Mannose receptor (ManR)-mediated liver sinusoidal endothelial cell (LSEC) endocytosis plays a role in antigen presentation and innate immunity, but its role in hepatic metastasis is unknown. We studied ManR-mediated endocytosis during C26 colorectal cancer cell interaction with LSECs and its implications in metastasis. Uptake of labeled ManR ligands (mannan and ovalbumin) and immunohistochemistry were used to study ManR endocytosis and expression. Several interleukin (IL)-1 inhibitors and the cyclooxygenase-2 (COX-2) inhibitor celecoxib were used to analyze the role of IL-1 and COX-2 in ManR regulation. Anti-mouse ManR antibodies and ManR knockout (ManR 2/2 ) mice were used to identify ManR-dependent mechanisms during antitumor immune response of liver sinusoidal lymphocytes (LSLs) interacting with tumor-activated LSECs. ManR expression and endocytosis increased in tumor-activated LSECs through a two-step mechanism:(1) Release of COX-2-dependent IL-1-stimulating factors by lymphocyte function-associated antigen-1-expressing C26 cells in response to intercellular adhesion molecule-1 (ICAM-1), which was expressed and secreted by tumor-activated LSECs; and (2) widespread up-regulation of ManR in LSECs through tumor-induced IL-1. In addition, LSLs that had interacted with tumoractivated LSECs in vivo decreased their antitumor cytotoxicity and interferon (IFN)-gamma secretion while they increased IL-10 release ex vivo. IFN-gamma/IL-10 ratio also decreased in the hepatic blood from tumor-injected mice. Immunosuppressant effects of tumor-activated LSECs on LSLs were abrogated in both LSECs from ManR 2/2 mice and tumor-activated LSECs given antimouse ManR antibodies. Conclusion: ICAM-1-induced tumor COX-2 decreased antitumor activity during hepatic metastasis through IL-1-induced ManR. ManR constituted a common mediator for prometastatic effects of IL-1, COX-2, and ICAM-1. A rise in hepatic IFN-gamma/IL-10 ratio and antitumor cytotoxicity by way of ManR blockade is consistent with the antimetastatic effects of IL-1, COX-2, and ICAM-1 inhibitors. These data support ManR and ManR-stimulating factors as targets for hepatic colorectal metastasis therapy. (HEPATOLOGY 2010;51:2172-2182 Abbreviations: ASMA, alpha-smooth muscle actin; CM, cell-conditioned medium; COX-2, cyclooxygenase-2; CSPG, chondroitin sulfate proteoglycan; ELISA, enzyme-linked immunosorbent assay; FITC-OVA, fluorescein isothiocyanate-labeled ovalbumin; FSA, formaldehyde treated serum albumin; ICAM-1, intercellular adhesion molecule-1; ICE, IL-1-converting enzyme; IgG2a, immunoglobulin G2a; IL, interleukin; IL-1RI, IL-1 receptor type I; IL-1Ra, IL-1 receptor antagonist; LFA-1, lymphocyte function-associated antigen 1; LSEC, liver sinusoidal endothelial cell; LSL, liver sinusoidal lymphocyte; ManR, mannose receptor; ManR À/À , ManR knockout; SD, standard deviation; sICAM-1, soluble ICAM-1.From the

BackgroundCell surface sialylation is emerging as an important feature of cancer cell metastasis. Sialyltransferase expression has been reported to be altered in tumours and may account for the formation of sialylated tumour antigens. We have focused on the influence of alpha-2,3-sialyltransferase ST3Gal III in key steps of the pancreatic tumorigenic process.Methodology/Principal FindingsST3Gal III overexpressing pancreatic adenocarcinoma cell lines Capan-1 and MDAPanc-28 were generated. They showed an increase of the tumour associated antigen sialyl-Lewisx. The transfectants' E-selectin binding capacity was proportional to cell surface sialyl-Lewisx levels. Cellular migration positively correlated with ST3Gal III and sialyl-Lewisx levels. Moreover, intrasplenic injection of the ST3Gal III transfected cells into athymic nude mice showed a decrease in survival and higher metastasis formation when compared to the mock cells.ConclusionIn summary, the overexpression of ST3Gal III in these pancreatic adenocarcinoma cell lines underlines the role of this enzyme and its product in key steps of tumour progression such as adhesion, migration and metastasis formation.

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RNA-binding proteins (RBPs) play a major role in control of mRNA turnover and translation rates. We examined the role of the RBP human antigen R (HuR) during cholestatic liver injury and hepatic stellate cells (HSC) activation. HuR silencing attenuated fibrosis development in vivo after BDL, reducing liver damage, oxidative stress, inflammation, and collagen and α-SMA (α-smooth muscle actin) expression. HuR expression increased in activated HSC from BDL mice and during HSC activation in vitro, and HuR silencing markedly reduced HSC activation. HuR regulated platelet-derived growth factor (PDGF)-induced proliferation and migration, and controlled expression of several mRNAs involved in these processes (Actin, MMP9, Cyclin D1 and B1). These functions of HuR were linked to its abundance and cytoplasmic localisation, controlled by PDGF, via ERK and PI3K activation, and ERK-LKB1 activation respectively. More importantly, we identified the tumor suppressor LKB1 as a novel downstream target of PDGF-induced ERK activation in HSC. HuR also controlled transforming growth factor beta (TGF-β-induced profibrogenic actions by regulating expression of TGF-β, α-SMA, and p21. This was likely due to an increased cytoplasmic localisation of HuR, controlled by TGF-β-induced p38 MAPK activation. Finally, we found that HuR and LKB1 (Ser428) levels were highly expressed in activated HSC in human cirrhotic samples. Conclusion: Our results show that HuR is important for pathogenesis of liver fibrosis development in the cholestatic injury model, for HSC activation, and for the response of activated HSC to PDGF and TGF-β.

Abstract. Intercellular adhesion molecule (ICAM)-1, is a transmembrane glycoprotein of the immunoglobulin (Ig)-like superfamily, consisting of five extracellular Ig-like domains, a transmembrane domain and a short cytoplasmic tail. ICAM-1 is expressed in various cell types, including endothelial cells and leukocytes, and is involved in several physiological processes. Furthermore, it has additionally been reported to be expressed in various cancer cells, including melanoma, colorectal cancer and lymphoma. The majority of studies to date have focused on the expression of the ICAM-1 on the surface of tumor cells, without research into ICAM-1 expression at sites of metastasis. Cancer cells frequently metastasize to the liver, due to its unique physiology and specialized liver sinusoid capillary network. Liver sinusoidal endothelial cells constitutively express ICAM-1, which is upregulated under inflammatory conditions. Furthermore, liver ICAM-1 may be important during the development of liver metastasis. Therefore, it is necessary to improve the understanding of the mechanisms mediated by this adhesion molecule in order to develop host-directed anticancer therapies.