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Zinc (Zn) is an essential heavy metal that is incorporated into a number of human Zn metalloproteins. Zn plays important roles in nucleic acid metabolism, cell replication, and tissue repair and growth. Zn deficiency is associated with a range of pathological conditions, including impaired immunity, retarded growth, brain development disorders and delayed wound healing. Moreover, many reports have suggested that Zn is involved in cancer development and levels of Zn in serum and malignant tissues of patients with various types of cancer are abnormal. Zn may directly affect tumor cells by regulating gene expression profiles and/or cell viability, both of which are mediated in part by tumor-induced changes in Zn transporter expression. On the other hand, Zn may indirectly influence tumor cells by affecting processes within the cancer microenvironment, including immune responses; the functions and/or activity levels of immune cells that attack tumor cells are influenced by the intracellular Zn concentrations within those cells. In both cases, Zn contributes to intracellular metal homeostasis and/or signal transduction in tumor and immune cells. In this review article, we will summarize the current understanding of the roles of Zn homeostasis and signaling primarily in immune cells, with a discussion of the contributions of these processes to oncogenesis. ( Cancer Sci 2008; 99: 1515–1522) [ABSTRACT FROM AUTHOR]

Zinc is an essential element, necessary for sustaining all life. Zinc deficiency causes taste impairments, immune deficiency, skin problems, and growth and mental retardation. Recent reports suggest that zinc is associated with an increased risk of cancer, although it is still unclear whether zinc or its transporters are involved in cancer progression. Here we show that zinc and its transporter ZIP10 are involved in the invasive behavior of breast cancer cells. The screening of clinical samples for ZIP10 mRNA expression suggested that ZIP10 was significantly associated with the metastasis of breast cancer to the lymph node. In addition, the expression of ZIP10 mRNA was higher in the invasive and metastatic breast cancer cell lines MDA-MB-231 and MDA-MB-435S than in less metastatic breast cancer cell lines, such as MCF7, T47D, ZR75-1 and ZR75-30. In in vitro cell migration assays, the depletion of zinc transporter ZIP10 and intracellular zinc inhibited the migratory activity of MDA-MB-231 and MDA-MB-435S cells. These results showed that zinc and ZIP10 play an essential role in the migratory activity of highly metastatic breast cancer cells, and suggest ZIP10 as a possible marker for the metastatic phenotype of breast cancer and a promising target of novel treatment strategies. ( Cancer Sci 2007; 98: 692–697) [ABSTRACT FROM AUTHOR]

Dendritic cells (DC) play a central role in immune responses by presenting antigenic peptides to CD4+ T cells through MHCII molecules. Here, we demonstrate a TRIF–GEFH1–RhoB pathway is involved in MHCII surface expression on DC. We show the TRIF (TIR domain-containing adapter inducing IFNβ)- but not the myeloid differentiation factor 88 (MyD88)-dependent pathway of lipopolysaccharide (LPS)-signaling in DC is crucial for the MHCII surface expression, followed by CD4+ T-cell activation. LPS increased the activity of RhoB, but not of RhoA, Cdc42, or Rac1/2 in a manor dependent on LPS-TRIF- but not LPS-Myd88-signaling. RhoB colocalized with MHCII+ lysosomes in DC. A dominant-negative (DN) form of RhoB (DN-RhoB) or RhoB's RNAi in DC inhibited the LPS-induced MHCII surface expression. Moreover, we found GEFH1 associated with RhoB, and DN-GEFH1 or GEFH1's RNAi suppressed the LPS-mediated RhoB activation and MHCII surface expression. DN-RhoB attenuated the DC's CD4+ T-cell stimulatory activity. Thus, our results provide a molecular mechanism relating how the MHCII surface expression is regulated during the maturation stage of DC. The activation of GEFH1-RhoB through the TRIF-dependent pathway of LPS in DC might be a critical target for controlling the activation of CD4+ T cells. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome (SARS) has become a global public health emergency. p38 mitogen-activated protein kinase (MAPK) and its downstream targets are activated in SARS coronavirus (SARS-CoV)-infected Vero E6 cells and activation of p38 MAPK enhances the cytopathic effects of SARS-CoV infection. In addition, weak activation of Akt cannot prevent SARS-CoV infection-induced apoptosis in Vero E6 cells. In the present study, we demonstrated that signal transducer and activator of transcription (STAT) 3, which is constitutively phosphorylated at tyrosine (Tyr)-705 and slightly phosphorylated at serine (Ser)-727 in Vero E6 cells, was dephosphorylated at Tyr-705 on SARS-CoV infection. In addition to phosphorylation of p38 MAPK in virus-infected cells, other MAPKs, i.e., extracellular signal-regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase (JNK), were phosphorylated. Although inhibitors of ERK1/2 and JNK (PD98059 and SP600125) had no effect on phosphorylation status of STAT3, inhibitors of p38 MAPK (SB203580 and SB202190) partially inhibited dephosphorylation of STAT3 at Tyr-705. Tyr-705-phosphorylated STAT3 was localized mainly in the nucleus in mock infected cells, whereas STAT3 disappeared from the nucleus in virus-infected cells. As STAT3 acts as an activator of transcription in the nucleus, these results suggest that STAT3 lacks its activity on transcription in SARS-CoV-infected Vero E6 cells. [Copyright &y& Elsevier]

The O-linked sugar chains were liberated from porcine zona pellucida glycoproteins by alkaline-borohydride treatment and the structures of neutral oligosaccharides were determined. The major oligosaccharides had the following structures with type-1 cores, (Galβ1→4GlcNAcβ1→3)1 3-Galβ1→3N-acetylgalactosaminitol (54%) and GlcNAcβ1→3(Galβ1→4GlcNAcβ1→3)0 1Galβ1→3N-acetylgalactosaminitol (16%). Approximately 6% of the oligosaccharides had the structure with a type-3 core. Galβ1→4GlcNAcβ1→3N-acetylgalactosaminitol. Oligosaccharides having α-galactose (2%) and β-GalNAc (4%) at their non-reducing termini were also found as minor components. [ABSTRACT FROM AUTHOR]

The signal transducer and activator of transcription molecules (STATs) play key roles in cytokine-induced signal transduction. However, their role in cell growth has not been clear. In the present study, we show that STAT3 plays a key role in the G1 to S phase cell-cycle transition induced by the cytokine receptor subunit gp130, through the upregulation of cyclins D2, D3 and A, and cdc25A, and the concomitant downregulation of p21 and p27. Furthermore, unexpectedly, we found that gp130 could induce the expression of p21 when STAT3 activation was suppressed. Such contradictory signals regulating cell-cycle progression could be simultaneously delivered from distinct cytoplasmic regions of gp130. We propose an ‘orchestrating model’ for cytokine and growth factor action in which contradictory signals are orchestrated to produce a specific effect in a target cell. [ABSTRACT FROM AUTHOR]

In response to interferon-γ (IFN-γ), Stat1 is tyrosine phosphorylated and translocates to the nucleus where it activates transcription. In this study, we identified factors which mediate the nuclear import of Stat1. Tyrosine­phosphorylated Stat1 associated with the β subunit (a 97 kDa component) of the nuclear pore-targeting complex via the NPI-1 family, but not the Rch1 family, of α subunit (a 58 kDa component) as a result of IFN-γ stimulation. Antibodies against NPI-1 or β subunit consistently inhibited the IFN-γ-dependent nuclear import of Stat1 in living cells, although anti-bodies reactive to Rch1 had no effect. Solution binding assays with deletion mutants of NPI-1 showed that the Stat1-binding domain of NPI-1 was located in the carboxy­terminal region, which is clearly distinct from the SV40 large T antigen nuclear localization signal (NLS)-binding region. These results indicate that the extracellular signal-dependent nuclear transport of Stat1 is mediated by NPI-1, but not Rch1, in conjunction with β subunit, and that these factors participate in, not only constitutive, but also the conditional nuclear import of proteins. [ABSTRACT FROM AUTHOR]

IL-6 induces differentiation of PC12 cells pretreated with nerve growth factor (NGF). We explored the signals required for neurite outgrowth of PC12 cells by using a series of mutants of a chimeric receptor consisting of the extracellular domain of the granulocyte-colony stimulating factor (G-CSF) receptor and the cytoplasmic domain of gp130, a signal-transducing subunit of the IL-6 receptor. The mutants incapable of activating the MAP kinase cascade failed to induce neurite outgrowth. Consistently, a MEK inhibitor, PD98059, inhibited neurite outgrowth, showing that activation of the MAP kinase cascade is essential for the differentiation of PC12 cells. In contrast, a mutation that abolished the ability to activate STAT3 did not inhibit, but rather stimulated neurite outgrowth. This mutant did not require NGF pretreatment for neurite outgrowth. Dominant-negative STAT3s mimicked NGF pretreatment, and NGF suppressed the IL-6-induced activation of STAT3, supporting the idea that STAT3 might regulate the differentiation of PC12 cells negatively. These results suggest that neurite outgrowth of PC12 cells is regulated by the balance of MAP kinase and STAT3 signal transduction pathways, and that STAT3 activity can be regulated negatively by NGF. [ABSTRACT FROM AUTHOR]

Affinity cross-linking of 125I-labeled recombinant human interleukin-6 (IL-6) to human hepatoma cells (HepG2) allowed the detection of three IL-6-containing complexes with molecular masses of 100 kDa, 120 kDa and 200 k Da. Treatment of HepG2 cells with dexamethasone led to a time- and dose-dependent up-regulation of IL-6-receptor mRNA levels. By the use of cross-linking this effect was also seen at the protein level, where all three IL6-binding complexes increased upon incubation of HepG2 cells with dexamethasone. Under conditions of IL-6-receptor up-regulation by dexamethasone, γ-fibrinogen mRNA induction by IL-6 is stronger and occurs earlier than without dexamethasone. We propose therefore that the expression of the IL-6 receptor might be a rate-limiting step in acute-phase-protein induction. [ABSTRACT FROM AUTHOR]

The plasma half-life of recombinant human interleukin-6 (rhIL-6) was determined in rats by measuring the disappearance of the biological activity as well as of the radioactivity of 125I-rhIL-6 from the circulation. The kinetics of clearance were biphasic. It consisted of a rapid initial disappearance corresponding to a half-life of 3 min, and of a second slow one corresponding to a half-life of about 55 min. By cellulose-acetate electrophoresis it was shown that rhIL-6 binds to a plasma protein resulting in a complex migrating in the β-γ region; 20 min after intravenous injection, about 80% of the 125I-rhIL-6 that had disappeared from the circulation was found in the liver. 125I-rhIL-6 was exclusively localized on the surface of parenchymal cells suggesting the existence of an interleukin-6 receptor on the hepatocytes. [ABSTRACT FROM AUTHOR]

Secretory products of cultured human blood monocytes contain a hepatocyte-stimulating factor which is able to induce the acute-phase proteins α2-macroglobulin and fibrinogen in rat liver cells. Total RNA was isolated from unstimulated and lipopolysaccharide-stimulated human monocytes and translated in a reticulocyte lysate. The capability of the cell-free synthesized proteins to induce the acute-phase proteins a2-macroglobulin and fibrinogen was assayed in rat hepatocyte primary cultures and in the rat hepatoma cell line Fao. The products translated from the mRNA of lipopolysaccharide-stimulated human monocytes induced mRNAs for α2-macroglobulin and fibrinogen and therefore contain hepatocyte-stimulating factor. The translation products of unstimulated monocytes had no effect. A cDNA containing the coding sequence for interleukin-6 (B-cell stimulatory factor 2, interferon-β2/26-kDa protein, interleukin HP1) derived from human T-cells cloned into the transcription vector pGEM4 was transcribed in vitro. Translation of the isolated RNA in a reticulocyte lysate led to the synthesis of a protein of about 25 kDa. This cell-free synthesized interleukin-6 exhibited hepatocyte-stimulating activity measured by the induction of β-fibrinogen mRNA in Fao cells. Using an antibody against interleukin-6, two proteins of 22 kDa and 23 kDa were immunoprecipitated from the culture medium of lipopolysaccharide-stimulated human monocytes. These two proteins were not synthesized by unstimulated monocytes. When total RNA from unstimulated human monocytes and lipopolysaccharide-stimulated human monocytes and lymphocytes was subjected to Northern analysis and hybridized with the interleukin-6 cDNA, a strong hybridization signal corresponding to an RNA of about 1300 bases was detected only in the RNA from lipopolysaccharide-stimulated human monocytes, indicating that human monocytes express the interleukin-6 gene after stimulation. The data presented in this paper strongly suggest that hepatocyte-stimulating factor from human monocytes and interleukin-6 from T-cells are identical. [ABSTRACT FROM AUTHOR]

The regulation of the three major acute-phase proteins α2-macroglobulin, cysteine proteinase inhibitor and α1-antitrypsin by recombinant human interleukin-1β, recombinant human interleukin-6 and recombinant human tumor necrosis factor α was studied in rat hepatocyte primary cultures. Synthesis and secretion of the acute-phase proteins was measured after labeling with [35S]methionine and immunoprecipitation. Incubation of hepatocytes with interleukin-6 led to dose-dependent and time-dependent changes in the synthesis of the three major acute-phase proteus and albumin, similar to those occurring m vivo during experimental inflammation. α2-Macroglobulin and cysteine proteinase inhibitor synthesis was induced 54-fold and 8-fold, respectively, 24 h after the addition of 100 units/ml interleukin-6. At the same time synthesis of the negative acute-phase protein albumin was reduced to 30% of controls. Half-maximal effects were achieved with 4 units interleukin-6/ml. Interleukin-lβ bad only a partial effect on the regulation of the fore proteins studied: only a twofold stimulation of α2-macroglobulin and a 60% reduction of albumin synthesis were observed. Tumor necrosis factor α did not alter the synthesis of acute-phase proteins. The stimulation of α2-macroglobulin and cysteine proteinase inhibitor synthesis by interleukin-6 was inhibited by interleukin-lβ in a dose-dependent manner. In pulse-chase experiments the effect of interleukin-lβ, interleukin-6 and tumor necrosis factor a on the secretion of acute-phase proteins was examined. Interleukin-6 markedly accelerated the secretion of total proteins and α2-macroglobulin, whereas the secretion of cysteine proteinase inhibitor, α1-antitrypsin and albumin was not affected. The inhibition of N-glycosylation by tunicamycin abolished the effect of interleukin-6 on the secretion of α2-macroglobulin, indicating a possible role of interleukin-6 on N-glycosylation. [ABSTRACT FROM AUTHOR]