正常核型急性髓系白血病NPM1和FLT3-ITD基因突变的研究

目的:探讨正常核型急性髓系白血病(AML)患者中NPM1基因与FLT3基因内部串联重复(ITD)突变的发生率,并了解其临床特征。方法:收集40例正常核型AML患者初诊时骨髓单个核细胞,采用基因组DNA-PCR方法分别扩增其NPM1和FLT3基因,直接测序法分析NPM1第12外显子突变,琼脂糖电泳分析FLT3-ITD突变。结果:40例正常核型AML患者中共检出NPM1突变15例(37.5%),FLT3-ITD突变8例(20%),4例(10%)同时存在NPM1和FLT3-ITD基因2种突变。单纯NPM1或FLT3-ITD突变的AML患者初诊时表现为高白细胞数、高骨髓原始细胞比例(P0.05)。结论:NPM1和FLT3-ITD突变是正常核型AML患者常见的分子学异常,且与初诊时高外周血白细胞数、高骨髓原始细胞比例相关。     

正常核型急性髓系白血病NPM1和FLT3-ITD基因突变的研究

目的:探讨正常核型急性髓系白血病(AML)患者中NPM1基因与FLT3基因内部串联重复(ITD)突变的发生率,并了解其临床特征。方法:收集40例正常核型AML患者初诊时骨髓单个核细胞,采用基因组DNA-PCR方法分别扩增其NPM1和FLT3基因,直接测序法分析NPM1第12外显子突变,琼脂糖电泳分析FLT3-ITD突变。结果:40例正常核型AML患者中共检出NPM1突变15例(37.5%),FLT3-ITD突变8例(20%),4例(10%)同时存在NPM1和FLT3-ITD基因2种突变。单纯NPM1或FLT3-ITD突变的AML患者初诊时表现为高白细胞数、高骨髓原始细胞比例(P0.05)。结论:NPM1和FLT3-ITD突变是正常核型AML患者常见的分子学异常,且与初诊时高外周血白细胞数、高骨髓原始细胞比例相关。     

急性髓细胞白血病患者NPM1与FLT3基因突变的研究

目的 探讨急性髓细胞白血病（AML）患者中NPM1基因与FLT3基因内部串联重复（ITD）突变的发生率,并了解其临床特征及预后。方法 收集86例成人AML患者初诊时骨髓单个核细胞,采用基因组DNA-PCR方法分别扩增其NPM1和FLT3基因,毛细管电泳方法分析NPM1第12外显子突变,琼脂糖电泳分析FLT3-ITD突变,随访判断其预后。结果 86例AML患者中共检出NPM1基因突变29例（33．7％）,FLT3-ITD突变15例（17,4％）。两种突变在50例染色体正常核型AML中的发生率分别为46．0％和24．0％,明显高于异常核型AML患者。7例中6例NPM1^＋／FLT3-ITD^＋双阳性AML患者表现为正常核型,外周血白细胞均〉50×10^9几。单纯NPM1^＋或FLT3-ITD^＋AML患者初诊时也表现为高白细胞（P〈0.05）,NPM1^＋AML患者CD34表达率较低（P〈0．001）、临床完全缓解（CR）率略高（66.7％、53.3％,P〉0.05）、总生存率（OS）高（P〉0.05）;而FLT3-ITD^＋AML患者CR率略低（50．0％、58．8％,P〉0.05）、OS低（P〉0.05）。NPM1^＋／FLT3-ITD^-、NPM^-／FLT3-ITD^-、NPM^＋／FLT3-ITD^＋、NPM1-／FLT3-ITD^＋四组患者的CR率分别为66．7％、62．5％、50．0％、42．9％（P〉0．05）,各组间OS差异无统计学意义（P〉0．05）。结论 NPM1和FLT3-ITD突变是AML（尤其正常核型AML）患者常见的分子学异常,且与其临床特点、疗效及预后有一定相关性。     

急性髓细胞白血病遗传学特征与临床特征分析

目的 :探讨急性髓细胞白血病(AML)患者的分子遗传学特征及其与临床特征的关联性。方法 :采用骨髓短期培养和G显带技术对103例AML患者进行染色体核型分析,并通过PCR技术对其基因突变、融合基因等进行检测。结果:在103例患者样本中所检测到的FMS样酪氨酸激酶3基因的内部串联重复(FLT3-ITD)突变和酪氨酸激酶结构域点突变(FLT3-TKD)、核磷蛋白1(NPM1)基因突变、神经母细胞瘤RAS癌(NRAS)基因突变、异柠檬酸脱氢酶1(IDH1)基因突变、CCAAT/增强子结合蛋白α(CEBPA)基因突变、人类原癌基因C-KIT突变的发生率分别为14.3%、3.3%、14.3%、12.4%、5.6%、10.6%和18.8%;NPM1突变阳性患者较阴性患者骨髓幼稚细胞比例高(P=0.0105),FLT3-ITD突变阳性患者较阴性患者的病死率低(P=0.0285),而C-KIT突变阳性患者较阴性患者的病死率高(P=0.0255)。结论:AML患者的分子遗传学特征细化了基于核型的AML危险度分层,其中FLT3-ITD、NPM1、C-KIT突变与患者的临床特征有关联。     

急性髓性细胞白血病的分子遗传学研究进展

急性髓性细胞白血病(AML)是一种异质性和克隆性的造血干细胞(HSC)疾病,由于HSC获得性异常遗传,使HSC异常自我更新、增殖和分化,故遗传物质异常导致AML发病。但40%～49%的AML患者为正常染色体核型〔1〕。因此,对于正常核型AML患者的分子遗传学研究有重要意义。已经有许多影响正常核型AML患者预后的基因突变和基因表达变化被证实,如FMS样酪氨酸激酶3(FLT3)基因突变、核磷蛋白1(NPM1)基因突变、MLL基因部分串联重复(MLL-PTD)、髓系转录因子CCAAT增强子结合蛋白-A(CEBPA)基因突变及脑和急性白血病胞质(BAALC)基因过表     

老年急性髓系白血病患者106例临床特点

目的 研究急性髓系白血病老年患者细胞遗传学及分子生物学特征.方法 回顾性分析我中心初治老年急性髓系白血病患者106例,对其的染色体核型及基因突变进行研究.结果 106例患者中异常核型52例,检出率为49.06％.t(15;17)及t(8;21)预后良好核型的发生率分别为13.21％ (14/106)与5.66％ (6/106);预后不良的复杂核型及单体型核型的检出率分别为9.43％ (10/106)及4.72％ (5/106).染色体预后分层:良好组、中危组、高危组所占比例分别为18.87％ (20/106)、70.75％ (75/106)与10.83％ (11/106).高危组预后较差.共21例患者行分子学检测,NPM1、FLT3-ITD及c-kit突变的发生率分别为23.81％、14.29％及4.76％,NPM1、FLT3-1TD突变者均为正常核型,c-kit突变只见于t(8;21)患者.结论 老年患者预后良好核型低,预后不良核型则高.老年患者预后较差,高危组患者预后更差.     

266例急性髓系白血病患者的染色体核型、基因突变及治疗观察

目的 观察266例急性髓系白血病（AML）患者的染色体核型、基因突变及治疗情况。方法 AML患者266例，采用R显带技术检测染色体核型，聚合酶链式反应（PCR）技术检测基因突变；所有患者采用IA方案、DA方案或HA方案治疗，观察不同ELN危险分层、基因突变种类患者的治疗效果。结果 266例AML中，染色体异常核型105例，其中复杂核型26例、t(8;21)(q22;q22)核型18例、Inv(16)(p13q22)核型10例、5q-核型7例、-Y核型9例、-7核型6例、其他核型29例；基因突变182例，其中WT1基因突变29例、CEBPA基因突变27例、DNMT3A基因突变27例、NPM1基因突变19例、TET2基因突变17例、FLT3-ITD基因突变17例、IDH2基因突变17例、KIT基因突变13例、NRAS基因突变15例、RUNX1基因突变12例、CBFβ-MYH11基因突变10例、IDH1基因突变8例、BCOR基因突变7例、BCR-ABL基因突变7例、TP53基因突变7例、ASXL1基因突变5例、KMT2A基因突变5例、PTPM11基因突变3例、ZRSR2基因突变2例、EZH2...     

FLT3-ITD突变高等位基因比率在急性髓系白血病中的预后意义

目的:探讨FLT3-ITD突变高等位基因比率在急性髓系白血病(AML)患者中的预后意义。方法:筛选100例检测到FLT3-ITD等位基因比率的AML初诊患者的临床资料,对其临床特征及预后因素进行统计学分析。结果:100例患者初诊时中位白细胞计数为80.1×10~9/L(2×10~9/L～326×10~9/L),中位骨髓原始细胞比例数为68.5%(21%～95%),细胞遗传学检查示正常核型66例。将FLT3-ITD等位基因比率阈值设置在1.0,分为低等位基因比率组(1.0,64例)和高等位基因比率组(≥1.0,36例)进行分析,这些患者的初次完全缓解(CR1)率总体为70.0%,低等位基因比率组和高等位基因比率组间CR1率差异有统计学意义(82.8%vs 47.2%,P0.001)。在接受异基因造血干细胞移植(allo-HSCT)的65例患者中,低等位基因比率组的无复发生存(RFS)和总生存(OS)明显优于高等位基因比率组(RFS:P=0.007,OS:P=0.014)。而对于高等位基因比率组患者,allo-HSCT与化疗比较,未能明显改善其RFS及OS(RFS:P=0.539,OS:P=0.579)。在未进行allo-HSCT的患者中,低等位基因比率组和高等位基因比率组间RFS和OS差异无统计学意义(RFS:P=0.538,OS:P=0.854)。伴有其他突变(CEBPA、NPM1、DNMT3A)的FLT3-ITD高等位基因比率患者的CR1、OS、RFS,与低等位基因比率患者比较差异无统计学意义(P0.05)。对患者的预后因素进行分析发现,CR1、外周白细胞计数及allo-HSCT在单因素、多因素分析中均对RFS、OS有影响。FLT3-ITD高等位基因比率的AML患者能检测到13号染色体长臂杂合性丢失(LOH),且等位基因比率值越高,LOH检测到的频率越高。结论:FLT3-ITD突变高等位基因比率的AML患者具有较高的白细胞计数,多合并NPM1突变、CR1率低及OS、RFS短的特征。对于不同化疗效果均差,即使进行allo-HSCT也未能明显改善其OS及RFS。高等位基因比率患者存在LOH状态,等位基因比率值越高,LOH频率越高。     

急性髓系白血病患者miRNA-181b表达特点及预后意义

目的 探讨微小RNA-181b(miR-181b)在急性髓性白血病(AML)中的表达特点及预后意义.方法 采用实时定量逆转录-聚合酶链反应(RT-PCR)检测158例初诊AML患者及20例健康供者骨髓单个核细胞中miR-181b的表达水平.同时采用基因组DNA-PCR结合测序方法检测158例AML患者核磷蛋白1(NPM1)基因第12号外显子突变和fms样酪氨酸激酶3(FLT3)基因内部串联重复(ITD)突变(FLT3-ITD).结果 AML中miR-181b表达水平较正常对照组显著升高(Z =-2.386,P=0.017),各FAB亚型中M1、M5及M6型miR-181b表达水平较对照组明显升高(P＜0.05).miR-181b高表达与低血红蛋白、高乳酸脱氢酶及NPMI野生型有关.miR-181b高表达完全缓解率较低(x2 =7.717,P=0.005)、总生存期较短(P＜0.05).结论 miR-181b在AML某些亚型中高表达,miR-181b高表达是AML患者不利的预后因素.     

老年急性髓系白血病基因突变及临床意义

目的:探讨老年急性髓系白血病(AML)患者基因突变情况及其临床意义。方法:采用二代测序方法检测69例初诊老年AML患者基因突变情况,包括TET2,DNMT3A,NPM1,CEBPα,EZH2,JAK2,U2AF1,RUNX1,NRAS,TP53,IDH2,C-KIT,SRSF2,SF3B1,ASXL1,FLT3,ETV6,PHF6,CBL,SETBP1,ZRSR2,收集患者临床资料,分析突变发生率及临床意义,针对49例接受DCAG治疗患者分析疗效及预后。结果:老年AML患者基因突变频率高,突变率为94.2%(65/69),NPM1,SRSF2,SF3B1在4种白血病分型间分布存在差异(均P0.05)。C-KIT突变易出现在染色体核型低中危组(P0.001),TP53突变与高危核型有关(P=0.003)。TP53突变,ETV6突变,合并症数目,染色体核型及DCAG首次诱导完全缓解均为影响预后的因素,其中TP53突变,首次诱导完全缓解及合并症数目为独立危险因素(P0.05)。结论:老年AML患者基因突变及细胞遗传学异常对临床诊疗工作具有重要意义。     

Nucleophosmin mutations in childhood acute myelogenous leukemia with normal karyotype

Nucleophosmin (NPM) is a nucleocytoplasmic shuttling protein involved in leukemia-associated chromosomal translocations, and it regulates the alternate reading frame (ARF)-p53 tumor-suppressor pathway. Recently, it has been demonstrated that mutations of the NPM1 gene alter the protein at its C-terminal, causing its cytoplasmic localization. Cytoplasmic NPM was detected in 35% of adult patients with primary non-French-American-British (FAB) classification M3 acute myeloid leukemia (AML), associated mainly with normal karyotype. We evaluated the prevalence of the NPM1 gene mutation in non-M3 childhood AML patients enrolled in the ongoing Associazione Italiana di Ematologia e Oncologia Pediatrica (AIEOP-AML02) protocol in Italy. NPM1 mutations were found in 7 (6.5%) of 107 successfully analyzed patients. NPM1-mutated patients carried a normal karyotype (7/26, 27.1%) and were older in age. Thus, the NPM1 mutation is a frequent abnormality in AML patients without known genetic marker; the mutation may represent a new target to monitor minimal residual disease in AML and a potential candidate for alternative and targeted treatments.     

TET2 mutation is an unfavorable prognostic factor in acute myeloid leukemia patients with intermediate-risk cytogenetics

The studies concerning clinical implications of TET2 mutation in patients with primary acute myeloid leukemia (AML) are scarce. We analyzed TET2 mutation in 486 adult patients with primary AML. TET2 mutation occurred in 13.2% of our patients and was closely associated with older age, higher white blood cell and blast counts, lower platelet numbers, normal karyotype, intermediate-risk cytogenetics, isolated trisomy 8, NPM1 mutation, and ASXL1 mutation but mutually exclusive with IDH mutation. TET2 mutation is an unfavorable prognostic factor in patients with intermediate-risk cytogenetics, and its negative impact was further enhanced when the mutation was combined with FLT3-ITD, NPM1-wild, or unfavorable genotypes (other than NPM1(+)/FLT3-ITD(-) or CEBPA(+)). A scoring system integrating TET2 mutation with FLT3-ITD, NPM1, and CEBPA mutations could well separate AML patients with intermediate-risk cytogenetics into 4 groups with different prognoses (P < .0001). Sequential analysis revealed that TET2 mutation detected at diagnosis was frequently lost at relapse; rarely, the mutation was acquired at relapse in those without TET2 mutation at diagnosis. In conclusion, TET2 mutation is associated with poor prognosis in AML patients with intermediate-risk cytogenetics, especially when it is combined with other adverse molecular markers. TET2 mutation appeared to be unstable during disease evolution.     

Prognostic significance ofFLT3 internal tandem duplication andNPM1 mutations in acute myeloid leukemia in an unselected patient population

Mutations in the fms-like tyrosine kinase 3 (FLT3) gene containing an internal tandem duplication (FLT3/ITD) or mutations in the nucleophosmin 1 gene (NPM1) are thought to be prognostic indicators in acute myeloid leukemia (AML). Previous studies suggested that FLT3/ITD mutation indicates a poor prognosis and that NPM1 mutation indicates a more favorable one, but these studies were often performed with selected patient populations. We investigated the clinical significance of these mutations at our institution with an unselected group of patients with newly diagnosed AML. This group included patients > or =60 years old and those with a poor performance status. Using polymerase chain reaction and sequencing analyses, we detected FLT3/ITD mutations in 12 patients (20.0%) and NPM1 mutations in 7 patients (11.7%) among a group of 60 patients. There was a nonsignificant trend for FLT3/ITD mutation to be associated with a poorer predicted overall survival (OS) probability in this population. In contrast, OS was significantly higher in patients with wild-type NPM1 than in patients with NPM1 mutation, both for all AML patients and for AML patients with a normal karyotype. In this general and unselected AML patient population, NPM1 mutation was not a prognostic indicator of a favorable outcome.     

Prevalence, clinical profile, and prognosis of NPM mutations in AML with normal karyotype

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.     

Prevalence and prognostic impact of NPM1 mutations in 1485 adult patients with acute myeloid leukemia (AML)

Mutations of the nucleophosmin (NPM1) gene have recently been described in patients with acute myeloid leukemia (AML). To clarify the prevalence as well as the clinical impact of this mutation, we investigated 1485 patients with AML for NPM1 exon 12 mutations using fragment analysis. A 4 bp insert was detected in 408 of 1485 patients (27.5%). Sequence analysis revealed known mutations (type A, B, and D) as well as 13 novel alterations in 229 analyzed cases. NPM1 mutations were most prevalent in patients with normal karyotype (NK) (324 of 709; 45.7%) compared with 58 of 686 with karyotype abnormalities (8.5%; P < .001) and were significantly associated with several clinical parameters (high bone marrow [BM] blasts, high white blood cell [WBC] and platelet counts, female sex). NPM1 alterations were associated with FLT3-ITD mutations, even if restricted to patients with NK (NPM1-mut/FLT3-ITD: 43.8%; versus NPM1-wt/FLT3-ITD: 19.9%; P < .001). The analysis of the clinical impact in 4 groups (NPM1 and FLT3-ITD single mutants, double mutants, and wild-type [wt] for both) revealed that patients having only an NPM1 mutation had a significantly better overall and disease-free survival and a lower cumulative incidence of relapse. In conclusion, NPM1 mutations represent a common genetic abnormality in adult AML. If not associated with FLT3-ITD mutations, mutant NPM1 appears to identify patients with improved response toward treatment.     

IDH2 mutations are frequent in Chinese patients with acute myeloid leukemia and associated with NPM1 mutations and FAB-M2 subtype

Introduction: Gene mutations play an important role in acute myeloid leukemia (AML) pathogenesis. Several genes have been identified in AML, such as FLT3, KIT, NPM1, and JAK2. This study investigated the frequency of novel mutations in IDH1 (amino acid R132) and IDH2 (R140 and R172) and analyzed their impact on disease biology and interaction with other mutations in Chinese patients with de novo AML. Methods: A total of 195 patients were screened for mutations in the IDH1, IDH2, JAK2 V617F, NPM1, FLT3, and KIT genes, using polymerase chain reaction (PCR)-based and direct sequencing assays. Results: IDH mutations occurred at a considerable frequency of 15.89% in Chinese AML cases; IDH2 R140Q was the most frequent genetic alteration and was associated with older age, normal karyotype, and French-American-British classification M2 at diagnosis. There was a strong association of IDH2 mutation with NPM1 mutations and a trend with FLT3-internal-tandem duplication. Conclusion: IDH mutations may be a novel genetic marker in cytogenetically normal AML and may cooperate in leukemogenesis.     

Nucleophosmin mutation in Southeast Asian acute myeloid leukemia: eight novel variants, FLT3 coexistence and prognostic impact of NPM1/FLT3 mutations

NPM1 mutations were investigated in 400 Southeast Asian leukemia patients and were detectable in 105 cases (26.25%) of acute myeloid leukemia but in no cases of acute lymphoid leukemia or chronic myeloid leukemia. Eight novel and 5 known mutations were identified. All predicted novel proteins shared the last five amino acids VSLRK with the similar gain of nuclear exporting signal motif as known variants. Older age, high white blood cell and platelet counts, normal cytogenetics, and CD34-negativity were associated with NPM1 mutation. FLT3 mutation was more frequent in mutant NPM1 than wild-type cases (56.8% vs. 25.6%) whereas RAS and AML1 mutations were rarely found. Overall survival analysis based on the NPM1/FLT3 mutational status revealed a better outcome for the NPM1-positive/FLT3-negative subgroup. We conclude that: i) NPM1 mutation represents a common genetic hallmark in Southeast Asian acute myeloid leukemia with a normal karyotype; ii) NPM1 mutants coexisted mainly with FLT3 mutants, but not RAS or AML1; iii) FLT3 mutation had a negative prognostic impact on patients with mutant NPM1.     

Prognostic Impact of NPM1 Mutations in Serbian Adult Patients with Acute Myeloid Leukemia

Based on current findings, the presence of NPM1 mutations in acute myeloid leukemia (AML) patients is associated with an increased probability of complete remission (CR) and better overall survival (OS). We determined the incidence and prognostic relevance of NPM1 mutations, their association with FLT3 and IDH mutations, and other clinical characteristics in Serbian adult AML patients. Samples from 111 adult de novo AML patients, including 73 AML cases with a normal karyotype (NK-AML), were studied. NPM1, FLT3, and IDH mutations were detected by PCR and direct sequencing. NPM1 mutations were detected in 22.5% of patients. The presence of NPM1 mutations predicted a low CR rate and shorter OS. NPM1 mutations showed an association with both FLT3 and IDH mutations. Survival analysis based on NPM1/FLT3 mutational status revealed a lower OS for NPM1(+)/FLT3(-) compared to the NPM1(-)/FLT3(-) group in NK-AML patients. The lack of impact or unfavorable prognostic effect of NPM1 mutations found in this study can be assigned to a small cohort of analyzed AML patients, as can the presence of FLT3 and IDH mutations or other genetic lesions that cooperate with NPM1 mutations influencing prognosis.     

NPM1 mutation is a stable marker for minimal residual disease monitoring in acute myeloid leukaemia patients with increased sensitivity compared to WT1 expression

Mutation in the NPM1 gene occurs in 60% of acute myeloid leukaemia (AML) patients with normal karyotype. NPM1 mutation is potentially a superior minimal residual disease (MRD) marker compared to WT1 gene overexpression by being specific to the malignant clone, although experimental evidence published so far includes very limited numbers of relapsed cases. Also, the stability of the NPM1 mutation has been questioned by reports of the mutation being lost at relapse. In the present study we compared NPM1 mutation and WT1 overexpression as MRD markers in 20 cases of relapsed AML. The 20 patients experienced a total of 28 morphological relapses. Karyotypic evolution was detected in 56% of relapses. All relapses were accompanied by high levels of NPM1 mutation, along with high WT1 mRNA levels, thus demonstrating complete stability of both markers during relapse. Detectable NPM1 mutation following a period of morphological remission was accompanied by a morphological relapse in all cases. In contrast, WT1 expression was detected in 33% of the NPM1 mutation negative samples. This background WT1 expression produced by non-leukaemia cells was highly variable, both between and within patients, and limited the de facto sensitivity of the WT1 expression analysis. The present study therefore provides important experimental evidence demonstrating that NPM1 mutation is superior to WT1 overexpression as marker of MRD in NPM1-mutated AML, even in the presence of extensive karyotypic evolution.     

Clinical characteristics and prognostic implications of NPM1 mutations in acute myeloid leukemia

Recently, somatic mutations of the nucleophosmin gene (NPM1), which alter the subcellular localization of the product, have been reported in acute myeloid leukemia (AML). We analyzed the clinical significance of NPM1 mutations in comparison with cytogenetics, FLT3, NRAS, and TP53 mutations, and a partial tandem duplication of the MLL gene (MLL-TD) in 257 patients with AML. We found NPM1 mutations, including 4 novel sequence variants, in 64 of 257 (24.9%) patients. NPM1 mutations were associated with normal karyotype and with internal tandem duplication (ITD) and D835 mutations in FLT3, but not with other mutations. In 190 patients without the M3 French-American-British (FAB) subtype who were treated with the protocol of the Japan Adult Leukemia Study Group, multivariate analyses showed that the NPM1 mutation was a favorable factor for achieving complete remission but was associated with a high relapse rate. Sequential analysis using 39 paired samples obtained at diagnosis and relapse showed that NPM1 mutations were lost at relapse in 2 of the 17 patients who had NPM1 mutations at diagnosis. These results suggest that the NPM1 mutation is not necessarily an early event during leukemogenesis or that leukemia clones with NPM1 mutations are sensitive to chemotherapy.