title: 12-O-tetradecanoylphorbol-13-acetate-induced apoptosis is mediated by tumor necrosis factor alpha in human monocytic U937 cells.
abstract: 12-O-tetradecanoylphorbol-13-acetate (TPA), a phorbol ester that is known as a tumor promoter, induces differentiation of myeloid cells and suppresses their proliferation. We studied the regulation of apoptosis by TPA in human monocytic cell line U937 cells that lack p53. Untreated U937 cells constitutively underwent apoptosis, and TPA enhanced apoptosis in these cells. Further studies showed that TPA increased production of tumor necrosis factor-alpha (TNFalpha) in U937 cells, and exogenously added TNFalpha induced apoptosis. Moreover, the induction of apoptosis by TPA was blocked by anti-TNFalpha antibody. Similar results were obtained in the myeloblastic cell line KY821 cells. We also found that the induction of apoptosis by TPA was increased in cells overexpressed with TNF receptor 1 but not in control cells. Furthermore, TPA failed to induce the production of TNFalpha and apoptosis in cells with either their protein kinase C or mitogen-activated protein kinase pathway blocked. Our results indicate that TPA induces apoptosis, at least in part, through a pathway that requires endogenous production of TNFalpha in U937 cells. Our data also suggest that the induction of apoptosis by TPA occurs through activation of protein kinase C and mitogen-activated protein kinase and TNFalpha is an autocrine-stimulating factor for the induction of apoptosis in these cells.
authors.affiliation: Division of Radiation Health, National Institute of Radiological Sciences, Chiba, 263-8555 Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Takada
authors.forename: M
authors.initials: M
authors.lastname: Hachiya
authors.forename: Y
authors.initials: Y
authors.lastname: Osawa
authors.forename: Y
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: K
authors.initials: K
authors.lastname: Ando
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Akashi
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001483:Base Sequence; D017931:DNA Primers; D006801:Humans; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D020298:U937 Cells
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; C482576:MAP3K1 protein, human; D013755:Tetradecanoylphorbol Acetate