Apurinic/Apyrimidinic Endonuclease 1/Redox Factor-1 Could Serve as a Potential Serological Biomarker for the Diagnosis and Prognosis of Oral Squamous Cell Carcinoma

APE-1/Ref-1 Inhibition Blocks Malignant Pleural Mesothelioma Cell Proliferation and Migration: Crosstalk between Oxidative Stress and Epithelial Mesenchymal Transition (EMT) in Driving Carcinogenesis and Metastasis

Malignant pleural mesothelioma (MPM) is an aggressive cancer associated with asbestos exposure. MPM pathogenesis has been related both to oxidative stress, evoked by and in response to asbestos fibers exposure, and epithelial mesenchymal transition (EMT), an event induced by oxidative stress itself and related to cancer proliferation and metastasis. Asbestos-related primary oxidative damage is counteracted in the lungs by various redox-sensitive factors, often hyperactivated in some cancers. Among these redox-sensitive factors, Apurinic-apyrimidinic endonuclease 1 (APE-1)/Redox effector factor 1 (Ref-1) has been demonstrated to be overexpressed in MPM and lung cancer, but the molecular mechanism has not yet been fully understood. Moreover, asbestos exposure has been associated with induced EMT events, via some EMT transcription factors, such as Twist, Zeb-1 and Snail-1, in possible crosstalk with oxidative stress and inflammation events. To demonstrate this hypothesis, we inhibited/silenced Ref-1 in MPM cells; as a consequence, both EMT (Twist, Zeb-1 and Snail-1) markers and cellular migration/proliferation were significantly inhibited. Taken as a whole, these results show, for the first time, crosstalk between oxidative stress and EMT in MPM carcinogenesis and invasiveness, thus improving the knowledge to better address a preventive and therapeutic approach against this aggressive cancer.

Revisiting Two Decades of Research Focused on Targeting APE1 for Cancer Therapy: The Pros and Cons

APE1 is an essential endodeoxyribonuclease of the base excision repair pathway that maintains genome stability. It was identified as a pivotal factor favoring tumor progression and chemoresistance through the control of gene expression by a redox-based mechanism. APE1 is overexpressed and serum-secreted in different cancers, representing a prognostic and predictive factor and a promising non-invasive biomarker. Strategies directly targeting APE1 functions led to the identification of inhibitors showing potential therapeutic value, some of which are currently in clinical trials. Interestingly, evidence indicates novel roles of APE1 in RNA metabolism that are still not fully understood, including its activity in processing damaged RNA in chemoresistant phenotypes, regulating onco-miRNA maturation, and oxidized RNA decay. Recent data point out a control role for APE1 in the expression and sorting of onco-miRNAs within secreted extracellular vesicles. This review is focused on giving a portrait of the pros and cons of the last two decades of research aiming at the identification of inhibitors of the redox or DNA-repair functions of APE1 for the definition of novel targeted therapies for cancer. We will discuss the new perspectives in cancer therapy emerging from the unexpected finding of the APE1 role in miRNA processing for personalized therapy.

Screening and application of inhibitory aptamers for DNA repair protein apurinic/apyrimidinic endonuclease 1

The base excision repair (BER) pathway is crucial for DNA repair, and apurinic/apyrimidinic endonuclease 1 (APE1) is a critical enzyme in this pathway. Overexpression of APE1 has been linked to multidrug resistance in various cancers, including lung cancer, colorectal cancer, and other malignant tumors. Therefore, reducing APE1 activity is desirable to improve cancer treatment. Inhibitory aptamers, which are versatile oligonucleotides for protein recognition and function restriction, are a promising tool for this purpose. In this study, we developed an inhibitory aptamer for APE1 using systematic evolution of ligands by exponential (SELEX) technology. We used carboxyl magnetic beads as the carrier and APE1 with a His-Tag as the positive screening target, while the His-Tag itself served as the negative screening target. The aptamer APT-D1 was selected based on its high binding affinity for APE1, with a dissociation constant (K_d) of 1.306 ± 0.1418 nM. Gel electrophoresis analysis showed that APT-D1 at a concentration of 1.6 μM could entirely inhibit APE1 with 21 nM. Our results suggest that these aptamers can be utilized for early cancer diagnosis and the treatment, and as an essential tool for studying the function of APE1.

The multifunctional APE1 DNA repair-redox signaling protein as a drug target in human disease

Apurinic/apyrimidinic (AP) endonuclease-reduction/oxidation factor 1 (APE1/Ref-1, also called APE1) is a multifunctional enzyme with crucial roles in DNA repair and reduction/oxidation (redox) signaling. APE1 was originally described as an endonuclease in the Base Excision Repair (BER) pathway. Further study revealed it to be a redox signaling hub regulating critical transcription factors (TFs). Although a significant amount of focus has been on the role of APE1 in cancer, recent findings support APE1 as a target in other indications, including ocular diseases [diabetic retinopathy (DR), diabetic macular edema (DME), and age-related macular degeneration (AMD)], inflammatory bowel disease (IBD) and others, where APE1 regulation of crucial TFs impacts important pathways in these diseases. The central responsibilities of APE1 in DNA repair and redox signaling make it an attractive therapeutic target for cancer and other diseases.

The Biological Role of Apurinic/Apyrimidinic Endonuclease1/Redox Factor-1 as a Therapeutic Target for Vascular Inflammation and as a Serologic Biomarker

Endothelial dysfunction promotes vascular inflammation by inducing the production of reactive oxygen species and adhesion molecules. Vascular inflammation plays a key role in the pathogenesis of vascular diseases and atherosclerotic disorders. However, whether there is an endogenous system that can participate in circulating immune surveillance or managing a balance in homeostasis is unclear. Apurinic/apyrimidinic endonuclease 1/redox factor-1 (henceforth referred to as APE1/Ref-1) is a multifunctional protein that can be secreted from cells. It functions as an apurinic/apyrimidinic endonuclease in the DNA base repair pathway and modulates redox status and several types of transcriptional factors, in addition to its anti-inflammatory activity. Recently, it was reported that the secretion of APE1/Ref-1 into the extracellular medium of cultured cells or its presence in the plasma can act as a serological biomarker for certain disorders. In this review, we summarize the possible biological functions of APE1/Ref-1 according to its subcellular localization or its extracellular secretions, as therapeutic targets for vascular inflammation and as a serologic biomarker.