scholarly journals The Ability of CBFβ-SMMHC to Increase RUNX1 Binding Affinity to Target DNA Correlates with Its Leukemogenic Potential

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1157-1157
Author(s):  
Tao Zhen ◽  
Tongyi Dou ◽  
Yun Chen ◽  
Wei Yang ◽  
Jiansen Jiang ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Negative Staining ◽  
Filament Formation ◽  
Consistent Finding ◽  
E Coli ◽  
Filament Structure ◽  
Target Dna ◽  
Complex Forms

Abstract Inversion of chromosome 16 is a consistent finding in patients with acute myeloid leukemia subtype M4 with eosinophilia (AML M4Eo), which generates a CBFB-MYH11 fusion gene. We recently showed that RUNX1 is indispensable for Cbfb-MYH11-induced leukemogenesis in a mouse model. We found that RUNX1 interacted with CBFβ-SMMHC, the fusion protein encoded by CBFB-MYH11, to directly regulate critical genes for leukemogenesis (Zhen et al., Blood, 2020). However, our current understanding of the interaction between CBFβ-SMMHC and RUNX1 does not provide adequate explanation on how the RUNX1-CBFβ-SMMHC complex forms and how the complex interacts with DNA for leukemogenesis as CBFβ-SMMHC without the RUNX1 high-affinity-binding-domain (CBFβ-SMMHC-ΔHABD) is also able to induce leukemia while CBFβ-SMMHC with mutations in the C-terminal multimerization domain (CBFβ-SMMHC-mDE) is not able to induce leukemia in mice. To address this question, we used RHD domain of RUNX1, CBFβ, CBFβ-SMMHC, CBFβ-SMMHC-ΔHABD and CBFβ-SMMHC-mDE proteins, which were purified from E. coli overexpressing these proteins, to explore how the HABD and DE domains affect the interactions between CBFβ-SMMHC, RHD and RUNX1-target DNA Bio-Layer Interferometry (BLI) and negative staining. As expected, deletion of the HABD domain significantly reduced CBFβ-SMMHC's binding affinity to RHD by BLI assay. Interestingly, differences in binding affinity between RHD and different versions of CBFβ-SMMHC did not correlate with their leukemogenic capability. On the other hand, the binding affinity between RHD and its target oligo was more significantly enhanced by CBFβ-SMMHC and CBFβ-SMMHC-ΔHABD that can induce leukemia than CBFβ-SMMHC-DE, which cannot. We also found that both CBFβ-SMMHC and CBFβ-SMMHC-ΔHABD, but not CBFβ-SMMHC-mDE, could form a filament structure by negative staining, suggesting the filament formation ability is important for leukemogenesis by CBFβ-SMMHC. In addition, RHD reduces filament formation by CBFβ-SMMHC, which was overcome when target oligo was added. In contrast, RHD could not inhibit filament formation by CBFβ-SMMHC-ΔHABD, suggesting that HABD interaction is required for RHD to disrupt filament formation by CBFβ-SMMHC. Overall, we found that leukemogenic capability of CBFβ-SMMHC correlates with its ability to enhance binding between RHD and its target DNA and to form multimerized filaments. The results also suggest that HABD and DE domains of CBFβ-SMMHC are required for the formation of the RUNX1-CBFβ-SMMHC complex with higher binding affinity to target DNA. Disclosures No relevant conflicts of interest to declare.

scholarly journals Lowering DNA binding affinity of SssI DNA methyltransferase does not enhance the specificity of targeted DNA methylation in E. coli

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Krystyna Ślaska-Kiss ◽  
Nikolett Zsibrita ◽  
Mihály Koncz ◽  
Pál Albert ◽  
Ákos Csábrádi ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Dna Binding ◽  
Binding Affinity ◽  
Dna Methyltransferase ◽  
Restriction Enzymes ◽  
Dna Binding Protein ◽  
E Coli ◽  
Dna Binding Affinity ◽  
Higher Eukaryotes

AbstractTargeted DNA methylation is a technique that aims to methylate cytosines in selected genomic loci. In the most widely used approach a CG-specific DNA methyltransferase (MTase) is fused to a sequence specific DNA binding protein, which binds in the vicinity of the targeted CG site(s). Although the technique has high potential for studying the role of DNA methylation in higher eukaryotes, its usefulness is hampered by insufficient methylation specificity. One of the approaches proposed to suppress methylation at unwanted sites is to use MTase variants with reduced DNA binding affinity. In this work we investigated how methylation specificity of chimeric MTases containing variants of the CG-specific prokaryotic MTase M.SssI fused to zinc finger or dCas9 targeting domains is influenced by mutations affecting catalytic activity and/or DNA binding affinity of the MTase domain. Specificity of targeted DNA methylation was assayed in E. coli harboring a plasmid with the target site. Digestions of the isolated plasmids with methylation sensitive restriction enzymes revealed that specificity of targeted DNA methylation was dependent on the activity but not on the DNA binding affinity of the MTase. These results have implications for the design of strategies of targeted DNA methylation.

Filament Formation by Slime Mould Myosin Isolated at Low Ionic Strength

1974 ◽  
Vol 15 (1) ◽  
pp. 113-129
Author(s):  
H. HINSSEN ◽  
J. D'HAESE
Keyword(s):  
Ionic Strength ◽  
Striated Muscle ◽  
Divalent Cations ◽  
Filament Formation ◽  
Selective Precipitation ◽  
Slime Mould ◽  
Preparation Conditions ◽  
Filament Structure ◽  
Low Ionic Strength

Myosin was isolated and purified from plasmodia of the slime mould Physarum polycephalum by a new method. This method is based on actomyosin extraction at low ionic strength after extensive washing, followed by the selective precipitation of myosin at pH 6.1 under relaxing conditions. The yield of myosin was 3-5 times higher than reported for other methods. In contrast to earlier studies a remarkably strong tendency to filament formation was found for slime mould myosin, probably due to a better preservation of some structural properties during preparation. Conditions were worked out under which numerous filaments up to 4 µm in length can be produced. It was established that not only a gradual decrease of ionic strength may influence filament formation, but also pH, ATP concentration and the presence of divalent cations. Compared to the current filament models a difference exists in the structure of the filaments. No central bare zone can be found, and thus, they lack an apparent bipolarity. Along the entire filament there are lateral projections representing the head portion of myosin molecules. A clear periodicity with an axial repeat of about 14 nm was observed, indicating a highly ordered arrangement of these projections. In this paper it is shown for the first time that myosin from one of the primitive motile systems is able to form aggregates of high structural order, indicating that the contraction of non-muscular actomyosin systems is not necessarily effected with oligomeric or randomly aggregated myosin. The possible role of myosin aggregation in vivo and the similarity of filament structure to that recently reported for myosin from vertebrate smooth muscle and striated muscle are discussed.

scholarly journals External Guide Sequences Targeting the aac(6′)-Ib mRNA Induce Inhibition of Amikacin Resistance

2007 ◽  
Vol 51 (6) ◽  
pp. 1918-1925 ◽  
Author(s):  
Alfonso J. C. Soler Bistué ◽  
Hongphuc Ha ◽  
Renee Sarno ◽  
Michelle Don ◽  
Angeles Zorreguieta ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Antisense Oligonucleotides ◽  
Rnase P ◽  
E Coli ◽  
The World ◽  
Guide Sequence ◽  
Mrna Binding ◽  
Target Rna ◽  
External Guide Sequence

ABSTRACT The dissemination of AAC(6′)-I-type acetyltransferases have rendered amikacin and other aminoglycosides all but useless in some parts of the world. Antisense technologies could be an alternative to extend the life of these antibiotics. External guide sequences are short antisense oligoribonucleotides that induce RNase P-mediated cleavage of a target RNA by forming a precursor tRNA-like complex. Thirteen-nucleotide external guide sequences complementary to locations within five regions accessible for interaction with antisense oligonucleotides in the mRNA that encodes AAC(6′)-Ib were analyzed. While small variations in the location targeted by different external guide sequences resulted in big changes in efficiency of binding to native aac(6′)-Ib mRNA, most of them induced high levels of RNase P-mediated cleavage in vitro. Recombinant plasmids coding for selected external guide sequences were introduced into Escherichia coli harboring aac(6′)-Ib, and the transformant strains were tested to determine their resistance to amikacin. The two external guide sequences that showed the strongest binding efficiency to the mRNA in vitro, EGSC3 and EGSA2, interfered with expression of the resistance phenotype at different degrees. Growth curve experiments showed that E. coli cells harboring a plasmid coding for EGSC3, the external guide sequence with the highest mRNA binding affinity in vitro, did not grow for at least 300 min in the presence of 15 μg of amikacin/ml. EGSA2, which had a lower mRNA-binding affinity in vitro than EGSC3, inhibited the expression of amikacin resistance at a lesser level; growth of E. coli harboring a plasmid coding for EGSA2, in the presence of 15 μg of amikacin/ml was undetectable for 200 min but reached an optical density at 600 nm of 0.5 after 5 h of incubation. Our results indicate that the use of external guide sequences could be a viable strategy to preserve the efficacy of amikacin.

Immunogenicity Evaluation of Chimeric Subunit Vaccine Comprising Adhesion Coli Surface Antigens from Enterotoxigenic Escherichia coli

2019 ◽  
Vol 29 (1-6) ◽  
pp. 91-100
Author(s):  
Dorna Khoobbakht ◽  
Shohreh Zare Karizi ◽  
Mohammad Javad  Motamedi ◽  
Rouhollah Kazemi ◽  
Pooneh Roghanian ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Epithelial Cells ◽  
Subunit Vaccine ◽  
Fusion Gene ◽  
Intestinal Epithelial Cells ◽  
High Titer ◽  
Chimeric Protein ◽  
Amino Acid Sequences ◽  
Intestinal Epithelial ◽  
E Coli

Enterotoxigenic <i>Escherichia coli</i> (ETEC) is the most common agent of diarrhea morbidity in developing countries. ETEC adheres to host intestinal epithelial cells via various colonization factors. The CooD and CotD proteins play a significant role in bacteria binding to the intestinal epithelial cells as adhesin tip subunits of CS1 and CS2 pili. The purpose here was to design a new construction containing <i>cooD</i> and <i>cotD</i> genes and use several types of bioinformatics software to predict the structural and immunological properties of the designed antigen. The fusion gene was synthesized with codon bias of <i>E. coli</i> in order to increase the expression level of the protein. The amino acid sequences, protein structure, and immunogenicity properties of potential antigens were analyzed in silico. The chimeric protein was expressed in <i>E. coli</i>BL21 (DE3). The antigenicity of the recombinant proteins was verified by Western blotting and ELISA. In order to assess the induced immunity, the immunized mice were challenged with wild-type ETEC by an intraperitoneal route. Immunological analyses showed the production of a high titer of IgG serum with no sign of serum-mucosal IgA antibody response. The result of the challenge assay showed that 30% of immunized mice survived. The results of this study showed that CooD-CotD recombinant protein can stimulate immunity against ETEC. The designed chimera could be a prototype for the subunit vaccine, which is worthy of further consideration.

Cooperation of MLL/AF10(OM-LZ) with K-Ras Mutation Induced Myeloid Sarcoma in a Mouse Bone Marrow Transplantation Model.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1964-1964
Author(s):  
Jen-Fen Fu ◽  
Lee-Yung Shih
Keyword(s):  
Bone Marrow ◽  
Cell Lines ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Flow Cytometric Analysis ◽  
Myeloid Sarcoma ◽  
Mouse Bone Marrow ◽  
Myeloproliferative Disease ◽  
Multiple Tumor

Abstract Abstract 1964 Poster Board I-987 We analyzed genetic mutations in a large cohort of AML patients and found that two of the five patients with MLL/AF10 and N-/K-RAS mutations had cutaneous tumors (myeloid sarcomas). To study the cooperative role of MLL/AF10 and N-/K-RAS in the formation of myeloid sarcoma, we established two cell lines by retroviral transduction of MLL/AF10(OM-LZ) and K-RASG12C into GFP-B6 mouse bone marrow cells. Flow cytometric analysis revealed that the cells with MLL/AF10(OM-LZ) and K-RASG12C showed a decreased Mac-1 and CD115 expression when compared with the cells with a single MLL/AF10(OM-LZ) mutation. Microarray and RT-PCR analyses revealed an increased gene expression in Hoxa10 and Meis1, but not Hoxa9. In addition, the phagocytosis related genes, Cybb and Lyz were decreased in the cells harboring MLL/AF10(OM-LZ) and K-RASG12C. These results suggested that cooperation of MLL/AF10(OM-LZ) and K-RASG12C mutations blocked the cells in a more primitive hematopoietic stage. When the two cell lines were intra-peritoneally injected into B6 mice, the mice developed myeloproliferative disease-like myeloid leukemia as that of the mice transplanted with cells carrying a single MLL/AF10(OM-LZ) fusion gene. The median survival time were 33±4.2 and 31.6±5.1 days, respectively, which were shorter than that of the mice transplanted with cells carrying a single MLL/AF10(OM-LZ) fusion gene (49.8±5.0 days). We found that the majority (84%) of mice transplanted with cells harboring both MLL/AF10(OM-LZ) and K-RASG12C mutations formed multiple tumor masses involving gastrointestinal tract, kidney, peritoneum, paraspinal soft tissue, and/or skin. Cytological examination from the imprint smears of tumor masses showed massive infiltrates of leukemia blastic cells. Immunohistochemical stains of the paraffin-fixed histological sections of tumor masses were positive for GFP, confirmed that the tumor cells were generated from the transplanted cell lines. We have established a mouse model which can be used for further study of the myeloid sarcoma formation. Disclosures: No relevant conflicts of interest to declare.

Transforming and Tumorogenic Activity of JAK2 by Fusion to BCR: Molecular Mechanisms of Action of a Novel BCR-JAK2 Tyrosin-Kinase.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4683-4683
Author(s):  
Álvaro Cuesta-Domínguez ◽  
Mara Ortega ◽  
Cristina Ormazabal ◽  
Matilde Santos-Roncero ◽  
Marta Galán-Díez ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Nude Mice ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Lymphoblastic Leukemia ◽  
Chimeric Protein ◽  
Tyrosine Kinase Domain ◽  
Molecular Response

Abstract Abstract 4683 Chromosomal translocations in human tumors frequently produce fusion genes whose chimeric protein products play an essential role in oncogenesis. Recent reports have found a BCR-JAK2 fusion gene in cases of chronic or acute myeloid leukemia, but the protein had not been characterized. We describe a BCR-JAK2 fusion gene by fluorescence in situ hybridization and RT-PCR amplification from bone marrow at diagnosis of a patient with acute lymphoblastic leukemia. After induction therapy, real time PCR showed persistent molecular response correlating with hematological remission maintained up to present. BCR-JAK2 is a 110 KDa chimeric protein containing the BCR oligomerization domain fused to the JAK2 tyrosine-kinase domain. In vitro analysis showed that BCR-JAK2 was constitutively phosphorylated and was located to the cytoplasm. BCR-JAK2 transformed the IL-3-dependent murine hematopoietic cell line Ba/F3 into IL-3 independent growth and induced STAT5b phosphorylation and translocation into the cell nuclei. The treatment with a JAK2 inhibitor abrogated BCR-JAK2 and STAT5b phosphorylation, leading to apoptosis of transformed Ba/F3 cells. To test whether BCR-JAK2 has tumorogenic ability in vivo, we performed experiments with nude mice, in which we injected subcutaneously cells transduced with the control vector and cells expressing BCR-JAK2. Notably, we only obtained tumors in the flank injected with BCR-JAK2 expressing cells, thus confirming the tumorogenic activity of the BCR-JAK2 fusion protein. We conclude that BCR-JAK2 is a new tyrosine-kinase that induces proliferation and cell survival, which can be abrogated by JAK2 inhibitors. In vitro studies demonstrate that BCR-JAK2 displays transforming activity. Moreover, the nude mice model reveals its ability to cause tumors. Disclosures: No relevant conflicts of interest to declare.

The W–x–x–W Motif in the TSR1 of ADAMTS13 Is Important for Its Secretion

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4389-4389
Author(s):  
Jing Ling ◽  
Jian Su ◽  
Zhenni Ma ◽  
Changgeng Ruan
Keyword(s):  
Shear Stress ◽  
Binding Affinity ◽  
Culture Medium ◽  
Stress Condition ◽  
Conflicts Of Interest ◽  
Enzyme Linked Immunosorbent Assay ◽  
High Shear ◽  
High Shear Stress ◽  
Wild Type ◽  
Western Blots

Abstract Abstract 4389 Introduction: The W-x-x-W motif is commonly found in the thrombospondin type 1 repeat (TSR) of various extra cellular proteins called TSR super family proteins, including thrombospondins, ADAMTSs, F-spondin and properdin. The W–x–x–W motif is known to bind with heparin, heparan sulfate proteoglycans, collagen and transforming growth factor-β, suggesting functional significance in cell–cell interaction and/or cellular signaling. However, the function of W-x-x-W in ADAMTS13 is unclear. In this study, we investigated the role of the W-x-x-W motif of ADAMTS13. Materials and Methods: We generated a W-x-x-W mutant (W387A) construct of ADAMTS13, and expressed the mutant and the wild-type constructs in HELA cells. Percentage of the protein secretion was defined as the concentration in the culture medium divided by the concentrations in the culture medium and cell lysates, multiplied by 100%. The binding affinity of the mutant or wild-type ADAMTS13 was investigated by enzyme-linked immunosorbent assay. Measurement of ADAMTS13 proteolytic activity toward von Willebrand factor (VWF) multimers was based on the generation of a dimeric 176-kDa fragment resulting from cleavage of VWF at the Y1605-M1606 bond, under denaturing condition and high shear stress condition, analyzed by Western blots. Results: SDS-PAGE gel analysis showed that the W387A mutant was secreted less efficiently relative to the wild-type construct. As for the binding affinity for the VWF multimer, there was no difference between the wild-type and mutant ADAMTS13. The W387A mutant was less active under denaturing condition; the same result was reproduced when FRETS-VWF73 was used as the substrate. However, under high shear stress condition, the mutant was as efficient as the wild-type ADAMTS13. Conclusions: The W–x–x–W motif is necessary for efficient secretion of ADATMS13. Further studies are needed to determine the contribution of the motif to the VWF cleave activity of ADAMTS13. Disclosures: No relevant conflicts of interest to declare.

Detection of Five Common Fusion Oncogenes in Pakistani Children with Acute Lymphoblastic Leukemia and Their Association with Clinical Pattern and Treatment Outcome

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 5124-5124
Author(s):  
Zafar Iqbal ◽  
Sabir Noreen ◽  
Aleem Aamer ◽  
Awan Tashfeen ◽  
Tahir Naeem ◽  
...  
Keyword(s):  
Treatment Outcome ◽  
Acute Lymphoblastic Leukemia ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Lymphoblastic Leukemia ◽  
White Cell Count ◽  
Total Leukocyte Count ◽  
Age Group ◽  
Response To Chemotherapy ◽  
Pediatric All

Abstract Abstract 5124 Background & Objectives: Acute lymphoblastic leukemia (ALL) is a complex genetic disease involving many fusion oncogenes (FGs) (Xu et al., 2012). The frequency of various FO can vary in different ethnic groups & these FGs have important implications for prognosis & treatment outcome (van-Dongen et al, 1999). Methods: We studied FGs in 101 pediatric ALL patients using Interphase FISH & RT-PCR (van-Dongen et al, 1999), & their association with clinical features & treatment outcome. Results: Five most common FGs i. e. BCR-ABL [t(9;22)], TCF3-PBX1 [t(1;19)], ETV6-RUNX1 [t(12;21)], MLL-AF4 [t(4;11)] & SIL-TAL1 (del 1p32) were found in 89/101 (88. 1%) patients. Frequency of BCR-ABL was 44. 5% (45/101) (Table 1). BCR-ABL positive patients had a significantly lower survival (43. 73 ± 4. 24 weeks) (Figure 1)& higher white cell count as compared to others except patients with MLL-AF4. The highest relapse-free survival (RFS) was documented in ETV6-RUNX1 (14. 167 months) followed closely by those cases in which no gene was detected (13/100). RFS in BCR-ABL, MLL-ASF4, TCF-PBX4 & SIL-TAL1 was less than 10 months (7. 994, 3. 559, 5. 500 & 8. 080 months respectively) (Figure 2 & 3). BCR-ABL: Frequency of occurrence was directly proportional to age (3 less than 2 year age group, 16 in the 2–7 year age group & 26 in the older than 7 group. Total leukocyte count (TLC) was higher when compared to patients with other oncogenes. Organomegaly was not common. BCR-ABL positivity was associated with low remission rates & shortened survival. ETV6-RUNX1: The median age of the patients was 1. 85 years. The gene frequency was highest in patients younger than 2 years. TLC was not very high & patients had a good prognosis. MLL-AF4: 17 patients had MLL-AF4 gene rearrangement with a median age of 9 years. Five patients were younger than 2 years, two between 2 & 7 years, & ten patients were in the 7–15 age group. Majority of our patients were older unlike the usual occurrence where most of the patients are infants. TCF3-PBX1: This FG occurs in around 2% of patients. Only two female patients were diagnosed with this translocation. Both the patients were over 2 years of age. It was associated with an inferior outcome in the context of response to chemotherapy & a higher risk of CNS relapse although small numbers preclude any firm conclusions. SIL-TAL1: Patients were older than 2 years, with the majority falling in the age range 7 to 15 years. The immunophenotype data were available in all SIL-TAL1 patients showing this fusion gene was associated with T-ALL with organomegaly being observed frequently. Discussion & Conclusion: This is the first study from Pakistan correlating molecular markers with disease biology & treatment outcome in pediatric ALL. Our study revealed the highest reported frequency of BCR-ABL FO in pediatric ALL, in consistent with various other reports from Pakistan & rest of the world ((Iqbal & Akhtar, 2007; Faiz et al., 2011; (Gaynon et al., 1997; Iacobucci et al., 2012).) which, consequently, was associated with poor overall survival. The data indicates an immediate need for incorporation of tyrosine kinase inhibitors in the treatment of BCR-ABL+ pediatric ALL in this population & the development of facilities for stem cell transplantation. Disclosures: No relevant conflicts of interest to declare.

Epigenetic Status Of CEBPA Promoter and Expression Of CEBPα Correlates With Molecular Genetic Subtype and CD2 Aberrant Expression In B Cell Precursor ALL

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2573-2573
Author(s):  
Lucie Slamova ◽  
Julia Starkova ◽  
Karel Fiser ◽  
Eva Fronkova ◽  
Leona Rezkova Reznickova ◽  
...  
Keyword(s):  
B Cell ◽  
Early Phase ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Lymphoblastic Leukemia ◽  
Methylation Status ◽  
Fisher Exact Test ◽  
Cell Precursor ◽  
Aberrant Expression ◽  
Mll Gene

Abstract CCAAT/enhancer binding protein alpha (CEBPα) is one of the crucial transcription factors involved in hematopoietic differentiation and leukemogenesis. CEBPα promotes myeloid differentiation by up-regulation of lineage specific genes and by cell proliferation arrest. Epigenetic regulation of CEBPα expression through DNA methylation has been demonstrated in acute myeloid leukemia (AML) (Figueroa et al, Cancer Cell, 2010). However, only limited data are available regarding CEBPA promoter methylation and its expression in B cell precursor acute lymphoblastic leukemia (BCP-ALL). Methylation status of CEBPA promoter (-295 to -593bp upstream of the transcription start site (TSS), 24 CpG dinucleotides) was analyzed by bisulfite sequencing. Five subgroups of BCP-ALLs were analyzed: MLL gene rearranged (n=5), hyperdiploid (n=6), mBCR-ABLpos(n=5), ETV6-RUNX1pos(n=6) and other BCP-ALLs (no hyperdiploidy, MLL gene rearrangement, BCR-ABL or ETV6-RUNX1 fusion gene (“BCP-others”, n=29)). CEBPA promoter was hypermethylated in MLL-rearranged, hyperdiploid and ETV6-RUNX1pos BCP-ALL (5/5, 6/6 and 4/6 respectively). Surprisingly CEBPA promoter was hypomethylated in all mBCR-ABLpos cases (5/5). In subgroup of other BCP-ALLs both hypermethylation (10/29) and hypomethylation of CEBPA promoter (19/29) were detected (Figure 1A). In previous study we found association of CD2 (LFA-2) aberrant expression and switch to the monocytic lineage during the early phase of treatment in BCP-ALLs (Slamova et al, ASH 2012). We were interested if a possible link between hypomethylation of CEBPA promoter correlates with aberrant expression of CD2. There was a significant association between aberrant expression of CD2 antigen and hypomethylation in CEBPA promoter in BCP-others (Fisher exact test, p<0.0001). Interestingly, in the only hypomethylated ETV6-RUNX1pos case we found aberrant CD2 expression on blasts, which is exceptional in ETV6-RUNX1pos ALL. We next asked whether methylation of CEBPA promoter correlates with CEBPα expression. It is generally accepted that promoter hypomethylation is often associated with increased expression of the relevant gene. Our data prove that in general, this holds true also for BCP-ALL. However, in two genetically defined subsets we observed either high expression despite hypermethylation (MLL-rearranged ALL) or low expression despite hypomethylation (mBCR-ABLpos ALL) (Figure 1B). In BCP-others hypomethylation of CEBPA promoter was significantly associated with upregulation of myeloid antigens (CD14 and/or CD33) and downregulation of B cell marker CD19 on blasts during the first weeks of the treatment (Fisher test, p=0.0009). In summary Methylation status of CEBPA promoter correlates with genetic subtypes of BCP-ALL. The notion that hypomethylation leads to overexpression was confirmed in majority of BCP-ALLs, while in mBCR-ABLpos and MLL gene rearranged BCP-ALL it did not follow this pattern. Hypomethylation of CEBPA promoter in BCP- others correlates with CD2 expression on blasts and increased CEBPα gene expression. During the early phase of the treatment in other BCP-ALLs with hypomethylated CEBPA promoter increase of myeloid and decrease of B lymphoid markers on blasts was observed. Supported by: GACR P301/10/1877, GACR P304/12/2214, GAUK 914613, UNCE 204012, NT13462, NT12397- 4, project for conceptual development of research organization (Ministry of Health, CZ) 00064203, the FACS Aria instrument was supported by EU-Prague project CZ.2.16/3.1.00/24022 Disclosures: No relevant conflicts of interest to declare.

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