Molecular Biology and Genetics / Moleküler Biyoloji ve Genetik
Permanent URI for this collectionhttps://hdl.handle.net/11147/9
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Article Citation - WoS: 7Citation - Scopus: 9Genomewide Elucidation of Drug Resistance Mechanisms for Systemically Used Antifungal Drugs Amphotericin B, Caspofungin, and Voriconazole in the Budding Yeast(American Society for Microbiology, 2019) Balkan, Çiğdem; Ercan, İlkcan; Işık, Esin; Akdeniz, Esra Şahin; Balcıoğlu, Orhan; Kodedova, Marie; Koç, AhmetThere are only a few antifungal drugs used systemically in treatment, and invasive fungal infections that are resistant to these drugs are an emerging problem in health care. In this study, we performed a high-copy-number genomic DNA (gDNA) library screening to find and characterize genes that reduce susceptibility to amphotericin B, caspofungin, and voriconazole in Saccharomyces cerevisiae. We identified the PDR16 and PMP3 genes for amphotericin B, the RMD9 and SWH1 genes for caspofungin, and the MRS3 and TRI1 genes for voriconazole. The deletion mutants for PDR16 and PMP3 were drug susceptible, but the other mutants had no apparent susceptibility. Quantitative-PCR analyses suggested that the corresponding drugs upregulated expression of the PDR16, PMP3, SWH1, and MRS3 genes. To further characterize these genes, we also profiled the global expression patterns of the cells after treatment with the antifungals and determined the genes and paths that were up-or downregulated. We also cloned Candida albicans homologs of the PDR16, PMP3, MRS3, and TRI1 genes and expressed them in S. cerevisiae. Heterologous expression of Candida homologs also provided reduced drug susceptibility to the budding yeast cells. Our analyses suggest the involvement of new genes in antifungal drug resistance.Article Citation - WoS: 15Citation - Scopus: 13Environmentally Responsive Dual-Targeting Nanoparticles: Improving Drug Accumulation in Cancer Cells as a Way of Preventing Anticancer Drug Efflux(John Wiley and Sons Inc., 2018) Dağlıoğlu, CenkDrug targeting and stimuli-responsive drug release are 2 active areas of cancer research and hold tremendous potential in the management of cancer drug resistance. In this study, I addressed this issue and focused on the synthesis and characterization of pH-responsive Fe3O4@SiO2(FITC)-BTN/folic acid/DOX multifunctional nanoparticles aiming to increase drug accumulation in malignancies with both dual active targeting and endosomal drug release properties. Dye-doped silica magnetic-fluorescent composite was constructed by a simple coprecipitation of Fe+2/Fe+3 salts followed by sol-gel formation and dual-targeting function was obtained by conjugating folate and biotin moieties on the silica surface of nanoparticles via an esterification reaction. Doxorubicin was then successfully attached on the amine-functionalized nanoparticles using a pH-sensitive Schiff-base formation. The physicochemical characterization of the structure was performed by dynamic light scattering, zeta potential measurement, X-ray diffraction, Fourier transform infrared spectroscopy, electron microscopy techniques, and an in vitro pH-dependent release study. Cellular uptake and cytotoxicity experiments demonstrated an enhanced intracellular delivery and reduction of cancer cell viability in the cervical carcinoma HeLa cell line. Furthermore, proapoptotic studies showed that the nanoparticles increased the apoptotic rates within the same cancer cells. The preliminary cell tests confirm the potential of these multifunctional nanoparticles against the development of drug resistance in cancer cells.Article Citation - WoS: 108Citation - Scopus: 119Sphingosine Kinase-1 and Sphingosine 1-Phosphate Receptor 2 Mediate Bcr-Abl1 Stability and Drug Resistance by Modulation of Protein Phosphatase 2a(American Society of Hematology, 2011) Salas, Arelis; Ponnusamy, Suriyan; Senkal, Can E.; Meyers-Needham, Marisa; Selvam, Shanmugam Panneer; Saddoughi, Sahar A.; Apohan, Elif; Sentelle, R. David; Smith, Charles; Gault, Christopher R.; Obeid, Lina M.; El-Shewy, Hesham M.; Oaks, Joshua; Santhanam, Ramasamy; Marcucci, Guido; Baran, Yusuf; Mahajan, Sandeep; Fernandes, Daniel; Stuart, Robert; Perrotti, Danilo; Öğretmen, BesimThe mechanisms by which sphingosine kinase-1 (SK-1)/sphingosine 1-phosphate (S1P) activation contributes to imatinib resistance in chronic myeloid leukemia (CML) are unknown. We show herein that increased SK-1/S1P enhances Bcr-Abl1 protein stability, through inhibition of its proteasomal degradation in imatinib-resistant K562/IMA-3 and LAMA-4/IMA human CML cells. In fact, Bcr-Abl1 stability was enhanced by ectopic SK-1 expression. Conversely, siRNA-mediated SK-1 knockdown in K562/IMA-3 cells, or its genetic loss in SK-1-/- MEFs, significantly reduced Bcr-Abl1 stability. Regulation of Bcr-Abl1 by SK-1/S1P was dependent on S1P receptor 2 (S1P2) signaling, which prevented Bcr-Abl1 dephosphorylation, and degradation via inhibition of PP2A. Molecular or pharmacologic interference with SK-1/S1P2 restored PP2A-dependent Bcr-Abl1 dephosphorylation, and enhanced imatinib- or nilotinib-induced growth inhibition in primary CD34+ mononuclear cells obtained from chronic phase and blast crisis CML patients, K562/IMA-3 or LAMA4/IMA cells, and 32Dcl3 murine progenitor cells, expressing the wild-type or mutant (Y253H or T315I) Bcr-Abl1 in situ. Accordingly, impaired SK-1/S1P2 signaling enhanced the growth-inhibitory effects of nilotinib against 32D/T315I-Bcr-Abl1-derived mouse allografts. Since SK-1/S1P/S1P2 signaling regulates Bcr-Abl1 stability via modulation of PP2A, inhibition of SK-1/S1P2 axis represents a novel approach to target wild-type- or mutant-Bcr-Abl1 thereby overcoming drug resistance. © 2011 by The American Society of Hematology.Article Citation - WoS: 32Citation - Scopus: 34Therapeutic Applications of Bioactive Sphingolipids in Hematological Malignancies(John Wiley and Sons Inc., 2010) Ekiz, Hüseyin Atakan; Baran, YusufSphingolipids 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 processes. 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. © 2010 UICC.