Turkish Journal of Hematology Volume: 35 - Issue: 4

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RESEARCH ARTICLEDOI: 10.4274/tjh.2018.0106Turk J Hematol 2018;35:260-264Tendency of K562 Chronic Myeloid Leukemia Cells Towards CellReprogrammingK562 Kronik Myeloid Lösemi Hücrelerinin Yeniden Hücre Programlanmasına YatkınlığıAçelya Yılmazer AktunaAnkara University Faculty of Engineering, Department of Biomedical Engineering, Ankara, TurkeyAbstractObjective: Cancer cell reprogramming is a potential tool to studycancer progression, disease pathology, and drug sensitivity. Prior toperforming cancer reprogramming studies, it is important to evaluatethe stemness predisposition of cells that will be reprogrammed. Weperformed a proof-of-concept study with chronic myeloid leukemiaK562 cells in order to evaluate their tendency for cancer cellreprogramming.Materials and Methods: Expression of reprogramming factors,pluripotency markers, and tumor-suppressor genes was analyzed atgene and protein levels via real-time reverse transcription-polymerasechain reaction and flow cytometry. Human peripheral bloodmononuclear cells (PBMCs) were used as a positive control.Results: K562 cells were shown to express higher levels of most of thereprogramming factors and pluripotency markers. Expression of p53,which is one of the main regulators during the generation of inducedpluripotent stem cells, was found to be lower in K562 cells comparedto PBMCs, whereas the other tumor-suppressor genes showed higherexpression levels.Conclusion: This study suggested that, similar to healthy humanPBMCs, K526 cells could be used in cancer cell reprogramming studies.Generating induced pluripotent stem cells from leukemia cells couldhelp scientists to establish chronic myeloid leukemia models in vitrofor a better understanding of therapy resistance and development ofnovel therapeutic targets.Keywords: Induced pluripotent stem cells, Chronic myeloid leukemia,K562, Disease modeling, Cell reprogrammingÖzAmaç: Kanser hücrelerinin yeniden programlanarak hastalıkmodellerinin oluşturulması, hastalığın ilerleyişini, patolojisini ve ilaçduyarlılığını incelemek için önemli bir teknolojidir. Kanser hücrelerindeyeniden programlama çalışmalarını gerçekleştirmeden önce, hücrelerinprogramlamaya yatkınlığını değerlendirmek önemlidir. Kronik myeloidlösemi K562 hücrelerinin kanser programlama çalışmalarındakullanılabilirliğini göstermek amacıyla bir kavram kanıtı çalışmasıgerçekleştirdik.Gereç ve Yöntemler: Yeniden programlama faktörleri, pluripotensibelirteçleri ve tümör baskılayıcı genlerin ifadeleri, gerçek zamanlıpolimerazzincir reaksiyonu ve akan hücre sitometrisi ile gen veprotein seviyelerinde analiz edildi. Programlama çalışmalarında en çokkullanılan insan periferik kan mononükleer hücreleri (PBMC) pozitifkontrol olarak kullanıldı.Bulgular: K562 hücrelerinin, yeniden programlama faktörlerinive pluripotency belirteçlerini PBMC hücrelerine göre daha yüksekseviyede ifade ettiği gösterilmiştir. Uyarılmış pluripotent kökhücrelerinin oluşumu sırasında ana düzenleyicilerden biri olan p53’ünifadesi, K562 hücrelerinde PBMC’ye kıyasla daha düşük bulunurken,diğer tümör baskılayıcı genler daha yüksek ifade göstermiştir.Sonuç: Bu çalışma, sağlıklı insan PBMC’lerine benzer şekilde, K526hücrelerinin yeniden programlama çalışmalarında kullanılabileceğinigöstermiştir. Lösemi kaynaklı uyarılmış pluripotent kök hücrelerikullanılarak in vitro ortamda hastalık modellerinin üretilmesi, biliminsanlarının ilaç dirençlerini daha iyi anlaması ve yeni tedavi hedeflerigeliştirilmesi için önemli bir araç olacaktır.Anahtar Sözcükler: Uyarılmış pluripotent kök hücreler, Kronikmyeloid lösemi, K562, Hastalık modelleme, Hücre programlama©Copyright 2018 by Turkish Society of HematologyTurkish Journal of Hematology, Published by Galenos Publishing HouseAddress for Correspondence/Yazışma Adresi: Açelya YILMAZER AKTUNA, PhD.,Ankara University Faculty of Engineering, Department of Biomedical Engineering, Ankara, TurkeyE-mail : ayilmazer@ankara.edu.tr ORCID-ID: orcid.org/0000-0003-2712-7450Received/Geliş tarihi: March 19, 2018Accepted/Kabul tarihi: May 21, 2018260
Turk J Hematol 2018;35:260-264Açelya Yılmazer Aktuna, Tendency of K562 CML Cells Towards Cell ReprogrammingIntroductionSince their discovery, induced pluripotent stem cells (iPSCs)have been extensively used to model diseases and test drugsin vitro [1,2,3,4,5,6]. Hematological disorders including chronicmyeloid leukemia (CML) have been modeled by various researchgroups [4,7,8]. iPSCs capture the genetic alterations present inleukemia cells and their differentiation ability helps scientists tounderstand disease progression and therapy resistance.In one of the first such studies, the CML cell line KBM7 wasreprogrammed towards pluripotency via retroviral vectorscarrying OKSM (Oct3/4, Klf-4, Sox-2, c-Myc) factors [9].Unlike the untreated cells, the reprogrammed group showedresistance to the chemotherapeutic agent imatinib, which isan inhibitor of the BCR-ABL oncogene. It was hypothesizedthat the therapeutic agent imatinib targets cells in a specificepigenetic differentiated cell state, which can contribute toits inability to fully eradicate disease in CML patients [10].Later, Bedel et al. [11] reported that when CD34 BCR-ABL+ cellsfrom CML patients were reprogrammed, CML-iPSCs lost theirBCR-ABL dependency and became resistant to tyrosine kinaseinhibitor therapy. The authors suggested that CML-iPSCs canbe used to study mechanisms by which leukemic stem cellssurvive to therapy and are a promising tool for testing andscreening new therapeutic targets reducing leukemic stemcell survival [11]. In another CML study, again with the useof retroviral vectors, iPSCs were generated from primaryCML patients’ cells. Although CML-iPSCs were resistant tothe chemotherapeutic agent imatinib, CML-iPSC-derivedhematopoietic cells recovered sensitivity to the drug [12]. Inanother study, whole-genome sequencing of CML-derivediPSCs revealed genocopying of highly mutated primaryleukemic cells, which were used to understand the selectivegrowth under tyrosine kinase inhibitor therapies [13]. In2015, iPSCs were used to identify the leukemia stem cellsfor primitive CML by Suknuntha et al. [14]. Due to the rarityof leukemia stem cells within the primitive hematopoieticcell compartment, it is difficult to study their contribution.By the generation of CML-iPSCs, the authors discoveredolfactomedin 4 as a novel factor that contributes to thesurvival and growth of somatic lin(-)CD34(+) cells from thebone marrow of patients with CML in the chronic phase, butnot primitive hematopoietic cells from normal bone marrow[14]. These contradictory results show that more work isneeded to model CML. However, as in the reprogrammingof healthy cells, there are various factors affectingreprogramming efficiency, and for this reason, these factorsshould be first determined for leukemia in order to modelsuch diseases in vitro.As can be seen from the above studies, reprogramming cancercells is a potential tool to study cancer progression, diseasepathology, and drug sensitivity. Prior to performing cancerreprogramming studies, it is important to evaluate the stemnesspredisposition of cells that will be reprogrammed [4]. Here, weperformed a proof-of-concept study with K562 cells in orderto evaluate their tendency for cancer cell reprogramming. Weanalyzed the endogenous expression of reprogramming andpluripotency factors that are known to be important factorsfor cell reprogramming. Furthermore, it is well known thatthe expression of tumor-suppressor genes also determinesreprogramming efficiency [15]. Therefore, the levels ofimportant tumor-suppressor genes were identified in K562 cells.Materials and MethodsCell CultureHuman CML cell line K562 and human peripheral bloodmononuclear cells (PBMCs) were obtained from ATCC and Lonza,respectively. Cells were cultured in RPMI 1640 supplementedwith 10% fetal bovine serum, 50 U/mL penicillin, 50 µg/mLstreptomycin, and 1% L‐glutamine at 37 °C in 5% CO 2.RNA Extraction and Quantitative Real-Time PCR (qRT-PCR)Cells (1x10 6 cells) were collected and RNA was extracted withthe Macherey-Nagel RNA isolation kit. cDNA synthesis from 1 µgof RNA sample was performed with the iScript cDNA synthesiskit (Bio-Rad) according to the manufacturer’s instructions. Twomicroliters of each cDNA sample were used to perform real-timequantitative reverse transcription-polymerase chain reaction(qRT-PCR) reactions with iQ SYBR Green SuperMix (Bio-Rad).Samples were run on the CFX-96 Connect Real-Time System(Bio-Rad) with the following protocol: 95 °C for 3 min, 1 cycle;95 °C for 10 s and 60 °C for 30 s, repeated for 40 cycles. GAPDHwas used as a reference gene and gene expression levels forOCT3/4, SOX2, KLF4, CMYC, NANOG, REX, CRIPTO, P53, P21, P16,and PRB were normalized to PBMCs.Flow Cytometry AnalysisCells (1x10 6 cells) were collected by centrifugation, washedwith ice-cold methanol for fixation, and then permeabilizedwith 0.1% Triton-X100 containing 2% bovine serum albuminphosphatebuffered saline (PBS). Following washing with PBS,cells were stained with rabbit anti-Oct3/4, rabbit anti-Nanog, ormouse anti-p53 antibodies. Anti-rabbit-AF543 and anti-mouse-AF488 were used as secondary antibodies. Cells were analyzedwith a BD Accuri Plus Flow Cytometer (BD). For 10,000 events,percentages of positive populations were determined by usingBD Accuri Plus software (BD).Statistical AnalysisTriplicates containing required amounts of cells were usedduring analyses. Delta Ct values were used for the statisticalanalysis of RT-PCR results. Statistical analysis was performed261
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AUTHOR INDEX 201835 th Volume Index
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AUTHOR INDEX 2018Olga Meltem Akay..
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SUBJECT INDEX 2018Gluteal lymphoma
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