A broad range of experimental and clinical evidence has highlighted the central role of chronic infl ammation in promoting tumor development. However, the molecular mechanisms converting a transient infl ammatory tissue reaction into a tumor-promoting microenvironment remain largely elusive. We show that mice defi cient for the receptor for advanced glycation end-products (RAGE) are resistant to DMBA/TPA-induced skin carcinogenesis and exhibit a severe defect in sustaining infl ammation during the promotion phase. Accordingly, RAGE is required for TPA-induced up-regulation of proinfl ammatory mediators, maintenance of immune cell infi ltration, and epidermal hyperplasia. RAGE-dependent up-regulation of its potential ligands S100a8 and S100a9 supports the existence of an S100/RAGE-driven feed-forward loop in chronic infl ammation and tumor promotion. Finally, bone marrow chimera experiments revealed that RAGE expression on immune cells, but not keratinocytes or endothelial cells, is essential for TPA-induced dermal infi ltration and epidermal hyperplasia. We show that RAGE signaling drives the strength and maintenance of an infl ammatory reaction during tumor promotion and provide direct genetic evidence for a novel role for RAGE in linking chronic infl ammation and cancer.

The receptor for advanced glycation end products (RAGE) is a single transmembrane receptor of the immunoglobulin superfamily that is mainly expressed on immune cells, neurons, activated endothelial and vascular smooth muscle cells, bone forming cells, and a variety of cancer cells. RAGE is a multifunctional receptor that binds a broad repertoire of ligands and mediates responses to cell damage and stress conditions. It activates programs responsible for acute and chronic inflammation, and is implicated in a number of pathological diseases, including diabetic complications, stroke, atheriosclerosis, arthritis, and neurodegenerative disorders. The availability of Rage knockout mice has not only advanced our knowledge on signalling pathways within these pathophysiological conditions, but also on the functional importance of the receptor in processes of cancer. Here, we will summarize molecular mechanisms through which RAGE signalling contributes to the establishment of a pro-tumourigenic microenvironment. Moreover, we will review recent findings that provide genetic evidence for an important role of RAGE in bridging inflammation and cancer.

The nuclear factor-kappaB (NF-B) signaling pathway has been recently shown to participate in inflammation-induced cancer progression. Here, we describe a detailed analysis of the NF-B-dependent gene regulatory network in the well-established Mdr2 knockout mouse model of inflammation-associated liver carcinogenesis. Expression profiling of NF-B-deficient and NF-B-proficient hepatocellular carcinoma (HCC) revealed a comprehensive list of known and novel putative NF-B target genes, including S100a8 and S100a9. We detected increased co-expression of S100A8 and S100A9 proteins in mouse HCC cells, in human HCC tissue, and in the HCC cell line Hep3B on ectopic RelA expression. Finally, we found a synergistic function for S100A8 and S100A9 in Hep3B cells resulting in a significant induction of reactive oxygen species (ROS), accompanied by enhanced cell survival. Conclusion: We identified S100A8 and S100A9 as novel NF-B target genes in HCC cells during inflammation-associated liver carcinogenesis and provide experimental evidence that increased co-expression of both proteins supports malignant progression by activation of ROS-dependent signaling pathways and protection from cell death. (HEPATOLOGY 2009;50: 1251-1262.)H epatocellular carcinoma (HCC) is the most frequent type of liver cancer and one of the most prevalent causes of cancer mortality worldwide. These tumors arise at sites of chronic liver injury, inflammation, and hepatocyte proliferation provoked by several causes such as chronic hepatitis B and C viral infection, chronic alcohol consumption, and aflatoxin B1-contaminated food. 1,2 Despite remarkable improvements in diagnosis, only limited therapeutic options exist, most of them with minimal clinical benefit. 2 Moreover, there is

Objective. To define the phenotype and function of CD4؉,CD25؉ regulatory T cells (Treg) in patients with cutaneous lupus erythematosus (CLE), a heterogeneous autoimmune disease characterized primarily by inflammatory skin lesions.Methods. The number of Treg in skin specimens obtained from patients with various subtypes of CLE was investigated by immunohistochemical analysis, using anti-Foxp3 and anti-CD4 monoclonal antibodies. Furthermore, characterization of peripheral blood CD4؉,CD25؉ Treg from normal healthy donors and patients with CLE was carried out by flow cytometry, analyzing the expression of Foxp3 and Treg subpopulations. We also purified CD4؉,CD25 high Treg obtained from patients with CLE and tested the sensitivity of these cells to CD95L-mediated apoptosis.Results. Quantitative analysis of CD4؉ T cells in skin lesions from patients with CLE revealed that the number was similar to that in lesions from patients with other chronic inflammatory diseases, but the number of Foxp3؉ Treg in CLE was significantly reduced. There was no correlation between disease subtype and the frequency of Foxp3؉ Treg in the skin of patients with CLE. In peripheral blood, no significant differences were observed in the number and phenotype of CD4؉,CD25؉ Treg or in the sensitivity to apoptosis of CD4؉,CD25 high Treg derived from patients with CLE and those derived from normal healthy donors.Conclusion. These data suggest that an organspecific abnormality of Treg in the skin underscores the importance of analyzing Treg in the affected tissue. Such a local process might give insight into the pathogenic mechanisms of CLE and differs from a global peripheral dysfunction as reported for patients with a systemic manifestation of the disease.

Expression and function of the oncogenic transcription factor activator protein (AP-

Two related models for T cell signalling initiation suggest either that T cell receptor (TCR) engagement leads to its recruitment to ordered membrane domains, often referred to as lipid rafts, where signalling molecules are enriched or that ordered TCR-containing membrane nanodomains coalesce upon TCR engagement. That ordered domains form upon TCR engagement, as they do upon lipid raft marker patching, has not been considered. The target of this study was to differentiate between those three options. Plasma membrane order was followed in live T cells at 37 °C using laurdan to report on lipid packing. Patching of the TCR that elicits a signalling response resulted in aggregation, not formation, of ordered plasma membrane domains in both Jurkat and primary T cells. The TCR colocalised with actin filaments at the plasma membrane in unstimulated Jurkat T cells, consistent with it being localised to ordered membrane domains. The colocalisation was most prominent in cells in G1 phase when the cells are ready to commit to proliferation. At other cell cycle phases the TCR was mainly found at perinuclear membranes. Our study suggests that the TCR resides in ordered plasma membrane domains that are linked to actin filaments and aggregate upon TCR engagement.

The receptor for advanced glycation end products (RAGE) is a pattern recognition receptor causally related to the pathogenesis of acute and chronic inflammation. In a mouse model of inflammation-driven skin carcinogenesis, RAGE deletion conferred protection from the development of skin tumors due to a severely impaired cutaneous inflammation. Although the impact of RAGE expression in immune cells was shown to be essential for the maintenance of a cutaneous inflammatory reaction, the role of RAGE in keratinocytes remained unsolved. Using mice harboring a keratinocyte-specific deletion of RAGE, we analyzed its role in the regulation of an acute inflammatory response that was induced by topical treatment of the back skin with the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). We show that RAGE expression in cutaneous keratinocytes modulates the strength and kinetics of acute inflammation and supports the maintenance of epidermal keratinocyte activation. To address the underlying molecular mechanism, we isolated interfollicular epidermis by laser microdissection for gene expression analysis, and identified RAGE as a regulator in the temporal control of TPA-induced epidermal tumor necrosis factor alpha transcript levels. In summary, our data demonstrate that RAGE expression in keratinocytes is critically involved in the perpetuation of acute inflammation and support the central role of RAGE in paracrine communication between keratinocytes and stromal immune cells.

BackgroundIn the past, molecular mechanisms that drive the initiation of an inflammatory response have been studied intensively. However, corresponding mechanisms that sustain the expression of inflammatory response genes and hence contribute to the establishment of chronic disorders remain poorly understood. Recently, we provided genetic evidence that signaling via the receptor for advanced glycation end products (Rage) drives the strength and maintenance of an inflammatory reaction. In order to decipher the mode of Rage function on gene transcription levels during inflammation, we applied global gene expression profiling on time-resolved samples of mouse back skin, which had been treated with the phorbol ester TPA, a potent inducer of skin inflammation.ResultsRanking of TPA-regulated genes according to their time average mean and peak expression and superimposition of data sets from wild-type (wt) and Rage-deficient mice revealed that Rage signaling is not essential for initial changes in TPA-induced transcription, but absolutely required for sustained alterations in transcript levels. Next, we used a data set of differentially expressed genes between TPA-treated wt and Rage-deficient skin and performed computational analysis of their proximal promoter regions. We found a highly significant enrichment for several transcription factor binding sites (TFBS) leading to the prediction that corresponding transcription factors, such as Sp1, Tcfap2, E2f, Myc and Egr, are regulated by Rage signaling. Accordingly, we could confirm aberrant expression and regulation of members of the E2f protein family in epidermal keratinocytes of Rage-deficient mice.ConclusionsIn summary, our data support the model that engagement of Rage converts a transient cellular stimulation into sustained cellular dysfunction and highlight a novel role of the Rb-E2f pathway in Rage-dependent inflammation during pathological conditions.