Browsing by Author "Tepedelen B.E."

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    Synergistic effect of ponatinib and epigallocatechin-3-gallate induces apoptosis in chronic myeloid leukemia cells through altering expressions of cell cycle regulatory genes
    (Zerbinis Publications, 2014) Goker B.; Caliskan C.; Caglar H.O.; Kayabasi C.; Balci T.; Tepedelen B.E.; Aygunes D.; Susluer S.Y.; Mutlu Z.; Gunell N.S.; Korkmaz M.; Saydam G.; Gunduz C.; Avci C.B.
    Purpose: Ponatinib (P) has been used for the treatment of chronic myeloid leukemia (CML) and it is known that inhibition of BCR-ABL fusion protein by ponatinib induces apoptosis of CML cells. Epigallocatechin-3-gallate (EGCG), which is a polyphenol in green tea, induces apoptosis in different types of cancer cells. The purpose of this study was to determine the cytotoxic and apoptotic effects of ponatinib and EGCG combination in K562 CML cell line. This study also aimed to detect alterations of the expression levels of cell cycle-regulation related genes after ponatinib and EGCG combination in K562 CML cell line. Methods: The cytotoxic effects of the compounds on K562 cells were determined in a time- and dose-dependent manner by using WST-1 analysis. The combination index (CI) isobologram was used to analyze the data. Apoptotic effects of P-EGCG were defined by flow cytometry and gene expressions were detected by RT-qPCR. Results: IC50 values of ponatinib and EGCG were 87.13 nM and 50μM, respectively. CI value of the P-EGCG was 0.658 and the combination showed synergistic effect (ED90 value: 28.39 nM ponatinib, 117.12 μg/ml EGCG). Ponatinib, EGCG and P-EGCG induced apoptosis compared to control cells. CyclinDl and CDC25A were downregulated by P-EGCG by 2.49 and 2.63-fold, respectively. TGF-β2 was upregulated by 4.57-fold. Conclusion: EGCG possesses cytotoxic and apoptotic properties and may cooperate with the growth inhibiting activity of ponatinib synergistically against CML cells. P-EGCG mediated apoptosis might be associated with upregulation of TGF-β2 gene and downregulation of cyclinDl and CDC25A genes.
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    Boric Acid Reduces the Formation of DNA Double Strand Breaks and Accelerates Wound Healing Process
    (Humana Press Inc., 2016) Tepedelen B.E.; Soya E.; Korkmaz M.
    Boron is absorbed by the digestive and respiratory system, and it was considered that it is converted to boric acid (BA), which was distributed to all tissues above 90 %. The biochemical essentiality of boron element is caused by boric acid because it affects the activity of several enzymes involved in the metabolism. DNA damage repair mechanisms and oxidative stress regulation is quite important in the transition stage from normal to cancerous cells; thus, this study was conducted to investigate the protective effect of boric acid on DNA damage and wound healing in human epithelial cell line. For this purpose, the amount of DNA damage occurred with irinotecan (CPT-11), etoposide (ETP), doxorubicin (Doxo), and H2O2 was determined by immunofluorescence through phosphorylation of H2AX(Ser139) and pATM(Ser1981) in the absence and presence of BA. Moreover, the effect of BA on wound healing has been investigated in epithelial cells treated with these agents. Our results demonstrated that H2AX(Ser139) foci numbers were significantly decreased in the presence of BA while wound healing was accelerated by BA compared to that in the control and only drug-treated cells. Eventually, the results indicate that BA reduced the formation of DNA double strand breaks caused by agents as well as improving the wound healing process. Therefore, we suggest that boric acid has important therapeutical effectiveness and may be used in the treatment of inflammatory diseases where oxidative stress and wound healing process plays an important role. © 2016, Springer Science+Business Media New York.
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    Epigallocatechin-3-gallate reduces the proliferation of benign prostatic hyperplasia cells via regulation of focal adhesions
    (Elsevier Inc., 2017) Tepedelen B.E.; Soya E.; Korkmaz M.
    Aims Benign prostatic hyperplasia (BPH) is the most common urological disease that is characterized by the excessive growth of prostatic epithelial and stromal cells. Pharmacological therapy for BPH has limited use due to the many side effects so there is a need for new agents including natural compounds such as epigallocatechin-3-gallate (EGCG). This study was undertaken to assess the role of EGCG, suppressing the formation of BPH by reducing inflammation and oxidative stress, in cytoskeleton organization and ECM interactions via focal adhesions. Main methods We performed MTT assay to investigate cell viability of BPH-1 cells, wound healing assay to examine cell migration, immunofluorescence assay for F-actin organization and paxillin distribution and finally immunoblotting to investigate focal adhesion protein levels in the presence and absence of EGCG. Key findings We found that EGCG inhibits cell proliferation at the concentration of 89.12 μM, 21.2 μM and 2.39 μM for 24, 48 and 72 h, respectively as well as inhibitory effects of EGCG on BPH-1 cell migration were observed in a wound healing assay. Furthermore, it was determined by immunofluorescence labeling that EGCG disrupts F-actin organization and reduces paxillin distribution. Additionally, EGCG decreases the activation of FAK (Focal Adhesion Kinase) and the levels of paxillin, RhoA (Ras homolog gene family, member A), Cdc42 (cell division cycle 42) and PAK1 (p21 protein-activated kinase 1) in a dose-dependent manner. Significance For the first time, by this study, we found evidence that BPH-1 cell proliferation could be inhibited with EGCG through the disruption of cytoskeleton organization and ECM interactions. Consequently, EGCG might be useful in the prevention and treatment of diseases characterized by excessive cell proliferation such as BPH. © 2017
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    A Study on the Anticarcinogenic Effects of Calcium Fructoborate
    (Humana Press Inc., 2017) Tepedelen B.E.; Korkmaz M.; Tatlisumak E.; Uluer E.T.; Ölmez E.; Değerli İ.; Soya E.; İnan S.
    Evidences about the preventive and therapeutic effects of boron compounds on cancer have been increasing in the last years. Although calcium fructoborate (CaFB) is used as a nutritional supplement, data about its preventive and therapeutic effects on neoplastic transformations are limited. In the present study, the various concentrations of CaFB were applied to the MDA-MB-231 metastatic breast cancer cell line. First, we examined the cytotoxic effect and IC50 value of CaFB by MTT assay. For the evaluation of the DNA damage, apoptosis and metastatic potential, expression levels of ATM, pATM, PARP, p53, p-p53, caspase-3, caspase-9, and VEGF were investigated by using immunoblotting and immunohistochemical methods. Cell viability was significantly reduced at 50 μM CaFB treatment. pATM, p-p53, and caspase-9 levels increased significantly in all groups; furthermore, there was approximately 12.5-, 2.4-, and 10.7-fold increase, respectively, for 100 μM CaFB treatment. ATM and p53 levels did not change with CaFB treatment, but PARP levels significantly 2.5-fold decreased. While VEGF immunoreactivity decreased in all groups, significant increase in caspase-3 immunoreactivity was observed only in the group treated with 50 μM CaFB (p < 0,001). Our results imply that CaFB may have therapeutic potential as well as preventive benefits in cancer. © 2016, Springer Science+Business Media New York.
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    A Src/Abl kinase inhibitor, bosutinib, downregulates and inhibits PARP enzyme and sensitizes cells to the DNA damaging agents
    (Turkish Biochemistry Society, 2018) Kirmizibayrak P.B.; Ilhan R.; Yilmaz S.; Gunal S.; Tepedelen B.E.
    Background: Poly(ADP-ribosyl)ation (PARylation) catalyzed mainly by PARP1 is a highly regulated posttranslational modification associated with several pathways in cellular physiology and genotoxic deoxyribonucleic acid (DNA) damage response. PAR polymers and PARP enzyme function in DNA integrity maintenance and several PARP inhibitors have entered clinical phase studies for cancer therapies. Material and methods: The effect of bosutinib, a dual Src/ Abl kinase inhibitor, on PARylation was fluorometrically measured. The cytotoxic and chemosensitizing effects were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra-zolium bromide (MTT) assay. The levels of DNA repair proteins and PARP enzyme were examined by immunoblotting. Results: In this study, bosutinib is characterized as a novel PARP inhibitor. Bosutinib inhibited oxidative stress-induced cellular PARylation and nuclear foci formation by downregulating PARP1 levels. Bosutinib was found to be more cytotoxic on Capan1 cells with BRCA2 mutation. Furthermore by acting as a chemosensitizer, bosutinib enhanced the cytotoxicity of doxorubicin (DOXO) and etoposide (ETP) by decreasing phosphorylation of DNA repair enzymes checkpoint kinase 1 (Chk1) and ataxia-telangiectasia mutated (ATM). Conclusion: By inhibition of both PARP and DNA damage checkpoint kinases, bosutinib increased the phospho-H2AX levels, an early indicator of DNA double strand breaks. © 2018 Turkish Biochemistry Society. All rights reserved.