Araştırma Çıktıları

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Author: search.filters.author.Muftuoglu, MeltemHas files: Yes

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    Targeting mitochondrial DNA polymerase gamma for selective inhibition of MLH1 deficient colon cancer growth
    (PUBLIC LIBRARY SCIENCE, 2022-01-01) Somuncu, Berna; Ekmekcioglu, Aysegul; Antmen, Fatma Merve; Ertuzun, Tugce; Deniz, Emre; Keskin, Nazli; Park, Joon; Yazici, Ilgu Ece; Simsek, Busra; Erman, Batu; Yin, Whitney; Erman, Burak; Muftuoglu, Meltem
    Synthetic lethality in DNA repair pathways is an important strategy for the selective treatment of cancer cells without harming healthy cells and developing cancer-specific drugs. The synthetic lethal interaction between the mismatch repair (MMR) protein, MutL homolog 1 (MLH1), and the mitochondrial base excision repair protein, DNA polymerasey (Poly) was used in this study for the selective treatment of MLH1 deficient cancers. Germline mutations in the MLH1 gene and aberrant MLH1 promoter methylation result in an increased risk of developing many cancers, including nonpolyposis colorectal and endometrial cancers. Because the inhibition of Poly in MLH1 deficient cancer cells provides the synthetic lethal selectivity, we conducted a comprehensive small molecule screening from various databases and chemical drug library molecules for novel Poly inhibitors that selectively kill MLH1 deficient cancer cells. We characterized these Poly inhibitor molecules in vitro and in vivo, and identified 3,3'-{[}(1,1'-Bipheny1)4',4'-diyl)bis(azo)]bis{[}4-amino-1-naphthalenesu lfonic acid] (congo red
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    Type I IFN-related NETosis in ataxia telangiectasia and Artemis deficiency
    (MOSBY-ELSEVIER, 2018-01-01) Gul, Ersin; Sayar, Esra Hazar; Gungor, Bilgi; Eroglu, Fehime Kara; Surucu, Naz; Keles, Sevgi; Guner, Sukru Nail; Findik, Siddika; Alpdundar, Esin; Ayanoglu, Ihsan Cihan; Kayaoglu, Basak; Geckin, Busra Nur; Sanli, Hatice Asena; Kahraman, Tamer; Yakicier, Cengiz; Muftuoglu, Meltem; Oguz, Berna; Ayvaz, Deniz Nazire Cagdas; Gursel, Ihsan; Ozen, Seza; Reisli, Ismail; Gursel, Mayda
    Background: Pathological inflammatory syndromes of unknown etiology are commonly observed in ataxia telangiectasia (AT) and Artemis deficiency. Similar inflammatory manifestations also exist in patients with STING-associated vasculopathy in infancy (SAVI). Objective: We sought to test the hypothesis that the inflammation-associated manifestations observed in patients with AT and Artemis deficiency stem from increased type I IFN signature leading to neutrophil-mediated pathological damage. Methods: Cytokine/protein signatures were determined by ELISA, cytometric bead array, or quantitative PCR. Stat1 phosphorylation levels were determined by flow cytometry. DNA species accumulating in the cytosol of patients' cells were quantified microscopically and flow cytometrically. Propensity of isolated polymorhonuclear granulocytes to form neutrophil extracellular traps (NETs) was determined using fluorescence microscopy and picogreen assay. Neutrophil reactive oxygen species levels and mitochondrial stress were assayed using fluorogenic probes, microscopy, and flow cytometry. Results: Type I and III IFNsignatures were elevated in plasma and peripheral blood cells of patients with AT, Artemis deficiency, and SAVI. Chronic IFN production stemmed fromthe accumulation of DNA in the cytoplasm of ATand Artemis-deficient cells. Neutrophils isolated from patients spontaneously produced NETs and displayed indicators of oxidative and mitochondrial stress, supportive of theirNETotic tendencies. Asimilar phenomenonwas also observed in neutrophils from healthy controls exposed to patient plasma samples or exogeneous IFN-alpha. Conclusions: Type I IFN-mediated neutrophil activation and NET formation may contribute to inflammatory manifestations observed in patients with AT, Artemis deficiency, and SAVI. Thus, neutrophils represent a promising target to manage inflammatory syndromes in diseases with active type I IFN signature.
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    Investigation of base excision repair gene variants in late-onset Alzheimer's disease
    (PUBLIC LIBRARY SCIENCE, 2019-01-01) Ertuzun, Tugce; Semerci, Asli; Cakir, Mehmet Emin; Ekmekcioglu, Aysegul; Gok, Mehmet Oguz; Soltys, Daniela T.; de Souza-Pinto, Nadja C.; Sezerman, Ugur; Muftuoglu, Meltem
    Base excision repair (BER) defects and concomitant oxidative DNA damage accumulation play a role in the etiology and progression of late-onset Alzheimer's disease (LOAD). However, it is not known whether genetic variant(s) of specific BER genes contribute to reduced BER activity in LOAD patients and whether they are associated with risk, development and/or progression of LOAD. Therefore, we performed targeted next generation sequencing for three BER genes, uracil glycosylase (UNG), endonuclease VIII-like DNA glycosylase 1 (NEIL1) and polymerase beta (POL beta) including promoter, exonic and intronic regions in peripheral blood samples and postmortem brain tissues (temporal cortex, TC and cerebellum, CE) from LOAD patients, high-pathology control and cognitively normal age-matched controls. In addition, the known LOAD risk factor, APOE was included in this study to test whether any BER gene variants associate with APOE variants, particularly APOE epsilon 4. We show that UNG carry five significant variants (rs1610925, rs2268406, rs80001089, rs1018782 and rs1018783) in blood samples of Turkish LOAD patients compared to age-matched controls and one of them (UNG rs80001089) is also significant in TC from Brazilian LOAD patients (p<0.05). The significant variants present only in CE and TC from LOAD are UNG rs2569987 and POL beta rs1012381950, respectively. There is also significant epistatic relationship (p = 0.0410) between UNG rs80001089 and NEIL1 rs7182283 in TC from LOAD subjects. Our results suggest that significant BER gene variants may be associated with the risk of LOAD in non-APOE epsilon 4 carriers. On the other hand, there are no significant UNG, NEIL1 and POL beta variants that could affect their protein level and function, suggesting that there may be other factors such as post-transcriptional or-translational modifications responsible for the reduced activities and protein levels of these genes in LOAD pathogenesis. Further studies with increased sample size are needed to confirm the relationship between BER variants and LOAD risk.
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    Non-muscle invasive bladder cancer tissues have increased base excision repair capacity
    (NATURE PORTFOLIO, 2020-01-01) Somuncu, Berna; Keskin, Selcuk; Antmen, Fatma Merve; Saglican, Yesim; Ekmekcioglu, Aysegul; Ertuzun, Tugce; Tuna, Mustafa Bilal; Obek, Can; Wilson, David M.; Ince, Umit; Kural, Ali Riza; Muftuoglu, Meltem
    The molecular mechanisms underlying the development and progression of bladder cancer (BC) are complex and have not been fully elucidated. Alterations in base excision repair (BER) capacity, one of several DNA repair mechanisms assigned to preserving genome integrity, have been reported to influence cancer susceptibility, recurrence, and progression, as well as responses to chemotherapy and radiotherapy. We report herein that non-muscle invasive BC (NMIBC) tissues exhibit increased uracil incision, abasic endonuclease and gap-filling activities, as well as total BER capacity in comparison to normal bladder tissue from the same patient (p<0.05). No significant difference was detected in 8-oxoG incision activity between cancer and normal tissues. NMIBC tissues have elevated protein levels of uracil DNA glycosylase, 8-oxoguanine DNA glycosylase, AP endonuclease 1 and DNA polymerase beta protein. Moreover, the fold increase in total BER and the individual BER enzyme activities were greater in high-grade tissues than in low-grade NMIBC tissues. These findings suggest that enhanced BER activity may play a role in the etiology of NMIBC and that BER proteins could serve as biomarkers in disease prognosis, progression or response to genotoxic therapeutics, such as Bacillus Calmette-Guerin.
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    5-Hydroxyuracil Incision Activity Varies According to the Histological Grade of Non-muscle-invasive Bladder Cancer
    (GALENOS YAYINCILIK, 2021-01-01) Keskin, Selcuk; Antmen, Fatma Merve; Somuncu, Berna; Saglican, Yesim; Doganca, Tunkut; Obek, Can; Ince, Umit; Kural, Ali Riza; Muftuoglu, Meltem
    Objective: High levels of endonuclease III-like 1 (NTHL1) DNA glycosylase, which plays a role in the first step of the base excision repair pathway, has been related to cancer initiation and progression. 5-hydroxyuracil (5-OHU) oxidative base damage is a substrate for NTHL1 and endonuclease VIII-like 1 enzyme 1 (NEIL1) DNA glycosylases. This study investigates the association of 5-OHU incision activity with the risk of disease progression in patients with non-muscle-invasive bladder cancer (NMIBC) regarding grade and stage. Materials and Methods: During transurethral resection of 17 NMIBC patients, the papillary tumour before monopolar resection and healthy bladder mucosal tissue from the same person were obtained using cold cup biopsy. Both the normal mucosa and NMIBC tumour were pathologically confirmed. The histological grade and stage were also determined. The 5-OHU incision activity of all tissues was measured using a radiolabelled 5-OHU modified base containing DNA substrate. Results: 5-OHU incision activity was significantly higher in all high-grade NMIBC tissue extracts compared with the corresponding normal tissues (p=0.001). However, we found no significant difference in 5-OHU incision activity in low-grade NMIBC tissues (p=0.89). There was also a significant increase in 5-OHU incision activity at the Ta/T1 stage compared with the corresponding normal tissue (p=0.001). Conclusion: The increase in 5-OHU incision activity according to the histological grade of NMIBC tissue indicates that this activity (mainly performed by NTHL1 and NEIL1 DNA glycosylases) might play a role in NMIBC prognosis. Thus, it could be used as a potential prognostic biomarker for NMIBC.
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    Bacillus Calmette-Guerin Increases Base Excision Repair in Bladder Cancer Cells
    (GALENOS YAYINCILIK, 2021-01-01) Keskin, Selcuk; Somuncu, Berna; Muftuoglu, Meltem
    Objective: Most patients with non-muscle-invasive bladder cancer (NMIBC) do not respond to intravesical Bacillus Calmette-Guerin (BCG) immunotherapy and have high risk of NMIBC recurrence and progression. In addition to its therapeutic effect which increases the local immune response, BCG also exerts an anti-tumour effect by increasing oxidative stress, and producing reactive oxygen species and oxidative DNA damage in bladder cancer (BC) cells. The oxidative DNA damage is repaired by base excision repair (BER) mechanism. Thus, BER capacity of BC cells could be an important factor in response to BCG therapy. Effects of BCG on the activity of BER in BC transitional carcinoma cell line, T24 have been investigated. Materials and Methods: The uracil-initiated total BER and BER enzyme activities were measured in whole cell extracts with or without BCG treatment using a {[}gamma-32P] adenosine triphosphate-labelled 51-mer DNA substrates. Results: BCG treatment increased the activities of uracil-initiated total BER and BER enzymes, uracil DNA glycosylase and DNA polymerase beta in 6 h and 24 h repair periods and increased the activity of 8-oxoguanine DNA glycosylase in 6 h repair in T24 BC cell line. Conclusion: The enhanced BER activity in BC cells in response to BCG treatment could be an important factor in BCG resistance.