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      Prognostic significance of the FLT3 ITD mutation in patients with normal-karyotype acute myeloid leukemia in relapse

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          Abstract

          Background

          Fms-like tyrosine kinase 3 internal tandem duplication ( FLT3 ITD) mutation is related to poor prognosis in normal-karyotype acute myeloid leukemia (AML). However, the prognostic significance of the mutation at relapse has not been adequately investigated. We investigated the prognostic significance of the FLT3 ITD mutation at relapse in normal-karyotype AML patients.

          Methods

          We analyzed 69 normal-karyotype AML patients, in whom paired bone marrow samples taken at initial diagnosis and subsequent relapse were analyzed for the FLT3 ITD mutation at the Asan Medical Center between 1995 and 2009.

          Results

          Forty patients showed a persistent wild-type genotype, 11 showed the FLT3 ITD mutation at diagnosis and relapse, and 9 lost and another 9 acquired the mutation at relapse. The mutation status at relapse affected the overall survival (OS), with the mutation group showing shorter OS and survival after relapse than the wild-type group did ( P<0.001 and P<0.001, respectively), despite having received more frequent stem cell transplantation after relapse than the wild-type group did. However, no difference was detected in the OS and survival after relapse with regard to the mutation status at diagnosis.

          Conclusion

          The patients with FLT3 ITD mutation at relapse showed poorer prognoses than those without the mutation. However, mutation status at diagnosis did not affect the outcome. These results suggest that, in normal-karyotype AML patients with relapse, the prognostic significance of FLT3 ITD mutation at relapse is greater than that of the mutation status at diagnosis.

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          Most cited references17

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          Analysis of FLT3-activating mutations in 979 patients with acute myelogenous leukemia: association with FAB subtypes and identification of subgroups with poor prognosis.

          C Thiede (2002)
          Constitutive activation of the FLT3 receptor tyrosine kinase, either by internal tandem duplication (ITD) of the juxtamembrane region or by point mutations in the second tyrosine kinase domain (TKD), has been described in patients with acute myelogenous leukemia (AML). We analyzed the prevalence and the potential prognostic impact of FLT3 mutations in 979 AML patients. Results were correlated with cytogenetic data and the clinical response. FLT3-ITD mutations were found in 20.4% and FLT3-TKD mutations in 7.7% of the patients. Each mutation was associated with similar clinical characteristics and was more prevalent in patients with normal karyotype. Significantly more FLT3 aberrations were found in patients with FAB M5, and fewer were found in patients with FAB M2 and M6. Although less frequent in patients with cytogenetic aberrations, FLT3-ITDs were found in 13 of 42 patients with t(15;17) and in 9 of 10 patients with t(6;9). The prevalence of the ITD allele on the DNA level was heterogeneous, ranging from faint mutant bands in some patients to predominant mutant bands in others. Based on quantitative analysis, the mutant-wild-type (wt) ratio ranged from 0.03 to 32.56 (median, 0.78). Patients with a high mutant/wt ratio (ie, greater than 0.78) had significantly shorter overall and disease-free survival, whereas survival in patients with ratios below 0.78 did not differ from those without FLT3 aberrations. Multivariate analysis confirmed a high mutant/wt ratio to be a strong independent prognostic factor. Taken together, these data confirm that FLT mutations represent a common alteration in adult AML. Constitutive activation may be associated with monocytoid differentiation. A high mutant/wt ratio in ITD-positive patients appears to have a major impact on the prognostic relevance.
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            Prognostic implication of FLT3 and N-RAS gene mutations in acute myeloid leukemia.

            Internal tandem duplication of the FLT3 gene and point mutations of the N-RAS gene are the most frequent somatic mutations causing aberrant signal-transduction in acute myeloid leukemia (AML). However, their prognostic importance is unclear. In this study, their prognostic significance was analyzed in 201 newly diagnosed patients with de novo AML except acute promyelocytic leukemia. Three patients had mutations in both genes, 43 had only the FLT3 gene mutation, 25 had only the N-RAS gene mutation, and 130 had neither. These mutations seemed to occur independently. Both mutations were related to high peripheral white blood cell counts, and the FLT3 gene mutation was infrequently observed in the French-American-British (FAB)-M2 type. AML cases with wild FLT3/mutant N-RAS had a lower complete remission (CR) rate than those with wild FLT3/wild N-RAS, whereas the presence of mutant FLT3 did not affect the CR rate. Univariate analysis showed that unfavorable prognostic factors for overall survival were age 60 years or older (P =.0002), cytogenetic data (P =.002), FAB types other than M2 (P =.002), leukocytosis over 100 +/- 10(9)/L (P =.003), and the FLT3 gene mutation (P =.004). However, the N-RAS gene mutation was only a marginal prognostic factor (P =.06). For the subjects under 60 years old, multivariate analysis showed that the FLT3 gene mutation was the strongest prognostic factor (P =.008) for overall survival. The FLT3 gene mutation, whose presence is detectable only by genomic polymerase chain reaction amplification and gel electrophoresis, might serve as an important molecular marker to predict the prognosis of patients with AML.
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              Tandem-duplicated Flt3 constitutively activates STAT5 and MAP kinase and introduces autonomous cell growth in IL-3-dependent cell lines.

              We have recently identified an internal tandem duplication of the human Flt3 gene in approximately 20% of acute myeloid leukemia (AML) cases. In the present study, the wild-type and the mutant Flt3 genes were transfected into two IL-3-dependent cell lines, 32D and BA/F3 cells. Mutant Flt3-transfected cells exhibited autonomous growth while wild-type Flt3-transfected cells with the continuous stimulation of Flt3 ligand exhibited a minimal proliferation. Cells expressing mutant Flt3 showed constitutive activation of STAT5 and MAP kinase. In contrast, Flt3 ligand stimulation caused rapid activation of MAP kinase but not STAT5 in cells expressing wild-type Flt3. Finally, we found constitutive activation of MAP kinase and STAT5 in all clinical samples of AML patients with mutant Flt3. Our study shows the significance of internal tandem duplication of Flt3 receptors for leukemia cell expansion.
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                Author and article information

                Journal
                Korean J Hematol
                KJH
                The Korean Journal of Hematology
                Korean Society of Hematology; Korean Society of Blood and Marrow Transplantation; Korean Society of Pediatric Hematology-Oncology; Korean Society on Thrombosis and Hemostasis
                1738-7949
                2092-9129
                June 2011
                21 June 2011
                : 46
                : 2
                : 88-95
                Affiliations
                [1 ]Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea.
                [2 ]Department of Laboratory Medicine, Eulji University School of Medicine, Eulji General Hospital, Seoul, Korea.
                [3 ]Department of Internal Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea.
                [4 ]Department of Pediatrics, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea.
                Author notes
                Correspondence to Hyun-Sook Chi, M.D., Ph.D. Department of Laboratory Medicine, Asan Medical Center and University of Ulsan College of Medicine, 86, Asanbyungwon-gil, Songpa-gu, Seoul 138-736, Korea. Tel: +82-2-3010-4502, Fax: +82-2-478-0884, hschi@ 123456amc.seoul.kr
                Article
                10.5045/kjh.2011.46.2.88
                3128906
                21747880
                aafc978a-427c-438d-9b15-9c67f90b8894
                © 2011 Korean Society of Hematology

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 10 March 2011
                : 11 April 2011
                : 17 May 2011
                Categories
                Original Article

                Hematology
                normal karyotype,relapse,prognosis,aml,flt3 itd
                Hematology
                normal karyotype, relapse, prognosis, aml, flt3 itd

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