All trans retinoic acid (ATRA), a differentiation inducer for human myeloid NB4 cells, induced accumulation of lipid droplet as determined by positivity of Nile Red and Oil Red O in this cell line. Granulocyte colony-stimulating factor (G-CSF), although not having detectable effect by itself, exerted the additive effects on lipid droplet formation in NB4 cells when combined with ATRA. mRNA analysis for peroxisome proliferatoractivated receptors (PPARs) revealed the initial transient

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... on followed by upregulation of the transcript for PPARg2, a master molecule for adipogenesis, and upregulation of PPARa. BADGE, a synthetic antagonist for PPARg, potently inhibited lipid droplet formation in NB4 cells stimulated by ATRA and/or G-CSF, but not the functional differentiation of the cells by ATRA and/or G-CSF. These results suggest that ATRA and G-CSF induce lipid droplet formation via certain PPARg-mediated specific mechanisms in human myeloid NB4 cells during functional differentiation.