Overexpression of novel short isoforms of Helios in a patient with T-cell acute lymphoblastic leukemia

Objective. In previous studies, we demonstrated overexpression of the dominant-negative isoform of the transcription factor Ikaros, Ik-6, in patients with blast crisis of chronic myelogenous leukemia and B-cell acute lymphoblastic leukemia. In the present study, we analyzed expression of the Ikaros family genes Ikaros, Aiolos, and Helios in a panel of human T-cell leukemia/lymphoma cell lines and bone marrow samples of patients with T-cell acute lymphoblastic leukemia. Materials and Methods. We performed reverse transcriptase polymerase chain reaction, sequencing analysis, immunoblotting, and Southern blotting. Results. We found overexpression of novel short isoforms of Helios (Hel-5 and Hel-6) in the HD-Mar cell line. Southern blot analysis suggested that there might be a small deletion in the Helios locus of RD-Mar. In addition, we observed decreased expression of more than one Ikaros family gene in 3 of 9 patients with T-cell acute lymphoblastic leukemia. Moreover, one of the patients overexpressed novel short isoforms of Helios (Hel-7 and Hel-8). Conclusion. This study provides the first evidence of an Ikaros family member (other than Ikaros) of which novel short isoforms become overexpressed in human leukemia. (C) 2002 International Society for Experimental Hematology. Published by Elsevier Science Inc.