The endonuclease APE1 processes miR-92b formation, thereby regulating expression of the tumor suppressor LDLR in cervical cancer cells

Promising predictive molecular biomarkers for cervical cancer (Review)

Cervical cancer (CC) constitutes a serious public health problem. Vaccination and screening programs have notably reduced the incidence of CC worldwide by >80%; however, the mortality rate in low‑income countries remains high. The staging of CC is a determining factor in therapeutic strategies: The clinical management of early stages of CC includes surgery and/or radiotherapy, whereas radiotherapy and/or concurrent chemotherapy are the recommended therapeutic strategies for locally advanced CC. The histopathological characteristics of tumors can effectively serve as prognostic markers of radiotherapy response; however, the efficacy rate of radiotherapy may significantly differ among cancer patients. Failure of radiotherapy is commonly associated with a higher risk of recurrence, persistence and metastasis; therefore, radioresistance remains the most important and unresolved clinical problem. This condition highlights the importance of precision medicine in searching for possible predictive biomarkers to timely identify patients at risk of treatment response failure and provide tailored therapeutic strategies according to genetic and epigenetic characteristics. The present review aimed to summarize the evidence that supports the role of several proteins, methylation markers and non‑coding RNAs as potential predictive biomarkers for CC.

Linking Late Endosomal Cholesterol with Cancer Progression and Anticancer Drug Resistance

Cancer cells undergo drastic metabolic adaptions to cover increased bioenergetic needs, contributing to resistance to therapies. This includes a higher demand for cholesterol, which often coincides with elevated cholesterol uptake from low-density lipoproteins (LDL) and overexpression of the LDL receptor in many cancers. This implies the need for cancer cells to accommodate an increased delivery of LDL along the endocytic pathway to late endosomes/lysosomes (LE/Lys), providing a rapid and effective distribution of LDL-derived cholesterol from LE/Lys to other organelles for cholesterol to foster cancer growth and spread. LDL-cholesterol exported from LE/Lys is facilitated by Niemann–Pick Type C1/2 (NPC1/2) proteins, members of the steroidogenic acute regulatory-related lipid transfer domain (StARD) and oxysterol-binding protein (OSBP) families. In addition, lysosomal membrane proteins, small Rab GTPases as well as scaffolding proteins, including annexin A6 (AnxA6), contribute to regulating cholesterol egress from LE/Lys. Here, we summarize current knowledge that links upregulated activity and expression of cholesterol transporters and related proteins in LE/Lys with cancer growth, progression and treatment outcomes. Several mechanisms on how cellular distribution of LDL-derived cholesterol from LE/Lys influences cancer cell behavior are reviewed, some of those providing opportunities for treatment strategies to reduce cancer progression and anticancer drug resistance.

Expression levels and clinical values of miR-92b-3p in breast cancer

BACKGROUND

miR-92b is a carcinogenic miRNA that has great potential as a biomarker for disease prognosis, diagnosis, and treatment in the clinic. It is of great significance to analyse the relationship between miR-92b and the clinicopathological characteristics of cancer patients. This paper aimed to investigate the expression levels and clinical values of miR-92b-3p in breast cancer (BC).

METHODS

Altogether, 112 female BC patients who were treated in our hospital were included as a study group, and 108 healthy women who came to our hospital for physical examinations were included as a control group. miR-92b-3p expression in the serum of subjects in both groups was detected by fluorescence quantitative PCR (RT-PCR) to analyse the correlation of this miRNA with the patients' pathological features and prognoses. The diagnostic value of miR-92b-3p expression for BC was analysed by plotting a receiver operating characteristic (ROC) curve.

RESULTS

miR-92b-3p expression was remarkably higher in the study group (P < 0.05), and its area under the curve (AUC) for detecting BC was 0.88. The expression was correlated with the tumour size, degree of differentiation, TNM staging, and lymphatic metastasis (P < 0.05). miR-92b-3p was significantly positively correlated with the TNM staging (r = 0.40, P < 0.05), was significantly negatively correlated with the degree of differentiation of the breast cancer cells (r =  - 0.35, P < 0.05), and was significantly positively correlated with the expression of carbohydrate antigen 125 (CA125) (r = 0.39, P < 0.05). The overall survival rate (OSR) of the 99 patients who had follow-up was 73.74%. The survival status was remarkably better in the low expression group (P < 0.05). miR-92b-3p expression was remarkably higher in the death group (P < 0.05). The AUC of miR-92b-3p alone in the death and survival groups was 0.76.

CONCLUSION

miR-92b-3p expression obviously rises in the serum of BC patients and is closely related to the clinical staging, degree of differentiation, and CA125 in BC, so the detection of this miRNA is of great significance to the diagnosis and prognostic evaluation of BC. This miRNA can be used as a potential biomarker for the diagnosis and prognosis of the disease.

Gene expression profiling after LINC00472 overexpression in an NSCLC cell line

Lung cancer accounts for a large proportion of cancer-related deaths worldwide. Personalized therapeutic medicine based on the genetic characteristics of non-small cell lung cancer (NSCLC) is a promising field, and discovering clinically applicable biomarkers of NSCLC is required. LINC00472 is a long non-coding RNA and has been recently suggested to be a biomarker of NSCLC, but little is known of its mechanism in NSCLC. Thus, the current study was performed to document changes in gene expression after LINC00472 overexpression in NSCLC cells. As a result of cell viability and migration assay, LINC00472 downregulated cell survival, proliferation, and motility. Transcriptome sequencing analysis showed 3,782 genes expression were changed in LINC00472 overexpressing cells. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed most genes were associated with intracellular metabolism. The PPP1R12B, RGS5, RBM5, RBL2, LDLR and PTPRM genes were upregulated by LINC00472 overexpression and these genes functioned as tumor suppressors in several cancers. In contrast, SPSB1, PCNA, CD24, CDK5, CDC25A, and EIF4EBP1 were downregulated by LINC00472, and they functioned as oncogenes in various cancers. Consequently, the function of LINC00472 in tumorigenesis might be related to changes in the expressions of other oncogenes and tumor suppressors.

PAICS is related to glioma grade and can promote glioma growth and migration

Glioma is a common malignant tumour of the brain. In this study, we aimed to investigate diagnostic biomarkers and its role in glioma. Weighted gene co-expression network analysis (WGCNA) and Cytoscape software were used to screen the marker genes in glioma. RT-qPCR and Western blotting methods were performed to determine the expression of PAICS, ERCC1 and XPA genes in glioma tissues. Expression level of PAICS in different grades of glioma was examined by immunohistochemistry. CCK8 and Colony formation assays were used to detect cell proliferation. Cell adhesion assay was used to detect adhesion ability. Wound healing and transwell tests were used to detect cell migration ability. Flow cytometry was used to detect cell cycle and apoptosis. According to the predicted co-expression network, we identified the hub gene PAICS. Furthermore, we observed that PAICS expression level was up-regulated in glioma tissues compared with normal tissues, and the expression level was correlated with the grade of glioma. Moreover, we found PAICS can promote glioma cells proliferation and migration in vitro. Flow cytometry results showed that si-PAICS cells were stalled at the G1 phase compared with the si-NC cells and knocking down PAICS expression can increase apoptotic rate. PAICS can regulate the mRNA and protein levels of nucleotide excision repair pathway core genes ERCC1 and XPA. l-aspartic acid can affect the expression of PAICS and then inhibit glioma cell proliferation. Our results indicated that PAICS can promote glioma proliferation and migration. PAICS may act as a potential diagnostic marker and a therapeutic target for glioma.

Coping with RNA damage with a focus on APE1, a BER enzyme at the crossroad between DNA damage repair and RNA processing/decay

Interest in RNA damage as a novel threat associated with several human pathologies is rapidly increasing. Knowledge on damaged RNA recognition, repair, processing and decay is still scanty. Interestingly, in the last few years, more and more evidence put a bridge between DNA damage repair enzymes and the RNA world. The Apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1) was firstly identified as a crucial enzyme of the base excision repair (BER) pathway preserving genome stability toward non-distorting DNA lesion-induced damages. Later, an unsuspected role of APE1 in controlling gene expression was discovered and its pivotal involvement in several human pathologies, ranging from tumor progression to neurodegenerative diseases, has emerged. Recent novel findings indicate a role of APE1 in RNA metabolism, particularly in processing activities of damaged (abasic and oxidized) RNA and in the regulation of oncogenic microRNAs (miRNAs). Even though the role of miRNAs in human pathologies is well-known, the mechanisms underlying their quality control are still totally unexplored. A detailed knowledge of damaged RNA decay processes in human cells is crucial in order to understand the molecular processes involved in multiple pathologies. This cutting-edge perspective article will highlight these emerging aspects of damaged RNA processing and decay, focusing the attention on the involvement of APE1 in RNA world.

LDLR inhibition promotes hepatocellular carcinoma proliferation and metastasis by elevating intracellular cholesterol synthesis through the MEK/ERK signaling pathway

Objective

Adaptive rewiring of cancer energy metabolism has received increasing attention. By binding with LDLs, LDLRs make most of the circulating cholesterol available for cells to utilize. However, it remains unclear how LDLR works in HCC development by affecting cholesterol metabolism.

Methods

Database analyses and immunohistochemical staining were used to identify the clinical significance of LDLR in HCC. A transcriptome analysis was used to reveal the mechanism of LDLR aberration in HCC progression. A liver orthotopic transplantation model was used to evaluate the role of LDLR in HCC progression in vivo.

Results

Downregulation of LDLR was identified as a negative prognostic factor in human HCC. Reduced expression of LDLR in HCC cell lines impaired LDL uptake but promoted proliferation and metastasis in vitro and in vivo. Mechanistically, increasing intracellular de novo cholesterol biosynthesis was the chief contributor to malignant behaviors caused by LDLR inhibition, which could be rescued by simvastatin. Activation of the MEK/ERK pathway by LDLR downregulation partially contributed to intracellular cholesterol synthesis in HCC.

Conclusions

Downregulation of LDLR may elevate intracellular cholesterol synthesis to accelerate proliferation and motility through a mechanism partially attributed to stimulation of the MEK/ERK signaling pathway. Repression of intracellular cholesterol synthesis with statins may constitute a targetable liability in the context of lower LDLR expression in HCC.

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Downregulation of LDLR is identified as a negative prognostic factor in human HCC.

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LDLR inhibition facilitates the proliferation and metastasis of HCC cells.

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Increased cholesterol synthesis chiefly contributes to the malignant behaviors caused by LDLR reduction.

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Blockade of cholesterol synthesis by simvastatin attenuates HCC progression under lower LDLR.

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Activation of the MEK/ERK pathway by LDLR downregulation promotes cholesterol synthesis in HCC.

APE1/Ref-1 - One Target with Multiple Indications: Emerging Aspects and New Directions

In the realm of DNA repair, base excision repair (BER) protein, APE1/Ref-1 (Apurinic/Apyrimidinic Endonuclease 1/Redox Effector - 1, also called APE1) has been studied for decades. However, over the past decade, APE1 has been established as a key player in reduction-oxidation (redox) signaling. In the review by Caston et al. (The multifunctional APE1 DNA repair-redox signaling protein as a drug target in human disease), multiple roles of APE1 in cancer and other diseases are summarized. In this Review, we aim to expand on the contributions of APE1 to various diseases and its effect on disease progression. In the scope of cancer, more recent roles for APE1 have been identified in cancer cell metabolism, as well as chemotherapy-induced peripheral neuropathy (CIPN) and inflammation. Outside of cancer, APE1 signaling may be a critical factor in inflammatory bowel disease (IBD) and is also an emergent area of investigation in retinal ocular diseases. The ability of APE1 to regulate multiple transcription factors (TFs) and therefore multiple pathways that have implications outside of cancer, makes it a particularly unique and enticing target. We discuss APE1 redox inhibitors as a means of studying and potentially combating these diseases. Lastly, we examine the role of APE1 in RNA metabolism. Overall, this article builds on our previous review to elaborate on the roles and conceivable regulation of important pathways by APE1 in multiple diseases.

Activity of Human Apurinic/Apyrimidinic Endonuclease APE1 Toward Damaged DNA and Native RNA With Non-canonical Structures

The primary role of apurinic/apyrimidinic (AP) endonuclease APE1 in human cells is the cleavage of the sugar phosphate backbone 5' to an AP site in DNA to produce a single-strand break with a 5'-deoxyribose phosphate and 3'-hydroxyl end groups. APE1 can also recognize and incise some damaged or modified nucleotides and possesses some minor activities: 3'-5' exonuclease, 3'-phosphodiesterase, 3'-phosphatase, and RNase H. A molecular explanation for the discrimination of structurally different substrates by the single active site of the enzyme remains elusive. Here, we report a mechanism of target nucleotide recognition by APE1 as revealed by the results of an analysis of the APE1 process involving damaged DNA and native RNA substrates with non-canonical structures. The mechanism responsible for substrate specificity proved to be directly related to the ability of a target nucleotide to get into the active site of APE1 in response to an enzyme-induced DNA distortion.

APE1 inhibits foam cell formation from macrophages via LOX1 suppression

BACKGROUND

Macrophage activation and massive foam cell formation are key events in the development of Atherosclerosis (AS). Apurinic apyrimidinic endonuclease 1/Redox factor-1 (APE1) is an enzyme responsible for DNA repair and redox regulation. Recent studies indicate that APE1 is also involved in inflammatory response. We sought to explore its effect on oxidized low-density lipoprotein (oxLDL) induced macrophage activation and foam cell formation.

METHODS

Human macrophage cell line THP-1 cells were cultured and treated with oxLDL. The mRNA and protein levels of inflammatory markers for macrophage activation were measured. Foam cell formation was detected by Oil red O staining. Meanwhile the major cellular receptors responsible for oxLDL uptake and efflux were detected. Chromatin immunoprecipitation-quantitative real time PCR (ChIP-qPCR) and dual luciferase reporter assays were performed to identify the molecular mechanisms through which APE1 affects macrophage activation and foam cell formation.

RESULTS

Aberrant APE1 expression dramatically decreases the mRNA and protein of oxLDL-induced inflammatory molecules in THP-1 cells, accompanied by significantly inhibited foam cell formation. Western blot assay showed that down-regulation of LOX1, a receptor of oxLDL, is responsible for the inhibitory effect of APE1 on oxLDL induced macrophage inflammation. ChIP-qPCR assay showed that APE1 inhibits binding of the LOX1 promoter to its transcription factor Oct1, leading to suppression of LOX1.

CONCLUSION

Our data confirm the anti-inflammatory properties of APE1 and for the first-time report that APE1 suppresses foam cell formation from macrophages via the oxLDL receptor LOX1. This finding indicates that APE1 can be a therapeutic target for AS prevention.

MiR-92b-3p inhibits proliferation and migration of C2C12 cells

Skeletal muscle, a critical component of the mammalian body, is essential for normal body movement. miRNAs are well documented in gene post-transcription regulation in many biological processes, including muscle development and maintenance. miR-92b-3p, which is often associated with tumorigenesis, has never been explored in myoblast development. Here, we used murine-derived C2C12 myoblasts to explore the potential functions of miR-92b-3p in skeletal muscle development. Our results demonstrated that miR-92b-3p mimics inhibited C2C12 cell proliferation and migration, whereas miR-92b-3p inhibitor promoted C2C12 cell proliferation and migration. C2C12 cell differentiation was not affected by miR-92b-3p mimics, according to immunofluorescence and qPCR results. Serum- and glucocorticoid-induced kinase 3 (SGK3) was predicted and validated as a target of miR-92b-3p. Overexpression of SGK3 promoted C2C12 cell proliferation. SGK3 and miR-92b-3p formed a regulatory pathway to modulate C2C12 cell proliferation. In conclusion, miR-92b-3p inhibited C2C12 cell proliferation by targeting SGK3 and impeded C2C12 cell migration.

USP16 Regulates the Stability and Function of LDL receptor by Deubiquitination

Low-density lipoprotein (LDL) particles are known to be atherogenic agents in coronary artery diseases. They adjust to other electronegative forms and can be the subject for the enhancement of inflammatory events in vessel subendothelial spaces. The LDL uptake is related to the membrane scavenger receptors, including LDL receptor (LDLR). The LDLR expression is closely associated with LDL uptake and occurrence of diseases, such as atherosclerotic cardiovascular diseases. Our findings identified USP16 as a novel regulator of LDLR due to its ability to prevent ubiquitylation-dependent LDLR degradation, further promoting the uptake of LDL. The enhancement of USP16-mediated deubiquitination andthe suppressive degradation of the LDLR cause the presentation of a potential strategy to increase LDL cholesterol clearance.

APE1 promotes proliferation and migration of cutaneous squamous cell carcinoma

BACKGROUND

Human Apurinic/Apyrimidinic Endonuclease 1 (APE1/REF-1/HAP1) is a multifunction protein involved in the progression of cancer. But the role of APE1 in cutaneous squamous cell carcinoma (cSCC) is unclear.

OBJECTIVE

This study is aimed to investigate the basic modulatory mechanism of APE1 in cSCC development and offer a novel potential target for clinical treatment.

METHODS

The expression of APE1 in cSCC tissues was detected by western blot and immunohistochemistry (IHC) staining. The function of APE1 and miR-27a in cSCC cells was investigated by cell counting kit-8 (CCK-8) assays, colony formation assays and transwell migration assays. Western blot was used to determine the expression of APE1 in cSCC and epithelial-mesenchymal transition (EMT) markers in HSC-1 and HSC-5 cells with APE1 knockdown or overexpression. Double luciferase reporter assays were performed to confirm the interaction of miR-27a and APE1.

RESULTS

We identified that APE1 was significantly upregulated in human cSCC tissues and cSCC cells and its overexpression promoted cell proliferation, migration and the expression of EMT markers in cSCC cells. Mechanistically, miR-27a was predicted and confirmed as the upstream of APE1. Its downregulation also enhanced the proliferation and migration of cSCC cells. Rescue experiments demonstrated that restoration of APE1 expression significantly abolished the inhibition of cell proliferation and migration mediated by miR-27a.

CONCLUSION

As a direct gene of miR-27a, APE1 improved cell proliferation and migration to promote the progression of cSCC, which could be considered as a potential therapeutic target for cSCC treatment.

A randomized, double-blind, placebo-controlled study of B-cell lymphoma 2 homology 3 mimetic gossypol combined with docetaxel and cisplatin for advanced non-small cell lung cancer with high expression of apurinic/apyrimidinic endonuclease 1

Background Overexpression of apurinic/apyrimidinic endonuclease 1 (APE1) is an important cause of poor chemotherapeutic efficacy in advanced non-small cell lung cancer (NSCLC) patients. Gossypol, a new inhibitor of APE1, in combination with docetaxel and cisplatin is believed to improve the efficacy of chemotherapy for advanced NSCLC with high APE1 expression. Methods Sixty-two patients were randomly assigned to two groups. Thirty-one patients in the experimental group received 75 mg/m² docetaxel and 75 mg/m² cisplatin on day 1 with gossypol administered at 20 mg once daily on days 1 to 14 every 21 days. The control group received placebo with the same docetaxel and cisplatin regimen. The primary endpoint was progression-free survival (PFS); secondary endpoints included overall survival (OS), response rate, and toxicity. Results There were no significant differences in PFS and OS between the experimental group and the control group. The median PFS (mPFS) in the experimental and control groups was 7.43 and 4.9 months, respectively (HR = 0.54; p = 0.06), and the median OS (mOS) was 18.37 and 14.7 months, respectively (HR = 0.68; p = 0.27). No significant differences in response rate and serious adverse events were found between the groups. Conclusion The experimental group had a better mPFS and mOS than did the control group, though no significant difference was observed. Because the regimen of gossypol combined with docetaxel and cisplatin was well tolerated, future studies with larger sample sizes should be performed.

Deoxycholic acid modulates the progression of gallbladder cancer through N6-methyladenosine-dependent microRNA maturation

Bile acids (BAs), well-defined signaling molecules with diverse metabolic functions, play important roles in cellular processes associated with many cancers. As one of the most common BAs, deoxycholic acid (DCA) is originally synthesized in the liver, stored in the gallbladder, and processed in the gut. DCA plays crucial roles in various tumors; however, functions and molecular mechanisms of DCA in gallbladder cancer (GBC) still remain poorly characterized. Here, we analyzed human GBC samples and found that DCA was significantly downregulated in GBC, and reduced levels of DCA was associated with poor clinical outcome in patients with GBC. DCA treatment impeded tumor progression by halting cell proliferation. DCA decreased miR-92b-3p expression in an m⁶A-dependent posttranscriptional modification manner by facilitating dissociation of METTL3 from METTL3–METTL14–WTAP complex, which increased the protein level of the phosphatase and tensin homolog, a newly identified target of miR-92b-3p, and subsequently inactivated the PI3K/AKT signaling pathway. Our findings revealed that DCA might function as a tumor suppressive factor in GBC at least by interfering with miR-92b-3p maturation, and suggested that DCA treatment could provide a new therapeutic strategy for GBC.

Recent advances in the contribution of noncoding RNAs to cisplatin resistance in cervical cancer

Cervical cancer (CC) remains a major disease burden on the female population worldwide. Chemotherapy with cisplatin (cis-diamminedichloroplatinum (II); CDDP) and related drugs are the main treatment option for CC; however, their efficacy is limited by the development of drug resistance. Noncoding RNAs (ncRNAs) have been found to play critical roles in numerous physiological and pathological cellular processes, including drug resistance of cancer cells. In this review, we describe some of the ncRNAs, including miRNAs, lncRNAs and circRNAs, that are involved in the sensitivity/resistance of CC to CDDP-based chemotherapy and discuss their mechanisms of action. We also describe some ncRNAs that could be therapeutic targets to improve the sensitivity of CC to CDDP-based chemotherapy.