Interplay of TP53 allelic state, blast count, and complex karyotype on survival of patients with AML and MDS.

Several clinical and genetic factors impact overall survival (OS) in myelodysplastic neoplasms (MDS) and acute myeloid leukemia (AML), including complex karyotype (CK), TP53 allelic state, and blast count. We analyzed the interplay of these factors by performing Cox regression analysis and by determining the frequency of TP53 single-hit (sh) and double-hit (dh) events and OS in MDS (n = 747) with <5% blasts, with ≥5% but <10% blasts, and ≥10% but <20% blasts and AML (n = 772). MDS with <5% blasts showed the best outcome, followed by with ≥5% but <10% blasts, and ≥10% but <20% blasts, and AML (median OS: 75, 54, 27, and 18 months, respectively). The same hierarchy was observed when each subgroup was divided into TP53sh, TP53dh, and without TP53 alterations (alt), revealing a dismal outcome of TP53dh in all subgroups (17, 10, 8, and 1 month[s], respectively). MDS with <5% blasts differed from the other subgroups by showing predominantly TP53sh (76% of TP53alt cases), and by an independent adverse impact of CK on OS (hazard ratio, 5.2; P < .001). The remaining subgroups displayed many similarities, with TP53dh found at high frequencies (67%, 91%, and 71%, respectively) and only TP53alt but not CK independently influencing OS, and TP53dh showing the strongest influence. When the total cohort was split based on TP53 state, only the blast count and not CK had an independent adverse impact on OS in all subgroups. Thus, TP53dh is the strongest prognostic factor, further supporting its integration into risk stratification guidelines and classification as a separate entity. However, the blast count also influences OS independent of TP53 state, whereas CK plays a minor prognostic role.

Clonal evolution in chronic lymphocytic leukemia is associated with an unmutated IGHV status and frequently leads to a combination of loss of TP53 and TP53 mutation.

BACKGROUND: Chromosomal abnormalities and gene mutations determine the prognosis of patients with chronic lymphocytic leukemia (CLL). Genetic lesions can be acquired by clonal evolution (CE) likely correlating with clinical progression. METHODS AND RESULTS: Samples of 169 CLL patients were analyzed for cytogenetic clonal evolution (CCE) and CE affecting the genes TP53 and SF3B1. Moreover, the mutational status of IGHV and the clinical outcome was evaluated. CCE was observed in 35% of CLL patients. The most frequently gained cytogenetic aberration was a deletion of TP53. Acquired TP53 deletion was more frequent in patients with SF3B1 mutations compared to those without (19% vs. 7%). CCE showed a tendency to occur more frequently in patients with an aberrant karyotype at first investigation than in patients with a normal karyotype. In 73% of patients with CCE (p = 0.002) and 92% of patients with CE affecting the genes TP53 and SF3B1 (p < 0.001) an unmutated IGHV status was present. CCE and CE affecting the genes TP53 and SF3B1 were significantly associated with each other (p < 0.001). In 7% of patients, CE resulted in the co-occurrence of TP53 deletion and TP53 mutation resulting in a significantly shorter overall survival. CONCLUSIONS: The most frequently gained cytogenetic aberration during CCE was a deletion of TP53, which was associated with SF3B1 mutations. Moreover, CCE was associated with an unmutated IGHV status. Our results indicate the importance of re-evaluation of the TP53 status during the course of the disease to ensure correct treatment guidance.

Mutational patterns and their correlation to CHIP-related mutations and age in hematological malignancies.

Acquired somatic mutations are crucial for the development of most cancers. We performed a comprehensive comparative analysis of the mutational landscapes and their correlation with CHIP-related (clonal hematopoiesis of indeterminate potential) mutations and patient age of 122 genes in 3096 cases of 28 different hematological malignancies. Differences were observed regarding (1) the median number of mutations (highest, median n = 4; lowest, n = 0); (2) specificity of certain mutations (high frequencies in atypical chronic myeloid leukemia [aCML; ASXL1, 86%], follicular lymphoma [FL; KMT2D, 87%; CREBBP, 73%], hairy cell lymphoma [BRAF, 100%], lymphoplasmacytic lymphoma [MYD88, 98%; CXCR4, 51%], myeloproliferative neoplasm [MPN; AK2, 68%]); (3) distribution of mutations (broad distribution within/across the myeloid/lymphoid lineage for TET2, ASXL1, DNMT3A, TP53, BCOR, and ETV6); (4) correlation of mutations with patient's age (correlated with older age across entities: TET2, DNMT3A, ASXL1, TP53, EZH2, BCOR, GATA2, and IDH2; younger age: KIT, POT1, RAD21, U2AF2, and WT1); (5) correlation of mutation number per patient with age. Moreover, we observed high frequencies of mutations in RUNX1, SRSF2, IDH2, NRAS, and EZH2 in cases comprising at least 1 DTA (DNMT3A, TET2, ASXL1) mutation, whereas in cases without DTA mutations, TP53, KRAS, WT1, and SF3B1 were more frequent across entities, suggesting differences in pathophysiology. These results give further insight into the complex genetic landscape and the role of DTA mutations in hematological neoplasms and define mutation-driven entities (myelodysplastic syndrome/MPN overlap; secondary acute myeloid) in comparison with entities defined by chromosomal fusions (chronic myeloid leukemia; myeloid/lymphoid neoplasm with eosinophilia).

Clinical application of whole transcriptome sequencing for the classification of patients with acute lymphoblastic leukemia.

BACKGROUND: Considering the clinical and genetic characteristics, acute lymphoblastic leukemia (ALL) is a rather heterogeneous hematological neoplasm for which current standard diagnostics require various analyses encompassing morphology, immunophenotyping, cytogenetics, and molecular analysis of gene fusions and mutations. Hence, it would be desirable to rely on a technique and an analytical workflow that allows the simultaneous analysis and identification of all the genetic alterations in a single approach. Moreover, based on the results with standard methods, a significant amount of patients have no established abnormalities and hence, cannot further be stratified. METHODS: We performed WTS and WGS in 279 acute lymphoblastic leukemia (ALL) patients (B-cell: n = 211; T-cell: n = 68) to assess the accuracy of WTS, to detect relevant genetic markers, and to classify ALL patients. RESULTS: DNA and RNA-based genotyping was used to ensure correct WTS-WGS pairing. Gene expression analysis reliably assigned samples to the B Cell Precursor (BCP)-ALL or the T-ALL group. Subclassification of BCP-ALL samples was done progressively, assessing first the presence of chromosomal rearrangements by the means of fusion detection. Compared to the standard methods, 97% of the recurrent risk-stratifying fusions could be identified by WTS, assigning 76 samples to their respective entities. Additionally, read-through fusions (indicative of CDKN2A and RB1 gene deletions) were recurrently detected in the cohort along with 57 putative novel fusions, with yet untouched diagnostic potentials. Next, copy number variations were inferred from WTS data to identify relevant ploidy groups, classifying an additional of 31 samples. Lastly, gene expression profiling detected a BCR-ABL1-like signature in 27% of the remaining samples. CONCLUSION: As a single assay, WTS allowed a precise genetic classification for the majority of BCP-ALL patients, and is superior to conventional methods in the cases which lack entity defining genetic abnormalities.

Whole genome sequencing demonstrates substantial pathophysiological differences of MYC rearrangements in patients with plasma cell myeloma and B-cell lymphoma.

MYC rearrangements (MYCr) occur in several B-cell neoplasms and impact disease progression and overall survival. We used whole genome sequencing (WGS) and whole transcriptome sequencing (WTS) to analyze and compare MYCr in different B-cell neoplasms. The MYCr features of cases with plasma cell myeloma (PCM) (n = 88) showed distinct characteristics compared to cases with mature B-cell lymphomas (n = 62, including Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL) and high grade lymphoma with MYC and BCL2 and/or BCL6 rearrangements (HGBL)): they were more complex and showed a wider variety of translocation partners and breakpoints. Additionally, unlike B-cell lymphomas, they showed no evidence of activation-induced deaminase (AID) involvement in the formation of MYCr with immunoglobolin heavy chain (IGH), indicating a different mechanism of origin. The different MYCr characteristics resulted in poor MYCr detection rates by fluorescence in situ hybridization of only 50% in PCM, compared to 94% in lymphoma.

Enhancer Hijacking Drives Oncogenic BCL11B Expression in Lineage-Ambiguous Stem Cell Leukemia.

Lineage-ambiguous leukemias are high-risk malignancies of poorly understood genetic basis. Here, we describe a distinct subgroup of acute leukemia with expression of myeloid, T lymphoid, and stem cell markers driven by aberrant allele-specific deregulation of BCL11B, a master transcription factor responsible for thymic T-lineage commitment and specification. Mechanistically, this deregulation was driven by chromosomal rearrangements that juxtapose BCL11B to superenhancers active in hematopoietic progenitors, or focal amplifications that generate a superenhancer from a noncoding element distal to BCL11B. Chromatin conformation analyses demonstrated long-range interactions of rearranged enhancers with the expressed BCL11B allele and association of BCL11B with activated hematopoietic progenitor cell cis-regulatory elements, suggesting BCL11B is aberrantly co-opted into a gene regulatory network that drives transformation by maintaining a progenitor state. These data support a role for ectopic BCL11B expression in primitive hematopoietic cells mediated by enhancer hijacking as an oncogenic driver of human lineage-ambiguous leukemia. SIGNIFICANCE: Lineage-ambiguous leukemias pose significant diagnostic and therapeutic challenges due to a poorly understood molecular and cellular basis. We identify oncogenic deregulation of BCL11B driven by diverse structural alterations, including de novo superenhancer generation, as the driving feature of a subset of lineage-ambiguous leukemias that transcend current diagnostic boundaries.This article is highlighted in the In This Issue feature, p. 2659.

Whole transcriptome sequencing detects a large number of novel fusion transcripts in patients with AML and MDS.

Fusion transcripts are frequent genetic abnormalities in myeloid malignancies and are often the basis for risk stratification, minimal residual disease (MRD) monitoring, and targeted therapy. We comprehensively analyzed the fusion transcript landscape in 572 acute myeloid leukemia (AML) and 630 myelodysplastic syndrome (MDS) patients by whole transcriptome sequencing (WTS). Totally, 274 fusion events (131 unique fusions) were identified in 210/572 AML patients (37%). In 16/630 MDS patients, 16 fusion events (15 unique fusions) were detected (3%). In AML, 141 cases comprised entity-defining rearrangements (51% of all detected fusions) and 21 (8%) additional well-known fusions, all detected by WTS (control group). In MDS, only 1 fusion was described previously (NRIP1-MECOM, n = 2). Interestingly, a high number of so-far unreported fusions were found (41% [112/274] in AML, 88% [14/16] in MDS), all validated by cytogenetic and/or whole genome sequencing data. With 1 exception (CTDSP1-CFLAR, n = 2), all novel fusions were observed in 1 patient each. In AML, cases with novel fusions showed concomitantly a high frequency of TP53 mutations (67%) and of a complex karyotype (71%), which was also observed in MDS, but less pronounced (TP53, 26%; complex karyotype, 21%). A functional annotation of genes involved in novel fusions revealed many functional relevant genes (eg, transcription factors; n = 28 in AML, n = 2 in MDS) or enzymes (n = 42 in AML, n = 9 in MDS). Taken together, new genomic alterations leading to fusion transcripts were much more common in AML than in MDS. Any novel fusions might be of use for developing markers (eg, for MRD monitoring), particularly in cases without an entity-defining abnormality.

Molecular characterization of a second myeloid neoplasm developing after treatment for acute myeloid leukemia.

Therapy-related myeloid neoplasms (tMN) following successful treatment of acute myeloid leukemia (AML) are rare and poorly characterized. To evaluate the presence of a common ancestral clone, we performed whole-exome sequencing of 25 patients at AML diagnosis, tMN diagnosis (tMDS: 13; tAML: 12), and matched remission samples, identifying 607 mutations affecting 504 different genes (46 recurrently mutated). Number of mutations was higher in tAML vs. tMDS cases (median 19 vs 13 mutations, p = 0.05). Focusing on 24 genes commonly mutated in hematological malignancies, 19/25 (76%) patients were found to share mutations between AML and tMN, mostly affecting epigenetic modifiers (21/32; 66%), splicing factors (6/32; 19%), and chromatin modifiers (3/32; 9%). Analysis of remission samples identified 13 persisting mutations in 10/22 patients, affecting DNMT3A (n = 6), TET2 (n = 5), IDH1 and SRSF2 (n = 1, each). Comparison of cytogenetics revealed that 9/12 patients with a normal karyotype (NK) in AML harbored aberrations in tMN, four aberrant AML cases presented with NK in tMN, four other patients showed unrelated cytogenetic aberrations. Our study provides novel insights into the pathogenesis of tMN, hypothesizing the presence of a common ancestral clone in AML and tMN. Mutations mostly affected epigenetic modifiers, which have previously been linked to clonal hematopoiesis.

Cytogenetic and molecular genetic characterization of KMT2A-PTD positive acute myeloid leukemia in comparison to KMT2A-Rearranged acute myeloid leukemia.

To define the biological differences in acute myeloid leukaemia (AML) with KMT2A gene involvements and their prognostic impact, we compared 190 de novo AML patients at diagnosis, 95 harbouring KMT2A-rearrangement (KMT2Ar) and 95 KMT2A-PTD by performing cytogenetic and molecular genetic analyses. Both AML subtypes had an unfavourable outcome, particularly in patients > 60 years. Patients with KMT2Ar were younger compared to patients with KMT2A-PTD (mean 52 vs 65 years, p < 0.001) and had a higher rate of additional cytogenetic abnormalities (ACA) (46% vs 25% of cases). In both groups, occurrence of ACA did not influence the overall survival (OS). Regarding molecular genetics, 66% of patients with KMT2Ar and 99% of patients with KMT2A-PTD had additional gene mutations. In multivariate analysis, KRAS mutations and 10p12 rearrangement resulted as adverse prognostic factors in KMT2Ar subgroup. In the KMT2A-PTD group, apart from age, only the occurrence of DNMT3A non-R882 mutations correlated with shorter OS.

Novel and Rare Fusion Transcripts Involving Transcription Factors and Tumor Suppressor Genes in Acute Myeloid Leukemia.

Approximately 18% of acute myeloid leukemia (AML) cases express a fusion transcript. However, few fusions are recurrent across AML and the identification of these rare chimeras is of interest to characterize AML patients. Here, we studied the transcriptome of 8 adult AML patients with poorly described chromosomal translocation(s), with the aim of identifying novel and rare fusion transcripts. We integrated RNA-sequencing data with multiple approaches including computational analysis, Sanger sequencing, fluorescence in situ hybridization and in vitro studies to assess the oncogenic potential of the ZEB2-BCL11B chimera. We detected 7 different fusions with partner genes involving transcription factors (OAZ-MAFK, ZEB2-BCL11B), tumor suppressors (SAV1-GYPB, PUF60-TYW1, CNOT2-WT1) and rearrangements associated with the loss of NF1 (CPD-PXT1, UTP6-CRLF3). Notably, ZEB2-BCL11B rearrangements co-occurred with FLT3 mutations and were associated with a poorly differentiated or mixed phenotype leukemia. Although the fusion alone did not transform murine c-Kit+ bone marrow cells, 45.4% of 14q32 non-rearranged AML cases were also BCL11B-positive, suggesting a more general and complex mechanism of leukemogenesis associated with BCL11B expression. Overall, by combining different approaches, we described rare fusion events contributing to the complexity of AML and we linked the expression of some chimeras to genomic alterations hitting known genes in AML.