Molecular Biology and Genetics / Moleküler Biyoloji ve Genetik

Permanent URI for this collectionhttps://hdl.handle.net/11147/9

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Scopus Q: search.filters.scopusQuartile.Q3Subject: search.filters.subject.Drug resistance

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  • Article
    Citation - WoS: 49
    Citation - Scopus: 50
    Targeting glucosylceramide synthase sensitizes imatinib-resistant chronic myeloid leukemia cells via endogenous ceramide accumulation
    (Springer Verlag, 2011) Baran, Yusuf; Bielawski, Jacek; Gündüz, Ufuk; Öğretmen, Besim
    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.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 7
    Nilotinib Significantly Induces Apoptosis in Imatinib Resistant K562 Cells With Wild-Type Bcr-Abl, as Effectively as in Parental Sensitive Counterparts
    (Taylor and Francis Ltd., 2010) Ekiz, Hüseyin Atakan; Can, Geylani; Gündüz, Ufuk; 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. © 2010 W. S. Maney & Son Ltd.