Browsing by Author "Can, Geylani"

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Citation Count: 19
Apoptotic Effects of Resveratrol, a Grape Polyphenol, on Imatinib-Sensitive and Resistant K562 Chronic Myeloid Leukemia Cells
(int inst Anticancer Research, 2012) Can, Geylani; Cakir, Zeynep; Kartal, Melts; Gunduz, Ufuk; Baran, Yusuf; Baran, Yusuf
Aim: To examine the antiproliferative and apoptotic effects of resveratrol on imatinib-sensitive and imatinib-resistant K562 chronic myeloid leukemia cells. Materials and Methods: Antiproliferative effects of resveratrol were determined by the 3-Bis[2-methoxy-4-nitro-5-sulphophenyl]-2H-tetrazolium-5-carboxanilide inner salt (XTT) cell proliferation assay. Apoptotic effects of resveratrol on sensitive K562 and resistant K562/IMA-3 cells were determined through changes in caspase-3 activity, loss of mitochondrial membrane potential (MMP), and apoptosis by annexin V-(FITC). Results: The concentrations of resveratrol that inhibited cell growth by 50% (IC50) were calculated as 85 and 122 mu M for K562 and K562/IMA-3 cells, respectively. There were 1.91-, 7.42- and 14.73-fold increases in loss of MMP in K562 cells treated with 10, 50, and 100 mu M resveratrol, respectively. The same concentrations of resveratrol resulted in 2.21-, 3.30- and 7.65-fold increases in loss of MMP in K562/IMA3 cells. Caspase-3 activity increased 1.04-, 2.77- and 4.8-fold in K562 and 1.02-, 1.41- and 3.46-fold in K562/IMA3 cells in response to the same concentrations of resveratrol, respectively. Apoptosis was induced in 58.7%- and 43.3% of K562 and K562/IMA-3 cells, respectively, in response to 100 mu M resveratrol. Conclusion: Taken together these results may suggest potential use of resveratrol in CML, as well as in patients with primary and/or acquired resistance to imatinib.
Citation Count: 38
Autologous rabbit adipose tissue-derived mesenchymal stromal cells for the treatment of bone injuries with distraction osteogenesis
(Elsevier Sci Ltd, 2013) Sunay, Ozgur; Can, Geylani; Cakir, Zeynep; Denek, Ziya; Kozanoglu, Ilknur; Erbil, Guven; Baran, Yusuf; Baran, Yusuf
Background aims. Adipose tissue-derived mesenchymal stromal cells (MSCs) have a higher capacity for proliferation and differentiation compared with other cell lineages. Although distraction osteogenesis is the most important therapy for treating bone defects, this treatment is restricted in many situations. The aim of this study was to examine the therapeutic potential of adipose tissue-derived MSCs and osteoblasts differentiated from adipose tissue-derived MSCs in the treatment of bone defects. Methods. Bone defects were produced in the tibias of New Zealand rabbits that had previously undergone adipose tissue extraction. Tibial osteotomy was performed, and a distractor was placed on the right leg of the rabbits. The rabbits were placed in control (group I), stem cell (group II) and osteoblast-differentiated stem cell (group III) treatment groups. The rabbits were sacrificed, and the defect area was evaluated by radiologic, biomechanical and histopathologic tests to examine the therapeutic effects of adipose tissue-derived MSCs. Results. Radiologic analyses revealed that callus density and the ossification rate increased in group III compared with group I and group II. In biomechanical tests, the highest ossification rate was observed in group III. Histopathologic studies showed that the quality of newly formed bone and the number of cells active in bone formation were significantly higher in group III rabbits compared with group I and group II rabbits. Conclusions. These data reveal that osteoblasts differentiated from adipose tissue-derived MSCs shorten the consolidation period of distraction osteogenesis. Stem cells could be used as an effective treatment for bone defects.
Deciphering 5-fluorouracil mediated molecular mechanisms required for cell death
(Izmir Institute of Technology, 2011) Can, Geylani; Baran, Yusuf
The chemotherapy agent 5-Fluorouracil (5-FU) is an antimetabolite that has been in use to treat several cancers for decades. In cells, it is converted into three distinct fluoro-based nucleotide analogues which interfere with DNA-synthesis and repair leading to impairment of the genome and, eventually apoptotic cell death. Current knowledge also state that 5-FU induced damage is signaling through a p53-dependent induction of death inducing complex (DISC) formation and further caspase-8 activation in certain cell types and members of the TNF-receptor family has been proposes to be required for the process. Here, we introduce calcium (Ca2+) as a messenger for p53 activation in the cellular response triggered by 5-FU. Using a combination of pharmacological and genetic approaches, we show that treatment of cultured colon carcinoma cells stimulates entry of extracellular Ca2+ through L-type plasma membrane channels and that this event direct posttranslational phosphorylation of at least two specific p53 serine residues (ser15 and ser33) by means of Calmodulin (CaM) activity. Obstructing this pathway by the Ca2+-chelator BAPTA or by two different inhibitors of CaM efficiently blocks 5-FU-induced cell death. The fact that a widely used therapeutic drug, such as 5-FU, is signaling by these means could provide new therapeutic intervention points, or specify new combinatorial treatment regimes.
Citation Count: 35
Imatinib induces autophagy through BECLIN-1 and ATG5 genes in chronic myeloid leukemia cells
(Taylor & Francis Ltd, 2011) Can, Geylani; Ekiz, Huseyin Atakan; Baran, Yusuf; Baran, Yusuf
Imatinib is a chemotherapeutic drug used for the treatment of chronic myeloid leukemia (CML). Recent data showed imatinib-induced cell death in various types of cancers. Autophagy is the physiological process in which cellular components are broken down by the lysosomal activation. In this study, we aimed to examine the effects of imatinib on autophagy in addition to apoptosis in CML cells. Results suggested that imatinib induces autophagy in CML cells through inducing over-expression of BECLIN-1 and ATG5 genes with the statistical significance. Our results demonstrated that autophagy might be involved in imatinib-induced cell death.
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: 24
Role of autophagy in the progression and suppression of leukemias
(Elsevier Science inc, 2012) Ekiz, Huseyin Atakan; Can, Geylani; Baran, Yusuf; Baran, Yusuf
Autophagy is a physiological process in which cellular components are degraded by the lysosomal machinery. Thereby, organelles are recycled and monomers are produced in order to maintain energy production. Current studies indicate autophagy might suppress or augment survival of cancer cells. Therefore, by elucidating the role of autophagy in cancer pathogenesis, novel therapeutic intervention points may be revealed. Leukemia therapy has advanced in recent years; but a definitive cure is still lacking. Since autophagy often is deregulated in this particular type of cancer, it is clear that future findings will have clinical implications. This review will discuss the current knowledge of autophagy in blood cancers. (C) 2011 Elsevier Ireland Ltd. All rights reserved.