Search

Therapy-related myelodysplastic syndromes (t-MDS) represent a heterogeneous group of malignancies that arise as a late complication of prior exposure to chemotherapy and/or radiotherapy administered for a primary condition. T-MDS account for approximately 20% of all MDS and are characterized by resistance to current treatment strategies and poor prognosis. Our understanding of t-MDS pathogenesis has considerably improved over the last 5 years with the availability of deep sequencing technologies. T-MDS development is now considered as a multifactorial process resulting from complex interactions between an underlying germline genetic susceptibility, the stepwise acquisition of somatic mutations in hematopoietic stem cells, the clonal selection pressure exerted by cytotoxic therapies, and alterations of the bone marrow microenvironment. The survival of patients with t-MDS is generally poor. This can be explained by both patient-related factors including poor performance status and less tolerance to treatment and disease-related factors, such as the presence of chemoresistant clones, high-risk cytogenetic alterations and molecular features (e.g. high frequency of TP53 mutations). Around 50% of t-MDS patients are classified as high/very high risk based on IPSS-R or IPSS-M scores, versus 30% in de novo MDS. Long-term survival is only achieved in a minority of t-MDS patients who receive allogeneic stem cell transplantation, but the development of novel drugs may open new therapeutic opportunities, especially in unfit patients. Further investigations are needed to improve the identification of patients at higher risk of developing t-MDS and determine whether primary disease treatment can be modified to prevent the occurrence of t-MDS., (Copyright © 2023 Société Française du Cancer. Published by Elsevier Masson SAS. All rights reserved.)

Genes encoding the RNA splicing factors SF3B1, SRSF2, and U2AF1 are subject to frequent missense mutations in clonal hematopoiesis and diverse neoplastic diseases. Most "spliceosomal" mutations affect specific hotspot residues, resulting in splicing changes that promote disease pathophysiology. However, a subset of patients carries spliceosomal mutations that affect non-hotspot residues, whose potential functional contributions to disease are unstudied. Here, we undertook a systematic characterization of diverse rare and private spliceosomal mutations to infer their likely disease relevance. We used isogenic cell lines and primary patient materials to discover that 11 of 14 studied rare and private mutations in SRSF2 and U2AF1 induced distinct splicing alterations, including partially or completely phenocopying the alterations in exon and splice site recognition induced by hotspot mutations or driving "dual" phenocopies that mimicked 2 co-occurring hotspot mutations. Our data suggest that many rare and private spliceosomal mutations contribute to disease pathogenesis and illustrate the utility of molecular assays to inform precision medicine by inferring the potential disease relevance of newly discovered mutations., (© 2020 by The American Society of Hematology.)

Acute myeloid leukemia (AML) with t(8;21) or inv(16) have been recognized as unique entities within AML and are usually reported together as core binding factor AML (CBF-AML). However, there is considerable clinical and biological heterogeneity within this group of diseases, and relapse incidence reaches up to 40%. Moreover, translocations involving CBFs are not sufficient to induce AML on its own and the full spectrum of mutations coexisting with CBF translocations has not been elucidated. To address these issues, we performed extensive mutational analysis by high-throughput sequencing in 215 patients with CBF-AML enrolled in the Phase 3 Trial of Systematic Versus Response-adapted Timed-Sequential Induction in Patients With Core Binding Factor Acute Myeloid Leukemia and Treating Patients with Childhood Acute Myeloid Leukemia with Interleukin-2 trials (age, 1-60 years). Mutations in genes activating tyrosine kinase signaling (including KIT, N/KRAS, and FLT3) were frequent in both subtypes of CBF-AML. In contrast, mutations in genes that regulate chromatin conformation or encode members of the cohesin complex were observed with high frequencies in t(8;21) AML (42% and 18%, respectively), whereas they were nearly absent in inv(16) AML. High KIT mutant allele ratios defined a group of t(8;21) AML patients with poor prognosis, whereas high N/KRAS mutant allele ratios were associated with the lack of KIT or FLT3 mutations and a favorable outcome. In addition, mutations in epigenetic modifying or cohesin genes were associated with a poor prognosis in patients with tyrosine kinase pathway mutations, suggesting synergic cooperation between these events. These data suggest that diverse cooperating mutations may influence CBF-AML pathophysiology as well as clinical behavior and point to potential unique pathogenesis of t(8;21) vs inv(16) AML., (© 2016 by The American Society of Hematology.)

Non-del(5q) transfusion-dependent low/intermediate-1 myelodysplastic syndrome (MDS) patients achieve an erythroid response with lenalidomide in 25% of cases. Addition of an erythropoiesis-stimulating agent could improve response rate. The impact of recurrent somatic mutations identified in the diseased clone in response to lenalidomide and the drug's effects on clonal evolution remain unknown. We investigated recurrent mutations by next-generation sequencing in 94 non-del(5q) MDS patients randomized in the GFM-Len-Epo-08 clinical trial to lenalidomide or lenalidomide plus epoetin β. Clonal evolution was analyzed after 4 cycles of treatment in 42 cases and reanalyzed at later time points in 18 cases. The fate of clonal architecture of single CD34(+)CD38(-) hematopoietic stem cells was also determined in 5 cases. Mutation frequency was >10%: SF3B1 (74.5%), TET2 (45.7%), DNMT3A (20.2%), and ASXL1 (19.1%). Analysis of variant allele frequencies indicated a decrease of major mutations in 15 of 20 responders compared with 10 of 22 nonresponders after 4 cycles. The decrease in the variant allele frequency of major mutations was more significant in responders than in nonresponders (P < .001). Genotyping of single CD34(+)CD38(-) cell-derived colonies showed that the decrease in the size of dominant subclones could be associated with the rise of founding clones or of hematopoietic stem cells devoid of recurrent mutations. These effects remained transient, and disease escape was associated with the re-emergence of the dominant subclones. In conclusion, we show that, although the drug initially modulates the distribution of subclones, loss of treatment efficacy coincides with the re-expansion of the dominant subclone. This trial was registered at www.clinicaltrials.gov as #NCT01718379., (© 2016 by The American Society of Hematology.)

Fetal hemoglobin (HbF, α2γ2) induction is a well-validated strategy for sickle cell disease (SCD) treatment. Using a small-molecule screen, we found that UNC0638, a selective inhibitor of EHMT1 and EHMT2 histone methyltransferases, induces γ-globin expression. EHMT1/2 catalyze mono- and dimethylation of lysine 9 on histone 3 (H3K9), raising the possibility that H3K9Me2, a repressive chromatin mark, plays a role in silencing γ-globin expression. In primary human adult erythroid cells, UNC0638 and EHMT1 or EHMT2 short hairpin RNA-mediated knockdown significantly increased γ-globin expression, HbF synthesis, and the percentage of cells expressing HbF. At effective concentrations, UNC0638 did not alter cell morphology, proliferation, or erythroid differentiation of primary human CD34(+) hematopoietic stem and progenitor cells in culture ex vivo. In murine erythroleukemia cells, UNC0638 and Ehmt2 CRISPR/Cas9-mediated knockout both led to a marked increase in expression of embryonic β-globin genes Hbb-εy and Hbb-βh1. In primary human adult erythroblasts, chromatin immunoprecipitation followed by sequencing analysis revealed that UNC0638 treatment leads to genome-wide depletion in H3K9Me2 and a concomitant increase in the activating mark H3K9Ac, which was especially pronounced at the γ-globin gene region. In RNA-sequencing analysis of erythroblasts, γ-globin genes were among the most significantly upregulated genes by UNC0638. Further increase in γ-globin expression in primary human adult erythroid cells was achieved by combining EHMT1/2 inhibition with the histone deacetylase inhibitor entinostat or hypomethylating agent decitabine. Our data provide genetic and pharmacologic evidence that EHMT1 and EHMT2 are epigenetic regulators involved in γ-globin repression and represent a novel therapeutic target for SCD., (© 2015 by The American Society of Hematology.)

In-depth molecular investigation of familial leukemia has been limited by the rarity of recognized cases. This study examines the genetic events initiating leukemia and details the clinical progression of disease across multiple families harboring germ-line CEBPA mutations. Clinical data were collected from 10 CEBPA-mutated families, representing 24 members with acute myeloid leukemia (AML). Whole-exome (WES) and deep sequencing were performed to genetically profile tumors and define patterns of clonal evolution. Germline CEBPA mutations clustered within the N-terminal and were highly penetrant, with AML presenting at a median age of 24.5 years (range, 1.75-46 years). In all diagnostic tumors tested (n = 18), double CEBPA mutations (CEBPAdm) were detected, with acquired (somatic) mutations preferentially targeting the C-terminal. Somatic CEBPA mutations were unstable throughout the disease course, with different mutations identified at recurrence. Deep sequencing of diagnostic and relapse paired samples confirmed that relapse-associated CEBPA mutations were absent at diagnosis, suggesting recurrence was triggered by novel, independent clones. Integrated WES and deep sequencing subsequently revealed an entirely new complement of mutations at relapse, verifying the presentation of a de novo leukemic episode. The cumulative incidence of relapse in familial AML was 56% at 10 years (n = 11), and 3 patients experienced ≥3 disease episodes over a period of 17 to 20 years. Durable responses to secondary therapies were observed, with prolonged median survival after relapse (8 years) and long-term overall survival (10-year overall survival, 67%). Our data reveal that familial CEBPA-mutated AML exhibits a unique model of disease progression, associated with favorable long-term outcomes., (© 2015 by The American Society of Hematology.)

Acute myeloid leukemia (AML) with t(8;21) (q22;q22) is considered to have favorable risk; however, nearly half of t(8;21) patients are not cured, and recent studies have highlighted remarkable genetic heterogeneity in this subset of AML. Here we identify somatic mutations in additional sex combs-like 2 (ASXL2) in 22.7% (25/110) of patients with t(8;21), but not in patients with inv(16)/t(16;16) (0/60) or RUNX1-mutated AML (0/26). ASXL2 mutations were similarly frequent in adults and children t(8;21) and were mutually exclusive with ASXL1 mutations. Although overall survival was similar between ASXL1 and ASXL2 mutant t(8;21) AML patients and their wild-type counterparts, patients with ASXL1 or ASXL2 mutations had a cumulative incidence of relapse of 54.6% and 36.0%, respectively, compared with 25% in ASXL1/2 wild-type counterparts (P = .226). These results identify a high-frequency mutation in t(8;21) AML and identify the need for future studies to investigate the clinical and biological relevance of ASXL2 mutations in this unique subset of AML., (© 2014 by The American Society of Hematology.)

The SET-NUP214 (TAF1/CAN) fusion gene is a rare genetic event in T-cell acute lymphoblastic leukemia (T-ALL). Eleven (6%) of 196 T-ALL patients enrolled in the French Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL) 2003 and 2005 trials harbored a SET-NUP214 transcript. SET-NUP214-positive patients were predominantly (10 [91%] of 11) T-cell receptor (TCR)-negative and strikingly associated with TCRγδ lineage T-ALLs, as defined by expression of TCRγδ, TCRδ and/or TCRγ rearrangements but no complete TCRβ variable diversity joining rearrangement in surface CD3/TCR-negative cases. When compared with SET-NUP214-negative patients, SET-NUP214-positive patients showed a significantly higher rate of corticosteroid resistance (91% vs 44%; P = .003) and chemotherapy resistance (100% vs 44%; P = .0001). All SET-NUP214-positive patients but one achieved complete remission, and 9 were allografted. Despite the poor early-treatment sensitivity, the outcome of SET-NUP214-positive patients was similar to that of SET-NUP214-negative patients.

Patients with low-risk myelodysplastic syndromes (MDS) that rapidly progress to acute myeloid leukemia (AML) remain a challenge in disease management. Using whole-exome sequencing of an MDS patient, we identified a somatic mutation in the BCOR gene also mutated in AML. Sequencing of BCOR and related BCORL1 genes in a cohort of 354 MDS patients identified 4.2% and 0.8% of mutations respectively. BCOR mutations were associated with RUNX1 (P = .002) and DNMT3A mutations (P = .015). BCOR is also mutated in chronic myelomonocytic leukemia patients (7.4%) and BCORL1 in AML patients with myelodysplasia-related changes (9.1%). Using deep sequencing, we show that BCOR mutations arise after mutations affecting genes involved in splicing machinery or epigenetic regulation. In univariate analysis, BCOR mutations were associated with poor prognosis in MDS (overall survival [OS]: P = .013; cumulative incidence of AML transformation: P = .005). Multivariate analysis including age, International Prognostic Scoring System, transfusion dependency, and mutational status confirmed a significant inferior OS to patients with a BCOR mutation (hazard ratio, 3.3; 95% confidence interval, 1.4-8.1; P = .008). These data suggest that BCOR mutations define the clinical course rather than disease initiation. Despite infrequent mutations, BCOR analyses should be considered in risk stratification.

Mutation of the MYD88 gene has recently been identified in activated B-cell-like diffuse cell lymphoma and enhanced Janus kinase/signal transducer and activator of transcription (JAK-STAT) and nuclear factor κB (NF-κB) signaling pathways. A whole exome-sequencing study of Waldenstrom macroglobulinemia (WM) suggested a high frequency of MYD88 L265P mutation in WM. The genetic background is not fully deciphered in WM, although the role of NF-κB and JAK-STAT has been demonstrated. We analyzed MYD88 mutation in exon 5 and characterized the clinical significance of this genetic alteration in 67 WM patients. Clinical features; immunophenotypic markers; and conventional cytogenetic, fluorescence in situ hybridization, and single nucleotide polymorphism array data were analyzed. MYD88 L265P mutation was acquired in 79% of patients. Overall, we have identified alteration of the MYD88 locus in 91% of WM patients, including 12% with gain on chromosome 3 at the 3p22 locus that included the MYD88 gene. Patients with absence of MYD88 mutation were WM characterized with a female predominance, a splenomegaly, gain of chromosome 3, and CD27 expression. Importantly, inhibition of MYD88 signaling induced cytotoxicity and inhibited cell growth of cell lines issued from patients with WM. In conclusion, these results confirm a high frequency of MYD88 L265P mutation in WM. The discovery of MYD88 L265P mutation may contribute to a better understanding of the physiopathogeny of WM.

Genomic studies in chronic myeloid malignancies, including myeloproliferative neoplasms (MPN), myelodysplastic syndromes (MDS), and MPN/MDS, have identified common mutations in genes encoding signaling, epigenetic, transcription, and splicing factors. In the present study, we interrogated the clonal architecture by mutation-specific discrimination analysis of single-cell-derived colonies in 28 patients with chronic myelomonocytic leukemias (CMML), the most frequent MPN/MDS. This analysis reveals a linear acquisition of the studied mutations with limited branching through loss of heterozygosity. Serial analysis of untreated and treated samples demonstrates a dynamic architecture on which most current therapeutic approaches have limited effects. The main disease characteristics are early clonal dominance, arising at the CD34(+)/CD38(-) stage of hematopoiesis, and granulomonocytic differentiation skewing of multipotent and common myeloid progenitors. Comparison of clonal expansions of TET2 mutations in MDS, MPN, and CMML, together with functional invalidation of TET2 in sorted progenitors, suggests a causative link between early clonal dominance and skewed granulomonocytic differentiation. Altogether, early clonal dominance may distinguish CMML from other chronic myeloid neoplasms with similar gene mutations.

Not all patients with core binding factor acute myeloid leukemia (CBF-AML) display a good outcome. Modern risk factors include KIT and/or FLT3 gene mutations and minimal residual disease (MRD) levels, but their respective values have never been prospectively assessed. A total of 198 CBF-AML patients were randomized between a reinforced and a standard induction course, followed by 3 high-dose cytarabine consolidation courses. MRD levels were monitored prospectively. Gene mutations were screened at diagnosis. Despite a more rapid MRD decrease after reinforced induction, induction arm did not influence relapse-free survival (RFS) (64% in both arms; P = .91). Higher WBC, KIT, and/or FLT3-ITD/TKD gene mutations, and a less than 3-log MRD reduction after first consolidation, were associated with a higher specific hazard of relapse, but MRD remained the sole prognostic factor in multivariate analysis. At 36 months, cumulative incidence of relapse and RFS were 22% vs 54% (P < .001) and 73% vs 44% (P < .001) in patients who achieved 3-log MRD reduction vs the others. These results suggest that MRD, rather than gene mutations, should be used for future treatment stratifications in CBF-AML patients. This trial was registered at EudraCT as #2006-005163-26 and at www.clinicaltrials.gov as #NCT 00428558.

RUNX1 gene alterations are associated with acquired and inherited hematologic malignancies that include familial platelet disorder/acute myeloid leukemia, primary or secondary acute myeloid leukemia, and chronic myelomonocytic leukemia. Recently, we reported that RUNX1-mediated silencing of nonmuscle myosin heavy chain IIB (MYH10) was required for megakaryocyte ploidization and maturation. Here we demonstrate that runx1 deletion in mice induces the persistence of MYH10 in platelets, and a similar persistence was observed in platelets of patients with constitutional (familial platelet disorder/acute myeloid leukemia) or acquired (chronic myelomonocytic leukemia) RUNX1 mutations. MYH10 was also detected in platelets of patients with the Paris-Trousseau syndrome, a thrombocytopenia related to the deletion of the transcription factor FLI1 that forms a complex with RUNX1 to regulate megakaryopoiesis, whereas MYH10 persistence was not observed in other inherited forms of thrombocytopenia. We propose MYH10 detection as a new and simple tool to identify inherited platelet disorders and myeloid neoplasms with abnormalities in RUNX1 and its associated proteins.

A cohort of MDS patients was examined for mutations affecting 4 splice genes (SF3B1, SRSF2, ZRSR2, and U2AF35) and evaluated in the context of clinical and molecular markers. Splice gene mutations were detected in 95 of 221 patients. These mutations were mutually exclusive and less likely to occur in patients with complex cytogenetics or TP53 mutations. SF3B1(mut) patients presented with lower hemoglobin levels, increased WBC and platelet counts, and were more likely to have DNMT3A mutations. SRSF2(mut) patients clustered in RAEB-1 and RAEB-2 subtypes and exhibited pronounced thrombocytopenias. ZRSR2(mut) patients clustered in International Prognostic Scoring System intermediate-1 and intermediate-2 risk groups, had higher percentages of bone marrow blasts, and more often displayed isolated neutropenias. SRSF2 and ZRSR2 mutations were more common in TET2(mut) patients. U2AF35(mut) patients had an increased prevalence of chromosome 20 deletions and ASXL1 mutations. Multivariate analysis revealed an inferior overall survival and a higher AML transformation rate for the genotype ZRSR2(mut)/TET2(wt) (overall survival: hazard ratio = 3.3; 95% CI, 1.4-7.7; P = .006; AML transformation: hazard ratio = 3.6; 95% CI, 2-4.2; P = .026). Our results demonstrate that splice gene mutations are among the most frequent molecular aberrations in myelodysplastic syndrome, define distinct clinical phenotypes, and show preferential associations with mutations targeting transcriptional regulation.

Hydroxyurea is the standard therapy of chronic myelomonocytic leukemia (CMML) presenting with advanced myeloproliferative and/or myelodysplastic features. Response to hypomethylating agents has been reported in heterogeneous series of CMML. We conducted a phase 2 trial of decitabine (DAC) in 39 patients with advanced CMML defined according to a previous trial. Median number of DAC cycles was 10 (range, 1-24). Overall response rate was 38% with 4 complete responses (10%), 8 marrow responses (21%), and 3 stable diseases with hematologic improvement (8%). Eighteen patients (46%) demonstrated stable disease without hematologic improvement, and 6 (15%) progressed to acute leukemia. With a median follow-up of 23 months, overall survival was 48% at 2 years. Mutations in ASXL1, TET2, AML1, NRAS, KRAS, CBL, FLT3, and janus kinase 2 (JAK2) genes, and hypermethylation of the promoter of the tumor suppressor gene TIF1γ, did not predict response or survival on DAC therapy. Lower CJUN and CMYB gene expression levels independently predicted improved overall survival. This trial confirmed DAC efficacy in approximately 40% of CMML patients with advanced myeloproliferative or myelodysplastic features and suggested that CJUN and CMYB expression could be potential biomarkers in this setting. This trial is registered at EudraCT (eudract.ema.europa.eu) as #2008-000470-21 and www.clinicaltrials.gov as #NCT01098084.

To assess the value of administering timed-sequential chemotherapy (TSC; 2 therapeutic sequences separated by a 4-day interval-free chemotherapy) or high-dose cytarabine (HDAraC) cycles in consolidation therapy for acute myeloid leukemia (AML), 459 patients 15 to 50 years of age were enrolled in the prospective randomized Acute Leukemia French Association-9802 trial. Complete remission was achieved in 89%. A total of 237 patients were then randomized to either TSC consolidation (120 patients) or HDAraC consolidation cycles (117 patients). Overall, there was no significant difference between the 2 consolidation arms (5-year event-free survival [EFS]: 41% for HDAraC vs 35% for TSC), or cumulative incidence of relapse, or treatment-related mortality. Cytogenetically normal AML NPM1(+) or CEBPA(+) and FLT3-ITD(-) had the same outcome as those with favorable cytogenetics. When considering favorable and unfavorable risk groups, the trend was in favor of HDAraC. However, the difference became significant when considering intermediate cytogenetics (5-year EFS: 49% vs 29%; P = .02), especially cytogenetically normal AML (5-year EFS: 48% vs 31%; P = .04), which was related to lower relapse rate and less toxicity. This study demonstrates that TSC did not produce any benefit when used as consolidation therapy in younger adults compared with HDAraC. This trial was registered at www.clinicaltrials.gov as #NCT00880243.

Mutations of the ten eleven translocation 2 gene (TET2) have recently been reported in myelodysplastic syndrome and myeloproliferative neoplasms. We analyzed the incidence and prognostic value of TET2 point mutations and other genomic alterations by direct sequencing and single nucleotide polymorphism microarray analysis in 111 de novo acute myeloid leukemia, who had all achieved complete remission (CR). Mutations were observed in 19 (17%) of the 111 patients compared with 10 (27%) of 36 patients who had failed to achieve CR (P = .2). In the 111 patients who had achieved CR, TET2 alterations were only significantly associated with NPM1 mutations but not with other pretreatment characteristics. TET2 gene status was not significantly correlated with disease-free survival and overall survival, both in the entire cohort and in patients with normal karyotype.

Familial platelet disorder (FPD), a rare autosomal dominant disorder characterized by quantitative and qualitative platelet abnormalities, is considered as a model of genetic predisposition to acute myeloid leukemia (AML). So far, monoallelic RUNX1 germline mutations have been found in 19 of 20 families with reported FPD, and the analysis of blast cells from only 5 patients at acute leukemia (AL) stage has shown no additional RUNX1 abnormality. Here, we performed RUNX1 analysis at constitutional and somatic levels in 8 persons with FPD who developed AL from 4 independent families. In addition to the germline RUNX1 mutation, we identified a second RUNX1 alteration in 6 AML cases (acquired point mutations in 4 cases and duplication of the altered RUNX1 allele associated with acquired trisomy 21 in 2 other cases). Although haploinsufficiency of RUNX1 causes FPD, our findings suggest that a second genetic event involving RUNX1 is often associated with progression to AML.

Mutations of the CCAAT/enhancer binding protein alpha (CEBPA) gene have been associated with a favorable outcome in patients with acute myeloid leukemia (AML), but mainly in those with a normal karyotype. Here, we analyzed the impact of associated cytogenetic abnormalities or bad-prognosis fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) in 53 patients with CEBPA(+) de novo AML treated in the Acute Leukemia French Association trials. We found that only those with a normal karyotype and no FLT3-ITD displayed the expected favorable outcome. In this context, relapse-free, disease-free, and overall survival were significantly longer than in corresponding patients without the CEBPA mutation (P = .035, .016, and .047, respectively). This was not observed in the context of an abnormal karyotype or associated FLT3-ITD. Furthermore, after adjustment on age, trial, and mutation type, these features were independently predictive of shorter overall survival in the subset of patients with CEBPA(+) AML (multivariate hazard ratio = 2.7; 95% confidence interval, 1.08-6.7; and 2.9; 95% confidence interval, 1.01-8.2; with P = .034 and .05, for abnormal karyotype and FLT3-ITD, respectively).

Mutation of the nucleophosmin (NPM) gene has been reported as the most frequent mutation in acute myeloid leukemia (AML), especially in the presence of a normal karyotype. In this subgroup of intermediate-risk AML, the identification of other gene mutations (eg, FLT3, CCAAT/enhancer-binding protein-alpha [CEBPA]) has helped to refine the prognosis. This study explored the prevalence and the prognostic impact of NPM mutations in a cohort of 106 patients with normal-karyotype AML. NPM exon 12 mutations were detected by polymerase chain reaction (PCR) and fragment analysis for the insertion/deletion globally resulting in a 4-bp insertion. NPM mutations were detected in 47% of patients and were associated with a high white blood cell count, involvement of the monocytic lineage (M4/M5), and a decreased prevalence of CEBPA mutations. Complete remission rate and long-term outcome did not differ between NPM-mutated and -nonmutated patients. Prospective studies are needed to confirm the definitive place of NPM mutation detection to predict AML response to therapy.