ACTIVATION OF INTERLEUKIN-1-BETA GENE-EXPRESSION DURING RETINOIC ACID-INDUCED GRANULOCYTIC DIFFERENTIATION OF PROMYELOID LEUKEMIA-CELL

We have examined the expression of the interleukin 1 beta (IL-1 beta) gene during the granulocytic differentiation of two promyeloid leukemi a cell lines, HL-60 and NB4. HL-60 is known to differentiate along the granulocytic pathway after treatment with 13-trans-retinoic acid (13- trans-RA), whereas treatment with phorbol myristate acetate (PMA) lead s to development of mature macrophages. NB4 cells are derived from the bone marrow of an acute promyelocytic leukemia (APL) patient in relap se, have a translocated RA receptor-alpha, and are converted into nond ividing granulocytes by 13-trans-RA treatment. When HL-60 or NB4 were cultured in the presence of 13-trans-RA, IL-1 beta mRNA and protein le vels were increased. In the more mature THP-1 cells which are induced to macrophage-like cells by 13-trans-RA treatment, RA was unable to in duce any IL-1 beta expression, implying that the effect of 13-trans-RA is associated with granulocytic differentiation. Moreover, PMA and 13 -trans-RA had a strong synergistic effect in the induction of IL-1 bet a gene expression. Nuclear run-off analysis indicated that the increas ed IL-1 beta gene expression was due to an enhanced rate of transcript ion. When the cells were transfected with an IL-1 beta-X-CAT reporter plasmid containing the -2982/-2748 promoter segment of the IL-1 beta g ene conferring responsiveness to PMA, both NB4 and HL-60 cells respond ed with increased CAT activity when stimulated with 13-trans-RA alone. In contrast to PMA, 13-trans-RA was unable to increase AP-1 enhancer activity. Thus, our data demonstrate that the IL-1 beta gene is activa ted during granulocytic differentiation and that the same enhancer seq uence of the IL-1 beta gene is activated by inducers of monocytic and granulocytic differentiation but probably via different mechanisms. Mo reover, these differentiative signals have a strong synergistic effect in the induction of IL-1 beta gene expression. As the IL-1 beta gene expression was similarly regulated by 13-trans-RA in NB4 cells and in HL-60 cells, it is probable that the 13-trans-RA signal in this case i s not affected by the 13-trans-RA receptor-alpha translocation.