Cetin Timur

Deregulated WNT signaling in childhood T-cell acute lymphoblastic leukemia

WNT signaling has been implicated in the regulation of hematopoietic stem cells and plays an important role during T-cell development in thymus. Here we investigated WNT pathway activation in childhood T-cell acute lymphoblastic leukemia (T-ALL) patients. To evaluate the potential role of WNT signaling in T-cell leukomogenesis, we performed expression analysis of key components of WNT pathway. More than 85% of the childhood T-ALL patients showed upregulated β-catenin expression at the protein level compared with normal human thymocytes. The impact of this upregulation was reflected in high expression of known target genes (AXIN2, c-MYC, TCF1 and LEF). Especially AXIN2, the universal target gene of WNT pathway, was upregulated at both mRNA and protein levels in ∼40% of the patients. When β-CATENIN gene was silenced by small interfering RNA, the cancer cells showed higher rates of apoptosis. These results demonstrate that abnormal WNT signaling activation occurs in a significant fraction of human T-ALL cases independent of known T-ALL risk factors. We conclude that deregulated WNT signaling is a novel oncogenic event in childhood T-ALL.

Prognostic significance of NOTCH1 and FBXW7 mutations in pediatric T-ALL.

The NOTCH signaling pathway plays important role in the development of multicellular organisms, as it regulates cell proliferation, survival, and differentiation. In adults, it is essential for the T- or B-lymphocyte lineage commitment. NOTCH1 and FBXW7 mutations both lead the activation of the NOTCH1 pathway and are found in the majority of T-ALL patients. In this study, the mutation analysis of NOTCH1 and FBXW7 genes was performed in 87 pediatric T-ALLs who were treated on the ALL-BFM protocols. In 19 patients (22%), activating NOTCH1 mutations were observed either in the heterodimerization domain or in the PEST domain and 7 cases (10%) demonstrated FBXW7 mutations (2 cases had both NOTCH1 and FBXW7 mutations). We also analyzed the relationship of the mutation data between the clinical and biological data of the patients. NOTCH1 and FBXW7, NOTCH1 alone were found correlated with lower initial leucocyte counts which was independent from the sex and T- cell immunophenotype. However, NOTCH1 and FBXW7 mutations were not predictive of outcome in the overall cohort of pediatric T-ALLs.

Prognostic significance of the TEL-AML1 fusion gene in pediatric acute lymphoblastic leukemia in Turkey

Purpose The t(12;21) translocation is the most common reciprocal chromosomal rearrangement in pediatric acute lymphoblastic leukemia (ALL). This translocation fuses two genes, TEL and AML1, and results in the production of the TEL-AML1 fusion protein. The authors investigated the incidence and prognostic significance of the TEL-AML1 fusion gene in patients with ALL in Turkey. Methods The authors analyzed 219 children with ALL using the reverse transcription–polymerase chain reaction. Results The TEL-AML1 fusion transcript was detected in 20.1% (44/219) of newly diagnosed children with ALL. TEL-AML1-positive patients had precursor B-cell ALL and were 3 to 10 years old at diagnosis. TEL-AML1-positive patients had a significantly lower rate of relapse compared with TEL-AML1-negative patients. TEL-AML1-positive patients have a higher overall survival rate than TEL-AML1-negative patients. Conclusions These data support that the presence of TEL-AML1 at diagnosis is an independent favorable prognostic indicator in patients with ALL in Turkey.

Factor 8 (F8) gene mutation profile of Turkish hemophilia A patients with inhibitors.

Factor VIII (FVIII) replacement therapy is ineffective in hemophilia A patients who develop alloantibodies (inhibitors) against FVIII. The type of factor 8 (F8) gene mutation, genes in the major histocompatibility complex loci, and also polymorphisms in IL-10 and tumor necrosis factor-α are the major predisposing factors for inhibitor formation. The present study was initiated to reveal the F8 gene mutation profile of 30 severely affected high-responder patients with inhibitor levels of more than 5 Bethesda U (BU)/ml and four low-responder patients with inhibitors less than 5 BU/ml. Southern blot and PCR analysis were performed to detect intron 22 and intron 1 inversions, respectively. Point mutations were screened by DNA sequence analysis of all coding regions, intron/exon boundaries, promoter and 3′ UTR regions of the F8 gene. The prevalent mutation was the intron 22 inversion among the high-responder patients followed by large deletions, small deletions, and nonsense mutations. Only one missense and one splicing error mutation was seen. Among the low-responder patients, three single nucleotide deletions and one intron 22 inversion were found. All mutation types detected were in agreement with the severe hemophilia A phenotype, most likely leading to a deficiency of and predisposition to the development of alloantibodies against FVIII. It is seen that Turkish hemophilia A patients with major molecular defects have a higher possibility of developing inhibitors.

A Possible Role for WNT5A Hypermethylation in Pediatric Acute Lymphoblastic Leukemia.

Objective: WNT5A is one of the most studied noncanonical WNT ligands and is shown to be deregulated in different tumor types. Our aim was to clarify whether hypermethylation might be the cause of low WNT5A mRNA levels and whether we could restore this downregulation by reversing the event. Materials and Methods: The expression of WNT5A mRNA was studied in a large acute lymphoblastic leukemia (ALL) patient group (n=86) by quantitative real-time PCR. The methylation status was detected by methylation-specific PCR (MSPCR) and bisulphate sequencing. In order to determine whether methylation has a direct effect on WNT5A expression, disease-representative cell lines were treated by 5’-aza-20-deoxycytidine. Results: Here we designed a validation experiment of the WNT5A gene, which was previously examined and found to be differentially expressed by microarray study in 31 T-cell ALL patients. The expression levels were confirmed by quantitative real-time PCR and the expression levels were significantly lower in T-cell ALL patients than in control thymic subsets (p=0.007). MSPCR revealed that 86% of the patients were hypermethylated in the WNT5A promoter region. Jurkat and RPMI cell lines were treated with 5’-aza-20-deoxycytidine and WNT5A mRNA expression was restored after treatment. Conclusion: According to our results, WNT5A hypermethylation does occur in ALL patients and it has a direct effect on mRNA expression. Our findings show that epigenetic changes of WNT signaling can play a role in ALL pathogenesis and reversing methylation might be useful as a possible treatment of leukemia.

Rare coagulation disorders: a retrospective analysis of 156 patients in Turkey.

Objective: To retrospectively evaluate the clinical findings, laboratory data, management, and outcome in a group ofTurkish children diagnosed with rare coagulation deficiencies (RCDs) between January 1999 and June 2009. Material and Methods: The Turkish Society of Pediatric Hematology-Hemophilia-Thrombosis-Hemostasissubcommittee designed a Microsoft Excel-based questionnaire for standardized data collection and sent it to participatinginstitutions. Results: In total, 156 patients from 12 pediatric referral centers were included in the study. The cost common RCDswere as follows: FVII (n = 53 [34%]), FV (n = 24 [15.4%]), and FX (n = 23 [14.7%]) deficiency. The most common initialfinding in the patients was epistaxis, followed by ecchymosis, and gingival bleeding. Conclusion: Initial symptoms were mucosal bleeding, and fresh frozen plasma (FFP) and tranexamic acid werethe most commonly used treatments. We think that prophylactic treatment used for hemophilia patients should beconsidered as an initial therapeutic option for patients with rare factor deficiencies and a severe clinical course, and forthose with a factor deficiency that can lead to severe bleeding.

Seroconversion Status After Single Dose and Double Doses of Varicella Vaccination in Children With Leukemia

Although varicella is a benign self-limiting disease in healthy children, it can be fatal when it occurs in immunocompromised hosts. Despite that immunosuppressed children are suggested to require 2 doses of vaccine to achieve seroconversion, conflicting results are reported in the literature. The aim of this study was to investigate the seroconversion status and mean antibody titers at first year after single dose and double doses of varicella vaccination in acute lymphoblastic leukemia patients. Patients with leukemia in remission for at least 1 year who were seronegative for varicella-zoster virus immunoglobulin G (IgG) were vaccinated. Titers above the cutoff level (0.65) were accepted as seroconversion. Seventeen patients were vaccinated with single dose whereas 24 patients were vaccinated with double doses. Mean prevaccination antibody titers were 0.56 ± 0.05 in patients with single dose and 0.51 ± 0.08 in patients with double doses (P > .05, Student t test). The mean antibody titers at first year were 0.61 ± 0.05 in patients with single-dose vaccination (P > .05, Wilcoxon signed-rank test) and 1.48 ± 0.04 in patients with double doses (P < .001, Wilcoxon signed-rank test). Seroconversion after single-dose vaccination was achieved in 29% of patients (n = 5/17) and in 75% of patients with double doses (n = 18/24) at first year (P = .004, chi-square test). These results suggest that seroconversion after single-dose vaccination might not persist at first year in malignancy patients. Double doses should be applied in order to provide long-term seroconversion.

Frequency of Pericardial Effusion in Childhood Acute Lymphoblastic Leukemia and Clinical Features of These Patients

In this study, we aimed to determine the frequency of pericardial effusion (PE) in children diagnosed with acute lymphoblastic leukemia (ALL). Clinical features of patients with effusion were evaluated. For this purpose, we reviewed the medical records of ALL patients who had pretherapy echocardiograms. A total of 90 patients aged between 1.8 and 16.3 years were analyzed retrospectively. In 23 of 90 (25.6%) patients, PE was detected at initial diagnosis. The age of patients with PE ranged between 1.8 and 14.8 years (mean 5.05 ± 3.77 years). The female/male ratio was 9/14. Six (26.1%) patients were T-lineage and 17 (73.9%) were B-lineage ALL. Nine (39%) patients were in standard risk group, 13 (57%) were in median risk group, 1 (4%) patient was in high-risk group. Mean initial white blood cell count was 40.756 ± 38.653/mm3 (range 23.000–130.000/mm3). Mean initial hemoglobin count was 7.3 ± 1.39 gr/dL (range 5.5–10.1 gr/dL), mean initial platelet count was 35.200 ± 26.300/mm3 (range 4.000–118.000 mm3). Size of effusions was between 2 and 6 mm (mean size 3.3 ± 1.8 mm). All patients had normal left ventricular systolic function. In 87% of patients, effusions disappeared in the first 7 days and, in 13%, disappeared between 8th and 15th days of chemotherapy. None of the patients required pericardiocentesis. Cardiac dysfunction did not occur among any of these patients during chemotherapy. In conclusion, PE is not frequent in childhood ALL. It usually does not cause cardiac impairment. It responds to treatment of leukemia.

Upregulation of T-Cell-Specific Transcription Factor Expression in Pediatric T-Cell Acute Lymphoblastic Leukemia (T-ALL).

Objective: T-cell acute lymphoblastic leukemia (T-ALL) is associated with recurrent chromosomal aberrations andabnormal ectopic gene expression during T-cell development. In order to gain insight into the pathogenesis of T-ALLthis study aimed to measure the level of expression of 7 T-cell oncogenes (LMO2, LYL1, TAL1, TLX1, TLX3, BMI1, andCALM-AF10) in pediatric T-ALL patients Material and Methods: LMO2, LYL1, TLX1, TLX3, BMI1, TAL1, and CALM-AF10 expression was measured usingquantitative real-time PCR in 43 pediatric T-ALL patients. Results: A high level of expression of LMO2, LYL1, TAL1, and BMI1 genes was observed in a large group of T-ALL.Several gene expression signatures indicative of leukemic arrest at specific stages of normal thymocyte development(LYL1 and LMO2) were highly expressed during the cortical and mature stages of T-cell development. Furthermore,upregulated TAL1 and BMI1 expression was observed in all phenotypic subgroups. In all, 6 of the patients had TLX1and TLX3 proto-oncogene expression, which does not occur in normal cells, and none of the patients had CALM-AF10fusion gene transcription. Expression of LYL1 alone and LMO2-LYL1 co-expression were associated with mediastinalinvolvement; however, high-level oncogene expression was not predictive of outcome in the present pediatric T-ALLpatient group, but there was a trend towards a poor prognostic impact of TAL1 and/or LMO2 and/or LYL1 protooncogeneexpression. Conclusion: Poor prognostic impact of TAL1 and/or LMO2 and/or LYL1 proto-oncogene expression indicate the needfor extensive study on oncogenic rearrangement and immunophenotypic markers in T-ALL, and their relationship totreatment outcome. Conflict of interest:None declared.

Evaluation of PAX5 gene in the early stages of leukemic B cells in the childhood B cell acute lymphoblastic leukemia.

B-lineage acute lymphoblastic leukemia (B-ALL) is a common subtype of acute leukemia in children. PAX5 plays a central role in B-cell development and differentiation. In this study, we analyzed PAX5 expression levels, transactivation domain mutations/deletions in B-ALL patients (n=115) and healthy controls (n=10). Relative PAX5 mRNA levels were significantly increased in B-ALL patients (p<0.0001). PAX5 expression was also evaluated in three different B-ALL subgroups (pro B, Common B and Pre B ALL) and showed stage specific expression levels. Pro B (p=0.04) and pre B (p=0.04) patients showed significantly high PAX5 mRNA levels compared to stage specific controls. At least one deletion of exons 7-8 or 9 has been identified in the 41% of the patients. CD34 positivity in patients and presence of large deletions (Δ7/8/9) showed a significant correlation (p=0.05). None of our patients showed PAX5 point mutations, but two previously identified SNPs (rs3780135 and rs35469494) were detected. Our results support that PAX5 is a critical factor in B-ALL development and aberrant PAX5 expression especially at early stages may leads to leukemic transformation.