title: Retinoic acid promotes phorbol ester-initiated macrophage differentiation in HL-60 leukemia cells without disappearance of protein kinase C.
abstract: The ability of retinoic acid (RA) to promote 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-initiated macrophage differentiation was examined in human promyelocytic leukemia cell line HL-60. One-hour exposure to 10 nM TPA and subsequent exposure for 48 h to 1 microM RA following removal of TPA rapidly induced the macrophage phenotype in 65% of the cells. This effect was comparable to continuous exposure for 48 h to TPA alone, but contrasted with the absence of macrophage-like cells after RA treatment alone or the induction of 10% of the cell population to a macrophage phenotype after 1-h exposure to TPA. The effect of TPA + RA was accompanied by increased cell adherence and increased nonspecific esterase activity but not by a change in the reduction of nitroblue tetrazolium. Protein kinase C (PK-C) activity was increased 35-40% in cells treated for 1 h with TPA alone or after subsequent exposure to RA. Cells treated for 48 h with RA exhibited a 2-fold increase in PK-C activity while cells exposed to TPA for 48 h lost all PK-C activity. The changes in PK-C activity in TPA + RA-treated cells were accompanied by Ca2+/phospholipid(PL)-dependent phosphorylation in vitro of pp38 which is characteristic of treatment with RA alone, as well as the Ca2+/PL-independent phosphorylation in vitro of pp82 and pp130 (vinculin) which is prevalent in cells treated continuously with TPA alone and is absent in RA-treated cells. These results indicate that the macrophage phenotype induced by TPA + RA is similar to that produced by continuous exposure to TPA alone with respect to their in vitro phosphoprotein patterns, cytochemical markers, cell adherence and morphology, but that the disappearance of PK-C is not an obligatory characteristic of these cells.
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000201:enzymology / Q000473:pathology*; D008264:Macrophages / Q000166:cytology*; D009124:Muscle Proteins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000032:analysis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014212:Tretinoin / Q000494:pharmacology*; D016596:Vinculin
chemical_list: D009124:Muscle Proteins; D016596:Vinculin; D014212:Tretinoin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate