When a human leukemic cell line, HT93 was incubated with all-trans retinoic acid (ATRA), IL-5, or both, this cell line was differentiated into eosinophic lineage, in that an eosinophilic specific granule proteins, major basic protein (MBP) and eosinophil peroxidase (EPO) appeared. Both CD11b and CC chemokine receptor, CCR3 expression were upregulated, while CD71 expression was downregulated by ATRA or ATRA+IL-5. Concomitantly, marked production of eotaxin-2/CCL24 was observed, but no production of eotaxin-1/CCL11 and eotaxin-3/CCL26 was detected. Since only 20 to 30% cells incubated with ATRA became positive for CCR3, CCR3+ population was enriched by a magnetic activated cell sorter (MACS). Enriched CCR3+ population produced higher eotaxin-2/CCL24 than the CCR3- population, indicating that differentiated eosinophils are capable of producing eotaxin-2/CCL24. During the ATRA-induced differentiation, expression of a transcriptional factor, GATA-1 was significantly increased. Introduction of siRNA against GATA-1 markedly reduced the ATRA-induced differentiation markers including CD11b and CCR3, as well as reduced eotaxin-2/CCL24 production. Finally, ATRA-induced differentiation and eotaxin-2/CCL24 production were greatly enhanced in the GATA-1-overexpressed clones. These results indicate that the ability to produce eotaxin-2/CCL24 is acquired during the differentiation into eosinophilic lineage which is dependent on GATA-1 expression.
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