Secondary Chromosomal Aberrations Research Articles

Molecular basis of multiple myeloma.

Multiple myeloma (MM) is aheterogeneous hematological malignancy characterized by clonal expansion of malignant plasma cells in the bone marrow. The disease is accompanied by various clinical manifestations, such as bone lesions, anemia, hypercalcemia, and renal insufficiency. However, despite significant advances in treatment over the last two decades, the disease remains challenging to treat, and most patients relapse. Although its pathogenesis has not yet been elucidated, it is clear that genomic instability plays akey role in its develop-ment or resistance to treatment. In some instances, the cause of this instability is chromothripsis, aform of complex genomic rearrangement that involves shattering and subsequent haphazard reassembly of chromosomes within asingle catastrophic event. The resulting rearrangements involve avariety of structural changes, including deletions, duplications, inversions, and translocations, that lead to genome disruption. Specifically, these changes may result in alteration or inactivation of tumor suppressor genes (TP53and CDKN2C), activation of oncogenes (MAF, FGFR3, and CCND1) or genes involved in key cellular processes. Unraveling the mechanisms that result in chromothripsis provides opportunities to identify critical genes and pathways involved in MM pathogenesis. These findings may serve as abasis for improved dia-gnostic approaches. The goal of this review is to summarize the common primary and secondary chromosomal aberrations in MM with a particular focus on introducing complex chromosomal aberrations, especially chromothripsis in MM.

EBV and 1q Gains Affect Gene and miRNA Expression in Burkitt Lymphoma.

Abnormalities of the long arm of chromosome 1 (1q) represent the most frequent secondary chromosomal aberrations in Burkitt lymphoma (BL) and are observed almost exclusively in EBV-negative BL cell lines (BL-CLs). To verify chromosomal abnormalities, we cytogenetically investigated EBV-negative BL patient material, and to elucidate the 1q gain impact on gene expression, we performed qPCR with six 1q-resident genes and analyzed miRNA expression in BL-CLs. We observed 1q aberrations in the form of duplications, inverted duplications, isodicentric chromosome idic(1)(q10), and the accumulation of 1q12 breakpoints, and we assigned 1q21.2-q32 as a commonly gained region in EBV-negative BL patients. We detected MCL1, ARNT, MLLT11, PDBXIP1, and FCRL5, and 64 miRNAs, showing EBV- and 1q-gain-dependent dysregulation in BL-CLs. We observed MCL1, MLLT11, PDBXIP1, and 1q-resident miRNAs, hsa-miR-9, hsa-miR-9*, hsa-miR-92b, hsa-miR-181a, and hsa-miR-181b, showing copy-number-dependent upregulation in BL-CLs with 1q gains. MLLT11, hsa-miR-181a, hsa-miR-181b, and hsa-miR-183 showed exclusive 1q-gains-dependent and FCRL5, hsa-miR-21, hsa-miR-155, hsa-miR-155*, hsa-miR-221, and hsa-miR-222 showed exclusive EBV-dependent upregulation. We confirmed previous data, e.g., regarding the EBV dependence of hsa-miR-17-92 cluster members, and obtained detailed information considering 1q gains in EBV-negative and EBV-positive BL-CLs. Altogether, our data provide evidence for a non-random involvement of 1q gains in BL and contribute to enlightening and understanding the EBV-negative and EBV-positive BL pathogenesis.

Ring Chromosome and Clinical Findings: Reports Cases of 4 Different Chromosomes in Beninese Population

Ring chromosome is a disorder in which one or both ends of chromosome are lost and joined, so they could show a ring-shaped structure. Patients with ring chromosome could therefore present with features of deletion of long or short arms of the chromosome syndromes or a combination of both. Phenotypic of these individuals depends on the size of the ring chromosome, amount of genetic material lost in breakage, the stability of the ring chromosome and the presence of secondary chromosomal aberrations including the varying degrees of mosaicism. Ring chromosomes accounts for a very low percentage of structural chromosomal abnormalities but could lead to a major clinical concern and complicated genetic counseling. Practitioner awareness must be permanently raised up to help in managing with efficacy patient with ring condition. We report here 4 cases of ring on chromosome 4, 9, 15 and X. We described their clinical finding and draw attention on common key signs that were present in the reported cases and also discussed recurrence risk.

Analyzing the Transcriptome Discovers up-Regulation of HOXA Genes in Patients with Myeloid Neoplasms and Isochromosome 17q and Mutations in ASXL1, SETBP1 and SRSF2

Introduction: Isochromosome 17 (i(17q)) is a rare cytogenetic abnormality reported in different myeloid neoplasms. I(17q) has been described as primary and as secondary chromosomal aberration, often acquired in the disease course. Recently, we have shown that patients with i(17q) show a distinct mutation profile with mutations in ASXL1, SETBP1 and SRSF2. Further data suggested a parallel acquisition of SETBP1 mutation and i(17q) (Meggendorfer et al., Leukemia, 2016). Of note, i(17q) results in three copies of the splicing factor SRSF2, potentially further influencing the transcriptome of affected cells.Aim: To characterize the transcriptome in myeloid neoplasms with i(17q) and the typical mutations in ASXL1, SETBP1 and SRSF2 (A/S/S/i17pos).Patients and Methods: In total 18 patients were selected based on the cytogenetic profile and the molecular mutations. All had the diagnosis of a myeloid neoplasm by cytomorphology according to the WHO. Chromosome banding and FISH analysis and mutation status of ASXL1, SETBP1 and SRSF2 was available in all cases. Three patient groups were defined: 1) ASXL1, SETBP1, SRSF2 mutated and a normal karyotype (A/S/S/-pos; n=5) and gain of i(17q) during follow up, 2) ASXL1, SETBP1, SRSF2 mutated and i(17q) as sole cytogenetic abnormality (A/S/S/i17pos; n=8), 3) ASXL1, SRSF2 mutated and i(17q) as sole cytogenetic abnormality (A/-/S/i17pos; n=5). In all cases RNA sequencing was performed (TruSeq RNA Sample Preparation V2, Illumina, San Diego, CA). A control RNA (Universal Human Reference RNA, Agilent Technologies, Santa Clara, CA) was investigated in triplicate for normalization and comparison. Expression analyses were performed with BaseSpace RNA Express app (Illumina, San Diego, CA).Results: In total 23,710 genes were annotated by RNA sequencing and at least 14,773 analyzed for differential expression, showing that all three patient groups show aberrant expression in comparison to the control RNA. In mean 4,930 genes/group (range: 3,603-6,711) were differentially expressed. The differential expression ranged from -12.7 to 11.2 log2(fold change). Comparing the two groups with all three gene mutations but different i(17q) status (A/S/S/-pos and A/S/S/i17pos) showed that the presence of i(17q) changes the expression pattern with 1,596/13,218 assessed genes differentially expressed. In detail, in A/S/S/i17pos cases 790 genes were significantly over expressed while 806 genes showed reduced expression compared to A/S/S/-pos, ranging from -2.84 to 2.78 log2(fold change). The expression of SRSF2 was not affected by i(17q), although i(17q) cases show three SRSF2 gene copies. Analyzing the most strongly affected genes (2<log2(fold change)<-2, n=48) showed that differential gene expression affected mostly the homeobox (HOX) genes clustering on chromosome 7p15 (HOXA1, HOXA5 and HOXA7) as well as MEIS1, an important cofactor of HOX genes. HOX genes represent a family of transcription factors, shown to be involved in hematopoiesis. Addressing specifically the differential expression of HOX genes showed that further 4 HOXA genes (HOXA2, HOXA4, HOXA9, HOXA10) and 3 HOXB genes (HOXB2, HOXB3, HOXB4) were significantly dysregulated, with HOXB clustering on 17q21. The expression of all HOX genes was up-regulated in cases with i(17q). Interestingly, the molecular mutation pattern A/S/Spos has also been shown to associate with patients having a monosomy 7 (Meggendorfer, #1364, ASH 2013), where the HOXA gene cluster is located. Comparing the HOXA and MEIS1 gene expression in all 18 samples to human control RNA revealed a significant lower expression level in A/S/S/-pos and an increased one in A/S/S/i17pos and A/-/S/i17pos patients, clearly differentiating i(17q) carrying patients. However, the additional SETBP1 mutation did not influence the expression pattern as seen by comparing A/S/S/i17pos and A/-/S/i17pos patients (0/13,398 assessed genes differentially expressed).Conclusion: 1) Transcriptome analysis of patients with myeloid malignancies, i(17q) and mutations in ASXL1, SETBP1 and SRSF2 show an up-regulation of HOXA genes. 2) Accompanying SETBP1 mutation does not further influence the transcriptome of A/-/S/i17pos patients. 3) The up-regulation of HOXA genes might indicate a pathogenic mechanism in patients with ASXL1, SETBP1, SRSF2 and i(17q). However, this finding has to be validated in a larger cohort and with an independent method. DisclosuresMeggendorfer:MLL Munich Leukemia Laboratory: Employment. Nadarajah:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Concurrent Amplification of MYC and 1q21 in Multiple Myeloma: Focal and Segmental Jumping Translocations of MYC

IntroductionMultiple myeloma (MM) is characterized by an accumulation of secondary chromosome aberrations which lead to cytogenetically heterogeneous subpopulations of cells in the subclonal progression of this disease. Copy number aberrations (CNAs) represent a large proportion of these aberrations and include both numerical and structural chromosome aberrations which involve unbalanced translocations, amplifications, insertions, and deletions.Secondary MYC translocations are thought to play a role in driving the transition from MGUS to MM, and during tumor progression additional secondary CNAs of both MYC (8q24) and 1q21 are found in relapsed patients. When CNAs are taken into account the percentage of myeloma cases where MYC is deregulated is 55%, making it the most common genetic event in MM (Walker B. et al., Nature Comm, 2015). In fact, high resolution SNP arrays have shown that somatic CNAs of MYC and 1q21 are two of the top ten CNAs in all cancers (Beroukhim R. et al., Nature, 2010). Two types of amplification predominate by SNPs array, either large arm-length amplifications (25% of the genome) or small focal CNAs (10% of the genome). Unfortunately, the origins of the complex structural chromosomal aberrations which underlie these types CNAs have not been well characterized in MM.To better understand the possible relationship between MYC and 1q21 CNAs we undertook a comprehensive metaphase cytogenetic analysis of 26 diagnostic specimens showing concurrent MYC and 1q21 CNAs by G-banding.MethodsLocus specific FISH probes and Spectral karyotyping were used to define and follow the progression of aberrations occurring in these two regions. Locus specific FISH probes for selected regions of chromosomes 1 and 8 pericentromeric regions and the regions surrounding 1q21 and 8q24 were utilized.ResultsThree primary aberration patterns were observed:The most frequent pattern involved copy number gains in both regions, apparently occurring independently of each other (sixteen patients).The second most frequent pattern showed unbalanced segmental jumping translocations (SJTs) of 8q and the MYC locus to different receptor chromosomes. These unbalanced translocations of MYC were found in seven patients involving varying sized segments of 8q, and included both intra and inter-chromosomal translocations. Surprisingly, three patients in this group showed clones with the co-amplification of MYC and 1q21 on the same derivative chromosome, where 8q and MYC were in essence piggybacking on jumping translocations of 1q12 (JT1q12) to receptor chromosomes.Finally, the third and most complex structural aberration pattern involved the breakage-fusion-bridge cycle mechanism, which results in focal amplifications of genes. This mechanism typically results from telomere shortening and loss and subsequent formation of dicentric chromosomes. Evidence of dicentric chromosomes 8 and the breakage fusion break amplification of MYC was identified in three patients and, strikingly, in one case was found to be initiated by a JT1q12 to 8qter. Therefore, this case identifies a novel alternative mechanism for the focal amplification of the MYC locus whereby the JT1q12 initiates sister chromatid fusion at 8q24.ConclusionWe demonstrate for the first time the mechanistic coupling of MYC and 1q21 amplifications involving sequential jumping translocations of 8q and JT1q12s. These findings provide evidence for the origin of both arm-length and focal amplifications of MYC, and that these aberrations can co-evolve in the same clones. The concurrent amplification of MYC and 1q21 suggests pericentromeric instability, and to a lesser extent telomeric instability, play a role in driving CNAs of both of these genomic lesions in MM. DisclosuresDavies:Celgene: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Janssen: Consultancy, Honoraria. Morgan:Univ of AR for Medical Sciences: Employment; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Bristol Meyers: Consultancy, Honoraria; Janssen: Research Funding.

Characterization of a novel acquired der(1)del(1)(p13p31)t(1;15)(q42;q15) in a high risk t(12;21)-positive acute lymphoblastic leukemia

The t(12;21)(p13;q22) with ETV6-RUNX1 fusion occurs in 25% of cases of B-cell precursor acute lymphoblastic leukemia (BCP-ALL); and is generally associated with favorable prognosis. However, 15–20% of the t(12;21)-positive cases are associated with high-risk disease due to for example slow early responses to therapy. It is well-known that development of overt leukemia in t(12;21)-positive ALL requires secondary chromosomal aberrations although the full spectrum of these cytogenetic alterations is yet unsettled, and also, how they may be associated with disease outcome. This report describes the case of an adolescent male with t(12;21)-positive ALL who displayed a G-banded karyotype initially interpreted as del(1)(p22p13) and del(15)(q15). The patient was treated according to NOPHO standard risk protocol at diagnosis, but had minimal residual disease (MRD) at 6,4% on day 29 as determined by flow cytometric immunophenotyping. Because of MRD level>0.1% he was then assigned as a high risk patient and received intensified chemotherapy accordingly. Further molecular cytogenetic studies and oligo-based aCGH (oaCGH) analysis characterized the acquired complex structural rearrangements on chromosomes 1 and 15, which can be described as der(1)del(1)(p13.1p31.1)t(1;15)(q42;q15) with concurrent deletions at 1q31.2-q31.3, 1q42.12-q43, and 15q15.1-q15.3. The unbalanced complex rearrangements have not been described previously. Extended locus-specific FISH analyses showed that the three deletions were on the same chromosome 1 homologue that was involved in the t(1;15), and that the deletion on chromosome 15 also was on the same chromosome 15 homologue as involved in the t(1;15). Together these findings show the great importance of the combined usage of molecular cytogenetic analyses and oaCGH analysis to enhance characterization of apparently simple G-banded karyotypes, and to provide a more complete spectrum of secondary chromosomal aberrations in high risk t(12;21)-positive BCP-ALLs.

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.

Molecular Cytogenetic Analysis of Chromosome 8 Aberrations in Patients With Multiple Myeloma Examined in 2 Different Stages, at Diagnosis and at Progression/Relapse.

The genome of multiple myeloma (MM) clonal plasma cells is characterized by genetic changes of prognostic importance. Disease progression is accompanied by a number of secondary chromosomal aberrations including chromosome 8. We focused on the detection of chromosome 8 aberrations in patients with MM who were examined at 2 different phases: diagnosis and progression/relapse. A total of 62 patients with MM were examined at the time of diagnosis and at relapse/progression. The median age was 64 years (range, 39-78 years); the study included 29 males and 33 females. We analyzed bone marrow samples for detecting aberrations on chromosome 8 by the fluorescence immunophenotyping and interphase cytogenetics as a tool for the investigation of neoplasms (FICTION) and fluorescence in situ hybridization methods with specific probes. Chromosome 8 aberrations were detected in 24 (38.7%) patients at diagnosis and in 29 (46.8%) patients at progression/relapse. Only 5 (8%) patients developed additional chromosome 8 changes at progression/relapse. The aberrations were heterogeneous, involving numerical and structural changes of the MYC gene. Aberrations of the short arm of chromosome 8, involving the genes TRAIL-R1/-R2, were less frequent (4 of 62 patients, 6.4%). All aberrations of chromosome 8 were accompanied with additional changes and with an advanced clinical phase of the disease. This finding significantly influenced the overall survival of patients. In the current study, chromosome 8 aberrations were highly heterogeneous, were presented at diagnosis in patients with advanced clinical stage, and were associated with worse overall survival. We have not confirmed the increase of frequency aberration of chromosome 8 in disease progression. The findings demonstrate the importance of fluorescence in situ hybridization examination of chromosome 8 in newly diagnosed patients with MM.

Genes encoding members of the JAK-STAT pathway or epigenetic regulators are recurrently mutated in T-cell prolymphocytic leukaemia.

T-cell prolymphocytic leukaemia (T-PLL) is an aggressive leukaemia. The primary genetic alteration in T-PLL are the inv(14)(q11q32)/t(14;14)(q11;q32) leading to TRD/TRA-TCL1A fusion, or the t(X;14)(q28;q11) associated with TRD/TRA-MTCP1 fusion. However, additional cooperating abnormalities are necessary for emergence of the full neoplastic phenotype. Though the pattern of secondary chromosomal aberrations is remarkably conserved, targets of the changes are largely unknown. We analysed a cohort of 43 well-characterized T-PLL for hotspot mutations in the genes JAK3, STAT5B and RHOA. Additionally, we selected a subset of 23 T-PLL cases for mutational screening of 54 genes known to be recurrently mutated in T-cell and other haematological neoplasms. Activating mutations in the investigated regions of the JAK3 and STAT5B genes were detected in 30% (13/43) and 21% (8/39) of the cases, respectively, and were mutually exclusive. Further, we identified mutations in the genes encoding the epigenetic regulators EZH2 in 13% (3/23), TET2 in 17% (4/23) and BCOR in 9% (2/23) of the cases. We confirmed that the JAK-STAT pathway is a major mutational target, and identified epigenetic regulators recurrently mutated in T-PLL. These findings complement the mutational spectrum of secondary aberrations in T-PLL and underscore the potential therapeutical relevance of epigenetic regulators in T-PLL.

The Landscape of Myeloid Neoplasms with Isochromosome 17q Discloses a Specific Mutation Profile and Is Characterized By an Accumulation of Prognostically Adverse Molecular Markers

Introduction: Isochromosome 17 (i(17q)) is a rare cytogenetic abnormality resulting in the loss of the short arm and the duplication of the long arm of chromosome 17. i(17q) has been reported in different myeloid neoplasms like acute myeloid leukemia (AML), chronic myeloid leukemia (CML), myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), MDS/MPN overlap, as well as in Hodgkin- and non-Hodgkin-lymphoma. i(17q) has been described both as primary and as secondary chromosomal aberration. In myeloid neoplasms i(17q) as sole abnormality is suggested to define a distinctive clinicopathological entity with a high risk to leukemic progression and poor prognosis. So far, however, it is only briefly mentioned in the WHO classification.Aim: To comprehensively characterize the molecular features of patients with myeloid neoplasms and i(17q).Patients and Methods: Patients were selected by the presence of i(17q) and diagnosis of a myeloid neoplasm. Philadelphia positive CML were excluded. The cohort comprised 62 cases, 47 males and 15 females with a median age of 69 years (range: 30 - 87 years). Classification of all cases was performed by cytomorphology on peripheral blood and/or bone marrow smears according to the WHO. Chromosome banding and FISH analysis were performed in all cases. 19/27 cases with sole i(17q) were additionally analyzed by array CGH. All 62 samples were analyzed by next generation sequencing using a 29-gene panel targeting ASXL1, BCOR, BRAF, CALR, CBL, CSF3R, DNMT3A, ETV6, EZH2, FLT3-TKD, GATA1, GATA2, IDH1, IDH2, JAK2, KIT, KRAS, MPL, NPM1, NRAS, PTPN11, RUNX1, SETBP1, SF3B1, SRSF2, TET2, TP53, U2AF1, and WT1. Variants of unknown significance were excluded from statistical analyses (n=14).Results: Following WHO classification four of the 62 patients were diagnosed as MPN, 13 as MDS/MPN overlap, 24 as MDS, and 21 as AML. 27 cases showed i(17q) as sole abnormality, while 23 cases showed additional chromosome aberrations, and eight even a complex karyotype (>3 aberrations). Further four cases had two independent cell clones, with one harboring the sole i(17q) abnormality. Array CGH revealed that in 15/19 cases i(17q) was the only abnormality, while four patients showed additional aberrations (1-3 per patient): loss of 7p, 7q, 12p, gain of 13q, and CN-LOH 19p and 22q (n=2). The comprehensive mutational analyses revealed only 3/62 patients carrying no mutation, while a median of 3 mutations per patient was observed (range 0-6). The three most frequently mutated genes were ASXL1 (66%, 41/62), SRSF2 (65%, 40/62), and SETBP1 (48%, 30/62) with no association to any WHO entity, indicating the presence of this genetic profile also across entities beyond the expected overlap between different neoplasms. Following genes showed mutation frequencies >10%: TET2 (24%), ETV6 (16%), CBL (13%), TP53 (15%), RUNX1 (11%), and NRAS (10%), all genes known for adverse prognostic impact. Interestingly, mutations in the three most frequently mutated genes ASXL1, SRSF2, and SETBP1 often co-occurred (n=21) and ASXL1 and SRSF2 were rarely mutated alone (n=9; n=5), while SETBP1 was even never mutated solely, indicating acquirement of SETBP1 mutations during disease course. Therefore, SETBP1 mutations associated significantly with mutations in ASXL1 as well as SRSF2 (24/41 vs 6/21 in ASXL1 wild type (wt), p=0.033; 27/40 vs 3/22 in SRSF2 wt, p<0.001). Furthermore, mutations in ASXL1 associated significantly with i(17q) sole in comparison to cases with additional chromosomal aberrations (22/27 vs 19/35, p=0.032). Therefore, also cases harboring mutations in all three genes ASXL1, SRSF2, and SETBP1 associated with sole i(17q) (13/27 vs 8/35, p=0.058), indicating that these three mutations might be drivers of disease pathogenesis in this cytogenetic background. Reviewing the bone marrow morphology showed characteristic pseudo-Pelger-Huet anomaly in 36 of 59 (61%) analyzed smears. These changes were not associated with the cytogenetic profile, but showed a trend towards co-occurrence with ASXL1 mutations (27/39 vs 9/20 ASXL1 wt p=0.094).Conclusion: 1) Myeloid neoplasms with i(17q) show a distinct molecular mutation pattern, accumulating prognostically adverse mutations. 2) Patients with sole i(17q) show co-occurring mutations in ASXL1, SRSF2, and SETBP1. 3) Frequency and co-existence of ASXL1, SRSF2, and SETBP1 mutations predispose these as driver mutations. DisclosuresMeggendorfer:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Downregulation of DLEU1 Significantly Shortened Survival in a Rituximab-Treated DLEU1 Knockout Human Burkitt Lymphoma (BL) Xenograft NSG Mouse Model: DLEU1 May Act As a Tumor Suppressor Gene in Pediatric BL

BACKGROUND: Burkitt lymphoma (BL) is the most common histological subtype of non-Hodgkin lymphoma (NHL) in children and adolescents (Cairo et al., Blood, 2007; Miles/Cairo, BJH, 2012). We have previously identified secondary chromosomal aberrations in 70% of pediatric BL patients (PBL) with a C-MYC gene rearrangement (Poirel/Cairo et al., Leukemia, 2009). Specifically, we identified significantly inferior event free survival (EFS) and overall survival in children and adolescents with a specific loss of the 13q14.3 locus (Poirel/Cairo et al., Leukemia, 2009; Nelson/Cairo/Sanger et al., Br. J. Haematol., 2009). In a multivariate analysis controlling for stage, lactate dehydrogenase levels, country of treatment, and group classification, children with BL who had a 13q deletion had significantly poorer EFS compared to the remainder of patients treated with the same French-American-British (FAB) chemotherapy regimen (Poirel/Cairo et al., Leukemia, 2009). Deleted in lymphocytic leukemia 1 (DLEU1) is a BL classifier gene in the 13q14.3 region (Dave et al., NEJM, 2006) and interacts with C-MYC, Tubulin beta-2C chain (TUBB2C), E3 ubiquitin-protein ligase (UBR1), cellular tumor antigen p53, and Ras association (RalGDS/AF-6) domain family member 1 (RASSF1) (Stelzl et al., Cell, 2005). The sequence-specific Transcription Activator-Like Effector Nucleases (TALENs) have been developed for targeted genome editing in in vitro and in vivo experiments with high efficiency as a new therapeutic tool (Sander et al., Nat. Biotechnol., 2011). We have previously reported a down-regulated DLEU1 mRNA expression significantly associated with an increase in BL proliferation in vitro (Lee/Cairo et al., AACR, 2015). We hypothesize that DLEU1 may have function as a tumor suppressor gene; however, the role of DLEU1 regulating programmed cell death in BL are poorly understood.OBJECTIVES: We hypothesize that DLEU1 may act as a tumor suppressor gene in BL and whether down-regulation of DLEU1 expression results in changes in BL survival following targeted immunotherapy.METHODS: TALENs induced DLEU1 knockout Raji cells were previously generated (Lee/Cairo et al., ASH, 2013) and DLEU1 knockout cells were stably transfected with a firefly luciferase expression plasmid (ffluc-zeo), kindly provided by Laurence Cooper MD, PhD. Four- to six- week-old female NSG (NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ) mice from The Jackson Laboratory were irradiated (2.5 Gy), and then mice were subcutaneously injected with 1x106 ffluc-zeo tumor cells. Tumor burden and tumor progression were monitored by bioluminescence imaging system using the Xenogen IVIS-200 (Caliper Life Sciences). Mice were treated with either PBS, IgG isotype control, rituximab (30 mg/kg) or cyclophosphamide (25 mg/kg) and in combination by intraperitoneal (i.p) injection at 7 day intervals. Survival rates were analyzed by the Kaplan-Meier method and differences evaluated by log-rank test using the Prism Version 6.0 software.RESULTS: There were significant increases of luciferase signal intensity in DLEU1 knockout mice (DLEU1-KO) compared to that in wild type (WT) mice on day 31 of rituximab (p<0.05), cyclophosphamide (p<0.05) or rituximab and cyclophosphamide (p<0.01) combined treatment. Consistent with these initial findings in tumor growth, we found that rituximab-treated DLEU1-KO mice (n=12 per group) had a significantly shortened survival time with a median of 42 days compared to that of WT mice (n=12 per group) (52 days, p<0.005) (Figure 1A). For the rituximab and cyclophosphamide combination treated group, WT mice (n=12 per group) had a significantly extended survival time compared to the DLEU1-KO group (55.5 days vs 48 days, p<0.05) (Figure 1B). There were no significant differences in survival between WT and DLEU1-KO mice with PBS and IgG isotope treatment.CONCLUSIONS: The down-regulation of DLEU1 expression significantly decreased the survival rate in DLEU1-KO xenografted NSG mice following rituximab and in combination with cyclophosphamide treatment. Therefore, the down-regulation of DLEU1 expression in BL may in part result in immunotherapy resistance and may result in a consideration of alternative therapeutic strategies. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Landscape of Secondary Genetic Lesions in Acute Myeloid Leukemia with Inv(16)/CBFB-MYH11

Introduction: Acute myeloid leukemia (AML) with inv(16)(p13q22) or t(16;16)(p13;q22) accounts for 5-7% of adult AML and overall is associated with a favorable outcome. However, secondary genetic lesions have been shown to negatively impact on outcome.Aims: To assess the frequency and clinical impact of additional mutations and chromosomal aberrations in AML with inv(16)/CBFB-MYH11.Patients: We analyzed 138 patients (pts) who were referred to our laboratory for diagnosis of de novo AML between 2005 and 2014 (54 females; 84 males; median age 54 years, range: 20-88 years). All patients were proven to have inv(16)(p13q22) or t(16;16)(p13;q22) /CBFB-MYH11 by a combination of chromosome banding analysis, fluorescence in situ hybridization and RT-PCR. All 138 samples were analyzed by next generation sequencing using a 22-gene panel targeting ASXL1, CBL, DNMT3A, ETV6, EZH2, FLT3-TKD, IDH1, IDH2, KIT, KRAS, NPM1, NRAS, RAD21, RUNX1, SF3B1, SMC1A, SMC3, SRSF2, TET2, TP53, U2AF1, and WT1.Results: In total, 127 pts showed an inv(16)(p13q22), 10 pts a t(16;16)(p13;q22). One pt showed a normal karyotype with a cytogenetically cryptic CBFB-MYH11 rearrangement confirmed by RT-PCR.Using standard chromosome banding analysis, additional cytogenetic aberrations (ACA) were observed in 52 pts (38%). The most frequent secondary chromosome aberrations were +8 (15/52; 29%), +22 (15/52; 29%) and +21 (5/52; 10%). With regard to blood counts, cases with sole inv(16) had significantly elevated white blood cell counts compared to patients with inv(16) and ACA (78x109/L vs 20x109/L; p<0.001).112/138 (81%) pts had at least one mutation in addition to CBFB-MYH11, 47/112 (42%) had at least two additional mutations (maximum: four). Most common were mutations in NRAS (35%), KIT (32%), FLT3-ITD and FLT3-TKD(20%) and KRAS (17%). Mutations in other genes (ASXL1, CBL, DNMT3A, RUNX1, SRSF2, TET2 and WT1) were found in less than 10% of cases. Comparing AML with CBFB-MYH11 withthe other core binding factor AML entity, i.e. AML with RUNX1-RUNX1T1 (Krauth et al., Leukemia 2014), the formershowed a higher incidence of additional mutations (81% vs 50%), however, the landscape of mutated genes was comparable. Solely, the frequency of ASXL1 mutations was higher in RUNX1-RUNX1T1 positive AML compared to CBFB-MYH11 positive AML (12% vs <1%). We additionally analyzed concomitant mutations in CBFB-MYH11 positive AML according to functional pathways. Mutations resulting in activated signaling (FLT3- ITDand FLT3- TKD, KRAS, NRAS, KIT) were identified in the majority of cases (n=107/138; 78%), while mutations of tumor suppressors (CBL, TP53, WT1) were detected in 18/138 cases only (13%). Mutations of myeloid transcription factors (CEBPA, RUNX1, ETV6), mutations of genes that modify the epigenetic status (ASXL1, EZH2, TET2, DNMT3A, IDH1/2 and MLL mutations), mutations of cohesin complex genes (SMC1A, SMC3 and RAD21) and spliceosome genes (SF3B1, U2AF1, SRSF2 and ZRSR2) were identified in less than 10% of cases.There was no difference in frequency and types of additional mutations between patients with inv(16) sole and those with inv(16) and ACA with the exception of WT1 mutations, which were more frequent in patients with inv(16) and ACA (8/51; 16% vs 2/84; 2%; p=0.006).Data regarding the prognostic impact of the concurrent genetic lesions, trisomy 22 and KIT mutations, in CBFB-MYH11 AML are controversial. In our cohort, survival analysis revealed no impact of trisomy 22 or concomitant KIT mutations on prognosis of CBFB-MYH11 AML. However, within patients with inv(16) sole those with concomitant KRAS mutations had a significantly worse overall survival (OS) compared to KRAS wild-type patients (2 year OS: 43% vs 23%; p<0.001).Conclusions:1.Secondary genetic lesions are detected in 91% of inv(16)/CBFB-MYH11 positive AML patients.2.NRAS mutations were the most frequent secondary lesions followed by KIT mutations, FLT3-ITD and FLT3-TKD.3.inv(16)/CBFB-MYH11 positive AML show high frequency of mutations resulting in activated signaling.4.Considering controversial studies, trisomy 22 and concomitant KIT mutations had no prognostic impact in our cohort of 132 inv(16)/CBFB-MYH11 AML cases. The only additional genetic marker with a significant adverse prognostic impact on OS was KRAS mutation. DisclosuresFasan:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Perglerová:MLL2 s.r.o.: Employment. Schindela:MLL Munich Leukemia Laboratory: Employment. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Incidence and Prognostic Relevance of ASXL2 Mutations in Adult CBF-AML with t(8;21)(q22;q22): A Study of the German-Austrian AML Study Group (AMLSG)

Background: The ASXL2 (Additional Sex comb-like 2) gene on chromosome 2p23.3 encodes an epigenetic regulator that is thought to act through histone modification and thereby regulating gene transcription in a context-dependent manner. Recently, ASXL2 mutations (ASXL2mut) were found with a high incidence (~23%) in a cohort of 110 pediatric or adult AML patients (pts) with t(8;21)(q22;q22) (Micol et al., Blood 2014).Aim: We assessed the frequency and prognostic impact of ASXL2mut in the context of other clinical and genetic factors in a large clinically well-defined cohort of intensively treated adults with t(8;21) AML. In addition, the stability of ASXL2 mutation status was analysed in a subset of pts at the time of relapse.Methods: Diagnostic samples from 204 adults with t(8;21);RUNX1/RUNX1T1 -positive AML [median age: 49 years, range: 18-82] were analysed for ASXL2mut in exon 11 and 12 using a combination of PCR-based amplification and subsequent direct DNA-sequencing. Paired samples at diagnosis and relapse were evaluated for the ASXL2 mutation status in a subset of 22 pts. Additional mutation analyses were performed for KIT, FLT3 (ITD and TKD), NRAS, and ASXL1 genes. All pts received intensive treatment either within AMLSG trials (n=155) or according to standard chemotherapy regimens.Results: Thirty four ASXL2mut were identified in 33 (16.2%) of the 204 pts. All mutations (frame-shifts, n=32; non-sense, n=2) created stop codons leading to premature protein truncation with loss of the terminal PHD domain; 27% of the mutations affected codon T740 in exon 12. At diagnosis, there was no significant difference between pts with ASXL2mut and ASXL2 wildtype (ASXL2wt) with respect to sex, WBC, haemoglobin, platelets, LDH serum levels, and circulating or bone marrow blasts. Of note, ASXL2mut were not associated with increasing age, a finding which is commonly observed for ASXL1 mutations in AML. In terms of secondary chromosome aberrations ASXL2mut were frequently associated with del(9q) (P=.006), whereas they never co-occurred with trisomy 8. There was no significant association between ASXL2mut and all other gene mutations analysed. Analysis for ASXL2 mutation status in 22 paired samples obtained at diagnosis and relapse showed a high stability since the mutation was still present in two pts at relapse whereas none of the remaining 20 ASXL2 wildtype cases acquired ASXL2mut. There was no difference in complete remission (CR) rate after double induction between pts with ASXL2mut (88%) and those with ASXL2wt (92%); the same was true when comparing pts with ASXL1 or ASXL2 mutations (ASXL1/2mut) as one group (93%) versus those with ASXL1/2 wildtype. Neither ASXL2mut nor ASXL1/2mut did impact the endpoints event-free-survival, cumulative incidence of relapse, relapse-free and overall survival.Conclusions: Beside KIT and NRAS, ASXL2 is among the most frequently mutated genes in t(8;21) AML. ASXL2mut did not impact achievement of CR or any survival endpoint. Nevertheless, the high incidence (16.2%) of ASXL2mut in t(8;21) AML and the exclusivity to this subgroup of core-binding factor AML implies a peculiar role of ASXL2 in the leukemogenesis of t(8;21) AML providing a basis for further studies. DisclosuresHorst:MSD: Research Funding; Pfizer: Research Funding; Amgen: Honoraria, Research Funding; Gilead: Honoraria, Research Funding; Boehringer Ingleheim: Research Funding. Schlenk:Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Boehringer-Ingelheim: Honoraria; Arog: Honoraria, Research Funding; Teva: Honoraria, Research Funding.

Molecular Characterization of Relapsed Core-Binding Factor (CBF) Acute Myeloid Leukemia (AML)

Background: CBF-AML is defined by recurrent genetic abnormalities which encompass t(8;21)(q22;q22), inv(16)(p13.1q22) or less frequently t(16;16)(p13.1;q22). Most frequent secondary chromosome aberrations in t(8;21) AML are del(9q) or loss of a sex chromosome, and in inv(16)/t(16;16) AML trisomy 22 or trisomy 8. At the molecular level mutations involving KIT, FLT3, or NRAS were identified as recurrent lesions in CBF-AML. However, the underlying genetic alterations which might trigger relapse in CBF-AML are not well delineated. Thus, the aim of our study was to characterize the clonal architecture of relapsed CBF-AML.Methods: We performed mutational profiling (KIT, FLT3-ITD, FLT3-TKD, NRAS, ASXL1) in paired samples obtained at diagnosis and at relapse from 66 adults with CBF-AML [inv(16), n=43; t(8;21), n=23] who all were treated within the AMLSG studies.Results: In inv(16) AML, the following mutation pattern was identified at diagnosis: KIT 13/40 (33%; exon 8, n=6; exon 17, n=5; exon 8+17, n=1; exon 11, n=1; missing data, n=3), NRAS 18/43 (42%), FLT3-TKD 4/43 (9%); none of the pts harboured FLT3-ITD or ASXL1 mutations. At the time of relapse, there was a shift in the mutation pattern in 26 pts (60%): KIT mutations (exon 8, n=5; exon 17, n=2; exon 8+17, n=1) were lost in 8 pts and 1 pt acquired an exon 17 KIT mutation; similarly, 15 pts lost and 1 pt gained NRAS mutation, respectively. Of note, all FLT3-TKD mutations were lost at the time of relapse, and only one pt gained a FLT3-ITD mutation. Based on these findings we calculated the stability in inv(16) AML for KIT, NRAS and FLT3-TKD mutations as 38%, 17%, and 0%, respectively.AML with t(8;21) presented a different diagnostic mutation profile: KIT 9/23 (39%; exon 17, n=8; exon 11, n=1), FLT3 -ITD 3/23 (13%), NRAS 2/23 (9%), and ASXL1 1/23 (4%); there were no FLT3-TKD mutations. At the time of relapse, the mutation pattern changed in 9 pts (39%); KIT mutations were lost in 4 pts (exon 17, n=3; exon 11, n=1), but acquired in 2 pts with both of them located in exon 17; only 1 pt lost the NRAS mutation. FLT3-ITD was lost in 2 and gained in 3 pts. There was no change in the ASXL1 mutation status. Thus, the stability for KIT, NRAS, FLT3-ITD and ASXL1 mutations in t(8;21) AML was calculated as 56%, 50%, 33% and 100%, respectively.Of note, mutations affecting the KIT and NRAS gene were almost mutually exclusive; there were only 3 pts with concurrent KIT and NRAS mutations at diagnosis [inv(16), n=2; t(8;21), n=1].Conclusion: CBF-AML cases display a high degree of molecular heterogeneity with shift of the mutation pattern at relapse in both CBF-AML subtypes. The frequent loss of KIT and NRAS mutations at relapse suggests that there might be other important secondary lesions driving relapse. Ongoing high-resolution genome-wide profiling will further unravel the clonal hierarchy and genomic landscape in CBF-AML. DisclosuresGötze:Novartis: Honoraria; Celgene Corp.: Honoraria. Greil:Celgene: Consultancy; Ratiopharm: Research Funding; Sanofi Aventis: Honoraria; Pfizer: Honoraria, Research Funding; Boehringer-Ingelheim: Honoraria; Astra-Zeneca: Honoraria; GSK: Research Funding; Novartis: Honoraria; Genentech: Honoraria, Research Funding; Janssen-Cilag: Honoraria; Merck: Honoraria; Mundipharma: Honoraria, Research Funding; Eisai: Honoraria; Amgen: Honoraria, Research Funding; Cephalon: Consultancy, Honoraria, Research Funding; Bristol-Myers-Squibb: Consultancy, Honoraria; AOP Orphan: Research Funding; Roche, Celgene: Honoraria, Research Funding. Schlenk:Boehringer-Ingelheim: Honoraria; Teva: Honoraria, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Research Funding; Arog: Honoraria, Research Funding.

Establishment of a molecular cytogenetic analysis for native tumor tissue of meningiomas-suitable for clinical application

BackgroundMeningiomas are mostly benign tumors which arise from the meninges. They are among the cytogenetically best-studied solid tumors, mostly displaying a normal karyotype or, as a typical primary aberration, monosomy of chromosome 22. Further secondary chromosomal aberrations, especially the deletion of chromosome 1p, are correlated with increasing biological aggressiveness up to malignancy. These data are derived from the cytogenetical characterization of 661 meningiomas, from which the genetic progression score (GPS) has been developed. Due to the high expenditure of time and the expert knowledge for the cytogenetical characterization, the aim of this work was to establish an equally reliable yet more rapid clinical diagnosis based on fluorescence in situ hybridization (FISH) on meningiomas. Thus a comparison between the native tumor tissue and the primary culture of the same tumor was done in order to determine the most efficient method for a molecular cytogenetic characterization. The diagnostic procedure has to deliver fast and robust results, since they must enable the attending physician to plan the appropriate follow-up regimens for the patients. All in all, preparations of native tumor tissue as well as preparations of cell culture of 22 meningiomas were tested with FISH for aberrations concerning the prognostically relevant chromosome regions 1p and 9p, and the chromosomes 10, 14, 18 and 22 in comparison with the particular karyotypes revealed by conventional karyotyping using G-banding.ResultsThe FISH examinations between native and cultured cells showed an accordance of 93.4%. The comparison of FISH data and karyotyping presented accordance to the greatest possible extent concerning the chromosomes 14, 18 and 22, but to detect the progression associated losses of 1p and 9p FISH is the most sensitive method.ConclusionsThe raised data reveal that both methods can be used for a significant analysis of chromosome aberrations on meningiomas. As a result of that the complex primary culture could also be avoided. Therefore a clinical diagnosis based on FISH on meningiomas is at hand for the assignment of patients to a suitable follow-up regimen.

Acute Myeloid Leukemia With t(8;21)/RUNX1-RUNX1T1 demonstrate a High Number Of Secondary Genetic Lesions: Frequency and Impact On Clinical Outcome

▪ BackgroundTranslocation t(8;21) with the resulting RUNX1-RUNX1T1 rearrangement is one of the most common chromosomal abnormalities in acute myeloid leukemia (AML). Although it is generally associated with a favourable prognosis, many additional genetic lesions may impact on outcome. AimTo assess the frequency and clinical impact of additional mutations and chromosomal aberrations in AML with t(8;21)/RUNX1-RUNX1T1. MethodsWe analyzed 139 patients (pts) who were referred to our laboratory for diagnosis of AML between 2005 and 2012 (65 females, 74 males; median age 53.3 years, range 18.6 - 83.8 years). All pts were proven to have t(8;21)/RUNX1-RUNX1T1 by a combination of chromosome banding analysis, fluorescence in situ hybridisation and RT-PCR. Analysis of mutations in ASXL1, FLT3-TKD, KIT (D816, exon8-11), NPM1, IDH1 and IDH2, KRAS, NRAS, CBL, and JAK2 as well as of MLL-PTD and FLT3-ITD was performed in all pts. Results107/139 pts were classified according to FAB criteria (77.0%). 34/107 had AML M1 (31.8%) and 73/107 AML M2 (68.2%). 117/139 had de novo AML (84.2%), 22/139 had therapy-related AML (t-AML) (15.8%). 69/139 (49.6%) pts had at least one molecular alteration in addition to RUNX1-RUNX1T1, 23/69 (33.3%) had two or more additional mutations. Most common were mutations (mut) in KIT (23/139; 16.5%), followed by NRAS (18/139; 12.9%) and ASXL1 (16/139; 11.5%). FLT3-ITD and mutations in FLT3-TKD, CBL, and KRAS were found in 4.3% - 5.0% of all pts, whereas mutations in IDH2 and JAK2 were detectable in 3.6% and 2.9%, respectively. IDH1 mutations were found in only 0.7% (1/139). NPM1mut and MLL-PTD were mutually exclusive of RUNX1-RUNX1T1. FLT3-ITD as well as FLT3-TKD were exclusive of ASXL1 mutations. With exception of FLT3-ITD, which was only present in de novo AML, there was no difference in mutation frequencies between de novo AML and t-AML.69.8% (97/139) pts had at least one chromosomal aberration in addition to t(8;21)(q22;q22). Most frequent was the loss of either X- or Y-chromosome (together 46.8%), followed by del(9q) (15.1%), and trisomy 8 (5.8%). FLT3-ITD, FLT3-TKD and trisomy 8 were found to be mutually exclusive. The number of secondary chromosomal aberrations did not differ significantly between pts with de novo AML and t-AML, showing only a trend towards higher frequency of -Y, del(9q), and trisomy 8 in pts with t-AML.Survival was calculated in pts who received intensive treatment (n=111/139, 79.9%; median follow-up 26.9 months; 2-year survival rate 73.4%). With exception of KITD816 mutation, which had a negative impact on overall survival in pts with de novo AML (2-year survival rate 64.2% vs. 82.3%, p=0.03), none of the other 13 mutations significantly influenced outcome, not even in case of 2 or more coexistent mutations. Also, no influence of additional chromosomal aberrations on survival was found.In selected cases (n=21/139), we compared dynamic changes in the patterns of genetic lesions at diagnosis and at relapse. In 14/21 (66.7%) pts the initial molecular mutation pattern changed at relapse. Mutations commonly gained at relapse were KIT mutations (6/21, 28.6%), followed by ASXL1 and IDH1R132 (each 2/21, 9.5%). FLT3-ITD, CBL, NRAS and JAK2 mutations emerged in 1/21 patients (4.8%) each. Loss of a mutation at relapse has been observed in KIT, ASXL1, and NRAS (each 2/21, 9.5%), as well as in KRAS, FLT3-ITD and FLT3-TKD (each 1/21, 4.8%). Concerning chromosomal alterations at relapse, 7/21 pts (33.3%) showed a change of their initial cytogenetic pattern, mostly shifting to a more complex karyotype (gain of chromosomal aberrations: 5/21, 23.8%; loss of chromosomal aberrations: 2/21, 9.5%). In all cases, t(8;21)(q22;q22)/RUNX1-RUNX1T1 remained stable at time of relapse. Conclusions1) 50% of t(8;21)/RUNX1-RUNX1T1 positive pts had at least one additional molecular mutation and almost 70% showed additional chromosomal abnormalities. 2) KIT was the most frequent additional molecular mutation, followed by NRAS and ASXL1. 3) The only additional genetic marker with a significant adverse prognostic impact was KITD816 mutation. Disclosures:Krauth:MLL Munich Leukemia Laboratory: Employment. Eder:MLL Munich Leukemia Laboratory: Employment. Alpermann:MLL Munich Leukemia Laboratory: Employment. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

A novel t(3;12)(q21;p13) translocation in a patient with accelerated chronic myeloid leukemia after imatinib and nilotinib therapy.

The acquisition of secondary chromosomal aberrations in chronic myeloid leukemia (CML) patients with Philadelphia chromosome-positive (Ph+) karyotype signifies clonal evolution associated with the progression of the disease to its accelerated or blastic phase. Therefore, these aberrations have clinical and biological significance. T(3;12)(q26;p13), which is a recurrent chromosomal aberration observed in myeloid malignancies, is typically associated with dysplasia of megakaryocytes, multilineage involvement, short duration of any blastic phase, and extremely poor prognosis. We have identified a recurrent reciprocal translocation between chromosomes 3 and 12 with different breakpoint at bands 3q21 in the malignant cells from a 28-year-old man. The patient was initially diagnosed as having Ph+ CML in the chronic phase. The t(3;12)(q21;p13) translocation occurred 4 years after the patient was first diagnosed with CML while undergoing tyrosine kinase inhibitor therapy. We confirmed the t(3;12)(q21;p13) translocation via fluorescence in situ hybridization assay by using whole-chromosome paint probes for chromosomes 3 and 12. Our findings demonstrate that, similar to other recurrent translocations involving 3q26 such as t(3;3) and t(3;21), the t(3;12)(q21;p13) translocation is implicated not only in myelodysplastic syndrome and acute myeloid leukemia but also in the progression of CML. These findings extend the disease spectrum of this cytogenetic aberration.

Secondary genetic lesions in acute myeloid leukemia with inv(16) or t(16;16): a study of the German-Austrian AML Study Group (AMLSG)

AbstractIn this study, we evaluated the impact of secondary genetic lesions in acute myeloid leukemia (AML) with inv(16)(p13.1q22) or t(16;16)(p13.1;q22); CBFB-MYH11. We studied 176 patients, all enrolled on prospective treatment trials, for secondary chromosomal aberrations and mutations in N-/KRAS, KIT, FLT3, and JAK2 (V617F) genes. Most frequent chromosomal aberrations were trisomy 22 (18%) and trisomy 8 (16%). Overall, 84% of patients harbored at least 1 gene mutation, with RAS being affected in 53% (45% NRAS; 13% KRAS) of the cases, followed by KIT (37%) and FLT3 (17%; FLT3-TKD [14%], FLT3-ITD [5%]). None of the secondary genetic lesions influenced achievement of complete remission. In multivariable analyses, KIT mutation (hazard ratio [HR] = 1.67; P = .04], log10(WBC) (HR = 1.33; P = .02), and trisomy 22 (HR = 0.54; P = .08) were relevant factors for relapse-free survival; for overall survival, FLT3 mutation (HR = 2.56; P = .006), trisomy 22 (HR = 0.45; P = .07), trisomy 8 (HR = 2.26; P = .02), age (difference of 10 years, HR = 1.46; P = .01), and therapy-related AML (HR = 2.13; P = .14) revealed as prognostic factors. The adverse effects of KIT and FLT3 mutations were mainly attributed to exon 8 and tyrosine kinase domain mutations, respectively. Our large study emphasizes the impact of both secondary chromosomal aberrations as well as gene mutations for outcome in AML with inv(16)/t (16;16).

Differential cytogenetic profile in advanced chronic myeloid leukemia with sequential lymphoblastic and myeloblastic blast crisis

Frequency of additional chromosomal abnormalities in chronic myeloid leukemia (CML) is estimated to be 7% in chronic phase and increases to 40–70% in advanced disease. Progression of CML from chronic phase to accelerated phase or blast crisis is often associated with secondary chromosomal aberrations. We report an exceptional case of CML as debut in lymphoblastic blast crisis and a subsequent progression in myeloblastic blast crisis with rare cytogenetic abnormalities.

Molecular characterization of chromosomal band 5p15.33: A recurrent breakpoint region in mantle cell lymphoma involving the TERT–CLPTM1L locus

Secondary chromosomal aberrations may contribute to the development of a malignant phenotype in mantle cell lymphoma. Chromosomal band 5p15.33 represents a new recurrent breakpoint in B-cell malignancies.We present a molecular cytogenetic study of 8 mantle cell lymphoma (MCL) cell lines and 23 patients with MCL to determine and characterize novel secondary aberrations. We detected new secondary recurrent rearrangements in all cell lines and in 7 patients and confirmed 5p15.33 as a recurrent breakpoint in 4 cell lines and one patient. Further molecular characterization by flow-FISH and quantitative RT-PCR suggest TERT and CLPTM1L as target genes of 5p15.33 rearrangements.