Gene Summary

Gene:APEX1; apurinic/apyrimidinic endodeoxyribonuclease 1
Summary:Apurinic/apyrimidinic (AP) sites occur frequently in DNA molecules by spontaneous hydrolysis, by DNA damaging agents or by DNA glycosylases that remove specific abnormal bases. AP sites are pre-mutagenic lesions that can prevent normal DNA replication so the cell contains systems to identify and repair such sites. Class II AP endonucleases cleave the phosphodiester backbone 5' to the AP site. This gene encodes the major AP endonuclease in human cells. Splice variants have been found for this gene; all encode the same protein. [provided by RefSeq, Jul 2008]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:DNA-(apurinic or apyrimidinic site) lyase
Source:NCBIAccessed: 11 March, 2017


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • BCL2 protein
  • DNA Repair
  • Thymine DNA Glycosylase
  • Radiotherapy Dosage
  • Survival Rate
  • Stomach Cancer
  • Thyroid Cancer
  • Oligonucleotide Array Sequence Analysis
  • Sequence Deletion
  • siRNA
  • Tumor Suppressor Proteins
  • Risk Assessment
  • Young Adult
  • Surveys and Questionnaires
  • Messenger RNA
  • Polymorphism
  • Chromosome 14
  • Smoking
  • Taiwan
  • Single-Stranded Conformational Polymorphism
  • Xenograft Models
  • Reactive Nitrogen Species
  • Transcription Factors
  • Reactive Oxygen Species
  • Tissue Culture Techniques
  • Transfection
  • Stromal Cells
  • Sensitivity and Specificity
  • Oxidation-Reduction
  • Xeroderma Pigmentosum
  • APEX1
  • Cervical Cancer
  • p53 Protein
  • Single Nucleotide Polymorphism
  • Skin Cancer
  • Turkey
  • Lucanthone
  • Uracil-DNA Glycosidase
  • Radiation Tolerance
  • DNA-(Apurinic or Apyrimidinic Site) Lyase
Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: APEX1 (cancer-related)

Wen X, Lu R, Xie S, et al.
APE1 overexpression promotes the progression of ovarian cancer and serves as a potential therapeutic target.
Cancer Biomark. 2016; 17(3):313-322 [PubMed] Related Publications
BACKGROUND: Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional enzyme that is involved in DNA repair and the redox regulation of transcription factors. Blocking these functions leads to cell-growth inhibition, apoptosis and other effects. Previous studies have demonstrated that high expression levels of the APE1 protein are associated with the progression and chemoresistance of cancers. We hypothesized that APE1 silencing in ovarian cancer cells might have anticancer effects mediated by cell-growth inhibition and an increase in drug-sensitivity.
OBJECTIVE: In this study, we explored the consequences of APE1 silencing in ovarian cancer cells.
METHODS: Immunohistochemistry (IHC) was used to detect the APE1 protein levels in tissue samples from twelve ovarian cancer (OC) patients and eleven non-OC patients. APE1 knockdown was achieved via the stable transfection of SKOV3 and A2780 cells with a construct encoding a short hairpin DNA directed against the APE1 gene. Then, cell proliferation, colony formation, cell cycle and apoptosis assays were performed to reveal the consequences of APE1 silencing in ovarian cancer cells. Additionally, the SKOV3 and A2780 cells were subjected to the treatment with camptothecin (CPT) and ultraviolet rays (UV) to assess the possible link between the APE1 protein and drug-resistance.
RESULTS: Our results revealed that the APE1 protein was overexpressed in OC tissues. APE1 knockdown in A2780 and SKOV3 cells reduced cell proliferation, arrested cell cycle progression, repressed colony formation and weakly promoted cell apoptosis through the BAX and BCL-2 apoptotic pathways. Additionally, the down-regulation of APE1 significantly enhanced the sensitivity of ovarian cancer cells to the CPT/UV treatment.
CONCLUSION: Our study suggested that the APE1 protein is important for the proliferation and growth of ovarian cancer cells. APE1 silencing might enhance drug-sensitivity, and thus APE1 might serve as a novel anti-OC therapeutic target.

Costa EF, Santos ES, Liutti VT, et al.
Association between polymorphisms in genes related to DNA base-excision repair with risk and prognosis of oropharyngeal squamous cell carcinoma.
J Cancer Res Clin Oncol. 2016; 142(9):1917-26 [PubMed] Related Publications
PURPOSE: We examined the influence of OGG1 c.977C>G (rs1052133), APEX1 c.444T>G (rs1130409), XRCC1 c.-77T>C (rs3213245), c.580C>T (rs1799782), c.839G>A (rs25489) and c.1196G>A (rs25487) single-nucleotide polymorphisms (SNPs), involved in base-excision repair (BER) pathway, on oropharyngeal squamous cell carcinoma (OPSCC) risk and prognosis.
METHODS: Aiming to identify the genotypes, DNA from 200 consecutive OPSCC patients and 200 controls was analyzed by PCR-RFLP. The prognostic impact of genotypes of SNPs on progression-free survival (PFS) and overall survival of OPSCC patients was examined using the Kaplan-Meier estimates and Cox regression analyses.
RESULTS: XRCC1 c.580CT or TT genotypes (19.5 vs. 11.0 %, P = 0.04) and XRCC1 TTGG haplotype from c.-77T>C, c.580C>T, c.839G>A and c.1196G>A SNPs (17.5 vs. 10.0 %, P = 0.04) were more common in patients with OPSCC than in controls. Carriers of combined genotypes of c.580C>T and TTGG haplotype of XRCC1 gene were under 3.35- and 3.22-fold increased risk of OPSCC than others. For survival analysis, we selected only patients with tumor at stage IV. The median follow-up time was 24.5 months. At 24 months of follow-up, PFS was shorter in patients with OGG1 c.977CC genotype when compared with others genotypes (35.5 vs. 52.1 %, log-rank test, P = 0.03). After multivariate Cox analysis, patients with OGG1 c.977CC genotype had more chance to present tumor progression when compared with others (HR 1.68, P = 0.02).
CONCLUSIONS: Our data present, for the first time, evidence that inherited OGG1 c.977C>G; XRCC1 c.-77T>C, c.580C>T, c.839G>A and c.1196G>A abnormalities of DNA BER pathway are important determinants of OPSCC and predictors of patient outcomes.

Lai CY, Hsieh LL, Tang R, et al.
Association between polymorphisms of APE1 and OGG1 and risk of colorectal cancer in Taiwan.
World J Gastroenterol. 2016; 22(12):3372-80 [PubMed] Free Access to Full Article Related Publications
AIM: To evaluate the effects of OGG1 (Ser326Cys, 11657A/G, and Arg154His) and APE1 (Asp148Glu, and T-656G) polymorphisms on colorectal cancer (CRC) risk.
METHODS: We enrolled 727 cases newly diagnosed with colorectal adenocarcinoma and 736 age- and sex-matched healthy controls from a medical center in Taiwan. Genomic DNA isolated from the buffy coat was used for genotyping through polymerase chain reaction. Unconditional logistic regressions were used for calculating ORs and 95%CIs to determine the association between the genetic polymorphisms and CRC risk. Haplotype frequencies were estimated using PHASE software. Moreover, stratification analyses on the basis of sex, age at diagnosis, and tumor subsite and stage were performed.
RESULTS: The CRC risk was higher in patients with the OGG1 326Ser/Cys + Cys/Cys genotype (OR = 1.38, 95%CI: 1.03-1.85, P = 0.030), particularly high in patients with stage III + IV cancer (OR = 1.48, 95%CI: 1.03-2.13) compared with patients with the Ser/Ser genotype. In addition, OGG1 11657G allele carriers had a 41% reduced CRC risk among stage 0-II patients (OR = 0.59, 95%CI: 0.35-0.98). The CRC risk was significantly higher among females with the APE1 Glu allele (OR = 1.41, 95%CI: 1.02-1.96). The APE1 148Glu/-656G haplotype was also associated with a significant CRC risk in females (OR = 1.36, 95%CI: 1.03-1.78).
CONCLUSION: OGG1 and APE1 polymorphisms are associated with stage- and sex-specific risk of CRC in the Taiwanese population.

Gordillo GM, Biswas A, Khanna S, et al.
Multidrug Resistance-associated Protein-1 (MRP-1)-dependent Glutathione Disulfide (GSSG) Efflux as a Critical Survival Factor for Oxidant-enriched Tumorigenic Endothelial Cells.
J Biol Chem. 2016; 291(19):10089-103 [PubMed] Article available free on PMC after 06/05/2017 Related Publications
Endothelial cell tumors are the most common soft tissue tumors in infants. Tumor-forming endothelial (EOMA) cells are able to escape cell death fate despite excessive nuclear oxidant burden. Our previous work recognized perinuclear Nox-4 as a key contributor to EOMA growth. The objective of this work was to characterize the mechanisms by which EOMA cells evade oxidant toxicity and thrive. In EOMA cells, compared with in the cytosol, the nuclear GSSG/GSH ratio was 5-fold higher. Compared to the ratio observed in healthy murine aortic endothelial (MAE) cells, GSSG/GSH was over twice as high in EOMA cells. Multidrug resistance-associated protein-1 (MRP-1), an active GSSG efflux mechanism, showed 2-fold increased activity in EOMA compared with MAE cells. Hyperactive YB-1 and Ape/Ref-1 were responsible for high MRP-1 expression in EOMA. Proximity ligand assay demonstrated MRP-1 and YB-1 binding. Such binding enabled the nuclear targeting of MRP-1 in EOMA in a leptomycin-B-sensitive manner. MRP-1 inhibition as well as knockdown trapped nuclear GSSG, causing cell death of EOMA. Disulfide loading of cells by inhibition of GSSG reductase (bischoloronitrosourea) or thioredoxin reductase (auranofin) was effective in causing EOMA death as well. In sum, EOMA cells survive a heavy oxidant burden by rapid efflux of GSSG, which is lethal if trapped within the cell. A hyperactive MRP-1 system for GSSG efflux acts as a critical survival factor for these cells, making it a potential target for EOMA therapeutics.

de Melo JT, de Souza Timoteo AR, Lajus TB, et al.
XPC deficiency is related to APE1 and OGG1 expression and function.
Mutat Res. 2016 Feb-Mar; 784-785:25-33 [PubMed] Related Publications
Oxidative DNA damage is considered to be a major cause of neurodegeneration and internal tumors observed in syndromes that result from nucleotide excision repair (NER) deficiencies, such as Xeroderma Pigmentosum (XP) and Cockayne Syndrome (CS). Recent evidence has shown that NER aids in removing oxidized DNA damage and may interact with base excision repair (BER) enzymes. Here, we investigated APE1 and OGG1 expression, localization and activity after oxidative stress in XPC-deficient cells. The endogenous APE1 and OGG1 mRNA levels were lower in XPC-deficient fibroblasts. However, XPC-deficient cells did not show hypersensitivity to oxidative stress compared with NER-proficient cells. To confirm the impact of an XPC deficiency in regulating APE1 and OGG1 expression and activity, we established an XPC-complemented cell line. Although the XPC complementation was only partial and transient, the transfected cells exhibited greater OGG1 expression and activity compared with XPC-deficient cells. However, the APE1 expression and activity did not significantly change. Furthermore, we observed a physical interaction between the XPC and APE1 proteins. Together, the results indicate that the responses of XPC-deficient cells under oxidative stress may not only be associated with NER deficiency per se but may also include new XPC functions in regulating BER proteins.

Montaldi AP, Godoy PR, Sakamoto-Hojo ET
APE1/REF-1 down-regulation enhances the cytotoxic effects of temozolomide in a resistant glioblastoma cell line.
Mutat Res Genet Toxicol Environ Mutagen. 2015; 793:19-29 [PubMed] Related Publications
Temozolomide (TMZ) is widely used for patients with glioblastoma (GBM); however, tumor cells frequently exhibit drug-resistance. Base excision repair (BER) has been identified as a possible mediator of TMZ resistance, and an attractive approach to sensitizing cells to chemotherapy. Human apurinic/apyrimidinic endonuclease/redox factor-1 (APE1) is an essential enzyme with a role in the BER pathway by repairing abasic sites, and it also acts as a reduction factor, maintaining transcription factors in an active reduced state. Thus, we aimed to investigate whether the down-regulation of APE1 expression by siRNA can interfere with the resistance of GBM to TMZ, being evaluated by several cellular and molecular parameters. We demonstrated that APE1 knockdown associated with TMZ treatment efficiently reduced cell proliferation and clonogenic survival of resistant cells (T98G), which appears to be a consequence of increased DNA damage, S-phase arrest, and H2AX phosphorylation, resulting in apoptosis induction. On the contrary, for those assays, the sensitization effects of APE1 silencing plus TMZ treatment did not occur in the TMZ-sensitive cell line (U87MG). Interestingly, TMZ-treatment and APE1 knockdown significantly reduced cell invasion in both cell lines, but TMZ alone did not reduce the invasion capacity of U87MG cells, as observed for T98G. We also found that VEGF expression was down-regulated by TMZ treatment in T98G cells, regardless of APE1 knockdown, but U87MG showed a different response, since APE1 silencing counteracted VEGF induction promoted by TMZ, suggesting that the APE1-redox function may play an indirect role, depending on the cell line. The present results support the contribution of BER in the GBM resistance to TMZ, with a greater effect in TMZ-resistant, compared with TMZ-sensitive cells, emphasizing that APE1 can be a promising target for modifying TMZ tolerance. Furthermore, genetic characteristics of tumor cells should be considered as critical information to select an appropriate therapeutic strategy.

Antoniali G, Marcuzzi F, Casarano E, Tell G
Cadmium treatment suppresses DNA polymerase δ catalytic subunit gene expression by acting on the p53 and Sp1 regulatory axis.
DNA Repair (Amst). 2015; 35:90-105 [PubMed] Related Publications
Cadmium (Cd) is a carcinogenic and neurotoxic environmental pollutant. Among the proposed mechanisms for Cd toxic effects, its ability to promote oxidative stress and to inhibit, in vitro, the activities of some Base Excision DNA Repair (BER) enzymes, such as hOGG1, XRCC1 and APE1, have been already established. However, the molecular mechanisms at the basis of these processes are largely unknown especially at sub-lethal doses of Cd and no information is available on the effect of Cd on the expression levels of BER enzymes. Here, we show that non-toxic treatment of neuronal cell lines, with pro-mitogenic doses of Cd, promotes a significant time- and dose-dependent down-regulation of DNA polymerase δ (POLD1) expression through a transcriptional mechanism with a modest effect on Polβ, XRCC1 and APE1. We further elucidated that the observed transcriptional repression on Polδ is acted by through competition by activated p53 on Sp1 at POLD1 promoter and by a squelching effect. We further proved the positive effect of Sp1 not only on POLD1 expression but also on Polβ, XRCC1 and APE1 expression, suggesting that Sp1 has pleiotropic effects on the whole BER pathway. Our results indicated that Cd-mediated impairment of BER pathway, besides acting on the enzymatic functions of some key proteins, is also exerted at the gene expression level of Polδ by acting on the p53-Sp1 regulatory axis. These data may explain not only the Cd-induced neurotoxic effects but also the potential carcinogenicity of this heavy metal.

Yager JW, Erdei E, Myers O, et al.
Arsenic and ultraviolet radiation exposure: melanoma in a New Mexico non-Hispanic white population.
Environ Geochem Health. 2016; 38(3):897-910 [PubMed] Related Publications
Cases of cutaneous melanoma and controls were enrolled in a New Mexico population-based study; subjects were administered questionnaires concerning ultraviolet (UV) and inorganic arsenic (iAs) exposure. Historical iAs exposure was estimated. UV exposure estimates were also derived using geospatial methods. Drinking water samples were collected for iAs analysis. Blood samples were collected for DNA repair (Comet) and DNA repair gene polymorphism assays. Arsenic concentrations were determined in urine and toenail samples. UV exposures during the previous 90 days did not vary significantly between cases and controls. Mean (±SD) current home iAs drinking water was not significantly different for cases and controls [3.98 μg/L (±3.67) vs. 3.47 μg/L (±2.40)]. iAs exposure showed no effect on DNA repair or association with melanoma. Results did not corroborate a previously reported association between toenail As and melanoma risk. Arsenic biomarkers in urine and toenail were highly significantly correlated with iAs in drinking water. A UV-DNA repair interaction for UV exposure over the previous 7-90 days was shown; cases had higher DNA damage than controls at low UV values. This novel finding suggests that melanoma cases may be more sensitive to low-level UV exposure than are controls. A UV-APEX1 interaction was shown. Subjects with the homozygous rare APEX1 DNA repair gene allele had a higher risk of early melanoma diagnosis at low UV exposure compared with those with the homozygous wild type or the heterozygote. Notably, a UV-arsenic interaction on inhibition of DNA repair was not observed at iAs drinking water concentrations below 10 ppb (μg/L).

Elingarami S, Liu H, Kalinjuma AV, et al.
Polymorphisms in NEIL-2, APE-1, CYP2E1 and MDM2 Genes are Independent Predictors of Gastric Cancer Risk in a Northern Jiangsu Population (China).
J Nanosci Nanotechnol. 2015; 15(7):4815-28 [PubMed] Related Publications
China is one of the countries with the highest incidence of gastric cancer, and accounts for over 40% of all new gastric cancer cases in the world. Genetic factors as well as environmental factors play a role in development of gastric cancer. To investigate the independent roles of single nucleotide polymorphisms (SNPs) in base excision repair (BER) genes (APE1 and NEIL2), carcinogen metabolism gene (CYP2E1) and tumor suppressor pathway gene (MDM2) for gastric cancer susceptibility in a Chinese population, we conducted a hospital based case-control study to evaluate the potential association between these polymorphisms and susceptibility to gastric cancer in a Northern Jiangsu population. We also associated the NEIL-2 mRNA expression with the studied NEIL2 SNP genotypes to assess whether the genotypes have influence on the NEIL2 mRNA (hence protein) expression. Five SNPs, APE 1 (rs2275008), NEIL 2 (rs804270), MDM2 (rs2279744), and CYP 2E1 (rs2480256 and rs2031920), were genotyped by TaqMan assays in 105 gastric cancer cases and 118 controls. Genotype frequency distribution showed that the APE 1 SNP (rs2275008), NEIL 2 SNP (rs804270), MDM2 SNP (rs2279744), and CYP 2E1 SNP (rs2031920) had more mutant alleles in gastric cancer cases than controls (76.19, 68.57, 54.29, and 43.81%, respectively), while CYP 2E1 SNP (rs2480256) had large percentage of both alleles (43.81%). Risk analysis revealed that there was increased risk for gastric cancer in subjects with mutant alleles in APE 1 (rs2275008: OR 5.49, 95% CI = 2.6-5.7, p <.0001), NEIL 2 (rs804270: OR 2.3, 95% CI = 1.22-4.3, p=0.01), MDM2 (rs2279744: OR 14.65, 95% CI = 5.63-8.15, p < .0001), and CYP 2E1 (rs2031920: OR 8.385, 95% CI = 3.2-5.3, p < .0001) SNPs. Moreover, the NEIL2 mRNA expression analysis showed that there was significant differential expression of NEIL2 mRNA among the randomly tested NEIL2 genotypes (p = 0.005), with low expression seen in variant genotypes than in other genotypes. In conclusion, variant alleles in the NEIL2 (rs804270), APE1 (rs2275008), CYP2E1 (rs2031920) and MDM2 (rs2279744) SNPs may independently influence susceptibility to gastric cancer in a Northern Jiangsu Chinese population. The genotypes may also independently influence their respective gene mRNA expression, as seen in our study, where there was differential expression of the NEIL2 mRNA among the genotypes, with low NEIL2 mRNA expression seen in the variant genotype.

Mashayekhi F, Yousefi M, Salehi Z, et al.
The association of ApE1 -656T>G and 1349T>G polymorphisms with breast cancer susceptibility in northern Iran.
Cell Mol Biol (Noisy-le-grand). 2015; 61(4):70-4 [PubMed] Related Publications
Breast cancer is the most common cancer and one of the main causes of cancer-related death in the world and has become a major public health concern. Many genes have been shown to be involved in the progress of the breast cancer. Human apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional protein that has an important role in the base excision repair (BER) pathway. The aim of this study was to evaluate the association between ApE1 -656T>G and 1349T>G polymorphisms and the susceptibility to breast cancer in northern Iran population. Samples were obtained from 150 patients diagnosed with breast cancer and 150 control subjects and genotyped by tetra - primer amplification refractory mutation system PCR (T-ARMS-PCR). We observed a significant difference in genotype distributions of -656T>G polymorphism between patients and controls (P= 0.03). Findings indicated that individuals with the variant TG genotypes had a significant decreased risk of breast cancer (OR= 0.55, 95% CI= 0.33 - 0.91, P= 0.019). However, the significant association between 1349T>G polymorphism and breast cancer risk was not observed (P = 0.89). Larger studies are needed to confirm our results.

Li H, Zou J, Mi J, et al.
Association of APE1 Gene Asp148Glu Variant with Digestive Cancer: A Meta-Analysis.
Med Sci Monit. 2015; 21:2456-66 [PubMed] Article available free on PMC after 06/05/2017 Related Publications
BACKGROUND: Apurinic/apyrimidinic endonuclease-1 (APE1) is a rate-limiting enzyme in DNA base excision repair and has been implicated in carcinogenesis. In this study, we summarize available data to examine the susceptibility of APE1 gene Asp148Glu variant to digestive cancer via a meta-analysis.
MATERIAL AND METHODS: Study selection and data abstraction were conducted independently by 2 authors. Random-effects model was utilized to pool effect estimates. Heterogeneity and publication bias were addressed.
RESULTS: Sixteen articles involving 4916 digestive cancer patients and 7748 controls were qualified for this meta-analysis. Overall association showed an indicative association between Asp148Glu variant and digestive cancer under allelic (odds ratio or OR=1.11; 95% confidence interval or CI: 0.99-1.25; P=0.074) and dominant (OR=1.18; 95% CI: 1.00-1.40; P=0.056) models, with strong evidence of heterogeneity. Deviation from Hardy-Weinberg equilibrium was an obvious source of heterogeneity. In subgroup analyses by cancer sites, this variant was significantly associated with the increased risk for hepatocellular cancer under allelic (OR=1.50; 95% CI: 1.25-1.80; P<0.001) and homozygous genotypic (OR=1.55; 95% CI: 1.02-2.29; P=0.028) models. There were low probabilities of publication bias for the above comparisons.
CONCLUSIONS: The results of this meta-analysis collectively suggest that APE1 gene Asp148Glu variant is not a risk-conferring factor for digestive cancer. Further large and well-designed studies are required.

AlMutairi F, Pathan AA, Alanazi M, et al.
Association of DNA Repair Gene APE1 Asp148Glu Polymorphism with Breast Cancer Risk.
Dis Markers. 2015; 2015:869512 [PubMed] Article available free on PMC after 06/05/2017 Related Publications
OBJECTIVE: The aim of this study was to investigate the role of APE1 Asp148Glu polymorphism in breast cancer progression in Saudi population.
METHODS: We examined the genetic variations (rs1130409) in the DNA base excision repair gene APE1 at codon 148 (Asp148Glu) and its association with breast cancer risk using genotypic assays and in silico structural as well as functional predictions. In silico structural analysis was performed with Asp148Glu allele and compared with the predicted native protein structure. The wild and mutant 3D structures of APE1 were compared and analyzed using solvent accessibility models for protein stability confirmation.
RESULTS: Genotypic analysis of APE1 (rs1130409) showed statistically significant association of Asp148Glu with elevated susceptibility to breast cancer. The in silico analysis results indicated that the nsSNP Asp148Glu may cause changes in the protein structure and is associated with breast cancer risk.
CONCLUSION: Taken together, this is the first report that established that Asp148Glu variant has structural and functional effect on the APE1 and may play an important role in breast cancer progression in Saudi population.

Pournourali M, Tarang AR, Yousefi M
The association between 1349T>G polymorphism of ApE1 gene and the risk of prostate cancer in northern Iran.
Cell Mol Biol (Noisy-le-grand). 2015; 61(4):21-4 [PubMed] Related Publications
Prostate cancer (PCa) is the most common malignancy in men and the fourth most common cause of death based on cancer all over the world. Many genes has been shown to be involved in the progress of the prostate cancer. Human apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional protein that has an important role in the base excision repair (BER) pathway. The aim of this study was to evaluate the association of ApE1 1349T>G polymorphism and the susceptibility to prostate cancer in northern Iran population. Samples were collected from 100 patients diagnosed with prostate cancer patients and 100 controls subjects and genotyped by PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism). We observed a significant difference in genotype distributions of ApE1 1349T>G polymorphism between patients and controls (P= 0.039). Our findings revealed individuals with the variant TG and GG had a significant increased risk of prostate cancer (GG: OR= 2.50, 95%CI= 1.063-5.874, P= 0.035. TG: OR= 2.40, 95%CI= 1.16-4.95, P= 0.017). Also, more analyses were showed that G allele were associated with increased risk of prostate cancer (OR= 1.493, 95%CI= 1.007-2.21, P= 0.045). The data from this study indicates that the ApE1 1349T>G polymorphism is associated with increased risk of prostate cancer. Although more studies should be considered with larger number of patients and control subjects to confirm our results.

Chantre-Justino M, Alves G, Britto C, et al.
Impact of reduced levels of APE1 transcripts on the survival of patients with urothelial carcinoma of the bladder.
Oncol Rep. 2015; 34(4):1667-74 [PubMed] Article available free on PMC after 06/05/2017 Related Publications
Molecular evidence indicates that alterations in genes involved in the maintenance of genome stability may be related to susceptibility to bladder carcinoma. Our goal was to evaluate the prognostic role of base excision repair (BER) genes in a cohort of patients diagnosed with primary urothelial carcinoma of the bladder (UCB). The levels of all APE1, XRCC1 and POLB transcripts were detected by quantitative real-time PCR (qPCR) technique in tumor samples from 52 patients undergoing transurethral resection (TUR) for primary UCB at the Department of Urology, Brazilian National Cancer Institute, Rio de Janeiro. Increased levels of APE1, XRCC1 and POLB transcripts were significantly associated with high-grade tumors when compared to these levels in low-grade tumors (p<0.01) and could be attributed to different mechanisms of transcriptional regulation as a response to tumorigenesis and oxidative stress. By analyzing the collected data in the present study, regardless of pathological grade or stage, univariate analysis revealed that the reduced levels of APE1 transcripts were significantly associated with cancer-specific mortality (p=0.032). Furthermore, the variant genotype (TG/GG) of the APE1 T1349G polymorphism was observed in 75% of a subset of patients who concomitantly experienced reduced levels of the APE1 transcript and death and/or recurrence events. Taken together, our data reinforce the idea that human DNA repair mechanisms must be finely regulated in order to avoid instability leading to tumorigenesis and poor clinical outcomes in UCB patients.

Kabziński J, Majsterek I, Mik M, et al.
Impact of APEX Ile64val Gene Polymorphisms of DNA Repair Ber System on Modulation of the Risk of Colorectal Cancer in the Polish Population.
Pol Przegl Chir. 2015; 87(3):121-3 [PubMed] Related Publications
UNLABELLED: Colorectal cancer (CRC) is one of the deadliest cancers which lie in the incidence of morbidity in second place. Intensive research is to determine and confirm the genetic basis of this disease, which is believed may have a direct relationship with the reduced efficiency of DNA repair systems. The aim of this study was to determine the effect of APEX gene polymorphism Ile64Val on increasing the risk of colorectal cancer in the Polish population.
MATERIAL AND METHODS: The blood samples collected from 150 patients diagnosed with colon cancer was used. The control group consisted of 150 healthy subjects. Genotyping was performed by TaqMan method.
RESULTS: The results indicate that genotype Ile Val is associated with an increased risk of colorectal cancer (OR 2.069; 95% CI 1,205-3,552; p = 0.008).
CONCLUSIONS: Based on these results, we conclude that the APEX gene polymorphism Ile64Val may be associated with an increased risk of colorectal cancer.

Lee YR, Kim KM, Jeon BH, Choi S
Extracellularly secreted APE1/Ref-1 triggers apoptosis in triple-negative breast cancer cells via RAGE binding, which is mediated through acetylation.
Oncotarget. 2015; 6(27):23383-98 [PubMed] Article available free on PMC after 06/05/2017 Related Publications
The present study evaluated the mechanism of apoptosis caused by post-translational modification, hyperacetylation in triple-negative breast cancer (TNBC) cells. We previously showed that trichostatin A (TSA) induced secretion of acetylated apurinic apyrimidinic endonuclease 1/redox factor-1 (Ac-APE1/Ref-1). This is the first report showing that Ac-APE1/Ref-1 initiates apoptosis in TNBC cells by binding to the receptor for advanced glycation end products (RAGE). The functional significance of secreted Ac-APE1/Ref-1 was studied by induction of intracellular hyperacetylation through co-treatment with acetylsalicylic acid and TSA in MDA-MB-231 cells. In response to hyperacetylation, secretion of Ac-APE1/Ref-1 in vesicles was observed, resulting in significantly decreased cell viability and induction of apoptosis with increased expression of RAGE. The hyperacetylation-induced apoptosis was similar in two other TNBC cell lines: BT-459 and MDA-MB-468. Therefore, hyperacetylation may be a therapeutic target for treatment of TNBCs. This study introduces a novel paradigm whereby post-translational modification induces apoptotic cell death in breast cancer cells resistant to standard chemotherapeutic agents through secretion of auto- or paracrine molecules such as Ac-APE1/Ref-1.

Jiang S, Zhu L, Tang H, et al.
Ape1 regulates WNT/β-catenin signaling through its redox functional domain in pancreatic cancer cells.
Int J Oncol. 2015; 47(2):610-20 [PubMed] Related Publications
Apurinic/apyrimidinic endonuclease 1/redox factor-1 (Ape1/Ref-1, Ape1) is a multifunctional protein that is upregulated in human pancreatic cancer. Ape1 redox domain plays an essential role in regulating the effects of reactive oxygen species (ROS) generated during physiological metabolism and pathological stress. In the present study, we explored whether Ape1 and ROS affect WNT/β-catenin signaling. We used E3330, a small molecule inhibitor of the redox activity of Ape1, and a siRNA approach to knock down Ape1, in two human pancreatic cancer cell lines. Inhibition of Ape1 resulted in growth suppression of pancreatic cancer cells, increased ROS levels, upregulation of β-catenin and c-myc and downregulation of cyclin D1. Consistent with these data, overexpression of Ape1 in pancreatic cancer cells reduced ROS and c-myc levels and increased cyclin D1 levels. Moreover, treatment of pancreatic cancer cells with H2O2 to induce oxidative stress resulted in upregulated ROS levels, decreased Ape1 at both the mRNA and protein level, and alterations in WNT/β-catenin pathway components. Finally, treatment of pancreatic cancer cells with the WNT/β-catenin inhibitor IWR-1 resulted in growth inhibition, which was greatly enhanced when combined with E3330 treatment. In summary, our results demonstrate that ROS is an important intracellular messenger that can modulate WNT/β‑catenin signaling. The present study provides interesting new insight into crosstalk between the redox function of Ape1 and WNT/β-catenin signaling in cancer cells. Furthermore, our data show that the combination of Ape1 and WNT inhibitors enhanced the inhibition of pancreatic cell proliferation. These results provide a promising novel therapeutic strategy for treating pancreatic cancer in future.

Chou WC, Hu LY, Hsiung CN, Shen CY
Initiation of the ATM-Chk2 DNA damage response through the base excision repair pathway.
Carcinogenesis. 2015; 36(8):832-40 [PubMed] Related Publications
The DNA damage response (DDR) is activated by various genotoxic stresses. Base lesions, which are structurally simple and predominantly fixed by base excision repair (BER), can trigger the ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 (Chk2) pathway, a DDR component. How these lesions trigger DDR remains unclear. Here we show that, for alkylation damage, methylpurine-DNA glycosylase (MPG) and apurinic/apyrimidinic endonuclease 1, both of which function early in BER, are required for ATM-Chk2-dependent DDR. In addition, other DNA glycosylases, including uracil-DNA glycosylase and 8-oxoguanine glycosylase, which are involved in repairing deaminated bases and oxidative damage, also induced DDR. The early steps of BER therefore play a vital role in modulating the ATM-Chk2 DDR in response to base lesions, facilitating downstream BER processing for repair, in which the formation of a single-strand break was shown to play a critical role. Moreover, MPG knockdown rescued cell lethality, its overexpression led to cell death triggered by DNA damage and, more interestingly, higher MPG expression in breast and ovarian cancers corresponded with a greater probability of relapse-free survival after chemotherapy, underscoring the importance of glycosylase-dependent DDR. This study highlights the crosstalk between BER and DDR that contributes to maintaining genomic integrity and may have clinical applications in cancer therapy.

Zheng ZH, Du W, Li YJ, et al.
Lentiviral-mediated short hairpin RNA silencing of APE1 suppresses hepatocellular carcinoma proliferation and migration: A potential therapeutic target for hepatoma treatment.
Oncol Rep. 2015; 34(1):95-102 [PubMed] Related Publications
Apurinic/apyrimidinic endonuclease-1 (APE1) is a protein involved in DNA repair and transcriptional regulation of gene expression. APE1 expression was reported to be correlated with poor prognosis in hepatocellular carcinoma (HCC) patients. Based on our previous study, we hypothesized that APE1 may be involved in the metastatic progression of HCC. Thus, the present study aimed to investigate the knockdown effect of APE1 using shRNA in HCC and demonstrate that silencing of APE1 in MHCC97-H cells can decrease the oncogenic transforming potential in vitro and reduce the growth of HCC tumor xenografts in vivo. Silencing of APE1 expression decreased the cell proliferation and survival, reduced the cell adhesion ability in Matrigel or fibronectin-coated plates and suppressed the cell migration and invasion in a Transwell assay of HCC cells. In the xenograft study, tumor growth was markedly inhibited in the APE1-silenced group. Silencing of APE1 in MHCC97-H cells decreased the oncogenic transforming potential in vitro and reduced the growth of HCC tumor xenografts in vivo. Inhibition of APE1 may present a novel therapeutic approach for the treatment of HCC.

Dai ZJ, Shao YP, Kang HF, et al.
Relationship between apurinic endonuclease 1 Asp148Glu polymorphism and gastrointestinal cancer risk: An updated meta-analysis.
World J Gastroenterol. 2015; 21(16):5081-9 [PubMed] Article available free on PMC after 06/05/2017 Related Publications
AIM: To evaluate the relationship between apurinic endonuclease 1 (APE1) Asp148Glu polymorphism and the susceptibility to gastrointestinal (GI) cancers.
METHODS: We searched PubMed, ISI Web of Knowledge, and Chinese National Knowledge Infrastructure (CNKI) databases updated on July 15, 2014 for relevant studies. Only case-control studies comparing APE1 Asp148Glu polymorphism and GI cancer risk were included. We excluded studies reporting only standardized incidence ratios without control groups and those without detailed genotyping data. Meta-analysis was performed on 17 studies involving 4856 cancer patients and 6136 cancer-free controls. Review Manager version 5.1 was used to perform the meta-analysis. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated under the allele contrast, homozygous, heterozygous, dominant and recessive genetic models. We also conducted subgroup analyses stratified by ethnicity and cancer type. Publication bias was evaluated using Begg's test.
RESULTS: The meta-analysis showed a significant association between APE1 Asp148Glu polymorphism and GI cancer risk in three genetic models in the overall population (G vs T: OR = 1.18; 95%CI: 1.05-1.32; TG vs TT: OR = 1.28; 95%CI: 1.08-1.52; TG + GG vs TT: OR = 1.32; 95%CI: 1.10-1.57). Stratified analysis by ethnicity revealed a statistically increased GI cancer risk in Asians (G vs T: OR = 1.27; 95%CI: 1.07-1.51; GG vs TT: OR = 1.58; 95%CI: 1.05-2.38; TG vs TT: OR = 1.30; 95%CI, 1.01- 1.67; and TG + GG vs TT: OR = 1.38; 95%CI: 1.07-1.78), but not in Caucasians. Further subgroup analysis by cancer type indicated that APE1 Asp148Glu polymorphism may contribute to gastric cancer risk. However, Asp148Glu has no significant association with colorectal or esophageal cancer risk in any genetic model.
CONCLUSION: This meta-analysis suggests that the APE1 Asp148Glu polymorphism G allele is associated with an increased GI cancer risk, especially in gastric cancer.

Das S, Bhowmik A, Bhattacharjee A, et al.
XPD, APE1, and MUTYH polymorphisms increase head and neck cancer risk: effect of gene-gene and gene-environment interactions.
Tumour Biol. 2015; 36(10):7569-79 [PubMed] Related Publications
In the present study, we investigated the effect of the DNA repair gene polymorphisms XPD Asp312Asn (G>A), APE1 Asp148Glu (T>G), and MUTYH Tyr165Cys (G>A) on the risk for head and neck cancer (HNC) in association with tobacco use in a population of Northeast India. The study subjects comprised of 80 HNC patients and 92 healthy controls. Genotyping was performed using amplification refractory mutation system-PCR (ARMS-PCR) for XPD Asp312Asn (G>A) and PCR using confronting two-pair primers (PCR-CTPP) for APE1 Asp148Glu (T>G) and MUTYH Tyr165Cys (G>A). The XPD Asp/Asn genotype increased the risk for HNC by 2-fold (odds ratio, OR = 2.072; 95 % CI, 1.025-4.190; p < 0.05). Interaction between APE1 Asp/Asp and XPD Asp/Asn as well as MUTYH Tyr/Tyr and XPD Asp/Asn genotypes further increased the risk by 2.9 (OR = 2.97; 95 % CI, 1.16-7.61; p < 0.05) and 2.3 (OR = 2.37; 95 % CI, 1.11-5.10; p < 0.05) folds, respectively. The risk was further increased in heavy smokers with the XPD Asp/Asn genotype and heavy tobacco chewers with XPD Asn/Asn genotype by 7.7-fold (OR = 7.749; 95 % CI, 2.53-23.70; p < 0.05) and 10-fold (OR = 10; 95 % CI, 1.26-79.13; p < 0.05), respectively. We thus conclude that the XPD Asp312Asn and APE1 Asp148Glu polymorphisms increase the risk for HNC in association with smoking and/or tobacco chewing in the population under study.

Chen H, Li X, Li W, Zheng H
miR-130a can predict response to temozolomide in patients with glioblastoma multiforme, independently of O6-methylguanine-DNA methyltransferase.
J Transl Med. 2015; 13:69 [PubMed] Article available free on PMC after 06/05/2017 Related Publications
BACKGROUND: Currently, O6-methylguanine-DNA methyltransferase(MGMT) promoter methylation is the most convincing predictive biomarker for temozolomide (TMZ) response in patients with glioblastoma multiforme (GBM). However, technical obstacles prevent this biomarker from being applied widely. On the other hand, microRNAs (miRNAs) are easily investigated in the clinical setting using quantitative real-time polymerase chain reactions. This study aimed to identify miRNAs that could serve as predictive biomarkers for TMZ response.
METHODS: The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) databases were used to investigate the significance of associations between miRNA expression and overall survival (OS) in TMZ-treated patients with GBM. Cytotoxicity assays were used to validate the miRNAs' roles in the response of glioma cells to TMZ. Biological insights concerning the miRNAs were explored using gene set enrichment analysis (GSEA) and gene ontology (GO) analysis.
RESULTS: miR-130a was found to be significantly associated with OS in TMZ-treated patients from TCGA and the CGGA. In contrast, miR-130a appeared to be unassociated with OS in patients who only received radiotherapy. The TMZ cytotoxicity assay showed that miR-130a over-expression could sensitize response to TMZ in glioma cells. GSEA and GO analysis indicated that lower miR-130a could generate a more extensive response to oxidative stress, which in turn could elevate Ape1 and mediate resistance to TMZ. In vitro experiment verified that cells with lower miR-130a express higher Ape1 under oxidative stress.
CONCLUSIONS: Our data suggested that miR-130a could be a predictive marker for TMZ response in patients with GBM, independently of the mechanism by which MGMT acts as a biomarker. miR-130a could serve as a guide for treatment strategy selection in cases of GBM.

Poletto M, Malfatti MC, Dorjsuren D, et al.
Inhibitors of the apurinic/apyrimidinic endonuclease 1 (APE1)/nucleophosmin (NPM1) interaction that display anti-tumor properties.
Mol Carcinog. 2016; 55(5):688-704 [PubMed] Article available free on PMC after 01/05/2017 Related Publications
The apurinic/apyrimidinic endonuclease 1 (APE1) is a protein central to the base excision DNA repair pathway and operates in the modulation of gene expression through redox-dependent and independent mechanisms. Aberrant expression and localization of APE1 in tumors are recurrent hallmarks of aggressiveness and resistance to therapy. We identified and characterized the molecular association between APE1 and nucleophosmin (NPM1), a multifunctional protein involved in the preservation of genome stability and rRNA maturation. This protein-protein interaction modulates subcellular localization and endonuclease activity of APE1. Moreover, we reported a correlation between APE1 and NPM1 expression levels in ovarian cancer, with NPM1 overexpression being a marker of poor prognosis. These observations suggest that tumors that display an augmented APE1/NPM1 association may exhibit increased aggressiveness and resistance. Therefore, targeting the APE1/NPM1 interaction might represent an innovative strategy for the development of anticancer drugs, as tumor cells relying on higher levels of APE1 and NPM1 for proliferation and survival may be more sensitive than untransformed cells. We set up a chemiluminescence-based high-throughput screening assay in order to find small molecules able to interfere with the APE1/NPM1 interaction. This screening led to the identification of a set of bioactive compounds that impair the APE1/NPM1 association in living cells. Interestingly, some of these molecules display anti-proliferative activity and sensitize cells to therapeutically relevant genotoxins. Given the prognostic significance of APE1 and NPM1, these compounds might prove effective in the treatment of tumors that show abundant levels of both proteins, such as ovarian or hepatic carcinomas.

Sakai Y, Yamamori T, Yasui H, Inanami O
Downregulation of the DNA repair enzyme apurinic/apyrimidinic endonuclease 1 stimulates transforming growth factor-β1 production and promotes actin rearrangement.
Biochem Biophys Res Commun. 2015; 461(1):35-41 [PubMed] Related Publications
The DNA repair enzyme apurinic/apyrimidinic endonuclease 1 (APE1) plays a central role in base excision repair and functions as a reductive activator of various transcription factors. Multiple other functionalities have been ascribed to APE1 in addition to these major functions. A recent study showed that APE1 knockdown upregulated the expression of a set of genes related to extracellular matrix (ECM) production, indicating an additional novel biological role for this enzyme. Based on this finding, we have investigated the effect of APE1 downregulation on ECM-related gene expression and its biological consequences. Endogenous APE1 expression was downregulated in human cervical carcinoma HeLa cells and human lung carcinoma A549 cells using siRNA. When the expression of six ECM-related genes (TGFB1, LAMC1, FN1, COL1A1, COL3A1, and COL4A1) was evaluated, we found that APE1 knockdown upregulated the expression of TGFB1 in both cell lines. APE1 downregulation promoted actin rearrangement, inducing F-actin accumulation in HeLa cells and the dissipation of stress fibers in A549 cells. We also discovered that APE1 knockdown enhanced cellular motility in A549 cells, which was suppressed by the inhibition of transforming growth factor (TGF)-β1 signaling. These results suggested that APE1 controls the organization of actin cytoskeleton through the regulation of TGF-β1 expression, providing novel insights into the biological significance of APE1.

Yang S, Zhang J, Zhang Y, et al.
KDM1A triggers androgen-induced miRNA transcription via H3K4me2 demethylation and DNA oxidation.
Prostate. 2015; 75(9):936-46 [PubMed] Related Publications
BACKGROUND: Androgen receptor (AR) is a ligand dependent transcription factor that regulates the transcription of target genes. AR activity is closely involved in the maintenance and progression of prostate cancer. After the binding with androgen, AR moves into nucleus and binds to DNA sequence containing androgen response elements (ARE). Flavin-dependent monoamine oxidase KDM1A is necessary for AR driven transcription while the mechanism remains unclear.
METHODS: The association between androgen-dependent transcription and oxidation was tested through pharmaceutical inhibitions and siRNA knockdown of DNA oxidation repair components in prostate cancer cells. The recruitment of involved proteins and the histone methylation dynamics on ARE region was explored by chromatin immunoprecipitation (ChIP).
RESULTS: Oxidation inhibition reduced AR dependent expression of KLK3, TMPRSS2, hsa-miR-125b2, and hsa-miR-133b. And such reduction could be restored by H2 O2 treatment. KDM1A recruitment and H3K4me2 demethylation on ARE regions, which produce H2 O2 , are associated with AR targets transcription. AR targets transcription and coupled oxidation recruit 8-oxoguanine-DNA glycosylase (OGG1) and the nuclease APEX1 to ARE regions. Such recruitment depends on KDM1A, and is necessary for AR targets transcription.
CONCLUSION: Our work underlined the importance of histone demethylation and DNA oxidation/repairing machinery in androgen-dependent transcription. The present finds have implications for research into new druggable targets for prostate cancer relying on the cascade of AR activity regulation.

Maayah ZH, Ghebeh H, Alhaider AA, et al.
Metformin inhibits 7,12-dimethylbenz[a]anthracene-induced breast carcinogenesis and adduct formation in human breast cells by inhibiting the cytochrome P4501A1/aryl hydrocarbon receptor signaling pathway.
Toxicol Appl Pharmacol. 2015; 284(2):217-26 [PubMed] Related Publications
UNLABELLED: Recent studies have established that metformin (MET), an oral anti-diabetic drug, possesses antioxidant activity and is effective against different types of cancer in several carcinogen-induced animal models and cell lines. However, whether MET can protect against breast cancer has not been reported before. Therefore, the overall objectives of the present study are to elucidate the potential chemopreventive effect of MET in non-cancerous human breast MCF10A cells and explore the underlying mechanism involved, specifically the role of cytochrome P4501A1 (CYP1A1)/aryl hydrocarbon receptor (AhR) pathway. Transformation of the MCF10A cells into initiated breast cancer cells with DNA adduct formation was conducted using 7,12-dimethylbenz[a]anthracene (DMBA), an AhR ligand. The chemopreventive effect of MET against DMBA-induced breast carcinogenesis was evidenced by the capability of MET to restore the induction of the mRNA levels of basic excision repair genes, 8-oxoguanine DNA glycosylase (OGG1) and apurinic/apyrimidinic endonuclease1 (APE1), and the level of 8-hydroxy-2-deoxyguanosine (8-OHdG). Interestingly, the inhibition of DMBA-induced DNA adduct formation was associated with proportional decrease in CYP1A1 and in
NAD(P)H: quinone oxidoreductase 1 (NQO1) gene expression. Mechanistically, the involvements of AhR and nuclear factor erythroid 2-related factor-2 (Nrf2) in the MET-mediated inhibition of DMBA-induced CYP1A1 and NQO1 gene expression were evidenced by the ability of MET to inhibit DMBA-induced xenobiotic responsive element and antioxidant responsive element luciferase reporter gene expression which suggests an AhR- and Nrf2-dependent transcriptional control. However, the inability of MET to bind to AhR suggests that MET is not an AhR ligand. In conclusion, the present work shows a strong evidence that MET inhibits the DMBA-mediated carcinogenicity and adduct formation by inhibiting the expression of CYP1A1 through an AhR ligand-independent mechanism.

Kaur N, Dhiman M, Perez-Polo JR, Mantha AK
Ginkgolide B revamps neuroprotective role of apurinic/apyrimidinic endonuclease 1 and mitochondrial oxidative phosphorylation against Aβ25-35 -induced neurotoxicity in human neuroblastoma cells.
J Neurosci Res. 2015; 93(6):938-47 [PubMed] Related Publications
Accumulating evidence points to roles for oxidative stress, amyloid beta (Aβ), and mitochondrial dysfunction in the pathogenesis of Alzheimer's disease (AD). In neurons, the base excision repair pathway is the predominant DNA repair (BER) pathway for repairing oxidized base lesions. Apurinic/apyrimidinic endonuclease 1 (APE1), a multifunctional enzyme with DNA repair and reduction-oxidation activities, has been shown to enhance neuronal survival after oxidative stress. This study seeks to determine 1) the effect of Aβ25-35 on reactive oxygen species (ROS)/reactive nitrogen species (RNS) levels, 2) the activities of respiratory complexes (I, III, and IV), 3) the role of APE1 by ectopic expression, and 4) the neuromodulatory role of ginkgolide B (GB; from the leaves of Ginkgo biloba). The pro-oxidant Aβ25-35 peptide treatment increased the levels of ROS/RNS in human neuroblastoma IMR-32 and SH-SY5Y cells, which were decreased after pretreatment with GB. Furthermore, the mitochondrial APE1 level was found to be decreased after treatment with Aβ25-35 up to 48 hr, and the level was increased significantly in cells pretreated with GB. The oxidative phosphorylation (OXPHOS; activities of complexes I, III, and IV) indicated that Aβ25-35 treatment decreased activities of complexes I and IV, and pretreatment with GB and ectopic APE1 expression enhanced these activities significantly compared with Aβ25-35 treatment. Our results indicate that ectopic expression of APE1 potentiates neuronal cells to overcome the oxidative damage caused by Aβ25-35 . In addition, GB has been shown to modulate the mitochondrial OXPHOS against Aβ25-35 -induced oxidative stress and also to regulate the levels of ROS/RNS in the presence of ectopic APE1. This study presents findings from a new point of view to improve therapeutic potential for AD via the synergistic neuroprotective role played by APE1 in combination with the phytochemical GB.

Hsia KT, Liu CJ, Mar K, et al.
Impact of apurinic/apyrimidinic endonuclease 1/redox factor-1 on treatment response and survival in oral squamous cell carcinoma.
Head Neck. 2016; 38(4):550-9 [PubMed] Related Publications
BACKGROUND: Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multifunctional protein involved in DNA repair and redox signaling. The purpose of this study was to investigate the relationship between APE1/Ref-1 expression and clinicopathological features, survival, and treatment response in patients with oral squamous cell carcinoma (OSCC) and cell lines.
METHODS: APE1/Ref-1 expression in OSCC was evaluated by immunohistochemistry, and its relationship to patient outcomes and treatment response was assessed statistically. The effects of stable short hairpin (sh)RNA-mediated knockdown of APE1/Ref-1 on cell survival, migration, and chemoradiation sensitivity were determined in OSCC cell lines.
RESULTS: APE1/Ref-1 immunostaining was correlated with positive lymph node status, and higher APE1/Ref-1 expression was significantly associated with poor prognosis and reduced treatment response. Consistent with the clinical studies, APE1/Ref-1 expression in OSCC cell lines was implicated in the regulation of migration and cisplatin-induced apoptosis.
CONCLUSION: Elevated APE1/Ref-1 expression may be used to predict poor survival and may confer chemoresistance in OSCC.

Shan JL, He HT, Li MX, et al.
APE1 promotes antioxidant capacity by regulating Nrf-2 function through a redox-dependent mechanism.
Free Radic Biol Med. 2015; 78:11-22 [PubMed] Related Publications
APE1 is a multifunctional protein that has recently been implicated in protecting cells from oxidative stress. In the current study, we confirmed that APE1׳s effect on cellular antioxidant capacity is related to its redox activity through the use of an APE1 functional mutant, and we investigated the mechanism through which this multifunctional protein affects the function of the transcription factor Nrf-2 in regulating oxidative stress-induced genes. Using a pair of mutants for both the redox activity and the acetylation-regulated activity of APE1, in vitro assays showed that the redox activity of APE1 is crucial for its nuclear association with Nrf-2 and subsequent activation of Nrf-2׳s transcription of several downstream genes during oxidative challenge. Important oxidative stress genes are affected by APE1 redox activity, including Hmox1, Gstm1, and Txnrd1. In addition, utilizing human non-small-cell lung cancer sample tissue as well as a nude mouse xenograft model, we determined that APE1 expression levels are inversely correlated to oxidative stress in vivo. These findings indicated that interference with these crucial functions of APE1 shows promise in preventing resistance to certain radiotherapies and that further research is necessary to understand APE1׳s complex roles in regulating both the basal redox status and the oxidative stress state of the cellular environment.

Abdel-Fatah TM, Arora A, Alsubhi N, et al.
Clinicopathological significance of ATM-Chk2 expression in sporadic breast cancers: a comprehensive analysis in large cohorts.
Neoplasia. 2014; 16(11):982-91 [PubMed] Article available free on PMC after 01/05/2017 Related Publications
ATM-Chk2 network is critical for genomic stability, and its deregulation may influence breast cancer pathogenesis. We investigated ATM and Chk2 protein levels in two cohorts [cohort 1 (n = 1650) and cohort 2 (n = 252)]. ATM and Chk2 mRNA expression was evaluated in the Molecular Taxonomy of Breast Cancer International Consortium cohort (n = 1950). Low nuclear ATM protein level was significantly associated with aggressive breast cancer including larger tumors, higher tumor grade, higher mitotic index, pleomorphism, tumor type, lymphovascular invasion, estrogen receptor (ER)-, PR -, AR -, triple-negative, and basal-like phenotypes (Ps < .05). Breast cancer 1, early onset negative, low XRCC1, low SMUG1, high FEN1, high MIB1, p53 mutants, low MDM2, low Bcl-2, low p21, low Bax, high CDK1, and low Chk2 were also more frequent in tumors with low nuclear ATM level (Ps < .05). Low ATM protein level was significantly associated with poor survival including in patients with ER-negative tumors who received adjuvant anthracycline or cyclophosphamide, methotrexate, and 5-fluorouracil-based adjuvant chemotherapy (Ps < .05). Low nuclear Chk2 protein was likely in ER -/PR -/AR -; HER-2 positive; breast cancer 1, early onset negative; low XRCC1; low SMUG1; low APE1; low polβ; low DNA-PKcs; low ATM; low Bcl-2; and low TOPO2A tumors (P < .05). In patients with ER + tumors who received endocrine therapy or ER-negative tumors who received chemotherapy, nuclear Chk2 levels did not significantly influence survival. In p53 mutant tumors, low ATM (P < .000001) or high Chk2 (P < .01) was associated with poor survival. When investigated together, low-ATM/high-Chk2 tumors have the worst survival (P = .0033). Our data suggest that ATM-Chk2 levels in sporadic breast cancer may have prognostic and predictive significance.

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