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

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.

Enhancing APE1 detection through apurinic/apyrimidinic site inhibition of DNA polymerase: an innovative, highly sensitive approach

This study presents an innovative method for the highly sensitive detection of apurinic/apyrimidinic endonuclease 1 (APE1), a crucial biomarker and target for cancer diagnosis and treatment. The method is predicated on our discovery that the apurinic or apyrimidinic site (AP site) can inhibit the activity of Taq DNA polymerase. Subsequent experiments further led to the development of a new amplification method based on the digestion activity of Lambda exonuclease. This approach showed potential to detect trace amounts of APE1 in biological samples with high sensitivity.

Multiply Guaranteed Catalytic DNA Circuit for Cancer-Cell-Selective Imaging of miRNA and Robust Evaluation of Drug Resistance

Catalytic DNA circuits are desirable for sensitive bioimaging in living cells; yet, it remains a challenge to monitor these intricate signal communications because of the uncontrolled circuitry leakage and insufficient cell selectivity. Herein, a simple yet powerful DNA-repairing enzyme (APE1) activation strategy is introduced to achieve the site-specific exposure of a catalytic DNA circuit for realizing the selectively amplified imaging of intracellular microRNA and robust evaluation of the APE1-involved drug resistance. Specifically, the circuitry reactants are firmly blocked by the enzyme recognition/cleavage site to prevent undesirable off-site circuitry leakage. The caged DNA circuit has no target-sensing activity until its circuitry components are activated via the enzyme-mediated structural reconstitution and finally transduces the amplified fluorescence signal within the miRNA stimulation. The designed DNA circuit demonstrates an enhanced signal-to-background ratio of miRNA assay as compared with the conventional DNA circuit and enables the cancer-cell-selective imaging of miRNA. In addition, it shows robust sensing performance in visualizing the APE1-mediated chemoresistance in living cells, which is anticipated to achieve in-depth clinical diagnosis and chemotherapy research.

Investigation of APE1 and OGG1 expression in chronic hemodialysis patients

BACKGROUND

The role of DNA repair mechanisms is of significant importance in diseases characterized by elevated oxidative DNA damage, such as chronic kidney disease. It is imperative to thoroughly understand the functions of molecules associated with DNA repair mechanisms, not only for assessing susceptibility to diseases but also for monitoring disease progression. In this research, we investigated the APE1 and OGG1 gene expression levels, both of which are involved in the base excision repair (BER) mechanism in chronic hemodialysis patients with malignancy (HPM; n = 8) and without malignancy (HP; n = 36) in pre- and post-dialysis period and 37 healty persons. We also assessed how these values correlate with the clinical profiles of the patients.

METHODS AND RESULTS

We conducted gene expression analysis using real-time polymerase chain reaction (qRT-PCR). No significant differences in APE1 gene expression levels were observed in pre-dialysis when comparing the HP and HPM groups to the control group. The expression levels of the OGG1 gene were significantly lower in both the HP and HPM groups in pre- and post-dialysis periods compared to the control group. Dialysis procedures led to a reduction in APE1 and OGG1 gene expression levels in both HP and HPM groups.

CONCLUSIONS

The findings of our study elucidate the impact of alterations in the base excision repair (BER) mechanism, including the hemodialysis process, in end-stage renal disease (ESRD).

The APE1/REF-1 and the hallmarks of cancer

APE1/REF-1 (apurinic/apyrimidinic endonuclease 1 / redox factor-1) is a protein with two domains, with endonuclease function and redox activity. Its main activity described is acting in DNA repair by base excision repair (BER) pathway, which restores DNA damage caused by oxidation, alkylation, and single-strand breaks. In contrast, the APE1 redox domain is responsible for regulating transcription factors, such as AP-1 (activating protein-1), NF-κB (Nuclear Factor kappa B), HIF-1α (Hypoxia-inducible factor 1-alpha), and STAT3 (Signal Transducers and Activators of Transcription 3). These factors are involved in physiological cellular processes, such as cell growth, inflammation, and angiogenesis, as well as in cancer. In human malignant tumors, APE1 overexpression is associated with lung, colon, ovaries, prostate, and breast cancer progression, more aggressive tumor phenotypes, and worse prognosis. In this review, we explore APE1 and its domain's role in cancer development processes, highlighting the role of APE1 in the hallmarks of cancer. We reviewed original articles and reviews from Pubmed related to APE1 and cancer and found that both domains of APE1/REF-1, but mainly its redox activity, are essential to cancer cells. This protein is often overexpressed in cancer, and its expression and activity are correlated to processes such as proliferation, invasion, inflammation, angiogenesis, and resistance to cell death. Therefore, APE1 participates in essential processes of cancer development. Then, the activity of APE1/REF-1 in these hallmarks suggests that targeting this protein could be a good therapeutic approach.