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Permanent URI for this collectionhttps://hdl.handle.net/11443/932

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Author: search.filters.author.Antmen, Fatma Merve

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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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    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.