This study looked at how the gene for thymosin‑beta‑4 behaves in blood‑cancer cells and found it turns on more when those cells start to change into more mature types, especially in certain T‑cell cancers.

Thymosin beta 4 (T beta 4) 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 T beta 4 expression, we studied T beta 4 gene expression in various leukemic cells and in established cell lines. Among leukemic cell samples obtained from leukemia patients, the T beta 4 gene was highly expressed in a lymphoid lineage, especially in adult T-cell leukemia (ATL) cells, rather than in a granulocyte lineage. The T beta 4 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 from one of the ATL patients transcribed a heterogeneous message. T beta 4 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 T beta 4 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 T beta 4 may be a new marker of differentiation of hematopoietic cells.