Expression data from ALL patients included in the set used to construct a classification signature (COALL cohort). Homo sapiens

Childhood acute lymphoblastic leukemia (ALL) comprises a large group of genetic subtypes with a favorable prognosis characterized by a TEL-AML1-fusion, hyperdiploidy (>50 chromosomes) or E2A-PBX1 fusion and a smaller group with unfavorable outcome characterized by either a BCR-ABL-fusion, MLL-rearrangement or T-ALL. About 25% of precursor B-ALL are currently genetically unclassified and have an intermediate prognosis. The present study used genome-wide strategies to reveal new biological insights and advance the prognostic classification of childhood ALL. A double-loop cross validation was used to construct a classifier based on gene expression in ALL cells from 190 newly diagnosed cases (COALL cohort, GEO GSE13425) with a prediction accuracy of 90%. T-ALL, TEL-AML1-positive, hyperdiploid and E2A-rearranged cases were identified with 100% sensitivity and ≥94% specificity. The classifier accuracy was confirmed in an independent cohort of 107 cases (87.9%, DCOG cohort, GEO GSE13351). Keywords: gene expression study for classification of ALL subtypes Overall design: 190 bone marrow and peripheral blood samples were collected at diagnosis and frozen. They were later thawed and hybridized to Affymetrix U133A arrays.