Expression of the thymosin β4 gene during differentiation of hematopoietic cells

Abstract

Thymosin β4 (Tβ4) was originally isolated as a thymic hormone. Its functional properties remain obscure; however, the N-terminal peptidic sequence could have a regulatory function on hematopoietic stem cell proliferation. To investigate the mechanism of Tβ4 expression, we studied Tβ4 gene expression in various leukemic cells and in established cell lines. Among leukemic cell samples obtained from leukemia patients, the Tβ4 gene was highly expressed in a lymphoid lineage, especially in adult T-cell leukemia (ATL) cells, rather than in a granulocyte lineage. The Tβ4 gene was more transcriptionally active in chronic B-cell leukemia than in acute B-cell leukemia, while it was inactive in plasma cell leukemia. We also found that cells om one of the ATL patients transcribed a heterogeneous message. Tβ4 messenger RNA increased in MOLT-3 during differentiation by 12-O-tetradecanoylphorbol-13-acetate (TPA). in HL60 cells induced by TPA or dimethylsulfoxide and K562 cells stimulated by cytosine arabinoside or hemin. The genomic sequence of Tβ4 is considered to be highly conserved. Only 1 of 20 genomes from normal or hematopoietic malignant cells showed restriction fragment length polymorphism. These findings, along with previous data, suggest that Tβ4 may be a new marker of differentiation of hematopoietic cells. © 199O by The American Society of Hematology.