IL-22 is produced by activated T cells and signals through a receptor complex consisting of IL-22R1 and IL-10R2. The aim of this study was to analyze IL-22 receptor expression, signal transduction, and specific biological functions of this cytokine system in intestinal epithelial cells (IEC). Expression studies were performed by RT-PCR. Signal transduction was analyzed by Western blot experiments, cell proliferation by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay and Fas-induced apoptosis by flow cytometry. IEC migration was studied in wounding assays. The IEC lines Caco-2, DLD-1, SW480, HCT116, and HT-29 express both IL-22 receptor subunits IL-22R1 and IL-10R2. Stimulation with TNF-alpha, IL-1beta, and LPS significantly upregulated IL-22R1 without affecting IL-10R2 mRNA expression. IL-22 binding to its receptor complex activates STAT1/3, Akt, ERK1/2, and SAPK/JNK MAP kinases. IL-22 significantly increased cell proliferation (P = 0.002) and phosphatidylinsitol 3-kinase-dependent IEC cell migration (P < 0.00001) as well as mRNA expression of TNF-alpha, IL-8, and human beta-defensin-2. IL-22 had no effect on Fas-induced apoptosis. IL-22 mRNA expression was increased in inflamed colonic lesions of patients with Crohn's disease and correlated highly with the IL-8 expression in these lesions (r = 0.840). Moreover, IL-22 expression was increased in murine dextran sulfate sodium-induced colitis. IEC express functional receptors for IL-22, which increases the expression of proinflammatory cytokines and promotes the innate immune response by increased defensin expression. Moreover, our data indicate intestinal barrier functions for this cytokine-promoting IEC migration, which suggests an important function in intestinal inflammation and wound healing. IL-22 is increased in active Crohn's disease and promotes proinflammatory gene expression and IEC migration.

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The mechanisms of immune evasion and the role of the early immune response in chronic infection caused by hepatitis C virus (HCV) are still unclear. Here, we present evidence for a cascade of molecular events that the virus initiates to subvert the innate immune attack. The HCV core protein induced p53-dependent gene expression of TAP1 (transporter associated with antigen processing 1) and consecutive major histocompatibility complex (MHC) class I upregulation. Moreover, in p53-deficient liver cell lines, only reconstitution with wild-type p53, but not mutated p53 lacking DNA binding capacity, showed this effect. As a consequence of increased MHC class I expression, a significantly downregulated cytotoxic activity of natural killer (NK) cells against HCV core-transfected liver cells was observed, whereas lysis by HCV-specific cytotoxic T cells was not affected. These results demonstrate a way in which HCV avoids recognition by NK cells that may contribute to the establishment of a chronic infection.Hepatitis C virus (HCV) acts as a major causative agent of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. To date, HCV infection is one of the primary causes of liver transplantation in the United States and other countries. More than 170 million individuals have been reported to be seropositive worldwide (40). There is no sufficient prophylaxis by vaccination, and antiviral therapy with a combination of alpha interferon (IFN-␣) and ribavirin is effective only in selected patients. This underlines an urgent need to improve our knowledge of virus-cell interactions and immune escape mechanisms. Elucidation of the mechanisms by which HCV interacts with and regulates the immune response, especially in the early stages of infection, is likely to lead to productive insights into how to combat chronic infection and prevent its serious complications.HCV has been classified as the sole member of a distinct genus called Hepacivirus in the family Flaviviridae. The characteristic all of these viruses have in common is a positivestranded RNA that, in the case of HCV, consists of a genome of approximately 10 kb containing one large open reading frame (ORF) that is initially translated into one single polyprotein and subsequently cleaved into the functional proteins. The putative organization of the HCV genome includes the 5Ј-untranslated region, four structural proteins, six nonstructural proteins, and a 3Ј-untranslated region (41). Among the structural proteins of HCV, the basic 19-kDa core protein exhibits pleiotropic features. It may be involved in nucleocapsid formation, and it plays a role in the switch between viral polyprotein synthesis and subsequent viral RNA replication. In addition, HCV core protein was shown to transcriptionally regulate several cellular and viral genes (28). Furthermore, severalalthough in part contradictory-reports suggest an influence of the HCV core protein on the transcriptional activity of p53 and the regulation of p53-dependent genes. Both suppression and upregulation of p53-dependen...

The CD95 (also called APO-1 or Fas) system plays a major role in the induction of apoptosis in lymphoid and nonlymphoid tissues in response to a variety of extracellular signals, including chemotherapeutic drugs. Here we report that the CD95 ligand (CD95L) is upregulated in hepatoma cells upon treatment with antineoplastic drugs. Upregulation by different chemotherapeutic drugs is functionally relevant for drug-induced apoptosis and is mediated by transcriptional mechanisms. The MEKK1/JNKK pathway and a novel AP-1 element in the CD95L promoter downstream of the TATA box are required for CD95L upregulation. Thus, understanding the mechanisms of CD95-mediated apoptosis through CD95L upregulation upon treatment of hepatocellular carcinomas with chemotherapeutic drugs may contribute to the improvement of anticancer chemotherapy.

Neoplastic progression in human tissues appears to be paralleled by a series of genetic and epigenetic alterations. In human colorectal cancers, defect Wnt/␤-catenin/T-cell factor and RAS/RAF signaling pathways have a major contributing role in tumor initiation and progression. To date, much of the research on the consequences of ␤-catenin activation has been focused on genes whose expression is believed to be activated by ␤-catenin-associated T-cell factor-dependent transcription. Little is known about genes whose expression may be down-regulated secondary to ␤-catenin activation. Using a subtractive suppression hybridization approach, we identified a gene with markedly decreased expression in rat RK3E epithelial cells neoplastically transformed by ␤-catenin. Because expression of this gene was also down-regulated in RK3E transformed by several other oncogenes, the gene was named DRO1 for "down-regulated by oncogenes 1." Compared with corresponding normal tissues, DRO1 expression was found to be very reduced in colon and pancreatic cancer cell lines as well as in most colorectal cancer specimens. The predicted DRO1 protein contains three repetitive elements with significant similarity to the carboxyl-terminal regions of the predicted proteins from DRS/SRPX/ ETX1 and SRPUL genes, suggesting the existence of a new protein family. Ectopic expression of DRO1 in neoplastically transformed RK3E or colorectal and pancreatic cancer cell lines lacking endogenous DRO1 expression resulted in substantial inhibition of growth properties. DRO1 was found to suppress anchorage independent growth and to sensitize cells to anoikis and CD95-induced apoptosis. Our findings suggest that inhibition of DRO1 expression may be an important event in the development of colorectal and pancreatic cancers.

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Loss of susceptibility to apoptosis signals is a crucial step in carcinogenesis. Therefore, sensitization of tumor cells to apoptosis is a promising therapeutic strategy. c-Jun-Nterminal-kinases (JNK) have been implicated in stressinduced apoptosis, but may also contribute to survival signaling. Here we show that CD95-induced apoptosis is augmented by the JNK inhibitor SP600125 and small interfering RNA directed against JNK1/2. SP600125 potently inhibited methyl methane sulfonate-induced phosphorylation of c-Jun, but had minimal effect on apoptosis alone. In contrast, it strongly enhanced CD95-mediated apoptosis in six of eight tumor cell lines and led to a G 2 /M phase arrest in all cell lines. SP600125 enhanced cleavage of caspase 3 and caspase 8, the most upstream caspase in the CD95 pathway. JNK inhibition up-regulates p53 and its target genes p21Cip1/Waf1 and CD95. However, although HCT116 p53 À/À cells and p21 +/+ cells were less sensitive to CD95 stimulation than their p53 +/+ and p21 À/À counterparts, p53and p21 were not involved in the JNK-mediated effect. JunD, which was described to be protective in tumor necrosis factor-induced apoptosis, was not regulated by JNK inhibition on the protein level. When transcription was blocked by actinomycin D, JNK inhibition still enhanced apoptosis to a comparable extent. We conclude that JNK inhibition has antitumor activity by inducing growth arrest and enhancing CD95-mediated apoptosis by a transcription-independent mechanism. (Cancer Res 2005; 65(15): 6780-8)

Suramin is a polysulfonated derivative of urea and has been widely used both to treat infections and as a chemotherapeutic drug. Suramin has been shown to inhibit growth factor signaling pathways; however, its effect on apoptosis is unknown. Here we show that suramin inhibits apoptosis induced through death receptors in hepatoma and lymphoma cells. It also inhibits the proapoptotic effect of chemotherapeutic drugs. The antiapoptotic mechanism is specific to cell type and is caused by reduced activation, but not altered composition, of the death-inducing signaling complex (DISC), and by inhibition of the initiator caspases 8, 9 and 10. Suramin also shows similar effects in in vivo models: apoptotic liver damage induced by CD95 stimulation and endotoxic shock mediated by tumor-necrosis factor (TNF) are inhibited in mice, but necrotic liver damage is not inhibited in a rat model of liver transplantation. Thus, the antiapoptotic property of suramin in the liver may be therapeutically exploited.