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The development of gastric cancer is closely associated with Helicobacter pylori ( H. pylori) infection. The expression of cylooxigenase-2 (COX-2), a rate-limiting enzyme for prostaglandin biosynthesis, is induced in H. pylori-associated chronic gastritis, which thus results in the induction of proinflammatory prostaglandin, PGE2. The COX-2/PGE2 pathway plays a key role in gastric tumorigenesis. On the other hand, several oncogenic pathways have been shown to trigger gastric tumorigenesis. The activation of Wnt/β-catenin signaling is found in 30–50% of gastric cancers, thus suggesting that Wnt signaling plays a causal role in gastric cancer development. Mutations in the bone morphogenetic protein (BMP) signaling pathway are responsible for the subset of juvenile polyposis syndrome (JPS) that develops hamartomas in the gastrointestinal tract. BMP suppression appears to contribute to gastric cancer development because gastric cancer risk is increased in JPS. Wnt signaling is important for the maintenance of gastrointestinal stem cells, while BMP promotes epithelial cell differentiation. Accordingly, it is possible that both Wnt activation and BMP suppression can cause gastric tumorigenesis through enhancement of the undifferentiated status of epithelial cells. Recent mouse model studies have indicated that induction of the PGE2 pathway is required for the development of both gastric adenocarcinoma and hamartoma in the Wnt-activated and BMP-suppressed gastric mucosa, respectively. This article reviews the involvement of the PGE2, Wnt, and BMP pathways in the development of gastric cancer, and gastric phenotypes that are found in transgenic mouse models of PGE2 induction, Wnt activation, BMP suppression, or a combination of these pathways. ( Cancer Sci 2009; 100: 1779–1785) [ABSTRACT FROM AUTHOR]

Background & Aims: Helicobacter pylori infection induces an inflammatory response, which can contribute to gastric tumorigenesis. Induction of cyclooxygenase-2 (COX-2) results in production of prostaglandin E2 (PGE2), which mediates inflammation. We investigated the roles of bacterial infection and PGE2 signaling in gastric tumorigenesis in mice. Methods: We generated a germfree (GF) colony of K19-Wnt1/C2mE mice (Gan mice); these mice develop gastric cancer. We examined tumor phenotypes, expression of cytokines and chemokines, and recruitment of macrophages. We also investigated PGE2 signaling through the PGE2 receptor subtype 4 (EP4) in Gan mice given specific inhibitors. Results: Gan mice raised in a specific pathogen-free facility developed large gastric tumors, whereas gastric tumorigenesis was significantly suppressed in GF-Gan mice; reconstitution of commensal flora or infection with Helicobacter felis induced gastric tumor development in these mice. Macrophage infiltration was significantly suppressed in the stomachs of GF-Gan mice. Gan mice given an EP4 inhibitor had decreased expression of cytokines and chemokines. PGE2 signaling and bacterial infection or stimulation with lipopolysaccharide induced expression of the chemokine C-C motif ligand 2 (CCL2) (which attracts macrophage) in tumor stromal cells or cultured macrophages, respectively. CCL2 inhibition suppressed macrophage infiltration in tumors, and depletion of macrophages from the tumors of Gan mice led to signs of tumor regression. Wnt signaling was suppressed in the tumors of GF-Gan and Gan mice given injections of tumor necrosis factor-α neutralizing antibody. Conclusions: Bacterial infection and PGE2 signaling are required for gastric tumorigenesis in mice; they cooperate to up-regulate CCL2, which recruits macrophage to gastric tumors. Macrophage-derived tumor necrosis factor-α promotes Wnt signaling in epithelial cells, which contributes to gastric tumorigenesis. [Copyright &y& Elsevier]

Equine cells are required for isolation of viruses that infect the horse. However, only a few equine cell lines and cell cultures are available so far. Fetal horse kidney (FHK)-Tcl3.1 cell is a novel cell line established by introducing simian virus 40 (SV40) large T antigen. In the present study, the ability to propagate equine viruses was compared between FHK-Tcl3.1 cells and other equine cells. FHK-Tcl3.1 cells efficiently increased many viruses derived from or having pathogenicity to horses and produced high infective titers in culture fluids. These results indicate that FHK-Tcl3.1 cells would be useful for propagation and serological tests of viruses that affect Equidae.

The activation of Wnt/beta-catenin signalling has an important function in gastrointestinal tumorigenesis. It has been suggested that the promotion of Wnt/beta-catenin activity beyond the threshold is important for carcinogenesis. We herein investigated the role of macrophages in the promotion of Wnt/beta-catenin activity in gastric tumorigenesis. We found beta-catenin nuclear accumulation in macrophage-infiltrated dysplastic mucosa of the K19-Wnt1 mouse stomach. Moreover, macrophage depletion in Apc(Delta716) mice resulted in the suppression of intestinal tumorigenesis. These results suggested the role of macrophages in the activation of Wnt/beta-catenin signalling, which thus leads to tumour development. Importantly, the conditioned medium of activated macrophages promoted Wnt/beta-catenin signalling in gastric cancer cells, which was suppressed by the inhibition of tumour necrosis factor (TNF)-alpha. Furthermore, treatment with TNF-alpha induced glycogen synthase kinase 3beta (GSK3beta) phosphorylation, which resulted in the stabilization of beta-catenin. We also found that Helicobacter infection in the K19-Wnt1 mouse stomach caused mucosal macrophage infiltration and nuclear beta-catenin accumulation. These results suggest that macrophage-derived TNF-alpha promotes Wnt/beta-catenin signalling through inhibition of GSK3beta, which may contribute to tumour development in the gastric mucosa.

Neutrophils (polymorphonuclear leukocytes: PMNs) are essential for the host defense against various infections and are often injurious to the host, causing inflammatory diseases where tumor necrosis factor-alpha (TNF-alpha) is suggested to play an important role. Since an effect of TNF-alpha on canine PMN apoptosis has not been studied, canine PMNs were stimulated with recombinant human (rh)TNF-alpha in the present study to investigate the effect of TNF-alpha on canine PMN apoptosis. PMN apoptosis and function to produce ROS were assessed by flow cytometry. Delayed apoptosis was observed in the PMNs treated with rhTNF-alpha at 100 ng/ml, accompanied by retention of capability to produce ROS. However, PMN apoptosis was accelerated by rhTNF-alpha combined with cycloheximide. Therefore, it is indicated that TNF-alpha is able to activate anti- and pro-apoptotic pathways in PMNs and that the inhibition of PMN apoptosis by TNF-alpha requires protein synthesis in the PMNs.

The canine Mcl-1 gene was cloned and sequenced. Canine Mcl-1 clone was 2694 base pairs in length and encoded 350 amino acids. The predicted amino acid sequence was 87.7%, 77.1% and 75.7% homologous to predicted human, mouse and rat Mcl-1, respectively. RT-PCR analysis revealed that canine Mcl-1 mRNA was expressed in PBMCs (peripheral blood mononuclear cells), bone marrow cells, MDCK (Madin-Darby canine kidney) and GL-1 (canine B cell leukemia) whereas undetectable in CL-1 (canine T cell lymphoma) cell line.