Germline GATA1s-generating mutations predispose to leukemia with acquired trisomy 21 and Down syndrome-like phenotype.

Individuals with Down syndrome are at increased risk of myeloid leukemia in early childhood, which is associated with acquisition of GATA1 mutations that generate a short GATA1 isoform called GATA1s. Germline GATA1s-generating mutations result in congenital anemia in males. We report on 2 unrelated families that harbor germline GATA1s-generating mutations in which several members developed acute megakaryoblastic leukemia in early childhood. All evaluable leukemias had acquired trisomy 21 or tetrasomy 21. The leukemia characteristics overlapped with those of myeloid leukemia associated with Down syndrome, including age of onset at younger than 4 years, unique immunophenotype, complex karyotype, gene expression patterns, and drug sensitivity. These findings demonstrate that the combination of trisomy 21 and GATA1s-generating mutations results in a unique myeloid leukemia independent of whether the GATA1 mutation or trisomy 21 is the primary or secondary event and suggest that there is a unique functional cooperation between GATA1s and trisomy 21 in leukemogenesis. The family histories also indicate that germline GATA1s-generating mutations should be included among those associated with familial predisposition for myelodysplastic syndrome and leukemia.

RecQ helicase expression in patients with telomeropathies.

BACKGROUND: Telomeropathies are a group of inherited disorders caused by germline pathogenic variants in genes involved in telomere maintenance, resulting in excessive telomere attrition that affects several tissues, including hematopoiesis. RecQ and RTEL1 helicases contribute to telomere maintenance by unwinding telomeric structures such as G-quadruplexes (G4), preventing replication defects. Germline RTEL1 variants also are etiologic in telomeropathies. METHODS AND RESULTS: Here we investigated the expression of RecQ (RECQL1, BLM, WRN, RECQL4, and RECQL5) and RTEL1 helicase genes in peripheral blood mononuclear cells (PBMCs) from human telomeropathy patients. The mRNA expression levels of all RecQ helicases, but not RTEL1, were significantly downregulated in patients' primary cells. Reduced RecQ expression was not attributable to cell proliferative exhaustion, as RecQ helicases were not attenuated in T cells exhausted in vitro. An additional fifteen genes involved in DNA damage repair and RecQ functional partners also were downregulated in the telomeropathy cells. CONCLUSION: These findings indicate that the expression of RecQ helicases and functional partners involved in DNA repair is downregulated in PBMCs of telomeropathy patients.

Immunophenotypically defined stem cell subsets in paediatric AML are highly heterogeneous and demonstrate differences in BCL-2 expression by cytogenetic subgroups.

In adult acute myeloid leukaemia (AML), immunophenotypic differences enable discrimination of leukaemic stem cells (LSCs) from healthy haematopoietic stem cells (HSCs). However, immunophenotypic stem cell characteristics are less explored in paediatric AML. Employing a 15-colour flow cytometry assay, we analysed the expression of eight aberrant surface markers together with BCL-2 on CD34+ CD38- bone marrow stem cells from 38 paediatric AML patients and seven non-leukaemic, age-matched controls. Furthermore, clonality was investigated by genetic analyses of sorted immunophenotypically abnormal stem cells from six patients. A total of 50 aberrant marker positive (non-HSC-like) subsets with 41 different immunophenotypic profiles were detected. CD123, CLEC12A, and IL1RAP were the most frequently expressed markers. IL1RAP, CD93, and CD25 expression were not restricted to stem cells harbouring leukaemia-associated mutations. Differential BCL-2 expression was found among defined cytogenetic subgroups. Interestingly, only immunophenotypically abnormal non-HSC-like subsets demonstrated BCL-2 overexpression. Collectively, we observed pronounced immunophenotypic heterogeneity within the stem cell compartment of paediatric AML patients. Additionally, certain aberrant markers used in adults seemed to be ineligible for detection of leukaemia-representing stem cells in paediatric patients implying that inference from adult studies must be done with caution.

Outcome of treatment with carfilzomib before and after treatment with daratumumab in relapsed or refractory multiple myeloma patients.

Real world evidence is important since most patients cannot be included in randomized clinical trials (RCTs). In a nationwide, cohort of relapsed/refractory multiple myeloma patients treated with daratumumab (N = 635), we retrospective studied patients treated with carfilzomib (N = 251). Data were collected by audit of medical records. We compared characteristics of patients treated with carfilzomib before daratumumab (Car-Da; N = 150) and after daratumumab (Da-Car; N = 101) with those not treated with carfilzomib (N = 384). Furthermore, we examined effectiveness and safety of carfilzomib. The group of patients treated with carfilzomib differed from patients not treated with carfilzomib in the following parameters: They were younger, more were treated up-front with high dose melphalan and autologous stem cell transplantation (HDM-ASCT)and had relapse within 18 months thereafter, and more had high-risk cytogenetic abnormalities (CA) and amplification 1q (amp1q). In patients treated with Car-Da, 30.3% had high-risk CA and 30.1% had amp1q and in Da-Car it was 43.3% and 41%, respectively. In the Car-Da cohort, 34.4% experienced early relapse after HDM-ASCT versus 47.4% in the Da-Car cohort. The percentage of patients with very good partial remission was higher in patients treated with Car-Da compared to Da-Car (31.7% vs. 17.4%). The median duration of treatment and time to next treatment (TNT) of Car-Da/Da-Car were 4.6/4.3 months and 7.1/4.3 months and only a trend toward superior TNT for Car-Da was found (p = 0.06). Toxicity of carfilzomib was the same as reported in RCT. A similar poor TNT of daratumumab was found when used before (5.6 months) or after carfilzomib (4.9 months). In this cohort of patients with sequential treatment with carfilzomib and daratumumab or vice versa, a high percentage of patients were high-risk by CA, amp1q, and early relapse after HDM-ASCT. Outcome of Car-DA and outcome of Da-Car were equally poor. These patients should be considered for new promising treatment strategies.

IG-MYC + neoplasms with precursor B-cell phenotype are molecularly distinct from Burkitt lymphomas.

The WHO Classification of Tumours of Haematopoietic and Lymphoid Tissue notes instances of Burkitt lymphoma/leukemia (BL) with IG-MYC rearrangement displaying a B-cell precursor immunophenotype (termed herein "preBLL"). To characterize the molecular pathogenesis of preBLL, we investigated 13 preBLL cases (including 1 cell line), of which 12 were analyzable using genome, exome, and targeted sequencing, imbalance mapping, and DNA methylation profiling. In 5 patients with reads across the IG-MYC breakpoint junctions, we found evidence that the translocation derived from an aberrant VDJ recombination, as is typical for IG translocations arising in B-cell precursors. Genomic changes like biallelic IGH translocations or VDJ rearrangements combined with translocation into the VDJ region on the second allele, potentially preventing expression of a productive immunoglobulin, were detected in 6 of 13 cases. We did not detect mutations in genes frequently altered in BL, but instead found activating NRAS and/or KRAS mutations in 7 of 12 preBLLs. Gains on 1q, recurrent in BL and preB lymphoblastic leukemia/lymphoma (pB-ALL/LBL), were detected in 7 of 12 preBLLs. DNA methylation profiling showed preBLL to cluster with precursor B cells and pB-ALL/LBL, but apart from BL. We conclude that preBLL genetically and epigenetically resembles pB-ALL/LBL rather than BL. Therefore, we propose that preBLL be considered as a pB-ALL/LBL with recurrent genetic abnormalities.

CRISPR-C: circularization of genes and chromosome by CRISPR in human cells.

Extrachromosomal circular DNA (eccDNA) and ring chromosomes are genetic alterations found in humans with genetic disorders. However, there is a lack of genetic engineering tools to recapitulate and study the biogenesis of eccDNAs. Here, we created a dual-fluorescence biosensor cassette, which upon the delivery of pairs of CRISPR/Cas9 guide RNAs, CRISPR-C, allows us to study the biogenesis of a specific fluorophore expressing eccDNA in human cells. We show that CRISPR-C can generate functional eccDNA, using the novel eccDNA biosensor system. We further reveal that CRISPR-C also can generate eccDNAs from intergenic and genic loci in human embryonic kidney 293T cells and human mammary fibroblasts. EccDNAs mainly forms by end-joining mediated DNA-repair and we show that CRISPR-C is able to generate endogenous eccDNAs in sizes from a few hundred base pairs and ranging up to 207 kb. Even a 47.4 megabase-sized ring chromosome 18 can be created by CRISPR-C. Our study creates a new territory for CRISPR gene editing and highlights CRISPR-C as a useful tool for studying the cellular impact, persistence and function of eccDNAs.

Revisiting CLEC12A as leukaemic stem cell marker in AML: highlighting the necessity of precision diagnostics in patients eligible for targeted therapy.

Targeted therapy directed against rare disease-propagating leukaemic stem cells (LSCs) is a promising prospect for improving the outcome of acute myeloid leukaemia (AML) patients. Thus, distinguishing LSCs from normal haematopoietic stem and progenitor cells (HSPCs) is essential. The CLEC12A receptor has been proposed as a specific marker of LSCs, and consequently as an appealing treatment target. To explore the role of CLEC12A in further detail, we investigated whether a sorting strategy based on the activity of aldehyde dehydrogenase and CLEC12A expression could separate residual normal HSPCs from LSCs in bone marrow from 5 AML patients. We demonstrate that this distinction was possible in 2/5 cases, however with evidence of pre-leukaemic mutations in the CLEC12A- stem cells in one case. In contrast, cytogenetic and/or molecular aberrations were detected in both the CLEC12A+/- cell subsets in 3/5 AML cases studied. Furthermore, targeted next generation sequencing (NGS) of the sorted cell subsets revealed a pronounced clonal heterogeneity in the CLEC12A- cells suggestive of the leukaemia often originating in this immature cell subset. In conclusion, we provide proof-of-concept that precision diagnostics employing targeted cytogenetic/NGS-based analyses on highly purified cell subsets could be a powerful tool for selecting patients eligible for LSC-directed therapy.

Addressing the room for improvement in management of acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is highly curable. To achieve high cure rates, targeted therapy with retinoic acid (ATRA) must be started promptly at time of suspected diagnosis. Early death rates (EDRs, ≤30 days from diagnosis) differ markedly in patients treated on clinical trials compared to the general population. OBJECTIVES AND METHODS: We used the comprehensive Danish National Acute Leukemia Registry (DNLR) to investigate the incidence, treatment, EDR, and long-term clinical outcome in APL between 2000 and 2014. RESULTS: Twenty-two of 41 deaths occurring in 122 APL patients were EDs which were primarily caused by intracranial hemorrhage, disseminated intravascular coagulation (DIC), sepsis, and multiorgan failure. The overall EDR was 18.0%, whereas clinical trial participants had an EDR of 6.7%. Fifteen patients recruited to the NCRI AML17 APL trial from 2010 to 2013 were younger and had decreased mortality (HR 0.18, CI 0.04-0.86, P = 0.02) compared to contemporarily treated patients (n = 15) not recruited to a clinical trial. Performance status, leukemia origin, and Sanz-score were independent prognostic variables. CONCLUSIONS: The very low EDR for on-trial patients is not observed in the general cohort of APL patients. Diagnostic awareness emerges as the greatest clinical challenge in management of APL.

Systematic evaluation of signal-to-noise ratio in variant detection from single cell genome multiple displacement amplification and exome sequencing.

BACKGROUND: The current literature on single cell genomic analyses on the DNA level is conflicting regarding requirements for cell quality, amplification success rates, allelic dropouts and resolution, lacking a systematic comparison of multiple cell input down to the single cell. We hypothesized that such a correlation assay would provide an approach to address the latter issues, utilizing the leukemic cell line OCI-AML3 with a known set of genetic aberrations. RESULTS: By analyzing single and multiple cell replicates (2 to 50 cells) purified by micromanipulation and serial dilution we stringently assessed the signal-to-noise ratio (SNR) from single as well as a discrete number of cells based on a multiple displacement amplification method, with whole exome sequencing as signal readout. In this setting, known OCI-AML3 mutations as well as large copy number alterations could be identified, adding to the current knowledge of cytogenetic status. The presence of DNMT3A R882C, NPM1 W288 fs and NRAS Q61L was consistent, in spite of uneven allelic read depths. In contrast, at the level of single cells, we observed that one-third to half of all variants were not reproduced in the replicate sample, and this allelic mismatch displayed an exponential function of cell input. Large signature duplications were discernible from 5 cells, whereas deletions were visible down to the single cell. Thus, even under highly optimized conditions, single cell whole genome amplification and interpretation must be taken with considerable caution, given that allelic change is frequent and displays low SNR. Allelic noise is rapidly alleviated with increased cell input, and the SNR is doubled from 2 to 50 cells. CONCLUSIONS: In conclusion, we demonstrate noisy allele distributions, when analyzing genetic aberrations within single cells relative to multiple cells. Based on the presented data we recommend that single cell analyses should include replicate cell dilution assays for a given setup for relative assessment of procedure-specific SNR to ensure that the resolution supports the specific hypotheses.

Complex and monosomal karyotype are distinct cytogenetic entities with an adverse prognostic impact in paediatric acute myeloid leukaemia. A NOPHO-DBH-AML study.

Data on occurrence, genetic characteristics and prognostic impact of complex and monosomal karyotype (CK/MK) in children with acute myeloid leukaemia (AML) are scarce. We studied CK and MK in a large unselected cohort of childhood AML patients diagnosed and treated according to Nordic Society for Paediatric Haematology and Oncology (NOPHO)-AML protocols 1993-2015. In total, 800 patients with de novo AML were included. CK was found in 122 (15%) and MK in 41 (5%) patients. CK and MK patients were young (median age 2·1 and 3·3 years, respectively) and frequently had FAB M7 morphology (24% and 22%, respectively). Refractory disease was more common in MK patients (15% vs. 4%) and stem cell transplantation in first complete remission was more frequent (32% vs. 19%) compared with non-CK/non-MK patients. CK showed no association with refractory disease but was an independent predictor of an inferior event-free survival (EFS; hazard ratio [HR] 1·43, P = 0·03) and overall survival (OS; HR 1·48, P = 0·01). MK was associated with a poor EFS (HR 1·57, P = 0·03) but did not show an inferior OS compared to non-MK patients (HR 1·14, P = 0·62). In a large paediatric cohort, we characterized AML with non-recurrent abnormal karyotype and unravelled the adverse impact of CK and MK on prognosis.

Characterization of an acquired jumping translocation involving 3q13.31-qter in a patient with de novo acute monocytic leukemia.

We studied an adult with de novo acute monocytic leukemia and a dismal outcome where her leukemic cells harbored an acquired rare jumping translocation (JT). We used oligo-based array CGH (oaCGH) analysis, fluorescence in situ hybridization (FISH), and 24-color karyotyping to enhance the characterization of the JT. G-banding detected a JT involving the 3q13.3-qter chromosomal segment and the recipient chromosomal regions 17p, 8q, and 15q. Each clone with JT was associated with trisomy 8. oaCGH analysis revealed an additional submicroscopic deletion in 3q13.31 as well as small subtelomeric duplications on several chromosomes. Locus-specific FISH with BAC-based probes from the 3q13.31-q13.32 region showed great heterogeneity. Telomere FISH revealed significantly reduced telomeric content in the aberrant cells with JT compared with cytogenetically normal cells at diagnosis and in normal cells at complete remission. A literature search revealed two previous de novo AML-M5 cases of JT involving the 3q13.3-qter chromosomal segment and concomitant trisomy 8. In addition, a case with an unbalanced der(Y)t(Y;3)(q12;q13.31) and additional trisomy 8 was previously reported in a patient with de novo AML-M5. All of these cases had a dismal outcome. In the present case, and in the der(Y)t(Y;3) case, a concurrent submicroscopic deletion at 3q13.31 was observed affecting the TUSC7 gene. Duplication of 3q13.31-qter might be a non-random chromosomal abnormality with concomitant submicroscopic deletion at 3q13.31 occurring in rare cases of acute monocytic leukemia, being associated with adverse prognosis. The impact of shortened telomeres in forming the JT is reviewed.

Trisomy 8 in pediatric acute myeloid leukemia: A NOPHO-AML study.

Trisomy 8 (+8) is a common cytogenetic aberration in acute myeloid leukemia (AML); however, the impact of +8 in pediatric AML is largely unknown. We retrospectively investigated 609 patients from the NOPHO-AML database to determine the clinical and cytogenetic characteristics of +8 in pediatric AML and to investigate its prognostic impact. Complete cytogenetic data were available in 596 patients (98%) aged 0-18 years, diagnosed from 1993 to 2012, and treated according to the NOPHO-AML 1993 and 2004 protocols in the Nordic countries and Hong Kong. We identified 86 patients (14%) with +8. Trisomy 8 was combined with other cytogenetic aberrations in 68 patients (11%) (+8 other) and in 18 patients (3%), it was the sole abnormality (+8 alone). Trisomy 8 was associated with FAB M5 (36%) but otherwise clinically comparable with non-trisomy 8 patients. Trisomy 8 was favorable in patients of young age and with t(9;11). Trisomy 8 alone was associated with older age (median age 10.1 years), FAB M2 (33%), and FLT3-ITD mutations (58%). The 5-year event-free survival for patients with +8 alone was 50% and 5-year overall survival was 75%. In conclusion, +8 is one of the most common cytogenetic aberrations in pediatric AML. Trisomy 8 positive AML is a heterogeneous group and the majority of cases have additional cytogenetic aberrations. Patients with +8 alone differed from patients with +8 other and were associated with older age, FAB M2, and FLT3-ITD aberrations. There were no differences in survival despite the more frequent occurrence of FLT3-ITD in +8 alone. © 2016 Wiley Periodicals, Inc.

Unravelling the relevance of CLEC12A as a cancer stem cell marker in myelodysplastic syndrome.

Evidence of distinct disease propagating stem cells in myelodysplastic syndrome (MDS) has emerged in recent years. However, immunophenotypic characterization of these cancer stem cells remains sparse. In acute myeloid leukaemia (AML), we have previously described aberrant expression of the C-type lectin domain family 12, member A (CLEC12A) as a stable and reliable marker of leukaemia blasts and as a tool for assessing minimal residual disease. Furthermore, CLEC12A has been proposed as a promising marker of leukaemic stem cells in AML. The role of CLEC12A in MDS, however, remains to be elucidated. In this study, we found CLEC12A aberrantly expressed on the CD34+ CD38- cell compartment in 71% (22/31) of MDS patients, distributed across all Revised International Prognostic Scoring System risk groups. We showed that the CD34+ CD38- CLEC12A+ cells were indeed malignant and possessed functional stem cell properties in the long-term colony-initiating cell assay. As opposed to reported findings in AML, we showed that cancer stem cells from MDS samples derived from both CLEC12A positive and negative CD34+ CD38- subpopulations. Due to the absence of CLEC12A on normal haematopoietic stem cells, CLEC12A stem cell immunophenotyping may contribute to diagnosing and monitoring MDS patients and could furthermore add knowledge about disease propagating cells in MDS.

Oligo-based aCGH analysis reveals cryptic unbalanced der(6)t(X;6) in pediatric t(12;21)-positive acute lymphoblastic leukemia.

Secondary chromosomal aberrations are necessary for development of overt leukemia in t(12;21)/ETV6-RUNX1-positive acute lymphoblastic leukemia (ALL). Conventional cytogenetic analysis supplemented with locus-specific FISH analyses is gold standard to detect important clonal aberrations in this disease group. However, adequate chromosome banding analysis may often be hampered by poor chromosome morphology and banding patterns in pediatric ALL cases, which may hinder identification of possible clinical important additional chromosomal aberrations. We used oligo-based high-resolution aCGH (oaCGH) analysis as an adjunct tool to enhance conventional cytogenetic analysis in pediatric acute B-cell lymphoblastic leukemia in a prospective single center study during a 4-year period (2012-2015). In a consecutive series of 45 pediatric B-ALLs, we identified eight patients with t(12;21)/ETV6-RUNX1 fusion by FISH analysis. In three of the patients, oaCGH analysis revealed concurrent Xq duplication and 6q deletion, which was cryptic by G-banded analysis. FISH analyses with whole chromosome painting probes confirmed the imbalances and showed an unbalanced translocation der(6)t(X;6) in all three patients. A search in the literature revealed two additional pediatric patients with cryptic der(6)t(X;6) in t(12;21)-positive ALLs. No common break points on Xq or 6q could be determined between the five patients. This study highlights the importance of oaCGH analysis as an adjunct cytogenetic tool to detect cryptic chromosomal aberrations. Further, the study adds to understanding the full spectrum of secondary chromosomal aberrations in the very common t(12;21)-positive pediatric ALL disease group. We suggest that the unbalanced der(6)t(X;6), which is cryptic to conventional cytogenetics, is a non-random secondary event in this disease group. It might be that the specific combination of concurrent Xq duplication and 6q-deletion results in gain of possible oncogenes on Xq and loss of possible tumor suppressor genes on 6q that are important for the leukemic propagation of t(12;21)-positive hematopoietic cells in a subset of ALLs.

Acute Lymphoblastic Leukemia Presenting With Pancytopenia Followed by a 14-Month-Long Period of Transient Remission Possibly Supporting the Adrenal Hypothesis of Leukemogenesis.

A small group of children with acute lymphoblastic leukemia (ALL) have a preleukemic phase of pancytopenia followed by a period of spontaneous remission before the diagnosis (pre-ALL). A 6-year-old girl presented with pancytopenia, fever, and myelodysplasia. Following transient remission pre-B ALL was diagnosed 14 months later. Clonal B-lineage blasts at the period of pancytopenia were identified retrospectively. The interval between pre-ALL and ALL-diagnosis was longer than previously reported. The infection was clinically severe and might have induced a significant endogenous corticosteroids production resulting in the long-lasting remission. The case supports the adrenal and the Coley's toxin hypothesis in leukemogenesis.

Nature and nurture: a case of transcending haematological pre-malignancies in a pair of monozygotic twins adding possible clues on the pathogenesis of B-cell proliferations.

We describe a comprehensive molecular analysis of a pair of monozygotic twins, who came to our attention when one experienced amaurosis fugax and was diagnosed with JAK2+ polycythaemia vera. He (Twin A) was also found to have an asymptomatic B-cell chronic lymphocytic leukaemia (B-CLL). Although JAK2-, Twin B was subsequently shown to have a benign monoclonal B-cell lymphocytosis (MBL). Flow cytometric and molecular analyses of the B-cell compartments revealed different immunoglobulin light and heavy chain usage in each twin. We hypothesized that whole exome sequencing could help delineating the pattern of germline B-cell disorder susceptibility and reveal somatic mutations potentially contributing to the differential patterns of pre-malignancy. Comparing bone marrow cells and T cells and employing in-house engineered integrative analysis, we found aberrations in Twin A consistent with a myeloid neoplasm, i.e. in TET2, RUNX1, PLCB1 and ELF4. Employing the method for detecting high-ranking variants by extensive annotation and relevance scoring, we also identified shared germline variants in genes of proteins interacting with B-cell receptor signalling mediators and the WNT-pathway, including IRF8, PTPRO, BCL9L, SIT1 and SIRPB1, all with possible implications in B-cell proliferation. Similar patterns of IGHV-gene usage to those demonstrated here have been observed in inherited acute lymphoblastic leukaemia. Collectively, these findings may help in facilitating identification of putative master gene(s) involved in B-cell proliferations in general and MBL and B-CLL in particular.

The applicability of the WHO classification in paediatric AML. A NOPHO-AML study.

The World Health Organization (WHO) classification of myeloid leukaemia was revised in 2008. It incorporates newly recognized entities and emphasizes the pivotal role of cytogenetic abnormalities. The aim of this study was to evaluate the usability of the WHO classification when applied to a large population-based paediatric acute myeloid leukaemia (AML) cohort. We included children diagnosed with de novo AML, 0-18 years of age from the Nordic countries and Hong Kong from 1993 to 2012. Data were retrieved from the Nordic Society for Paediatric Haematology and Oncology AML database and patients classified according to the WHO 2008 classification. A successful karyotype was available in 97% of the cases. AML with recurrent genetic abnormalities were present in 262 (41%) and 94 (15%) were classified as AML with myelodysplasia-related changes (AML-MDS). WHO classifies patients with monosomy 7 and del(7q) into one group. We found that -7 (n = 14) had significantly poorer outcome than del(7q) (n = 11); 5-year event-free survival 26% vs. 67%, (P = 0·02), and 5-year overall survival 51% vs. 90%, (P = 0·04). The largest group was the highly heterogeneous AML not otherwise specified (NOS) (n = 280) (44%). In conclusion, the WHO classification allocated 15% to AML-MDS, 44% to NOS and grouped together entities with clearly different outcome, therefore limiting the applicability of the current WHO classification in children with AML.

A novel acquired cryptic three-way translocation t(2;11;5)(p21.3;q13.5;q23.2) with a submicroscopic deletion at 11p14.3 in an adult with hypereosinophilic syndrome.

Hypereosinophilic syndrome (HES) is a clinically and pathologically heterogeneous disease entity. It is characterized by persistent eosinophilia and organ damage after excluding other causes. Clonal eosinophilia is distinguished from idiopathic eosinophilia by the presence of histologic, cytogenetic, or molecular evidence of an underlying malignancy. There are two distinct subcategories of clonal eosinophilia: chronic eosinophilic leukemia, not otherwise specified and myeloid/lymphoid neoplasms with eosinophilia and mutations involving platelet-derived growth factor receptor α/ß or fibroblast growth factor receptor 1. More than 50% of HES are without knowledge of underlying pathogenic molecular pathways. Here we examined a HES patient by oligo-based aCGH analysis and molecular cytogenetic methods. Examination for the common eosinophilia-related cytogenetic abnormalities involving the genes PDGFRA, PDGFRB, and FGFR1 together with BCR-ABL fusion gene was negative. Cytogenetic analysis and multi-color FISH analysis revealed a novel cryptic three-way translocation t(2;11;5)(p21.3;q13.5;q23.2). By oaCGH analysis we could not find any copy number changes related to the cytogenetic breakpoints but instead detected a 0.9Mb submicroscopic deletion at 11p14.3. The deleted region involved the 5'-upstream sequences and exons 1-4 of the LUZP2 gene, which encodes a leucine zipper protein. Analysis of surrogate germ-line cells revealed a normal result showing that the detected chromosomal aberrations were acquired. This is the first report on a HES patient associated with a novel complex three-way translocation t(2;11;5)(p21.3;q13.5;q23.2) and a submicroscopic deletion in chromosome band 11p14.3. The study also demonstrates the benefits of oligo-based aCGH analysis in detecting hidden disease related chromosomal abnormalities. The present findings provide additional clues to unravel important molecular pathways in HES to obtain the full spectrum of acquired chromosomal and genomic aberrations in this heterogeneous disease entity. As more cases become characterized this may eventually improve on classification and treatment options.

Treatment-related myelodysplastic syndrome in a child with acute myeloid leukemia and TPMT heterozygosity.

INTRODUCTION: We describe a patient diagnosed with acute myeloid leukemia (AML) and low activity of thiopurine methyltransferase (TPMT) who developed secondary myelodysplastic syndrome after treatment. OBSERVATION: A 10-year-old boy presented with AML-M2 with t(8;21)(q22;q22) and genotyping revealing 3*B TPMT heterozygosity. The patient was treated according to the NOPHO-AML 2004 protocol. Two years after the treatment, the patient presented with neutropenia and thrombocytopenia. Bone marrow, including fluorescent in situ hybridization and retrospective aCGH analysis, verified therapy-related myelodysplastic syndrome with ring chromosome 6. DISCUSSION: The clinical course of this patient raises the possibility that low-activity TPMT genotypes may influence 6TG toxicity in patients with AML and lead to an increased risk of developing secondary malignant neoplasms.