Abnormalities In Acute Myeloid Leukemia Research Articles

Integrative Analysis of the Mutational Landscape of Mouse and Human AML Identifies Functionally Relevant Leukemia Disease Alleles

t(8;21) is the most frequent chromosomal abnormality in acute myeloid leukemia (AML), occurring in 4-12% of adult and 12-30% of pediatric patients. This translocation fuses the N-terminus of AML1 to nearly the entire coding region of ETO, resulting in expression of the fusion protein AML1-ETO. Observations that mice expressing AML1-ETO develop AML only if treated with mutagenic agents have suggested that AML1-ETO requires cooperating disease alleles for leukemogenesis. Consistent with this, t(8;21)+ AML patients harbor multiple genetic abnormalities. Recent exome/genome sequencing studies have expanded the number of known mutations in t(8;21)+ AML patients; however, efforts to distinguish driver from passenger mutations have yielded few cooperative events and the requirements for AML1-ETO leukemogenesis remain largely unknown.To better define the genetic landscape in AML and distinguish driver from passenger mutations, we compared the mutational profiles of two specific AML1-ETO driven mouse models of leukemia to the mutational profiles of human AML patients. We found that the mouse models of AML1-ETO driven AML were phenotypically similar in terms of their extensive latency, myeloid progenitor immunophenotype, and the acquired secondary disease alleles. The first model relies upon the expression of AML1-ETO in transplanted p21 null cells, while the second model relies upon the expression of AML1-ETO9a, a splice variant of AML1-ETO, in transplanted wild type cells.p21 is neither disrupted, nor methylated in t(8;21)+ AML. Because loss of p21 prevents the repair of damaged DNA, leukemogenesis may occur in this model once a cooperating disease allele has been naturally acquired in an AML1-ETO positive hematopoietic progenitor. AML1-ETO9a itself deregulates the expression of several DNA repair genes, suggesting that AML1-ETO9a could similarly facilitate the acquisition of a cooperating disease allele.When we compared the mutational landscape of these murine leukemias to AML patients, we found that the murine leukemias enrich for disease alleles present in human AML (hypergeometric p ≤ 4.26x10-20) and that there is a significant tendency for disease alleles mutated in both species to possess mutations in the same protein domain (hypergeometric p ≤ 4.23x10-3). Furthermore, domains mutated in both species were affected by recurrent mutations (Spearman correlation of domain p-values r = 0.53, p ≤ 2.73x10-8). While the frequency with which various protein classes were affected by mutations was significantly different in MLL-AF9 and AML1-ETO/AML1-ETO9a positive murine AML compared to MLL-fusion and t(8;21)+ positive human AML (p = 0.049), the protein classes targeted in AML1-ETO/AML1-ETO9a murine AML vs. human t(8;21)+ AML were not significantly different (p = 0.327).To identify disease alleles capable of cooperating with AML1-ETO, we determined that of the 424 genes mutated in both species, 38 of those genes were significantly mutated in human AML (Genome MuSiC SMG FDR ≤ 30%). These 38 genes represented 45 mouse orthologues, 38 of which were significantly mutated in AML1-ETO driven murine leukemias (FDR ≤ 10%). These 38 orthologues corresponded to 32 human orthologues, 3 of which were annotated in COSMIC as cancer-related genes: TET2, PTPN11, and THRAP3.Using retroviral transduction and transplantation experiments, we demonstrated that the expression of AML1-ETO in transplanted Tet2 null cells or PTPN11 D61Y cells was sufficient for leukemogenesis. At euthanasia, mice exhibited leukocytosis, anemia, thrombocytopenia, splenomegaly, and an expansion in the myeloid progenitor compartment. Our identification of Tet2 loss as a cooperating allele implicates mutations in epigenetic regulators as potential driving events in t(8;21)+ AML, while the discovery of PTPN11 D61Y solidifies the role of constitutive MAPK signaling in t(8;21)+ AML.This integrative genetic profiling approach allowed us to accurately predict cooperating events in t(8;21)+ AML in a robust and unbiased manner, while also revealing functional convergence in mouse and human AML. Collectively, these findings illustrate the power of integrating murine and human genomic profiling to identify functionally relevant disease alleles in AML. DisclosuresLevine:CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Loxo Oncology: Membership on an entity's Board of Directors or advisory committees; Foundation Medicine: Consultancy.

Immunohistochemical detection of cytoplasmic nucleophosmin in formalin-fixed paraffin-embedded marrow trephine biopsies in acute myeloid leukaemia

AimsNucleophosmin (NPM1) gene mutations resulting in cytoplasmic delocalisation of nucleophosmin (NPMc+) are the most common genetic abnormality in acute myeloid leukaemia (AML). In this study, we tested whether immunohistochemical (IHC)...

Wnt signaling induces transcription, spatial proximity, and translocation of fusion gene partners in human hematopoietic cells

AbstractChromosomal translocations are frequently associated with a wide variety of cancers, particularly hematologic malignancies. A recurrent chromosomal abnormality in acute myeloid leukemia is the reciprocal translocation t(8;21) that fuses RUNX1 and ETO genes. We report here that Wnt/β-catenin signaling increases the expression of ETO and RUNX1 genes in human hematopoietic progenitors. We found that β-catenin is rapidly recruited into RNA polymerase II transcription factories (RNAPII-Ser5) and that ETO and RUNX1 genes are brought into close spatial proximity upon Wnt3a induction. Notably, long-term treatment of cells with Wnt3a induces the generation a frequent RUNX1-ETO translocation event. Thus, Wnt/β-catenin signaling induces transcription and translocation of RUNX1 and ETO fusion gene partners, opening a novel window to understand the onset/development of leukemia.

Clinical and prognostic significance of 3q26.2 and other chromosome 3 abnormalities in CML in the era of tyrosine kinase inhibitors

AbstractChromosome 3q26.2 abnormalities in acute myeloid leukemia, including inv(3)/t(3;3) and t(3;21), have been studied and are associated with a poor prognosis. Their prevalence, response to tyrosine kinase inhibitor (TKI) treatment, and prognostic significance in chronic myelogenous leukemia (CML) are largely unknown. In this study, we explored these aspects using a cohort of 2013 patients with CML diagnosed in the era of TKI therapy. Chromosome 3 abnormalities were observed in 116 (5.8%) of 2013 cases. These cases were divided into 5 distinct groups: A, inv(3)(q21q26.2)/t(3;3)(q21;q26.2), 26%; B, t(3;21)(q26.2;q22), 17%; C, other 3q26.2 rearrangements, 7%; D, rearrangements involving chromosome 3 other than 3q26.2 locus, 32%; and E, gain or loss of partial or whole chromosome 3, 18%. In all, 3q26.2 rearrangements were the most common chromosome 3 abnormalities (50%, groups A-C). 3q26.2 rearrangements emerged at different leukemic phases. For cases with 3q26.2 rearrangements that initially emerged in chronic or accelerated phase, they had a high rate of transformation to blast phase. Patients with 3q26.2 abnormalities showed a marginal response to TKI treatment, and no patients achieved a long-term sustainable response at a cytogenetic or molecular level. Compared with other chromosomal abnormalities in CML, patients with 3q26.2 rearrangements had poorer overall survival. The presence or absence of other concurrent chromosomal abnormalities did not affect survival in these patients, reflecting the predominant role of 3q26.2 rearrangements in determining prognosis. Interestingly, although heterogeneous, chromosome 3 abnormalities involving non-3q26.2 loci (groups D, E) also conferred a worse prognosis compared with changes involving other chromosomes in this cohort.

Update on Recurrent Genetic Aberrations in Acute Myeloid Leukemia

Recurrent chromosomal aberrations have long been recognized to influence prognosis in acute myeloid leukemia (AML), however, 50% of AML patients have a normal karyotype. The new millennium ushered in discoveries of gene mutations at the molecular level that predict outcome in patients with normal karyotype. Some recurrent mutations are already used in routine practice for AML risk stratification. With the development of high-throughput sequencing technologies, there has been a storm of new data, uncovering a complex genetic landscape in AML. In this review, we describe the significant progress in characterizing recurrent genetic abnormalities in AML in the last 5 years, focusing on prognostic significance and therapeutic implications.

Transcriptome Profiling of Pediatric Core Binding Factor AML.

The t(8;21) and Inv(16) translocations disrupt the normal function of core binding factors alpha (CBFA) and beta (CBFB), respectively. These translocations represent two of the most common genomic abnormalities in acute myeloid leukemia (AML) patients, occurring in approximately 25% pediatric and 15% of adult with this malignancy. Both translocations are associated with favorable clinical outcomes after intensive chemotherapy, and given the perceived mechanistic similarities, patients with these translocations are frequently referred to as having CBF-AML. It remains uncertain as to whether, collectively, these translocations are mechanistically the same or impact different pathways in subtle ways that have both biological and clinical significance. Therefore, we used transcriptome sequencing (RNA-seq) to investigate the similarities and differences in genes and pathways between these subtypes of pediatric AMLs. Diagnostic RNA from patients with t(8;21) (N = 17), Inv(16) (N = 14), and normal karyotype (NK, N = 33) were subjected to RNA-seq. Analyses compared the transcriptomes across these three cytogenetic subtypes, using the NK cohort as the control. A total of 1291 genes in t(8;21) and 474 genes in Inv(16) were differentially expressed relative to the NK controls, with 198 genes differentially expressed in both subtypes. The majority of these genes (175/198; binomial test p-value < 10−30) are consistent in expression changes among the two subtypes suggesting the expression profiles are more similar between the CBF cohorts than in the NK cohort. Our analysis also revealed alternative splicing events (ASEs) differentially expressed across subtypes, with 337 t(8;21)-specific and 407 Inv(16)-specific ASEs detected, the majority of which were acetylated proteins (p = 1.5x10-51 and p = 1.8x10-54 for the two subsets). In addition to known fusions, we identified and verified 16 de novo fusions in 43 patients, including three fusions involving NUP98 in six patients. Clustering of differentially expressed genes indicated that the homeobox (HOX) gene family, including two transcription factors (MEIS1 and NKX2-3) were down-regulated in CBF compared to NK samples. This finding supports existing data that the dysregulation of HOX genes play a central role in biology CBF-AML hematopoiesis. These data provide comprehensive transcriptome profiling of CBF-AML and delineate genes and pathways that are differentially expressed, providing insights into the shared biology as well as differences in the two CBF subsets.

MicroRNA-181a enhances the chemotherapeutic sensitivity of chronic myeloid leukemia to imatinib.

MicroRNA-181 (miR-181) has been recently demonstrated to participate in the differentiation and development of immune cells, including natural killer cells and B and T lymphocytes, and myeloid linages, including erythroid and megakaryocytic cells. The aberrant expression of miR-181, particularly low expression levels, has been observed in a number of leukemia types, including B-cell chronic lymphocytic leukemia and cytogenetically abnormal acute myeloid leukemia. However, the expression and function of miR-181 in chronic myeloid leukemia (CML) remains unknown. In the present study, the aberrant expression of miR-181a was analyzed in a patient with CML and in the CML K562 cell line. In addition, the function and potential mechanisms of miR-181a in K562 cells with regard to their chemotherapeutic sensitivity to imatinib were investigated. The expression levels of miR-181a were significantly reduced in the patient with CML and in the CML K562 cell line. Furthermore, the overexpression of miR-181a in the K562 cells enhanced the chemotherapeutic sensitivity of these cells to imatinib. The potential mechanism mediating these effects may be associated with the capacity of miR-181a to inhibit cell growth and/or to induce cells apoptosis and differentiation in K562 cells. The results of the present study suggested that miR-181a may be a target for the treatment of CML and a useful indicator of the therapeutic sensitivity of CML to imatinib.

Clinical and prognostic significance of 3q26 rearrangements and other chromosome 3 abnormalities in chronic myelogenous leukemia in era of tyrosine kinase inhibitors

Chromosome 3q26.2 abnormalities in acute myeloid leukemia (AML), including inv(3)/t(3;3) and t(3;21), have been studied and are associated with a poor prognosis. Their prevalence, response to tyrosine kinase inhibitor (TKI) treatment and prognostic significance in chronic myelogenous leukemia (CML) are largely unknown. In this study we explored these aspects using a cohort of 2013 CML patients in the era of TKI therapy. Chromosome 3 abnormalities were observed in 116 of 2013 (5.8%) cases. These cases were divided into five distinct groups: A, inv(3)(q21q26.2)/t(3;3)(q21;q26.2), 26%; B, t(3;21)(q26.2;q22), 17%; C, other 3q26.2 rearrangements, 7%; D, rearrangements involving chromosome 3 other than 3q26.2 locus, 32%; and E, gain or loss of partial or whole chromosome 3, 18%. In all, 3q26.2 rearrangements were the most common chromosome 3 abnormalities (50%, groups A-C). 3q26.2 rearrangements emerged at different leukemic phases. For cases with 3q26.2 rearrangements that initially emerged in chronic or accelerated phase, they had a high rate of transformation to blast phase. Patients with 3q26.2 abnormalities showed a marginal response to TKIs treatment and no patients achieved a long-term sustainable response at cytogenetic or molecular level. Compared to other chromosomal abnormalities in CML, patients with 3q26.2 rearrangements had a poorer overall survival. The presence or absence of other concurrent chromosomal abnormalities did not affect survival in these patients, reflecting the predominant role of 3q26.2 rearrangements in determining prognosis. Interestingly, although heterogeneous, chromosome 3 abnormalities involving non-3q26.2 loci (groups D, E) also conferred a worse prognosis compared with changes involving other chromosomes in this cohort.

Incidence and Prognostic Value of Known Genetic Aberrations in Patients with Acute Myeloid Leukemia – a Two Year Study

In this work, we evaluated the incidence and prognostic value of several genetic aberrations in patients with a diagnosis of acute myeloid leukemia (AML). We analysed 90 patients: 42 males (mean age 54.5 years) and 48 females (mean age 59 years), with AML. The genetics of all leukemia samples was studied using conventional cytogenetics, the interphase fluorescence in situ hybridisation as well as the standardized RTPCR protocol. In 34.4% of patients, we detected at least one of the analysed genetic aberrations, except the CBFB MYH11, which we did not detect. Translocation t(8;21)/ AML1 ETO was found in 4.4% of patients with a mean age of 45.4 years, while none of these patients was older than 55 years. Translocation t(15;17)/ PMLRARA was found in 5.5% of patients with a mean age of 52.6 years and an almost equal distribution between younger and older patients. The MLL gene rearrangements were found in 6.6% of patients, the -5/ 5q- and/ or -7/ 7q- aberrations in 7.7% of patients, while the most frequent genetic abnormality in our study was trisomy 8 (10%). Moreover, we found a favorable clinical outcome in patients expressing fusion genes AML1-ETO or PMLRARA in contrast to an adverse clinical outcome with few remissions and death in AML patients with MLL, -5q/ -5 and -7q/ 7-. Finally, an intermediate prognosis was found in patients with trisomy 8. In this study, we found a good congruence with published literature on the incidence and prognostic value of several well established AML-associated genetic aberrations. This simple genetic-based classification system helps us to identify patients with a favorable, intermediate or unfavorable prognosis and to treat them with the best currently available therapy. However, analysis of new genetically defined abnormalities in AML is necessary for development of better therapeutic strategies and/or diagnostics.

Retrospective evaluation of the clinical and laboratory data from 300 patients of various hematological malignancies with chromosome 3 abnormalities

This retrospective study was designed to evaluate the clinical and laboratory behaviors of chromosome 3 abnormalities by analyzing the morphological, cytogenetic, and follow-up data from 300 patients of various hematological malignancies with chromosome 3 abnormalities. From the results, trisomy 3, translocation (3q), and del(3) were the abnormal types most frequently observed (>10%) among the chromosome 3 abnormalities. In hematological malignancies, chromosome 3 abnormalities were most frequently seen in the patients with acute myeloid leukemia (AML) (24.7%) and myelodysplastic syndrome (MDS) (16%), followed by those with acute lymphocytic leukemia (ALL) (13.7%) and multiple myeloma (MM) (12.7%). In this series, genomic losses were the most frequent genetic abnormalities in AML, ALL, and hybrid acute leukemia (HAL) patients, whereas structural rearrangements were frequently seen in chronic myeloid leukemia (CML) and MDS patients, and genomic gains in MM, lymphoma and chronic lymphocytic leukemia (CLL) patients. Chromosome 3 abnormalities mainly occurred as a component of a complex abnormality (251/300) rather than a sole one (14/300). Survival analysis demonstrated a statistical difference between the patients with trisomy 3, who had a better prognosis, and patients with del(3), who had a worse prognosis in this series (P < 0.05). Abnormalities in chromosome 3 may imply an unfavorable outcome in CML and ALL.

Trisomy chromosome 6 as a sole cytogenetic abnormality in acute myeloid leukemia.

Identification of cytogenetic abnormalities plays an important role in the diagnosis and prognosis of leukemias. Isolated trisomy 6 is a rare abnormality, the prognostic significance of which is not well established. We report one case of acute myeloid leukemia (AML-M5 variant) with trisomy 6 as the sole cytogenetic abnormality. Previously, trisomy 6 has been reported in aplastic anemia, myelodysplastic syndrome, and AML, usually associated with hypocellular marrow. However, our patient had a very short history and hypercellular marrow infiltrated with blasts. We report this case due to the rarity of the condition. More studies are required to ascertain the role of trisomy 6 in the development of leukemia as well as in prognosis.

Integration of gene expression and DNA-methylation profiles improves molecular subtype classification in acute myeloid leukemia.

BackgroundAcute Myeloid Leukemia (AML) is characterized by various cytogenetic and molecular abnormalities. Detection of these abnormalities is important in the risk-classification of patients but requires laborious experimentation. Various studies showed that gene expression profiles (GEP), and the gene signatures derived from GEP, can be used for the prediction of subtypes in AML. Similarly, successful prediction was also achieved by exploiting DNA-methylation profiles (DMP). There are, however, no studies that compared classification accuracy and performance between GEP and DMP, neither are there studies that integrated both types of data to determine whether predictive power can be improved.ApproachHere, we used 344 well-characterized AML samples for which both gene expression and DNA-methylation profiles are available. We created three different classification strategies including early, late and no integration of these datasets and used them to predict AML subtypes using a logistic regression model with Lasso regularization.ResultsWe illustrate that both gene expression and DNA-methylation profiles contain distinct patterns that contribute to discriminating AML subtypes and that an integration strategy can exploit these patterns to achieve synergy between both data types. We show that concatenation of features from both data sets, i.e. early integration, improves the predictive power compared to classifiers trained on GEP or DMP alone. A more sophisticated strategy, i.e. the late integration strategy, employs a two-layer classifier which outperforms the early integration strategy.ConclusionWe demonstrate that prediction of known cytogenetic and molecular abnormalities in AML can be further improved by integrating GEP and DMP profiles.

Cytogenetic Patterns of Relapse Following Stem Cell Transplantation in Morphologic Complete Remission in Patients with Cytogenetically Abnormal Acute Myeloid Leukemia

Cytogenetic Patterns of Relapse Following Stem Cell Transplantation in Morphologic Complete Remission in Patients with Cytogenetically Abnormal Acute Myeloid Leukemia

Combining the differentiating effect of panobinostat with the apoptotic effect of arsenic trioxide leads to significant survival benefit in a model of t(8;21) acute myeloid leukemia.

BackgroundOne of the most frequently found abnormalities in acute myeloid leukemia (AML) is the t(8;21)(q22;q22) translocation, which is seen in around 15% of patients. This translocation results in the production of the AML1/ETO (A/E) fusion protein and commonly involves cooperating activating mutations of RAS. AE9a encodes a C-terminally truncated A/E protein of 575 amino acids that retains the ability to recruit histone deacetylases (HDACs). Expression of AE9a leads to rapid development of leukemia in experimental mouse systems. We have recently shown that treatment of mice bearing A/E9a;NrasG12D tumors with the histone deacetylase inhibitor (HDACi) panobinostat leads to degradation of the A/E9a fusion protein, cell cycle arrest, differentiation of AML blasts into mature granulocytes and prolonged survival. Herein, we sought to enhance this therapeutic effect.FindingsCombined treatment of mice bearing A/E9a;NrasG12D leukemias with panobinostat and arsenic trioxide (ATO) resulted in a significant survival advantage compared to mice treated with either agent alone. Moreover, some of the mice treated with the panobinostat/ATO combination showed complete tumor responses and remained in remission for over 220 days. Panobinostat caused differentiation of A/E9a;NrasG12D cells while ATO induced apoptosis of the leukemic cells, an effect that was enhanced following co-treatment with panobinostat.ConclusionsOur results indicate that leukemic blast differentiation mediated by panobinostat combined with induction of apoptosis by ATO could be therapeutically beneficial and should be considered for patients with t(8;21) AML.Electronic supplementary materialThe online version of this article (doi:10.1186/s13148-014-0034-4) contains supplementary material, which is available to authorized users.

Trisomy 6 as Sole Cytogenetic Abnormality in Acute Myeloid Leukemia “A Case Series”

Identification of cytogenetic abnormalities plays an important role in the diagnosis and prognosis of leukemias. We report three cases of trisomy 6 as sole cytogenetic abnormality in acute myeloid leukemia (AML). Short-term unstimulated bone marrow culture showed two cases of AML-M1 and one case of AML-M2 with trisomy 6. It is known that trisomy 6 is a rare numerical abnormality and prognostic significance is not well established. More studies are required to assign the role of trisomy 6 in the development of leukemia as well as in prognosis.

The Impact of Molecular Genetic in Acute Myeloid Leukemias

The discovery and application of advanced molecular techniques, such as gene and microRNA expression profiling, whole genome and exome sequencing and methylation assays, allowed for the identification of recurrent molecular abnormalities in acute myeloid leukemia (AML) that have revolutionized our understanding of the genetic landscape of the disease. Moreover, these modalities have emerged as valuable tools that permit a more comprehensive and detailed molecular characterization of AML, helping in the prediction of prognosis, particularly within the context of cytogenetically normal AML (CN-AML). This review will discuss the major techniques and platforms that have been used to identify novel recurrent gene mutations in AML and briefly describe how these discoveries have impacted on outcome prediction.

Identification and Analysis of Oncogenic Pathways in Deletion 20q Acute Myeloid Leukaemia

Deletion of the long arm of chromosome 20 [del(20q)] is a common recurrent chromosomal abnormality in acute myeloid leukaemia (AML) and myeloproliferative neoplasms (MPN). The abnormal chromosome 20 has a “Common Deleted Region” (CDR) that contains Protein Tyrosine Phosphatase Receptor T (PTPRT), a tyrosine phosphatase that is mutated in many human cancers. We have previously reported (MacKinnon et al, Genes, Chromosomes and Cancer 2010) that del(20q) also harbours an amplified “Common Retained Region,” (CRR) which contains multiple copies of Haemopoietic Cell Kinase (HCK). HCK is an oncogenic Src tyrosine kinase and its aberrant activation has been shown to contribute to the pathogenesis of some haematological malignancies.Our hypothesis is that the amplification of HCK in the CRR cooperated with the loss of PTPRT in the CDR. Indeed, our results strongly suggested that HCK amplification with PTPRT loss led to a myeloproliferative phenotype seen in MPN.Our model proposed that MPN occurred either through the consequence of direct interaction between HCK and PTPRT, or through aberrant activation of Signal Transducer and Activator of Transcription 3 (STAT3). Constitutively activated STAT3 has been shown to be oncogenic in several haematological malignancies. STAT3 is a direct target of both HCK and PTPRT. It is phosphorylated (hence activated) by HCK, and dephosphorylated (hence inactivated) by PTPRT. This provides a downstream leukaemogenic pathway for our model.The ultimate aim of our experiments is to prove this hypothesis using mouse models. Murine haemopoietic stem cells (HSC) were isolated from the bone marrows of wild type C57BL/6 (WT) and PTPRT-null mice by Fluorescence Activated Cell Sorting for Lineage negative, C-kit and Sca-1 positive (LKS+) cells. Retroviral constructs of HCK were generated by cloning it into the retroviral vector pMSCViresEGFP(MIG), with GFP as reporter. Murine HSC were transduced with either retroviral HCK or MIG vector control. Hence wild type (WT) and PTPRT-null murine HSC transduced with either MIG or HCK were used in our experiments (WTMIG, WTHCK, PTPRTMIG, PTPRTHCK).We have previously presented that PTPRTHCK showed a significant increase in methylcelluose colony numbers and colony sizes compared to PTPRTMIG, while there was no difference between WTMIG and WTHCK. In addition, an intracellular anti-phosphoSTAT3 antibody assay demonstrated that in both WTHCK and PTPRTHCK, significant STAT3 hyperphosphorylation, and hence overactivation, occurred. This response was more exaggerated in the PTPRTHCK. Finally, direct interaction between HCK and PTPRT was shown with an interaction assay using recombinant proteins. We now present the in vivo data in the murine recipients.In Vivo ReconstitutionLKS+ HSC transduced with either MIG or HCK were transplanted into lethally irradiated SJL/PTPRCa murine recipients to assess AML or MPN formation in a reconstitution study over 12 months. The recipients from the four cohorts (WTMIG, WTHCK, PTPRTMIG and PTPRTHCK) were regularly analysed by full blood counts, peripheral blood GFP%, and blood films. At 12 months, they were culled and the organs harvested and analysed by flow cytometry, cytospin, and paraffin-embedded histology (H + E and immunohistochemistry). Recipents of PTPRTHCK HSC had a significantly higher proportion of nucleated erythroid populations in the bone marrow by flow and larger splenic size by weight. They also showed a higher haemoglobin (Hb) at 12 months, although this did not reach statistical significance. [Display omitted] [Display omitted] [Display omitted] ConclusionThe data reveal a likely new oncogenic-signalling cascade: that HCK amplification and loss of PTPRT in del(20q) may cooperate to cause MPN directly, or by aberrant activity of hyperphosphorylated STAT3. DisclosuresNo relevant conflicts of interest to declare.

AML1/ETO Cooperates with HIF1α to Promote Leukemogenesis through DNMT3a Transactivation

The t(8;21)(q22;q22) translocation, resulting in a chimeric protein AML1/ETO (A/E), is one of the most common chromosomal abnormalities in acute myeloid leukemia (AML). It has been reported that additional mutagenic “hits” are required for A/E to be a leukemic driver, but it is unclear why most A/E-positive patients don’t carry such gene mutations. We hypothesized that unconventional and more universal events might cooperate with A/E to drive leukemogenesis. Hypoxia inducible factor 1a (HIF1a) is a transcription factor mediating the cellular response to hypoxia in malignant cells. To identify the key molecule responsible for A/E-driven leukemia, we focused on HIF1a signaling, as it is selectively activated in AML stem cells in a hypoxia-independent fashion.Using qPCR analysis, we measured HIF1a mRNA levels in bone marrow mononuclear cells from 73 A/E-positive and 59 A/E-negative patients with newly diagnosed AML and 15 healthy donors. HIF1a was highly expressed in A/E-positive patients, as compared to A/E-negative patients and healthy controls. The expression of HIF1a was positively correlated with the expression of A/E, independent of KIT mutation. Patients were grouped into quartiles according to HIF1a expression levels (Q1-Q4, each quartile containing 25% of patients) and divided into high HIF1a (HIF1a high, Q4; n = 33) and low HIF1a (HIF1a low, Q1-Q3; n = 99). AE-positive patients with high HIF1a expression had a significantly shorter OS (median = 19.0 months vs. not reached, P = 0.015) and EFS (median = 9.0 months vs. 24.0 months, P = 0.001) compared to those with low HIF1a expression. Notably, HIF1a-associated inferior prognosis in A/E-positive patients was KIT mutation-independent. In patients carrying wild-type KIT [n = 53, about 73% (53/73) of the entire A/E-patients], those with high HIF1a levels had a shorter OS (median = 23.1 months vs. not reached, P = 0.008) and EFS (median = 9.4 months vs. not reached, P = 0.001) than those with low HIF1a levels. Multivariate analysis revealed that high HIF1a levels were independent prognostic indicators for both OS and EFS (P = 0.014, HR = 3.574 and P = 0.004, HR = 4.304, respectively) in AE-positive patients. Mechanistic studies revealed that A/E and HIF1a formed a positive regulatory circuit, in which A/E bound to HIF1a gene promoter and transactivated HIF1a or vice versa. Co-expression of AE and HIF1a in leukemia cells caused a higher cell proliferation rate in vitro and more serious leukemic status in mice. To gain insight into the molecular basis of A/E-HIF1a functional cooperation in leukemogenesis, we examined the mRNA levels of DNMT1, DNMT3a and DNMT3b expression in bone marrow samples from above-mentioned AML patients and healthy donors using qPCR. The result showed that DNMT3a, but not DNMT1 and DNMT3b, was significantly overexpressed in A/E-positive patients, as compared to A/E-negative patients and healthy donors. DNMT3a levels were positively correlated with both A/E and HIF1a levels. We therefore focused on evaluating the role of DNMT3a in A/E-positive AML. We found that DNMT3a expression was positively correlated with both A/E and HIF1a levels. As an individual event, A/E or HIF1a was enriched on DNMT3a gene promoter and synergistically increased DNMT3a transcription and enhanced global DNA methylation. Pharmacological or genetic interventions in the AE-HIF1a loop resulted in DNA hypomethylation, a reexpression of hypermethylated tumor suppressor p15INK4band the blockage of leukemia growth.In summary, we showed that A/E and HIF1a form a regulatory circuit and cooperatively control aggressive leukemia growth through DNMT3a transactivation and subsequent DNA hypermethylation. Thus, the HIF1a-DNMT3a nexus serves as a reliable marker, which identifies patients with a poor prognosis in an otherwise prognostically favorable AML group, and represents an innovative therapeutic target in high-risk AE-positive leukemia. DisclosuresNo relevant conflicts of interest to declare.

Frequency of 11q23/MLL gene rearrangement in Egyptian childhood acute myeloblastic leukemia: Biologic and clinical significance.

Background:Molecular cytogenetic abnormalities involving 11q23 are among the most common cytogenetic abnormalities in acute myeloid leukemia (AML) patients.Aim of the work:we aimed to evaluate the frequency of MLL/AF9 fusion gene in de novo AML patients, its impact on clinical features, and its prognostic significance.Patients and Methods:Twenty-eight children patients with AML and 20 healthy controls were subjected to complete clinical examination and laboratory investigations including, complete hemogram and bone marrow (BM) examination. Diagnosis was based on FAB morphologic and immunophenotypic criteria. Detection of (MLL/AF9) fusion gene was assessed by dual color fluorescent in situ hybridization (FISH). Follow-up were carried out clinically and by blast count in BM, and response to therapy to detect the outcome of the disease.Results:The incidence of MLL-fusion gene MLL/AF9 in AML cases was about (6/28) (21%). Four patients with MLL/AF9 fusion gene were newly diagnosed, two cases were at relapse and no patient at remission showed positivity. As regard the clinical outcome, five out of six MLL positive cases died, three of them during induction and two during relapse. The FAB AML subtypes with MLL/AF9 fusion were one M2, three M4, and two M5.Conclusion:MLL-fusion gene MLL/AF9 was found in about 21% of studied AML patients when assessed by FISH technique and this is of high clinical relevance as most of these abnormalities have been associated with poor prognosis.

The Use of Molecular Genetics to Refine Prognosis in Acute Myeloid Leukemia

The discovery and application of advanced molecular techniques, such as gene and microRNA expression profiling, whole genome and exome sequencing, proteomic analysis and methylation assays, have allowed for the identification of recurrent molecular abnormalities in acute myeloid leukemia (AML) that have revolutionized our understanding of the genetic landscape of the disease. These modalities have emerged as valuable tools that permit a more comprehensive and detailed molecular characterization of AML. Many of these molecular abnormalities have been shown to predict prognosis, particularly within the context of cytogenetically normal AML. This review will discuss the major techniques and platforms that have been used to identify novel recurrent gene mutations in AML and briefly describe how these discoveries have impacted on outcome prediction.