Apurinic/apyrimidinic Endonuclease 1 Research Articles

Selective anti-tumor activity of glutathione-responsive abasic site trapping agent in anaplastic thyroid carcinoma.

Anaplastic thyroid carcinoma (ATC) is a rare but highly aggressive thyroid cancer with poor prognosis. Killing cancer cells by inducing DNA damage or blockage of DNA repair is a promising strategy for chemotherapy. It is reported that aldehyde-reactive alkoxyamines can capture the AP sites, one of the most common DNA lesions, and inhibit apurinic/apyrimidinic endonuclease 1(APE1)-mediated base excision repair (BER), leading to cell death. Whether this strategy can be employed for ATC treatment is rarely investigated. The aim of this study is to exploit GSH-responsive AP site capture reagent (AP probe-net), which responses to the elevated glutathione (GSH) levels in the tumor micro-environment (TME), releasing reactive alkoxyamine to trap AP sites and block the APE1-mediated BER for targeted anti-tumor activity against ATC. In vitro experiments, including MTT andγ-H2AX assays, demonstrate their selective cytotoxicity towards ATC cells over normal thyroid cells. Flow cytometry analysis suggests that AP probe-net arrests the cell cycle in the G2/M phase and induces apoptosis. Western blotting (WB) results show that the expression of apoptotic protein increased with the increased concentration of AP probe-net. Further in vivo experiments reveal that the AP probe-net has a good therapeutic effect on subcutaneous tumors of the ATC cells. In conclusion, taking advantage of the elevated GSH in TME, our study affords a new strategy for targeted chemotherapy of ATC with high selectivity and reduced adverse effects.

Selective anti-tumor activity of glutathione-responsive abasic site trapping agent in anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is a rare but highly aggressive thyroid cancer with poor prognosis. Killing cancer cells by inducing DNA damage or blockage of DNA repair is a promising strategy for chemotherapy. It is reported that aldehyde-reactive alkoxyamines can capture the AP sites, one of the most common DNA lesions, and inhibit apurinic/apyrimidinic endonuclease 1(APE1)-mediated base excision repair (BER), leading to cell death. Whether this strategy can be employed for ATC treatment is rarely investigated. The aim of this study is to exploit GSH-responsive AP site capture reagent (AP probe-net), which responses to the elevated glutathione (GSH) levels in the tumor micro-environment (TME), releasing reactive alkoxyamine to trap AP sites and block the APE1-mediated BER for targeted anti-tumor activity against ATC. In vitro experiments, including MTT andγ-H2AX assays, demonstrate their selective cytotoxicity towards ATC cells over normal thyroid cells. Flow cytometry analysis suggests that AP probe-net arrests the cell cycle in the G2/M phase and induces apoptosis. Western blotting (WB) results show that the expression of apoptotic protein increased with the increased concentration of AP probe-net. Further in vivo experiments reveal that the AP probe-net has a good therapeutic effect on subcutaneous tumors of the ATC cells. In conclusion, taking advantage of the elevated GSH in TME, our study affords a new strategy for targeted chemotherapy of ATC with high selectivity and reduced adverse effects.

Synergistic powering of DNA walker movement by endogenous dual enzymes for constructing dual-mode biosensors

To achieve highly sensitive and reliable detection of apurinic/apyrimidinic endonuclease 1 (APE1), a critical cancer diagnostic biomarker, we designed a DNA walker-based dual-mode biosensor, utilizing cellular endogenous dual enzymes (APE 1 and Flap endonuclease 1 (FEN 1)) to collaborate in activating and propelling DNA walker motion on DNA-functionalized Au nanoparticles. Incorporating both fluorescence and electrochemical detection modes, this system leverages signal amplification from DNA walker movement and cascade amplification through tandem hybridization chain reactions (HCR), achieving highly sensitive detection of APE 1. In the fluorescence mode, continuous DNA walker movement, initiated by APE1 and driven by FEN1, generates a robust signal response within a concentration range of 0.01–500 U mL−1, presenting a good linearity in the concentration range of 0.01–10 U mL−1, with a detection limit of 0.01 U mL−1. In the electrochemical detection module, the cascade upstream DNA walker and downstream HCR dual signal amplification strategy further enhances the sensitivity of APE1 detection, extending the linear range to 0.01–50 U mL−1 and reducing the detection limit to 0.002 U mL−1. Rigorous validation demonstrates the biosensor's specificity and anti-interference capability against multiple enzymes. Moreover, it effectively distinguishes cancer cells from normal cell lysates, exhibiting excellent stability and consistency in the dual-modes. Overall, our findings underscore the efficacy of the developed dual-mode biosensor for detecting APE1 in serum and cell lysates samples, indicating its potential for clinical applications in disease diagnosis.

Nanoconfined Silver Nanoclusters Combined with X-Shaped DNA Recognizer-Triggered Cascade Amplification for Electrochemiluminescence Detection of APE1.

Apurinic/apyrimidinic endonuclease 1 (APE1), as a vital base excision repair enzyme, is essential for maintaining genomic integrity and stability, and its abnormal expression is closely associated with malignant tumors. Herein, we constructed an electrochemiluminescence (ECL) biosensor for detecting APE1 activity by combining nanoconfined ECL silver nanoclusters (Ag NCs) with X-shaped DNA recognizer-triggered cascade amplification. Specifically, the Ag NCs were prepared and confined in the glutaraldehyde-cross-linked chitosan hydrogel network using the one-pot method, resulting in a strong ECL response and exceptional stability in comparison with discrete Ag NCs. Furthermore, the self-assembled X-shaped DNA recognizers were designed for APE1 detection, which not only improved reaction kinetics due to the ordered arrangement of recognition sites but also achieved high sensitivity by utilizing the recognizer-triggered cascade amplification of strand displacement amplification (SDA) and DNAzyme catalysis. As expected, this biosensor achieved sensitive ECL detection of APE1 in the range of 1.0 × 10-3 U·μL-1 to 1.0 × 10-10 U·μL-1 with the detection limit of 2.21 × 10-11 U·μL-1, rendering it a desirable approach for biomarker detection.

An Enzymatically Activated and Catalytic Hairpin Assembly-Driven Intelligent AND-Gated DNA Network for Tumor Molecular Imaging.

Due to the potential off-tumor signal leakage and limited biomarker content, there is an urgent need for stimulus-responsive and amplification-based tumor molecular imaging strategies. Therefore, two tetrahedral framework DNA (tFNA-Hs), tFNA-H1AP, and tFNA-H2, were rationally engineered to form a polymeric tFNA network, termed an intelligent DNA network, in an AND-gated manner. The intelligent DNA network was designed for tumor-specific molecular imaging by leveraging the elevated expression of apurinic/apyrimidinic endonuclease 1 (APE1) in tumor cytoplasm instead of normal cells and the high expression of miRNA-21 in tumor cytoplasm. The activation of tFNA-H1AP can be achieved through specific recognition and cleavage by APE1, targeting the apurinic/apyrimidinic site (AP site) modified within the stem region of hairpin 1 (H1AP). Subsequently, miRNA-21 facilitates the hybridization of activated H1AP on tFNA-H1AP with hairpin 2 (H2) on tFNA-H2, triggering a catalytic hairpin assembly (CHA) reaction that opens the H1AP at the vertices of tFNA-H1AP to bind with H2 at the vertices of tFNA-H2 and generate fluorescence signals. Upon completion of hybridization, miRNA-21 is released, initiating the subsequent cycle of the CHA reaction. The AND-gated intelligent DNA network can achieve specific tumor molecular imaging in vivo and also enables risk stratification of neuroblastoma patients.

APE1 regulates mitochondrial DNA damage repair after experimental subarachnoid haemorrhage in vivo and in vitro

BackgroundSubarachnoid haemorrhage (SAH) can result in a highly unfavourable prognosis. In recent years, the study of SAH has focused on early brain injury (EBI), which is a crucial progress that...

AND Logic-Gate-Based Dual-Locking Probe System for the Sensitive Detection of microRNA and APE1.

MicroRNA (miRNA) and apurinic/apyrimidinic endonuclease 1 (APE1) have been reported to be closely associated with cancers, making them potential crucial biomarkers and therapeutic targets. However, focusing on the detection of a single target is not conducive to the diagnosis and prognosis assessment of diseases. In this study, an AND logic-gate-based dual-locking hairpin-mediated catalytic hairpin assembly (DL-CHA) was developed for sensitive and specific detection of microRNA and APE1. By addition of a lock to each of the hairpins, with APE1 and microRNA serving as keys, fluorescence signals could only be detected in the presence of simultaneous stimulation by APE1 and miRNA-224. This indicated that the biosensor could operate as an AND logic gate. DL-CHA exhibited advantages such as a low background, rapid response, and high logic capability. Therefore, the biosensor serves as a novel approach to cancer diagnosis with significant potential applications.

Endogenous Enzyme-Driven Amplified DNA Nanocage Probe for Selective and Sensitive Imaging of Mature MicroRNAs in Living Cancer Cells.

Selective and sensitive imaging of intracellular mature microRNAs (miRNAs) is of great importance for biological process study and medical diagnostics. However, this goal remains challenging because of the interference of precursor miRNAs (pre-miRNAs) and the low abundance of mature miRNAs. Herein, we develop an endogenous enzyme-driven amplified DNA nanocage probe (Acage) for the selective and sensitive imaging of mature miRNAs in living cells. The Acage consists of a microRNA-responsive probe, an endogenous enzyme-driven fuel strand, and a DNA nanocage framework with an inner cavity. Benefiting from the size selectivity of DNA nanocage, smaller mature miRNAs rather than larger pre-miRNAs are allowed to enter the cavity of DNA nanocage for molecular recognition; thus, Acage can significantly reduce the signal interference of pre-miRNAs. Moreover, with the driving force of an endogenous enzyme apurinic/apyrimidinic endonuclease 1 (APE1) for efficient signal amplification, Acage enables sensitive intracellular miRNA imaging without an additional external intervention. With these features, Acage was successfully applied for intracellular imaging of mature miRNAs during drug treatment. We believe that this strategy provides a promising pathway for better understanding the functions of mature microRNAs in biological processes and medical diagnostics.

A GSH/APE1-controlled framework nucleic acids based entropy-driven DNA circuit for high-contrast miRNAs imaging

Catalytic DNA circuits show great potential for precise intracellular imaging. However, their selectivity and efficiency are often hindered by low anti-interference performance in the cytoplasm’s complex environment. Thus, designing DNA circuits that exhibit enhanced stability and specific activation is crucial for the accurate intracellular biomolecule imaging. Herein, we proposed a framework nucleic acids based endogenously activated entropy-driven catalytic (EDC) circuit, FEED, for in vivo microRNA imaging with enhanced selectivity and efficiency. To mitigate undesired signal leakage before reaching the target cells, the dominating EDC circuitry fuel strand was initially blocked with a disulfide bond modified DNA strand, and the target recognition site of sensing module was also closed by apurinic/apyrimidinic (AP) sites. This configuration allowed selective activation of the EDC by endogenous GSH and human apurinic/apyrimidinic endonuclease 1 (APE1) in cancer cells, facilitating high-contrast miRNA imaging. Additionally, the integrating a distinctive DNA tetrahedral structure into the EDC circuit enhances both biostability and cellular reaction efficacy. This in-site activation FEED circuit offers a programmable and modular amplification strategy for biomarker detection in live cells and mice, providing a potentially valuable molecular tool for living systems.

Fluorogenic Aptamer-Based Hybridization Chain Reaction for Signal-Amplified Imaging of Apurinic/Apyrimidinic Endonuclease 1 in Living Cells.

A fluorogenic aptamer (FA)-based hybridization chain reaction (HCR) could provide a sensitive and label-free signal amplification method for imaging molecules in living cells. However, existing FA-HCR methods usually face some problems, such as a complicated design and significant background leakage, which greatly limit their application. Herein, we developed an FA-centered HCR (FAC-HCR) method based on a remote toehold-mediated strand displacement reaction. Compared to traditional HCRs mediated by four hairpin probes (HPs) and two HPs, the FAC-HCR displayed significantly decreased background leakage and improved sensitivity. Furthermore, the FAC-HCR was used to test a non-nucleic acid target, apurinic/apyrimidinic endonuclease 1 (APE1), an important BER-involved endonuclease. The fluorescence analysis results confirmed that FAC-HCR can reach a detection limit of 0.1174 U/mL. By using the two HPs for FAC-HCR with polyetherimide-based nanoparticles, the activity of APE1 in living cells can be imaged. In summary, this study could provide a new idea to design an FA-based HCR and improve the performance of HCRs in live cell imaging.

Oxidatively-induced DNA base damage and base excision repair abnormalities in siblings of individuals with bipolar disorder DNA damage and repair in bipolar disorder

Previous evidence suggests elevated levels of oxidatively-induced DNA damage, particularly 8-hydroxy-2’-deoxyguanosine (8-OH-dG), and abnormalities in the repair of 8-OH-dG by the base excision repair (BER) in bipolar disorder (BD). However, the genetic disposition of these abnormalities remains unknown. In this study, we aimed to investigate the levels of oxidatively-induced DNA damage and BER mechanisms in individuals with BD and their siblings, as compared to healthy controls (HCs). 46 individuals with BD, 41 siblings of individuals with BD, and 51 HCs were included in the study. Liquid chromatography-tandem mass spectrometry was employed to evaluate the levels of 8-OH-dG in urine, which were then normalized based on urine creatinine levels. The real-time-polymerase chain reaction was used to measure the expression levels of 8-oxoguanine DNA glycosylase 1 (OGG1), apurinic/apyrimidinic endonuclease 1 (APE1), poly ADP-ribose polymerase 1 (PARP1), and DNA polymerase beta (POLβ). The levels of 8-OH-dG were found to be elevated in both individuals with BD and their siblings when compared to the HCs. The OGG1 and APE1 expressions were downregulated, while POLβ expressions were upregulated in both the patient and sibling groups compared to the HCs. Age, smoking status, and the number of depressive episodes had an impact on APE1 expression levels in the patient group while body mass index, smoking status, and past psychiatric history had an impact on 8-OH-dG levels in siblings. Both individuals with BD and unaffected siblings presented similar abnormalities regarding oxidatively-induced DNA damage and BER, suggesting a link between abnormalities in DNA damage/BER mechanisms and familial susceptibility to BD. Our findings suggest that targeting the oxidatively-induced DNA damage and BER pathway could offer promising therapeutic strategies for reducing the risk of age-related diseases and comorbidities in individuals with a genetic predisposition to BD.

DNA Walker-Driven Mass Nanotag Assembly System for Simultaneously Profiling Dual Markers of Oxidative Stress at Different Cellular Locations.

Simultaneous profiling of redox-regulated markers at different cellular sublocations is of great significance for unraveling the upstream and downstream molecular mechanisms of oxidative stress in living cells. Herein, by synchronizing dual target-triggered DNA machineries in one nanoentity, we engineered a DNA walker-driven mass nanotag (MNT) assembly system (w-MNT-AS) that can be sequentially activated by oxidative stress-associated mucin 1 (MUC1) and apurinic/apyrimidinic endonuclease 1 (APE1) from plasma membrane to cytoplasm and induce recycled assembly of MNTs for multiplex detection of the two markers by matrix-assisted laser desorption ionization mass spectrometry (MALDI MS). In the working cascade, the sensing process governs the separate activation of w-MNT-AS by MUC1 and APE1 in diverse locations, while the assembly process contributes to the parallel amplification of the ion signal of the characteristic mass tags. In this manner, the differences between MCF-7, HeLa, HepG2, and L02 cells in membrane MUC1 expression and cytoplasmic APE1 activation were fully characterized. Furthermore, the oxidative stress level and dynamics caused by exogenous H2O2, doxorubicin, and simvastatin were comprehensively demonstrated by tracking the fate of the two markers across different cellular locations. The proposed w-MNT-AS coupled MS method provides an effective route to probe multiple functional molecules that lie at different locations while participating in the same cellular event, facilitating the mechanistic studies on cellular response to oxidative stress and other disease-related cellular processes.

Nanoscale Interaction of Endonuclease APE1 with DNA.

Apurinic/apyrimidinic endonuclease 1 (APE1) is involved in DNA repair and transcriptional regulation mechanisms. This multifunctional activity of APE1 should be supported by specific structural properties of APE1 that have not yet been elucidated. Herein, we applied atomic force microscopy (AFM) to characterize the interactions of APE1 with DNA containing two well-separated G-rich segments. Complexes of APE1 with DNA containing G-rich segments were visualized, and analysis of the complexes revealed the affinity of APE1 to G-rich DNA sequences, and their yield was as high as 53%. Furthermore, APE1 is capable of binding two DNA segments leading to the formation of loops in the DNA-APE1 complexes. The analysis of looped APE1-DNA complexes revealed that APE1 can bridge G-rich segments of DNA. The yield of loops bridging two G-rich DNA segments was 41%. Analysis of protein size in various complexes was performed, and these data showed that loops are formed by APE1 monomer, suggesting that APE1 has two DNA binding sites. The data led us to a model for the interaction of APE1 with DNA and the search for the specific sites. The implication of these new APE1 properties in organizing DNA, by bringing two distant sites together, for facilitating the scanning for damage and coordinating repair and transcription is discussed.

The DNA-repair protein APE1 participates with hnRNPA2B1 to motif-enriched and prognostic miRNA secretion.

The base excision repair (BER) Apurinic/apyrimidinic endonuclease 1 (APE1) enzyme is endowed with several non-repair activities including miRNAs processing. APE1 is overexpressed in many cancers but its causal role in the tumorigenic processes is largely unknown. We recently described that APE1 can be actively secreted by mammalian cells through exosomes. However, APE1 role in EVs or exosomes is still unknown, especially regarding a putative regulatory function on vesicular small non-coding RNAs. Through dedicated transcriptomic analysis on cellular and vesicular small RNAs of different APE1-depleted cancer cell lines, we found that miRNAs loading into EVs is a regulated process, dependent on APE1, distinctly conveying RNA subsets into vesicles. We identified APE1-dependent secreted miRNAs characterized by enriched sequence motifs and possible binding sites for APE1. In 33 out of 34 APE1-dependent-miRNA precursors, we surprisingly found EXO-motifs and proved that APE1 cooperates with hnRNPA2B1 for the EV-sorting of a subset of miRNAs, including miR-1246, through direct binding to GGAG stretches. Using TCGA-datasets, we showed that these miRNAs identify a signature with high prognostic significance in cancer. In summary, we provided evidence that the ubiquitous DNA-repair enzyme APE1 is part of the EV protein cargo with a novel post-transcriptional role for this ubiquitous DNA-repair enzyme that could explain its role in cancer progression. These findings could open new translational perspectives in cancer biology.

Endogenous AND Logic DNA Nanomachine for Highly Specific Cancer Cell Imaging.

Intracellular cancer-related biomarker imaging strategy has been used for specific identification of cancer cells, which was of great importance to accurate cancer clinical diagnosis and prognosis studies. Localized DNA circuits with improved sensitivity showed great potential for intracellular biomarkers imaging. However, the ability of localized DNA circuits to specifically image cancer cells is limited by off-site signal leakage associated with a single-biomarker sensing strategy. Herein, we integrated the endogenous enzyme-powered strategy with logic-responsive and localized signal amplifying capability to construct a self-assembled endogenously AND logic DNA nanomachine (EDN) for highly specific cancer cell imaging. When the EDN encountered a cancer cell, the overexpressed DNA repairing enzyme apurinic/apyrimidinic endonuclease 1 (APE1) and miR-21 could synergistically activate a DNA circuit via cascaded localized toehold-mediated strand displacement (TMSD) reactions, resulting in amplified fluorescence resonance energy transfer (FRET) signal. In this strategy, both endogenous APE1 and miR-21, served as two "keys" to activate the AND logic operation in cancer cells to reduce off-tumor signal leakage. Such a multiplied molecular recognition/activation nanomachine as a powerful toolbox realized specific capture and reliable imaging of biomolecules in living cancer cells.

An enzymatically activated self-powered and self-recycled strategy for in situ tumor cell-specific molecular imaging

Specific imaging of tumor cells with high sensitivity is urgently needed for evaluating the risk of tumor metastasis and progression. However, traditional tumor cell imaging strategies are still restricted by limited tumor specificity and sensitivity due to off-tumor signal leakage and a lower content of the targets. Therefore, a self-powered and self-recycled strategy based on molecular beacon (MB) hybridized on tetrahedral framework DNA (E-MB-tFNA) using the endogenous enzyme, apurinic/apyrimidinic endonuclease 1 (APE1), was rationally developed for tumor cell-specific molecular imaging with superior spatial specificity and improved sensitivity. The apurinic/apyrimidinic site (AP site) can be specifically recognized and cleaved by APE1, and was modified on the stem and loop region of E-MB-tFNA. The resultant E-MB-tFNA can be specifically recognized and cleaved by APE1 in the cytoplasm, which is overexpressed in tumor cells compared to normal cells. In particular, once APE1 cleaves the AP site on the stem region (double-stranded DNA) of E-MB-tFNA, the self-powered and self-recycled sequences modified on the stem region of E-MB-tFNA is freed to hybridize with the loop region of E-MB-tFNA, prompting APE1 to further hydrolyze the E-MB-tFNA loop region and generate fluorescence signals. In addition, the self-powered and self-recycled sequences can be hybridized with other E-MB-tFNA to continuously and cyclically amplify the fluorescence signal. The experimental results of this study showed that the E-MB-tFNA has the capability to monitor drug resistance and achieve guided precision surgical excision in vivo with superior spatial specificity and improved sensitivity. In particular, E-MB-tFNA can realize the risk classification of neuroblastoma patients in clinical plasma.

Imaging multiple DNA repair enzymes in living cells based on framework nucleic acid fluorescence nanoprobe

DNA repair enzymes play pivotal roles in DNA damage repair. Imaging multiple DNA repair enzymes in living cells is significant for DNA damage repair-related biological study and disease diagnosis. Here, we constructed a framework nucleic acids (FNAs) fluorescent nanoprobe for imaging multiple DNA repair enzymes in living cells. Uracil DNA glycosylase (UDG) and human apurinic/apyrimidinic endonuclease 1 (APE1) were used as the target analytes. Two double-stranded DNA probes (dsDNA1 and dsDNA2) were designed. dsDNA1 contained four uracil (U) bases for UDG recognition and was labeled with black hole quencher2 (BHQ2) /cyanine5 (Cy5). dsDNA2 contained one apurinic/apyrimidinic (AP) site for APE1 recognition and was labeled with black hole quencher1 (BHQ1) /fluorophore carboxyfluorescein (FAM). To obtain the FNAs fluorescent nanoprobe, dsDNA1 and dsDNA2 were attached to two vertices of a DNA tetrahedron (a type of FNAs). Under the action of UDG and APE1, dsDNA1 and dsDNA2 were both dissociated, generating fluorescence of Cy5 and FAM. Among them, Cy5 indicated the activity of UDG and FAM indicated the activity of APE1. This method had good sensitivity to UDG and APE1, and the detection limits were 0.0012 U/mL and 0.057 U/mL, respectively. This method also exhibited high selectivity for UDG and APE1. When the FNAs fluorescent nanoprobe was endocytosed, it had little toxicity to normal and cancer cells. Furthermore, this method successfully achieved multiple imaging UDG and APE1 in cancer cells. This study provides a novel strategy for imaging multiple DNA repair enzymes and holds great potential in biological applications and clinical diagnosis.

Construction of an Enzymatically Controlled DNA Nanomachine for One-Step Imaging of Telomerase in Living Cells.

Telomerase is a basic reverse transcriptase that maintains the telomere length in cells, and accurate and specific sensing of telomerase in living cells is critical for medical diagnostics and disease therapeutics. Herein, we demonstrate for the first time the construction of an enzymatically controlled DNA nanomachine with endogenous apurinic/apyrimidinic endonuclease 1 (APE1) as a driving force for one-step imaging of telomerase in living cells. The DNA nanomachine is designed by rational engineering of substrate probes and reporter probes embedded with an enzyme-activatable site (i.e., AP site) and their subsequent assembly on a gold nanoparticle (AuNP). Upon recognition and cleavage of the AP site in the substrate probe by APE1, the loop of the substrate probe unfolds, exposing telomeric primer (TP) with the 3'-OH end. Subsequently, the TP is elongated by telomerase at the 3'-OH end to generate a long telomeric product. The resultant telomeric product acts as a swing arm that can hybridize with a reporter probe to initiate the APE1-powered walking reaction, ultimately generating a significantly enhanced fluorescence signal. Notably, endogenous APE1 is used as the driving force of the DNA nanomachine, avoiding the introduction of exogenous auxiliary cofactors into the cellular microenvironment. Owing to the high kinetics and high amplification efficiency of the APE1-powered DNA nanomachine, this strategy enables one-step sensitive sensing of telomerase in vitro and in vivo. It can successfully discriminate telomerase activity between cancer cells and normal cells, screen telomerase inhibitors, and monitor the variations of telomerase activity in living cells, offering a prospective platform for molecular diagnostics and drug discovery.

APE1 inhibition enhances ferroptotic cell death and contributes to hepatocellular carcinoma therapy.

Ferroptosis, a regulated form of cell death triggered by iron-dependent lipid peroxidation, has emerged as a promising therapeutic strategy for cancer treatment, particularly in hepatocellular carcinoma (HCC). However, the mechanisms underlying the regulation of ferroptosis in HCC remain to be unclear. In this study, we have identified a novel regulatory pathway of ferroptosis involving the inhibition of Apurinic/apyrimidinic endonuclease 1 (APE1), a key enzyme with dual functions in DNA repair and redox regulation. Our findings demonstrate that inhibition of APE1 leads to the accumulation of lipid peroxidation and enhances ferroptosis in HCC. At the molecular level, the inhibition of APE1 enhances ferroptosis which relies on the redox activity of APE1 through the regulation of the NRF2/SLC7A11/GPX4 axis. We have identified that both genetic and chemical inhibition of APE1 increases AKT oxidation, resulting in an impairment of AKT phosphorylation and activation, which leads to the dephosphorylation and activation of GSK3β, facilitating the subsequent ubiquitin-proteasome-dependent degradation of NRF2. Consequently, the downregulation of NRF2 suppresses SLC7A11 and GPX4 expression, triggering ferroptosis in HCC cells and providing a potential therapeutic approach for ferroptosis-based therapy in HCC. Overall, our study uncovers a novel role and mechanism of APE1 in the regulation of ferroptosis and highlights the potential of targeting APE1 as a promising therapeutic strategy for HCC and other cancers.

Label-free colorimetric detection platform based on catalytic hairpin self-assembly and G-quadruplex/hemin DNAzyme for comprehensive biomarker profiling

The expression level of human apurinic/apyrimidinic endonuclease 1 (APE1) is closely associated with the onset of various diseases, establishing it as a crucial clinical biomarker and a target in anti-cancer efforts. This study accomplished colorimetric and visual detection of APE1 by harnessing its endonuclease activity through catalytic hairpin self-assembly (CHA) and G-quadruplex/hemin DNAzyme. Optimization of the freedom degrees of the G-rich sequence significantly improved the detection performance of the strategy by influencing DNAzyme formation. Additionally, we replaced the signal reporting system with a molecular beacon to develop a fluorescence detection strategy, which served as an extension of the signal amplification system for validation and signal readout. The fluorescent probe method achieved a detection limit of 3.37 × 10−4 U/mL, while the colorimetric method yielded a detection limit of 6.5 × 10−3 U/mL, with a linear range spanning from 0.01 to 0.25 U/mL. Subsequently, the colorimetric approach effectively assessed APE1 activity in biological samples and facilitated the screening of APE1 activity inhibitors. Furthermore, this CHA/G-quadruplex/hemin DNAzyme strategy was adapted for the colorimetric detection of adenosine, showcasing its broad applicability across various biomarkers. The developed colorimetric analytical strategy represents a pivotal biosensing platform for diagnosing and treating diseases.