[Identification of molecular markers in children with acute myeloid leukemia (AML)]

AML is an aggressive, phenotypically and genetically heterogenous clonal disease of hematopoietic progenitor cells with a great molecular variability. New WHO classification 2008 divides de novo AML according to cytogenetic and molecular prognostic and predictive markers. Recently, it is increasingly possible to identify a subgroup of poorer prognosis patients among those with normal karyotype AML. The aim of our study was to identify prognostically important molecular markers in children with AML, to stratify patients with normal karyotype and to monitor the disease according the genetic findings.

In 2008-2010, we analyzed bone marrow and peripheral blood samples of 20 children with de novo AML by conventional cytogenetic analysis, fluorescence in situ hybridisation and molecular diagnostics. The molecular analysis was performed on the cDNA level, with the restriction analysis of PCR products (FLT3-TKD), conventional PCR (MLL-PTD, NPM1mut, FLT3-ITD) and quantification RT-PCR method (expression of fusion transcripts, BAALC, WT1).

Samples from 20 children with AML were analyzed using the conventional cytogenetics, FISH and molecular methods. Abnormal karyotype was identified in 13 patients (65%). Further analysis revealed FLT3-ITD in 5/20 (25%), FLT3-TKD in 3/20 (15%), NPM1mut in 2/20 (10%) and MLL-PTD in 1/20 (5%), overexpression of WT1 gene in 15/20 (75%) and overexpression of BAALC in 13/20 (65%) patients.

Wide cytogenetic and molecular screening helped to find at least one genetic marker in all 20 patients for later follow-up and risk stratification. 4/20 (20%) patients died of the disease progression.