One gene downregulated by AML1/ETO in vitro, Williams Beuren syndrome critical region 5 (WBSCR5), was expressed in primary t(8;21)-negative AML blasts but not in primary t(8;21)-positive AML blasts, strongly implying a role of this gene in the phenotype of t(8;21)-positive AML.     ///    " The chromosomal translocation t(8;21) fuses the AML1 (RUNX1) gene on chromosome 21 and the ETO gene on chromosome 8 in human acute myeloid leukemias (AMLs), resulting in expression of the chimeric transcription factor AML1/ETO. "    ///    We used an ecdysone-inducible expression system in the human monoblastic U-937 cell line to isolate genes that were differentially expressed upon induction of AML1/ETO expression.     ///    "By representational difference analysis (cDNA-RDA), we identified 26 genes whose expression levels were significantly modulated following AML1/ETO induction for 48 h. "    ///    AML1/ETO-associated dysregulation of gene expression was not mediated by a TSA-sensitive mechanism.     ///    Williams-Beuren syndrome critical region-5/non-T-cell activation linker: a novel target gene of AML1/ETO..     ///    "None of these genes has previously been described as a target of AML1, ETO or AML1/ETO. "    ///    AML1/ETO-mediated dysregulation of target genes critical for hematopoietic differentiation and proliferation is thought to contribute to the leukemic phenotype.     ///    "Three out of eight genes including WBSCR5 were regulated during ATRA-induced monocytic differentiation of U-937 cells, however, none of them antagonistically, upon both ATRA treatment and AML1/ETO induction. "    ///    The identified genes provide a useful model to study the mechanism by which the AML1/ETO fusion protein exerts its function in transcriptional dysregulation in AML. 