Emin Kürekçi

DNA methyltransferase expression differs with proliferation in childhood acute lymphoblastic leukemia

DNA methylation is involved in genomic imprinting, tissue and stage specific gene regulation, X chromosome inactivation and especially necessary in normal mammalian development [1]. Methylation of DNA at cytosine base occurs at most CpG islands in the mammalian genome, with exception of CpG islands of gene promoters which are usually unmethylated. Methylation of promoter CpG islands inhibits the activity of the gene by inhibiting the association of some DNA-binding factors with methylated DNA sequences or by silencing transcription via methyl-CpG binding proteins with co-repressors and chromatin modifiers [2]. Cancer is known as a genetic disease, in which epigenetic alterations play important roles. Cancer cells show global genomic hypomethylation, but the CpG islands of the promoters, especially the promoters of the tumour suppressor genes are hypermethylated [3]. Aberrant methylation of CpG islands is a major epigenetic mechanism of gene expression in human cancers. Global hypomethylation is important in tumour formation by different ways which include chromosomal and genomic instability, increased mutation rate and recombination frequency [4]. Hypermethylation of tumour suppressor genes causes gene inactivation, furthermore aberrant DNA methylation facilitates gene mutation, because deamination of 5-methylcytosine leads to the formation of thymine which is not repaired by uracil glycosylases, instead of the formation of uracil by cytosine deamination [5]. Acute lymphoblastic leukemia (ALL), is the most frequent cancer of childhood (25%). The blockage of lymhpoid cell development at any stage, leads to ALL. Chromosomal aberrations as well as epigenetic changes are important in it’s development. E-cadherin, DAP-kinase, p73 and p15 gene promoters are some of the gene promoters that are known to be hypermethylated in childhood ALL [6–8]. DNA methyltransferases (DNMT’s) are the enzymes that methylate DNA. In mammalians, there are five different DNMT’s: DNMT1, DNMT2, DNMT3A, DNMT3B and DNMT3L. All of the DNMT’s, except DNMT3L, are catalitically active. All have a catalytic carboxy terminal and a regulator amino terminal, except DNMT2. The activity of DNMTs are greatly regulated by their amino terminal domain which interacts with other molecules. DNMT2, contains only the catalytic domain and participates scarcely to the formation of DNA methylation pattern although it covalently binds to DNA [9–11]. DNMT1 targets the replication fork, methylates preferentially hemimethylated DNA, and is responsible for the Isik Bokesoy—Retired Professor.

Freezing of Apheresis Platelet Concentrates in 6% Dimethyl Sulfoxide: The First Preliminary Study in Turkey.

Objective: Transfusion of platelet suspensions is an essential part of patient care for certain clinical indications. In this pioneering study in Turkey, we aimed to assess the in vitro hemostatic functions of platelets after cryopreservation. Materials and Methods: Seven units of platelet concentrates were obtained by apheresis. Each apheresis platelet concentrate (APC) was divided into 2 equal volumes and frozen with 6% dimethyl sulfoxide (DMSO). The 14 frozen units of APCs were kept at -80 °C for 1 day. APCs were thawed at 37 °C and diluted either with autologous plasma or 0.9% NaCl. The volume and residual numbers of leukocytes and platelets were tested in both before-freezing and post-thawing periods. Aggregation and thrombin generation tests were used to analyze the in vitro hemostatic functions of platelets. Flow-cytometric analysis was used to assess the presence of frozen treated platelets and their viability. Results: The residual number of leukocytes in both dilution groups was <1x106. The mean platelet recovery rate in the plasma-diluted group (88.1±9.5%) was higher than that in the 0.9% NaCl-diluted group (63±10%). These results were compatible with the European Directorate for the Quality of Medicines quality criteria. Expectedly, there was no aggregation response to platelet aggregation test. The mean thrombin generation potential of post-thaw APCs was higher in the plasma-diluted group (2411 nmol/L per minute) when compared to both the 0.9% NaCl-diluted group (1913 nmol/L per minute) and the before-freezing period (1681 nmol/L per minute). The flow-cytometric analysis results for the viability of APCs after cryopreservation were 94.9% and 96.6% in the plasma and 0.9% NaCl groups, respectively. Conclusion: Cryopreservation of platelets with 6% DMSO and storage at -80 °C increases their shelf life from 7 days to 2 years. Besides the increase in hemostatic functions of platelets, the cryopreservation process also does not affect their viability rates.

Factor V Leiden and Prothrombin 20210A Mutations among Turkish Pediatric Leukemia Patients.

This study was undertaken to determine the prevalence of the Factor V 1691 G-A and PT 20210 G-A mutations in Turkish children with leukemia. We genotyped 135 pediatric leukemia patients with for these mutations. Eleven (8%) of the 135 patients were heterozygous for the FV 1691 G-A mutation. Seven (5,1%) of the patients carried the PT 20210 G-A heterozygous mutation. Of the 135 patients, only three had thrombotic event, none of which had these two mutations, which is common in Turkish population. Our findings revealed a controversial compared to the previous reports, which needs further investigation.

Holotranscobalamin Levels in Children with Helicobacter Pylori Infection

The purpose of this study was to evaluate the association between vitamin B12 levels and Helicobacter Pylori infection and to examine the clinical usefulness of holotranscobalamin (holoTC) measurement in children.

Anticardiolipin Antibodies in Children with Helicobacter pylori Infection.

Anticardiolipin (aCL) antibodies are associated with thrombosis and have an important role in the etiology of diseases such as stroke and myocardial infarction whose etiologies were based on thrombosis. H. pylori has been proposed to be responsible for the pathophysiology of some diseases including stroke, myocardial infarction, thrombosis, and autoimmune diseases. From this point of view, we hypothesized a possible relationship between H. pylori infection and aCL antibodies and initially aimed to determine the prevalence of aCL antibody positivity in children with H. pylori infection.

First Observation of Hemoglobin M Saskatoon (ß63 (E7) His>Tyr(C-T)) in the Iraqi Population

Hemoglobin M Saskatoon (s63 His>Tyr(C-T)) is a rare hemoglobin variant that was first reported in Japan, followed by the US, Indonesia, Algeria, Russia, India, and Germany [1-8]. It was also reported in combination with another variant—Hb Hamilton [9]; however, it has yet to reported in the Turkish population [10,11]. The present report describes the first observation of this variant in an 9-year-old Iraqi boy that presented with fatigue and greyblue discoloration of the distal extremities and mucous membranes since birth. Physical examination showed cyanosis and clubbing of the fingers and toes. Complete blood count, reticulocyte count, liver and renal function tests, and abdominal ultrasound were normal. Echocardiography and angiography showed no abnormality. Blood gas analysis showed an O2 saturation of 91% and a methemoglobin level of 24.5%. Capillary hemoglobin electrophoresis showed hemoglobin M (Iwate or Saskatoon). Family history was unremarkable.

Successful treatment of ICE-rituximab chemotherapy and subsequent bone marrow transplantation in a patient with early-relapse Burkitt leukemia and inverted duplication of 1q.

Although childhood acute lymphoblastic leukemias are of good prognosis than leukemias of adulthood, some chromosomal abnormalities may have negative effects on their prognosis. Inverted duplication (1q) is a chromosomal abnormality with negative effect on outcome of Burkitt leukemia and lymphomas. We report a case of CD20+ Burkitt leukemia with inverted duplication (1q) mutation, who had an early relapse during NHL-BFM 95 treatment. Two courses of ICE-rituximab treatment were administered after relapse and a successful HLA-full match bone marrow transplantation was carried out. He is in follow-up for 18 months without any problem after the bone marrow transplantation. We suggest the usage of ICE protocol combined with rituximab in childhood CD20+ Burkitt leukemia with poor prognostic criteria such as inverted duplication (1q) mutation.

Two new mutations at ERGIC-53 gene in a Turkish family.

Combined factor V and factor VIII deficiency (F5F8D) is a rare autosomal recessive coagulation disorder associated with plasma levels of coagulation factors V and VIII approximately 5% to 30% normal. Combined factor V and factor VIII deficiency is caused by mutations in ERGIC-53 (LMAN1) gene. ERGIC-53 and multiple coagulation factor deficiency 2 (MCFD2) form a protein complex that functions as a cargo receptor transport FV and FVIII from the endoplasmic reticulum to the Golgi. The aim of this study was to determine the mutations of ERGIC-53 (endoplasmic reticulum [ER] to the ER-Golgi intermediate compartment) gene and combined F5F8D in a family. In this study, we analyzed a patient in a Turkish family with combined F5F8D. We found a nonsense mutation of C to T at nucleotide 202 in exon 9, resulting in a transition of arginine to stop codon, and in 1 child, we found a timine deletion in exon 4 in ERGIC-53 gene.

Frequency of thiopurine s-methyltransferase gene variations in turkish children with acute leukemia

Akın DF, Aşlar-Öner D, Kürekçi E, Akar N. Frequency of thiopurine S-methyltransferase gene variations in Turkish children with acute leukemia. Turk J Pediatr 2018; 60: 147-152. In this study we aim to determine the genotype distribution and allele frequencies of common TPMT (*2, *3A, *3B and *3C) polymorphisms in Turkish children with acute leukemia. The study population consisted of 169 patients aged between 1 and 15 years who were admitted to Losante Pediatric Hematology and Children`s Hospital with the diagnosis of acute leukemia. Genotyping of TPMT polymorphisms was screened with real-time PCR using fluorescence melting curve detection analysis. We found that the frequencies of four allelic variants of TPMT are *2 (238 G > C) (0,0%), *3A (460G > A and 719A > G) (1.7%), *3B (460G > A) (1,7%) and *3C (719A > G) (2.4%). Frequency of TPMT alleles increases the efficacy of leukemia treatment. Thus, TPMT genotyping can be useful for optimizing 6-MP therapy.

Screening of single nucleotide polymorphism in CD95 (APO-1/FAS) promoter region (G-1377A) in children with acute leukemia

Background CD95 is a cell surface receptor involved in apoptotic signal transmission. Deregulation of this pathway results in downregulation of apoptosis and subsequent persistence of a malignant clone. A single nucleotide polymorphism resulting in guanine-to-adenine (G>A) transition in the CD95 promoter region (position −1377) is thought to reduce stimulatory protein 1 transcription factor binding and decrease CD95 expression. The purpose of this study is to examine a genetic polymorphism in the core promoter region of CD95 and to evaluate association between its frequency and clinical findings. Patients and methods G-1377A in the CD95 promoter region was genotyped by polymerase chain reaction and restriction endonuclease analysis finally were sequenced by Sanger Sequecing. Results Among 146 patients, CD95 G-1377A (rs2234767) single nucleotide polymorphism carriers frequencies have been identified as 25% (n=37) GA and AA 4% (n=6). This polymorphism of the distribution of the CD95 gene in children with acute leukemia will be a guide for future studies. Conclusion This polymorphism of the distribution of the CD95 gene in children with acute leukemia will be a guide for future studies.