Gene expression signatures and ex vivo drug sensitivity profiles in children with acute lymphoblastic leukemia

Causes of treatment failure in acute lymphoblastic leukemia (ALL) are still poorly understood. Microarray technology gives new possibilities for the analysis of the biology of leukemias. We hypothesize that drug sensitivity in pediatric ALL is driven by specific molecular mechanisms that correlate with gene expression profiles assessed by microarray analysis. The aim of the study was to determine the ex vivo resistance profiles of 20 antileukemic drugs and gene expression profiles, with relation to response to initial therapy. Lymphoblasts were analyzed after bone marrow biopsy was obtained from 56 patients. The profile of in vitro resistance to drugs was determined in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cytotoxicity assay. High-quality total RNA was prepared and hybridized to oligonucleotide arrays HG-U133A 2.0 Chip (Affymetrix). The expression of selected genes was tested by qualitative reverse transcription polymerase chain reaction (qRT-PCR). The exposure of leukemic blasts to drugs initiates a complex cellular response, which reflects global changes in gene expression. Changes in the expression of several genes are highly correlated with drug resistance.