We examined the significance of t(8;21) chromosomal aberration for VPA treatment response among acute myeloid leukemia (AML) patients by direct comparison of AML1/ETO-negative vs.     ///    AML1/ETO-positive leukemia shows specific mechanism of VPA residing from differentiation followed by apoptosis that is accompanied by an increase in the expression of repressed AML1 target genes.     ///    VPA induced apoptosis in AML1/ETO-positive and MLL-AF4-positive cells in a dose-dependent manner.     ///    "VPA increased the expression of AML1 target genes - PU.1, C/EBPa, BPI and IGFBP7 only in AML1/ETO-positive cells. "    ///    "Differentiation, as indicated by changes in immunophenotype, was observed only in AML1/ETO-positive cells. "    ///    Our data suggest that AML1/ETO-positive patients might derive the greatest benefit from VPA treatment..     ///    Valproic acid triggers differentiation and apoptosis in AML1/ETO-positive leukemic cells specifically..     ///    This AML1/ETO-specific effect was confirmed also using patient blasts isolated at the time of diagnosis. 