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Citation Count: 8
The case of a cyst hydatid localized within the interatrial septum
(2004) Karabay,Ö.; Önen,A.; Yildiz,F.; Yilmaz,E.; Erdal,A.C.; Şanli,A.; Açikel,Ü.
The ratio of cardiac involvement of Echinoccocus granulosus is 0.02-2% and although seen rarely, involvement of the interatrial septum has also been reported in the published literature. The present case was a 19-year-old male university student admitted to hospital with complaints of headache and dizziness. Computerized tomography of the cranium revealed a cystic mass located at the frontal region and enucleation of the cyst was performed during surgery. A cystic lesion 5 × 4 cm in size was detected within the interatrial septum on two-dimensional transthoracic echocardiography during the postoperative period and the patient was referred to our clinic. Open heart surgery was performed and a hydatid cyst that involved the interatrial septum was enucleated. The cyst wall was sutured to the interatrial septum. No complications developed during the postoperative period. The patient was discharged on the fifth day of hospitalization and medical therapy was started with albendazole. Copyright © 2004 by the Japanese Heart Journal.
Citation Count: 38
Mechanisms of cellular resistance to imatinib in human chronic myeloid leukemia cells
(Taylor & Francis Ltd, 2007) Baran, Yusuf; Ural, Ali Ugur; Gunduz, Ufuk; Baran, Yusuf
A major advancement in the treatment of chronic myeloid leukemia (CML) has been the development of imatinib, which has shown striking activity in the chronic phase and the accelerated phase, but less so in the blast phase of the disease. Despite high rates of hematologic and cytogenetic responses to therapy, the emergence of resistance to imatinib has been recognized as a major problem in the treatment of patients with CML. Various cellular mechanisms may be involved in the nature of cellular resistance. Increased amount of target, alteration in structure of target proteins, decreased drug uptake and increased detoxification are well-known mechanisms of resistance. On the other hand, in some cases, even if anticancer drugs reach their sites of action, bypassing drug efflux system of the cells, some cells still may survive via the dysregulation of apoptotic signalling. In this study, mechanisms of resistance to imatinib-induced apoptosis in human Meg-01 CML cells were examined. Continuous exposure of cells to step-wise increasing concentrations of imatinib resulted in the selection of 200- and 1000 nM imatinib-resistant sub-lines referred to as Meg-01/IMA-0,2 and Meg-01/1MA-1, respectively. MTT cell proliferation, cell cycle analyses and trypan blue dye exclusion analyses showed that Meg-0l/IMA-1 cells were resistant to imatinib-induced apoptosis as compared to parental sensitive cells. There was an increased expression of BCR/ABL, Bcl-2 and an increase in mitochondrial membrane potential (MMP) detected in resistant cells comparing to parental sensitive cells. There was no mutation detected in imatinib binding site of ABL kinase region. Various diverse mechanisms have been reported for their involvement in the multidrug resistance. In this study, it has been shown that the degree of BCR/ABL expression appears to be directly proportional to the levels of imatinib resistance. In addition, there have been BCR/ABL-independent mechanisms reported for deriving resistance against imatinib. Our results revealed that besides BCR/ABL overexpression, imatinib resistance also depends on the inhibition of apoptosis as a result of up-regulation of anti-apoptotic stimuli and down-regulation of pro-apoptotic stimuli through MMP but does not depend on any mutation on imatinib binding site of ABL kinase.
Citation Count: 35
Upregulation of multi drug resistance genes in doxorubicin resistant human acute myelogeneous leukemia cells and reversal of the resistance
(Maney Publishing, 2007) Baran, Yusuf; Guer, Bala; Kaya, Pelin; Ural, Ali Ugur; Avcu, Ferit; Guenduez, Ufuk; Baran, Yusuf
The major problem in the treatment of acute myeloid leukemia (AML) patients results from multidrug resistance to administered anticancer agents. Drug resistance proteins, MDR1 and MRP1, which work as drug efflux pumps, can mediate the multidrug resistance of human leukemia cells. In this study, the mechanisms of resistance to doxorubicin-induced cell death in human HL60 AML cells were examined. Continuous exposure of cells to step-wise increasing concentrations of doxorubicin resulted in the selection of HL60/DOX cells, which expressed about 10.7-fold resistance as compared to parental sensitive cells. The expression analyses of MRP1 and MDR1 drug efflux proteins in doxorubicin-sensitive and -resistant HL60 cells revealed that there was an upregulation of MRP1 gene in HL60/DOX cells as compared to parental sensitive cells. On the other hand, while there was no expression of MDR1 gene in parental cells, the expression of MDR1 gene was upregulated in HL60/DOX cells. HL60/DOX cells also showed cross-resistance to cytosine arabinoside (Ara-c). This resistance was reversed by a combination therapy of Ara-c and cyclosporine A. However, the expression levels of CD15 and CD16 surface markers were significantly decreased in HL60/DOX cells.
Citation Count: 27
No association of interleukin-6 gene polymorphism (-174 G/C) with premature coronary artery disease in a Turkish cohort
(2007) Sekuri,C.; Cam,F.S.; Sagcan,A.; Ercan,E.; Tengiz,I.; Alioglu,E.; Berdeli,A.
OBJECTIVES: Interleukin-6 (IL-6) may contribute to the inflammatory response by activating endothelial cells and stimulating the synthesis of fibrinogen. It might thus be important in the pathogenesis of inflammation associated with coronary artery disease (CAD). Several studies suggested that the -174 C allele was associated with an increased prevalence of coronary heart disease. The aim of this study was to investigate further the association of the IL-6 -174 G/C allele status with premature CAD. METHODS: A total of 120 patients and 105 controls were included in the study. The IL-6 -174 G/C polymorphism was genotyped using PCR-restriction fragment length polymorphism. RESULTS: The genotype distribution of the -174 G/C polymorphism was not different in premature CAD patients (GG: 53%; GC: 42.6%; CC: 4.3%) and controls (GG: 54.3%; GC: 39%; CC: 6.7%) (P=0.72). The prevalence of the C allele was 25.6% in patients and 26.1% in controls. By multiple regression analysis, family history, smoking, diabetes, and hypertension were independent risk factors of premature CAD, but not IL-6 genotype. CONCLUSIONS: We conclude that the IL-6 -174 G/C polymorphism is not associated with the risk of premature CAD, and does not contribute to cardiovascular risk stratification. © 2007 Lippincott Williams & Wilkins, Inc.
Citation Count: 3
Regulation of mRNA stability through a pentobarbital-responsive element
(Elsevier Science inc, 2007) Akgul, Bunyamin; Tu, Chen-Pei D.; Akgül, Bünyamin
Pentobarbital, a general anesthetic and non-genotoxic carcinogen, can induce gene expression by activating transcription. In the Drosophila glutathione S-transferase D21 (gstD21) gene, pentobarbital's regulatory influence extends to the level of mRNA turnover. Transcribed from an intronless gene, gstD21 mRNA is intrinsically very labile. But exposure to pentobarbital renders it stabilized beyond what can be attributed to transcriptional activation. We aim here to identify cis-acting element(s) of gstD21 mRNA as contributors to the molecule's pentobarbital-mediated stabilization. In the context of hsp70 5'UTR and the 3'UTR of act5C, gstD21 mRNA, minus its native UTRs, is stable. Maintaining the same context of heterologous UTRs, we can reconstitute using the full-length gstD21 sequence the inherent instability of gstD21 mRNA and its stabilization by pentobarbital. Transgenic flies that express these chimeric gstD21 mRNA exhibit decay intermediates lacking 3'UTR, which are not stabilized by PB treatment. The 3'UTR sequence, when inserted downstream from a reporter transcript, stabilizes it 1.6-fold under PB treatment. The analysis of the decay intermediates suggests a polysome-associated decay pattern. We propose a regulatory model that features a 59-nucleotide pentobarbital-responsive element (PBRE) in the 3'UTR of gstD21 mRNA. (c) 2006 Elsevier Inc. All rights reserved.
Citation Count: 12
Bisphosphonate treatment and radiotherapy in metastatic breast cancer
(Humana Press inc, 2008) Ural, A. Ugur; Avcu, Ferit; Baran, Yusuf; Baran, Yusuf
Patients with advanced breast cancer frequently develop metastasis to bone. Bone metastasis results in intractable pain and high risk of pathologic fractures due to osteolysis. The treatment of breast cancer patients with bone metastases requires a multidisciplinary approach. Radiotherapy is an established treatment for metastatic bone pain. It may be delivered either as a localized low dose treatment for localized bone pain or systemically for more widespread symptoms. Bisphosphonates have been shown to reduce morbidity and bone pain from bone metastases when given to patients with metastatic bone disease. In vivo studies indicate that early bisphosphonates administration in combination with radiotherapy improves remineralization and restabilization of osteolytic bone metastases in animal tumor models. This review focused on a brief discussion about biology of bone metastases, the effects of radiotherapy and bisphosphonate therapy, and possible mechanisms of combination therapy in metastatic breast cancer patients.
Citation Count: 27
Formation of Pseudoisocyanine J-Aggregates in Poly(vinyl alcohol) Fibers by Electrospinning
(Amer Chemical Soc, 2009) Demir, Mustafa M.; Ozen, Bengisu; Ozcelik, Serdar; Demir, Mustafa
Submicrometer diameter, light emitting fibers of poly(vinyl alcohol) (PVA) doped with pseudoisocyanine (1, 1'-diethyl-2,2'-cyanine bromide, PIC) dye were prepared by electrospinning. A horizontal setup was employed with a stationary collector consisting of two parallel-positioned metal strips separated by a void gal). Formation of uniaxially aligned and randomly deposited fibers in electrospun films was confirmed by microscopy. Photoluminescence (PL) spectroscopy is used to evaluate spectral properties of both types of fibers doped with PIC. While PIC molecules were individually dispersed in PVA Solution, they assemble into J-aggregates upon electrospinning when the weight fraction of PIC molecules is above 2.5 wt%. The formation of J-aggregates was observed in both randomly deposited and Uniaxially aligned electrospun fibers. Moreover, the fibers aligned uniaxially showed a high degree of polarized emission (PL(parallel to)/PL(perpendicular to) = 10), arising from the orientation of J-aggregates along the fiber axis. On the other hand, isotropic emission of J-aggregates was observed from the fibers deposited randomly. As a conclusion, electrospinning was found to be an efficient and a practical method to form highly oriented J-aggregates dispersed into polymer fibers. To the best Of Our knowledge, it is the first time formation of J-aggregates (a bottom-up approach) and electrospinning (a top-down approach) is successfully combined.
Citation Count: 39
Investigation of Oxygen Permeation through Composites of PMMA and Surface-Modified ZnO Nanoparticles
(Wiley-v C H verlag Gmbh, 2009) Hess, Sandra; Demir, Mustafa M.; Yakutkin, Vladimir; Baluschev, Stanislav; Wegner, Gerhard; Demir, Mustafa
oxygen permeabilities of nanocomposite films consisting of poly(methyl methacrylate) (PMMA) and different amounts of spherical zinc oxide (ZnO) nanoparticles were determined to investigate the barrier effect of this material with respect to particle content. A method was applied which is based on quenching of an excited phosphorescent dye by oxygen. Possible effects of the nanoparticles on the response of the dye molecules were investigated and were ruled out.
Citation Count: 25
Multidrug Resistance Mediated by MRP1 Gene Overexpression in Breast Cancer Patients
(Taylor & Francis inc, 2009) Abaan, Ogan Demir; Mutlu, Pelin Kaya; Baran, Yusuf; Atalay, Can; Gunduz, Ufuk; Baran, Yusuf
Multidrug resistance (MDR) is a serious handicap towards the effective treatment of breast cancer patients. One of the most prevalent MDR mechanisms is through the overexpression of genes coding the proteins called Multidrug Resistance-associated Proteins (MRPs). The aim of this study was to investigate the expression of MRP1 in tumor tissues from breast cancer patients. In this study, a semi-quantitative RT-PCR approach was utilized. Our results suggest that MRP1 overexpression can mediate MDR in patients. Pre-evaluation of the level of such MDR mediators before chemotherapy can increase the efficacy of the treatment.
Citation Count: 6
Docetaxel enhances the cytotoxic effects of imatinib on Philadelphia positive human chronic myeloid leukemia cells
(Taylor & Francis Ltd, 2009) Gucluler, Gozde; Baran, Yusuf; Baran, Yusuf
Chronic myelogenous leukemia (CML) results from a translocation between chromosomes 9 and 22 which generates BCR/ABL fusion protein and characterized by uncontrolled proliferation of immature white blood cells. Imatinib, a molecularly targeting anticancer agent, is used widely for the treatment of CML and showed significant activity in chronic and accelerated phases but much less in blast crisis phase. The resistance to imatinib especially in blast crisis phase is recognized as a major problem in the treatment of CML patients. Docetaxel is shown to arrest cells in G2/M phase of the cell cycle which makes cells more sensitive to chemo- and radiotherapy. In this study, we aimed to increase chemosensitivity of human K562 CML cells to imatinib in combination with docetaxel. Taken together, our results showed that the combination of imatinib and docetaxel decreased cellular proliferation and increased apoptosis in human K562 chronic myeloid leukemia cells as compared to any agent alone. Imatinib and docetaxel induced apoptosis through caspase-3 enzyme activity and mitochondrial membrane potential.
Citation Count: 66
Sorption Efficiency of Chitosan Nanofibers toward Metal Ions at Low Concentrations
(Amer Chemical Soc, 2010) Horzum, Nesrin; Boyaci, Ezel; Eroglu, Ahmet E.; Shahwan, Talal; Demir, Mustafa M.; Demir, Mustafa
Chitosan fibers showing narrow diameter distribution with a mean of 42 nm were produced by electrospinning and utilized for the sorption of Fe(III), Cu(II), Ag(I), and Cd(II) ions from aqueous solutions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The filtration efficiency of the fibers toward these ions was studied by both batch and microcolumn methods. High efficiency in sorption of the metal ions was obtained in the both methods. The effects of sorbent amount (0.10-0.50 mg), shaking time (15-120 min), initial metal ion concentration (10.0-1000.0 mu g.L-1), and temperature (25 and 50 degrees C) on the extent of sorption were examined. The sorbent amount did not significantly alter the efficiency of sorption; however, shaking time, temperature, and metal ion concentration were found to have a strong influence on sorption. By virtue of its mechanical integrity, the applicability of the chitosan mat in solid phase extraction under continuous flow looks promising.
Citation Count: 7
Nilotinib significantly induces apoptosis in imatinib resistant K562 cells with wild-type BCR-ABL, as effectively as in parental sensitive counterparts
(Taylor & Francis Ltd, 2010) Ekiz, Huseyin Atakan; Can, Geylani; Gunduz, Ufuk; Baran, Yusuf; Baran, Yusuf
Chronic myeloid leukemia (CML) is a hematological malignancy characterized by high levels of immature white blood cells. CML is caused by the translocation between chromosomes 9 and 22 (which results in the formation of the Philadelphia chromosome) creating BCR-ABL fusion protein. Imatinib and nilotinib are chemotherapeutic drugs which specifically bind to the BCR-ABL and inhibit cancer cells. Nilotinib is more effective in this respect than imatinib. We have shown that nilotinib induces apoptosis in imatinib-resistant K562 CML cells which have the wild-type BCR-ABL fusion gene almost to the same extent as it does in the parental sensitive cells by the increase in caspase-3 enzyme activity and the decrease in mitochondrial membrane potential. This effect of nilotinib, even in low concentrations, may indicate the efficacy of the usage of nilotinib in imatinib-resistant CML with less risk of undesired cytotoxic effects in the remaining cells of the body.
Citation Count: 19
Suppression of STAT5A increases chemotherapeutic sensitivity in imatinib-resistant and imatinib-sensitive K562 cells
(Taylor & Francis Ltd, 2010) Kosova, Buket; Tezcanli, Burcin; Ekiz, Huseyin Atakan; Cakir, Zeynep; Selvi, Nur; Dalmizrak, Aysegul; Baran, Yusuf; Baran, Yusuf
STAT proteins are cytoplasmic transcription factors that are involved in the regulation of numerous cellular activities such as cell growth, differentiation, and survival. In this study, we aimed to identify the expression pattern of STAT genes in imatinib-sensitive and -resistant K562 cells, and further, to reveal the effects of STAT5A siRNA knockdown on cell growth and apoptosis induction. The XTT cell proliferation assay showed that both sensitive and resistant K562 cells were sensitized to imatinib upon transfection with STAT5A siRNA. Caspase-3 enzyme activity was increased significantly in both cells. These results may open up new opportunities to overcome chemotherapeutic resistance in leukemia.
Citation Count: 72
Sorption efficiency of chitosan nanofibers toward metal ions at low concentrations
(2010) Horzum N.; Boyaci E.; Eroǧlu A.E.; Shahwan T.; Demir, M.M.
Chitosan fibers showing narrow diameter distribution with a mean of 42 nm were produced by electrospinning and utilized for the sorption of Fe(III), Cu(II), Ag(I), and Cd(II) ions from aqueous solutions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The filtration efficiency of the fibers toward these ions was studied by both batch and microcolumn methods. High efficiency in sorption of the metal ions was obtained in the both methods. The effects of sorbent amount (0.10-0.50 mg), shaking time (15-120 min), initial metal ion concentration (10.0-1000.0 μg·L-1), and temperature (25 and 50°C) on the extent of sorption were examined. The sorbent amount did not significantly alter the efficiency of sorption; however, shaking time, temperature, and metal ion concentration were found to have a strong influence on sorption. By virtue of its mechanical integrity, the applicability of the chitosan mat in solid phase extraction under continuous flow looks promising. © 2010 American Chemical Society.
Citation Count: 32
Therapeutic applications of bioactive sphingolipids in hematological malignancies
(Wiley, 2010) Ekiz, Huseyin Atakan; Baran, Yusuf; Baran, Yusuf
Sphingolipids are sphingosine-based lipid molecules that have important functions in cellular signal transduction and in a variety of cellular processes including proliferation, differentiation, programmed cell death (apoptosis) and responses to stressful conditions. Ceramides, dihydroceramide, sphingosine and sphingosine-1-phosphate are examples of those bioactive sphingolipids. They have a major impact on determination of the cell fate by contributing to the cell survival or cell death through apoptosis. Despite the number of carbon atoms in the fatty acid chain changes the physiological role; ceramides generally exert suppressive roles on the cell proliferation. There have been several enzymes identified in this pathway that are responsible for the conversion of ceramide into other sphingolipid derivatives. Those,derivatives also have differential roles on those cellular process. Sphingosine-1-phosphate is an example of such sphingolipid derivatives which has antiapoptotic effects. As they have significant impacts particularly on the cell death and survival, bioactive sphingolipids have a great potential to be targets in cancer therapy. Increasing number of studies indicates that sphingolipid derivatives are important in the progression of hematological malignancies, and they are also involved in the resistance to current chemotherapeutic options. This review compiles the current knowledge in this area for enlightening the therapeutic potentials of bioactive sphingolipids in various leukemias.
Citation Count: 10
Garlic Accelerates Red Blood Cell Turnover and Splenic Erythropoietic Gene Expression in Mice: Evidence for Erythropoietin-Independent Erythropoiesis
(Public Library Science, 2010) Akgul, Bunyamin; Lin, Kai-Wei; Yang, Hui-Mei Ou; Chen, Yen-Hui; Lu, Tzu-Huan; Chen, Chien-Hsiun; Tu, Chen-Pei D.; Akgül, Bünyamin
Garlic (Allium sativum) has been valued in many cultures both for its health effects and as a culinary flavor enhancer. Garlic's chemical complexity is widely thought to be the source of its many health benefits, which include, but are not limited to, anti-platelet, procirculatory, anti-inflammatory, anti-apoptotic, neuro-protective, and anti-cancer effects. While a growing body of scientific evidence strongly upholds the herb's broad and potent capacity to influence health, the common mechanisms underlying these diverse effects remain disjointed and relatively poorly understood. We adopted a phenotype-driven approach to investigate the effects of garlic in a mouse model. We examined RBC indices and morphologies, spleen histochemistry, RBC half-lives and gene expression profiles, followed up by qPCR and immunoblot validation. The RBCs of garlic-fed mice register shorter half-lives than the control. But they have normal blood chemistry and RBC indices. Their spleens manifest increased heme oxygenase 1, higher levels of iron and bilirubin, and presumably higher CO, a pleiotropic gasotransmitter. Heat shock genes and those critical for erythropoiesis are elevated in spleens but not in bone marrow. The garlic-fed mice have lower plasma erythropoietin than the controls, however. Chronic exposure to CO of mice on garlic-free diet was sufficient to cause increased RBC indices but again with a lower plasma erythropoietin level than air-treated controls. Furthermore, dietary garlic supplementation and CO treatment showed additive effects on reducing plasma erythropoietin levels in mice. Thus, garlic consumption not only causes increased energy demand from the faster RBC turnover but also increases the production of CO, which in turn stimulates splenic erythropoiesis by an erythropoietin-independent mechanism, thus completing the sequence of feedback regulation for RBC metabolism. Being a pleiotropic gasotransmitter, CO may be a second messenger for garlic's other physiological effects.
Citation Count: 22
Proteasome Inhibitor Bortezomib Increases Radiation Sensitivity in Androgen Independent Human Prostate Cancer Cells
(Elsevier Science inc, 2010) Goktas, Serdar; Baran, Yusuf; Ural, Ali U.; Yazici, Sertac; Aydur, Emin; Basal, Seref; Beyzadeoglu, Murat; Baran, Yusuf
OBJECTIVES To investigate the effects of a strong proteasome inhibitor, bortezomib alone or in combination with radiotherapy on androgen-independent DU145 human prostate cancer cells. Proteasomes play important roles in cell cycle, proliferation, apoptosis, angiogenesis, and cellular resistance to chemotherapy and radiotherapy. METHODS Increasing concentrations of bortezomib alone or in combination with radiation were applied to DU145 cells and IC50 values that inhibited cell growth by 50% were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium- bromide assay. Apoptosis was determined using annexin V staining by flow cytometry. mRNA levels of proapoptotic caspase-3 and antiapoptotic Bcl-2 genes were examined by reverse transcriptase polymerase chain reaction. RESULTS The IC50 value of bortezomib was found to be 28 mu M although 400- and 800-cGy radiation decreased the cell proliferation by 14% and 28%, respectively. In 400- and 800-cGy radiation applied DU145 cells, IC50 value of bortezomib decreased to 23- and 12 mu M, respectively. Exposure to 5 mu M bortezomib for 48 hours caused apoptosis in 35% of the population whereas 800-cGy radiation resulted apoptosis in 14% of cells. However, 42% of DU145 cells that were exposed to 800 cGy and 5 mu M bortezomib underwent apoptosis. Reverse transcriptase polymerase chain reaction results showed a significant decrease in mRNA levels of antiapoptotic Bcl-2 gene and an increase in proapoptotic caspase-3 gene expression in the combination group compared to control group. CONCLUSIONS Bortezomib increases radiation sensitivity in androgen-independent human DU145 prostate cancer cells through inhibition of Bcl-2 and induction of caspase-3 genes. UROLOGY 75: 793-798, 2010. (C) 2010 Elsevier Inc.
Citation Count: 7
Combination of Fludarabine and Imatinib Induces Apoptosis Synergistically Through Loss of Mitochondrial Membrane Potential and Increases in Caspase-3 Enzyme Activity in Human K562 Chronic Myleloid Leukemia Cells
(informa Healthcare, 2010) Yusuf, Baran; Baran, Yusuf; Oztekin, Coskun; Yonca, Bassoy Esen
In this study, we aimed to show the synergistic apoptotic effects of imatinib/fludarabine combination in human K562 chronic myleloid leukemia (CML) cells. There was a significant increase in cytotoxicity of combination of imatinib and fludarabine as compared to any agent alone. On the other hand, combination of both agents induced apoptosis significantly as confirmed by increases in caspase-3 enzyme activity and decreases in mitochondrial membrane potential. As a summary, the results of this study strongly suggest that combination of imatinib and fludarabine induced cell death synergistically comparing to only imatinib or fludarabine in human K562 CML cells.
Citation Count: 46
Targeting glucosylceramide synthase sensitizes imatinib-resistant chronic myeloid leukemia cells via endogenous ceramide accumulation
(Springer, 2011) Baran, Yusuf; Bielawski, Jacek; Gunduz, Ufuk; Ogretmen, Besim; Baran, Yusuf
Purpose Drug resistance presents a major obstacle for the treatment of some patients with chronic myeloid leukemia (CML). Pro-apoptotic ceramide mediates imatinib-induced apoptosis, and metabolism of ceramide by glucosylceramide synthase (GCS) activity, converting ceramide to glucosyl ceramide, might contribute to imatinib resistance. In this study, we investigated the role of ceramide metabolism by GCS in the regulation of imatinib-induced apoptosis in drug-sensitive and drug-resistant K562 and K562/IMA-0.2 and K562/IMA-1 human CML cells, which exhibit about 2.3- and 19-fold imatinib resistance, respectively. Methods Cytotoxic effects of PDMP and imatinib were determined by XTT cell proliferation assay. Expression levels of GCS were determined by RT-PCR and western blot. Intracellular ceramide levels were determined by LC-MS. Cell viability analyses was conducted by Trypan blue dye exclusion assay. Cell cycle and apoptosis analyses were examined by flow cytometry. Results We first showed that mRNA and protein levels of GCS are increased in drug-resistant K562/IMA as compared to sensitive K562 cells. Next, forced expression of GCS in sensitive K562 cells conferred resistance to imatinib-induced apoptosis. In reciprocal experiments, targeting GCS using its known inhibitor, PDMP, enhanced ceramide accumulation and increased cell death in response to imatinib in K562/IMA cells. Conclusion Our data suggest the involvement of GCS in resistance to imatinib-induced apoptosis, and that targeting GCS by PDMP increased imatinib-induced cell death in drug-sensitive and drug-resistant K562 cells via enhancing ceramide accumulation.
Citation Count: 25
Caffeic acid phenethyl ester triggers apoptosis through induction of loss of mitochondrial membrane potential in CCRF-CEM cells
(Springer, 2011) Avci, Cigir Biray; Gunduz, Cumhur; Baran, Yusuf; Sahin, Fahri; Yilmaz, Sunde; Dogan, Zeynep Ozlem; Saydam, Guray; Baran, Yusuf
CAPE (caffeic acid phenethyl ester) is one of the most valuable and investigated component of propolis which is composed by honeybees. In the current study, we aimed at examining apoptotic effects of CAPE on CCRF-CEM leukemic cells and at determining the roles of mitochondrial membrane potential (MMP) in cell death. Trypan blue and XTT methods were used to evaluate the cytotoxicity. Apoptosis was examined by ELISA-based oligonucleotide and acridine orange/ethidium bromide dye techniques. Loss of mitochondrial membrane potential was evaluated using JC-1 dye by flow cytometric analysis and under fluorescent microscope. We detected the time- and dose-dependent increases in cytotoxic effect of CAPE on CCRF-CEM cells. ELISA and acridine orange/ethidium bromide results showed that apoptotic cell population increased significantly in CCRF-CEM cells exposed to increasing concentrations of CAPE. On the other hand, there was significant loss of MMP determined in response to CAPE in CCRF-CEM cells. This in vitro data by being supported with clinical data may open the way of the potential use of CAPE for the treatment of leukemia.

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