Molecular characterization of acute leukemias by use of microarray technology

Accurate subclassification of leukemia and the identification of prognostic determinants are essential to guide therapy and to improve patients' outcome. According to present standards, pre-therapeutic assessment depends on a combination of different methods. We aimed to expand the molecular characterization of different acute leukemia subtypes to identify new genome-wide diagnostic markers. Total RNA from 90 adult patients suffering from acute lymphoblastic leukemia (ALL, n = 25) and acute myeloid leukemia (AML, n = 65) was extracted at diagnosis and high density oligonucleotide microarrays were used to analyze the expression profiles of 12,000/22,000 genes in all specimens (Affymetrix U95Av2/U133A). All cases were thoroughly characterized by individual combinations of cytomorphology, cytogenetics, multiparameter immunophenotyping, and molecular genetics. The expression signature of a small set of differentially expressed genes was sufficient to accurately discriminate eight clinically relevant acute leukemia subgroups. Underlying chromosomal aberrations or immunophenotypical characteristics were strictly correlated with a distinct gene expression pattern for AML with t(8;21), t(15;17), t(11q23)/MLL, or inv(16) as well as for precursor B-ALL with t(9;22), t(8;14), or t(11q23)/MLL and precursor T-ALL. These data support a possible future application of microarray technology for classification of the acute leukemias.