Abstract
Abstract Aim: Activating mutations of FLT3 are commonly found in AML patients and reported to be associated with poor clinical outcome. We aimed to evaluate the incidence of FLT3 mutations along with FLT3 mRNA and CD135 protein expression in AML patients of western India and their role in prognosis of disease. Method: Analysis for the detection of FLT3 internal tandem duplication (ITD), Tyrosine kinase domain (TKD) point mutations and quantification of mRNA level was carried out in total 174 de novo patients diagnosed with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and aplastic anemia using PCR and RT-PCR methods. FLT3 protein was quantified by flow cytometry on leukemic blasts. Results: The incidence of FLT3 ITD, FLT3 TKD mutations and CD135 protein expression was found to be 19%, 7% and 62% respectively in AML patients. In MDS, only FLT3 ITD mutation and CD135 protein over expression could be analyzed, incidence of which was 22% and 60%. In aplastic anemia, FLT3 mutations, FLT3 mRNA and protein over expression were not detected. FLT3 mutations as well as FLT3 mRNA and protein over expression were prominently noted in AML subtypes associated with myelo-monocytic lineage. CD135 protein over expression was significantly associated with reduced Disease Free Survival (DFS) whereas WBC and blasts emerged as poor prognostic factors with respect to Disease Free Survival (DFS) and Overall Survival (OS) respectively in multivariate analysis. Conclusion: Our data suggest that CD135 receptor protein over expression is a potential prognostic marker as well as molecular target for FLT3 inhibitors in AML patients.
Highlights
Fms-like tyrosine kinase 3 (FLT3), known as stem cell tyrosine kinase 1 (STK1) [1] or fetal liver kinase 2 [2], belongs to the group of class III receptor tyrosine kinases along with structurally similar growth receptors such as c-kit, PDGF-R and c-fms [3]
Our data suggest that CD135 receptor protein over expression is a potential prognostic marker as well as molecular target for FLT3 inhibitors in Acute Myeloid Leukemia (AML) patients
The incidence of FLT3 Internal tandem duplication (ITD) was higher as compared to FLT3 tyrosine kinase domain (TKD) mutations
Summary
Fms-like tyrosine kinase 3 (FLT3), known as stem cell tyrosine kinase 1 (STK1) [1] or fetal liver kinase 2 (flk1) [2], belongs to the group of class III receptor tyrosine kinases along with structurally similar growth receptors such as c-kit, PDGF-R and c-fms [3]. Internal tandem duplication (ITD) in the juxtamembrane domain – coding sequence, in exons 14 and 15 of FLT3 gene [5], was first identified by Nakao et al in 1996 [4] The length of these mutations varies but they are always in frame, producing a functional protein [8]. Such insertions leads to FLT3 ligand-independent kinase activation, stimulating proliferation and inhibition of apoptosis and in vitro studies show proliferation of Acute Myeloid Leukemia (AML) cells [9,10,11]. These point mutations have been reported in 7% of AML patients [12,13]
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