Gene Summary

Gene:FLT3; fms-related tyrosine kinase 3
Aliases: FLK2, STK1, CD135, FLK-2
Summary:This gene encodes a class III receptor tyrosine kinase that regulates hematopoiesis. This receptor is activated by binding of the fms-related tyrosine kinase 3 ligand to the extracellular domain, which induces homodimer formation in the plasma membrane leading to autophosphorylation of the receptor. The activated receptor kinase subsequently phosphorylates and activates multiple cytoplasmic effector molecules in pathways involved in apoptosis, proliferation, and differentiation of hematopoietic cells in bone marrow. Mutations that result in the constitutive activation of this receptor result in acute myeloid leukemia and acute lymphoblastic leukemia. [provided by RefSeq, Jan 2015]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:receptor-type tyrosine-protein kinase FLT3
Source:NCBIAccessed: 26 August, 2015


What does this gene/protein do?
Show (36)
Pathways:What pathways are this gene/protein implicaed in?
Show (3)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 26 August 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Transcriptome
  • Risk Factors
  • Neoplasm Proteins
  • Recurrence
  • Tandem Repeat Sequences
  • Phenylurea Compounds
  • Bone Marrow
  • Protein Kinase Inhibitors
  • Chromosome 13
  • Drug Resistance
  • Phosphorylation
  • Adolescents
  • Proto-Oncogene Proteins c-kit
  • Gene Duplication
  • Acute Myeloid Leukaemia
  • Childhood Cancer
  • Niacinamide
  • Leukaemia
  • Neoplastic Cell Transformation
  • Hematopoietic Stem Cell Transplantation
  • Residual Disease
  • Cancer Gene Expression Regulation
  • Isocitrate Dehydrogenase
  • Cell Proliferation
  • FLT3
  • Gene Expression Profiling
  • Nuclear Proteins
  • Remission Induction
  • Signal Transduction
  • Survival Rate
  • Leukemic Gene Expression Regulation
  • Mutation
  • Disease-Free Survival
  • Karyotyping
  • Apoptosis
  • Antineoplastic Agents
  • Oncogene Fusion Proteins
  • Gene Expression
  • Chromosome Aberrations
  • DNA Mutational Analysis
  • CCAAT-Enhancer-Binding Proteins
  • Infant
Tag cloud generated 26 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (3)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: FLT3 (cancer-related)

Lin P, Falini B
Acute Myeloid Leukemia With Recurrent Genetic Abnormalities Other Than Translocations.
Am J Clin Pathol. 2015; 144(1):19-28 [PubMed] Related Publications
OBJECTIVES: Session 2 of the workshop focused on cases of acute myeloid leukemia (AML) with gene mutations in the setting of a normal karyotype.
METHODS: Among 22 AML cases submitted, 14 had the NPM1 mutation, most also accompanied by mutations of other genes such as FLT3-ITD, DNMT3A, or, rarely, TP53; three cases had the heterozygous CEBPA mutation; and two cases had MYC amplification.
RESULTS: We explored prognostic implications of gene mutations such as DNMT3A, issues related to the classification of AML cases with the NPM1 mutation, and myelodysplasia-related changes arising from chronic myelomonocytic leukemia after a short latency interval. Disparate patterns of treatment response to targeted therapy using an FLT3 inhibitor, designated as cytotoxic or differentiation, and their genetic underpinnings were described. Finally, a minimal screening panel for gene mutations and the optimal approach for monitoring minimal residual disease were discussed.
CONCLUSIONS: In aggregate, this session highlighted the need for a refined molecular classification of AML as well as improved risk stratification based on systematic assessment for genetic alterations and their evolution over time.

Ogawara Y, Katsumoto T, Aikawa Y, et al.
IDH2 and NPM1 Mutations Cooperate to Activate Hoxa9/Meis1 and Hypoxia Pathways in Acute Myeloid Leukemia.
Cancer Res. 2015; 75(10):2005-16 [PubMed] Related Publications
IDH1 and IDH2 mutations occur frequently in acute myeloid leukemia (AML) and other cancers. The mutant isocitrate dehydrogenase (IDH) enzymes convert α-ketoglutarate (α-KG) to the oncometabolite 2-hydroxyglutarate (2-HG), which dysregulates a set of α-KG-dependent dioxygenases. To determine whether mutant IDH enzymes are valid targets for cancer therapy, we created a mouse model of AML in which mice were transplanted with nucleophosmin1 (NPM)(+/-) hematopoietic stem/progenitor cells cotransduced with four mutant genes (NPMc, IDH2/R140Q, DNMT3A/R882H, and FLT3/ITD), which often occur simultaneously in human AML patients. Conditional deletion of IDH2/R140Q blocked 2-HG production and maintenance of leukemia stem cells, resulting in survival of the AML mice. IDH2/R140Q was necessary for the engraftment or survival of NPMc(+) cells in vivo. Gene expression analysis indicated that NPMc increased expression of Hoxa9. IDH2/R140Q also increased the level of Meis1 and activated the hypoxia pathway in AML cells. IDH2/R140Q decreased the 5hmC modification and expression of some differentiation-inducing genes (Ebf1 and Spib). Taken together, our results indicated that IDH2 mutation is critical for the development and maintenance of AML stem-like cells, and they provided a preclinical justification for targeting mutant IDH enzymes as a strategy for anticancer therapy.

Verbiest T, Bouffler S, Nutt SL, Badie C
PU.1 downregulation in murine radiation-induced acute myeloid leukaemia (AML): from molecular mechanism to human AML.
Carcinogenesis. 2015; 36(4):413-9 [PubMed] Free Access to Full Article Related Publications
The transcription factor PU.1, encoded by the murine Sfpi1 gene (SPI1 in humans), is a member of the Ets transcription factor family and plays a vital role in commitment and maturation of the myeloid and lymphoid lineages. Murine studies directly link primary acute myeloid leukaemia (AML) and decreased PU.1 expression in specifically modified strains. Similarly, a radiation-induced chromosome 2 deletion and subsequent Sfpi1 point mutation in the remaining allele lead to murine radiation-induced AML. Consistent with murine data, heterozygous deletion of the SPI1 locus and mutation of the -14kb SPI1 upstream regulatory element were described previously in human primary AML, although they are rare events. Other mechanisms linked to PU.1 downregulation in human AML include TP53 deletion, FLT3-ITD mutation and the recurrent AML1-ETO [t(8;21)] and PML-RARA [t(15;17)] translocations. This review provides an up-to-date overview on our current understanding of the involvement of PU.1 in the initiation and development of radiation-induced AML, together with recommendations for future murine and human studies.

Oellerich T, Mohr S, Corso J, et al.
FLT3-ITD and TLR9 use Bruton tyrosine kinase to activate distinct transcriptional programs mediating AML cell survival and proliferation.
Blood. 2015; 125(12):1936-47 [PubMed] Related Publications
Acute myeloid leukemia (AML) is driven by niche-derived and cell-autonomous stimuli. Although many cell-autonomous disease drivers are known, niche-dependent signaling in the context of the genetic disease heterogeneity has been difficult to investigate. Here, we analyzed the role of Bruton tyrosine kinase (BTK) in AML. BTK was frequently expressed, and its inhibition strongly impaired the proliferation and survival of AML cells also in the presence of bone marrow stroma. By interactome analysis, (phospho)proteomics, and transcriptome sequencing, we characterized BTK signaling networks. We show that BTK-dependent signaling is highly context dependent. In Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD)-positive AML, BTK mediates FLT3-ITD-dependent Myc and STAT5 activation, and combined targeting of FLT3-ITD and BTK showed additive effects. In Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD)-negative AML, BTK couples Toll-like receptor 9 (TLR9) activation to nuclear factor κΒ and STAT5. Both BTK-dependent transcriptional programs were relevant for cell cycle progression and apoptosis regulation. Thus, we identify context-dependent oncogenic driver events that may guide subtype-specific treatment strategies and, for the first time, point to a role of TLR9 in AML. Clinical evaluation of BTK inhibitors in AML seems warranted.

Ok CY, Patel KP, Garcia-Manero G, et al.
Mutational profiling of therapy-related myelodysplastic syndromes and acute myeloid leukemia by next generation sequencing, a comparison with de novo diseases.
Leuk Res. 2015; 39(3):348-54 [PubMed] Related Publications
In this study we used a next generation sequencing-based approach to profile gene mutations in therapy-related myelodysplastic syndromes (t-MDS) and acute myeloid leukemia (t-AML); and compared these findings with de novo MDS/AML. Consecutive bone marrow samples of 498 patients, including 70 therapy-related (28 MDS and 42 AML) and 428 de novo (147 MDS and 281 AML) were analyzed using a modified-TruSeq Amplicon Cancer Panel (Illumina) covering mutation hotspots of 53 genes. Overall, mutation(s) were detected in 58.6% of t-MDS/AML and 56.8% of de novo MDS/AML. Of therapy-related cases, mutations were detected in 71.4% of t-AML versus 39.3% t-MDS (p=0.0127). TP53 was the most common mutated gene in t-MDS (35.7%) as well as t-AML (33.3%), significantly higher than de novo MDS (17.7%) (p=0.0410) and de novo AML (12.8%) (p=0.0020). t-AML showed more frequent PTPN11 but less NPM1 and FLT3 mutations than de novo AML. In summary, t-MDS/AML shows a mutation profile different from their de novo counterparts. TP53 mutations are highly and similarly prevalent in t-MDS and t-AML but mutations in genes other than TP53 were more frequent in t-AML than t-MDS. The molecular genetic profiling further expands our understanding in this group of clinically aggressive yet heterogeneous myeloid neoplasms.

Röllig C, Bornhäuser M, Kramer M, et al.
Allogeneic stem-cell transplantation in patients with NPM1-mutated acute myeloid leukemia: results from a prospective donor versus no-donor analysis of patients after upfront HLA typing within the SAL-AML 2003 trial.
J Clin Oncol. 2015; 33(5):403-10 [PubMed] Related Publications
PURPOSE: The presence of a mutated nucleophosmin-1 gene (NPM1(mut)) in acute myeloid leukemia (AML) is associated with a favorable prognosis. To assess the predictive value with regard to allogeneic stem-cell transplantation (SCT), we compared the clinical course of patients with NPM1(mut) AML eligible for allogeneic SCT in a donor versus no-donor analysis.
PATIENTS AND METHODS: Of 1,179 patients with AML (age 18 to 60 years) treated in the Study Alliance Leukemia AML 2003 trial, we identified all NPM1(mut) patients with an intermediate-risk karyotype. According to the trial protocol, patients were intended to receive an allogeneic SCT if an HLA-identical sibling donor was available. Patients with no available donor received consolidation or autologous SCT. We compared relapse-free survival (RFS) and overall survival (OS) depending on the availability of a suitable donor.
RESULTS: Of 304 eligible patients, 77 patients had a sibling donor and 227 had no available matched family donor. The 3-year RFS rates in the donor and no-donor groups were 71% and 47%, respectively (P = .005); OS rates were 70% and 60%, respectively (P = .114). In patients with normal karyotype and no FLT3 internal tandem duplication (n = 148), the 3-year RFS rates in the donor and no-donor groups were 83% and 53%, respectively (P = .004); and the 3-year OS rates were 81% and 75%, respectively (P = .300).
CONCLUSION: Allogeneic SCT led to a significantly prolonged RFS in patients with NPM1(mut) AML. The absence of a statistically significant difference in OS is most likely a result of the fact that NPM1(mut) patients who experienced relapse responded well to salvage treatment. Allogeneic SCT in first remission has potent antileukemic efficacy and is a valuable treatment option in patients with NPM1(mut) AML with a sibling donor.

Wen YS, Cai L, Zhang XW, et al.
Concurrent oncogene mutation profile in Chinese patients with stage Ib lung adenocarcinoma.
Medicine (Baltimore). 2014; 93(29):e296 [PubMed] Related Publications
Molecular characteristics in lung cancer are associated with carcinogenesis, response to targeted therapies, and prognosis. With concurrent oncogene mutations being reported more often, the adjustment of treatment based on the driver gene mutations would improve therapy. We proposed to investigate the distribution of concurrent oncogene mutations in stage Ib lung adenocarcinoma in a Chinese population and find out the correlation between survival outcome and the most frequently mutated genes in EGFR and KRAS in Chinese population. Simultaneously, we tried to validate the Sequenom method by real time fluoresce qualification reverse transcription polymerase chain reaction (RT-PCR) in oncogene detection. One hundred fifty-six patients who underwent complete surgical resection in our hospital between 1999 and 2007 were retrospectively investigated. Using time-of-flight mass spectrometry, 238 mutation hotspots in 19 oncogenes were examined. Genetic mutations occurred in 86 of 156 patients (55.13%). EGFR was most frequently gene contained driver mutations, with a rate of 44.23%, followed by KRAS (8.33%), PIK3CA (3.84%), KIT (3.20%), BRAF (2.56%), AKT (1.28%), MET (0.64%), NRAS (0.64%), HRAS (0.64%), and ERBB2 (0.64%). No mutations were found in the RET, PDGFRA, FGFR1, FGFR3, FLT3, ABL, CDK, or JAK2 oncogenes. Thirteen patients (8.3%) were detected in multiple gene mutations. Six patients had PIK3CA mutations in addition to mutations in EGFR and KRAS. EGFR mutations can coexist with mutations in NRAS, KIT, ERBB2, and BRAF. Only one case was found to have a KRAS mutation coexisting with the EGFR T790M mutation. Otherwise, mutations in EGFR and KRAS seem to be mutually exclusive. There is no survival benefit in favor of EGFR/KRAS mutation. Several concomitant driver gene mutations were observed in our study. None of EFGR/KRAS mutation was demonstrated as a prognostic factor. Polygenic mutation testing by time-of-flight mass spectrometry was validated by RT-PCR, which can be an alternative option to test for multiple mutations and can be widely applied to clinical practice and help to guide treatment.

Skvarova Kramarzova K, Fiser K, Mejstrikova E, et al.
Homeobox gene expression in acute myeloid leukemia is linked to typical underlying molecular aberrations.
J Hematol Oncol. 2014; 7:94 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Although distinct patterns of homeobox (HOX) gene expression have been described in defined cytogenetic and molecular subsets of patients with acute myeloid leukemia (AML), it is unknown whether these patterns are the direct result of transcriptional alterations or rather represent the differentiation stage of the leukemic cell.
METHOD: To address this question, we used qPCR to analyze mRNA expression of HOXA and HOXB genes in bone marrow (BM) samples of 46 patients with AML and sorted subpopulations of healthy BM cells. These various stages of myeloid differentiation represent matched counterparts of morphological subgroups of AML. To further study the transcriptional alterations of HOX genes in hematopoiesis, we also analyzed gene expression of epigenetic modifiers in the subpopluations of healthy BM and leukemic cells.
RESULTS: Unsupervised hierarchical clustering divided the AMLs into five clusters characterized by the presence of prevalent molecular genetic aberrations. Notably, the impact of genotype on HOX gene expression was significantly more pronounced than that of the differentiation stage of the blasts. This driving role of molecular aberrations was best exemplified by the repressive effect of the PML-RARa fusion gene on HOX gene expression, regardless of the presence of the FLT3/ITD mutation. Furthermore, HOX gene expression was positively correlated with mRNA levels of histone demethylases (JMJD3 and UTX) and negatively correlated with gene expression of DNA methyltranferases. No such relationships were observed in subpopulations of healthy BM cells.
CONCLUSION: Our results demonstrate that specific molecular genetic aberrations, rather than differentiation per se, underlie the observed differences in HOX gene expression in AML. Moreover, the observed correlations between epigenetic modifiers and HOX expression that are specific to malignant hematopoiesis, suggest their potential causal relationships.

Souza Melo CP, Campos CB, Dutra ÁP, et al.
Correlation between FLT3-ITD status and clinical, cellular and molecular profiles in promyelocytic acute leukemias.
Leuk Res. 2015; 39(2):131-7 [PubMed] Related Publications
Internal tandem duplications (ITD) of FLT3 gene occur in about a third of acute promyelocytic leukemias (APL). We investigated the patterns of blood count, surface antigen, expression, chromosome aberrations, PML-RARa isoform, gene expression profile (GEP) and survival in 34 APL patients according to FLT3-ITD status. 97% had a t(15;17) and all of them carried PML-RARa gene fusion, 8 (23.5%) had a FLT3-ITD mutation. Presence of ITD was associated with higher Hb and WBC levels, bcr3 isoform, CD34 expression, CD2 or CD2/CD34 expression. In a multivariate analysis, Hb>9.6g/dL and WBC≥20 × 10(9)/L were important factors for predicting ITD presence. GEP showed that FLT3-ITD carriers clustered separately, even when as few as 5 genes were considered. This study provides further evidence that FLT3-ITDs carriers constitute a biologically distinct group of APL patients.

Garzon R, Volinia S, Papaioannou D, et al.
Expression and prognostic impact of lncRNAs in acute myeloid leukemia.
Proc Natl Acad Sci U S A. 2014; 111(52):18679-84 [PubMed] Free Access to Full Article Related Publications
Long noncoding RNAs (lncRNAs) are transcripts longer than 200 nucleotides, located within the intergenic stretches or overlapping antisense transcripts of protein coding genes. LncRNAs are involved in numerous biological roles including imprinting, epigenetic regulation, apoptosis, and cell cycle. To determine whether lncRNAs are associated with clinical features and recurrent mutations in older patients (aged ≥60 y) with cytogenetically normal (CN) acute myeloid leukemia (AML), we evaluated lncRNA expression in 148 untreated older CN-AML cases using a custom microarray platform. An independent set of 71 untreated older patients with CN-AML was used to validate the outcome scores using RNA sequencing. Distinctive lncRNA profiles were found associated with selected mutations, such as internal tandem duplications in the FLT3 gene (FLT3-ITD) and mutations in the NPM1, CEBPA, IDH2, ASXL1, and RUNX1 genes. Using the lncRNAs most associated with event-free survival in a training cohort of 148 older patients with CN-AML, we derived a lncRNA score composed of 48 lncRNAs. Patients with an unfavorable compared with favorable lncRNA score had a lower complete response (CR) rate [P < 0.001, odds ratio = 0.14, 54% vs. 89%], shorter disease-free survival (DFS) [P < 0.001, hazard ratio (HR) = 2.88] and overall survival (OS) (P < 0.001, HR = 2.95). The validation set analyses confirmed these results (CR, P = 0.03; DFS, P = 0.009; OS, P = 0.009). Multivariable analyses for CR, DFS, and OS identified the lncRNA score as an independent marker for outcome. In conclusion, lncRNA expression in AML is closely associated with recurrent mutations. A small subset of lncRNAs is correlated strongly with treatment response and survival.

Fiskus W, Sharma S, Saha S, et al.
Pre-clinical efficacy of combined therapy with novel β-catenin antagonist BC2059 and histone deacetylase inhibitor against AML cells.
Leukemia. 2015; 29(6):1267-78 [PubMed] Article available free on PMC after 01/12/2015 Related Publications
The canonical wingless-type MMTV integration site (WNT)-β-catenin pathway is essential for self-renewal, growth and survival of acute myeloid leukemia (AML) stem/blast progenitor cells (BPCs). Deregulated WNT signaling inhibits degradation of β-catenin, causing increased nuclear translocation and co-factor activity of β-catenin with the transcriptional regulator T-cell factor (TCF) 4/lymphoid enhancer factor 1 in AML BPCs. Here, we determined the pre-clinical anti-AML activity of the anthraquinone oxime-analog BC2059 (BC), known to attenuate β-catenin levels. BC treatment disrupted the binding of β-catenin with the scaffold protein transducin β-like 1 and proteasomal degradation and decline in the nuclear levels of β-catenin. This was associated with reduced transcriptional activity of TCF4 and expression of its target genes, cyclin D1, c-MYC and survivin. BC treatment dose-dependently induced apoptosis of cultured and primary AML BPCs. Treatment with BC also significantly improved the median survival of immune-depleted mice engrafted with either cultured or primary AML BPCs, exhibiting nuclear expression of β-catenin. Co-treatment with the pan-histone deacetylase inhibitor panobinostat and BC synergistically induced apoptosis of cultured and primary AML BPCs, including those expressing FLT3-ITD, as well as further significantly improved the survival of immune-depleted mice engrafted with primary AML BPCs. These findings underscore the promising pre-clinical activity and warrant further testing of BC against human AML, especially those expressing FLT3-ITD.

Behdad A, Weigelin HC, Elenitoba-Johnson KS, Betz BL
A clinical grade sequencing-based assay for CEBPA mutation testing: report of a large series of myeloid neoplasms.
J Mol Diagn. 2015; 17(1):76-84 [PubMed] Related Publications
Diagnostic testing for CEBPA mutations is the standard of care for cytogenetically normal acute myeloid leukemia. Widespread implementation of this testing is hampered by technical challenges associated with the GC content of the gene, the variability of the mutations, and the complexity of the sequence analysis and variant interpretation. We developed a robust Sanger-sequencing test to detect CEBPA mutations in diagnostic acute myeloid leukemia specimens. Our experience with testing 2393 cases of suspected myeloid neoplasms is presented. NPM1, FLT3-internal tandem duplication (ITD), and FLT3-D835 mutation status were determined in parallel; 160 (6.7%) cases harbored CEBPA mutations, including 86 with a single mutation and 74 with double mutations. Nineteen single-mutant cases and 3 double-mutant cases showed only nucleotide substitutions that could not be detected by fragment-analysis-based tests. A subset of cases harbored double mutations with uneven mutant allele frequency and required careful interpretation because of possible leukemic heterogeneity. NPM1 and FLT3-ITD mutations were more frequent in single- compared with double-mutation cases (31% versus 5% for NPM1, and 28% versus 16% for FLT3-ITD). This sequencing-based assay provides an efficient and reliable CEBPA mutation testing platform, permitting detection of all mutations with immediate distinction of single- and double-mutation cases. Given the technical challenges, robust Sanger-sequencing assays continue to maintain an important role in clinical CEBPA testing despite the development of multigene next-generation sequencing assays.

Chatterjee A, Ghosh J, Ramdas B, et al.
Regulation of Stat5 by FAK and PAK1 in Oncogenic FLT3- and KIT-Driven Leukemogenesis.
Cell Rep. 2014; 9(4):1333-48 [PubMed] Article available free on PMC after 01/12/2015 Related Publications
Oncogenic mutations of FLT3 and KIT receptors are associated with poor survival in patients with acute myeloid leukemia (AML) and myeloproliferative neoplasms (MPNs), and currently available drugs are largely ineffective. Although Stat5 has been implicated in regulating several myeloid and lymphoid malignancies, how precisely Stat5 regulates leukemogenesis, including its nuclear translocation to induce gene transcription, is poorly understood. In leukemic cells, we show constitutive activation of focal adhesion kinase (FAK) whose inhibition represses leukemogenesis. Downstream of FAK, activation of Rac1 is regulated by RacGEF Tiam1, whose inhibition prolongs the survival of leukemic mice. Inhibition of the Rac1 effector PAK1 prolongs the survival of leukemic mice in part by inhibiting the nuclear translocation of Stat5. These results reveal a leukemic pathway involving FAK/Tiam1/Rac1/PAK1 and demonstrate an essential role for these signaling molecules in regulating the nuclear translocation of Stat5 in leukemogenesis.

Schetelig J, Schaich M, Schäfer-Eckart K, et al.
Hematopoietic cell transplantation in patients with intermediate and high-risk AML: results from the randomized Study Alliance Leukemia (SAL) AML 2003 trial.
Leukemia. 2015; 29(5):1060-8 [PubMed] Related Publications
The optimal timing of allogeneic hematopoietic stem cell transplantation (HCT) in acute myeloid leukemia (AML) is controversial. We report on 1179 patients with a median age of 48 years who were randomized upfront. In the control arm, sibling HCT was scheduled in the first complete remission for intermediate-risk or high-risk AML and matched unrelated HCT in complex karyotype AML. In the experimental arm, matched unrelated HCT in first remission was offered also to patients with an FLT3-ITD (FMS-like tyrosine kinase 3-internal tandem duplication) allelic ratio >0.8, poor day +15 marrow blast clearance and adverse karyotypes. Further, allogeneic HCT was recommended in high-risk AML to be performed in aplasia after induction chemotherapy. In the intent-to-treat (ITT) analysis, superiority of the experimental transplant strategy could not be shown with respect to overall survival (OS) or event-free survival. As-treated analyses suggest a profound effect of allogeneic HCT on OS (HR 0.73; P=0.002) and event-free survival (HR 0.67; P<0.001). In high-risk patients, OS was significantly improved after allogeneic HCT in aplasia (HR 0.64; P=0.046) and after HCT in remission (HR 0.74; P=0.03). Although superiority of one study arm could not be demonstrated in the ITT analysis, secondary analyses suggest that early allogeneic HCT is a promising strategy for patients with high-risk AML.

Wen XM, Lin J, Yang J, et al.
Double CEBPA mutations are prognostically favorable in non-M3 acute myeloid leukemia patients with wild-type NPM1 and FLT3-ITD.
Int J Clin Exp Pathol. 2014; 7(10):6832-40 [PubMed] Article available free on PMC after 01/12/2015 Related Publications
This study is aimed to investigate the pattern of CEBPA mutations and its clinical significance in Chinese non-M3 acute myeloid leukemia (AML) patients. The entire coding region of CEBPA gene was amplified by PCR and then sequenced in samples from 233 non-M3 AML patients. Fifty mutations were identified in 37 (15.8%) patients with eleven (4.7%) double mutated CEBPA (dmCEBPA) and twenty-six (11.1%) single mutated CEBPA (smCEBPA). dmCEBPA was exclusively observed in M1 and M2 subtypes of FAB classification (P = 0.008), whereas smCEBPA occurred in almost all subtypes (P = 0.401). Patients with dmCEBPA had significantly younger age and higher WBC counts than those with wtCEBPA (P = 0.016 and 0.043, respectively). Both dmCEBPA and smCEBPA were mainly present in cytogenetically normal patients. Patients with dmCEBPA achieved higher rate of complete (CR) than wtCEBPA patients (88% vs. 51%, P = 0.037), whereas smCEBPA and wtCEBPA groups are similar (47% vs. 51%, P = 0.810). Patients with dmCEBPA had a superior overall survival (OS) compared with patients with wtCEBPA (P = 0.033), whereas patients with smCEBPA had a similar OS as patients with wtCEBPA (P = 0.976). dmCEBPA but not smCEBPA was also associated with favorable outcome in patients with wild-type NPM1 and FLT3-ITD (NPM1(wt)FLT3-ITD(wt) ). Our data confirm that dmCEBPA but not smCEBPA is prognostically favorable in NPM1(wt)FLT3-ITD(wt) AML, and suggest that the entity AML with mutated CEBPA should be definitely designated as AML with dmCEBPA in WHO classification and smCEBPA should be excluded from the favorable risk of molecular abnormalities.

Pløen GG, Nederby L, Guldberg P, et al.
Persistence of DNMT3A mutations at long-term remission in adult patients with AML.
Br J Haematol. 2014; 167(4):478-86 [PubMed] Related Publications
Mutations in DNMT3A, the gene encoding DNA methyltransferase 3 alpha, have been identified as molecular drivers in acute myeloid leukaemia (AML) with possible implications for minimal residual disease monitoring and prognosis. To further explore the utility of DNMT3A mutations as biomarkers for AML, we developed assays for sensitive detection of recurrent mutations affecting residue R882. Analysis of DNA from 298 diagnostic AML samples revealed DNMT3A mutations in 45 cases (15%), which coincided with mutations in NPM1, FLT3 and IDH1. DNMT3A mutations were stable in 12 of 13 patients presenting with relapse or secondary myelodysplastic syndrome, but were also present in remission samples from 14 patients (at allele frequencies of <1-50%) up to 8 years after initial AML diagnosis, despite the loss of all other molecular AML markers. The mutant DNMT3A allele burden was not related to the clinical course of disease. Cell sorting demonstrated the presence of DNMT3A mutations in leukaemic blasts, but also at lower allele frequencies in T and B-cells from the same patients. Our data are consistent with the recent finding of preleukaemic stem cells in AML, which are resistant to chemotherapy. The persistence of DNMT3A mutations during remission may have important implications for the management of AML.

Sandhöfer N, Metzeler KH, Rothenberg M, et al.
Dual PI3K/mTOR inhibition shows antileukemic activity in MLL-rearranged acute myeloid leukemia.
Leukemia. 2015; 29(4):828-38 [PubMed] Related Publications
In acute myeloid leukemia (AML), several signaling pathways such as the phosphatidylinositol-3-kinase/AKT and the mammalian target of rapamycin (PI3K/AKT/mTOR) pathway are deregulated and constitutively activated as a consequence of genetic and cytogenetic abnormalities. We tested the effectiveness of PI3K/AKT/mTOR-targeting therapies and tried to identify alterations that associate with treatment sensitivity. By analyzing primary samples and cell lines, we observed a wide range of cytotoxic activity for inhibition of AKT (MK-2206), mTORC1 (rapamycin) and PI3K/mTORC1/2 (BEZ-235) with a high sensitivity of cells carrying an MLL rearrangement. In vivo PI3K/mTOR inhibition delayed tumor progression, reduced tumor load and prolonged survival in an MLL-AF9(+)/FLT3-ITD(+) xenograft mouse model. By performing targeted amplicon sequencing in 38 MLL-AF9(+) and 125 cytogenetically normal AML patient samples, we found a high additional mutation rate for genes involved in growth factor signaling in 79% of all MLL-AF9(+) samples, which could lead to a possible benefit of this cohort. PI3K/mTOR inhibition for 24 h led to the cross-activation of the ERK pathway. Further in vitro studies combining PI3K/mTOR and ERK pathway inhibition revealed highly synergistic effects in apoptosis assays. Our data implicate a possible therapeutic benefit of PI3K/mTOR inhibition in the MLL-mutated subgroup. Inhibiting rescue pathways could improve the therapeutic efficacy of PI3K-targeted therapies in AML.

Zhou L, Zhang Y, Chen S, et al.
A regimen combining the Wee1 inhibitor AZD1775 with HDAC inhibitors targets human acute myeloid leukemia cells harboring various genetic mutations.
Leukemia. 2015; 29(4):807-18 [PubMed] Article available free on PMC after 01/10/2015 Related Publications
AZD1775 targets the cell cycle checkpoint kinase Wee1 and potentiates genotoxic agent cytotoxicity through p53-dependent or -independent mechanisms. Here, we report that AZD1775 interacted synergistically with histone deacetylase inhibitors (HDACIs, for example, Vorinostat), which interrupt the DNA damage response, to kill p53-wild type (wt) or -deficient as well as FLT3-ITD leukemia cells in association with pronounced Wee1 inhibition and diminished cdc2/Cdk1 Y15 phosphorylation. Similarly, Wee1 shRNA knockdown significantly sensitized cells to HDACIs. Although AZD1775 induced Chk1 activation, reflected by markedly increased Chk1 S296/S317/S345 phosphorylation leading to inhibitory T14 phosphorylation of cdc2/Cdk1, these compensatory responses were sharply abrogated by HDACIs. This was accompanied by premature mitotic entry, multiple mitotic abnormalities and accumulation of early S-phase cells displaying increased newly replicated DNA, culminating in robust DNA damage and apoptosis. The regimen was active against patient-derived acute myelogenous leukemia (AML) cells harboring either wt or mutant p53 and various next-generation sequencing-defined mutations. Primitive CD34(+)/CD123(+)/CD38(-) populations enriched for leukemia-initiating progenitors, but not normal CD34(+) hematopoietic cells, were highly susceptible to this regimen. Finally, combining AZD1775 with Vorinostat in AML murine xenografts significantly reduced tumor burden and prolonged animal survival. A strategy combining Wee1 with HDACI inhibition warrants further investigation in AML with poor prognostic genetic aberrations.

Li L, Osdal T, Ho Y, et al.
SIRT1 activation by a c-MYC oncogenic network promotes the maintenance and drug resistance of human FLT3-ITD acute myeloid leukemia stem cells.
Cell Stem Cell. 2014; 15(4):431-46 [PubMed] Article available free on PMC after 02/10/2015 Related Publications
The FLT3-ITD mutation is frequently observed in acute myeloid leukemia (AML) and is associated with poor prognosis. In such patients, FLT3 tyrosine kinase inhibitors (TKIs) are only partially effective and do not eliminate the leukemia stem cells (LSCs) that are assumed to be the source of treatment failure. Here, we show that the NAD-dependent SIRT1 deacetylase is selectively overexpressed in primary human FLT3-ITD AML LSCs. This SIRT1 overexpression is related to enhanced expression of the USP22 deubiquitinase induced by c-MYC, leading to reduced SIRT1 ubiquitination and enhanced stability. Inhibition of SIRT1 expression or activity reduced the growth of FLT3-ITD AML LSCs and significantly enhanced TKI-mediated killing of the cells. Therefore, these results identify a c-MYC-related network that enhances SIRT1 protein expression in human FLT3-ITD AML LSCs and contributes to their maintenance. Inhibition of this oncogenic network could be an attractive approach for targeting FLT3-ITD AML LSCs to improve treatment outcomes.

Zeisig BB, So CW
A knockout Combo: eradicating AML Stem Cells with TKI plus SIRT1 inhibition.
Cell Stem Cell. 2014; 15(4):395-7 [PubMed] Related Publications
SIRT1 inhibition facilitates elimination of CML stem cells by Imatinib, in part via p53 activation. In this issue of Cell Stem Cell, Li et al. (2014) demonstrate a similar role for SIRT1 inhibition in eradicating FLT3-ITD AML stem cells, potentially through a positive feedback loop with c-MYC, highlighting SIRT1 as a potential target in combination cancer therapy.

Schlenk RF, Kayser S, Bullinger L, et al.
Differential impact of allelic ratio and insertion site in FLT3-ITD-positive AML with respect to allogeneic transplantation.
Blood. 2014; 124(23):3441-9 [PubMed] Related Publications
The objective was to evaluate the prognostic and predictive impact of allelic ratio and insertion site (IS) of internal tandem duplications (ITDs), as well as concurrent gene mutations, with regard to postremission therapy in 323 patients with FLT3-ITD-positive acute myeloid leukemia (AML). Increasing FLT3-ITD allelic ratio (P = .004) and IS in the tyrosine kinase domain 1 (TKD1, P = .06) were associated with low complete remission (CR) rates. After postremission therapy including intensive chemotherapy (n = 121) or autologous hematopoietic stem cell transplantation (HSCT, n = 17), an allelic ratio ≥ 0.51 was associated with an unfavorable relapse-free (RFS, P = .0008) and overall survival (OS, P = .004); after allogeneic HSCT (n = 93), outcome was significantly improved in patients with a high allelic ratio (RFS, P = .02; OS, P = .03), whereas no benefit was seen in patients with a low allelic ratio (RFS, P = .38; OS, P = .64). Multivariable analyses revealed a high allelic ratio as a predictive factor for the beneficial effect of allogeneic HSCT; ITD IS in TKD1 remained an unfavorable factor, whereas no prognostic impact of concurrent gene mutations was observed. The clinical trials described herein were previously published or are registered as follows: AMLHD93 and AMLHD98A, previously published; AML SG 07-04, ClinicalTrials.gov identifier #NCT00151242.

Chou SC, Tang JL, Hou HA, et al.
Prognostic implication of gene mutations on overall survival in the adult acute myeloid leukemia patients receiving or not receiving allogeneic hematopoietic stem cell transplantations.
Leuk Res. 2014; 38(11):1278-84 [PubMed] Related Publications
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.

Bleeker FE, Lamba S, Zanon C, et al.
Mutational profiling of kinases in glioblastoma.
BMC Cancer. 2014; 14:718 [PubMed] Article available free on PMC after 02/10/2015 Related Publications
BACKGROUND: Glioblastoma is a highly malignant brain tumor for which no cure is available. To identify new therapeutic targets, we performed a mutation analysis of kinase genes in glioblastoma.
METHODS: Database mining and a literature search identified 76 kinases that have been found to be mutated at least twice in multiple cancer types before. Among those we selected 34 kinase genes for mutation analysis. We also included IDH1, IDH2, PTEN, TP53 and NRAS, genes that are known to be mutated at considerable frequencies in glioblastoma. In total, 174 exons of 39 genes in 113 glioblastoma samples from 109 patients and 16 high-grade glioma (HGG) cell lines were sequenced.
RESULTS: Our mutation analysis led to the identification of 148 non-synonymous somatic mutations, of which 25 have not been reported before in glioblastoma. Somatic mutations were found in TP53, PTEN, IDH1, PIK3CA, EGFR, BRAF, EPHA3, NRAS, TGFBR2, FLT3 and RPS6KC1. Mapping the mutated genes into known signaling pathways revealed that the large majority of them plays a central role in the PI3K-AKT pathway.
CONCLUSIONS: The knowledge that at least 50% of glioblastoma tumors display mutational activation of the PI3K-AKT pathway should offer new opportunities for the rational development of therapeutic approaches for glioblastomas. However, due to the development of resistance mechanisms, kinase inhibition studies targeting the PI3K-AKT pathway for relapsing glioblastoma have mostly failed thus far. Other therapies should be investigated, targeting early events in gliomagenesis that involve both kinases and non-kinases.

Irving J, Matheson E, Minto L, et al.
Ras pathway mutations are prevalent in relapsed childhood acute lymphoblastic leukemia and confer sensitivity to MEK inhibition.
Blood. 2014; 124(23):3420-30 [PubMed] Article available free on PMC after 02/10/2015 Related Publications
For most children who relapse with acute lymphoblastic leukemia (ALL), the prognosis is poor, and there is a need for novel therapies to improve outcome. We screened samples from children with B-lineage ALL entered into the ALL-REZ BFM 2002 clinical trial (www.clinicaltrials.gov, #NCT00114348) for somatic mutations activating the Ras pathway (KRAS, NRAS, FLT3, and PTPN11) and showed mutation to be highly prevalent (76 from 206). Clinically, they were associated with high-risk features including early relapse, central nervous system (CNS) involvement, and specifically for NRAS/KRAS mutations, chemoresistance. KRAS mutations were associated with a reduced overall survival. Mutation screening of the matched diagnostic samples found many to be wild type (WT); however, by using more sensitive allelic-specific assays, low-level mutated subpopulations were found in many cases, suggesting that they survived up-front therapy and subsequently emerged at relapse. Preclinical evaluation of the mitogen-activated protein kinase kinase 1/2 inhibitor selumetinib (AZD6244, ARRY-142886) showed significant differential sensitivity in Ras pathway-mutated ALL compared with WT cells both in vitro and in an orthotopic xenograft model engrafted with primary ALL; in the latter, reduced RAS-mutated CNS leukemia. Given these data, clinical evaluation of selumetinib may be warranted for Ras pathway-mutated relapsed ALL.

Grunwald MR, Tseng LH, Lin MT, et al.
Improved FLT3 internal tandem duplication PCR assay predicts outcome after allogeneic transplant for acute myeloid leukemia.
Biol Blood Marrow Transplant. 2014; 20(12):1989-95 [PubMed] Article available free on PMC after 01/12/2015 Related Publications
Patients with acute myeloid leukemia (AML) who harbor internal tandem duplication (ITD) mutations of the FMS-like tyrosine kinase 3 (FLT3) gene carry a poor prognosis. Although allogeneic transplantation may improve outcomes, relapse occurs frequently. The FLT3/ITD mutation has been deemed an unsuitable minimal residual disease (MRD) marker because it is unstable and because the standard assay for the mutation is relatively insensitive. The FLT3 mutation is undetectable by PCR at pre- or post-transplant time points in many FLT3/ITD AML patients who subsequently relapse after transplant. We report the application of a new technique, tandem duplication PCR (TD-PCR), for detecting MRD in FLT3/ITD AML patients. Between October 2004 and January 2012, 54 FLT3/ITD AML patients in remission underwent transplantation at our institution. Of 37 patients with available day 60 marrow samples, 28 (76%) were assessable for MRD detection. In seven of 28 patients (25%), the FLT3/ITD mutation was detectable by TD-PCR but not by standard PCR on day 60. Six of 7 patients (86%) with MRD by TD-PCR have relapsed to date compared with only 2 of 21 patients (10%) who were negative for MRD (P = .0003). The ability to detect MRD by this sensitive technique may provide an opportunity for early clinical intervention.

Onish C, Mori-Kimachi S, Hirade T, et al.
Internal tandem duplication mutations in FLT3 gene augment chemotaxis to Cxcl12 protein by blocking the down-regulation of the Rho-associated kinase via the Cxcl12/Cxcr4 signaling axis.
J Biol Chem. 2014; 289(45):31053-65 [PubMed] Article available free on PMC after 07/11/2015 Related Publications
Internal tandem duplication mutations in the Flt3 gene (ITD-FLT3) enhance cell migration toward the chemokine Cxcl12, which is highly expressed in the therapy-protective bone marrow niche, providing a potential mechanism underlying the poor prognosis of ITD-FLT3(+) acute myeloid leukemia. We aimed to investigate the mechanisms linking ITD-FLT3 to increased cell migration toward Cxcl12. Classification of the expression of Cxcl12-regulated genes in ITD-FLT3(+) cells demonstrated that the enhanced migration of ITD-FLT3(+) cells toward Cxcl12 was associated with the differential expression of genes downstream of Cxcl12/Cxcr4, which are functionally distinct from those expressed in ITD-FLT3(-) cells but are independent of the Cxcr4 expression levels. Among these differentially regulated genes, the expression of Rock1 in the ITD-FLT3(+) cells that migrated toward Cxcl12 was significantly higher than in ITD-FLT3(-) cells that migrated toward Cxcl12. In ITD-FLT3(-) cells, Rock1 expression and Mypt1 phosphorylation were transiently up-regulated but were subsequently down-regulated by Cxcl12. In contrast, the presence of ITD-FLT3 blocked the Cxcl12-induced down-regulation of Rock1 and early Mypt1 dephosphorylation. Likewise, the FLT3 ligand counteracted the Cxcl12-induced down-regulation of Rock1 in ITD-FLT3(-) cells, which coincided with enhanced cell migration toward Cxcl12. Rock1 antagonists or Rock1 shRNA abolished the enhanced migration of ITD-FLT3(+) cells toward Cxcl12. Our findings demonstrate that ITD-FLT3 increases cell migration toward Cxcl12 by antagonizing the down-regulation of Rock1 expression. These findings suggest that the aberrant modulation of Rock1 expression and activity induced by ITD-FLT3 may enhance acute myeloid leukemia cell chemotaxis to the therapy-protective bone marrow niche, where Cxcl12 is abundantly expressed.

Kato T, Sakata-Yanagimoto M, Nishikii H, et al.
Hes1 suppresses acute myeloid leukemia development through FLT3 repression.
Leukemia. 2015; 29(3):576-85 [PubMed] Related Publications
In leukemogenesis, Notch signaling can be up and downregulated in a context-dependent manner. The transcription factor hairy and enhancer of split-1 (Hes1) is well-characterized as a downstream target of Notch signaling. Hes1 encodes a basic helix-loop-helix-type protein, and represses target gene expression. Here, we report that deletion of the Hes1 gene in mice promotes acute myeloid leukemia (AML) development induced by the MLL-AF9 fusion protein. We then found that Hes1 directly bound to the promoter region of the FMS-like tyrosine kinase 3 (FLT3) gene and downregulated the promoter activity. FLT3 was consequently upregulated in MLL-AF9-expressing immortalized and leukemia cells with a Hes1- or RBPJ-null background. MLL-AF9-expressing Hes1-null AML cells showed enhanced proliferation and ERK phosphorylation following FLT3 ligand stimulation. FLT3 inhibition efficiently abrogated proliferation of MLL-AF9-induced Hes1-null AML cells. Furthermore, an agonistic anti-Notch2 antibody induced apoptosis of MLL-AF9-induced AML cells in a Hes1-wild type but not a Hes1-null background. We also accessed two independent databases containing messenger RNA (mRNA) expression profiles and found that the expression level of FLT3 mRNA was negatively correlated with those of HES1 in patient AML samples. These observations demonstrate that Hes1 mediates tumor suppressive roles of Notch signaling in AML development, probably by downregulating FLT3 expression.

Konig H, Levis M
Targeting FLT3 to treat leukemia.
Expert Opin Ther Targets. 2015; 19(1):37-54 [PubMed] Related Publications
INTRODUCTION: Approximately 23% of acute myeloid leukemia (AML) patients younger than 60 years of age carry a mutation in the transmembrane domain of the FMS-like tyrosine kinase-3 (FLT3) gene (FLT3/internal tandem duplications [ITD]). In normal karyotype AML, the presence of a FLT3/ITD mutation is associated with poor prognosis, as mirrored by a high risk of relapse even after allogeneic stem cell transplantation. The poor prognostic impact along with the observation that FLT3 is frequently overexpressed in the majority of AML cases has formed the platform for the development of FLT3-targeted strategies. To date, several FLT3 kinase inhibitors have been investigated in preclinical and clinical studies. However, as of yet, none of the studied FLT3 inhibitors has received FDA approval for routine clinical use in AML. This is in part due to the 'off target' effects observed with most inhibitors when administered at concentrations needed to achieve sustained levels of FLT3 inhibition, which are required to exhibit substantial cytotoxic effects against leukemic blasts. Furthermore, the development of resistance mutations has emerged as a clinical issue posing a threat to successful FLT3 inhibitor therapy.
AREAS COVERED: In this review, the authors provide a brief summary of FLT3 inhibitors investigated thus far, and discuss current treatment approaches and strategies how to best incorporate FLT3 tyrosine kinase inhibitors (TKIs) into therapy.
EXPERT OPINION: The combination of a FLT3 inhibitor with conventional chemotherapeutic regimens, epigenetic modifiers or inhibitors of FLT3 downstream and collateral effectors has emerged as a promising strategy to improve treatment outcome. The future of a tailored, molecular-based treatment approach for FLT3-mutated AML demands novel clinical trial concepts based on harmonized and aligned research goals between clinical and research centers and industry.

Sharawat SK, Bakhshi R, Vishnubhatla S, Bakhshi S
High receptor tyrosine kinase (FLT3, KIT) transcript versus anti-apoptotic (BCL2) transcript ratio independently predicts inferior outcome in pediatric acute myeloid leukemia.
Blood Cells Mol Dis. 2015; 54(1):56-64 [PubMed] Related Publications
OBJECTIVE: In acute myeloid leukemia (AML), simultaneous expression of proliferative (FLT3, KIT) and anti-apoptotic genes (BCL2) is unknown. The aim of the study was to prospectively evaluate proliferative and anti-apoptotic gene transcripts, their interrelationship and impact on the outcome in pediatric AML patients.
METHODS: We assessed proliferative and anti-apoptotic gene transcripts by Q-polymerase chain reaction (TaqMan probe) in 64 consecutive pediatric AML patients. Survival data was analyzed by Kaplan-Meier curves followed by log rank test to compare statistical significance between groups. Stepwise multivariable Cox regression method was used to evaluate independent prognostic factors.
RESULTS: In univariate analysis, transcript ratio of FLT3/BCL2 and FLT3+KIT/BCL2 significantly predicted event free survival (EFS) (<0.01 and <0.01 respectively) and overall survival (OS) (<0.01 and<0.01 respectively). In stepwise Cox-regression model, high white blood cell count and high FLT3+KIT/BCL2 ratio predicted EFS (HR: 2.2 and 2.3); high hemoglobin and high FLT3+KIT/BCL2 ratio predicted OS (HR: 0.45 and 3.85). Prognostic index (PI) was calculated using the hazard coefficient of independent prognostic factors; at 57.3 months, predicted OS of patients with the highest PI of 1.8 was 8% versus 73% for the lowest PI of -0.3. The mean PI of patients who died was 1.8±0.72 versus 0.54±0.70 for those who are alive, P=0.004.
CONCLUSIONS: This first study showed that individual expression of proliferative and anti-apoptotic transcripts is not as important in AML patients, rather their interrelationship and relative level probably determines the outcome.

Roberts KG, Li Y, Payne-Turner D, et al.
Targetable kinase-activating lesions in Ph-like acute lymphoblastic leukemia.
N Engl J Med. 2014; 371(11):1005-15 [PubMed] Article available free on PMC after 07/11/2015 Related Publications
BACKGROUND: Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) is characterized by a gene-expression profile similar to that of BCR-ABL1-positive ALL, alterations of lymphoid transcription factor genes, and a poor outcome. The frequency and spectrum of genetic alterations in Ph-like ALL and its responsiveness to tyrosine kinase inhibition are undefined, especially in adolescents and adults.
METHODS: We performed genomic profiling of 1725 patients with precursor B-cell ALL and detailed genomic analysis of 154 patients with Ph-like ALL. We examined the functional effects of fusion proteins and the efficacy of tyrosine kinase inhibitors in mouse pre-B cells and xenografts of human Ph-like ALL.
RESULTS: Ph-like ALL increased in frequency from 10% among children with standard-risk ALL to 27% among young adults with ALL and was associated with a poor outcome. Kinase-activating alterations were identified in 91% of patients with Ph-like ALL; rearrangements involving ABL1, ABL2, CRLF2, CSF1R, EPOR, JAK2, NTRK3, PDGFRB, PTK2B, TSLP, or TYK2 and sequence mutations involving FLT3, IL7R, or SH2B3 were most common. Expression of ABL1, ABL2, CSF1R, JAK2, and PDGFRB fusions resulted in cytokine-independent proliferation and activation of phosphorylated STAT5. Cell lines and human leukemic cells expressing ABL1, ABL2, CSF1R, and PDGFRB fusions were sensitive in vitro to dasatinib, EPOR and JAK2 rearrangements were sensitive to ruxolitinib, and the ETV6-NTRK3 fusion was sensitive to crizotinib.
CONCLUSIONS: Ph-like ALL was found to be characterized by a range of genomic alterations that activate a limited number of signaling pathways, all of which may be amenable to inhibition with approved tyrosine kinase inhibitors. Trials identifying Ph-like ALL are needed to assess whether adding tyrosine kinase inhibitors to current therapy will improve the survival of patients with this type of leukemia. (Funded by the American Lebanese Syrian Associated Charities and others.).

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Cite this page: Cotterill SJ. FLT3, Cancer Genetics Web: http://www.cancer-genetics.org/FLT3.htm Accessed:

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