title: Activation of protein kinase C enhances TNF-alpha-induced differentiation by preventing apoptosis via rapid up-regulation of c-Myc protein expression in HL-60 cells.
abstract: Tumor necrosis factor-alpha (TNF-alpha) induces both rapid onset of apoptosis and monocytic differentiation in HL-60 human myeloid leukemia cells. In this study, we examined the effect of activation of protein kinase C (PKC) in c-Myc protein expression in association with the induction of apoptosis and differentiation in TNF-alpha-treated HL-60 cells. Pretreatment with phorbol 12-myristate 13-acetate (PMA), an activator of PKC, prevented TNF-alpha-induced rapid onset of apoptosis, which occurs at 3 h culture with TNF-alpha, concomitantly with the up-regulation of c-Myc protein expression. In addition, PMA enhanced TNF-a-induced differentiation at 24h treatment. This was documented by the expression of integrin Mac-1 molecule (CD11b) on the cell surface and the cellular adhesion to the plastic bottom of the flask, indicating the differentiation along with the monocyte/macrophage lineage. These results indicate that activation of PKC not only counteracts apoptosis but also enhances differentiation in TNF-alpha-treated HL-60 cells. Up-regulation of c-Myc protein evoked by pretreatment with PMA for a short time could disturb the signaling pathway of the ceramide and sphingosine, which are known to function as the endogenous modulators mediating the apoptotic signal of TNF-alpha. Our results strongly suggest the role of c-Myc protein as a mediator of cytoprotective effect of PKC pathway, and PKC pathway opposes apoptosis and consequently undergo differentiation via rapid up-regulated c-Myc protein expression during TNF-alpha signaling of HL-60 cells. Our findings provide a new insight for a role of PKC and c-Myc protein with special reference to the regulatory mechanisms in the decision of cellular fate, differentiation or apoptosis.
authors.affiliation: Division of Blood Transfusion, Shimane Medical University, Izumo, 693-8501, Japan. kumakura@shimane-med.ac.jp
authors.forename: Shunichi
authors.initials: S
authors.lastname: Kumakura
authors.forename: Hiroto
authors.initials: H
authors.lastname: Ishikura
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Maniwa
authors.forename: Shoso
authors.initials: S
authors.lastname: Munemasa
authors.forename: Hiroto
authors.initials: H
authors.lastname: Tsumura
authors.forename: Junichi
authors.initials: J
authors.lastname: Masuda
authors.forename: Shotai
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D039481:CD11b Antigen / Q000032:analysis; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D016259:Genes, myc; D018922:HL-60 Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D009363:Neoplasm Proteins / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology*; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D039481:CD11b Antigen; D009363:Neoplasm Proteins; D016271:Proto-Oncogene Proteins c-myc; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate