Swift elimination of undesirable cells is an important feature in tumour suppression and immunity. The tumour suppressor p53 and interferon-a and -b (IFN-a/b) are essential for the induction of apoptosis in cancerous cells and in antiviral immune responses, respectively, but little is known about their interrelationship. Here we show that transcription of the p53 gene is induced by IFN-a/b, accompanied by an increase in p53 protein level. IFN-a/b signalling itself does not activate p53; rather, it contributes to boosting p53 responses to stress signals. We show examples in which p53 gene induction by IFN-a/b contributes to tumour suppression. Furthermore, we show that p53 is activated in virally infected cells to evoke an apoptotic response and that p53 is critical for antiviral defence of the host. Our study reveals a hitherto unrecognized link between p53 and IFN-a/b in tumour suppression and antiviral immunity, which may have therapeutic implications.The tumour suppressor p53, activated in response to DNA damage, induces cell cycle arrest or apoptosis through transcriptional activation of its target genes, hence having a central role in tumour suppression [1][2][3][4][5] . So far, it is not known whether p53 contributes to the immune responses that lead to the eradication of pathogens such as viruses. On the other hand, IFN-a/b, both of which are essential cytokines for antiviral immunity, are sometimes referred to as 'negative growth factors' , and manifest anti-oncogenic activities [6][7][8][9][10] . In fact, IFN-a/b are used for the treatment of some forms of human cancer but the molecular basis for the treatment is poorly understood [11][12][13] . Until know, little if anything has been known about the link between the p53 and IFN-a/b system. Induction of p53 protein by IFN-a/bWhen wild-type mouse embryonic fibroblasts (MEFs) were stimulated with IFN-b, a notable increase in the level of p53 was observed (Fig. 1a). A similar observation was made in cells stimulated with IFN-a (data not shown) but not with IFN-g ( Supplementary Fig. 1). The increase in p53 level with IFN-b treatment was dose-dependent, with about fourfold induction achieved at a high concentration of IFN-b (Fig. 1b). The p53 induction by IFN-b was also observed in two human hepatic cancer cell lines, HepG2 and HLE, p53 function being abrogated in the latter cells by a mutation in the DNA-binding domain 14 (Fig. 1c). We performed a pulse-chase experiment to examine whether the observed p53 protein induction is secondary to suppression of the p53 degradation pathway by IFN-b, typically the MDM2-mediated pathway [15][16][17] . However, no difference was observed in the half-life of p53 (40-45 min) between the IFN-treated and untreated MEFs (Fig. 1d), suggesting that p53 protein synthesis is induced by IFN-b stimulation. Induction of the p53 gene by IFN-a/bInformation is limited about the induction of the p53 gene 18 , and the above results prompted us to examine whether IFN-a/b induces p53 gene transcription. Inspection of mouse and human p53...

Macrophages play pivotal roles in both the induction and resolution phases of inflammatory processes. Macrophages have been shown to synthesize anti-inflammatory fatty acids in an LXR-dependent manner, but whether the production of these species contributes to the resolution phase of inflammatory responses has not been established. Here, we identify a biphasic program of gene expression that drives production of anti-inflammatory fatty acids 12–24h following TLR4 activation and contributes to down-regulation of mRNAs encoding pro-inflammatory mediators. Unexpectedly, rather than requiring LXRs, this late program of anti-inflammatory fatty acid biosynthesis is dependent on SREBP1 and results in the uncoupling of NFκB binding from gene activation. In contrast to previously identified roles of SREBP1 in promoting production of IL1β during the induction phase of inflammation, these studies provide evidence that SREBP1 also contributes to the resolution phase of TLR4-induced gene activation by reprogramming macrophage lipid metabolism.

Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxic activity of many environmental xenobiotics. However, its role in innate immune responses during viral infection is not fully understood. Here we demonstrate that constitutive AHR signaling negatively regulates the type I interferon (IFN-I) response during infection with various types of virus. Virus-induced IFN-β production was enhanced in AHR- IFN-I-mediated innate response and, further, suggests that the AHR-TIPARP axis is a potential therapeutic target for enhancing antiviral responses.AHR was originally discovered as a xenobiotic sensor that mediates the toxicity of the persistent environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), more commonly known as dioxin [1][2][3][4] . Activation of AHR induces its target genes, including those encoding cytochrome P4501A1, cytochrome P4501B1, AHR repressor, TCDD-inducible poly(ADP-ribose)polymerase (TIPARP) and aldehyde dehydrogenase 1A3 (refs. 1,2,5-9), which are involved in the adaptive metabolism of xenobiotic compounds. This property of AHR has been implicated in host defense against bacterial infection, as certain bacterial pigmented virulence factors are AHR agonists that are subsequently metabolized by AHR-regulated drug-metabolizing enzymes 10 . Studies of AHR-deficient mice have identified important physiological roles for AHR in response to endogenous ligands in cell cycle regulation, cell differentiation and immune responses 8,[11][12][13][14] . In relation to this, several putative endogenous ligands for the AHR have also been reported, including heme metabolites, arachidonic acids or leukotrienes and tryptophan metabolites, such as 6-formylindolo(3,2-b)carbazole (FICZ) and kynurenine (Kyn) 2,8,15 .There has been increased interest in understanding the role of AHR in immunity.Several reports, most of which are based mainly on experiments with dioxin treatment, have shown that the AHR is involved in the differentiation and/or function of T cells, macrophages and dendritic cells 7,9,11,[16][17][18][19][20][21] . AHR has been implicated in the control of acute graft-versus-host disease and autoimmunity 11,12,21 . Dioxin-activated AHR also reduces the survival rate of mice infected with influenza A virus 22,23 and indirectly suppresses the proliferation and differentiation of virus-specific CD8 + T cells via its regulatory role in dendritic cells 24 . FICZ and dioxin diminish CD8 + T cell responsiveness, whereas dioxin, but not FICZ, affects neutrophil recruitment or pulmonary inducible nitric oxide synthase (iNOS) induction in response to influenza virus infection 25 .Tryptophan metabolites such as Kyn are upregulated during inflammation and/or tumor progression in several types of immune and tumor cells through the catalytic activity of tryptophan dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO), which catalyze the first step in the formation of Kyn from tryptophan 2,9 . This increase in Kyn leads to an increase in regulatory T c...

The receptor tyrosine kinase Ror2 regulates cell migration by acting as a receptor or co-receptor for Wnt5a. Although Wnt5a has been implicated in the invasiveness of several types of tumors, the role of Ror2 in tumor invasion remains elusive. Here we show that osteosarcoma cell lines SaOS-2 and U2OS show invasive properties in vitro by activating Wnt5a/Ror2 signaling in a cell-autonomous manner. The suppressed expression of either Wnt5a or Ror2 in osteosarcoma cells inhibits cell invasiveness accompanying decreased invadopodia formation. Gene-expression profiling identified matrix metalloproteinase 13 (MMP-13) as one of the genes whose expression is downregulated in SaOS-2 cells following suppression of Ror2 expression. Reduced expression or activity of MMP-13 suppresses invasiveness of SaOS-2 cells. Moreover, expression of MMP-13 and cell invasiveness by Wnt5a/Ror2 signaling can be abrogated by an inhibitor of the Src-family protein tyrosine kinases (SFKs), suggesting the role of the SFKs in MMP-13 expression through Wnt5a/Ror2 signaling. We further show that activation of an SFK is inhibited by the suppressed expression of Ror2. Collectively, these results indicate that Wnt5a/Ror2 signaling involves the activation of a SFK, leading to MMP-13 expression, and that constitutively active Wnt5a/Ror2 signaling confers invasive properties on osteosarcoma cells in a cell-autonomous manner.