异基因造血干细胞移植治疗Fms样酪氨酸激酶3基因内部串联重复(FLT3-ITD)阳性的急性髓性白血病的疗效分析

 目的 分析异基因造血干细胞移植(allo-HSCT)治疗伴有Fms样酪氨酸激酶3基因内部串联重复(FLT3-ITD)阳性的急性髓性白血病(AML)的疗效,探讨不同移植方式及疾病状态对该类患者预后的影响。方法 2006年10月至2012年10月在苏州大学附属第一医院行allo-HSCT的AML患者共314例,其中FLT3-ITD阳性54例,回顾性分析allo-HSCT对FLT3-ITD阳性AML患者的临床疗效。结果 54例FLT3-ITD阳性患者3年总生存(OS)率为56%, 3年无白血病生存(LFS)率为47%。其中同胞人类白细胞抗原(HLA)全相合及亲缘HLA单倍型相合造血干细胞移植的患者3年OS率分别为56%和60%,3年LFS率为45%和54%。两组在OS时间及LFS时间方面的差异均无统计学意义(χ²=0.074,P=0.786; χ²=0.006,P=0.941)。47例(87.0%)患者移植前本病处于首次完全缓解(CR1),7例(13.0%)患者移植前本病处于非CR1期。处于CR1期的患者的生存显著优于非CR1期患者。结论 allo-HSCT是FLT3-ITD阳性AML患者的有效治疗方法,亲缘HLA单倍型相合造血干细胞移植与同胞HLA全相合移植疗效相似。疾病复发是影响其疗效的主要因素。
        

Different clinical importance of FLT3 internal tandem duplications in AML according to FAB classification: possible existence of distinct leukemogenesis involving monocyte differentiation pathway

Impact of FLT3 receptor tyrosine kinase activation via internal tandem duplication (ITD) of the juxtamembrane region on outcome of acute myeloid leukemia (AML) is still controversial. Recent researches reveal a role of FLT3 in monocyte differentiation in hematopoiesis. We analyzed the clinical impact of FLT3 alterations in adult AML patients excluding acute promyelocytic leukemia (APL) who received induction chemotherapy according to morphologic classification. Retrospective review of medical records from three centers in Korea between 1997 and 2007 was performed. Polymerase chain reaction was performed on genomic DNA derived from blood samples of patients before induction chemotherapy for FLT3-ITD detection. We assessed overall survival (OS), first disease-free survival (1-DFS), and response to induction chemotherapy. One hundred eighty-four patients (median age 49.1 years, range 16.0–76.5) with AML excluding APL received induction chemotherapy from three centers. FLT3-ITD was detected in 22 patients. One hundred forty-one patients were below age 60. One hundred seventy-nine patients received induction chemotherapy with cytarabine and idarubicin (AId) regimen. One hundred nineteen patients achieved complete remission (CR) after first induction chemotherapy. FLT3-ITD was not related to achievement of CR. 1-DFS was longer in patients without FLT3-ITD (median 1-DFS 16.5 vs. 8.5 months, p?=?0.025). 1-DFS was not different according to FLT3-ITD status in nonmonocyte lineage leukemia (p?=?0.355), while 1-DFS was shorter in monocyte lineage leukemia for FLT3-ITD positive patients (20.9 vs. 2.4 months, p?<?0.001). FLT3-ITD had no impact on OS except for monocyte lineage, where OS was significantly shorter in FLT3-ITD positive group (39.4 vs. 6.0 months, p?=?0.026). Moreover FLT3-ITD was stronger prognostic factors in monocyte lineage AML than risk stratification based on cytogenetics. Status of FLT3-ITD should be analyzed differently in AML patients according to morphologic profile. FLT3-ITD is a predictive and prognostic marker only in monocyte lineage patients. This result suggests an existence of distinct subset of monocyte lineage AML with leukemogenesis involving FLT3 activating pathway.     

Prognostic implications of NPM1 mutations and FLT3 internal tandem duplications in Egyptian patients with cytogenetically normal acute myeloid leukemia

Nucleophosmin (NPM1) and fms-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) gene mutations represent the most frequent molecular aberrations in patients with cytogenetically normal-acute myeloid leukemia (CN-AML). We analyzed the prognostic impact of these mutations and their interactions in adults with CN-AML. NPM1 mutation (NPM1mut) and FLT3-ITD mutation (FLT3-ITD+) were analyzed by polymerase chain reaction and GeneScan assays of bone marrow samples obtained from newly diagnosed 104 CN-AML patients. FLT3-ITD+ and NPM1mut were detected in 36 (34.6%) and 30 (28.8%) out of 104 subjects, respectively, 16 cases (15.4%) had double NPM1mut/FLT3-ITD+. The incidence of FLT3-ITD+ was significantly higher in the NPM1mut group than in the NPM1 wild (NPM1wt) group (P = 0.018). Statistical analysis revealed that isolated NPM1mut group had a better clinical outcomes in terms of higher complete response (CR) rate (P = 0.01) and a trend towards favorable overall survival (OS) and disease-free survival (DFS) (P = 0.28, 0.40, respectively). In contrast, the isolated FLT3-ITD+ group had an unfavorable outcome in terms of lower CR rate (P = 0.12), shorter OS, and DFS (P < 0.0001 for both). The NPM1mut/FLT3-ITD-group had the best OS and DFS, while the NPM1wt/FLT3-ITD+ group had the worst OS and DFS than other groups (NPM1mut/FLT3-ITD+ or NPM1wt/FLT3-ITD?) (P < 0.0001 for both). Multivariate Cox regression analysis showed that age and FLT3/ITD+ were independent poor prognostic factors for OS (P = 0.006, <0.0001, respectively), while FLT3/ITD+ was independent predictor for DFS (P = 0.04). However, NPM1mut did not have a significant impact on OS and DFS. In conclusion, adult patients with CN-AML carrying isolated NPM1mut and isolated FLT3-ITD+ exhibit different clinical outcomes than those with NPM1mut/FLT3-ITD+ or NPM1wt/FLT3-ITD?. Patients with NPM1mut/FLT3-ITD? had the best prognosis in terms of higher CR, OS, and DFS, while those with NPM1mut/FLT3-ITD+ had the worst CR rate, and NPM1wt/FLT3-ITD+ had the lowest OS and DFS.     

Relapse risk and survival in patients with FLT3 mutated acute myeloid leukemia undergoing stem cell transplantation

In patients with AML with FMS‐like tyrosine kinase 3 (FLT3) mutations, the significance of minimal residual disease (MRD) detected by PCR before allogeneic stem cell transplantation (SCT) on outcomes after transplant remains unclear. We identified 200 patients with FLT3‐AML who underwent SCT at our institution. Disease status at transplant was: first or second complete remission (CR1/CR2, n = 119), high‐risk CR (third or subsequent CR, marrow hypoplasia, or incomplete count recovery) (CR‐HR, n = 31), and morphological evidence of active disease (AD, n = 50). The median follow‐up was 27 months, and the 2‐year overall and progression‐free survival were 43% and 41%, respectively. Relapse was highest in the AD group (85%) and the CR‐HR FLT3 MRD positive group (72%), followed by CR‐HR FLT3 MRD negative (58%), CR1/CR2 FLT3 MRD positive (39%), and lowest in the CR1/CR2 FLT3 MRD negative group (23%). On multivariate analysis, independent factors influencing the risk of relapse were detectable morphological disease and FLT3 MRD by PCR pre‐transplant. Factors that did not influence the relapse risk included: age, graft type, graft source, type of FLT3 mutation, or conditioning intensity. Morphologic and molecular remission status at the time of transplant were key predictors of disease relapse and survival in patients with FLT3‐AML.     

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。     

SU11248 is a novel FLT3 tyrosine kinase inhibitor with potent activity in vitro and in vivo

FLT3 (fms-related tyrosine kinase/Flk2/Stk-2) is a receptor tyrosine kinase (RTK) primarily expressed on hematopoietic cells. In blasts from acute myelogenous leukemia (AML) patients, 2 classes of FLT3 activating mutations have been identified: internal tandem duplication (ITD) mutations in the juxtamembrane domain (25%-30% of patients) and point mutations in the kinase domain activation loop (7%-8% of patients). FLT3-ITD mutations are the most common molecular defect identified in AML and have been shown to be an independent prognostic factor for decreased survival. FLT3-ITD is therefore an attractive molecular target for therapy. SU11248 is a recently described selective inhibitor with selectivity for split kinase domain RTKs, including platelet-derived growth factor receptors, vascular endothelial growth factor receptors, and KIT. We show that SU11248 also has potent activity against wild-type FLT3 (FLT3-WT), FLT3-ITD, and FLT3 activation loop (FLT3-Asp835) mutants in phosphorylation assays. SU11248 inhibits FLT3-driven phosphorylation and induces apoptosis in vitro. In addition, SU11248 inhibits FLT3-induced VEGF production. The in vivo efficacy of SU11248 was investigated in 2 FLT3-ITD models: a subcutaneous tumor xenograft model and a bone marrow engraftment model. We show that SU11248 (20 mg/kg/d) dramatically regresses FLT3-ITD tumors in the subcutaneous tumor xenograft model and prolongs survival in the bone marrow engraftment model. Pharmacokinetic and pharmacodynamic analysis in subcutaneous tumors showed that a single administration of an efficacious drug dose potently inhibits FLT3-ITD phosphorylation for up to 16 hours following a single dose. These results suggest that further exploration of SU11248 activity in AML patients is warranted.     

Prognostic significance of baseline FLT3-ITD mutant allele level in acute myeloid leukemia treated with intensive chemotherapy with/without sorafenib

Internal tandem duplication (ITD) of the fms-related tyrosine kinase-3 gene (FLT3) confer a poor prognosis in adult AML. Studies have reported that a higher mutant allelic burden is associated with a worse prognosis. Adult patients with FLT3-ITD mutated AML treated at our institution were identified. Patients were assigned into 2 groups; patients who received idarubicin and cytarabine (IA, group one) containing induction, and who received sorafenib in addition to IA containing regimens at induction (group two). The optimal FLT3-ITD mutant allele cut-off was defined as the cut-off to divide the whole cohort with the highest statistical significance. A total of 183 patients including 104 (57%) in group one and 79 (43%) in group two were identified. The complete remission (CR)/CR with incomplete hematologic recovery (CRi) for group one and group two were 85% and 99%, respectively (P = .004). The median relapse free survival (RFS) for group one and two were 12 and 45 months, respectively (P = .02). The median overall survival (mOS) was 17 months in group one, and has not been reached in group two (P = .008). The optimal FLT3-ITD mutant allele cut-off for OS was 6.9% in group one, there was no optimal cut-off in group two. On multivariate analysis, poor performance status (PS) (P = .003), sorafenib (P = .01), and presenting white blood cells (WBC) (P < .001) were independent predictors of OS. Higher FLT3-ITD allele burden is associated with a worse outcome in patients treated with IA-based chemotherapy. Addition of sorafenib to chemotherapy not only nullifies the negative prognostic impact of higher allele burden, but also improves outcome of FLT3-ITD mutated AML patients regardless of the allele burden.     

Non-A type nucleophosmin 1 gene mutation predicts poor clinical outcome in de novo adult acute myeloid leukemia: differential clinical importance of NPM1 mutation according to subtype

Mutations of nucleophosmin gene (NPM1) are known to be related to good prognosis in AML patients lacking FLT3 internal tandem duplication (FLT3-ITD). Recently, NPM1 mutations other than type A were reported, but their clinical significance is not well known. Retrospective medical record review of 106 de novo AML patients lacking FLT3-ITD, who received induction chemotherapy from three centers in Korea between 1997 and 2007, was performed. Direct sequencing of NPM1 and RT-PCR for FLT3-ITD was performed on genomic DNA derived from blood samples of patients before induction chemotherapy for detection of mutations. NPM1 mutation was detected in 18 patients, where 13 were type A mutants and 5 were non-type A mutants. CR, CR1-D and OS was not different according to NPM1 mutational status overall. But, non-type A NPM1 mutation was related to shorter CR1-D when compared with NPM1 wild types and NPM1 type A mutation (p = 0.004). OS was shorter in non-type A mutants when compared with NPM1 wild-type patients and NPM1 type A mutants (p = 0.001). The type of mutation of NPM1 is important for prognosis in de novo AML lacking FLT3-ITD. Non-A type NPM1 mutation is a poor prognostic factor.     

Allogeneic compared with autologous stem cell transplantation in the treatment of patients younger than 46 years with acute myeloid leukemia (AML) in first complete remission (CR1): an intention-to-treat analysis of the EORTC/GIMEMAAML-10 trial

In the European Organization for Research and Treatment of Cancer Leukemia Group and Gruppo Italiano Malattie Ematologiche dell' Adulto (EORTC-LG/GIMEMA) acute myeloid leukemia (AML)-10 trial, patients in first complete remission (CR1) received a single intensive consolidation (IC) course. Subsequently, those patients younger than 46 years with an HLA-identical sibling donor were assigned to undergo allogeneic (allo) stem cell transplantation (SCT), and patients without such a donor were planned for autologous (auto) SCT. Between November 1993 and December 1999, of 1198 patients aged younger than 46 years, 822 achieved CR. The study group constituted 734 patients who received IC: 293 had a sibling donor and 441 did not. Allo-SCT and auto-SCT were performed in 68.9% and 55.8%, respectively. Cytogenetic determination was successfully performed in 446 patients. Risk groups were good (t(8;21), inv16), intermediate (NN or -Y only), and bad/very bad (all others). Median follow-up was 4 years; 289 patients relapsed, 66 died in CR1, and 293 died. Intention-to-treat analysis revealed that the 4-year disease-free survival (DFS) rate of patients with a donor versus those without a donor was 52.2% versus 42.2%, P =.044; hazard ratio = 0.80, 95% confidence interval (0.64, 0.995), the relapse incidence was 30.4% versus 52.5%, death in CR1 was 17.4% versus 5.3%, and the survival rate was 58.3% versus 50.8% (P =.18). The DFS rates in patients with and without a sibling donor were similar in patients with good/intermediate risk but were 43.4% and 18.4%, respectively, in patients with bad/very bad risk cytogenetics. In younger patients (15-35 years), the difference was more pronounced. The strategy to perform early allo-SCT led to better overall results than auto-SCT, especially for younger patients or those with bad/very bad risk cytogenetics.     

Activating internal tandem duplication mutations of the fms-like tyrosine kinase-3 (FLT3-ITD) at complete response and relapse in patients with acute myeloid leukemia

FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutations are among the most frequent molecular aberrations in patients with acute myeloid leukemia. We retrospectively analyzed 324 patients with acute myeloid leukemia treated with front-line induction chemotherapy between October 2004 and March 2010. Fifty-six patients had FLT3-ITD mutation at diagnosis. Fifty-one (91%) patients with FLT3-ITD achieved complete remission. Thirteen patients had FLT3 analysis at complete remission. None had FLT3-ITD. Twenty-five (49%) patients with FLT3-ITD relapsed. Of these, 13 (52%) had FLT3-ITD at relapse (3 negative and 9 not done). Among the 201 patients without FLT3-ITD at diagnosis who achieved complete remission, 77 (38%) relapsed among whom 8 (10%) patients acquired FLT3-ITD clone. We conclude that FLT3-ITD mutations are unstable at follow up and may occur for the first time at relapse. Therefore, FLT3-ITD is not a reliable marker for minimal residual disease in acute myeloid leukemia.     

Second allogeneic hematopoietic SCT for relapsed ALL in children

A second SCT is generally accepted as the only potentially curative approach for ALL patients that relapse after SCT, but the role of second SCT for pediatric ALL is not fully understood. We performed a retrospective analysis of 171 pediatric patients who received a second allo-SCT for relapsed ALL after allo-SCT. OS at 2 years was 29.4±3.7%, the cumulative incidence of relapse was 44.1±4.0% and non-relapse mortality was 18.8±3.5%. Relapse occurred faster after the second SCT than after the first SCT (117 days vs 164 days, P=0.04). Younger age (9 years or less), late relapse (180 days or more after first SCT), CR at the second SCT, and myeloablative conditioning were found to be related to longer survival. Neither acute GVHD nor the type of donor influenced the outcome of second SCT. Multivariate analysis showed that younger age and late relapse were associated with better outcomes. Our analysis suggests that second SCT for relapsed pediatric ALL is an appropriate treatment option for patients that have achieved CR, which is associated with late relapse after the first SCT.     

Expression of myeloperoxidase and gene mutations in AML patients with normal karyotype: double CEBPA mutations are associated with high percentage of MPO positivity in leukemic blasts

The percentage of myeloperoxidase (MPO)-positive blast cells is a simple and highly significant prognostic factor in AML patients. It has been reported that the high MPO group (MPO-H), in which >50% of blasts are MPO activity positive, is associated with favorable karyotypes, while the low MPO group (≤50% of blasts are MPO activity positive, MPO-L) is associated with adverse karyotypes. The MPO-H group shows better survival even when restricted to patients belonging to the intermediate chromosomal risk group or those with a normal karyotype. It has recently been shown that genotypes defined by the mutational status of NPM1, FLT3, and CEBPA are associated with treatment outcome in patients with cytogenetically normal AML. In this study, we aimed to evaluate the relationship between MPO positivity and gene mutations found in normal karyotypes. Sixty AML patients with normal karyotypes were included in this study. Blast cell MPO positivity was assessed in bone marrow smears stained for MPO. Associated genetic lesions (the NPM1, FLT3-ITD, and CEBPA mutations) were studied using nucleotide sequencing. Thirty-two patients were in the MPO-L group, and 28 patients in the MPO-H group. FLT3-ITD was found in 11 patients (18.3%), NPM1 mutations were found in 19 patients (31.7%), and CEBPA mutations were found in 11 patients (18.3%). In patients with CEBPA mutations, the carrying two simultaneous mutations (CEBPA (double-mut)) was associated with high MPO expression, while the mutant NPM1 without FLT3-ITD genotype was not associated with MPO activity. Both higher MPO expression and the CEBPA (double-mut) genotype appeared to be associated with improved overall survival after intensive chemotherapy. Further studies are required to determine the importance of blast MPO activity as a prognostic factor, especially in CEBPA wild-type patients with a normal karyotype.     

SRC is a signaling mediator in FLT3-ITD- but not in FLT3-TKD-positive AML

Mutations of Fms-like tyrosine kinase 3 (FLT3) are among the most frequently detected molecular abnormalities in AML patients. Internal tandem duplications (ITDs) are found in approximately 25% and point mutations within the second tyrosine kinase domain (TKD) in approximately 7% of AML patients. Patients carrying the FLT3-ITD but not the FLT3-TKD mutation have a significantly worse prognosis. Therefore, both FLT3 mutations seem to exert different biologic functions. FLT3-ITD but not FLT3-TKD has been shown to induce robust activation of the STAT5 signaling pathway. In the present study, we investigated the mechanisms leading to differential STAT5 activation and show that FLT3-ITD but not FLT3-TKD uses SRC to activate STAT5. Coimmunoprecipitation and pull-down experiments revealed an exclusive interaction between SRC but not other Src family kinases and FLT3-ITD, which is mediated by the SRC SH2 domain. We identified tyrosines 589 and 591 of FLT3-ITD to be essential for SRC binding and subsequent STAT5 activation. Using site-specific Abs, we found that both residues were significantly more strongly phosphorylated in FLT3-ITD compared with FLT3-TKD. SRC inhibition and knock-down blocked STAT5 activation and proliferation induced by FLT3-ITD but not by FLT3-TKD. We conclude that SRC might be a therapeutic target in FLT3-ITD(+) AML.     

Characteristics and outcome of patients with core-binding factor acute myeloid leukemia and FLT3-ITD: results from an international collaborative study

The aim of this study was to evaluate the prognostic impact of FLT3-ITD in core-binding factor acute myeloid leukemia (CBFAML) in an international, multicenter survey of 97 patients of whom 52% had t(8;21)(q22;q22) and 48% had inv(16)(p13q22)/t(16;16)(p13;q22). The median age of the patients was 53 years (range, 19-81). Complete remission after anthracycline-based induction (n=86) and non-intensive therapy (n=11) was achieved in 97% and 36% of the patients, respectively. The median follow-up was 4.43 years (95% confidence interval [95% CI]: 3.35-7.39 years). The median survival after intensive and non-intensive treatment was not reached and 0.96 years, respectively. Among intensively treated patients, inv(16) with trisomy 22 (n=11) was associated with a favorable 4-year relapse-free survival rate of 80% (95% CI: 59-100%) as compared to 38% (95% CI: 27-54%; P=0.02) in all other patients with CBFAML/ FLT3-ITD (n=75). Overall, 24 patients underwent allogeneic hematopoietic cell transplantation (HCT), 12 in first complete remission and 12 after relapse. Allogeneic HCT in first complete remission was not beneficial (P=0.60); however, allogeneic HCT seemed to improve median survival in relapsed patients compared to that of patients treated with chemotherapy (not reached vs. 0.6 years, respectively; P=0.002). Excluding patients with inv(16) with trisomy 22, our data indicate that the outcome of CBF-AML patients with FLT3-ITD may be inferior to that of patients without FLT3-ITD (based on previously published data), suggesting that prognostically CBF-AML patients with FLT3-ITD should not be classified as favorable-risk. FLT3-inhibitors may improve the outcome of these patients.     

Complex karyotype,older age,and reduced first‐line dose intensity determine poor survival in core binding factor acute myeloid leukemia patients with long‐term follow‐up

Approximately 40% of patients affected by core binding factor (CBF) acute myeloid leukemia (AML) ultimately die from the disease. Few prognostic markers have been identified. We reviewed 192 patients with CBF AML, treated with curative intent (age, 15–79 years) in 11 Italian institutions. Overall, 10‐year overall survival (OS), disease‐free survival (DFS), and event‐free survival were 63.9%, 54.8%, and 49.9%, respectively; patients with the t(8;21) and inv(16) chromosomal rearrangements exhibited significant differences at diagnosis. Despite similar high complete remission (CR) rate, patients with inv(16) experienced superior DFS and a high chance of achieving a second CR, often leading to prolonged OS also after relapse. We found that a complex karyotype (i.e., ≥4 cytogenetic anomalies) affected survival, even if only in univariate analysis; the KIT D816 mutation predicted worse prognosis, but only in patients with the t(8;21) rearrangement, whereas FLT3 mutations had no prognostic impact. We then observed increasingly better survival with more intense first‐line therapy, in some high‐risk patients including autologous or allogeneic hematopoietic stem cell transplantation. In multivariate analysis, age, severe thrombocytopenia, elevated lactate dehydrogenase levels, and failure to achieve CR after induction independently predicted longer OS, whereas complex karyotype predicted shorter OS only in univariate analysis. The achievement of minimal residual disease negativity predicted better OS and DFS. Long‐term survival was observed also in a minority of elderly patients who received intensive consolidation. All considered, we identified among CBF AML patients a subgroup with poorer prognosis who might benefit from more intense first‐line treatment. Am. J. Hematol. 90:515–523, 2015. © 2015 Wiley Periodicals, Inc.     

Prevalence and Clinical Significance of FLT3 and NPM1 Mutations in Acute Myeloid Leukaemia Patients of Assam,India

Acute Myeloid Leukaemia (AML) is one of the common forms of haematological malignancy in adults. We analysed the prevalence and clinical significance of FMS-like tyrosine kinase 3 (FLT3) and Nucleophosmin 1 (NPM1) mutations in AML patients of North East India. Co-prevalence and clinical significance of three recurrent chromosomal translocations namely t(15; 17), t(8; 21), t(16; 16) and expression of epidermal growth factor receptor (EGFR), flow markers were also documented and co-related with disease progress. We analysed bone marrow aspirates or peripheral blood samples from 165 newly diagnosed AML patients. All clinical samples were analysed by Real Time PCR and DNA sequencing based assays. NPM1 was the most frequently detected mutation in the study population (46/165 = 27.90%, 95% CI 20.75–35.05). FLT3 mutations were detected in 27/165 (16.40%, 95% CI 10.45–22.35) patients with internal tandem duplication (FLT3-ITD) in 24/165 (14.60%, 95% CI 8.91–20.29) and FLT3-D835 in 3/165 (1.80%, 95% CI 0–4.13) patients. NPM1 mutations were associated with a higher complete remission rate and longer overall survival (P < 0.01) compared to FLT3-ITD whereas FLT3-ITD showed adverse impact with poor survival rate (P < 0.01), leukocytosis (P < 0.01) and a packed bone marrow. EGFR expression was more in patients with NPM1 mutation compared to FLT3 mutation (P = 0.09). Patients with FLT3 and NPM1 mutations uniformly expressed CD13 and CD33 whereas CD34 was associated with poor prognosis (P ≤ 0.01) in patients with NPM1 mutation. FLT3-ITD was associated with inferior overall survival. However the clinical significance of FLT3-D835 was not clear due to small number of samples. NPM1 mutation showed better prognosis with increased response to treatment in the absence of FLT3-ITD.     

T‐cell replete haploidentical stem cell transplantation attenuates the prognostic impact of FLT3‐ITD in acute myeloid leukemia: A report from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Acute myeloid leukemia (AML) patients harboring the FLT3‐ITD mutation are considered a high risk patient subset preferentially allocated for allogeneic stem cell transplantation in first remission. Whether FLT3‐ITD retains a prognostic role in haploidentical stem cell transplantation (haplo‐SCT) is unknown. To analyze the prognostic impact of FLT3‐ITD in haplo‐SCT, we performed a retrospective analysis of the multicenter registry of the acute leukemia working party of the European Society for Blood and Marrow Transplantation. We included all adult AML patients with known FLT3 status who underwent a first T‐cell replete related haplo‐HCT in first complete remission from 2005 to 2016. We evaluated 293 patients of whom 202 were FLT3^wt and 91 were FLT3‐ITD mutated. FLT3‐ITD patients were more likely to be NPM1 mutated as well as be in the intermediate risk cytogenetic risk category. In multivariate analysis, patients with FLT3‐ITD had comparable rates of relapse incidence [Hazard ratio (HR) = 1.34, confidence interval (CI) 95%, 0.67‐2.7; P = .9] and leukemia‐free survival (HR = 0.99, CI 95%, 0.62‐1.57; P = .9) to those of FLT3^wt patients. Overall survival, the incidence of nonrelapse mortality, and graft versus host disease‐free/relapse‐free survival were not significantly impacted by FLT3‐ITD status. Furthermore, relapse and overall survival were comparable between FLT3‐ITD patients transplanted from various donor pools, namely matched siblings, unrelated donors, haplo‐SCT). Finally, subset analysis of patients with intermediate risk cytogenetics confirmed the absence of a prognostic impact of FLT3‐ITD also for this patient segment. In AML patients undergoing T‐cell replete haplo‐SCT, the FLT3‐ITD mutation possibly does not retain its prognostic significance.     

FLT3-ITD cooperates with inv(16) to promote progression to acute myeloid leukemia

The inversion of chromosome 16 in the inv(16)(p13q22) is one of the most frequent cytogenetic abnormalities observed in acute myeloid leukemia (AML). The inv(16) fuses the core binding factor (CBF) beta subunit with the coiled-coil rod domain of smooth muscle myosin heavy chain (SMMHC). Expression of CBFbeta-SMMHC in mice does not promote AML in the absence of secondary mutations. Patient samples with the inv(16) also possess mutually exclusive activating mutations in either N-RAS, K-RAS, or the receptor tyrosine kinases, c-KIT and FLT3, in almost 70% of cases. To test whether an activating mutation of FLT3 (FLT3-ITD) would cooperate with CBFbeta-SMMHC to promote AML, we coexpressed both mutations in hematopoietic progenitor cells used to reconstitute lethally irradiated mice. Analysis of transplanted animals showed strong selection for CBFbeta-SMMHC/FLT3-ITD-expressing cells in bone marrow and peripheral blood. Compared with animals transplanted with only CBFbeta-SMMHC-expressing cells, FLT3-ITD further restricted early myeloid differentiation and promoted peripheralization of primitive myeloblasts as early as 2.5 weeks after transplantation. FLT3-ITD also accelerated disease progression in all CBFbeta-SMMHC/FLT3-ITD-reconstituted animals, which died of a highly aggressive and transplantable AML within 3 to 5 months. These results indicate that FLT3-activating mutations can cooperate with CBFbeta-SMMHC in an animal model of inv(16)-associated AML.