H-FERRITIN AND L-FERRITIN GENE-EXPRESSION IN U937 CELLS INDUCED TO MACROPHAGE DIFFERENTIATION

Ferritin is an ubiquitous protein that has been shown to regulate cell differentiation in several experimental systems. In this study we hav e investigated the expression of ferritin genes encoding the heavy (H) and light (L) chains in the U937 cell line, induced to differentiate to macrophage-like cells by 12-O-tetradecanoylphorbol-13-acetate (TPA) , retinoic acid (RA) or 1-beta-D-arabinofuranosylcytosine (Ara-C). An increase in the level of H ferritin mRNA was detected in U937 cells th at had been incubated with Ara-C. Treatment of U937 cells with Actinom ycin D suggested that the H ferritin mRNA increase was mediated by pos t-transcriptional mechanisms. The L ferritin mRNA level increased only following stimulation of U937 cells with RA. Immunophenotypic and cyt ochemical analyses showed that Ara-C was the strongest inducer of the macrophagic differentiation of U937 cells. These results suggest that the increase of H ferritin mRNA expression may represent a sensitive m arker of myeloid cells differentiating along the monocyte-macrophage l ineage.