Prognostic value of FLT3 mutations among different cytogenetic subgroups in acute myeloid leukemia

BACKGROUND:

The impact of FMS‐like tyrosine kinase 3 (FLT3) mutations and mutation burden among cytogenetic subgroups of patients with acute myeloid leukemia (AML) other than normal karyotype (NK) AML is unclear.

METHODS:

Patients with newly diagnosed AML were divided among 3 cytogenetic subgroups: core binding factor (CBF) AML, NK‐AML, and poor‐risk AML.

RESULTS:

In total, 481 patients were included: 13% had, CBF‐AML, 57% had NK‐AML, and 30% had poor risk AML, and the frequency of any FLT3 mutations was 20%, 32%, and 7.6% in the respective cytogenetic subgroups. FLT3 mutation did not have an impact on event‐free survival (EFS) in patients with CBF‐AML (P = .84) and poor‐risk AML (P = .37). In patients with NK‐AML, EFS was worse in the FLT3‐internal tandem duplication (ITD) group (20 weeks vs 41 weeks; P < .00,001) but not in the FLT3‐tyrosine kinase domain (TKD) point mutation group (61 weeks vs 41 weeks; P = .15). Worse EFS and overall survival (OS) were observed among patients with NK‐AML and higher FLT3‐ITD burden but not among patients with FLT3‐TKD mutation. In multivariate analysis, FLT3‐ITD mutation was prognostic of EFS in patients with NK‐AML (hazard ratio, 3.1; P = .03).

CONCLUSIONS:

FLT3 mutations did not have a prognostic impact in patients with AML who had good‐risk and poor‐risk karyotypes. In patients with NK‐AML, FLT3‐ITD mutations led to worse survival, which was even worse among patients who had high mutation burden. Cancer 2011. © 2010 American Cancer Society.     

FLT3/ITD基因突变在不同血液肿瘤患者的表达及其临床意义

Objective:To analyze Fms-like tyrosine kinase 3(FLT3)/intemal-tandem duplications(ITD)murations in various kinds of hematologic malignancy patients.Methods:FLT3/ITD gene mutations were detected by polymerase chain reaction (PCR)in 103 acute myeloid leukemia(AML)cases,63 acute lymphocytic leukemia(ALL)cases,53 chronic myelogenous leukemia(CML)cases in chronic phase(CML-CP),34 CML cases in biast crisis(CML-BC),11 chronic lymphatic leukemia(CLL)cases,36 myelodysplastic syndrome (MDS)cases,9 multiple myeloma(MM)cases and 13 non-hodgkin's lymphoma (NHL)cases with marrow infiltration.Results:The expressions of FLT3/ITD gene mutations were detected in 22.3% AML cases.in 6.5%CML-BC cases.in 5.6%MDS cases and in 2.6%ALL cases.The two ALL cases with FLT3/ITD mutation were diagnosed as ALL-L2 with morphology and both with myeloid antigen expression,but finally were diagnosed as acute mixed-lineage leukemia after immunology examination.FLT3/ITD gene muIations were not detected in CML-CP,MM.NHL and CLL cases.In the 23 AML patients with FLT3/ITD gene mutation,including 2 of 8 M1(2.5%),8 of 33 M2(24-2%),7 of 24 M3(29.3%),2 of 11 M4(18.2%).3 of 21 M5(14.3%),1 of 5 M6(20%),and 0 of 1 M7 cases,and there were no significant differences in the positive rates of FLT3/ITD mutations between the FAB subtypes(P＞0.05).Statistical analyses showed that in AML patients,FLT3/ITD was associated with a higher pefipheral blood white cell(WBC)counts[(41.23±32.56)x 100/L vs (11.36±9.89)x109/L(P＜0.01)],higher percentage of bone marrow blast cells[(72.78±21.79)%vs(51.26±20.78)%(P＜0.05)],and higher cumulative relapse rates(63.6%vs 27.7%,P＜0.025)than those negative.Conclusion:FLT3/ITD gene mutation mainly pccurred in AML patients.and might be a strong prognostic factor which was associated with high peripheral WBC counts.bone marrow blast cell proportion and a increased relapse risk in AML.Detection of FLT3/ITD gene mutation might provide insights to explore a more accurate genotyping of leukemia,differential diagnosis between AML and ALL.subdivide risk level in AML and estimate prognosis of leukemia.     

Prognostic implication of gene mutations on overall survival in the adult acute myeloid leukemia patients receiving or not receiving allogeneic hematopoietic stem cell transplantations

Several gene mutations have been shown to provide clinical implications in patients with acute myeloid leukemia (AML). However, the prognostic impact of gene mutations in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains unclear. We retrospectively evaluated the clinical implications of 8 gene mutations in 325 adult AML patients; 100 of them received allo-HSCT and 225 did not. The genetic alterations analyzed included NPM1, FLT3-ITD, FLT3-TKD, CEBPA, RUNX1, RAS, MLL-PTD, and WT1. In patients who did not receive allo-HSCT, older age, higher WBC count, higher lactate dehydrogenase level, unfavorable karyotype, and RUNX1 mutation were significantly associated with poor overall survival (OS), while CEBPA double mutation (CEBPA^double-mut) and NPM1^mut/FLT3-ITD^neg were associated with good outcome. However, in patients who received allo-HSCT, only refractory disease status at the time of HSCT and unfavorable karyotype were independent poor prognostic factors. Surprisingly, RUNX1 mutation was an independent good prognostic factor for OS in multivariate analysis. The prognostic impact of FLT3-ITD or NPM1^mut/FLT3-ITD^neg was lost in this group of patients receiving allo-HSCT, while CEBPA^double-mut showed a trend to be a good prognostic factor. In conclusion, allo-HSCT can ameliorate the unfavorable influence of some poor-risk gene mutations in AML patients. Unexpectedly, the RUNX1 mutation showed a favorable prognostic impact in the context of allo-HSCT. These results need to be confirmed by further studies with more AML patients.     

Prognostic Impact of Concurrent DNMT3A,FLT3 and NPM1 Gene Mutations in Acute Myeloid Leukemia Patients

BackgroundAcute myeloid leukemia (AML) is one of the rapidly progressing malignancies which is characterized by unregulated proliferation of hematopoietic precursors. Technological improvements enhanced the availability of genetic AML biomarkers. The clinical relevance of these molecular markers for AML diagnosis, planning of therapy and risk stratification are increasing evidently.MethodsIn current study, one hundred newly diagnosed AML patients before receiving induction chemotherapy were included, they were subjected to clinical examination, cytochemical and morphological analysis of blood cells, flow cytometric, cytogenetic and molecular genetic analysis for detection of NPM1, FLT3-ITD and DNMT3A mutations. Direct sequencing analysis for detection of NPM1 and DNMT3A genes mutations were done. FLT3 /ITD gene mutation was detected by gel electrophoresis after PCR amplification.ResultsAccording to genetic markers, our AML patients are classified in to further 8groups. AML patients with three DNMT3A/FLT3/NPM1 gene mutations (AML ^{DNMT3A /FLT3/NPM1}) this group of patients presented with a heavy disease burden, had an elevated WBC in comparison to other groups (70 vs. 41 × 10³/μL; P = .019), and BM blast counts (71% vs. 55.6%, P < .02). When comparing eight groups for death event there were significant difference among groups; P = .005, group 1 (AML ^{DNMT3A /FLT3/NPM1}) showed rapid decline of the cumulative overall survival. There was a significant difference among 8 groups as regards response to treatment after 14 days (P = .02), group 7 AML with (DNMT3A +NMP1) gene mutations showed better response to treatment (100%), groups 1 and 3 AML with (NPM1+DNMT3A +NMP1) gene mutations and AML with isolated FLT3-ITD showed no response to treatment after 14 days. And as regards response to treatment after 28 days, the eight groups showed no significant difference (P = .14).ConclusionOur study supports adverse prognostic effect of presence of DNMT3A gene mutation either alone or in the presence of FLT3 and/or NPM1 gene mutations.     

Prevalence and Clinical Outcome of FMS-Like Tyrosine Kinase Mutations Among Patients With Core Binding Factor—Acute Myeloid Leukemia: Systematic Review and Meta-Analysis

BackgroundCore binding factor acute myeloid leukemia (CBF-AML) belongs to favorable risk group in AML. However, approximately 50% of patients with CBF-AML remain incurable and their outcomes are also determined by the various co-occurring mutations. Though, FMS-like tyrosine kinase-3(FLT3) mutation in AML is associated with poor survival, the prevalence and prognostic significance of FLT3 mutations among CBF-AML is unknown.Patients and MethodsWe performed a systematic review and meta-analysis to assess the prevalence of FLT3 mutations (ITD and TKD) among patients with CBF-AML. The pooled prevalence of FLT3 mutations was estimated for patients with CBF-AML, t(8;21) and Inv(16). Pooled odds ratio was calculated to compare the prevalence of various FLT3 mutations within the 2 subsets of CBF-AML. A random effects model was adopted for analysis when heterogenicity existed (P_{heterogenicity}< 0.05 or I² > 50%). Otherwise, a fixed effects model was used.ResultsThe pooled prevalence of any FLT3 mutations among patients with CBF-AML was available from 18 studies and was 13% (95% CI: 10%-16%; I² = 79%). Comparison of prevalence of FLT3 mutations between the 2 subgroups of CBF-AML showed that patients with t(8;21) had a higher prevalence of FLT3-ITD [pooled odds ratio(OR): 2.23 (95% CI:1.41-3.53, P < .01)] and lower prevalence of FLT3-TKD [pooled OR: 0.29 (95% CI:0.19-0.44; P < .01)] compared to patients with Inv(16). Additionally, we have discussed the prognostic significance of FLT3 mutations in CBF-AML patients.ConclusionThe prevalence of FLT3-TKD mutation was commoner among Inv(16) AML while FLT3-ITD mutation was commoner among t(8;21) AML. Uniform reporting of outcomes is essential to understand the prognostic significance of FLT3 mutations among CBF-AML.     

Fms Like Tyrosine Kinase (FLT3) and Nucleophosmin 1 (NPM1) Mutations in De Novo Normal Karyotype Acute Myeloid Leukemia (AML)

Mutations in FLT3 and NPM1 are important prognostic factors in AML, influencing outcome in normalkaryotype cases. We here analysed incidences of FLT3/ITD, D 835 and NPM1 mutations in patients with denovo normal karyotype AML using PCR and gene sequencing, along with laboratory parameters and treatmentoutcomes. There were 128 patients with a median age of 45 years (range, 19-65). FLT3/ITD mutations weredetected in 26 (20.3%), FLT3/D835 in 8 (6.2%) and NPM1 in 22 (17.1%). The incidence of FLT3/ITD was higherin those with elevated lactate dehydrogenase (LDH) and peripheral blasts (p=< 0.002, < 0.001) while NPM1mutations or both NPM1 and FLT3/ITD was more common in elevated total leukocyte counts (TLC), LDH andperipheral blasts (p=<0.0001). Complete response and disease free survival were lower in those with FLT3/ITDmutations (p=0.04, 0.03). The incidence of FLT3 and NPM1 mutations was found to be low in Indian patientswith normal karyotype AML.     

FLT3-TKD mutation in childhood acute myeloid leukemia.

Mutations of receptor tyrosine kinases are implicated in the constitutive activation and development of human hematologic malignancies. An internal tandem duplication (ITD) of the juxtamembrane domain-coding sequence of the FLT3 gene (FLT3-ITD) is found in 20-25% of adult acute myeloid leukemia (AML) and at a lower frequency in childhood AML. FLT3-ITD is associated with leukocytosis and a poor prognosis, especially in patients with normal karyotype. Recently, there have been three reports on point mutations at codon 835 of the FLT3 gene (D835 mutations) in adult AML. These mutations are located in the activation loop of the second tyrosine kinase domain (TKD) of FLT3 (FLT3-TKD). The clinical and prognostic relevance of the TKD mutations is less clear. To the best of our knowledge, there has been no report to describe FLT3-TKD mutations in childhood AML. In this pediatric series, FLT3-TKD mutations occurred in three of 91 patients (3.3%), an incidence significantly lower than that of FLT3-ITD (14 of 91 patients, 15.4%) in the same cohort of patients. None of them had both FLT3-TKD and FLT3-ITD mutations. Sequence analysis showed one each of D835 Y, D835 V, and D835 H. Of the three patients carrying FLT3-TKD, two had AML-M3 with one each of L- and V-type PML-RARalpha, and another one had AML-M2 with AML1-ETO. None of our patients with FLT3-TKD had leukocytosis at diagnosis. At bone marrow relapse, one of the four patients examined acquired FLT3-ITD mutation and none gained FLT3-TKD mutation.     

Cytoplasmic localization of nucleophosmin in bone marrow blasts of acute myeloid leukemia patients is not completely concordant with NPM1 mutation and is not predictive of prognosis

BACKGROUND:

Nucleophosmin (NPM1) gene mutations are reported to predict a favorable prognosis in acute myeloid leukemia (AML) patients. Aberrant cytoplasmic localization of nucleophosmin (NPM) protein is reported be a surrogate for NPM1 gene mutation.

METHODS:

Using immunohistochemical (IHC) analysis, we assessed for NPM (clone 376) expression in formalin‐fixed, formic acid‐decalcified bone marrow biopsy specimens. DNA sequencing of exon 12 of NPM1 gene was performed in 104 patients.

RESULTS:

The study included 252 AML patients: 192 de novo AML, 33 AML preceded by either myelodysplastic syndrome or chronic myelomonocytic leukemia, and 27 therapy‐related AML. The median age was 62 years and 115 patients were ≤60 years old. All patients received intensive chemotherapy. Cytoplasmic NPM was detected in 59 of 252 (23%) patients, including 48 of 192 (25%) de novo AML and 33 of 94 (35%) with a normal karyotype. DNA sequencing identified NPM1 mutations in 30 of 38 cases with cytoplasmic NPM and 10 of 66 cases with nuclear NPM. Cytoplasmic NPM was associated with young patient age (P = .024), FLT3/ITD (P = .005), CD34 negative blasts (P < .001), high peripheral blood blast count (P = .041), and high serum albumin level (P = .028). No statistical differences in overall or event‐free survival were found on the basis of NPM localization. Similar results were obtained in patients ≤60 years old with normal karyotype and wild‐type FLT3 (P = .768).

CONCLUSIONS:

IHC assessment for NPM localization did not predict prognosis in this patient cohort. The discordance between immunohistochemistry and DNA sequencing results indicates that DNA sequencing cannot be replaced by IHC assessment. Cancer 2009. © 2009 American Cancer Society.     

Analysis of FLT3 internal tandem duplication and D835 mutations in Chinese acute leukemia patients

Genomic aberrations of Fms-like tyrosine kinase 3 (FLT3), including internal tandem duplication (ITD) and point mutations, have been demonstrated in 25–30% of adults acute myeloid leukemia (AML) and are markers of poor prognosis. FLT3/ITD and D835 mutations were analyzed in 194 Chinese patients with acute leukemia and myelodysplastic syndromes (MDS) by polymerase chain reaction (PCR). FLT3/ITDs and D835 mutations were found in 25.9 and 6.3% of 143 AML patients, respectively. Two patients showed both ITD and point mutations. Among the FAB subtypes of AML, the rate of FLT3 aberration was significantly higher in M3 and M5. However, neither aberrations was found in 25 patients with acute lymphoblastic leukemia (ALL), 2 acute hybrid leukemia, 17 MDS and 7 chronic myeloid leukemia in blast crisis (CML-BC). FLT3/ITD was associated to leukocytosis and lower complete remission (CR) rate, and was more prevalent in patients with normal karyotype. In contrast, D835 mutation was not associated with leukocytosis or low CR rate. Our results confirm that FLT3 activating mutations also occur in a significant percentage in Chinese AML patients. FLT3/ITD⁺ patients treated with standard induction regimen could achieve lower complete remission rates compared with patients not harboring this defect. Early detection of FLT3 mutations and an intensification of induction therapy might thus be useful for this group of patients to overcome the poor prognosis.     

Nucleophosmin (NPM1) mutations in adult and childhood acute myeloid leukaemia: towards definition of a new leukaemia entity

Nucleophosmin (NPM) is a ubiquitously expressed chaperone protein that shuttles rapidly between the nucleus and cytoplasm, but predominantly resides in the nucleolus. It plays key roles in ribosome biogenesis, centrosome duplication, genomic stability, cell cycle progression and apoptosis. Somatic mutations in exon 12 of the NPM gene (NPM1) are the most frequent genetic abnormality in adult acute myeloid leukaemia (AML), found in approximately 35% of all cases and up to 60% of patients with normal karyotype (NK) AML. In children, NPM1 mutations are far less frequent, occurring in 8–10% of all AML cases, and in approximately 25% of those with a NK. NPM1 mutations lead to aberrant localization of the NPM protein into the cytoplasm, thus the designation, NPMc+ AML. NPMc+ AML is seen predominantly in patients with a NK and is essentially mutually exclusive of recurrent chromosomal translocations. Patients with NPM1 mutations are twice as likely as those who lack an NPM1 mutation to also have a FMS‐like tyrosine kinase (FLT3) internal tandem duplication (ITD) mutation. NPMc+ AML is also characterized by a unique gene expression signature and microRNA signature. NPMc+ AML has important prognostic significance, as NPMc+ AML, in the absence of a coexisting FLT3‐ITD mutation, is associated with a favourable outcome. NPM1 mutations have also shown great stability during disease evolution, and therefore represent a possible marker for minimal residual disease detection. Given its distinctive biologic and clinical features and its clear clinical relevance, NPMc+ AML is included as a provisional entity in the 2008 WHO classifications. There is still much to be learned about this genetic alteration, including its exact role in leukaemogenesis, how it interacts with other mutations and why it confers a more favourable prognosis. Further, it represents a potential therapeutic target warranting research aimed at identifying novel small molecules with activity in NPMc+ AML. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of FLT3‐internal tandem duplication allele burden and white blood cell count on the outcome in patients with intermediate‐risk karyotype acute myeloid leukemia

BACKGROUND:

In patients with acute myeloid leukemia (AML), testing for fms‐like tyrosine kinase‐3 (FLT3)–internal tandem duplication (FLT3‐ITD) and nucleophosmin‐1 (NPM1) mutations can allow for further prognostic subclassification, but less is known about the effects of FLT3‐ITD allele burden and presenting white blood cell count (WBC) within molecular subgroups.

METHODS:

The authors retrospectively assessed 206 adult patients who had AML with an intermediate‐risk karyotype and who received treatment on a uniform induction and consolidation chemotherapy regimen.

RESULTS:

The presenting WBC was a prognostic factor for survival only in patients who had an FLT3‐ITD mutation. On multivariate analysis, after correcting for age, WBC, secondary AML, and blast percentage, nucleophosmin‐1 (NPM1)‐mutated/FLT3‐ITD–negative patients had superior overall survival compared with patients in the other molecular subgroups. Patients who had FLT3‐ITD mutations had an inferior overall survival compared with patients who had NPM1 wild‐type/FLT3‐negative disease, and patients who had low or intermediate levels of the FLT‐ITD of mutant allele had overall and disease‐free survival similar to those in patients who had high‐level mutations.

CONCLUSIONS:

NPM1 and FLT3‐ITD status, age, WBC, and secondary AML were identified as important prognostic variables that can help to risk stratify patients with AML who have intermediate‐risk cytogenetics. FLT3 allele burden had no significant influence on outcomes after correcting for other variables. Cancer 2012. © 2012 American Cancer Society.     

Frequency of FLT3 Internal Tandem Duplications in Adult Syrian Patients with Acute Myeloid Leukemia and Normal Karyotype

Objective: Activating mutations of the fms-like tyrosine kinase 3 gene (FLT3) by internal tandem duplications (ITDs) in the juxtamembrane domain (JMD) have been reported in ~30% of adult acute myeloid leukemia (AML) patients with cytogenetically normal karyotype (CN). However, FLT3/ITD mutations are frequently accompanied with leukocytosis, high percentage of blasts in bone marrow (BM), and increased the risk of treatment failure in AML patients. FLT3-ITD mutated AML patients mainly with normal karyotype have higher relapse probability and shorter duration of complete remission (CR) after chemotherapy, so FLT3-ITD mutation is considered as an independent poor prognostic factor in AML. Methods: FLT3-ITD and FLT3-KTD were studied by polymerase chain reaction (PCR) and restriction fragment length polymorphism- PCR (RFLP-PCR) in 44 adults AML patients with cytogenetically normal karyotype (AML-CN) at diagnosis to characterize FLT3 status. The results were correlated with the prognostic factors. Results: In this study, FLT3-ITD mutations were identified in 7 (15.9%) of the 44 AML-CN patients. Among the 7 patients with FLT3/ITD mutations, 6 patients revealed a typical ITDs mutation (fragment size was 329 bp) and one patient showed untypical ITD mutation (fragment size was ~400 bp). Whereas 37 patients (61.7%) were FLT3-ITD. None of all AML-CN patients examined showed FLT3-KTD mutations. Conclusions: Our results support that FLT3-ITD are independent adverse prognostic factors for elderly AML-CN patients and are associated with low overall survival (OS), low rate of CR, high relapse rate (RR), and high percentage of BM blast at diagnosis. We concluded, FLT3 mutation analysis should be performed as a routine test in AML-CN patients.     

Acquisition of FLT3 or N-ras mutations is frequently associated with progression of myelodysplastic syndrome to acute myeloid leukemia.

The role of internal tandem duplication of fms-like tyrosine kinase 3 (FLT3/ITD), mutations at tyrosine kinase domain (FLT3/TKD) and N-ras mutations in the transformation of myelodysplastic syndrome (MDS) to AML was investigated in 82 MDS patients who later progressed to AML; 70 of them had paired marrow samples at diagnosis of MDS and AML available for comparative analysis. Five of the 82 patients had FLT3/ITD at presentation. Of the 70 paired samples, seven patients acquired FLT3/ITD during AML evolution. The incidence of FLT3/ITD at diagnosis of MDS was significantly lower than that at AML transformation (3/70 vs 10/70, P<0.001). FLT3/ITD(+) patients progressed to AML more rapidly than FLT3/ITD(-) patients (2.5+/-0.5 vs 11.9+/-1.5 months, P=0.114). FLT3/ITD(+) patients had a significantly shorter survival than FLT3/ITD(-) patients (5.6+/-1.3 vs 18.0+/-1.7 months, P=0.0008). After AML transformation, FLT3/ITD was also associated with an adverse prognosis. One patient had FLT3/TKD mutation (D835Y) at both MDS and AML stages. Additional three acquired FLT3/TKD (one each with D835 H, D835F and I836S) at AML transformation. Five of the 70 matched samples had N-ras mutation at diagnosis of MDS compared to 15 at AML transformation (P<0.001), one lost and 11 gained N-ras mutations at AML progression. Coexistence of FLT3/TKD and N-ras mutations was found in two AML samples. N-ras mutations had no prognostic impact either at the MDS or AML stage. Our results show that one-third of MDS patients acquire activating mutations of FLT3 or N-ras gene during AML evolution and FLT3/ITD predicts a poor outcome in MDS.     

CEBPA mutations in younger adults with acute myeloid leukemia and normal cytogenetics: prognostic relevance and analysis of cooperating mutations.

PURPOSE: To assess the prognostic relevance of mutations in the CEBPA gene encoding CCAAT/enhancer binding protein alpha (C/EBP alpha) in a large prospective series of younger adults with acute myeloid leukemia (AML) and normal cytogenetics. PATIENTS AND METHODS: The entire CEBPA coding region was sequenced in diagnostic samples from 236 AML patients 16 to 60 years of age with normal cytogenetics who were uniformly treated on two consecutive protocols of the AML Study Group Ulm, and CEBPA mutation status was correlated with clinical outcome. RESULTS: CEBPA mutations were detected in 36 (15%) of 236 patients. Twenty-one (9%) of 236 patients had mutations predicted to result in loss of C/EBP alpha function. Remission duration and overall survival (OS) were significantly longer for the 36 patients with CEBPA mutations (P =.01 and P =.05, respectively). On multivariate analysis, wild-type CEBPA was an independent prognostic marker affecting remission duration (hazard ratio, 2.85; P =.01) and OS (hazard ratio, 1.87; P =.04). Analysis of cooperating mutations (both types of activating FLT3 mutations and MLL partial tandem duplications) showed that FLT3 mutations had no significant prognostic influence in patients with CEBPA mutations. Furthermore, there was no significant overlap between the subgroup of patients with CEBPA mutation with predicted loss of C/EBP alpha function and patients with FLT3 or MLL mutations, suggesting that CEBPA loss-of-function mutations define a distinct biologic subclass of AML with normal cytogenetics. CONCLUSION: Mutant CEBPA predicts favorable prognosis and may improve risk stratification in AML patients with normal cytogenetics.     

Heterogeneous patterns of FLT3 Asp(835) mutations in relapsed de novo acute myeloid leukemia: a comparative analysis of 120 paired diagnostic and relapse bone marrow samples.

PURPOSE: We analyzed Asp(835) mutations of FLT3 on paired marrow samples at diagnosis and relapse from 120 adult patients with de novo acute myeloid leukemia (AML) to determine the role of FLT3 Asp(835) mutation in the relapse of AML. EXPERIMENTAL DESIGN: Asp(835) mutation was analyzed by DNA PCR amplification of exon 20 of FLT3 gene followed by EcoRV digestion. All of the mutations were confirmed by sequence analysis. Mutant to wild-type allelic ratio was determined by Genescan analysis. The Expand Long Template PCR System was used to determine the allelic location of internal tandem duplication of FLT3 (FLT3/ITD) and Asp(835) mutations. RESULTS: Thirteen patients had Asp(835) mutations at diagnosis, of them 8 lost the mutations at relapse, and the remaining 5 patients carrying Asp(835) mutations at diagnosis relapsed with the identical mutation types. Another 6 patients acquired Asp(835) mutations at relapse. Five samples harbored both FLT3/ITD and Asp(835) mutations that were found on different alleles by cloning analysis in the 3 patients studied. There were no differences in WBC count, French-American-British subtype, percentage of marrow blasts, or circulating blasts between patients with and without Asp(835) mutations, whereas the difference in the prevalence of Asp(835) mutations among cytogenetic/molecular subgroups was statistically significant (P = 0.025). CONCLUSIONS: The present study showed that patients with AML had heterogeneous patterns of FLT3 Asp(835) mutations, either acquisition or loss of the mutations at relapse. Asp(835) mutant clone may develop as a secondary event in a subset of patients with AML.     

Mutational analysis of DNMT3A improves the prognostic stratification of patients with acute myeloid leukemia

Nucleophosmin1 (NPM1) mutations are the most frequently detected gene mutations in acute myeloid leukemia (AML) and are considered a favorable prognostic factor. We retrospectively analyzed the prognosis of 605 Japanese patients with de novo AML, including 174 patients with NPM1-mutated AML. Although patients with NPM1-mutated AML showed a high remission rate, this was not a favorable prognostic factor for overall survival (OS); this is contrary to generally accepted guidelines. Comprehensive gene mutation analysis showed that mutations in codon R882 of DNA methyltransferase 3A (DNMT3A^R882 mutations) were a strong predicative factor indicating poor prognosis in all AML (p < 0.0001) and NPM1-mutated AML cases (p = 0.0020). Furthermore, multivariate analysis of all AML cases showed that DNMT3A^R882 mutations and the co-occurrence of internal tandem duplication in FMS-like tyrosine kinase 3 (FLT3-ITD), NPM1 mutations, and DNMT3A^R882 mutations (triple mutations) were independent factors predicting a poor prognosis related to OS, with NPM1 mutations being an independent factor for a favorable prognosis (hazard ratios: DNMT3A^R882 mutations, 1.946; triple mutations, 1.992, NPM1 mutations, 0.548). Considering the effects of DNMT3A^R882 mutations and triple mutations on prognosis and according to the classification of NPM1-mutated AML into three risk groups based on DNMT3A^R882/FLT3-ITD genotypes, we achieved the improved stratification of prognosis (p < 0.0001). We showed that DNMT3A^R882 mutations are an independent factor for poor prognosis; moreover, when confounding factors that include DNMT3A^R882 mutations were excluded, NPM1 mutations were a favorable prognostic factor. This revealed that ethnological prognostic discrepancies in NPM1 mutations might be corrected through prognostic stratification based on the DNMT3A status.     

老年急性髓细胞白血病患者FLT3-ITD基因突变的临床意义

 目的　分析老年急性髓细胞白血病（AML）Fms样酪氨酸激酶3内部串联重复序列（FLT3-ITD）基因突变及其临床意义。方法　采用聚合酶链反应-变性高效液相色谱技术（PCR-DHPLC）分析30例初发老年AML患者骨髓单个核细胞FLT3-ITD突变。结果　30例老年AML患者FLT3-ITD突变阳性率26.67 %（8／30）,对照组均未检测到该突变;FAB各亚型FLT3-ITD突变率不同,有M3型突变率较高的趋势;所检测到FLT3-ITD突变均为杂合突变,突变均在阅读框内;不同预后核型组FLT3-ITD突变阳性率不同,预后中等核型组突变率较高,达40.0 %（6／15）;显示FLT3-ITD突变阳性者具有高白细胞、白血病细胞、完全缓解（CR）率低等临床特点。结论　FLT3-ITD突变阳性老年AML患者预后差,且多发生于预后中等核型组;FLT3-ITD突变检测在一定程度上可以弥补细胞遗传学的不足,有可能成为老年AML患者常规检测项目,以指导治疗判断预后。