaded mesoporous silica nanoparticles (MSNs) were modified with aptamer (Ap) against the epithelial cell adhesion molecule (EpCAM) for targeted delivery of DOX to colon cancer cells. These nanoparticles (Ap-MSN-DOX) were characterized by particle size, zeta potential, aptamer conjugation efficiency, drug encapsulation efficiency, and drug release properties. The in vitro cell recognition, cellular uptake, EpCAM protein inhibition efficiency, and cytotoxicity of Ap-MSN-DOX were also studied. Results demonstrated that EpCAM conjugation increased binding of Ap-MSN-DOX to EpCAM over-expressing SW620 colon cancer cells but not EpCAM-negative Ramos cells, resulting in enhanced cellular uptake and increased cytotoxicity of the DOX in SW620 cells when compared to non-Ap-modified nanoparticles (MSN-DOX). Additionally, Ap-MSN-DOX exhibited significant inhibition effects on the expression of EpCAM on SW620 cells. These results suggested that Ap-MSN-DOX has the potential for the targeted delivery of therapeutic agents into EpCAM positive colon cancer cells to improve therapeutic index while reducing side effects.

Targeting Cancer Cells Using LNA-Modified Aptamer-siRNA Chimeras

Aptamers are chimerized with drug or antisense oligos or nanoparticles to generate targeted therapeutics for cancer. Aptamer chimerized siRNA rescues nonspecific delivery and, thereby, enhances the availability of siRNA to target cells. EpCAM RNA aptamer (EpApt or Ep) has potential for siRNA chimerization due to its secondary structure. Stathmin and survivin proteins are reported to aid oncogenicity in retinoblastoma (RB), breast cancer and other cancers. Thus, chimerization of EpCAM Apt with siRNA against survivin and stathmin, respectively, was performed by incorporating Locked Nucleic Acid (LNA) modification. The LNA-modified chimeric aptamers were stable until 96 h and got internalized into RB, WERI-Rb1 and breast cancer, MDAMB453 cell lines. The constructs were studied using the recombinant dicer enzyme for the siRNA generation. Quantitative polymerase chain reaction and immunofluorescence by microscopic analysis of chimeras in vitro exhibited silencing of stathmin and survivin in the RB and breast cancer model. The chimeric constructs showed significant inhibition of cell proliferation of breast cancer cells. Thus, LNA-modified aptamer-based siRNA delivery aids in cell targeting and necessitates further studies in animal models.